Mechanism of rubber particles inhibit heat damage of steam-curing concrete
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摘要: 通过向蒸养混凝土中掺入橡胶颗粒制备蒸养橡胶混凝土来抑制蒸养过程中混凝土产生的热损伤。通过试验测试了蒸养橡胶混凝土的抗压强度;建立了考虑界面过渡区的橡胶混凝土随机骨料模型,基于ABAQUS,模拟研究了橡胶颗粒对降温阶段混凝土温度损伤应力的影响,从细观角度研究橡胶颗粒抑制蒸养混凝土中微裂纹发展规律,并将温度损伤应力作为初始缺陷,模拟了橡胶混凝土的抗压性能,验证了模拟结果的可靠性;通过压汞(Mercury intrusion porosimetry,MIP)测试研究了橡胶颗粒对蒸养混凝土孔结构的影响;通过超景深显微镜研究了橡胶与水泥石之间的结合情况。研究结果表明:橡胶颗粒掺入可以抑制蒸养混凝土的热损伤,减少强度损失。橡胶颗粒可以有效降低蒸养混凝土试件的总孔隙率,蒸养橡胶混凝土试件有害孔径较未掺加橡胶颗粒的普通蒸养混凝土下降了3.1%,同时改善了橡胶和水泥基体的粘结状况。Abstract: The heat damage of steam-curing concrete was restrained by adding rubber particles into steam-curing concrete to prepare steam-curing rubber concrete. The compressive strength of steam-curing rubber concrete was tested through experiments. A random aggregate model of rubber concrete considering interface transition zone was established based on ABAQUS simulation. The influence of rubber particles on the temperature damage stress of concrete in the cooling stage was studied. The influence of rubber particles on the temperature damage stress of concrete at the cooling stage was studied. The development of microcracks in steam-curing concrete inhibited by rubber particles was studied from a microscopical point of view, and taking the temperature damage stress as the initial defect, the compressive property of rubber concrete was studied, and the reliability of the simulation results was verified. The effect of rubber particles on the pore structure of steam-curing concrete was studied by mercury intrusion porosimetry (MIP) test. The bond between rubber and cement was studied by an ultra-depth-of-field microscope. The results show that the addition of rubber particles can restrain heat damage and reduce the strength loss of steam-curing concrete. Rubber particles can effectively reduce the total porosity of steam-curing concrete specimens, and the harmful pore size of steam-curing rubber concrete decreases by 3.1% compared with that ordi-nary steam-curing concrete without adding rubber particles. Meanwhile, the bond between rubber and cement matrix is improved.
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表 1 水泥的化学成分
Table 1. Chemical compositions of cement
wt% SiO2 Al2O3 Fe2O3 CaO MgO SO3 17.07 5.32 3.26 66.52 2.99 2.91 表 2 橡胶粉化学成分
Table 2. Chemical ingredients of crumb rubber
wt% Rubber hydrocarbon Carbon black Acetone extract Isoprene Water Ash content Fiber content Metal content Others 45.2 25.8 14.2 12.1 0.8 0.9 0.5 0.08 0.42 表 3 混凝土配合比设计
Table 3. Mix proportions of concretes
kg/m3 Specimen Cement Stone Water Sand Rubber RC0 520 810 195 835 0 RC35 520 810 195 747 35 RC70 520 810 195 696 70 RC105 520 810 195 571 105 表 4 不同养护制度不同橡胶掺量的混凝土抗压强度
Table 4. Compressive strength of concrete with different curing systems and different rubber contents
MPa Specimen Curing regime Standard-curing Steam-curing RC0 60.2 57.2 RC35 44.0 45.0 RC70 38.3 41.6 RC105 34.6 29.6 表 5 材料参数
Table 5. Material parameters
Material Elastic modulus/MPa Poisson's ratio Coarse aggregate 80000 0.20 Rubber 70 0.49 表 6 水灰比为0.375时公式计算砂浆的材料参数
Table 6. Formula calculates the material parameters of mortar when the water-cement ratio is 0.375
Water-cement ratio Elastic modulus/MPa Poisson's ratio Compressive strength/MPa Tensile strength/MPa 0.375 24000 0.2 46.1 3.7 表 7 不同养护制度和橡胶掺量的混凝土模拟结果与实验结果对比
Table 7. Simulation results of concrete with different curing systems and rubber contents compared with the experimental results
Specimen Rubber content/(kg·m−3) Compressive strength/MPa Relative error/% Experimental value Simulation value RC0-1 0 60.2 57.7 4.15 RC35-1 35 44.0 40.8 7.30 RC70-1 70 38.3 41.2 7.01 RC105-1 105 34.6 33.9 2.02 RC0-2 0 57.2 56.5 1.28 RC35-2 35 45.0 40.4 10.00 RC70-2 70 41.6 39.8 4.25 RC105-2 105 29.6 33.5 11.54 Notes: RC0-1 represents the standard-curing for group RC0 specimens; RC0-2 represents the steam-curing for group RC0 specimens. 表 8 不同橡胶掺量的混凝土损伤单元的比例
Table 8. Proportion of damaged elements of concrete with different rubber contents
% Specimen Curing regime Standard-curing Steam-curing RC0 49.79 53.05 RC35 45.62 45.26 RC70 45.21 45.90 RC105 50.58 52.42 表 9 RM70的孔隙率和中值孔径
Table 9. Porosity and median pore size of RM70
Rubber content/(kg·m−3) Porosity/% Median pore diameter/nm Standard-curing Steam-curing Standard-curing Steam-curing 70 12.56 11.66 560.87 283 -
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