Specification For Rcc Construction 4845b

Construction specification for hydraulic roller compacted concrete

Issued on Nov. 03, 2000 Implement from Jan. 1, 2001 Issued by State Economic and Trade Commission of the People's Republic of China Construction specification for hydraulic roller compacted concrete

Chief Development Organization：China National Water Resources and Hydropower Engineering Corporation Approval Department: State Economic and Trade Commission of the People's Republic of China Approval Document No: State Economic and Trade Power [2000] 1048

China Electric Power Press

2000

Beijing

DL/T5112-2000 Contents Preface 1 Scope……………………………………………………………… 2 Cited standard…………………………………………………… 3 General rules…………………………………………………….. 4 Vocabulary of ………………………………………….. 5 Materials……………………………………………………….. 5.1 Cement…………………………………………………… 5.2 Flyash or other additive blend……………………….…… 5.3 Concrete ixture………………………………………… 5.4 Aggregate…………………………………………………… 5.5 Water for concrete mixing and curing…………………….. 6 Mix design………………………………………………….. 7 Construction………………………………………………… 7.1 Preparation before placing……………………………… 7.2 Mixing…………………………………………………. 7.3 Transportation…………………………………………. 7.4 Dumping and block leveling………………………….. 7.5 Rolling……..…………………………………………. 7.6 t forming………………………………………….. 7.7 Treatment of layer and t face……………………. 7.8 Casting of dissimilar concrete（异种混凝土）…….. 7.9 Casting of abnormal concrete………………………. 7.10 Curing and protecting………………………………. 7.11 Construction of embedded parts…………………… 7.12 Construction under special meteorologic condition… 8 Quality management and assessment…………………….. 8.1 Testing and controlling of raw materials………………. 8.2 Testing and controlling of newly mixed RCC…………. 8.3 On-site quality testing of RCC……………………….. 8.4 Quality control and assessment……………………….. Annex A (standard annex) Conversion factor of compression strength between specimen of different height-diameter ratio & cylinder and cubic specimen………………………………………………………. Explanation of clauses……………………………………..

1 Scope This specification mainly includes the following contents: material, mix design, construction, quality management and assessment. This specification is applicable for the RCC construction of grade I, II III hydraulic structure in large and medium-scale hydropower stations，and RCC construction in other project can refer to this.

2 Cited standards The clauses of the following standards comprise the clauses of this specification through being cited in this specification. While this specification is published, all the editions showed here are effective. The parties using this specification should discuss the possibility to use the newest editions of the following standards since all the standards may be revised. GB 175-1999 Portland cement and ordinary Portland cement GB 200-1989 Moderate-heat Portland cement and low-heat slag Portland cement GB 1344-1999 Slag Portland cement, pozzolanic Portland cement and flyash Portland cement GB 8076-1997 Concrete ixture GB/T 1596-1991 Flyash used in cement and concrete GBJ 119-1988 Application technical standard for concrete ixture DL/T 5055-1996 Technical specification of flyash mixing in hydraulic concrete DL/T 5100-1999 Technical code of hydraulic concrete additive blend

DL/T 5123-2000 Acceptance code for basic construction project of hydropower station SD 105-1982 Test code for hydraulic concrete SDJ 207-1982 Construction specification for hydraulic concrete SL 48-1994 Test code for hydraulic RCC SL 176-1996 Construction quality assessment code for water resources and hydropower project

3 General rules 3.0.1 Besides complying with this specification, the construction of Hydraulic RCC should also carry out the current relevant specifications and industry standards of the nation where this specification does not cover. 3.0.2 Field test should be carried out before RCC construction to the mix design, process flow of construction, adaptability of construction system and construction equipment, and determine the construction technology and parameters. 3.0.3 The performance of RCC should satisfy the indices such as unit weight, Physical and Mechanical properties ， impermeability and frost resistance required by design. 3.0.4 The temperature should be controlled in the RCC construction. 3.0.5 The new technique, new technology, new materials and new equipments verified and demonstrated by practice can be applied in RCC construction after ing through the technical results approval.

4 Vocabulary of 4.0.1 blend Means the active and inactive mineral substances mixed in the cement when it leaves the factory. 4.0.2 additive blend Means the mineral substances mixed into the concrete on construction site. 4.0.3 construction t The t set up according to construction requirement. 4.0.4 spreading thickness Means the concrete thickness of each working layer before being compacted. 4.0.5 compacted thickness Means the thickness of each working layer being compacted to the designed compactness or unit weight. 4.0.6 relative density Means the ratio between the real tested unit weight in construction block and the average basic unit weight acquired from the RCC indoor test. 4.0.7 basic unit weight Average value of RCC with selected mix proportion acquired from indoor test. 4.0.8 intermittent time between layers Means the period starting from adding water to the lower layer concrete mixture till finishing the compaction of upper layer concrete. 4.0.9 permissible time interval between placing layers The maximum time interval between layers for placing the upper layer RCC to satisfy the combining quality requirement between layers directly without any layer surface treatment. 4.0.10 permissible time interval between placing layers while using bending mix The maximum time interval between layers in which the combining quality requirement can be satisfied by placing RCC after spreading bending mix on the layer surface. 4.0.11 cold t The compacting layer of which the intermittent time between layers has exceeded the permissible time interval between placing layers while using bending mix. 4.0.12 abnormal concrete The vibrated and compacted concrete by mixing a certain proportion of

mortar into the spread RCC. 4.0.13 bending mix The plaster, mortar or small aggregate concrete adaptable to corresponding RCC placing on the cast layer or foundation rock surface. 5 Materials 5.1 Cement 5.1.1 The cement quality should be in conformity with the relevant regulations of the current national standards. 5.1.2 Special requirements of mineral components and alkali content can be proposed for the cement used in hydraulic RCC according to specific condition. The cement should be produced by fixed manufacturer and adopt bulk cement in priority. 5.1.3 It is better to choose Portland cement, ordinary Portland cement and moderate-heat Portland cement for the variety of the cement. The cement grade should be no lower than No.425 5.1.4 There should be factory inspection report for each batch of cement. It should be rechecked according to table 8.1.1 after being transported to the site and chemical analysis should be carried out for it if necessary. The inspection of cement quality should be executed according to the current national standards. 5.1.5 The cement should be transported and stored respectively according to different variety, grade and factory number. 5.1.6 There should be rainproof and damp-proof facilities for the place of cement transportation and storage. The cement stored for more than 3 months must be rechecked before use and be used according to the rechecked results. Caked concrete is strictly forbidden to use. 5.2 Flyash or other additive blend 5.2.1 Appropriate amount of excellent flyash or other active additive blend should be mixed into the RCC in priority, and inactive additive blend can also be mixed into after test demonstration. 5.2.2 The flyash mixed in the RCC should be in conformity with the requirement of DL/T 5055, and be checked according to table 8.1.1 after being transported to the site. 5.2.3 The mixing quantity of flyash or other additive blend in the RCC should be determined by test. 5.3 Concrete ixture 5.3.1 ixture should be mixed into the RCC, and its variety and mixing quantity should be determined by test. 5.3.2 Compound ixtures should be mixed into the RCC. Mainly select the slow-setting and water-reducing ixtures for construction in summer. Select air-entraining ixtures for the concrete with frostresistant requirement. 5.3.3 The mobilized ixtures should have product instruction book

and material certificate, and should comply with the regulations in DL/T 5100. Quality inspection must be carried out before it is used. 5.4 Aggregate 5.4.1 Quality, technical and economic demonstration should be carried out for the used coarse and fine aggregate. 5.4.2 Aggregate test should be carried out following the relevant regulations in SD 105. 5.4.3 The reserve of aggregate should be enough, and sun-shading, rainproof and dewatering facilities should be set up for the aggregate. The water content of sand should not exceed 6% while mixing. 5.4.4 Control the screening quality while flushing and screening the aggregate, make sure that all grades of produced aggregate comply with requirements, and pay attention to the loss of rock powder in the fine sand and artificial sand. 5.4.5 The artificial sand should be produced by crushing machine with high productive efficiency and can produce good-sized grain. 5.4.6 While producing aggregate with dry method, measures should be taken to prevent the aggregate grain being adhered to and wrapped by large amount of rock powder. 5.4.7 While transporting and piling the aggregate, prevent to mix with clay and mix up different graduations. 5.4.8 The sand should be hard and the gradation should be well. The modulus of fineness of artificial sand should be within 2.2-2.9, and that of natural sand should be within 2.0-3.0. The content of oversized grain should be strictly controlled. The natural sand with the modulus of fineness less than 2.0 should be demonstrated by test. 5.4.9 The content of rock powder (grain with d≦0.16mm) in artificial sand should be controlled within 10%-20%, and the best rock powder content should be determined by test. 5.4.10 The sediment percentage ((grain with d≦0.08mm) of natural sand should not be over 5%. 5.4.11 The quality index of fine aggregate (sand) and coarse aggregate should be in conformity with 5.4.8, 5.4.9 and 5.4.10, besides, other quality indices of them should be in conformity with the requirements of SDJ207. 5.5 Water for concrete mixing and curing 5.5.1 All drinking water in conformity with national standard can be used to mix and cure various concrete. 5.5.2 The substance content of the concrete mixing water should be in line with the requirements of SDJ 207. 6 Mix design 6.0.1 The mix Design of RCC should satisfy all technical indices of engineer design and requirements of construction technology. 6.0.2 Selection of parameter of mix design:

