Effect of asphalt content on fatigue limit for asphalt mixture
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摘要: 利用马歇尔试验确定了沥青混合料的最佳沥青含量, 采用控制应变的小梁疲劳试验, 研究了最佳沥青含量和富沥青含量混合料弯拉劲度模量随应变水平的变化规律, 得到了应变水平与荷载作用次数模型, 并分析了2种混合料在不同应变水平和轴次下的疲劳特性。分析结果表明: 不同应变水平下, 2种混合料弯拉劲度模量随荷载作用次数变化规律基本一致, 高应变水平下弯拉劲度模量迅速衰减, 低应变水平下初始阶段模量明显降低, 随后趋于平缓; 以弯拉劲度模量降为初始值的一半作为破坏标准, 2种混合料疲劳寿命和应变的关系都呈非线性特征, 且低应变水平下曲线呈现典型的渐近线趋势, 表明2种沥青混合料具有类似的疲劳极限特性; 富沥青含量混合料在高应变水平下对疲劳极限特性影响有限, 只有当应变水平小于100με时才对疲劳寿命有明显改善; 在进行永久性沥青路面沥青层设计时, 不能简单通过增加沥青含量减薄沥青层厚度。Abstract: The optimum asphalt contents of asphalt mixtures were determined by using Marshell test.The fatigue performance change rules of asphalt concretes with different asphalt contents with strain levels were studied by controlled-strain beam fatigue test.The relationship model between strain level and load cycles was built.The fatigue characters of optimal asphalt content mixture and rich asphalt content mixture under different strain levels and load cycles were analyzed.The result shows that for different strain levels, the asphalt mixture flexural stiffness moduli of the two mixtures have the same rule, which reduce quickly with a sharp increase of load cycles during high strain level and tend to reduce slowly with lower strain level.The relationships of fatigue life and strain for the two mixtures are nonlinear, and low-strain curves show a typical feature of asymptote.So the two different asphalt mixtures all have the similar characteristics of fatigue limit.Rich asphalt content has little effect on the fatigue limit at high strain, and it can markedly improve the fatigue life only when strain level is lower than 100 με.Thus simply increasing asphalt content can not mean to thin the thickness of asphalt course during designing perpetual asphalt pavement.
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Key words:
- pavement material /
- asphalt mixture /
- fatigue limit /
- asphalt content
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表 1 集料指标
Table 1. Indices of aggregate
指标 实测结果 规范要求 压碎值/% 18 ≤28 磨耗值/% 22 ≤30 对沥青的粘附性 4级 ≥4级 针片状含量/% 大于9.5 mm 8 ≤15 小于9.5 mm 10 ≤20 吸水率/% 1.0% ≤3.0 细集料含泥量/% 0.7% ≤3.0 细集料砂当量/% 69 ≥60 表 2 沥青指标
Table 2. Indices of asphalt
指标 试验结果 针入度(25 ℃, 100 g, 5 s)/0.1mm 92 针入度指数 -0.69 延度(10 ℃)/cm > 100 软化点(环球法)/℃ 47 闪点/℃ > 250 密度(15 ℃)/(g·cm-3) 0.982 旋转薄膜加热试验RTFOT(165 ℃, 85 min) 残留针入度比(25 ℃)/% 72.3 残留延度(10 ℃)/cm 7.5 质量损失/% -0.02 表 3 混合料级配组成
Table 3. Gradations of mixtures
筛孔尺寸/mm 31.5 26.5 19 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 规范通过率/% 100 90~100 75~90 65~83 57~76 45~65 24~52 16~42 12~33 8~24 5~17 4~13 3~7 试验级配通过率/% 100.0 95.0 84.0 76.0 66.0 56.0 37.5 25.5 17.0 12.0 9.5 6.5 5.0 表 4 最佳沥青含量下S和N的拟合结果
Table 4. Fitting result of S and N under optimal asphalt content
应变水平/με a b c 均方差 残差平方和 判定系数R2/% 800 3 642 -331.05 0.170 3 9.97 162 988 99 3 076 -144.07 0.225 3 9.95 162 525 99 3 577 -387.02 0.158 9 7.06 81 841 99 400 3 714 -213.00 0.176 4 65.93 7 086 157 97 3 559 -180.71 0.188 8 63.45 6 663 221 98 3 090 -11.53 0.378 3 48.25 3 022 184 99 200 3 198 -1.56 0.452 7 31.65 1 502 267 98 3 165 -2.70 0.421 1 43.28 2 867 319 98 3 143 -1.12 0.489 6 31.79 1 518 038 99 100 3 442 -11.26 0.262 9 48.01 3 528 943 85 3 328 -8.43 0.281 0 52.39 4 201 809 83 3 480 -7.92 0.288 1 49.75 3 789 581 85 70 3 597 -19.35 0.229 4 34.25 2 143 048 92 3 814 -59.33 0.173 6 33.43 2 041 616 95 3 727 -53.24 0.177 1 28.86 1 521 957 96 表 5 富沥青含量下S和N的拟合结果
Table 5. Fitting result of S and N under rich asphalt content
应变水平/με a b c 均方差 残差平方和 判定系数R2/% 800 3 475 -432.15 0.147 3 29.98 1 534 098 99 3 218 -273.63 0.179 9 27.30 1 192 106 99 3 294 -270.95 0.180 6 27.08 1 196 027 99 400 2 647 -0.77 0.533 7 36.66 2 413 120 98 2 603 -0.88 0.519 7 23.39 967 102 99 2 614 -1.05 0.505 2 21.93 835 398 99 200 3 194 -14.55 0.297 5 50.02 3 830 244 96 3 145 -52.72 0.213 9 86.20 11 376 001 90 3 210 -48.66 0.219 7 85.18 11 108 863 90 100 3 250 -8.51 0.268 9 48.00 3 527 407 80 3 288 -11.69 0.253 7 49.86 3 806 061 82 3 232 -5.90 0.282 3 49.86 3 806 549 73 70 3 474 -16.52 0.220 6 32.25 1 592 341 88 3 504 -16.31 0.227 3 29.68 1 348 871 91 3 482 -12.77 0.235 2 32.46 1 613 408 88 表 6 不同应变水平对应的疲劳寿命
