盐冻循环作用下再生保温混凝土的抗冻性能研究

Study on frost resistance of recycled thermal insulation concrete under salt freezing cycle

为研究再生粗骨料取代率对盐冻循环作用下再生保温混凝土抗冻性能的影响,对不同再生粗骨料取代率试件在盐冻循环0~100次下的宏观形貌、微观形貌、氯离子浓度、质量损失率、抗压强度和劈裂抗拉强度等指标进行对比分析。结果表明,盐冻循环100次后,再生粗骨料取代率为0的试件表面未发生明显变化,再生粗骨料取代率为30%和50%的试件表面出现再生粗骨料剥落和少量浆料脱落,再生粗骨料取代率至70%和100%的试件表面出现了贯穿性裂纹和再生粗骨料剥落现象。随着盐冻循环次数从0增加至100,不同再生粗骨料取代率试件的抗压强度和劈裂抗拉强度都呈现减小特征;在相同盐冻循环次数下,再生粗骨料取代率越高则试件的抗压强度和劈裂抗拉强度越小,再生保温混凝土试件的抗压强度和劈裂抗拉强度损失率都随着盐冻循环次数增加而增大。盐冻循环过程中,裂纹先在旧界面薄弱区产生,并随着盐冻循环次数增加而出现裂纹扩展并贯穿至新水泥砂浆中。

In order to study the effect of the replacement rate of recycled coarse aggregate on frost resistance of recycled thermal insulation concrete under the salt freezing cycle,the macroscopic morphology,microscopic morphology,chloride ion concentration,mass loss rate,compressive strength and split tensile strength of specimens with different replacement rates of recycled coarse aggregate under the salt freezing cycle 0~100 times were compared and analyzed.The results show that after 100 cycles of salt freezing,there is no obvious change on the surface of the specimens with the replacement rate of recycled coarse aggregate of 0,the specimens with 30%and 50%of recycled coarse aggregate have spalling of recycled coarse aggregate and a small amount of slurry shedding,and the surface of specimens with 70%and 100%recycled coarse aggregate replacement rates show through cracks and spalling phenomenon.The compressive strength and split tensile strength of specimens with different replacement ratio of recycled coarse aggregate decrease with the increase of salt freezing cycles from 0 to 100.Under the same number of salt freezing cycles,the higher the replacement rate of recycled coarse aggregate is,the smaller the compressive strength and split tensile strength of specimens are,and the loss rate of compressive strength and split tensile strength of recycled thermal insulation concrete specimens are all along with the number of salt freezing cycles increase and increase.During the salt freezing cycle,the cracks initiate preferentially in the weak area of the old interface,and crack propagation occurs with the increase of the number of salt freezing cycles spread and penetrate into the new cement mortar.