骨料和外加剂对活性粉末混凝土强度影响的试验研究

Experimental study on effect of aggregate and admixture on the strength of reactive powder concrete

为研究各配制参数对活性粉末混凝土28 d抗压强度与抗折强度的影响,依据GB/T 31387—2015《活性粉末混凝土》,共设计了18组不同配合比的100 mm×100 mm×100 mm混凝土试块,以骨料品种、骨料级配、粉煤灰、缓凝剂、矿物添加剂等为参数,测定其3~28 d的抗压与抗折强度。研究表明:在RPC配合比设计中,细骨料用石英砂替换一部分标准砂,有利于强度的提高;其中石英砂的占比越高,强度越高,当石英砂全部替代标准砂时,RPC强度最高;考虑颗粒间的填充密实与RPC的抗压与抗折强度,建议石英砂的骨料级配选用中+细+特细的组合;粉煤灰与硅粉复合掺入时,其粉煤灰的最佳掺量为20%;缓凝剂延缓了RPC的初凝时间,但同时造成了RPC抗压强度和抗折强度降低,混凝土拌合物的和易性变差;矿物添加剂可以改善混凝土拌合物的施工性能,降低黏度,提高坍落度,同时可以一定程度地提高RPC的抗压强度和抗折强度。

In order to study the influence of preparation parameters on 28 day compressive strength and flexural strength of reactive powder concrete,according to GB/T 31387—2015“Reactive Powder Concrete”,a total of 18 groups of 100 mm×100 mm×100 mm concrete test blocks with different mix proportions were designed.The compressive strength and flexural strength of blocks were measured from 3 days to 28 days with the parameters of aggregate variety,aggregate gradation,fly ash,retarder,mineral additive,etc.Results show that in RPC mix proportion design,replacement of a part of standard sand with quartz sand for fine aggregate is beneficial to the improvement of strength,and higher the proportion of quartz sand is,the higher the strength is.When quartz sand completely replaces the standard sand,strength of concrete reaches the highest.Considering filling density between particles and compressive and flexural strength of RPC,it is suggested that aggregate gradation of quartz sand should be medium,fine,ultra-fine.When the fly ash and silica powder are mixed,the optimum content is 20%.Retarder delays the initial setting time of RPC,but at the same time,the compressive strength and flexural strength of RPC are reduced,and the workability of concrete mixture is poor.Mineral additives can obviously improve construction performance of concrete mixture,reduce viscosity,improve slump,and improve compressive strength and flexural strength of RPC to a certain extent.