室内环境下UHPC的收缩徐变试验和预测

Experimental Study on the Shrinkage and Creep of UHPC in Indoor Environments

为明确室内环境下普通及补偿收缩超高性能混凝土(UHPC)的收缩徐变特征,分别对这2种超高性能混凝土进行持续1080d的力学、收缩和徐变性能测试,分析了补偿收缩组分对超高性能混凝土性能的影响规律。基于收缩和徐变的试验结果,分析了国内外3种不同规范公式对室内环境下超高性能混凝土收缩徐变预测的适用性,并引入相应的修正系数对既有收缩徐变模型进行修正,使之适用于补偿收缩超高性能混凝土的收缩徐变预测。结果表明:①补偿收缩组分的加入对超高性能混凝土的力学性能有负面影响,使立方体抗压强度、棱柱体抗压强度和弹性模量分别降低4.3%、5.1%和4.2%。②UHPC棱柱体抗压强度和弹性模量与立方体抗压强度间存在良好的统计关系,且该统计关系受配合比和龄期的影响较小。③补偿收缩组分能有效抑制超高性能混凝土的收缩,使收缩降低28.9%,但对徐变有负面影响,使徐变应变、徐变系数和徐变度分别增加13.3%、9.3%和15.8%。④DBJ43/T325—2017的收缩、徐变模型对室内环境下普通超高性能混凝土的收缩徐变均给予较好的预测,预测误差分别在4%和6%以内;SIA 2052—2016仅有收缩模型的预测结果与实测结果较好地吻合;引入收缩和徐变修正系数后的修正模型能分别对补偿收缩超高性能混凝土的收缩和徐变予以较好地预测,预测误差也分别在4%和6%以内。

To clarify the characteristics of shrinkage and creep of ordinary and shrinkagecompensating ultra-high performance concrete(UHPC)in indoor environments,mechanical properties,shrinkage,and creep were tested for 1080days on two types of UHPCs.The effects of shrinkage-compensating composites on the performance of UHPC were analyzed.Based on the test results of shrinkage and creep,three specifications were assessed for the prediction of shrinkage and creep.To predict the shrinkage and creep of shrinkage-compensating UHPC precisely,the shrinkage and creep influence coefficients of shrinkage-compensating composites were introduced to modify the models.The results show that:①The use of shrinkage compensating composites has a negative impact on the mechanical properties of UHPC,and the cubic compressive strength,prismatic compressive strength,and elastic modulus reduce by 4.3%,5.1%,and 4.2%,respectively.②Prismatic compressive strength and elastic modulus have a good statistical relationship with cubic compressive strength,and the influences of mix proportion and curing age on this statistical relationship are limited.③The addition of shrinkagecompensating composites can reduce shrinkage strains effectively by 28.9%;however,it has a negative impact on UHPC creep:the creep strain,creep coefficient,and specific creep can increase by 13.3%,9.3%,and 15.8%,respectively.④The shrinkage and creep model of DBJ43/T325—2017agree well with the measured results of the ordinary UHPC,and the prediction error is within 4%and 6%,respectively.Only the shrinkage model of SIA 2052—2016 agrees well with the measured results of ordinary UHPC.The shrinkage and creep influence coefficient of shrinkage-compensating composites could be used in the modified models to predict the shrinkage and creep of shrinkage-compensating UHPC precisely,and the prediction error is within 4%and 6%,respectively.