Gsp-255_9780784413593.001 5e5245

Advanced Characterization of Asphalt and Concrete Materials GSP 255 © ASCE 2014

Mix Design for Full-Depth Reclaimed Asphalt Pavement with Cement as Stabilizer Yue Huan Yang1, Ying Biao Wu2 1

Engineer, CangZhou Municipal Engineering company, CangZhou City Hebei Province, China 061000;

Institute of Civil Engineering Hebei University of Technology, Tianjin, P.R. China, 344000 E-mail: [email protected] 2

Senior engineer, General Manager, CangZhou Municipal Engineering Company, CangZhou City,

Hebei Province, P.R. China 061000

ABSTRACT: A rational rehabilitation design should base on the understanding and knowledge of the existing pavement distress/condition. The purpose of this research was to investigate the effects of reclaimed asphalt pavement (RAP) content and cement content on the strength of Full-Depth Reclamation (FDR) base. FDR for asphalt pavement with cement as the stabilizer was used as the base course. The full-factorial experimental design included: (1) five RAP contents, and (2) five cement contents. To ensure the reproducibility, there were three replicates for each specimen. The 7 days unconfined compressive strength (UCS) was used as the control parameters. The five RAP contents consisted of 0%, 25%, 50%, 75% and 100%. The five cement blending content included 0.5%, 1.0%, 1.5%, 2.0% and 2.5%. The test results indicate that the optimum design was 50% RAP and 2% cement. KEYWORDS: Cement Stabilization; Full-depth Reclamation; Reclaimed Asphalt Pavement; Unconfined Compressive Strength; Factorial Analysis INTRODUCTION Given the necessity of preserving natural resources, HeBei Province of P. R. China, has utilized Full-Depth Reclamation (FDR), with different stabilizers, to rehab thousands of miles of deteriorated streets and roads. The following sections describe the research procedures associated with Full-Depth Reclamation (FDR) with cement as the stabilizer. When asphalt surface layer and base course of the streets and roads are both seriously damaged/ deteriorated, FDR is one of the best rehabilitation strategies. The main objective of this study was to determine the optimum reclaimed asphalt pavement (RAP) and cement content. The primary tasks in this study included:  According to particle size, RAP was divided into two classes: 10-30mm and 0-10mm. The Reclaimed Base Course Pavement (RBP) was divided into three classes: 0-5mm, 5-15mm and 15-30mm.  The specimens were prepared with five different RAP contents (0%, 25%, 50%, 75% and 100%) and five different cement contents (0.5%, 1.0%, 1.5%, 2.0% and 2.5%).  7-day Unconfined Compressive Strength (UCS) was used as the evaluation criterion  The factorial data analysis was carried out using the SPSS software.

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Advanced Characterization of Asphalt and Concrete Materials GSP 255 © ASCE 2014

MATERIALS CHARACTERIZATION RAP and RBP were obtained from Shi-Huang highway renovation project. 10-25mm mineral raw gravels need to add to regenerative material, because the mechanical force made the pavement materials fragmentation in the milling planer process. So as to achieve good gradation, 0-5mm mineral finer should be blended with the RAP and RBP. Testing RAP At least 8 times of mixture samples were brought to laboratory. After drying the materials, the gradation results are presented in Table 1 and the gradation curve is shown in figure1. The gradation results for RAP and RBP suggest that additional fine materials need to be added to meet gradation requirements. Table1 Gradation Results for Recycled Road Material percentage ing sieve size（%） Item 31.5 26.5 19 9.5 4.75 2.36 0.6 0.075 RAP 100 98.8 94.6 73.8 45.4 18.5 6.4 1.3 RBP 100 95.9 91.2 64.3 39.7 25.9 11.3 3.7 grading limit for 100 90-100 72-89 47-67 29-49 17-35 8-22 0-7 base

Figure 1 Gradation Curve for Recycled Materials The asphalt extraction results from RAP are given as follows:  asphalt-aggregate ratio 4.02%,  penetration 3.2mm,  ductility 92mm at 15℃,

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Advanced Characterization of Asphalt and Concrete Materials GSP 255 © ASCE 2014

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 softening point at 62℃,  viscosity 3421pa·s at 60℃. The results indicated that reclaimed asphalt was significantly aged. It basically meets the technical requirements of 30# matrix asphalt. The effective calcium oxide and magnesium oxide content of RBP was 3.0%. EDTA titration method to determine the lime dose was close to zero. Crushing value of RBP was 13.4% and the apparent relative density was 2.69 g/cm3. Testing Cement BoHai “god lion” brand cement used in this study was tested. Table 2 shows the engineering index test result. Relative indicators met the specification requirements. Table 2 Engineering Index Test Results for Cement Setting Time

