不同温度下自密实混凝土和减水剂的匹配性研究

为研究自密实混凝土在不同温度下的性能与减水剂电荷密度的关系,以温度、混凝土配比、减水剂电荷密度3个特征值为变量,选择曰常施工中最具代表性的3个温度,先后用2种常用的自密实混凝土配方,分别和2种电荷密度的聚羧酸系减水剂配对,组成12种试件,进行交叉试验。试验时借助流变仪测量自密实混凝土的剪切速率,从而计算出流变极限,得到混凝土的流变曲线。通过流变曲线从理论上评估每种试件的优劣,同时,对各试件进行28 d强度测试,通过最终测得的强度值,得出了和流变曲线一致的结论。基于理论分析和试验结果,针对低温、常温、高温三种环境,对自密实混凝土的配方设计(包括水灰比和水固比)及与减水剂的搭配,提出了设计建议,使混凝土达到最大强度和最稳定的力学特性。

Study on Matching Property of Self-compacting Concrete and Water Reducing Agent at Different Temperatures

In order to study the relationship between the performance of self-compacting concrete at different temperatures and the charge density of superplasticizer,taking the three characteristic values of temperature,concrete ratio and charge density of water reducing agent as variables,the three most representative temperatures in daily construction are selected,two kinds of commonly used self-compacting concrete formulas are used,which are matched with polycarboxylic acid water-reducing agents with two kinds of charge density respectively,and 12 kinds of test pieces are formed for cross test.In the tests,the shear rate of self-compacting concrete is measured by means of a rheometer,so as to calculate the rheological limit and obtain the rheological curves of concrete.The merits and demerits of each specimen are evaluated theoretically by rheological curves.At the same time,the 28-day strength of each specimen is tested,and a conclusion is obtained that the finally measured strength values are consistent with the rheological curves.Based on the theoretical analysis and test results,aiming at the three environments of low temperature,normal temperature and high temperature,some design suggestions are proposed for the formula design of self-compacting concrete(including water-cement ratio and water-solid ratio)and its matching with water reducing agent,so as to make the concrete reach the maximum strength and the most stable mechanical characteristics.