养护条件对预制盾构管片混凝土力学性能及微观形貌的影响

Effects of curing condition on the mechanical properties and micromorphology of precast shield pipe sheet concrete

为解决预制混凝土管片后期浸水养护引起的水资源消耗量大,废水处理成本高,带水作业存在安全隐患等问题,提出用喷雾代替浸水的新型养护方式,并针对新型喷雾养护和传统浸水养护两种方式下管片混凝土材料的力学性能及微观形貌开展试验,研究了两种养护条件对不同龄期混凝土抗压强度、抗折强度及微观形貌的影响规律。结果表明:在短龄期时,新型喷雾养护条件下混凝土的抗压强度低于浸水养护,但在28 d龄期时,两种养护条件下混凝土的抗压强度接近,且均能达到相应的强度等级要求;在整个养护龄期内,喷雾养护条件下混凝土的抗折强度始终低于浸水养护,但在28 d龄期时差距缩小,喷雾养护混凝土的抗折强度较浸水养护仅低6.9%;在7 d龄期时,喷雾养护下混凝土的水化程度比浸水养护低,导致混凝土早期的力学性能较差,但在28 d龄期时,喷雾养护下混凝土水化充分,形成致密的水化产物,保证了混凝土后期的力学性能。

In order to solve the problems of large water consumption,high cost of wastewater treatment and safety hazards of working with water caused by the immersion curing of precast concrete pipe sheets,a new curing method of spraying instead of immersion was proposed,and the mechanical properties and micromorphology of concrete materials of pipe sheets under the new spray curing and traditional immersion curing methods were tested.The effects of the two curing conditions on the compressive strength,flexural strength and micromorphology of concrete at different ages were investigated.The results show that the compressive strength of the concrete under the new spray curing condition is lower than that of the immersion curing condition at short ages,but at 28 d age of concrete,the compressive strengths of the concrete under the two conditions are close to each other,and both can reach the corresponding strength levels.During the whole curing period,the flexural strength of concrete under spray curing condition is always lower than that of immersion curing.However,the gap is reduced at 28 d age,the flexural strength of spray curing concrete is only 6.9%lower than that of immersion curing;at the 7d age,the degree of hydration of spray curing concrete is lower than that of immersion curing,resulting in poorer mechanical properties in the early stage of the concrete,but at 28 d age,the spray curing concrete is fully hydrated,forming a dense hydration product,which ensures the mechanical properties of the concrete in the later stage.