Research On Shrinkage-control Of Polymer-modified Mortar

Polymer modified mortar is a new trend of cement-based mortars. A great deal of research has been carried on this area home and abroad, such as the type and the mechanism of polymer, and their impact on the performance of mortar, and so on. Although some of the research involved the shrinkage of polymer-modified mortar, how to control the shrinkage is less-mentioned. Self-leveling mortar, which is a representative polymer modified mortar, is new material widely using. The quality of the ground material is directly related to the shrinkage of the mortar, and this kind of research is almost empty.In this article, experimental study and theoretical analysis were focused on the shrinkage-control of self-leveling mortar. The impact of the shrinkage reducer and the expansion agent on the ordinary cement mortar was studied at first, the shrinkage performance and shrinkage-control using shrinkage reducer and expansion agent of self-leveling mortar were analyzed quantitatively then. The impact on the shrinkage and other performance of the mortar with the admixtures using alone and together was discussed, and mechanism was studied. The research results can be concluded as follows:The shrinkage reducer and expansion agent using alone and together can effectively reduce the shrinkage of both self-leveling mortar and ordinary cement mortar. A synergistic effect on the shrinkage reduction was observed when the shrinkage reducer and the expansive agent were used together.From the mechanical properties, the shrinkage reducer and expansion agent had little impact on the flexural strength. The compressive strength of 28-day of the self-leveling mortar and ordinary cement mortar declined about 10% and 7% when shrinkage reducer was used alone and two admixtures were used together, respectively; expansion agent had little impact on compressive strength of mortars.The shrinkage of the mortar was reduced using the admixtures, and other properties can meet the criterion well at the same time. Comprehensively consider the reducing effects and other performance of the mortars, the amount of the shrinkage reducer and expansion agent was 1.5% and 8%.XRD test results showed that the formation of the ettringite was in early age, so the major expansion occurred at the time. The shrinkage compensation from expansion agent in mortar was almost the same as in concrete. Mesh membrane that is formed from polymer can be scanned according to SEM test. This kind of membrane plays a facilitating role to the shrinkage compensation of the expansion agent.