1 mixing quantity of additive blend: it should be determined by test, and special test demonstration should be done when the mix quantity has exceeded 65%. 2 water-binder ratio: should be determined according to concrete strength, tensile strain, heat insulating temperature rise and frost resistance proposed by design, and its value should be less than 0.70. 3 sand rate: the best sand rate value should be selected by test. While using the natural aggregate, the sand rate of graduation III RCC is 28%32%, and 32%-37% while it is graduation II; the sand rate should add 3%-6% while using artificial aggregate. 4 unit water consumption: can be selected according to the construction workability of RCC (VC value), variety of aggregate and maximum grain diameter, sand rate as well as ixture. 6.0.3 The designed workability (VC value) of RCC mixtures can adopt 5s-12s, the VC value at the outlet of the machine should be selected and controlled dynamically according to the variation of climate condition on construction site. And the value at the outlet of the machine should be within 5s-12s. 6.0.4 The cementing material consumption of RCC of mass permanent structure should not be less than 130kg/m3. 6.0.5 If it is required to change the variety or source of raw materials in construction, the mix proportion should be adjusted by test in advance.

7 Construction 7.1 Preparation before placing 7.1.1 Before placing the RCC, check the production and storage system of aggregate, raw materials supply, the capability of equipments of concrete making, transporting, placing, compacting and testing, work condition and construction measures combining with the on site compacting test. The construction can only be started when the requirements of relevant technical documents are satisfied. 7.1.2 Before placing the RCC, technical training should be carried out to the construction personnel. 7.1.3 Before placing in each block, there should be detailed plan for construction, and be fulfilled to specific construction operator. 7.1.4 Before placing RCC on foundation block, place mortar on the foundation rock surface first, and then place a layer of cushion concrete or abnormal concrete. Its thickness should take convenience for compaction after being leveled as principle except there is special requirement.

7.1.5 The formwork for RCC construction should be adaptable for fast and continuous construction and should satisfy the requirement to let the vibrating roller to get close. The formwork used should be designed specifically if necessary, including: vertical formwork, inclined formwork, concrete pre-cast formwork, and waterstop, formwork ing in and out of the blocks and holes. 7.2 Mixing 7.2.1 The forced mixing equipment should be selected in priority for RCC mixing, other types of mixing equipments such as free-fall. 7.2.2 The weighing system of the mixing equipment should be sensitive, accurate and reliable, and should be checked regularly to ensure that the accuracy requirement of weighing will be satisfied in the process of concrete production. 7.2.3 The mixing time, feeding order, mixing quantity of RCC should all be determined by test of concrete mixing homogeneity on site. 7.2.4 The mixing equipment should be installed quick testing device of water content of fine aggregate, and should have the automatic adjusting function of corresponding mixing water quantity. 7.2.5 The fall free from the outlet of the dump skip to the transportation tool should not exceed 5m. 7.2.6 The requirements of proportioning accuracy and mixing quality of mortar and plaster are as the same as those of mixing quality of concrete. The plaster should be mixed by machine. Collective mixing plant should be set up for large-scale project, and device to keep the plaster homogenous should be allocated. 7.3 Transportation 7.3.1 It is better to transport RCC with dumper, belt conveyor, negative pressure chute (pipe), special vertical chute. Overall examination and clearance of transportation machines should be carried out before they are being used. Cable machine ， gantry crane and tower crane etc. can be adopted while necessary. 7.3.2 The road for dumpers carrying concrete must be even; the dumper tyres must be flushed clean to prevent bringing clay and water into the block; the operations such as sudden break and sharp turn which may damage the quality of concrete layer should be avoided while running in the block. 7.3.3 While transporting concrete with belt conveyor, measures should be taken to reduce aggregate separation，plaster loss rate. And there should be sun-shading and rainproof facilities. 7.3.4 While transporting concrete with negative pressure chute (pipe), elbow heading down vertically should be made at the outlet of the negative pressure chute (pipe); the partly broken part of the cover tape of

negative pressure chute (pipe) should be repaired in time, and the cover tape should be changed timely while it has broke to a certain degree. The grade of slope and the anti-separation measures should be determined by field test. 7.3.5 The special vertical chute should have the function of antiseparation. Control device for preventing blockage can be set up if necessary. 7.3.6 while all kinds of transportation tools are running or dumping, the fall free of concrete at the outlet should not exceed 1.5m. While it exceeds, special vertical chute or transferring hopper；while continuous transporting tools and batch transporting tools are used tly, storage hopper with enough capacity should be set up at the transferring position; there should be measures to solve concrete camber while using transferring hopper; outlet of waste residue and cleaning waste water should be set up on the continuously closed transportation line form the mixing equipment to the block. 7.3.7 There should be measures to prevent slurry sediment and bleeding while transporting plaster, and ensure that the slurry transported to the site is homogeneous. The mortar can be transported by concrete transporting tools, or by special mortar transporting tools. 7.4 Dumping and block leveling 7.4.1 RCC should be placed continuously in thin layer in big block or placed intermittently, and the placing method should be level course full length placement, or inclined-layer placing method, step method. The placing size should be adaptable to the placing strength and permissible intermittent time between layers of RCC. 7.4.2 While adopting inclined-layer placing method, it should be placed from the downstream to the upstream to make the layer surface trend to the upstream, and the grade of slope should not be more steeper than 1:10, and avoid to form thin-layer sharp angle at the foot of the slope. The secondary contaminant on the construction t should be strictly cleared away before placing the mortar, and the RCC should be covered immediately after placing mortar. 7.4.3 The RCC layer should be placed belt by belt in the same direction; in the scope of 3m-5m of the upstream face, the block leveling direction should be in parallel with the dam axis. 7.4.4 While dumping concrete with dumper directly in the block, the height of concrete pile should be controlled. The separated aggregate on the side of the concrete pile should be distributed into the concrete evenly during the leveling process. 7.4.5 The unqualified concrete mixture is strictly forbidden to enter the block; the already entered should be treated. 7.4.6 While the compacted thickness is about 30cm, it can be levelly

placed once; in order to improve the separate condition or the compacted thickness is greater, it can be placed twice or three times. 7.4.7 The concrete surface should be flat and smooth after leveling, and the compacted thickness should be even. 7.5 Rolling 7.5.1 The selection of model of vibratory roller should take of rolling efficiency, exciting force, dimension of rolling drum, vibrating frequency, amplitude of vibration, walking speed, maintenance requirement and running reliability. 7.5.2 The surrounding parts of the structure should be rolled closing to the formwork by the same type of vibratory roller as the same as the inside. The part can not get close to should be compacted by small-sized vibratory roller. The permissible compacted thickness and ing number should be determined by test. 7.5.3 The walking speed of vibratory roller should be controlled within 1.0km/h-1.5km/h. 7.5.4 The compacted thickness and ing number in construction should be determined by test, and take of the factors such as comprehensive production capability of placement. Different compacting thickness can be selected according to climate, placement method etc. The compacted thickness should not less than three times of the maximum aggregate grain diameter. 7.5.5 In the scope of 3m-5m of the upstream face, the rolling direction should be vertical to the flow direction. The rolling work should adopt overlapping method. The overlapping width of rolling belt should be 10cm-20cm; and the overlapping width at the ends should be about 100cm. 7.5.6 After finishing the rolling work of each belt, lay out the testing points in mesh timely to test the compacted density of concrete. If the tested density is lower than the regulated index, retest at once, find out the reason and take treatment measures. The parts where spring soil occurs, there is no need to treat if the tested compact density meets the requirements. 7.5.7 The bedding surface or cold t that should be stopped as horizontal construction t should be rolled 1-2 times without vibration after reached the regulated ing number and compacted density. 7.5.8 While walking on the compacted concrete bedding surface, the equipments should avoid damaging the formed bedding surface. The part where is damaged should be repaired in time. 7.5.9 After entering the block, the RCC should be leveled and rolled as soon as possible. The permissible longest period from mixing to compacting finish should be determined by test or make analogy with other projects according to different season, weather conditions and variation law of RCC workability, and should not exceed 2h.

