Study On The Influence Of Rubber Powder And Cellulose Ether On The Dry Shrinkage Of Hardened Cement Paste

With the development of mortar recent years, the influence of re-dispersible polymer powders andcellulose ethers, as two important chemical admixtures in the mortar, on the properties of the commercialmortar has attracted many scholars. It has been found that although the dosage of chemical admixtures inthe mortar is small, it will have a significant impact on the performance of the mortar. However, in theexisting research, people paid little attention to polymer powders and cellulose ethers’ influence on waterloss, shrinkage deformation, recoverability, crack resistance and other aspects of cement stone. Under thissituation, this paper analyses the water loss shrinkage deformation of the cement stone on the impact ofpolymer powders and cellulose ether of the dehydration of cement, as well as the water absorption andexpansion process after dried for35days. re-dispersible polymer powders and cellulose ethers are theorganic matter, we carried out infrared spectroscopic analysis to the cement stone under different mix ratiosof re-dispersible polymer powders and cellulose ethers, and analyzed the variations of functional groups;while studying the free dry shrinkage deformation of harden cement stone, we researched into its crackresistance under certain restrict conditions; we also studied on the deformation of cement stone which ismixed with fly ash as well as either of re-dispersible polymer powder and cellulose ethers, analyzed thedeformation of cement stone when changing the water-cement ratio and procured period. Through thestudies, we find that:1.In the cement, with the increment of re-dispersible polymer powder dosage, the drying shrinkage ofhardened cement increases, water loss reduces; when re-soaked after dried, the expansion and deformationof the cement become bigger with increase of mix amount of re-dispersible polymer powder, while itswater absorption decreases. However, the formation of the latex film formed from polymer powder isreversible. This is due to the polymer powder in the cement form the elastic membrane, and the membranecan reduce the lost and absorb of moisture in the cement. Infrared spectroscopy with over cement stonelearned that due to the latex powder containing carbonyl, carbonyl in a damp environment, hydrolysis ofthe polyol, the polyol will dehydration in a dry environment carbonyl, the polymer powders to produceshrinkage is fully reversible. Latex film is an elastic membrane, and decreased with the increase of latexpowder content, the elastic modulus of hardened cement, flexible enhanced, the crack resistance of the hardened cement increases. Especially when the latex powder content increased to6%, the latex film isrelatively complete in cement, and after that the cement crack resistance increases much faster.2. With the increasing of cellulose ether content in cement stone, water loss and water absorption ofgradually increase more, while the contraction and expansion rate change little. The incorporation ofcellulose ether can slow the hydration of the cement, thus it leads to the increase of free water and adsorbedwater in the cement, and the decrease of gel water, structural, water and other forms of water. Theformation of the cellulose ether in the cement The structure retains water, increase of free water in thecement shrinkage contributes small. Drying shrinkage of cement increases play a small role, coupled withthe cellulose ether with the hydration of cement out of the product combination, making it smaller impacton the shrinkage of cement. Because the cellulose ether in the cement will form a grid rigid structure, withthe increasing of cellulose ether content, the modulus of elasticity and rigidity of harden cement stoneincrease, and the crack resistance increases.3. When the polymer powder and cellulose ether mixed with the cement in the different ratios, throughthe analysis of linear regression, we can find that both have slight interaction on the deformation and waterloss of cement stone, and the interaction of water loss is a litter more than that of deformation, bothinteraction of cement stone shrinkage and expansion that there was no interaction, but the presence of bothwater loss and water absorption of cement interaction, and this interaction is not a large impact on the crackresistance of cement.4. The low of the influence of fly ash on the effects of polymer powder and cellulose ether is studied,and the mechanism is analyzed. The content of fly ash is30%of the total cementing materials, and itsmixture will decrease the shrinkage and expansion of cement stone, and increase water loss and waterabsorption. When mixing with fly ash, the effect of cellulose ether will be strengthened in the water lossand absorption, as well as the shrinkage and expansion of the cement stone. It is due to that it fines the poreof hardened cement.5. The low of the influence of the ratio of water and cement on the effects of polymer powder andcellulose ether is studied, and the mechanism is analyzed. When water-cement ratio is reduced, the effectof the polymer powders will become weak on the shrinkage, expansion, water loss and absorption; but theimpact of cellulose ether will be changed weaken on the shrinkage and. The less the ratio of water and cement, the more marked the influence of the content of polymer powder on the crack resistance ofhardened cement is.This paper studies the interactions of re-dispersible polymer powders and cellulose ethers and theimpact on water loss and shrinkage, water absorption and expansion, as well as the crack resistance. At thesame time, it also researches into the impacts when mixed with fly ash and when the water-cement ratiochanges.