不同冻融方式下混凝土双K断裂韧度对比试验

Experimental study on double-K fracture toughness of concrete in different freezing and thawing modes

为了研究不同冻融方式对混凝土双K断裂韧度带来的不同影响,设计了5组共计15个试件,分别经历干燥、水浸泡、水冻融、盐浸泡、盐冻融作用20 d后进行三点弯曲梁试验。测定了试件断裂过程中的荷载、张口位移、裂缝尖端应变等参数的特征值和全过程曲线,基于双K断裂理论分别计算了各组环境下混凝土的有效裂缝长度、起裂荷载、失稳荷载等断裂参数。结果表明:不同冻融方式对混凝土造成的影响具有一定的相似性,水冻融与盐冻融均会对混凝土的弹性模量造成损失,使其断裂力学性能下降,但会提高混凝土韧性。在损伤程度和损伤后混凝土受力表现上不同冻融方式有显著区别。水冻融后混凝土受荷时更易开裂,但水冻融环境对混凝土抵抗裂缝发展能力的影响不明显。盐冻融后混凝土抵抗裂缝发生以及发展的能力同时降低,但混凝土受力时裂缝的发生会相对推迟。

In order to study the effects of different freezing and thawing methods on the fracture toughness of concrete with double-K,five groups of 15 specimens,respectively subjected to drying,water immersion,freezing and thawing,salt immersion and salt freezing and thawing for 20 days,were studied in the three point bend test.The eigenvalues and the whole process curve of the load,the displacement of the mouth and the strain at the tip of the crack were measured.Based on the double-K fracture theory,the effective crack length,the crack initiation load,the instability load and other fracture parameters were calculated.The results show that the influence of different freezing and thawing methods on the concrete has some similarity.Not only the concrete of water freezing and thawing but also the concrete of salt freezing and thawing can damage the elastic modulus of the concrete,decrease the mechanical properties of the concrete and increase the toughness of the concrete.However,there is a significant difference in the way of freezing and thawing between the degree of damage and the concrete after damage.Water freezing and thawing damage to the concrete is mainly manifested in the fact that the concrete is more easily cracked when subjected to water freezing and thawing,but the effect of water freezing and thawing environment on the development of concrete in resistance to cracking is insignificant.Salt freeze-thaw damage to concrete is mainly manifested in the salt freeze-thaw resistance to concrete cracks and the development of the ability to reduce at the same time,but the concrete cracks occurrence will be relatively postponed.