Development of Shrinkage Crack Control Method due to Combined use of Inert Powder and Chemical Admixture

结合使用惰性粉末和化学外加剂开发收缩裂纹控制方法

基本信息

批准号：
16360271
负责人：
NAWA Toyoharu
金额：
$ 9.02万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

Prevent concrete from cracking is actually one of the key issues for the design of concrete. The purpose of this study is to develop control of shrinkage crack due to combination of inert powder and chemical admixture. Most important results are summarized as follows:(1)When the inert inorganic additives such as slowly cooled blast furnace slag powder and limestone powder were added to the mortar with the organic admixtures which consist of polycarboxylate-based and polyoxyalkylene alcohol based polymer, autogenous shrinkage of mortar decreased markedly. However, the effect varied depending on the kind of organic admixture added. On the other hand, addition of fly ash also reduced significantly the autogenous shrinkage of cement mixes, but promoted to decrease their tensile strength. The opposite effects sometimes brought out a little tensile stress / tensile strength ratio, resulting in a low resistance of cracking. Hence, it was clear that to prevent crack due to autogenous and drying shrinkage, further development of sophisticated shrinkage reducing admixtures were required.(2)The polyethyleneimine based shrinkage reducing admixture absorbed strongly on to cement, providing no reduction of surface tension of pore solution in cement paste. However, it had an effect to reduce autogenous shrinkage and drying shrinkage, and showed good development in strength. Further, the combined use of calcium sulfate enhanced to reduce shrinkage and increase in strength.(3)The density of C-S-H in binary blends system could be calculated from data of Rietveld analysis, selective dissolution and mercury intrusion. As a result, the density of C-S-H became lower as increasing replacement ratio of fly ash. This implied that the volume of C-S-H gel due to fly ash hydration was larger than that of OPC hydration, providing elf-healing effect. Therefore, development of new method to prevent crack by this self-healing effect will be expected in future.

防止混凝土开裂实际上是混凝土设计的关键问题之一。本研究的目的是开发通过惰性粉末和化学混合物的组合来控制收缩裂纹的方法。最重要的结果概括如下：(1)当将缓慢冷却的高炉矿渣粉和石灰石粉等惰性无机添加剂添加到由聚羧酸酯基和聚氧化烯醇基聚合物组成的有机外加剂的砂浆中时，自收缩砂浆用量明显减少。然而，效果根据添加的有机混合物的种类而变化。另一方面，粉煤灰的添加也显着降低了水泥混合物的自收缩，但促进了其抗拉强度的降低。相反的效果有时会带来一点拉伸应力/拉伸强度比，导致抗开裂性低。因此，很明显，为了防止由于自生收缩和干燥收缩而导致的裂缝，需要进一步开发复杂的减缩外加剂。（2）基于聚乙烯亚胺的减缩外加剂强烈吸附在水泥上，不会降低孔隙溶液的表面张力在水泥浆中。然而，它具有减少自收缩和干燥收缩的效果，并且在强度方面表现出良好的发展。此外，硫酸钙的联合使用增强了减少收缩和增加强度的作用。(3)二元共混体系中C-S-H的密度可以根据Rietveld分析、选择性溶解和压汞数据计算出来。结果，随着飞灰替代率的增加，C-S-H的密度变低。这意味着飞灰水化产生的C-S-H凝胶的体积大于OPC水化的体积，从而提供自愈效果。因此，未来有望开发出利用这种自愈效应来防止裂纹的新方法。