A novel method for solving the impact of clay on concrete workability: dimensional design and mechanism analysis

Abstract

Clay often has severe detrimental impacts on cement-based materials. Therefore, it is necessary to investigate the mechanism causing the deterioration to improve the service life of cement-based materials. Based on accurate dimensional analysis, a mechanism that influences clay is proposed: the intercalation of the side chains of superplasticizer molecules in the interlayer space of the clay. To lessen this harmful effect, a new clay-resistant admixture (CRA) possessing cationic groups of small molecular size was synthesized through a novel dimensional design. The length and width of the side chains of this superplasticizer molecule were 9.50–17.50 and 0.25–0.40 nm, respectively, with a radius of ~3.74 nm in solvent, which is larger than the interlayer spacing of montmorillonite (i.e. 1.09–2.14 nm). The longitudinal and latitudinal lengths of the CRA molecule were 0.468 and 9.456 nm, respectively, ensuring intercalation in the interlayer of montmorillonite. The increase in interlayer spacing of the clay was 0.364 nm following addition of polycarboxylate superplasticizer (PCE) plus CRA and 0.632 nm following addition of PCE, which suggests that the CRA plays the role of a ‘sacrificial agent’ that is preferentially intercalated into the interlayer space of clay to further prevent the side chains of the superplasticizer molecules from entering the interlayer. The aim of this study was to propose a suitable means of synthesizing a new CRA to address the impact of clay through dimensional design and mechanism analysis, which contributes to the theoretical study and technological improvement of cement-based materials.

Synergistic Effect of Polycarboxylate Superplasticiser and Protein Retarders in Cementitious Materials Containing Na- Montmorillonite: Effect of Addition Methods

“…Compared to the development of novel clay-tolerance PCEs, the addition of sacrificial agents, a compound mitigating the interaction between PCEs and clays, in terms of intercalation blockers, clay swelling inhibitors, electrostatic blockers, or combined functionalised agent, has been widely applied due to its cost and ease to be achieved [ 38 ]. Therefore, different chemicals, i.e., polyether, polymeric ferric sulphate, sodium tripolyphosphate, etc., have been borrowed to be the sacrificial agents [ 22 , 26 , 39 , 40 ]. Tan et al [ 22 ] improved the clay tolerance by incorporating polymeric ferric sulphate, which was reported to block intercalation of PCE, but also significantly increased surficial adsorption.…”