预湿轻细骨料对混凝土内养护效率的影响

Effect of Pre-wetted Lightweight Fine Aggregate on Internal Curing Efficiency of Concrete

研究了2种轻细骨料的微观结构与释水性能及其预湿后对混凝土内部相对湿度和自收缩的影响.提出了混凝土内养护效率的概念,并研究了轻细骨料粒径与颗粒分布对内养护效率的影响.结果表明：轻细骨料孔隙体积和孔径皆大于硬化水泥净浆;预湿轻细骨料可以延迟混凝土由于自干燥引起的内部相对湿度降低并减小其降低幅度;内养护混凝土的自收缩和内部相对湿度存在线性关系.当轻细骨料用量占净浆体积的36%~39%时,混凝土在早期的28d内不产生自收缩.混凝土内养护效率随轻细骨料颗粒间距和半径比值的增大而减小,在轻细骨料颗粒间距和半径比值为1.1时,混凝土内养护效率为100%.

The microstructure and desorption properties of two types of lightweight fine aggregate（LW- FA） ,sintered fly ash and expanded shale, were investigated. The concept of ＂internal curing efficiency＂ was introduced. The effect of LWFA particle size and spacing on internal curing efficiency was also evalua- ted. The experiment results indicate：the pore volume and size of LWFA are larger than that of the harden- ed paste; pre-wetted LWFA can delay the decrease of concrete internal relative humidity induced by self- desiccation and reduce the extent; furthermore, for internal curing concrete, there exists a linear relation- ship between the autogenous shrinkage and internal relative humidity. When the contents of LWFA by volume of the paste were between 36% and 39%, autogenous shrinkage did not occur within 28 days. The internal curing efficiency decreases as the ratio of LWFA particle spacing to particle size increases. The re- sults show that 100% internal curing efficiency can be achieved if the ratio of LWFA particle spacing to particle size approaches 1.1.