Effect of sodium metasilicate on the early-age hydration and setting behavior of alkali-activated common cements containing slag

Abstract

The ways to keep under regulation the early-age hydration and setting behavior of the common cements containing slag per EN 197-1:2011 and activated with sodium metasilicate were discovered and the results are discussed. The alkaline activation of these cements using sodium metasilicate is one of the ways to escape the strength loss in the cement systems with blast-furnace slag content of 5… 95 %. However, these cements have too short setting times. This requires finding ways to regulate the structure formation. The aggregate states of sodium metasilicate, thes We were: a liquid state (solution) and a solid state (powder) as well as the admixture-surfactant have been chosen as factors of influence to regulate setting times. The results of the study showed that the use of sodium metasilicate in the liquid state, on contrary to the solid state, provided additional intensification of the structure formation. The acceleration of the structure formation processes was accompanied by the formation of high early (1 day) compressive strength of 43… 54 MPa, associated with an extremely quick setting time of 1… 8 min. The sodium lignosulphonate admixture could be of help: its addition in a quantity of 4 % can retard the structure formation processes to the required ranges, not depending upon the aggregate state of sodium metasilicate. The resulting alkali-activated common cements containing slag are characteristic of the early (1 day) compressive strength of 33… 48 MPa and initial setting time of 38… 50 min.