化学外加剂对混凝土徐变的影响规律研究

Influence regularities of chemical admixtures on creep

采用自制的徐变加载装置,研究了萘系减水剂、聚羧酸减水剂以缓凝组分、减缩组分对等配合比混凝土徐变的影响规律,结合与混凝土同水灰比浆体非可蒸发水含量及混凝土内部相对湿度演化分析了其影响机理。结果表明,相比萘系减水剂,聚羧酸减水剂能显著降低混凝土的徐变,其中以早强型聚羧酸减水剂的效果最好;减缩剂对混凝土的徐变有降低作用,缓凝组分的掺入对徐变有不利影响;聚羧酸减水剂和减缩组分能通过降低混凝土内部水分传输和向外界扩散来降低徐变;早强型聚羧酸使浆体具有较多的水化产物数量,对强度的增加和徐变的降低有一定好处,缓凝组分的掺入会延缓水化并减少总水化产物数量,降低强度,使徐变增加。

The influence law of naphthalene based plasticizer,polycarboxylic superplasticizer,retarding component and shrinkage reducing component on creep characteristics of concrete with same mix proportion were studied by the self-made creep loading device and the influence mechamism were analyzed by testing non-evaporable water of paste with same water-binder ratio with concrete and internal relative humidity of loaded concrete specimens.The results indicate that： compared with naphthalene based plasticizer,polycarboxylic superplasticizers could significantly reducing creep of concrete,and this effect of early-strength polycarboxylic superplasticizer is the best;shrinkage reducing components could also reduce creep,the incorporation of retarding component have an adverse effect on creep;polycarboxylic superplasticizers and shrinkage reducing component reduce creep by decreasing the internal moisture transmission and diffusion to external environment;early-strength polycarboxylic superplasticizer make concrete have more hydration products,which have certain advantages on increasing strength and lower creep;incorporation of retarding component slows hydration and reduce the total hydration product contents,therefore strength reduced and creep increased.