硅灰掺量对水泥基材早期收缩性能的影响

采用一种新的全自动混凝土收缩膨胀仪，连续测定了以5%、10%、15%水泥质量分数的硅灰替代水泥的混合浆体分别从终凝和24 h至168 h的自收缩值和干缩值. 试验发现:当试样中胶凝材料硅灰质量分数为5%、10%、15%时，其24 h龄期时自收缩值分别达到168 h龄期时的34.5%、57.1%、65.8%，24 h龄期时的干缩值分别达到168 h龄期时的66.7%、71.1%、75.8%，表明自收缩和干缩主要发生在24 h内. 试样在168 h龄期时，自收缩值、干缩值以及自收缩值与干缩值的比值均随硅灰掺量的增加而增加. 在96 h~150 h龄期内，自收缩速率出现了一个缓慢增加的阶段，表明硅灰与水化产物Ca_（OH）2之间发生了火山灰反应. 研究对高性能混凝土中硅灰掺量的控制以及早期的养护起到指导作用和借鉴意义.

Influence of Silica Fume Content on Shrinkage of Early-Age Cement-Based Materials

A new kind of automatic contractometer was used to continuously measure the autogenous and drying shrinkage of the paste samples with the silica fume of 5%，10% and 15% by mass of cement from final setting to 168 h and from 24 h to 168 h. The results show that the autogenous shrinkage values from final setting to 24 h are 34.5%， 57.1% and 65.8% of those at 168 h and the drying shrinkage values from final setting to 24 h are 66.7%， 71.1% and 75.8% of those at 168 h， which indicate that the autogenous and drying shrinkages mainly occur in the first 24 h. The autogenous and drying shrinkage values and the ratios of autogenous shrinkage to drying shrinkage increase with the silica fume content increasing at 168 h. There is a slow increase trend in the autogenous shrinkage rate curves from 96 h to 150 h， demonstrating that the pozzolanic reaction occurs between silica fume and the hydrate product Ca_（OH）2 from cement hydration. The study provides guidance and reference for controlling silica fume content in high performance concrete and cement-based materials curing at early stage.