Table 6. Fatigue lives under different strain levels
疲劳寿命/108次 混合料类型 应变水平/με 1 000 800 600 400 300 200 100 50 10 最佳沥青含量混合料 0.000 1 0.000 3 0.001 2 0.008 0 0.031 5 0.217 4 5.898 8 160.043 340 930 富沥青含量混合料 0.000 1 0.000 4 0.001 5 0.010 3 0.040 5 0.279 1 7.571 6 205.431 437 617 表 7 不同轴次对应的疲劳极限
Table 7. Fatigue limits under different axis
疲劳极限/με 混合料类型 当量轴次/108 0.01 0.05 0.10 0.50 1.00 5.00 10.00 50.00 100.00 最佳沥青含量混合料 381.8 272.3 235.4 167.9 145.2 103.5 89.5 63.8 55.2 富沥青含量混合料 402.4 287.0 248.1 176.9 153.0 109.1 94.3 67.3 58.2 -
[1] NUNN ME, BROWN A, WESTON D, et al. Design of long life flexible pavements for heavy traffic[R]. Berkshire: Transport Research Laboratory, 1997. [2] NEWCOMB D E, BUNCHER M B, HUDDLESON I J. Concepts of perpetual pavements[C]∥TRB. Perpetual Bitu-minous Pavements. Washington DC: TRB, 2001: 4-11. [3] Asphalt Pavement Alliance. Perpetual pavements: a synthesis[R]. Maryland: Asphalt Pavement Alliance, 2002. [4] 崔鹏, 邵敏华, 孙立军. 长寿命沥青路面设计指标研究[J]. 交通运输工程学报, 2008, 8(3): 37-42. http://transport.chd.edu.cn/article/id/200803009CUI Peng, SHAO Min-hua, SUNLi-jun. Research on design indices of perpetual asphalt pavement[J]. Journal of Traffic and Transportation Engineering, 2008, 8(3): 37-42. (in Chinese) http://transport.chd.edu.cn/article/id/200803009 [5] 郑木莲, 王松根, 陈拴发, 等. 耐久性沥青路面混凝土基层荷载应力的数值计算[J]. 中国公路学报, 2008, 21(2): 28-33. https://www.cnki.com.cn/Article/CJFDTOTAL-ZGGL200802005.htmZHENG Mu-lian, WANG Song-gen, CHEN Shuan-fa. Load stress numerical calculation for concrete base of durable asphalt pavement[J]. China Journal of Highway and Transport, 2008, 21(2): 28-33. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-ZGGL200802005.htm [6] 张志祥, 陈荣生, 白琦峰. LSM沥青混合料疲劳极限的试验研究[J]. 公路交通科技, 2006, 23(4): 19-24. https://www.cnki.com.cn/Article/CJFDTOTAL-GLJK200604004.htmZHANG Zhi-xiang, CHEN Rong-sheng, BAI Qi-feng. Test study on fatigue limit of LSMasphalt mixture[J]. Journal of Highway and Transportation Research and Development, 2006, 23(4): 19-24. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-GLJK200604004.htm [7] 董忠红, 吕彭民. 移动荷载下倒装结构沥青路面动力响应[J]. 长安大学学报: 自然科学版, 2008, 28(5): 111-115. https://www.cnki.com.cn/Article/CJFDTOTAL-XAGL200805027.htmDONG Zhong-hong, LU Peng-min. Dynamic response of inverse structure asphalt pavement under moving load[J]. Journal of Chang an University: Natural Science Edition, 2008, 28(5): 111-115. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-XAGL200805027.htm [8] MONISMITH C L, EPPS J A, KASI ANCHUK D A. Asphalt mixture behavior in repeated flexure[R]. Berkeley: University of California, 1968. [9] CARPENTER S H, GHUZLAN K A, SHEN Shi-hui. Fatigue endurance limit for highway and airport pavements[J]. Transportation Research Record, 2003(1832): 131-138. [10] THOMPSON M R, CARPENTER S H. Design principles for long lasting HMA pavements[C]∥International Society for Asphalt Pavements. International Conference on Design and Construction of Long Lasting Asphalt Pavements. Auburn: ISAP, 2004: 365-384. [11] PETERSON R L, TURNER P, ANDERSON M, et al. Determination of threshold strain level for fatigue endurance limit in asphalt mixtures[C]∥International Society for Asphalt Pavements. International Conference on Design and Construction of Long Lasting Asphalt Pavements. Auburn: ISAP, 2004: 385-398. [12] PRIEST A L, TI MM D H. Methodology and calibration of fatigue transfer functions for mechanistic-empirical flexible pavement design[R]. Auburn: Auburn University, 2006. [13] AASHTO T321—03, standard method of test for determin-ing the fatigue life of compacted hot-mix asphalt(HMA)subjected to repeated flexural bending[S]. [14] TAYEBALI A A, DEACON J A, COPLANTZ J S, et al. Fatigue response of asphalt-aggregate mixes[R]. Berkeley: University of California, 1994. [15] ROWE G M, BOULDI N M G. Improved techniques to evaluate the fatigue resistance of asphaltic mixtures[C]∥EAPA. Proceedings of2nd Eurasphalt and Eurobitume Congress. Barcelona: EAPA, 2000: 754-763. -