Effect of coarse aggregate size on the dynamic compression behavior of concrete
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摘要: 粗骨料作为混凝土材料组成最主要的部分,对混凝土力学性能和破坏模式有着很重要的影响。为了研究粗骨料平均粒径对混凝土动态力学性能的影响规律,针对不同平均粗骨料平均粒径(6、12、24 mm)的混凝土和砂浆材料进行了一系列SHPB试验,得到了不同应变率下各试件的应力-应变曲线,并对每种材料的动态增长因子(dynamic increase factor,DIF)与应变率的对数进行了线性拟合。结果表明:砂浆和混凝土材料的抗压强度具有明显的应变率效应,其动态抗压强度随着应变率的增加而逐渐增大,应力-应变曲线呈现相似的变化趋势;在相同的动态应变率条件下,平均粗骨料粒径为12 mm的混凝土的动态抗压强度最大,这与准静态条件下砂浆抗压强度最大截然不同;不同粗骨料粒径混凝土材料的应变率强化系数均大于砂浆材料,且随着粗骨料无量纲尺寸的增大,混凝土材料的应变率强化因子呈现先增大后减小的趋势。Abstract: As the most important part of concrete material, coarse aggregate has a very important influence on the mechanical properties and failure mode of concrete. In order to study the effect of the coarse aggregate average size on the dynamic mechanical properties of concrete, a series of SHPB experiments were carried out for concrete and mortar materials with different average particle sizes (6 mm, 12 mm and 24 mm) of coarse aggregate. A dual-pulse shaper was used in the tests for dynamic stress equilibrium and constant strain rate loading. Moreover, the dynamic stress equilibrium in the test specimen was checked, and it is considered that the test data are valid when the dynamic imbalance factor is less than 5%. The stress-strain curves of the specimens under different strain rates were obtained, and the dynamic increase factor (DIF) of each material was linearly fitted with the logarithm of the strain rate. The results indicate that the compressive strength of the mortar and the concrete has an obvious strain rate effect, the dynamic compressive strength increases gradually with the strain rate, and the stress-strain curves show a similar trend. Under the same dynamic strain rate condition, the dynamic compressive strength of the concrete with an average coarse aggregate size of 12 mm is the highest, which is quite different from the maximum compressive strength of the mortar under quasi-static conditions. The CEB and other models are inapplicable to the relationship between the DIF and the strain rate because they do not consider the effect of the coarse aggregate size found in this study. Therefore, the specimen’s dynamic DIF and the logarithm of strain rate are fitted by Bischoff's model in the paper. The strain rate strengthening coefficient of concretes with different coarse aggregate sizes is larger than that of the mortar. With the increase of the coarse aggregate dimensionless size, the strain rate strengthening factor of the concrete increases at first and then decreases.
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表 1 不同材料试样的配比
Table 1. Mix proportion of different grades of mortar and concrete
试件 w(水泥)/(kg·m−3) w(砂子)/(kg·m−3) w(粗骨料)/(kg·m−3) w(矿粉)(kg·m−3) w(水)/(kg·m−3) w(减水剂)/(kg·m−3) M60 714 1000 22 223 2.22 C60 547 767 897 17 171 1.70 表 2 SHPB装置中部件的主要参数
Table 2. Specifications of the SHPB experimental system
部件 材质 几何参数 物理参数 直径/mm 长度/mm ${E_{\text{b}}}$/GPa ${\rho _{\text{b}}}$/(g·cm−3) ${\nu _{\text{b}}}$ $ {c_{\text{b}}} $/(m·s−1) 撞击杆 40Cr钢 80 500/1000 210 7.85 0.22 5210 入射杆 40Cr钢 80 6000 210 7.85 0.22 5210 透射杆 40Cr钢 80 4000 210 7.85 0.22 5210 表 3 不同试样的动态增长因子在公式中的拟合结果
Table 3. Fitting results of dynamic increace factors of different samples in the formula
试样 A $ {\dot \varepsilon _{\text{s}}} $/s-1 R2 M60 0.94 30 0.998 C60-G6 1.45 30 0.996 C60-G12 2.13 30 0.995 C60-G24 1.08 30 0.996 -
