The efficiency of plasticizing surfactants in alkali-activated cement mortars and concretes

Abstract

Functionality of mortar and concrete mixes is regulated by surfactants, which act as plasticizers. The molecular structure of these admixtures can be changed during hydration of alkali-activated cements (AAC). The objective was to determine the chemical nature of plasticizers effective for property modification of mortars and concretes based on AACs with changing content of granulated blast furnace slag from 0 to 100 %. The admixtures without ester links become more effective than polyesters when content of alkaline component increase. The admixtures effective in high alkaline medium were used in dry mixes for anchoring (consistency of mortar 150 mm by Vicat cone; 1 d tensile strength in bending / compressive strength of mortar 6.6 /30.6 MPa) and in ready-mixed concretes (consistency class changed from S1 to S3, S4 with consistency safety during 60 min; 3 d compressive strength of modified concrete was not less than the reference one without admixtures).

Development of solutions concerning regulation of proper deformations in alkali-activated cements

“…This makes it possible to reduce cement shrinkage deformation due to the falling pressure in capillaries and slowing down rate of moisture evaporation. Since most of surfactants are ineffective in a hydration medium of AAC, principles of their selection were proposed for such cements according to the criteria of variation of plastic strength [13], stability of molecular structure of admixtures having plasticizing [21] and other types of action [22] in a high alkaline medium. In this regard, it has been shown that maximum plasticizing effect is enabled by addition of sodium lignosulfonate [23], sodium gluconate [24], polyatomic alcohols and other acyclic low-and high-molecular compounds [13].…”

“…The presented studies [14][15][16][17][18][19][20][21][22][23][24][25] show positive influence of mineral and organic admixtures on reduction of AAC shrinkage, however there is no explanation of the mechanism of their structure formation. This fact limits understanding ways of regulating proper deformations in artificial stone.…”

Development of a technology for utilizing the electroplating wastes by applying a ferritization method to the alkaline­activated materials

“…Previous studies have shown that the main products from hydration of alkaline-activated cements are the C-S-H gel [21], zeolites [22] and hydrogranates [23]. Such a composition of new structures makes it possible to reliably fix the elements of heavy metals in the structure of a material.…”

Studying the influence of metakaolin on self-healing processes in the contact-zone structure of concretes based on the alkali-activated Portland cement

“…The results from experimental research into the "alkaliactive aggregate" reaction, reported by different authors [4], allow us to formulate the basis of the AAR reaction mechanism: -cement itself [5], admixtures to concrete [6], and the external aggressive environment [7] are the sources of alkalis [8];…”