荷载对混凝土在腐蚀-冻融作用下强度的影响

为研究混凝土的多因素耐久性,采用高浓度腐蚀介质,测定普通混凝土(OPC)、高强混凝土(HSC)、高性能混凝土(HPC)、钢纤维增强高强高性能混凝土(SFRHPC)和高强高模聚乙烯纤维增强高强高性能混凝土(HEMPFRHPC)在(化学腐蚀+冻融循环)双重破坏因素(DDF)和(弯曲荷载+化学腐蚀+冻融循环)多重破坏因素(MDF)作用下的强度变化.结果表明:在1500次DDF和1600次MDF作用下,混凝土的抗压强度均存在不同程度的下降,弯曲荷载比对混凝土在MDF作用下抗压强度的降低作用存在一个阈值:HSC和HPC为40%,PFRHPC为20%,SFRHPC65%.掺加矿物掺合料有利于稳定高强度等级混凝土在MDF作用下的抗压强度,进一步掺加钢纤维还能够确保混凝土抗折强度的持续增长.

Effect of flexural stress on strength development of concrete subjected to combined actions of freezing-thawing cycles and chemical attack

To study the durability of concrete subjected to multiple damage factors,by adopting high concentration chemical attack solutions,we investigated the strength development of ordinary Portland cement concrete (OPC),high-strength concrete (HSC),high-performance concrete (HPC),steel fiber reinforced high-performance concrete (SFRHPC) and high elasticity module polyethylene fiber reinforced high-performance concrete (HEMPFRHPC) subjected to double damage factors (DDF),which are the combined actions of freezing-thawing cycles and chemical attack,and multiple damage factors (MDF),which are the combined actions of flexural load,freezing-thawing cycles and chemical attack.Results show that when subjected to 1 500 cycles of DDF or 1 600 cycles of MDF,the compressive strengths of all tested concretes are decreased.Further research indicates that there exists a critical stress ratio for flexural load to impair compressive strength of high grade concrete subjected to MDF,which is 40%,40%,20%,and more than 65% for HSC,HPC,PFRHPC and SFRHPC,respectively.It can be concluded that mineral admixture benefits the compressive strength of high grade concrete subjected to bittern MDF,additional steel fiber can even guarantee the continuous increase of flexural strength.