Influence of the Grade and Content of Fly Ash on the Strength of Cement Mortar

This study added fly ash in cement mortar to replace some cement,using three grades (GradeI、II、III )and three contents (10%、20%、30%)of fly ash respectively to make nine kinds of cement mortar specimen.Standard curing periods were respectively 3,7,14,28 days of each kind of specimen.The compressive strength and flexural strength of these nine kinds specimen at different ages were tested to be compared with the strength of cement mortar specimen with no fly ash.The results show that both the flexural and compressive strength of GradeIand GradeIIfly ash specimen are similar and higher than the strength of Grade III fly ash specimen.When fly ash content is 10%,early flexural strength of GradeIand GradeIIfly ash specimen increase most and the compressive strength at 28 days are higher than that of specimen with no fly ash.Grade III fly ash specimen show tympanites and send out irritating ammonia smell. Test materials and methodsTest materials.Fly ash:fly ash produced in Zhengzhou city of Henan provience(GradeI、II、III ); Cement:ordinary Portland cement P.O32.5 produced by China United Cement Zaozhuang Co.,Ltd Aggregate:medium sand with all indicators meeting the requirements of test procedures and no impurities ;silt content is less than 5%;all particles are clean and angular.