PVA-纳米SiO_(2)混凝土经冻融循环后的动态抗压特性

Dynamic Compressive Properties of PVA/NANO-SiO_(2) Concrete with Freeze-thaw Damages

为研究PVA纤维和纳米SiO_(2)对混凝土抗冻性的影响,对经历过冻融循环的PVA纤维混凝土、纳米SiO_(2)混凝土和PVA-纳米SiO_(2)混凝土施加动态压缩试验,测得抗压强度和峰值应变,以及质量损失率和相对动弹性模量,以此评价三种混凝土的抗冻性能,并以试验测得抗压强度劣化值构建了纤维混凝土冻融损伤的演化模型。研究结果表明:PVA纤维的掺入降低了混凝土冻融损伤的质量损失率,并使混凝土的延性有所提高,纳米SiO_(2)的掺入则明显提高了混凝土的抗压强度。掺加PVA纤维或掺加纳米SiO_(2)均可提高素混凝土的抗冻性,且PVA-纳米SiO_(2)混凝土的抗冻性优于PVA纤维混凝土,而PVA纤维混凝土的抗冻性优于纳米SiO_(2)混凝土。本文建立的纤维混凝土冻融损伤模型可较好地反映冻融损伤后混凝土抗压强度的劣化情况。

Three types of concrete specimens with admixtures of PVA fiber,nano-SiO_(2)and the both are tested under dynamic compression after freeze-thaw cycles to study the influences of the admixtures on frost resistance of concrete.Compressive strength,peak strain,mass loss ratio and relative dynamic elastic modulus are measured to do the evaluation,and the degraded compressive strength is used to construct a freeze-thaw damage model of fiber reinforced concrete.The results show that PVA fiber reduces mass loss ratio of the damaged concrete after freeze-thaw cycles and improves ductility of the material,while the addition of nano-SiO_(2)significantly improves compressive strength of the concrete.The addition of either PVA fiber or nano-SiO_(2)improves the frost resistance of concrete,but the former case is superior to the latter one,and adding both together can achieve further improvement.A model is finally established to evaluate the freeze-thaw damage of fiber reinforced concrete,which can estimate the compressive strength deterioration after freeze-thaw cycles.