路面水泥混凝土的早期塑性开裂性能

Plastic Shrinkage Cracking Behavior of Pavement Cement Concrete at Early Age

针对目前路面水泥混凝土易于出现塑性开裂的情况,为更合理优化路面混凝土原材料与配合比设计参数,采用笠井芳夫教授提出的大板法,对比研究了水泥细度、矿物掺和料种类及掺量、混凝土配合比设计参数对路面混凝土早期塑性开裂性能的影响。试验结果表明,水泥的比表面积越大,矿物掺和料掺量越高,水灰比越小,混凝土浆集比越大时,越不利于路面水泥混凝土的塑性开裂控制。且相对于粉煤灰与矿粉,硅灰作为矿物掺和料时,硅灰将更显著降低混凝土抗塑性开裂等级。为提高路面水泥混凝土的抗裂性,宜选择比表面积小于360 kg/m3的水泥,水灰比大于0.4、浆集比小于275∶725的配合比设计参数。当混凝土中掺加活性矿物掺和料时,应加强混凝土的早期养护,以抑制塑性裂缝的出现。

To cope with the situation that present pavement cement concrete is easy to appear plastic shrinkage cracking, in order to optimize the raw materials and the mix design parameters of pavement concrete more reasonably, the influence of fineness of cement, species and mixing amount of mineral admixture and concrete mix design parameters on early plastic shrinkage cracking performance of pavement cement concrete was comparatively studied by using the plate method proposed by Professor Kasai. The test results show that （ 1 ） it would be more detrimental to the control of plastic shrinkage cracking of pavement cement concrete when the cement specific surface area was larger, the content of mineral admixture became higher, the water-cement ratio turned smaller, and the cement paste-aggregate ratio trended to be greater; （2） relative to fly ash and mineral powder, silica fume will reduce the level of plastic shrinkage cracking resistance of concrete more significantly when used as mineral admixture; （3） in order to improve the crack resistance of pavement cement concrete, the mix design parameters should be selected as cement specific surface area less than 360 kg/m3 , water-cement ratio higher than 0. 4, and cement paste-aggregate ratio less than 275： 725 ; （4） when active mineral admixture was added in concrete, the early maintenance of concrete should be strengthened to inhibit the appearance of plastic shrinkage cracking.