超缓凝半水混合料的力学性能及水化机理研究

Study on the mechanical properties and hydration mechanism of ultra slow setting semi water mixture

针对湿喷用喷射混凝土功能性损失与其集料在地下储存的实际工程问题,研究了一种高减水、超缓凝、可调节的超缓凝剂(SRA),进而研制出超缓凝半水混合料,通过单轴抗压、坍落度及水化热试验讨论了混合料的力学性能及水化机理。研究结果表明:SRA掺量为3.5%时,水化热突然降低,72 h后仍具有缓凝作用,SRA最佳掺量为3.0%。对于静置72 h的超缓凝半水混合料,随SRA掺量的增加,坍落度逐渐增大,经时坍落度损失逐渐减小;SRA掺量为2.8%~3.0%时,拌合物的流变性最好。当SRA掺量为3.0%时,超缓凝半水混合料试块的单轴抗压强度最高,28 d单轴抗压强度可达28.93 MPa。SRA中的三聚磷酸钠(STPP)和聚羧酸减水剂(PC)抢夺吸附点,二者相互抑制,从而发挥缓凝作用。

A high water reducing,super retarding,and adjustable super retarder(SRA)was studied to address the functional loss of sprayed concrete for wet spraying and the practical engineering problems of its aggregate storage underground.Furthermore,a super retarding semi water mixture was developed,and the mechanical properties and hydration mechanism of the material were discussed using uniaxial compression tests,slump tests,hydration heat tests,and other tests.The research results indicate that:when the SRA content is 3.5% of cement,the hydration heat suddenly decreases,and after 72 hours,it still has a retarding effect.The optimal SRA content is 3.0% of cement.The slump of the concrete mixture increases with the increase of SRA content,and the loss of slump decreases with the increase of SRA content when it is left standing for 72 hours.When the SRA content is between 2.8% and 3.0%,the rheological properties of the concrete mixture are the best.When the SRA content is 3.0%,the uniaxial compressive strength of the ultra slow setting semi water mixture test block is the highest,and the 28 d uniaxial compressive strength can reach 28.93 MPa.Sodium tripolyphosphate(STPP)and polycarboxylate water reducing agent(PC)in SRA seize the adsorption point,and the two inhibit each other,playing the role of retarding.