Effect And Mechanism Of Low Temperature Calcinationon Volcanic Powder Activity In The Region Of Hotan Xinjiang

Mineral admixtures,the essential part to modern concrete could significantly improve the concrete compactness and performance.It is a kind of functional adjustment material and could greatly improve the durability and workability of concrete.Normally,mineral admixtures of concrete shall be selected nearby.If there are no ready mineral admixtures of concrete for use around the site of the project,they will have to be transported remotely from other places,adding the cost of project construction.Therefore,to industrial backward regions like Hotan Prefecture lacking in fly ash and other artificial mineral admixtures and abundant in natural volcanic rock resources,it is necessary to exploit natural mineral admixture.The research object of the research lies in taking natural volcanic rock in Hotan Prefecture as the mineral admixture of concrete.It conducts methods like low temperature calcination and retention time to conduct research on their influence on activity improvement of natural volcanic rock,and applies strength test method of cement mortar、XRD、SQU、SEM and other means to master the law of activity change in natural volcanic rock and analyze the mechanism of activity improvement.The conclusions of the research in the paper are as followed:(1)Under the condition of low temperature calcinations at 300℃～800℃ without maximum temperature retention,findings of analyzing the change law of mortar strength after relevant calcinated volcanic rock powder is added are as followed.When the temperature reaches 500℃,28d mortar get the highest activity index of the flexural strength and compressive strength.(2)After they are calcinated at 500℃～700℃ and the maximum temperature retention time is set at 10 min and 20 min,it has been found that certain retention time of maximum temperature has significant contributions to the improvement of the strength activity index.When the temperature reaches 500℃～550℃,the effect is relatively fine if the retention time is 20 minutes compared with that of 10 min..(3)Through the test of XRD on hydration products and the calculation and analysis of semi-quantitative integral content,after 550℃～600℃ calcination of volcanic rock powder,SiO2、Al2O3、Fe2O3,the content of three major oxides and the hydration product content in calcinated volcanic rock powder+cementitious binder system change greatly.The macro performance is the growth of activity index of strength.It explains the change law of flexural strength and compressive strength of cement mortar specimen in the macro-mechanical properties and reveals the improvement of volcanic activity by low temperature calcinations.(4)Analysis from the angle of macroscopic strength and variation law of strength-activity index shows that the optimum calcinations temperature for improving the activity of natural volcanic rock powder in Hotan Prefecture,Xinjiang is 500℃～550℃ and the maximum temperature retention is 20min.From the perspective of microscopic morphology,structural characteristics,hydration process and hydration products,the optimum calcinations temperature is 550℃～600℃ and the maximum temperature retention is 20 min.