The influence of calcium lignosulphonate–sodium bicarbonate on the status of ettringite crystallization in fly ash cement paste

• Published in: Cement and concrete research Vol. 32; no. 1; pp. 51 - 56
• Main Authors: Kerui, Yang, Caiwen, Zhang, Zhigang, Liu
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Ltd 2002; Elsevier Science
• Subjects: Analysis of cement phases and constituents; Applied sciences; Buildings. Public works; Calcium lignosulphonate–sodium bicarbonate; Cement concrete constituents; Cement paste; Cements; Ettringite; Exact sciences and technology; Hydration; Materials; Properties of anhydrous and hydrated cement, test methods; Rheology; Ettringite; Rheology; Calcium lignosulphonate–sodium bicarbonate; Cement paste; Fly ash; Scanning electron microscopy; Hydration; Differential thermal analysis; Chemical composition; Experimental study; X ray diffraction; Rheological properties
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/S0008-8846(01)00628-7

Calcium lignosulphonate (CL)–sodium bicarbonate (SB) (a total of 0.7% by weight of cement and CL to SB ratio of 1:1.8) will cause the fluidity of fly ash cement paste to decrease rapidly. It is the variation of the status of ettringite crystallization that causes this phenomenon. Experimental results show that CL–SB affects the liquid-phase composition of fly ash cement paste remarkably. As a result, ettringite crystallizes out in the shape of needles from the solution. These needle-like crystal particles are distributed in the solution at a certain distance from the surface of clinker particles. At the initial hydration stage, the crystallization of ettringite is stronger in fly ash cement with calcined gypsum than in fly ash cement with gypsum.