Preserve 20cm-30 cm to compact with the next belt at the same time at the brim placing belt in the compacted layer, brim of slope foot with the inclined-layer placing method, and brim of step with the step method. The final complete time for these parts should be controlled in permissible time interval between placing layers. 7.6 t forming 7.6.1 Transverse t can be formed by cutting with grooving machine, setting up induce hole or partition. The location, structure form of t and the filled materials in the t should meet the design requirements. 7.6.2 Cutting by grooving machine should adopt “cutting first, rolling later” or “rolling first, cutting later” according to the specific condition of project. 7.6.3 The setting-up of induce hole should be finished in the intermittent time between layers. Fill dry sand in the hole timely after the hole is formed. 7.6.4 The spacing length at the partition t should not be larger than 10cm, the height of partition should be 3cm-5cm lower than the compacted thickness. 7.6.5 The making and installing of transverse with re-grouting requirement should meet the design requirements. 7.7 Treatment of layer and t face 7.7.1 For the placed RCC rising continuously, the intermittent time between layers should be controlled in permissible time interval between placing layers. For the layer surface exceeding permissible time interval between placing layers, bedding mix should be placed on it first, and then placing a layer of RCC. The layer surface exceeding permissible time interval between placing layers while using bending mix is cold t. 7.7.2 Permissible time interval between placing layers and permissible time interval between placing layers while using bending mix should be determined by test according to the layer shear capacity and binding quality required by project structure, comprehensively taking of mixture property, season, weather, construction method and different areas upstream and downstream. 7.7.3 t treatment must be done to the construction t and cold t, to clean the laitance and loose aggregate on the surface of the concrete with the roughening method of brushing and flushing. After treatment and clean, and being accepted qualified, place bedding mix first, and then place a layer of concrete to continue the construction. 7.7.4 The roughening time of flushing and brushing should be determined by field test according to construction season, concrete strength, equipment performance etc. Roughening too early is prohibited. 7.7.5 The bedding mix can adopt plaster, mortar or small aggregate concrete adaptable to RCC. The water-binder ratio should as the same as RCC, the strength grade of mortar and small aggregate concrete should

enhance one grade. The bedding mix should be spread belt by belt just like the RCC. In which, the spread thickness of mortar is 1.0cm-1.5cm, and spread RCC on it immediately, and complete the rolling before the initial setting of mortar. 7.7.6 While the construction is interrupted by construction schedule change, rainfall or other reasons, the spread concrete should be rolled in time. The concrete face at where the placing stops should be rolled into inclined slope not more than 1:4, and ekscind the part with thickness less than 15cm. While the construction condition resumed, continue construction after treating the layer and t surface according to the interrupted time. 7.8 Casting of dissimilar concrete 7.8.1 The conventional concrete should be placed with the RCC of main body synchoronously. 7.8.2 The binding part of conventional concrete and RCC should be treated seriously as shown in graph 7.8.2. The two kinds of concrete should be placed alternately, and the conventional concrete is required to compacted before initial setting; the rolling of RCC should be finished in the permissible intermittent time between layers. Vibrating scope of vibrator Conventional concrete\ RCC (a) Vibrating scope of vibrator Conventional concrete\ RCC (b) (a) first placing conventional concrete and then RCC; (b) first placing RCC and then conventional concrete Graph 7.8.2 Treatment of binding part of dissimilar concrete 7.9 Casting of abnormal concrete 7.9.1 The abnormal concrete should be constructed layer by layer accompanying the RCC casting, and the plaster should be sprayed at the bottom and middle part of the newly compacted concrete. The placing layer thickness of abnormal concrete should be as the same as the block leveling thickness, and the plaster consumption should be determined by test. 7.9.2 The used mortar plaster in abnormal concrete is made of cement, flyash and ixture. Its water-binder ratio should be no larger than that of the same type RCC. 7.9.3 The plaster should be used strictly following the regulated quantity, and spread in the abnormal scope or 30cm-50cm near the rock face or formwork. The plaster consumption deviation per unit volume of concrete should be controlled in the allowed range. 7.9.4 The homogeneity and binding between layers of abnormal concrete should be ensured by forced vibration. The overlapping width between

abnormal zone and adjacent zone should exceed 20cm while compacting. 7.9.5 The layer and t surface treatment of abnormal concrete should be carried out as per the regulations in 7.7 of this standard. 7.10 Curing and protecting 7.10.1 The RCC block should be kept wet during construction. 7.10.2 Prevent out-coming water running into the block under construction or just finished rolling. 7.10.3 During construction interval, water curing should start after the final setting of RCC. For the horizontal construction t and cold t, the water curing should sustain till the placement of the upper layer of RCC; for the permanent exposed surface, the curing time should not less than 28d; the curing of edge angle of step-like surface should be strengthened. 7.10.4 Corresponding curing measures should be taken for the RCC with temperature control requirement according to temperature control design; and special protective measures should be made for low-temperature season and cold spell. 7.11 Construction of embedded parts 7.11.1 Later-embedding should be taken for the embedding of monitor equipments and cable in RCC. A backfill protective layer larger than 20cm should be ensured at the top of the pit depth for the instruments and cables without direction requirement. A backfill protective layer at least 50cm should be made at the upper part for the instruments without direction requirement. The backfill material should be flesh concrete removing the aggregate larger than 40mm from the original concrete mix design. 7.11.2 Measures must be taken for the backfill concrete in the pit to ensure good binding with the surrounded concrete. Artificial backfill in layers should be adopted except for cable, and compact with wood hammer to ensure the compactness of backfilled concrete. For cable or bunch of cables, mortar should be backfilled into the pit to avoid forming leakage age. 7.11.3 Reasonably arrange the construction schedule according to the elevation of embedded equipments, try to make the horizontal construction t during construction interval become the excavation layer of pit, and guarantee the good cooperation and coordination between embedding and concrete placing. 7.11. 4 The embedded equipments should be maintained and protected. While the initial setting of backfilled concrete at the embedded area has not finished or the upper layer of concrete has not been placed, all equipments are forbidden to walking on. 7.11.5 Monitor should be strengthened in the instrument installation, embedding, and concrete backfilling. If the equipment is found unusual or broken, take remedy measures in time. After the instruments and cables

are embedded, and be confirmed qualified after testing, record the initial reading, draw embedding sketch, and fill in the construction record. 7.11.6 Preserve a certain surplus length for the monitoring cable near the embedding point. 7.12 Construction under special meteorologic condition 7.12.1 Strengthen the collecting of meteorologic forecast information during construction, know the rain condition and temperature condition observed on site, and arrange the construction progress appropriately. 7.12.2 If the rainfall intensity is less than 3mm/h, and the construction can go on after taking measures. If the rainfall intensity equals or exceeds 3mm/h, stop mixing, and finish the outstanding dumping, leveling and rolling quickly. Take rainproof and discharge measures for the blocks just being rolled. 7.12.3 Before resume construction, the RCC lost plaster should be strictly treated. The layer surface and t surface should be treated according to the regulations in 7.7. 7.12.4 While construction under strong wind or dry weather, special measures should be taken to keep the block wet. 7.12.5 While the mean daily temperature is higher than 25℃, the intermittent time between layers should be greatly reduced. Take measures to prevent high-temperature, sun-shading and adjust the local microclimate so that the surface moisture will not evaporate and lose quickly during concrete transportation, spreading and rolling. 7.12.6 Low-temperature construction measures should be taken while the mean daily temperature is lower than 3℃ or the lowest temperature is lower than -3℃. 8 Quality management and assessment 8.1 Testing and controlling of raw materials 8.1.1 The field test item and test frequency of raw material of RCC should be carried out according to table 8.1.1 8.1.2 Strictly control the water content and graduation of fine aggregate. The permissible deviation of modulus of fineness of sand, and the mix proportion of RCC should be adjusted while it exceeds. The fine aggregate should have a certain time of dewatering, and its water content before mixing should be less than 6%. The permissible deviation of water content is 0.5%, and the water consumption of concrete mixing should be adjusted while it exceeds. 8.1.3 The exceeding and inferior grain in coarse aggregate of each graduation should be strictly controlled. While testing with round-hole mesh, its control standard is: exceeding grain less than 5%, inferior grain less than 10%; while testing with exceeding and inferior grain, its control standard is: exceeding grain is zero, and inferior grain is less than 2%. The permissible deviation of water content in stone is 0.2%. 8.1.4 The ixture should be stored respectively as per variety and

mobilizing date, and the storage place should be ventilated and dry. The ixture being tested qualified should be retested before use if it has been stored over 6 months. The ixture must be made into solution and mixed evenly while being used, and be stored in the indoor vessel to avoid contamination. Table 8.1.1 Test item and test frequency of raw material Name Cement

