再生粗骨料附着砂浆含量对再生混凝土抗冻耐久性的影响

选取五种不同附着砂浆含量的商用再生粗骨料在全取代天然粗骨料条件下制备C40再生混凝土,探讨了30%极限拉应力水平下,再生粗骨料附着砂浆含量对再生混凝土抗冻耐久性的影响规律,通过数学拟合确定了基于相对动弹性模量和抗冻耐久性指数要求的砂浆界限含量。结果表明:冻融循环后,再生混凝土抗压强度损失率与附着砂浆含量存在较强线性关系;再生混凝土质量损失率、相对动弹性模量、抗冻耐久性指数均与再生粗骨料附着砂浆含量呈二次函数关系;以冻融循环300次后再生混凝土相对动弹性模量降至60%为限值,获得对应的砂浆界限含量为49.52%(质量分数);以不同设计使用年限及不同冻融工况所规定的抗冻耐久性指数作为界定条件,得到了再生混凝土在拉应力条件下满足相应抗冻耐久性指数的砂浆界限含量。最后,通过搜集文献数据验证了本研究结果的合理性。

Effect of Attached Mortar Content of Recycled Coarse Aggregate on Frost Resistance Durability of Recycled Aggregate Concrete

Five kinds of commercial recycled coarse aggregate (RCA) with different attached mortar content were selected to prepare C40 recycled aggregate concrete under the condition of full substitution for natural coarse aggregate. The effect of attached mortar content of RCA on the frost resistance durability of recycled aggregate concrete under 30% of ultimate tensile stress level was discussed, and the mortar limit content based on relative dynamic elastic modulus and frost resistance durability factor was determined by mathematical fitting. The results show that there is a strong linear relationship between the loss rate of compressive strength of recycled aggregate concrete and the attached mortar content after freeze-thaw cycles. The mass loss rate, relative dynamic elastic modulus and frost resistance durability factor of recycled aggregate concrete have a quadratic function relation with the attached mortar content of recycled coarse aggregate. The relative dynamic elastic modulus of recycled aggregate concrete after 300 freeze-thaw cycles is reduced to 60% as the limit value, and the corresponding mortar limit content is obtained to be 49.52% (mass fraction). Taking the durability factor specified by different design service life and freeze-thaw working conditions as the defining conditions, the mortar limit content satisfying the corresponding durability factor under tensile stress is obtained. Finally, the rationality of the research results is verified by collecting literature data.