减缩剂对减少混凝土塑性收缩裂缝的影响  

Influence of shrinkage-reducing admixtures on the reduction of plastic shrinkage cracking in concrete

作　　者：José Mora-Ruacho Ravindra Gettu Antonio Aguado 贾福杰 

出　　处：《膨胀剂与膨胀混凝土》2009年第4期7-12,共6页 Expansive Agents & Expansive Concrete

摘　　要：暴露在高蒸发速率环境下的新拌混凝土很容易产生塑性收缩裂缝,特别是表面积与体积的比率很大的时候,目前的研究都证明了,减少拌合水的表面张力是减少塑性裂缝的一种很有效的办法。我们将传统混凝土和高强混凝土掺加超塑化剂和减缩剂,在塑性阶段暴露干燥,测量毛细孔压、沉降、内部温度和蒸发速率,结果显示减缩剂对减少混凝土甚至是高强混凝土的塑性裂缝都是很有效的,这主要由于蒸发速率减少,原因是孔中弯液面的发展导致毛细管压的峰值出现延迟和较低的沉降率。Fresh concrete exposed to high evaporation rates is prone to plastic shrinkage cracking, especially in structures with large surface area/volume ratios.The present work shows that the reduction of the surface tension of the mixing water is an effective way for decreasing such cracking.In this study, conventional and high strength concretes with superplasticizers and shrinkage reducing admixtures(SRAs) were exposed to drying in the plastic state.Continuous monitoring of the surface displacement facilitated the identification of the different stages of plastic shrinkage cracking.Measurements of capillary pressure, settlement, internal temperature and evaporation rate were also made.The results show the effectiveness of SRAs in reducing plastic shrinkage cracking, even in high strength concrete.This is attributed to the reduction in the evaporation rate, delay of the peak capillary pressure due to the development of menisci in the pores and lower settlement.

关 键 词：干缩 新拌混凝土 耐久性 收缩 外加剂 

分 类 号：TU528.0[建筑科学—建筑技术科学]