Flyash

Fine aggregate

Item

Specimen location Fast test the Cement grade storage of mixing plant Fineness, Cement stability, storage water consumptio n of standard consistency, setting time, grade Density, Warehou fineness, se water demand ratio, ignition loss Strength ratio

Frequenc y If it is necessar y

Mixing plant

To the cement activity

Twice To test the per 200t- cement 400t 1) quality leaving the factory

Twice Assess per 200t- quality 400t 1) stability

If necessar y Once per day

Modulus of Mixing fineness plant, screening plant Graduation If necessar y Water content

Aim

Test activtity

The screening plant controls production and adjust the mix proportion Once per Adjust 2h or if water

necessar y Sediment percentage, unit weight Coarse Large-sized aggregat stone e

Mixing plant, screening plant Exceeding Mixing and inferior plant, diameter screening plant

consumpti on of concrete

If necessar y

Once per screening shift plant controls production and adjust the mix proportion MediumWater Mixing Once per Adjust sized stone content plant shift or if water necessar consumpti y on of concrete Small-sized Content of Mixing If stone clay, silt, plant, necessar and fines screening y plant ixture Solution Mixing Once per Adjust the concentrati plant shift mixing on quantity of ixture 1) it should be tested once while less than 200t per batch 8.2 Testing and controlling of newly mixed RCC 8.2.1 The weighing apparatus for batch weighing of RCC should be checked once a month, and the allowable deviation of batch weighing follows the regulations in table 8.2.1. Table 8.2.1 Test standard for batch weighing Material Water Cement and Coarse and ixture name flyash fine aggregate Allowable 1% 1% 2% 1% deviation 8.2.2 After determined the model of mixer, test the mixture homogeneity of RCC through test so as to determine the mixing time and feeding order. The testing results of mixture homogeneity of RCC must comply with the following regulations: 1 While testing the coarse aggregate content with washing-analysis

method, the D-value between the two samples should be lower than 10%; 2 While testing the unit weight with mortar unit weight analysis method, the D-value between the two samples should be not larger than 30kg/m3. After the batching plant is put into operation, it should be tested regularly. 8.2.3 The test of RCC quality can be done by sampling from the outlet of the mixer. Test item and frequency follows the regulations in table 8.2.3 Table 8.2.3 Test item and frequency of RCC Item Frequency Aim VC value Once per 2h 1) Test the compactability of RCC and control the viability of workability Air content 1-2 times per shift Adjust the quantity of while using air ixture entraining agent Temperature Once per 2h-4h Temperature control requirement Compression strength Once per 300-500m3, Test the RCC quality specimen at least once and construction for each shift while quality less than 300m3 1) the testing times should be added appropriately while the climate change greatly (strong wind, rain, high-temperature) 8.2.4 After the VC value of RCC value is chosen, if the allowable deviation at the outlet of the machine exceeds the 3s controlling limit, the reason should be found out. Modify the mixing water consumption of RCC and keep the water-binder ratio unchanged. 8.2.5 Strictly control the air content of RCC mixed with air entraining agent, and the allowable deviation is 1%. 8.3 On-site quality testing of RCC 8.3.1 While placing RCC, it should be tested according to regulations in table 8.3.1, and should be recorded. Table 8.3.1 On-site testing item and standard of RCC placing Item Frequency Control standard VC value Once per 2h The allowable deviation of VC value on site is 5s Compression strength Amount to 5%-10% of the sampled quantity at the outlet of the mixer Compacted density Refer to 8.3.2 The tested unit weight of each placing layer should reach the

Aggregate separation

Whole-process control

Intermittent time Whole-process control between two rolling layers

relative compactness index regulated in 8.3.4 Aggregate concentration is not allowed The permissible intermittent time between layers under different temperature should be determined by test, and judge according to it Less than 2h

The period from Whole-process control adding water to mix the concrete to the rolling finished Entering block Once per 2-4h temperature 8.3.2 The compacted density shall be tested by nuclear moisture-density gauge or compaction densitometer. There should be at least on testing point for per 100m2-200m2 RCC placed, and more than 3 testing points should be arranged for each placing layer in the block. Take the result tested by the nuclear moisture-density gauge after 10min of rolling as the judge criteria of compacted density. 8.3.3 The nuclear moisture-density gauge should be calibrated by RCC made of actual raw materials before it is used. 8.3.4 The relative compactness is the index to assess the compaction quality of RCC. For the external concrete of structure, the relative compactness should not less than 98%; while for the internal concrete, it should not less than 97%. 8.4 Quality control and assessment 8.4.1 The specimen of RCC should be formed by sampling from the outlet of the mixer. The production quality control of RCC should be based on the 15cm standard cubic specimen and compression strength standardly cured 28d. 8.4.2 The percent of of concrete anti-frost and impervious test should not lower than 80%. 8.4.3 Refer to table 8.4.3 for the control standard of production quality of RCC. The mean square deviation and coefficient of variation of compression strength should be evaluated from a batch of (at least 30 groups) tested value of samples continuously sampled from the outlet of the mixer.

Table 8.4.3 Quality management level

Management level criteria of production quality of RCC (age 28d) Excellent

Good

Ordinary

Bad

﹤0.15

0.15-0.18

﹥0.18-0.22

﹥0.22

﹤3.5

3.5-4.0

﹥4.0-4.8

﹥4.8

Assessment standard

Assessment item Coefficient of variation Cv Mean square deviation S(Mpa)

Note: mean compression strength:

, adopt S standard of mean square deviation to assess;

, adopt Cv standard of coefficient of variation to assess

8.4.4 The quality assessment of RCC should be based on the compression strength with designed age, and assess in big specimen and small specimen according to specimen numbers. 1 Big sample. While the continuous sampling of concrete is more than 30 groups, adopt big specimen to assess, and calculate the assessment function according to the following formula:

Or

Where, F(X)-assessment function; --mean value of test compression strength of N times, Mpa; S—mean square deviation of test compression of N times, Mpa;; R—concrete strength grade (design grade), Mpa; t—coefficient of ensuring rate of strength, relevant to test times N and ensuring rate P(X). Refer to table 8.4.4-1 while N≧30. Xmin –the lowest compression strength in N times of tests, MPa; K and B—coefficient relevant to ensuring rate of strength and production control level, refer to table 8.4.4-1. While F(X)≧R or Xmin ≧KR or R+BS, the RCC is qualified. Table 8.4.4-1 Coefficient of quality assessment formula of RCC coefficient

of

ensuring rate of K B(while S is BS (S=4.3Mpa) strength t given) 0.84 0.73 -1.16 -4.98 2 Small sample. While the test group of concrete specimen is less than 6, refer to 8.4.4-2 the assessment standard. 3

When

, the quality of RCC is qualified.

Table 8.4.4-2 Allowable lowest mean strength of small specimen(Xmin) Continuous sampling group Cv=0.19 S is given When S=4.3Mpa for evaluating mean strength 1 0.73R R-1.16s R-4.98 2 0.87R R-0.57S R-2.46 3 0.92R R-0.31S R-1.35 4 0.96R R-1.16s R-0.68 5 0.98R R-0.05S R-0.23 6 R R-0.02s R-0.1 8.4.5 Boring specimen is the comprehensive method to assess the RCC quality. Boring specimen can be carried out after the RCC reached the designed age. The boring position and quantity should be determined according to elevation. The assessment contents of boring specimen are as follows: 1.

percentage recovery of core sample ： to assess the homogeneity of

RCC; 2. water-pressure test: to assess the impermeability of RCC; 3. physical and mechanical property test of core sample: to assess the homogeneity and mechanical property of RCC; 4. appearance description of core sample: to assess the homogeneity and compactness of RCC, see table 8.4.5 for the assessment standard. Table 8.4.5 Assessment standard of core specimen appearance of RCC Grade Smooth degree Density of Evenness of of surface surface aggregate distribution Excellent Smooth Dense Even Ordinary Basically With small holes Basically even smooth Bad Not smooth With part of Uneven holes Note: this table is applicable for the core specimen drilled by drill bit 8.4.6 The diameter of core specimen for compression strength testing is

better to be 15cm-20cm. For large-scale project or the project with maximum aggregate grain larger than 80mm of concrete, it is better to use core specimen with diameter 20cm or even larger. 8.4.7 Take the core specimen with height-diameter ration 2.0 as the standard specimen. Refer to Annex A for the ratio of compression strength between specimens of different height-diameter ratio and standard specimen with the height-diameter ratio 2.0. The specimen of core sample with the height-diameter ratio less than 1.5 is not allowed to be used in compression strength test. Refer to Annex A for the compression conversion relationship between

standard

specimen and 15cm cubic specimen.

