Drying shrinkage characteristics and mechanism primary exploration of MgO-slag mortars

In this work, seven groups of MgO-slag mortars and pastes were prepared with different MgO types and MgO contents. The setting time, compressive strength and drying shrinkage were characterized. The mechanism of drying shrinkage was discussed by means of microscopic test XRD, FT-IR, MIP and SEM-EDS. The results show that the setting time decrease with the increase of MgO activities and contents. The high-activity MgO only shows a higher compressive strength advantage in the early stage, and the higher content of S-MgO, the higher the compressive strength advantage in the later stage. The 120d drying shrinkage first increases and then decreases with the increase of S-MgO contents, and the maximum drying shrinkage is obtained when the S-MgO content is 15%. The drying shrinkage of the mortar mixed with M-MgO is about half of the mortar mixed with S-MgO; the mortar mixed with R-MgO shows expansion change. Intraparticle porosity, interparticle porosity, and MgO particle size are important factors that affect the drying shrinkage of MgO-slag mortars. This study will provide the theoretical basis for the preparation of cementing materials with no length change by using a MgO activator.

Automated summary

This study investigates the effects of different types and contents of MgO on the properties of MgO-slag mortars and pastes, as well as the mechanism of drying shrinkage. The results show that increasing MgO activities and contents can decrease the setting time and increase the compressive strength. The compressive strength advantage of high-activity MgO is mainly seen in the early stage, while higher contents of S-MgO exhibit higher compressive strength advantage in the later stage. Additionally, the study finds that intraparticle porosity, interparticle porosity, and MgO particle size are important factors affecting the drying shrinkage. These findings provide valuable insights for the preparation of cementing materials with no length change using MgO activator.