Limestone Powder - Fly Ash - Cement And Cementitious Materials Performance

The using of mineral admixture must meet the requirement of environmental protection and economy.Finding new resources is very urgent.The ground limestone resources was abundant,using it can not only protect enviroment but also bring social and economic benefits.Fly ash was a type of excellent mineral admixture,many of its advantages were proved.The research about mixed addition of ground limestone and fly ash on the performance of cement-based was seldom.This paper reprots an study on mechanical performance,sulfate attack,drying shrinkage,concrete anti-permeability of mined addition of ground limestone and fly ash.This primarily work and achievements of the paper is as follows:1,The effects of ground limestone and fly ash and the mixed addition of ground limestone and fly ash on the performance of cement-based materials were studied.1) The addition of the ground limestone was found to increase the fluidity of mortars, the fluidity increase with the increasing of replacement of ground limestone. The strength of cement pastes and mortars increase with ground limestone content increasing at early age, when the replacement of ground limestone was up to 10%,the strength achieved maximum. The chemical combined water of ground limestone paste was consistent with variation of strength and increased when the hydration time increase. The water absorption of ground limestone pastes was opposite to variation of strength and decrease when the hydration time increase.2) The addition of fly ash can improve the fluidity of cement pastes and mortars. The strength of pastes and mortars was improved well of all the mixed addition specimen when the replacement of 5% ground limestone and 5% fly ash.The strength of mortars is better at the same age when the replacement of 5% ground limestone and 5% fly ash compare to the replacement of 5% ground limestone or 5% fly ash.when the replacement of ground limestone do not change,the chemical combined water decrease as the replacement of fly ash increasing,the change trend was consistent with variation of strength.The water absorption of combined admixture specimen was opposite to variation of strength.2,The effect of ground limestone and fly ash on the sulfate attack performance of cement pastes and mortars.1) The addition of the ground limestone was unfavorable on the sulfate attack performance of cement mortar. The strength of cement mortars with ground limestone addition began to decrease after immersed in Na2SO4 solution three months,the flexural and corrosion resistance coefficient of mortars with ground limestone addition was all less than 0.8 after immersed in Na2SO4 solution eigth months. The water absorption of cement mortars increases with ground limestone content increasing at same age. The SO3 content increases with the increasing of replacement of ground limestone.The gypsum was found in the specimens with 5% ground limestone addition after immersed in Na2SO4 solution eigth months.2) The addition of fly ash can improve the sulfate attack performance of cement mortars. The flexural resistance coefficient of mortars with fly ash was large than 0.8 after immersed in Na2SO4 solution eigth months. The corrosion resistance coefficient of mortars increase with fly ash content increaseing at earth age then decrease from immersed in Na2SO4 solution four months. The addition of fly ash can decrease the water absorption of cement mortars. The SO3 content decreases with the increasing of replacement of fly ash. The gypsum is not found in the specimens with 5% fly ash addition after immersed in Na2SO4 solution eigth months.3) The addition of fly ash can improve the sulfate attack performance of cement-ground limestone mortars. The flexural resistance coefficient began to decrease of the mortars with the mixed addition of ground limestone and fly ash. The corrosion resistance coefficient began to increase after immersed in Na2SO4 solution four months and large than the reference specimens. The water absorption of mortars with the mixed addition of ground limestone and fly ash was large then the reference specimens at earth three months then decrease after immersed in Na2SO4 solution four months.when the replacement of ground limestone do not change,the SO3 content decrease as the replacement of fly ash increase. The gypsum was also found in the specimens with 5% ground limestone and 5% fly ash mixed addition after immersed in Na2SO4 solution eigth months.But it better then the specimens with 5% ground limestone.3,The effect of ground limestone and fly ash on the dry shrinkage performance of cement mortar.1) The dry shrinkage of mortar increase with ground limestone content increasing at the same age, when the replacement of ground limestone was about up to 10%,the dry shrinkage achieved maximum.2) Fly ash can decrease the dry shrinkage of mortar at the same age, the replacement of fly ash is 10%,the dry shrinkage achieved minimum.3) The addition of fly ash can effectively decrease the dry shrinkage when the replacement of ground limestone is not changed.The dry shrinkage of mortar was larger when the replacement of 5% ground limestone and 5% fly ash compare to the replacement of 5% ground limestone or 5% fly ash.When the binder content was not varied,the dry shrinkage of specimen with the replacement of fly ash is minimum.4,The effect of ground limestone and fly ash on the anti-permeability performance of concrete.1) The replacement of ground limestone is disadvantage for the concrete anti-permeability. The concrete anti-permeability become worse as the replacement of ground limestone increase. The fineness of ground limestone had little effect on the concrete anti-permeability.2) Fly ash is better for the concrete anti-permeability. The concrete anti-permeability become well as the replacement of fly ash increase.3) The addition of fly ash can effectively improve the anti-permeability of the concrete with ground limestone powder.The fineness of ground limestone has not influence on the concrete anti-permeability with mixed addition of ground limestone and fly ash.The anti-permeability of concrete with mixed addition of ground limestone and fly ash become worse as the water ratio increase.