Effects of cement fineness and admixtures on the flowability of cement paste
In order to investigate the influence of the performance characteristics of raw materials and admixtures on the flowability of concrete,cement paste was used as the object of study,and their effects on the flowability of cement paste were analyzed through the effects of Portland cement fineness,water reducing agents and thickening agents on the filling water,adsorbed water and free water in cement paste.The test results show that as the particle size of cement decreases,the filling water and adsorbed water show an increasing trend,but the linear relationship between the free water and the flowability shows that the flowability of ultrafine Portland cement paste increases more with the free water than that of ordinary Portland cement,which indicates that the effect of the fineness of cement on the flowability of the cement paste is mainly when the water consumption is smaller,that is,when the water-cement ratio is smaller.Whether it is naphthalene-based superplasticizer or polycarboxylate superplasticizer,as they increase,both filling water and adsorption water decrease gradually,while the flowability gradually increases with the increase of free water.Both carboxymethyl cellulose(CMC)and hydroxypropyl methyl cellulose(HPMC)increase the filling water,and basically have no effect on the adsorption water within a certain dosing range,but both make the adsorption water increase significantly when exceeding a certain dosing.CMC had little effect on the linear relationship between flowability and free water,and HPMC caused a decreasing trend of flowability with the increase of free water.This is a good reference for exploring the influence of performance characteristics on the flowability of concrete,such as raw materials and admixtures etc.
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