掺复合矿物外加剂混凝土的收缩性能研究

Study on Shrinkage of Concrete with Slag Composite Mineral Admixture

用矿渣微粉、火山灰质矿物外加剂及辅助助剂优化配伍组成复合矿物外加剂体系,并用其配制出高强度、大流动度及高耐久性的混凝土.结果表明:复合矿物外加剂可抑制混凝土自收缩变形,并使混凝土长期收缩变形得到补偿.通过对水化产物变化与水泥石自收缩变形曲线的综合分析,发现水泥石自收缩变形与水化产物AFt的形成密切相关,水化初期大量形成的AFt可改善水泥石自收缩变形,而AFt向AFm的转晶反应变形将增大水泥石的收缩变形.另外,根据XRD分析结果,还探讨了复合矿物外加剂改善自收缩变形的机理.

The paper deals with autogenous shrinkage of concrete with mineral admixture(SCA), which is composed of ultra\|fine slag, calcined kaolin and auxiliary agent in optimum compatibility and was used to prepare HPC instead of single ultrafine slag(SA). The experimental results show that SCA could either restrain the early autogenous shrinkage of paste or improve the prolonged shrinkage of concrete. General analysis of the hydration products and the autogenous shrinkage curve shows that the autogenous shrinkage is correlated closely with the formation of AFt. Because the deformation caused by the crystal transform reaction from AFt to AFm could supplement the shrinkage, the large amount of AFt produced in the early hydration could remarkably improve the autogenous shrinkage of paste. According to XRD analytic results, the mechanism how SCA improves shrinkage of concrete is proposed.