凝灰岩机制砂特性对砂浆流动度和强度的影响机理OA北大核心CSTPCD

The physical properties including crushing index,bulk density,void fraction,saturated surface dry water absorption and specific surface area of tuff manufactured sand from 10 different manufacturers were determined.The correlations between various characteristics and mortar fluidity,compressive strength and flexural strength were studied,and the internal mechanism was analyzed.The results show that the sharp corners of manufactured sand increase the crushing index and the void fraction.Lithology of the parent rock and fine will affect the saturated surface dry water absorption and specific surface area of the manufactured sand.The difference in saturated surface dry water absorption will not only affect the fluidity of the fresh mortar,but also have influence on the time-varying loss of the fluidity.The greater the saturated surface dry water absorption of sand,the smaller the fluidity of fresh mortar,and the greater the time-varying loss of the fluidity.When the water-cement ratio is 0.5,the flexural strength and compressive strength of manufactured sand mortar are higher than those of standard mortar.The difference in strength is mainly due to two reasons.One is the strong mechanical bite force brought by the rough surface of manufactured sand and the other is the improvement of interfacial transition zone caused by high saturated surface dry water absorption of sands.With the same fluidity,the influence law of mortar's strength changes with the fluidity value.When the fluidity is 180 mm,the strength of the manufactured mortar is still higher than that of the standard mortar.But,when the fluidity increases to 240 mm,the water-cement ratio increases significantly,the strength of manufactured mortar is far lower than that of standard mortar.