再生细骨料对混凝土力学性能及抗冻性能研究

摘要

Recycled fine aggregate is the reprocessed product of waste concrete .In order to promote the engineering ap-plication of recycled fine aggregate ,the compressive strength ,splitting tensile strength ,dynamic elastic modulus and weight loss of a regenerated concrete with different recycled fine aggregate replacement rate were studied in this research . The results show that recycled fine aggregate reduces the compressive strength of concrete .The downward trend of the compressive strength is more obvious with higher recycled fine aggregate replacement rate .The change of compressive strength is not significant after 28 days .The splitting tensile strength of recycled concrete is higher than natural concrete . The substitution rate of the recycled fine aggregate makes the splitting tensile strength show the trend of increasing first and then decreasing .When the substitution rate rises to 20 percent ,splitting tensile strength tends to be stable .The re-lationship between splitting tensile strength and compressive strength of recycled fine aggregate concrete is obtained with statistical regression .With the increasing of freeze-thaw circle numbers ,the decrease rate of dynamic elastic modulus and weight loss increase gradually .Finally ,some specimens were damaged after 75 times freeze-thaw circles .Higher recycled fine aggregate replacement ratio of concrete shows poor performance of frost resistance .%再生细骨料是废弃混凝土再加工的产物。为了促进再生细骨料的工程应用，采用不同再生细骨料取代率，对混凝土的抗压强度、劈裂抗拉强度和评定抗冻性能的动弹性模量及质量损失率进行研究。结果表明，再生细骨料取代率越大，混凝土抗压强度下降趋势越明显；经28 d 养护后，龄期对再生混凝土抗压强度影响不显著；掺加了再生细骨料的混凝土，其劈裂抗拉强度普遍高于对照组，劈裂抗拉强度随着再生细骨料取代率的增加呈现出先增大后减小的趋势，取代率达到20％后，劈裂抗拉强度趋于稳定；通过构建抗压强度及劈裂抗拉强度间关系，提出了再生细骨料作用下混凝土劈裂抗拉强度与抗压强度的经验回归公式；同时，随着冻融次数的增加，再生细骨料取代率越大，混凝土的动弹性模量下降率及质量损失率也随之增大，冻融次数达到75次，部分试块出现冻坏现象，较高再生细骨料取代率的混凝土表现出较差的抗冻性能。