Grade of

Fineness/%

Cement P·S32.5

Standard

（min）

Consistency Initial

Final

28d-Compressive Strength /Mpa

Setting Setting 1.1

29.4

327

486

37.5

28d-Flexural Strength

Soundness

/Mpa 6.7

Conformity

Figure 2 the Blending Target Curve with Regenerated Mixture METHODOLOGY The FDR methodology for combination of RAP and RBP using cement as stabilizer is presented. The design target proportions for RAP and RBP were selected

Advanced Characterization of Asphalt and Concrete Materials GSP 255 © ASCE 2014

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as: (1) RAP blending proportion 0%, 25%, 50%, 75%, and 100%, and (2) RBP blending proportion 100%, 75%, 50%, 25%, and 0%. The five cement blending contents are 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%. The optimum moisture content and maximum dry density were determined according to the conventional compaction test. Mix design According to “Technical Specifications for Construction of Highway Road Base”, deg cold mix recycled mixture with cement stabilization (CTB-25) specified gradation limits. Figure 2 shows the gradation curve. Determine the maximum dry density (MDD) and optimum water content (OWC) Construction of cold mix recycled mixture with cement stabilization need the right amount of water, which ensure the workability for the mixture, but excessive moisture will have negative effects on mixture performance. Conventional compaction test was used to determine the MDD and OWC. In the testing process, cement content was set at a constant value of 2.0%, while moisture content varying from 4.0%, 5.0%, 5.5%, 6.0%, 6.5%, to 7.0%. Test results are shown in Table 3. From quadratic fitting curve of dry density and water content, maximum dry density and optimum water content were obtained. Table 3 Optimum Water Content and Maximum Dry Density for Mixture with Various Blending Ratio RAP proportion 0 25 50 75 100

RBP proportion 100 75 50 25 0

Optimum water content % 6.6 6.4 6.1 5.6 5.6

Maximum dry density g/cm3 2.171 2.129 2.115 2.111 2.078

The effects of RAP content on MDD and OWC is presented in Figure 3. It indicates that with increasing RAP blending content, there was a MDD and OWC decline trend. When the RAP blending content is more than 75%, there is a reduced changing trend of OWC. When the RAP blending content is between 25% and 75%, changing trend of maximum dry density is mild. This phenomenon can be explained that thin film of asphalt wrapped in the aggregate surface makes the aggregate surface in the closed states. When RAP and mineral aggregate have equal volume, the density of RAP is lower than mineral aggregate. That is to say the compacted dry density of RAP is lower, for the effect by asphalt thin film.

Advanced Characterization of Asphalt and Concrete Materials GSP 255 © ASCE 2014

7-Day unconfined compressive strength The specimens prepared for UCS testing were compacted in a steel mold. Following compaction, the UCS specimens were then extruded from the mold. After extrusion, all specimens were placed in a moisture curing room, where they were subjected to more than 95 percent relative humidity for a 7-day curing period. The 7-day unconfined compressive strength value of 2.068 to 2.758 Mpa is recommended by Portland Cement Association. Figure 4 represents the drawing of UCS sample mean.

Figure 3 Dosage of RAP Effect on the Optimum Water Content and the Maximum Dry Density

Figure 4 Interactions between RAP Content and Cement Content for UCS

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Advanced Characterization of Asphalt and Concrete Materials GSP 255 © ASCE 2014

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The experiment results show that 7-day UCS have strong correlation with cement and RAP content. When cement content was less than 1.5%, 7-day UCS could not meet the specification requirements. When RAP proportion is more than 75%, it needs to increase cement content to make up for the lack of strength. Based on our field experience, we found that with increasing cement content, temperature and dry shrinkage cracks are also increased. As explained in the specification, UCS is an important design criterion as sufficient cement should be added to obtain a desirable UCS. The results of UCS testing conducted in this research are displayed in Table 4. An ANOVA was performed on the data to investigate the significance of each factor on the measured UCS value. Being less than the standard error rate of 0.05, the p-values shown in the Table 5 indicate that RAP proportion, cement content, and the interaction between RAP content and cement content were all significant. The effects of RAP and cement content on UCS are presented in Table 6, which shows that increasing RAP proportion lead to lower UCS values while increasing cement contents lead to higher UCS values. Table 4 Unconfined Compressive Strength Data Cement dosage/%

0.5

1.0

1.5

2.0

2.5

Specimens Number O1 O2 O3

RAP Proportion/ % 0 25 50 75 100 7-day Unconfined compressive strength /Mpa 0.462 0.641 0.552 0.337 0.290 0.393 0.538 0.593 0.401 0.310 0.393 0.648 0.538 0.384 0.317

