Research On The Influence Of Diatomite On The Mechanical Properties And Microstructure Of Portland Cement

The diatomite is a highly active and non-crystal mineral.The main composition of it is amorphous silicon dioxide.Now high quality diatomite has been utilized to construction and building industry,but the low quality of it hasn't been fully used,which is not only a waste of resource but also cause seriouspollution.So it is urgent for us to make good use of the low quality diatomite.As for the study of cement additive,many researches related to the the impact of additive on the performance of the cement have been done from different spectrum.This paper mainly focuses on the influence of diatomite on the mechanical property and microstructure of the Portland Cement on the basis of the previous researches.The influence of the quality,grain size and mixing amount of the diatomite with regard to the compressive strength of the cement under different temperature regime is studied.The effect of particle size distribution on the strength of cement paste was analyzed by grey correlation degree,furthermorethe hydration behavior and pore microstructure of diatomite silicate cement were studied.Under different curing condition,the compressive strength of Portland Cement with First Grade Diatomite is obviously higher than those without it at corresponding stage.As the content of A,B,C three kinds of particle sizediatomite increase,the diatomite silicate cement strength decrease.In contrast to the blank,the 28 d strength is higher when the specimen with 2% and 5% mixing amount is cured at 20?.Changing the curing temperature to 5?,only the specimen with 2% mixing amount does so.When the temperature is lowered to-10?,only the specimen mixed 2% diatomite of A grain size has a higher strength than the blank.Maintaining the mixing amount at 2%,the impact of the diatomite grain size on the diatomite silicate cement is as follows: at 5? and 20?,the strength is enhanced by all three kinds of particle size,and C particle size has a more clear effect than the others;at-10?,A particle size rise the strength compared to the blank,while the B and C particle size has a counter influence on the strength.When the curing temperature is 20?,and the first grade diatomite dosage is 2%,to the compression strength of 7d and 28 d,the influence of the maximum particle size range is >20?m and 0~5?m respectively.When the curing temperature is 5?,and the first grade diatomite dosage is 2%,to the compression strength of 7d and 28 d,the influence of the maximum particle size range is 0~5?m and >20?m respectively.When the curing temperature is-10?,and the first grade diatomite dosage is 2%,to the compression strength of 7d and 28 d,the influence of the maximum particle size range is 15~20?m and 10~15?m respectively.From microscopic angle,the main characteristic peak of C3 S and C2 S are decreased,and the number of hydration products is much higher than that of Secondary Diatomite samples,which shows First Grade Diatomite can promote the hydration process and make the cement more compact.With the increase of the diatomite,main characteristic peaks of C2 S and C3 S is falling,when the mixing amount reaches 15%,it begins to rise.And at the same time,the amount of calcium hydroxide declines.The paste with diatomite is dense as against the blank,but the hydration product of the cement with 15% diatomite has bad lap joint and the hydration structure is loose,which indicates the increase of the amount of diatomite can promote the hydration of cement,but the effect of large addition of Diatomite on the cement hydration is not good.By analyzing the porosity of samples with A,B and C diatomite particles,the porosity of the sample set for 7 dayswas lower than that of the blank samples at the temperature of 20,and the porosity of the samples was decreased with the increase of 0~5 um particles.In comparison with the blank,The number of harmless hole(20nm)and less harmful hole(20-50nm)in diatomite silicate cement is increasing,while the number of harmful pore(50-200nm)and multiple harm hole(> 200nm)is reduced,and the multiple harm pore has a sharp decline in amount.with the grinding of diatomite,the particle size distribution changes.Among all the samples with A,B,C three kinds of particles,those with C particles have the most harmless and less harmful pores,followed by the samples with B and A particles,but samples with A particles have the most harmful pores,then is the samples with B and C particle size.