[1] LI Q M, MENG H. About the dynamic strength enhancement of concrete-like materials in a split Hopkinson pressure bar test [J]. International Journal of Solids and Structures, 2003, 40(2): 343–360. DOI: 10.1016/S0020-7683(02)00526-7. [2] KOLSKY H. An investigation of the mechanical properties of materials at very high rates of loading [J]. Proceedings of the Physical Society B, 1949, 62(11): 676–700. DOI: 10.1088/0370-1301/62/11/302. [3] CHEN B, LIU J. Effect of aggregate on the fracture behavior of high strength concrete [J]. Construction and Building Materials, 2004, 18(8): 585–590. DOI: 10.1016/j.conbuildmat.2004.04.013. [4] CADONI E, LABIBES K, ALBERTINI C. Strain-rate effect on the tensile behaviour of concrete at different relative humidity levels [J]. Materials and Structures, 2001, 34(235): 21–26. DOI: 10.1007/BF02482196. [5] ALBERTINI C, CADONI E, LABIBES K. Study of the mechanical properties of plain concrete under dynamic loading [J]. Experimental Mechanics, 1999, 39(2): 137–141. DOI: 10.1007/BF02331117. [6] ALBERTINI C, MONTAGNANI M. Study of the true tensile stress-strain diagram of plain concrete with real size aggregate; need for and design of a large Hopkinson bar bundle [J]. Le Journal de Physique IV, 1994, 04(C8): 113–118. DOI: 10.1051/jp4:1994817. [7] MUCIACCIA G, ROSATI G, DI LUZIO G. Compressive failure and size effect in plain concrete cylindrical specimens [J]. Construction and Building Materials, 2017, 137: 185–194. DOI: 10.1016/j.conbuildmat.2017.01.057. [8] WALLIN K. A simple fracture mechanical interpretation of size effects in concrete fracture toughness tests [J]. Engineering Fracture Mechanics, 2013, 99(1): 18–29. DOI: 10.1016/j.engfracmech.2013.01.018. [9] UDDIN M T, MAHMOOD A H, KAMAL M R I, et al. Effects of maximum size of brick aggregate on properties of concrete [J]. Construction and Building Materials, 2017, 134: 713–726. DOI: 10.1016/j.conbuildmat.2016.12.164. [10] SIM J, YANG K, JEON J. Influence of aggregate size on the compressive size effect according to different concrete types [J]. Construction and Building Materials, 2013, 44(7): 716–725. DOI: 10.1016/j.conbuildmat.2013.03.066. [11] GRASSL P, GRÉGOIRE D, ROJAS SOLANO L, et al. Meso-scale modelling of the size effect on the fracture process zone of concrete [J]. International Journal of Solids and Structures, 2012, 49(13): 1818–1827. DOI: 10.1016/j.ijsolstr.2012.03.023. [12] HAO Y, HAO H, JIANG G P, et al. Experimental confirmation of some factors influencing dynamic concrete compressive strengths in high-speed impact tests [J]. Cement and Concrete Research, 2013, 52: 63–70. DOI: 10.1016/j.cemconres.2013.05.008. [13] KIM K, LEE S, CHO J. Effect of maximum coarse aggregate size on dynamic compressive strength of high-strength concrete [J]. International Journal of Impact Engineering, 2019, 125: 107–116. DOI: 10.1016/j.ijimpeng.2018.11.003. [14] LI M, HAO H, SHI Y, et al. Specimen shape and size effects on the concrete compressive strength under static and dynamic tests [J]. Construction and Building Materials, 2018, 161: 84–93. DOI: 10.1016/j.conbuildmat.2017.11.069. [15] GROTE D L, PARK S W, ZHOU M. Dynamic behavior of concrete at high strain rates and pressures: I. experimental characterization [J]. International Journal of Impact Engineering, 2001, 25(9): 869–886. DOI: 10.1016/S0734-743X(01)00020-3. [16] ZHOU X Q, HAO H. Modelling of compressive behaviour of concrete-like materials at high strain rate [J]. International Journal of Solids and Structures, 2008, 45(17): 4648–4661. DOI: 10.1016/j.ijsolstr.2008.04.002. [17] TEDESCO J W, POWELL J C, ROSS C A, et al. A strain-rate-dependent concrete material model for ADINA [J]. Computers and Structures, 1997, 64(5): 1053–1067. DOI: 10.1016/S0045-7949(97)00018-7. [18] ROSS C A. Split-Hopkinson pressure-bar tests on concrete and mortar in tension and compression [J]. ACI Materials Journal, 1989, 86(5): 475–481. DOI: 10.14359/2065. [19] COMMITTEE CEB. Fib model code for concrete structures[M]. UK: Trowbridge, Wiltshire, 2013. [20] BISCHOFF P, PERRY S. Compressive behaviour of concrete at high strain rates [J]. Materials and Structures, 1991, 24(6): 425–450. DOI: 10.1007/BF02472016. [21] 高光发, 郭扬波. 