Annex A (standard annex) Conversion factor of compression strength between specimen of different height-diameter ratio & cylinder and cubic specimen Table A1 Conversion factor of compression strength Strength grade Conversion factor of compression Mpa strength of specimen with different compression strength/ height-diameter ratio compression strength of 15cm cube height-diameter ratio 1.5 2.0 10-20 1.166 1.0 0.775 20-30 1.066 1.0 0.821 30-40 1.039 1.0 0.867 40-50 1.013 1.0 0.910 Note: 1 the height-diameter ratios of test specimen of elastic modulus, axial

tensile strength and tensile strain are within 2.0-3.0. 2 the conversion factor with the height-diameter ratio within 1.5-2.0 can be evaluated with interpolation method. 3 Conversion factor of compression strength of specimen with different height-diameter ratio = compression strength of specimen with different height-diameter ratio/compression strength of specimen with heightdiameter ratio 2.0

Construction specification for hydraulic roller compacted concrete Explanation of clauses

Chief Development Organization：China National Water Resources and Hydropower Engineering Corporation Approval Department: State Economic and Trade Commission of the People's Republic of China

China Electric Power Press 2001 Beijing

Contents 3 General rules…………………………………………………….. 5 Materials……………………………………………………….. 5.1 Cement…………………………………………………… 5.2 Flyash or other additive blend……………………….…… 5.3 Concrete ixture………………………………………… 5.4 Aggregate…………………………………………………… 6 Mix design………………………………………………….. 7 Construction………………………………………………… 7.1 Preparation before placing……………………………… 7.2 Mixing…………………………………………………. 7.3 Transportation…………………………………………. 7.4 Dumping and block leveling………………………….. 7.5 Rolling……..…………………………………………. 7.6 t forming………………………………………….. 7.7 Treatment of layer and t face……………………. 7.8 Casting of dissimilar concrete………………………… 7.9 Casting of abnormal concrete………………….. 7.10 Curing and protecting………………………………. 7.11 Construction of embedded parts…………………… 7.12 Construction under special meteorologic condition… 8 Quality management and assessment…………………….. 8.1 Testing and controlling of raw materials………………. 8.2 Testing and controlling of newly mixed RCC…………. 8.3 On-site quality testing of RCC……………………….. 8.4 Quality control and assessment………………………..

3 General rules 3.0.1 This clause illustrates the relationship between this Specification and the current relevant specifications and professional standards of the state. These standards mainly includes: SDJ207, SL48, DL/T5100, SL176, DL/T5123 and national standard relevant to materials and so on. 3.0.2 This clause stresses the importance of field test for RCC through which the rationality of concrete mix design can be verified; test the operating reliability and overcoatability of raw material production system, concrete preparation system, transporting system and machine tools of leveling and rolling during construction. Determine the reasonable construction technology and parameter through test, such as spreading way, leveling thickness, rolling thickness and ing number etc. In addition, it will have technical training effect on the personnel lack of construction practice experience. 3.0.3 This clause illustrates that the RCC should meet the technical requirements proposed by design. Accompanying with the more mature technique of RCC dam day after day, using RCC as the external concrete of hydraulic structure has become true. So besides satisfying the strength requirement, the RCC should also satisfy the requirement such as impermeability and frost resistance of external concrete. 3.0.4 This clause stresses the importance of temperature control in RCC construction. In the construction of RCC, the actual block-entering temperature will take great effect on the project quality. In the construction, take measures of temperature control, temperature-keeping and maintenance economically and reasonably according to the property of RCC to prevent cracking. 3.0.5 This clause is made with the purpose to favor the creation and application of new technique, new technology, new material and new equipment in the RCC construction and to guarantee the project quality. The technical achievement should be justified by the governing department of the project. 5 Materials 5.1 Cement 5.1.1 The cement quality should be in conformity with the current relevant specifications, such as requirements of GB175, GB200, and GB1344. 5.1.2 The performance of the cement being used should be ensured stable. 5.1.3 While selecting variety of cement, better to select the low-heat

cement in priority. 5.2 Flyash or other additive blend 5.2.1 The quality of flyash should be in accordance with the relevant regulations such as GBJ146, DL/T5055, GB/T1596 and GB/2847. Flyash or other additive blend is indispensable component materials of RCC. In recent years, RCC has commonly adopt great mixing quantity of flyash in RCC at home and abroad, the flyash mixing quantity of constructed RCC dam is within 50%-70% at home. The mixing quantity of flyash should be determined by test according to quality grade, design requirement. If there is no flyash resource, other active or inactive additive blend with comparatively reasonable technical and economic indices can be chosen nearby, such as tuff, phosphate slag，blast-furnace slag，tailing slag and rock powder etc. All of them could be mixed after grinding, and their mixing quantity should be selected be test demonstration. Concrete ixture 5.3.1-5.3.3 The ixture mixing in the RCC is indispensable important material for preparing high-quality RCC. According to the design index of RCC, requirements of project and construction reason, mixing ixture in concrete can not only improve the RCC property and make convenience for construction, but also can save engineering costs. In order to ensure the RCC quality, choose the ixture with good performance. The quality standard of ixture mixing in the RCC should comply with the requirements of GB8076, GBJ119 and DL/T 5100. 5.4 Aggregate 5.4.6 The rock powder produced in the artificial aggregate production with dry method will adhere to the surface of aggregate grain after being wetted, which will influence the RCC quality. The productive technology should be improved to prevent the aggregate being adhered to by rock powder, and wash the severely polluted aggregate. 5.4.8 The content of grain larger than 5mm in the sand has sensitive influence on the modulus of fineness, which should be controlled. It is controlled in 5% in some projects. 5.4.9 Several projects and repeated tests prove that proper rock powder in artificial sand will obviously improve the workability and water retention of mortar and concrete and promote the homogeneity, compactness, impermeability, mechanical index and fracture toughness property of concrete; rock powder can replace part of the flyash as additive blend of cement; properly increasing the content of rock powder can also promote the output of artificial sand, reduce the costs and increase the technical and economic benefits. Therefore, reasonable control of content of

artificial sand is in one of the most important measures to promote the concrete quality. While adopting artificial sand made of lime rock and the content of rock powder is 17.6%, each property of concrete is excellent; artificial sand made of granite has good property while the content of rock powder is 15%, artificial sand made of dolomite has good property while the content of rock powder is 20%. This shows that although there is difference between better content of rock powder in artificial sand made of different rock character, their better contents are all higher than the contents of rock powder regulated in the original Construction specification for hydraulic concrete. Seeing from the versatility, the content of rock power should be better controlled within 10%-22%. Production with dry method can promote the output of artificial sand and increase the contents of fine grain in rock powder so as to improve the workability of concrete and save equipment costs at the same time. 5.4.10 The sediment in sand means the silt and clay with diameter less than 0.08mm. The comparative tests at home and abroad relevant to the influence of sediment in sand on concrete strength prove that while the content of fine grain (less than 0.08mm) is within 3%-7% in the lean concrete, it can improve the workability, viscidity and compactness of concrete, promote the compression strength and impermeability of concrete. Accordingly, the sediment content in sand is promote from 3% to 5% in the JBJ52-1992 “Sand quality standard and test method of ordinary concrete” issued by Ministry of Construction 6 Mix design 6.0.1 The mix design of RCC should satisfy all technical indices of engineering design and construction technology, including: 1 the concrete should be homogeneous, and separation of coarse aggregate will not happen easily in construction; 2 the workability is appropriate, the mixture is relatively easy to be compacted, and the unit weight of concrete is relatively great; 3 the initial setting time of mixture is long, and easy to ensure good bonding between construction layers of RCC, and the physical and mechanical properties of layers are good; 4 the mechanical strength and impermeability of concrete meet the design requirements, and the concrete has high capacity of tensile strain. The RCC out of the structures should have durability adapting to the environment of the structure. 6.0.2 The mixing quantity of additive blend in permanent and important structures at home has reached 60%-65% (e.g. the mixing quantity of additive blend in dam RCC of hydropower station of Tianshengqiao Second Grade and Yantan are 60.7% and 65.4% respectively. The mixing quantity of additive blend in Shangjing Dam of America has exceeded 70%. The research results of Wuhan University of Hydraulic and Electrical Engineering indicates that it is feasible to use RCC with