Oi

0.416

0.609

0.561

0.374

0.36

T1 T2 T3

0.607 1.131 0.951

0.979 1.200 1.213

1.317 1.303 1.509

0.997 0.871 1.032

0.813 0.848 0.807

Ti

0.896

1.131

1.376

0.967

0.823

H1 H2 H3

2.626 3.309 3.220

2.434 3.199 3.185

2.482 2.634 2.434

2.375 2.199 2.286

1.661 1.799 1.558

Hi

3.052

2.939

2.517

2.287

1.673

F1 F2 F3

4.606 4.661 4.302

3.765 4.054 4.019

3.261 3.132 2.921

2.476 2.683 2.624

1.737 2.165 2.158

Fi

4.523

3.946

3.104

2.594

2.020

I1 I2 I3

4.908 5.185 5.357

4.733 4.502 3.971

3.482 3.820 3.454

3.187 3.562 3.254

2.109 2.482 2.434

Ii

5.150

4.402

3.585

3.334

2.342

Advanced Characterization of Asphalt and Concrete Materials GSP 255 © ASCE 2014

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Table 5 Variance analysis for two-factor factorial analysis Source

Type III Sum

df

Mean Square

F

Sig.

of Squares Model

546.773a

25

21.871

408.582

.000

Cement content

131.173

4

32.793

612.627

.000

RAP content

20.352

4

5.088

95.051

.000

C. C. * RAP C.

15.376

16

.961

17.953

.000

Error

2.676

50

.054

Total

549.449

75

a. R Squared = .995 (Adjusted R Squared = .993)

Table 6 Simple Effect for Factor A and Factor B Response Variable UCS/Mpa

0 2.807

RAP Proportion % 25 50 75

100

0.5

2.639

1.433

0.464

2.229

1.911

Cement Content % 1.0 1.5 2.0 1.039

2.493

3.237

2.5 3.763

In our previous experience, cold mix recycling with cement was first mixed in the plant and then brought to job site for placement. For example, the recycling base of Hua Gong Road was constructed in 2006. The RAP proportion was 55% and cement blending content was 2%. The maximum dry density was 2.184g/cm3, and optimum moisture content was 5.7%. FINDINGS & RECOMMENDATIONS Based on the results presented above, RAP proportion and cement content have significantly impact on UCS values. SPSS software was very helpful on data analyses. Test results indicated that the optimum design should include 50 to 75% of RAP and 1.5 to 2.5% of cement.

References [1] Mattherm Brent Roper. Evaluation of Laboratory Durability Tests for Stabilized Aggregate Base Materials [D]. Idaho: Department of Civil and Environmental Engineering Brigham Young University. August 2007 [2] Ashley Vannoy Brown. Cement Stabilization of Aggregate Base Material Blended with Reclaimed Asphalt Pavement [D]. Idaho: Department of Civil and Environmental Engineering Brigham Young University. August 2006 [3] David R. Luhr, Wayne S. Adaska, Gregory E. Halsted. Guide to Full-Depth Reclamation(FDR) with Cement [M]. U.S. Washington: Portland Cement Association. 2008

Advanced Characterization of Asphalt and Concrete Materials GSP 255 © ASCE 2014 [4] Gregory E. Halsted. Using Cement to Reclaim Asphalt Pavements [C]. Canada Saskatchewan: Paper Prepared for Presentation at the Preserving Low-Volume Road Investments Session of 2007 Annual Conference of the Transportation Association of Canada Saskatoon, Saskatchewan, 2007 [5] Ma Jun-yi. Research on the Application of Reclaimed Asphalt Pavement in Base Course [D]. Xi An China: Chang’an University. 2005 [6] Zeng Meng-lan, Xiao Jie, Wu Chao-fan. Effects of RAP Content on Performance of Cold Reclaimed Asphalt Mixture [J]. Chang Sha China: Central south highway engineering. 2007.4(32) P: 27 [7] Wu Jian-min, Hao He-rui, Ma Jun-yi. The Depth Determining of Asphalt Pavement Cold Regeneration [J]. Bei Jing Chian: Communications Standardization. 2007.10 P:112 [8] Department of Transportation, JTG F40-2004. Technical Specifications for Construction of Highway Asphalt Pavements [S]. Bei Jing China: China Communications Press, 2004

[9] Department of Transportation, JTG E51-2009 Test Methods of Materials Stabilized with Inorganic Binders for Highway Engineering [S]. Bei Jing China: China Communications Press, 2009

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