高强混凝土动态压缩试验分析 [J]. 爆炸与冲击, 2019, 39(3): 63–72. DOI: 10.11883/bzycj-2017-0405.GAO G F, GUO Y B. Analysis of the dynamic compressive test of high strength concrete [J]. Explosion and Shock Waves, 2019, 39(3): 63–72. DOI: 10.11883/bzycj-2017-0405. [22] 高光发. 混凝土材料动态拉伸强度的应变率强化规律 [J]. 高压物理学报, 2017, 31(5): 593–602. DOI: 10.11858/gywlxb.2017.05.013.GAO G F. Hardening effect of the strain rate on the dynamic tensile strength of the plain concrete [J]. Chinese Journal of High Pressure Physics, 2017, 31(5): 593–602. DOI: 10.11858/gywlxb.2017.05.013. [23] 高光发. 混凝土材料动态压缩强度的应变率强化规律 [J]. 高压物理学报, 2017, 31(3): 261–270. DOI: 10.11858/gywlxb.2017.03.007.GAO G F. Effect of strain-rate hardening on dynamic compressive strength of plain concrete [J]. Chinese Journal of High Pressure Physics, 2017, 31(3): 261–270. DOI: 10.11858/gywlxb.2017.03.007. [24] GUO Y B, GAO G F, JING L, et al. Response of high-strength concrete to dynamic compressive loading [J]. International Journal of Impact Engineering, 2017, 108: 114–135. DOI: 10.1016/j.ijimpeng.2017.04.015. [25] FLORES-JOHNSON E A, LI Q M. Structural effects on compressive strength enhancement of concrete-like materials in a split Hopkinson pressure bar test [J]. International Journal of Impact Engineering, 2017, 109: 408–418. DOI: 10.1016/j.ijimpeng.2017.08.003. [26] LU Y B, LI Q M. Appraisal of pulse-shaping technique in split Hopkinson pressure bar tests for brittle materials [J]. International Journal of Protective Structures, 2010, 1(3): 363–390. DOI: 10.1260/2041-4196.1.3.363. [27] HAO H, HAO Y, LI J, et al. Review of the current practices in blast-resistant analysis and design of concrete structures [J]. Advances in Structural Engineering, 2016, 19(8): 1193–1223. DOI: 10.1177/1369433216656430. [28] COTSOVOS D M, PAVLOVIĆ M N. Numerical investigation of concrete subjected to compressive impact loading: Part 1: a fundamental explanation for the apparent strength gain at high loading rates [J]. Computers and Structures, 2008, 86(1−2): 145–163. DOI: 10.1016/j.compstruc.2007.05.014. [29] MA H, YUE C, YU H, et al. Experimental study and numerical simulation of impact compression mechanical properties of high strength coral aggregate seawater concrete [J]. International Journal of Impact Engineering, 2020, 137: 103466. DOI: 10.1016/j.ijimpeng.2019.103466. [30] HARTMANN T, PIETZSCH A, GEBBEKEN N. A hydrocode material model for concrete [J]. International Journal of Protective Structures, 2010, 1(4): 443–468. DOI: 10.1260/2041-4196.1.4.443. [31] LEE S, KIM K, PARK J, et al. Pure rate effect on the concrete compressive strength in the split Hopkinson pressure bar test [J]. International Journal of Impact Engineering, 2018, 113: 191–202. DOI: 10.1016/j.ijimpeng.2017.11.015. [32] AL-SALLOUM Y, ALMUSALLAM T, IBRAHIM S M, et al. Rate dependent behavior and modeling of concrete based on SHPB experiments [J]. Cement and Concrete Composites, 2015, 55: 34–44. DOI: 10.1016/j.cemconcomp.2014.07.011. [33] 金浏, 杨旺贤, 余文轩, 等. 骨料粒径对混凝土动态拉伸强度及尺寸效应影响分析 [J]. 振动与冲击, 2020, 39(9): 24–34. DOI: 10.13465/j.cnki.jvs.2020.09.004.JIN L, YANG W, YU W, et al. Influence of aggregate size on the dynamic tensile strength and size effect of concrete [J]. Journal of Vibration and Shock, 2020, 39(9): 24–34. DOI: 10.13465/j.cnki.jvs.2020.09.004.