excellent flyash and mixing quantity larger than 70% as the internal concrete of mass hydraulic structure. The concrete strength has a certain increase during 8-9 years, the internal structure of concrete is continuously improving and the impermeability and anti-erosion of concrete are strong. The research result of Yangtze River Scientific Research Institute on clinker covering 16.5% of low-clinker RCC indicates: the hydration and sclerous reaction of this kind of concrete are basically consist with conventional concrete, its major hydration productions are stable, and the internal structure of concrete is dense. So 65% is feasible for the maximum mixing quantity of additive blend. The water-binder ratio of RCC should be different according to the materials of each project and technical requirement, and should be determined by test. Generally, the water-binder ratio of each project at home is within 0.50-0.70. The sand rate directly influences the construction performance, strength and duration of concrete. While determining the mix proportion of RCC, the best sand rate should be selected through test, i.e. the sand rate which can get good anti-separation after concrete mixing, reach the VC value required in construction and use the least cementing materials. The scope of sand rate listed in this clause is the general scope for projects at home. The selection of water consumption per unit does not only connect with the rollability but also relevant to economical efficiency. So while the rollability is satisfied, the smallest water consumption per unit is usually adopted to save cement and additive blend. For the graduation III RCC, the water consumption is within 70kg/m3-110kg/m3. 6.0.3 According to the project construction experience at home, in order to guarantee the rollability of RCC, easily bleeding and bonding quality between layers, the proper on-site VC value of mixture should be within 5s-15s. Taking of the influences of transportation, different temperature condition and water absorption on the VC value of mixture, the VC value 5s-12s at the outlet of mixer recommended by this clause should only be taken as the VC value of mix design. Because all kinds of factors may influence the on-site VC value in actual construction, therefore, the VC value at the outlet of mixer can be less than 5s while the normal compaction on site is satisfied. 6.0.4 The construction practices indicate: while the cementing material consumption is less than 120kg in per cubic meter of RCC, the impermeability of the hardened concrete will be poor. In order to guarantee that the prepared RCC satisfy the impermeability requirement of mass hydraulic concrete, the cementing material consumption per unit required by this clause should not be less than 130kg. This limitation is not applicable for small-scaled projects and temporary projects.

7 Construction 7.1 Preparation before placing 7.1.1 The characteristics of RCC construction are quick, continuous and high-mechanized construction. Failure, incoordination or unsuitability occurring to any link of the whole production system will impact the project progress and the exertion of RCC construction characteristics. That’s why this clause is formulated. 7.1.2 The operation qualification of construction personnel has great influence on the construction quality especially on the earlier construction quality. So the training should be strengthened after the construction begins. 7.1.3 The detailed plan arrangement of block is the embodiment of construction technology in the block, which can avoid arbitrariness of construction, ensure the strictly execution of construction technology, and be helpful to promote the construction efficiency, and be taken as the basis of field inspection. 7.1.4 It is not convenient for RCC concrete placing on the accidented rock foundation, so a certain thickness of bending concrete or abnormal concrete to make the surface level. The construction practices in the recent years indicate that the quality and property of RCC can completely reach those of conventional concrete. So the leveling course should not be too thick in order to turn to RCC construction quickly, which will be helpful to temperature control and construction progress. 7.1.5 Formwork is the important equipment for RCC dam construction, and has great influences on appearance, quality, construction progress and costs of RCC. So the selection of formwork has the same importance with allocation of mechanical equipment. The design of formwork should meet the requirement of quick and continuous construction of RCC. For the convenience of surrounded placement, no inclined stay should be set up. Waterstop, entrance and exit of block, and part of hole structure are the position where has high requirement or problems come out, and they should be stressed in the design. Step mode may be taken for the downstream surface, but the height of step should not be too small. 7.2 Mixing 7.2.1 Forced mixer is applicable to mixing dry and hard concrete. According to the construction experience abroad, and construction practice of guide wall of Shuikou Hydropower station, dam of Guanyinge reservoir and dam of Jiangwan Hydropower station, RCC mixed with forced mixer does not only have good quality, but also has short mixing time. According to the construction practice abroad, the mixers such as fall-free type can also mix RCC with good quality. Additionally, the continuous mixer is also commonly used abroad. 7.2.2 Except checking the accuracy of the weighing devices themselves,

the actual batching result should also be checked while inspecting the weighing system. 7.2.3 Practices indicate that the required time for even concrete mixing is influenced by concrete mix design, type of mixing equipment, feeding order and mixing quantity. Therefore, the feeding order and mixing time should be determined by mixing test. 7.2.4 The water content variation of fine aggregate will obviously influence the workability and water-binder ratio of concrete mixture. Generally, the modern batching plants are usually installed with quick testing devices of water content in sand, and have the adjusting and complementing function of corresponding mixing water. 7.2.5 For RCC, the larger fall it has while being dropped, the more serious aggregate separation will come out. So this clause limits the height of free fall of concrete mixture. 7.2.6 The consumption of mortar and plaster are great in RCC dam, and should be stressed as the same as concrete. In order to guarantee the quantity, the mortar and plaster must be fresh while being used. Mixing plaster with machine is for the purpose to keep its homogeneity. The plaster consumption of large-scaled project is great, and concentrated mixing station should be set up to supply plaster. 7.3 Transportation 7.3.1 According to construction practices at home and abroad, dumper, belt conveyor, negative pressure chute (pipe), special vertical straight chute are relatively mature. Cable crane, gantry crane and tower crane can also be used as auxiliary transportation tools. 7.3.2 While transporting concrete with dumper, the number of entrance to the block, structure and construction method of block sealing have great influence on the quality and speed of construction; the filth and soil being carried by the wheel will influence the bonding quality of concrete layers. The water being carried in will change the workability and water-binder ratio of the concrete and influence the concrete quality; sudden brake and sharp turning will damage the strength of concrete surface not high enough and influence the bonding between layers; the ing gap left on the structure can be filled in the consequent construction. 7.3.3 The sun-shading and rainproofing measures can reduce the influence of external environment on the concrete consistency ； aggregate separation may easily happen while the aggregate is transferred between belt conveyors, so anti-separating devices should be installed at the discharge end; larger groove angle is favorable to slow down the separation on the belt; practices indicate that proper scraper and cleaning device will control the loss of plaster. 7.3.4 In the usage of negative pressure chute (pipe), accompanying with the increase of the damage of cover tape, the speed of concrete at the

outlet may reach 10m/s-15m/s, and the concrete will be discharged directly on the dumper, which will cause great impact and aggregate separation. Install elbow downward at the outlet will greatly slow down the speed and mix the concrete, which will prevent impact and separation effectively. A section of circumferential split of cover tape can be added, and repair in the way of imbricate connection. The radial slit can be partly replaced after cutting the slit part. The whole cover tape should be replaced while the mean distance of circumferential split of cover tape is less than 3m-5m or the negative pressure reduce rapidly and the speed and separation at the outlet are out of control owing to broken of cover tape. 7.3.5 Adopting purpose-made rubber hose and other chute with special structure will effectively prevent aggregate separation. Clogging-control is for the purpose to ensure the equipment safety. 7.3.6 In order to guarantee the continuous running of continuous equipment, the volume of storage hopper should be enough; the camber of transferring funnel has great impact on the capacity of transporting system. 7.4 Dumping and block leveling 7.4.1 Level course full-length placement is the most popular adopted way at home and abroad. The aim of adopting inclined-layer placing method and step method is mainly to reduce the placing area and shorten the intermittent time between layers. According to the construction practices, inclined-layer method can cast lager-sized block with small casting capacity to realize the aim of reducing input, promote work efficiency, reducing costs and improving quality of layer bonding. The effect of this kind of construction method is in evidence in higher temperature season. 7.4.2 According to the practice of Jiangya project, the construction can be carried out normally while the slope of inclined layer is 1:10, and it’s hard to ensure the even thickness of spreading if the slope is too steep. Avoiding forming thin layer sharp angle at the foot of the slope and strictly cleaning the secondary contamination are the two main problems to ensure the construction quality of inclined-layer placing method. 7.4.3 Placing belt by belt in the fixed direction makes the construction layer clear, the intermittent time between layers easily controlled, and the construction in order. The leveling direction in parallel with the dam axis in the scope of 3m-5m upstream is for the purpose to avoid forming potential weak zone in the direction of flow at important parts. 7.4.5 The unqualified concrete mentioned in this clause means: the VC value of concrete mixture exceeds the scope determined on site; the content error of each group exceeds the regulated scope; the mixed concrete quantity is damaged due to human factors. 7.4.6 According to construction practices, level the concrete from the dumped position with bulldozer when the compacted thickness is 30cm

