Effect of Air-entraining Agent and Mineral Admixture on Thixotropy Property of Fresh Concrete

Abstract

The elevation control of concrete bottom slab in curve line section of high-speed railway is difficult because fresh concrete cannot hold its shape and the slope of fresh concrete cannot maintain effectively before concrete hardened. To solve this problem, air-entraining agent and attapulgite clay mineral admixture were used to improve the thixotropy of fresh concrete. Results indicated when air-entraining agent and attapulgite clay incorporated simultaneously, the static yield stress of fresh concrete increased to 9.78 Nm, the dynamic yield stress decreased to 5.56 Nm, the ratio between the static and dynamic yield stress increased to 1.9, and the ability of holding the shape and slope was improved to 95.6%. This is mainly due to fibrous gel structure and orientation distribution of attapulgite clay and spherical air bubbles introduced by air-entraining agent in fresh slurry. These will provide valuable and useful references for quality and elevation control of concrete bottom slab of ballastless track in curve line section of ballastless track.