常温养护型超高性能混凝土的圆环约束收缩性能

Restrained Shrinkage Behavior of Ultra High Performance Concrete Without Thermal Curing

研究了HCSA膨胀剂3种掺量(0%、3%、6%)下常温养护型超高性能混凝土(Ultra high performance concrete,UHPC)的圆环约束收缩性能,包括:(1)UHPC轴拉应力应变曲线测试;(2)根据GB/T50082的UHPC自由收缩实验;(3)根据ASTM C1581的UHPC圆环约束实验。结果表明,3种UHPC的极限拉伸应变均高于3 000με,28d总收缩值分别为1 005.6με、600.0με、462.2με,并且在圆环约束作用下转化为残余应变、弹性拉应变和塑性拉应变,其中塑性拉应变分别为700.4με、437.9με、389.9με。3种UHPC在拉伸应变达到1 000με时及圆环约束实验中均未发现0.01mm以上的可检测裂缝。基于拉伸实验和声发射损伤分析方法对UHPC进行应变分析,可知具有应变强化段的3种UHPC在圆环约束实验中的塑性变形以小于0.01mm的多点分布微裂纹形式存在。通过添加HCSA膨胀剂对常温养护型UHPC进行收缩补偿,可有效地降低UHPC自身的拉应力以及对原有结构的影响。

Restrained shrinkage behavior of ultra high performance concrete(UHPC)incorporating different HCSA expansion agent dosages(0%,3%,6%)without thermal curing was investigated by ring test,including three parts:(1)direct tensile stress-strain test of UHPC;(2)free shrinkage test of UHPC according to GB/T 50082;(3)restrained ring-test of UHPC according to ASTM C1581.The results indicated that three types of UHPC all achieved ultimate tensile strain higher than 3 000με.The 28 d free shrinkage values of three types of UHPC were 1 005.6με,600.0με,462.2μεrespectively,which converted into residual strain,elastic tensile strain and plastic tensile strain under ring restraint whose values were 700.4με,437.9με,389.9με,respectively.None of the three kinds of UHPC shows a crack wider than 0.01 mm both in the direct tensile test before a tensile strain of 1 000μεand in the ring test.The plastic tensile deformation mechanism of UHPC based on the direct tensile test and acoustic emission(AE)analysis method shows that the tensile stress-strain curves of the three kinds of UHPC all have the strain-hardening properties and their plastic deformation presents in the form of multiple cracks smaller than 0.01 mm in the ring test.Adding HCSA expansion agent can effectively reduce the tensile stress of UHPC and influence of UHPC on the structure.