骨料缺陷对再生混凝土力学性能的影响

将2种普通混凝土破碎加工成再生粗骨料(RA),经620℃高温处理,剔除RA上的附着砂浆,得到再生粗骨料H-RA,然后配制再生骨料混凝土(RAC),测定其抗压强度、劈裂抗拉强度和断裂能.结果表明:RAC的力学性能显著下降,这归因于RA破碎加工导致的石子损伤及其表面的附着砂浆;在低水胶比条件下,RA中的石子损伤是导致RAC力学性能下降的主要因素,而在高水胶比条件下,导致RAC力学性能下降的主要因素则是石子表面的附着砂浆;吸水率与断裂能可敏锐反映RA的缺陷特征.

Influence of Defects in Recycled Aggregate on Mechanical Properties of Recycled Aggregate Concrete

An experimental research on the influence of defects in recycled aggregate on mechanical properties of recycled aggregate concrete(RAC) was conducted.Concretes with two water-binder ratios(0.59 and 0.25)were broken into recycled aggregate(RA),which might induce defects in the forms of damage of gravel in RA and mortar attached to RA.A type of thermal treatment,i.e.heating under temperature 620℃ for 3 h,was employed to remove attached mortar.Tests were conducted to determine compressive strength,tensile splitting strength and fracture energy of the concrete.The experimental results reveal that the mechanical properties of RAC are significantly lower than those of natural aggregate concrete.As to RAC with a low water-binder ratio,gravel damage is a main factor causing the decrease in the mechanical properties,while with a high water-binder ratio,attached mortar is such a factor.Among the properties measured in this investigation,water absorption and fracture energy are the two factors that can sharply reflect influence of the defects in RA during the broken process.It is suggested that prior to mix proportion design and preparation of concrete using recycled aggregate,it is necessary to obtain the details of demolished concrete such as its strength grade or water-binder ratio,and of the characteristics of defects in recycled aggregate.