冻融循环下掺合料对UHPC强度影响规律研究

Effects of Admixtures on the Strength of UHPC Under Freezing-thawing Cycles

为研究冻融循环下掺合料对超高性能混凝土(UHPC)强度的影响,以硅粉(10%、15%、20%)、偏高岭土(5%、10%、15%)、镀铜钢纤维(0.5%、1.0%、1.5%、2.0%)为掺合料,开展冻融前后UHPC抗压和抗折强度试验。建立岭回归模型分析UHPC冻融前后强度变化,并对影响UHPC冻融后强度变化的关键因素进行分析。结果表明:UHPC的强度随硅粉、偏高岭土掺量的增加先增加后减小,随镀铜钢纤维掺量的增加而增大;冻融循环500次后UHPC的抗压和抗折强度均有所下降,抗压强度下降11%~15%,抗折强度下降13%~16%;三种掺料对UHPC强度的影响大小为:镀铜钢纤维>偏高岭土>硅粉。硅粉、偏高岭土、镀铜钢纤维对UHPC强度影响明显。

In order to investigate the effects of admixtures on the strength of UHPC under freezingthawing cycles,compressive and flexural strength tests were carried out with silica fume(10%,15%,20%),metakaolin(5%,10%,15%),and copperplated steel fiber(0.5%,1.0%,1.5%,2.0%)as the admixtures.A ridge regression model was established to analyze the strength changes of UHPC before and after freezingthawing.At the same time,the key factors affecting the strength changes of UHPC after freezingthawing were analyzed.The results are as follows.Silica fume,metakaolin,copperplated steel fibre had obvious influence on the strength of UHPC.The strength of UHPC increased and then decreased with the increase of silica fume and metakaolin content.It increased with the increase of copperplated steel fiber content.The compressive and flexural strength of UHPC decreased after 500 times of freezethawing cycles,with the compressive strength decreasing by 11%~15%and the flexural strength decreasing by 13%~16%.The effects of the three admixtures on the strength of UHPC from high to low were copperplated steel fibre,metakaolin,silica fume.The error of the fitting results of the ridge regression analysis was small,and the accuracy of the model was high.