Mechanical properties and drying shrinkage of manufactured sand concrete under steam curing
The application of manufactured sand in precast concrete components,and the wider coverage of manufactured sand in the construction industry,can effectively alleviate the shortage of natural sand resources. This article investigated the effect and corresponding mechanism of curing conditions and sand patterns through the concrete compressive strength,dynamic elastic modulus,drying shrinkage tests and microscopic tests such as scanning electron microscope tests,mercury injection tests and micro hardness tests. The results show that,regardless of the use of river sand or manufactured sand,steam curing concrete exhibits higher early mechanical properties and lower drying shrinkage compared to standard curing concrete. However,elevated temperatures leads to uneven distribution of hydration products,preventin subsequent hydration reactions,which leads to deterioration of later-stage mechanical performance. Microscopic examination indicates that pore coarsening,enlarged interface transition zones,and a loose structure of hydration products are the primary factors contributing to the degradation of later-stage performance in steam curing concrete. Nevertheless,substituting manufactured sand for river sand effectively mitigates the detrimental effects of steam curing thermal damage. Furthermore,the manufactured sand concrete under steam curing demonstrates superior mechanical properties and microstructure when compared with river sand concrete under steam curing. Specifically,manufactured sand concrete under steam curing has refined pore structure,denser interfacial transition zones and higher average matrix micro hardness values,resulting in an overall higher density. But the increase in capillaries smaller than 50 nm also leads to higher drying shrinkage deformation of manufactured sand concrete. The prediction model for the drying shrinkage of manufactured sand concrete under steam curing was established by introducing the influencing factors of the manufactured sand which is based on the GL 2000 shrinkage model. The prediction model can provide more accurate and effective drying shrinkage prediction of manufactured sand concrete under steam curing.
manufactured sandsteam cured concretemechanical propertiesdrying shrinkageshrinkage prediction model
万方数据
维普
