花岗岩石粉对砂浆干燥收缩性能的影响

Effect of Granite Powder on Drying Shrinkage

本工作针对花岗岩石粉,首先研究了不同粉磨时间(0、20、40、60 min)下石粉的颗粒特征,并探究了粉磨时间及石粉掺量(0%、5%、10%、15%、20%,质量分数,下同)对砂浆干燥收缩性能的影响规律。其次,采用扫描电镜(SEM)、同步热分析仪(TG-DSC)深入分析了石粉掺量和粉磨时间对掺花岗岩石粉砂浆的微结构形成特征和水化产物的影响规律。最后,基于灰熵分析方法,计算得出石粉颗粒特征参数与砂浆28 d干燥收缩活性指数的灰熵关联度,从而把握颗粒特征参数中影响干燥收缩的关键参数。结果表明,原状石粉颗粒粒径在56.4~63.2μm含量的占比最大,为5.1%,经20、40、60 min粉磨后,粒径在17.8~20.0、22.4~25.2、15.9~17.8μm占比达到最大,分别为3.5%、3.3%、3.4%。当粉磨时间延长时,掺石粉砂浆的抗干缩性能表现为先降低后升高再降低的变化趋势。相比基准配合比,掺5%、10%、15%的粉磨40 min的石粉,砂浆28 d干缩率分别减小了11.9%、35.2%、45.3%,当掺量增至20%时,干缩率减少了1.9%。灰熵分析表明,石粉的粒度累积分布数达到10%所对应的粒径、比表面积和20~40μm颗粒含量是影响砂浆干缩性能的关键参数,面积平均粒径和大于60μm颗粒含量对砂浆干缩性能影响较弱。

In this study,the characteristics of ground granite powder with different times(0,20,40,and 60 min)were studied.The effects of grinding time and amount of granite powder(0%,5%,10%,15%,and 20%)on the drying shrinkage of mortar were investigated.Scanning electron microscope and TG-DSC were used to analyze the microstructure and hydration products of granite stone powder mortar.Finally,gray entropy analysis was used to observe the key particle parameters affecting drying shrinkage;this was done by determining the gray entropy correlation between the particle parameters of granite powder and the 28 d drying shrinkage activity index of mortar.The results indicate that the highest proportion of the particle sizes in the range of 56.4—63.2μm in the raw granite powder is 5.1%.After crushing,the proportions of the particle sizes in the ranges of 17.8—20.0,22.4—25.2,and 15.9—17.8μm are 3.5%,3.3%,and 3.4%,respectively.With increasing grinding time,the drying shrinkage resistance first decrease,then increase and then decrease.Compared with the drying shrinkage rate of the reference mix,those of 5%-,10%-,and 15%-stone-powder-added mortar mixes(ground for 40 min)at 28 d are lower by 11.9%,35.2%,and 45.3%,respectively.Drying shrinkage decreased by 1.9%when the content increase to 20%.Gray entropy analysis shows that the particle size corresponding to the cumulative distribution of the particle size of the stone powder reaches 10%.Specific surface area and the particle content of 20~40μm are found to be the key parameters affecting the drying shrinkage performance of mortar.The area average particle size and the scope of particles>60μm had significantly minor effects on the drying shrinkage performance of mortar.