Early age strength increase of fly ash blended cement by a ternary hardening accelerating admixture

• Published in: Cement and concrete research Vol. 81; pp. 59 - 69
• Main Authors: Hoang, Kien, Justnes, Harald, Geiker, Mette
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.03.2016
• Subjects: Accelerating admixtures; Acceleration; Admixture; Admixtures; Age; ATOMIC FORCE MICROSCOPY; Blended; Cement; CEMENTS; FLY ASH; HARDENING; HYDRATES; HYDRATION; MATERIALS SCIENCE; SODIUM SULFATES; Strength; THERMAL GRAVIMETRIC ANALYSIS; X RADIATION; X-RAY DIFFRACTION; Fly ash; Hydration; Acceleration; Admixture; Cement
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2015.11.004

The applicability of a combination of sodium thiocyanate (NaSCN), diethanolamine (DEA) and glycerol (Gly) with small dosages as a ternary hardening accelerating admixture for fly ash blended cement (OPC-FA) was studied. The ternary admixture induced higher early and later age mortar strength at both low (5°C) and normal (20°C) temperature. Despite used in lower dosage the ternary admixture led to higher strength of the investigated OPC-FA system than other chemicals (e.g. sodium sulfate). Results obtained from isothermal calorimetry, thermogravimetric analysis (TGA) and X-ray diffraction (XRD) showed that the ternary admixture accelerated the cement hydration and increased the amount of AFm (notably calcium hemicarboaluminate hydrate) in the hydration products. A synergistic effect between the three components of the accelerator on the hydration of OPC-FA system was observed.