再生细骨料混凝土材料性能与结构行为研究评述

Material properties and structural behaviors of recycled fine aggregate concrete: an overview

国内外采用再生粗骨料制备再生骨料混凝土技术已较为成熟,已有成功的示范工程应用,在一定程度上缓解了工程对天然粗骨料的需求。然而,占再生骨料总质量约4%~60%的再生细骨料难以高效利用,造成资源浪费,加剧天然砂短缺趋势。文章基于大量的文献研究,旨在深入剖析再生细骨料混凝土材料与结构性能,揭示包括工作性能、力学性能和结构行为在内的再生细骨料混凝土性能特征,找出内在劣化规律,提炼再生细骨料混凝土应用和研究的目标和方向,为安全推广再生细骨料混凝土应用提供理论基础和研究依据。研究表明,再生细骨料的微观孔隙是造成再生细骨料混凝土性能复杂性的主要原因;再生细骨料对混凝土的工作性能和力学性能有不利影响,但通过调整水灰比和减水剂用量等方式,可以达到良好的工作性能和力学性能;相比相同抗压强度等级的天然骨料混凝土,再生细骨料混凝土的抗拉强度和弹性模量较低;再生细骨料混凝土构件的正截面承载能力与天然骨料混凝土构件相近,但其抗剪性能和与钢筋的锚固性能有待进一步研究。

Currently, recycled aggregate concrete(RAC) made of recycled coarse aggregate(RCA) has been proved technically and practically feasible in structural engineering and eases the demand for natural coarse aggregate to some extent.However, the recycled fine aggregate(RFA), which accounts for about 40-60% of total recycled aggregates, cannot be efficiently used, resulting in the unsettled problem of wasting resources and the lack of natural sand for construction.A literature overview on the material properties and structural behaviors of RFA concrete is presented in this paper, aiming to find the laws of the characteristics of RFA concrete including the workability, mechanical properties and structural behaviors, to point out the trend of future research, and to provide theoretical basis for application of RFA concrete in structural engineering.It is found that the micro cracks within RFA will lead to the complexity of RFA concrete properties.The workability and mechanical property of RFA concrete are inferior to those of natural aggregate concrete(NAC).However, they can be compensated by adjusting water to cement ratio and the dosage of superplasticizer.Compared to NAC with identical compressive strength grade, RFA concrete owns low splitting tension strength and elastic modulus.Although the bearing capacities of normal section for RFA concrete elements and NAC elements are similar, the shear performance and bonding between them and reinforcements should be further studied.