and the leveling thickness is 34cm, the better effect of improving separation can be gain. 7.4.7 In order to guarantee the rolling quantity, the leveling quantity must be also guaranteed. Make the thickness of rolling layer even. 7.5 Rolling 7.5.1 According to project practices of our country, BW-200, BW-201AD and BW-202AD made by former West are more applicable. The products with similar performance abroad and vibrating roller made at home can also be adopted if their vibrating force and vibrating frequency met the technical requirements after tests. 7.5.2 Project practices show that rolling the part near the formwork directly with large-sized vibrating roller can get high construction efficiency and good quality. 7.5.3 The walking speed of vibrating roller directly influences the rolling efficiency and compaction quality. The compaction effect is bad if the walking speed is too fast according to construction practices at home. The speed can increase to 1.5km/h while the ing number is properly added. 7.5.4 The compaction thickness of different vibrating roller is different, and the required ing numbers for mixture with the same mixing proportion is also different for different vibrating rollers. The rolling thickness and ing number can be determined through site test combining with the comprehensive production capacity of production system. Adopting different rolling thickness according to conditions in construction will be helpful to meet the requirement of intermittent time between layers. If the rolling thickness is less than 3 times of the maximum grain diameter of aggregate, the compaction effect will be influenced by the maximum grain diameter aggregate or the aggregate will be crushed. 7.5.5 Leakage age owing to bad between rolling belts can be avoided if the rolling direction is perpendicular to the flow direction. Therefore, the rolling direction in the scope of 3m-5m upstream must be perpendicular to the flow direction. Feasible measures must be taken while inclined-layer placing method is adopted. The overlapping of rolling belts is mainly for the purpose to guarantee the compaction quality of the overlapping parts. The overlapping length at the ends should ensure that both the front and back wheel of the vibrating roller can enter the overlapping scope. The overlapping length can be determined by the axle base of the selected vibrating roller. 7.5.6 The value of compacted density is the major mark to judge whether the RCC is compacted, so it should be tested following the rolling in construction. When the tested unit weight is lower than the regulated index, add the ing number, test again, if still could not reach the

regulated index, analyze the reason and take corresponding measures. The spring soil occurred in rolling process can be ignored if the compacted density can meet the requirement. 7.5.7 Rolling without vibration can heal the slight surface crack. 7.5.9 In order to avoid concrete quality problems owing to long standing time of mixture, the time from mixing of mixture to the finished time of rolling should be limited，and it should be determined according to VC value variation under different weather and influence on compacted density. The rolling work should be finished in 2h after the concrete mixing begins according to the tests on retaining wall of switch station of Shaxikou hydropower station and cofferdam project of Yantan, the faster the better. The situation of Jiangya project is similar to this. The time should be shorten while the temperature is high and be prolonged while the temperature is low or in rainy days. The finished rolling time of the part being rolled with the next belt at the same time should be strictly controlled in the maximum intermittent time between layers that can satisfy the bonding quality between layers. 7.6 t forming 7.6.1 According to the project practices, the t can be successfully formed by cutting with grooving machine, setting up induce hole or presetting t partition. 7.6.2 There are two ways to form ts with grooving machine: “cutting first, rolling later” or “rolling first, cutting later”. In order to guarantee the formation of t, the regulated t-forming size of each layer should meet the requirements, and the left part should wait for the natural tension fracture of the concrete. Galvanized sheet iron can be used as the materials filling in the t. Some projects adopted chemical fiber cloth or dry sand to fill in the t. 7.6.3 While placing continuously in thin layers, the induce hole can be formed by hitting poker bar by man or boring with air drill. Fill dry sand into the hole after it is formed to avoid the induce hole being filled by concrete while the upper-layer is constructed, which could not realize the aim of forming induce t. While intermittent-type construction is adopted, the induce hole can be formed by air drill during the intermittent time between layers. The drilling of induce hole of Tianshengqiao II Grade was done after the concrete had a certain strength (about 7d age), hole diameter 90mm, distance between holes 1m, hole depth for each time 3m. The t forming was controlled accurately and the effect was good. 7.6.4 The aim of limiting the distance between partitions is to guarantee the area of formed t; the height of partition is regulated in order not to influence the concrete compactness and damage the partition. 7.7 Treatment of layer and t face

7.7.1 In order to ensure good bonding between concrete layers, the intermittent time between layers must be controlled. The control standard of intermittent time between layers directly influences the boding quality between layers. The control standard and specific measure of each project are different at home and abroad. But actually, they are all about the limitation of time. In fact, many projects at home and abroad take double standard: one is used to control direct placement, viz. permissible time interval between placing layers; the other is used to control placement while using bending mix, viz. permissible time interval between placing layers while using bending mix. The construction practices show that once choose the proper time standard, this course of action can completely meet the requirement of bonding quality and shear index between layers. Since the direct placement has simple procedure, high efficiency and good bonding quality between layers, it should be adopted in priority in construction arrangement. 7.7.2 Considering importance and complexity of the problem, permissible time interval between placing layers and permissible time interval between placing layers while using bending mix should be determined comprehensively taking of all kinds of factors. The time of medium-small scale projects can be determined by comparing with the similar type projects. Different dams have different standards. Even for the same dam, the standard should also be discriminating for different conditions and different parts. Generally, the permissible time interval between placing layers can adopt the initial setting time or time a little less than that under normal weather condition. The two periods of Jiangya project are 6h and 24h respectively. The actual permissible time interval between placing layers adopts the initial setting time, and actually tested longest permissible time interval between placing layers while using bending mix is 22h, usually it is within 18h-22h. 7.7.3 The construction t and cold t in RCC dam are weak links. Leakage age is usually formed, which will influence the stability of anti-sliding, and should be seriously treated. 7.7.4 The purpose of brushing and greencutting is to clean the laitance, filth and loose aggregate on concrete surface, increase the roughness of the surface and enhance the bonding capacity between layers. Placing bending mix on the treated layer will guarantee good bonding between upper and lower layers. Brushing and greecutting vary accompanying with difference of concrete mix proportion, construction season and mechanical performance. Usually, they should be done after initial setting and before final setting. Greecutting too early not only causes concrete loss, but also damages the concrete quality. So this clause regulates that greencutting in advance is not allowed. 7.7.5 According to construction practices at home and abroad, there are successful experiences for bending mix adopting plaster and mortar.

While adopting mortar, special mix design should be made according to using part, and should be one grade higher than RCC strength. The t surfaces of construction t and cold t are rougher after roughening treatment and flushing clean. In order to guarantee sufficient filling and great 富裕度, mortar with the thickness of 1.0cm-1.5cm should be used. Spread the concrete closely after the spreading of mortar layer to prevent water loss or initial setting of the spread concrete. 7.7.6 While the RCC placement is stopped due to change of construction schedule, rainfall or other reasons, the slope where the placement stops should not be steeper than the steepest slope (1:4) for vibrating roller working. The concrete on the slope should be compacted. The sharp angle with thickness less than 10cm-15cm is hard to compacted and should be eliminated. According to construction practices, while the construction condition resumes where the construction suspended, its bonding quality can be reliably guaranteed as long as the layer surface is treated according to the regulation of intermittent time between layers. The bonding quality between layers can also be guaranteed as long as the damaged surface is treated according to 7.5.8. Generally, the strength of RCC increases slowly, and the effect of waiting for its increase is not evident. So in order to enhance the construction efficiency, the construction can be resumed immediately after the condition is available. 7.8

Casting of dissimilar concrete(异种混凝土)

