Study On Compatibility And Mechanism Of Manufactured Sand And Polycarboxylic Superplasticizer

Manufactured sand and polycarboxylic superplasticizer are important components of modern concrete,and the compatibility between them affects the properties of concrete.In this paper,the effects of manufactured sand gradation,lithology,stone powder dosage,and polycarboxylic superplasticizer structure on the compatibility between manufactured sand and polycarboxylic superplasticizer are studied by mortar fluidity.The absorbability of manufactured sand to polycarboxylic superplasticizer is determined by MB value and TOC value of stone powder,wetting angle and permeability of superplasticizer to stone powder surface,and saturated-surface-dried water absorption of manufactured sands.The compatibility mechanism between manufactured sand and polycarboxylic superplasticizer is proposed by analyzing the chemical composition,mineral composition,surface texture and internal structure of manufactured sand.The studies show that the gradation of manufactured sand significantly affects the compatibility between polycarboxylic superplasticizer and manufactured sand.When the gradation is in zone II,the compatibility is better than that in zone I.The compatibility is the best when the manufactured sand gradation is in the middle area of zone II and with proper amount of stone powder.The lithology of manufactured sand also affects the compatibility,which is the best when the manufactured sand made by limestone,and is better when made by granite,gneiss and diabase,and is the worst when made by tuff.The influence of stone powder dosage on the compatibility is different when adding different stone powder.The side chain density and main chain length of polycarboxylic superplasticizer should be the optimum value,too small or too large is harmful to compatibility.In general,the smaller MB value and TOC value of manufactured sand powder are,the better the compatibility is.The smaller the wetting angle of polycarboxylic superplasticizer on the surface of manufactured sand powder is,and the slower the permeability is,the better the compatibility is.Because of the poor hydrophilicity of the alkaline rocks mainly composed of Ca and Mg,they have good compatibility with polycarboxylic superplasticizer;because the acid rocks which compose of Al and Si have good hydrophilicity,the compatibility is poor.Limestone is alkaline rocks,while granite,gneiss,diabase and tuff are acidic rocks.The uneven surface of manufactured sand will increase the specific surface area and make the compatibility worse.The flat surface is beneficial to improve the compatibility.The compactness of manufactured sand determines its compatibility with polycarboxylic superplasticizer.The higher the compactness is,the better the compatibility is.The diagenetic process of the rock determines the compactness of manufactured sand.The compactness of granite which is plutonic rock and limestone which is sedimentary rock are the best,that of diabase which is hypabyssal rocks and gneiss which is metamorphic rock are better,and the compactness oftuff which is volcanic clastic rock and has high porosity is the worst.