活性掺合料改性RAC抗冻性试验研究

Experimental study on anti freezing property of modified RAC with active admixture

为了研究掺合料对RAC抗冻性的影响,对4组共48个100 mm×100 mm×100 mm的立方体试件,标准养护28 d后,分别进行抗压试验和劈裂拉伸试验,同时采用"快冻法",对掺合料RAC冻融循环下质量损失率和相对动弹性模量损失进行研究,研究结果发现:当粉煤灰掺量10%基础上,再掺入10%的硅粉,其RAC抗压强度远是普通RAC抗压强度的1.5倍,同时劈裂抗拉强是普通RAC的1.83倍,相比于普通RAC其力学性能均有所改善。并且,随着粉煤灰替代率的增加抗压强度与劈裂抗拉强度减小,但在粉煤灰掺量为20%时,其抗压强度与劈裂抗拉强度均高于普通RAC;经200次冻融循环后,10%粉煤灰+10%硅粉RAC的质量损失率分别是普通RAC、单掺20%粉煤灰RAC、复掺15%粉煤灰+5%硅粉RAC的27.3%、47.5%、87.3%,其质量损失率从小到大的排序依次是:复掺10%粉煤灰+10%硅粉RAC、复掺15%粉煤灰+5%硅粉RAC、单掺20%粉煤灰RAC、普通RAC;相对动弹性模量损失随着冻融循环次数的增加呈现递减趋势,其中在整个冻融循环过程中普通RAC相对动弹性模量下降速度最快,当冻融循环次数大于150次时,复掺10%粉煤灰+10%硅粉RAC相对动弹性模量均高于复掺15%粉煤灰+5%硅粉RAC、单掺20%RAC、普通RAC的相对动弹性模量。

In order to study the effect of admixture on the frost resistance of RAC,4 groups of 48 cubic specimens with a total of100 mm×100 mm×100 mm were tested for compression test and split tensile test respectively after the standard curing of 28 d.At the same time,the "fast freezing method"was adopted to carry out the loss of mass loss and relative dynamic elastic modulus under the freeze-thaw cycle of RAC.The research results show that the compressive strength of RAC is 1.5 times more than that of ordinary RAC,and the splitting tensile strength is 1.83 times that of ordinary RAC,and the mechanical properties of RAC are improved compared to ordinary RAC.In addition,with the increase of the fly ash substitution rate,the compressive strength and splitting tensile strength decrease,but when the fly ash content is 20%,the compressive strength and splitting tensile strength are higher than the ordinary RAC.After 200 freezing and thawing cycles,the mass loss rate of 10% fly ash+10% silica powder RAC is the ordinary RAC,the single doped fly ash RAC,and the compound 15%.The 27.3%,47.5%,87.3% of the fly ash+5% silica powder RAC,the order of its mass loss rate from small to large,is followed by 10% fly ash+10% silica powder RAC,15% fly ash+5% silica powder RAC,20% fly ash RAC,ordinary RAC,and the relative dynamic elastic modulus loss decreases with the increase of the freezing and thawing cycle times.During the freeze-thaw cycle,the relative dynamic elastic modulus of RAC is the fastest.When the number of freezing and thawing cycles is greater than 150 times,the relative dynamic elastic modulus of the 10% fly ash+10% silica powder RAC is higher than the relative dynamic elastic modulus of the 15% fly ash+5% silica powder RAC,the single 20%RAC and the ordinary RAC.