Effect of water/cement ratio and silica fume addition on the fracture toughness and morphology of fractured surfaces of gravel concretes
Effect of water/cement ratio and silica fume addition on the fracture toughness and morphology of fractured surfaces of gravel concretes
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DOI：
10.1016/s0008-8846(00)00332-x
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发表时间：
2000-09
影响因子：
11.4
通讯作者：
G. Prokopski;B. Langier
中科院分区：
文献类型：
--
作者：
G. Prokopski;B. Langier
由天然砾石骨料制成的混凝土的断裂韧性调查的结果进行了讨论，与不同的水/水泥比（W/C=0.33，0.43，0.53和0.63），没有硅灰和硅灰添加。确定了应力强度因子KIcS和裂纹尖端张开位移CTODc的临界值。同时，对断裂韧性试验中得到的混凝土试件断口的表面粗糙度参数RL和分形维数D进行了检验。最大值的应力强度因子，KIcS，表现出最低的水/水泥比，W/C=0.33（有和没有硅灰添加）的混凝土。这是由于在微观结构检查中观察到的骨料-水泥浆体过渡区的孔隙率相当低造成的，在这种情况下，骨料-水泥浆体过渡区的结构紧凑，具有少量的结构缺陷。裂纹，在达到临界力PQ，贯穿粗骨料颗粒，所获得的骨折是平坦的性质。所检查的断裂形态参数，即，剖面线发育程度RL和分形维数D在这些裂缝中达到最小值。随着水灰比的增加，骨料-水泥浆体过渡区的结构孔隙率增加，裂纹扩展加快，应力强度因子KIcS值降低。在这种情况下，裂纹传播避免粗砾石颗粒（形成粗粒断裂），这导致断裂表面粗糙度增加，并导致断裂表面形态的两个检查参数R和D的值上升。
The results of the fracture toughness investigations for concretes made from natural gravel aggregate, with diverse water/cement ratio (W/C=0.33, 0.43, 0.53 and 0.63), without silica fume and with a silica fume addition are discussed. The critical values of the stress intensity factor, KIcS, as well as, the critical values of crack tip opening displacement, CTODcwere determined. Also, the examination results for profile roughness parameter, RL, and fractal dimension, D, of concrete specimen fractures obtained in fracture toughness tests were performed. The largest values of the stress intensity factor, KIcS, were showed by concretes with the lowest water/cement ratio, W/C=0.33 (both with and without silica fume addition). This was caused by considerably lower porosity of the aggregate–cement paste transition zone as observed in microstructural examinations, which had in this case a compact structure with a small number of structural defects. Cracks, upon reaching the critical force PQ, ran through the coarse aggregate grains, and the obtained fractures were flat in character. The examined parameters of fracture morphology, i.e., the profile line development degree, RL, and the fractal dimension, D, reached the smallest values for those fractures. As the water/cement ratio increased, an increase in the structural porosity of the aggregate–cement paste transition zone occurred, which caused a promoted propagation of cracks and resulted in the obtaining of lower values of stress intensity factor, KIcS. Cracks in this case propagated avoiding coarse gravel grains (an overgrain fracture formed), which resulted in increased fracture surface roughness and in a rise of the values of both examined parameters of fracture surface morphology, RLand D.