硅灰和超塑化剂掺量对高性能混凝土强度及流动性的影响

Influence of silica fume and superplasticizer on compressive strength and flow diameter of high performance concrete

在高性能混凝土制备过程中,掺入硅灰、塑化剂分别可以达到改善水泥石水化产物成分和大幅降低水灰比的效果,确定硅灰和超塑化剂的最佳掺量是保证混土优良力学性能和工作性能的关键。对高性能混凝土中硅灰和超塑化剂的最佳配比和立方体抗压强度进行了试验研究。控制水灰比为0.15,制备超塑化剂质量掺量为0.3%~2.0%、硅灰替代率为8%~20%的高性能混凝土试件,并以流动性和28d抗压强度为主要参数进行试验对比分析。试验结果表明:超塑化剂质量掺量达到1.5%时,超塑化剂增塑效果最佳,若继续增加超塑化剂掺量流动性反而有所下降,硅灰替代率提高会使混凝土流动性降低,超过15%后基本丧失流动性;增加超塑化剂掺量会降低混凝土抗压强度,当硅灰替代率为10%时,混凝土达到峰值强度。试验过程中采用硅灰替代率10%,超塑化剂掺量1.1%的最优比例,在20℃常温养护条件下制备,实测其28d立方体抗压强度为93MPa,扩展度为170mm的高性能混凝土。

In producing high-performance concrete(HPC),the components of silica fume and superplasticizer couldcan improve the cementitious hydration and reduce water-cement ratio.Therefore,finding the optimum mix proportion of these two additives is the a key procedure issue to achieve high mechanical performance and workability of the HPC.In this paper,the optimal mix proportions of silica fume and superplasticizer in HPC have been investigated by comparing the flowability and 28-day compressive strength with thea fixed water-cement ratio of 0.15 by the comparison in flowability and 28-day compressive strength.The mass proportion of superplasticizer and the cementitious replacement percentage of silica fume were used in the range of 0.3%~2.0% and 8%~20%,respectively.The results showed that,the flowability of the fresh HPC reached the climax in when the mass proportion of superplasticizer was 1.5% of superplasticizer,and the flowability deteriorated decreased with the increasing of the cementitious replacement percentage of silica fume;the compressive strength of the hardened HPC reduced decreased compressive strength with the increasing of the content of super-plasticizer,and the maximum compressive strength was obtained within when the silica fume cementitious replacement was 10%.With the optimized mix design of content of silica fume of(10%) and super-plasticizer content of(1.1%),the HPC achieved 170mm in flow diameter and 93MPa at the age of 28 days under 20℃curing.