7.8.1 The aim of synchronous casting is to guarantee the bonding quality of interface between two kinds of concretes. The conventional concrete of middle outlet, bottom outlet, overflow surface and pier and so on where requires high smoothness of surface or with greater thickness or volume and the RCC of dam body are hard to guarantee their appearance and quality, and the rising speed will be influenced. At the same time, they are hard to cast alternately and synchronously. So it is better to cast in two stages, but good bonding between stage I and II must be ensured. 7.9 Casting of abnormal concrete 7.9.1 Abnormal concrete is the RCC with rich mortar by spreading mortar during the placement of RCC. It can be compacted by vibrating method level by level accompanying with RCC construction. The abnormal concrete is popularly used in many projects at home, and the effect is well. According to construction practices, the spreading thickness of RCC with mortar can be as the same as block-leveling thickness, so as to reduce the artificial work quantity and enhance the construction efficiency. The added mortar quantity should be determined by test according to specific requirements. 7.9.3 In order to guarantee the quality, the measurement of tools

spreading mortar and the corresponding spread size must be calibrated accurately, and the construction should be organized abrasively. 7.9.4 The construction of abnormal concrete should be carried out before rolling, and a certain width should be overlapped while rolling to guarantee good transitional bonding between abnormal zone and rolling zone. Strong vibration is the necessary measure to guarantee the homogeneity of abnormal concrete, bonding between upper and lower layers and bonding quality of rolling zone. The abnormal concrete can be replaced by the low-slump non-plastic concrete with same mix proportion mixed by mixer. 7.10 Curing and protecting 7.10.1 RCC is non-plastic concrete which will be greatly influenced by the external environment, so the concrete in the block is required to keep wet. 7.10.3 The water consumption of RCC per unit is small, and the earlier strength is low. In order to avoid crack, the curing time should be longer than that the conventional concrete. The edge angle is easy to crack, and the curing of it should be strength. 7.11 Construction of embedded parts 7.11.1 In order not to obstruct the rolling construction and not to damage the embedded parts, later-embedding method should be adopted for the internal monitor instruments and cable. In order to guarantee the rate of instrument in good condition and working accuracy, sufficient backfilling protection layer must be ensured on the top according to different types of instrument. 7.11.2 While the protection layer is filled back, if the RCC had exceeded the permissible time interval between placing layers, bending mix should be used at the connecting part to guarantee good bonding between backfilling concrete and rolled concrete when the concrete is filled back. While it is filled back by man in layers, removing the big aggregate is the important measure to guarantee the rate of instrument in good condition. The cable may cause concentrated leakage age, so the compactness of backfilled mortar must be ensured. 7.11.3 It is quite beneficial to the rate of instrument in good condition if the instrument embedding is being done on the horizontal construction ts. Good cooperation and coordination between placing and embedding is one of the most important factors to guarantee the rate of instrument in good condition. 7.11.4 According to construction practices, roll the surface of backfilled concrete directly with mechanical equipments may still damage the instrument before its initial setting, that’s why this clause is formulated. For the continuous rising rolling layers, a layer of concrete should be placed on the instrument embedding part before the normal placing work goes on.

7.11.6 Preserve a certain surplus length near the embedding part of monitor cable to guarantee the connection between instrument and cable in rolling construction. 7.12 Construction under special meteorologic condition 7.12.2 The rainfall intensity should be controlled in construction as per the equivalent value of rainfall measured in 5min-10min. 7.12.4 The moisture on the surface of the concrete loses quickly in strong wind. In order to guarantee the rolling compactness and good bonding between layers, spraying measures should be taken to complement moisture and keep the block humid. 7.12.5 The principal way to guarantee construction quality in hightemperature weather is to greatly reduce the intermittent time between layers, meanwhile, take measures to control and complement the evaporation and loss of surface moisture. 8 Quality management and assessment 8.1 Testing and controlling of raw materials 8.1.1 Table 8.1.1 is made according to project construction experience at home and referring to foreign data. The aim for testing raw material: check whether the quality of cement, additive blending, aggregate and ixture can meet the quality standard, and adjust the mix proportion of RCC and improve the construction technology, as well as assess the production control level of raw materials. 8.1.2 The production of fine aggregate should be mainly controlled in of graduation and water content of sand. The variation of fineness modulus of sand will cause the workability variation of RCC. Therefore, it is necessary to control the fineness modulus of sand in the variation range for stable RCC production. While the D-value between the tested results of fineness modulus of sand and the given value has exceeded 0.2 of the allowable deviation, the mix proportion of RCC should be adjusted. The water content of the sand in RCC construction should be more strictly controlled than the conventional concrete. Because when the allowable deviation of water content exceeds 0.5%, it will arouse unstable workability of RCC. In principle, the water content should be tested continuously, and should be checked according to regulations with traditional oven dry method. 8.1.3 For the coarse aggregate produced on site, mainly control its exceeding and inferior grain and the water content in each grade of stone. The exceeding and inferior grain inspection should be done with 原孔筛 or exceeding and inferior grain screen. Mainly test the water content of small-sized stone (5mm-20mm) for coarse aggregate. The tested results of water content of small-sized stone, RCC workability (VC) and compression strength show that the

fluctuation of water content of small-sized stone will cause fluctuation of RCC workability (VC) and compression strength or vice versa. 8.2 Testing and controlling of newly mixed RCC 8.2.1 The weighing accuracy of each ingredient of each pan of RCC is one important factor influencing RCC production quality. So the weighing apparatus should be check regularly. 8.2.2 The ingredients of RCC should be mixed evenly. The proper mixing time differs according to RCC workability, volume of mixer, type and feeding order, and should be determined by mixing test. 8.2.3 The emphasis of RCC quality test and control is the newly mixed concrete not setting after came out of the mixer. The aim is to find the factors out of control in construction and adjust accordingly to avoid causing quality accident in structure. Make a certain amount of compression strength specimen to assess whether the design requirements are satisfied by RCC quality. 8.2.4 According to construction experiences of projects like Yantan, Tongjiezi, Tianshengqiao II Grade, Shaxikou and Kengkou, the allowable deviation of VC value at the outlet of the mixer is determined as 3s. 8.2.5 The test results of RCC mixed with air entraining agent points out that: the mixing of air entraining agent will reduce the water consumption while keeping the same workability, if the water-binder ratio does not change, the cement can be saved. The greater the air content is, the more cement is saved. But the compression strength reduces accompanying with the increase of air content. The air content of RCC mixing with air entraining agent should be strictly controlled. Otherwise, the compression strength will reduce excessively owing to too much air content, which may cause quality accident of project. The variation range of air content should be controlled within ±1%. 8.3 On-site quality testing of RCC 8.3.1 This clause is formulated based on the construction experiences of projects such as Tongjiezi, Shaxikou, Kengkou and Jiangya. The allowable deviation of VC value 5s refers to the tested value on cast field. The proposing of permissible intermittent time between layers is to guarantee good bonding between layers and make layers satisfy the requirements of strength and impermeability. Therefore, it is proposed that “the permissible intermittent time between layers under different temperature should be determined by test”. 8.3.2 Some experiences have been accumulated for testing compacted apparent density with surface nuclear moisture-density gauge. And some of the products at home have reached the requirements of performance and quality. So it is regulated that the compacted apparent density should be tested with surface nuclear moisture-density gauge. Since there is a releasing period of energy after rolling compaction, so it should be tested 10min later.

8.3.4 The apparent density of RCC must reach higher than 97% of the theoretical unit weight of mix design to meet the basic requirements of gravity stabilization and compactness of RCC dam. 8.4 Quality control and assessment 8.4.1 The compression strength of 28d specimens molded by sampling from the outlet of the mixer is mainly used to judge the quality management level of RCC mixture production. 8.4.3 The criteria listed in table 8.4.3 is formulated based on ordinary concrete referring to American ACI-214. 8.4.4 Whether the RCC quality can meet the design requirement or not, assess it in big sample and small sample according to sample times. Take the Cubic compressive strength with designed age as the basis. For the big sample, assess the quality of RCC with the same grade according to week, ten days or month. The small sample reflects fast, it is to assess the RCC quality of one placing layer or one placing day. According to mathematical theory of statistics, the larger the sample size N is, the closer the value of mean square deviation S will close to the truth value. Most scholars believe that N≧30 is proper, so the continuous sampling times is regulated more than 30 times. Considering one placing layer or placing day of RCC, the sampling times should not be more than 6, so the continuous sampling times for small sample is regulated less than 6. In table 8.4.4-1, the t value is the coefficient of strength ensuring rate while the strength ensuring rate of concrete is 80%. 8.4.5 The standard cubic specimen molded by sampling from the mixer concrete could not reflect the quality difference aroused by a series of construction operation, including transportation, block leveling, rolling and curing. Core-boring is the most popular method to comprehensively assess the RCC quality on site at present. 8.4.6 According to the general regulation, the diameter of core sample should be (2.5-3.0 times) larger than the maximum aggregate diameter of concrete. If the maximum aggregate diameter of RCC is 80mm, the diameter of core sample should be 200mm-240mm. Taking of driller performance in our country at present, this clause regulates that the diameter of core sample should better be 15cm-20cm. For the largescaled project or project with the maximum aggregate diameter of concrete larger than 80mm, core samples with diameter 20cm or larger can be adopted. 8.4.7 While the height of specimen is 1.7times larger than the diameter, the constraint of end surface has reduced out of . As a result, the specimen of core sample with the height-diameter ratio 2.0 is taken as the standard specimen. This is also formulated according to test data of our country and referring to specifications of ASTMC42-77 of America and BS1881.4 of UK. Considering the maximum aggregate diameter is 80mm for projects and the constraint problem of end surface, it is regulated that

the core sample with height-diameter ratio less than 1.5 is forbidden to be used in compression strength test.