Cementitious Material With Low Clinker Content

The effect of limestone powder content on the fluidity and strength of the Portland cement mortar was studied with different water-binder ratios.The low clinker cementitious material which consists of 40% Portland cement and 60% admixture was produced,and the admixture consisted of limestone powder and slag powder or fly ash in different proportions.The effect of low clinker cementitious materials with different limestone powder content on the performances of concrete was studied with two different water-binder ratios,and the mechanism of limestone powder in concrete was analyzed.In the mortar experiment,0.38,0.44,and 0.50 water/cement ratios were used.When the water/cement ratio was the same,the fluidity of the mortar increases as the limestone powder content increased,and when the limestone powder content was 40%,the fluidity of the mortar was the largest.When the limestone powder content was fixed,the fluidity increases as the water/cement ratio increased.When water/cement ratio was 0.38 and the content of limestone powder was not more than 20%,the 28 d strength of mortar was large,but the 60 d strength reduced.When water/cement ratio was large,the incorporation of limestone powder was detrimental to mortar strength.In the concrete,0.38 and 0.50 water/cement ratios were used.When the total amount of portland cement was 40%,the suitable mixed ratio of limestone powder and slag powder or fly ash can improve the workability of the fresh concrete significantly.When the content of limestone powder in C30 concrete is 40% and the content of limestone powder in C50 concrete is 30%,the flow and slump of the fresh concrete were the largest.With the increase of limestone powder content,the compressive strength of concrete decreased.The strength of concrete decreased slowly when the amount of limestone powder is not more than 30%.The limestone powder affected the chloride ion permeation resistance,carbonation resistance,sulfate resistance,freeze-thaw resistance of concrete.When the limestone powder content is not more than 30%,the chloride ion permeation resistancse of C30 and C50 concrete were same as that of standard sample with cured for 28 days,and the chloride ion permeability reduced significantly with the increase of limestrne powder content.The degree of carbonization of the concrete with limestone powder-slag powder and the concrete with limestone powder-fly ash were similar when the limestone powder content is not more than 40%.The strength of the concrete soaked in sulfate solution for 28 days and 60 days was higher than that of the standard cured concrete,the strength growth rate gradually increased with the increase in the amount of limestone powder.In the case of high water/cement ratio,the freezing and thawing performance of concrete decreased when limestone powder was incorporated,in the low water/cement ratio,the freezing and thawing performance of concrete was similar to that of the benchmark group when the content of limestone powder was more than 20%.With the same amount of limestone powder,the durability of reconstituted concrete with slag powder is better than that of concrete mixed with fly ash.The influence of limestone powder on concrete was a combination of acceleration effect,filling effect,water reduction effect and dilution effect.