活性粉末混凝土叠合梁的收缩性能

Shrinkage Property of Reactive Powder Concrete Composite Beam

为改善活性粉末混凝土(RPC)材料的收缩性能,在RPC配合比基础上掺入碎石,设计了10片改进RPC-普通混凝土(NC)叠合梁、1片纯NC梁和2个改进RPC收缩试块.采用振弦式应变计和应力计分别测量了包含蒸汽养护阶段在内的改进RPC-NC叠合梁跨中截面混凝土的收缩应变及梁底纵向钢筋的收缩应力,同时与纯NC梁的收缩应变量进行了对比分析.结果表明:改进RPC材料的收缩应变量仅为650×10^(-6)~660×10^(-6);纵向钢筋配筋率、RPC高度、上部NC等级等因素对叠合梁跨中截面混凝土的收缩发展具有重要影响;由RPCNC叠合梁收缩引起的梁底纵向钢筋应力为40~63MPa,而由纯NC梁收缩引起的梁底钢筋应力为40MPa左右;改进RPC材料的收缩应变量仅为同条件下原RPC收缩应变量的37%,说明碎石的掺入可使RPC收缩应变量大大减小,同时也降低了RPC的造价,有利于RPC材料在工程中的推广应用.

The shrinkage property of reactive powder concrete（RPC） can be improved by mixing coarse ag- gregate. 10 RPC-normal eoncrete（NC） composite beams, 1 NC beam and 2 improved RPC specimens were designed on the basis of optimizing the mixture proportion. The shrinkage strain of RPC-NC composite beam at mid-span section and the shrinkage stress of longitudinal steel bars in the bottom of beams inclu- ding steam curing process were investigated by using vibrating wire extensometer and stress meter. The results show that the total shrinkage strain of improved RPC material is 650 X 10-6- 660 X 10-6. All the in- fluencing factors including the ratio of longitudinal reinforcement, height of RPC, concrete grade of NC, etc. have great effects on the shrinkage of composite beam at mid-span section, which is compared with the shrinkage of NC beam. The stress of longitudinal reinforcement was 40 - 63 MPa in the bottom of RPC-NC composite beams. The stress of longitudinal reinforcement is about 40 MPa in the bottom of NC beam. The results show that the shrinkage of improved RPC material is only 37% of normal RPC. It is indicated that the incorporation of gravel can greatly reduce the shrinkage of RPC and reduce the cost simultaneous- ly. And this will promote the application of RPC in engineering.