A preliminary study of alkali-activated slag blended with silica fume under the effect of thermal loads and thermal shock cycles

• Published in: Construction & building materials 2013-03, Vol.40, p.522-532
• Main Authors: Rashad, Alaa M., Khalil, Mervat H.
• Format: Article
• Language: English
• Subjects: Activated slag; Analysis; Elevated temperature; Mechanical properties; Portland cement; Relative strength; Residual compressive strength; Silica; Silica fume; Slag; Thermal properties; Thermal shock resistance
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2012.10.014

Slag in alkali-activated slag (AAS) was replaced with silica fume (SF) at levels of 0, 5, 10, and 15-wt.%. Some pastes were exposed to elevated temperatures from 400°C to 1000°C with an increment of 200°C. The others were subjected to thermal shock cycles. The compressive strengths before and after firing were determined. Thermal shock resistance was monitored. [Display omitted] ► The replacement of slag with SF up to 15% improved the compressive strength. ► AAS/SF pastes residual strengths up to 800°C were higher than neat AAS pastes. ► Neat AAS paste residual strength at 1000°C was higher than AAS/SF pastes. ► Neat AAS pastes relative strengths were higher than those of AAS/SF pastes. ► Neat AAS is more efficient to resist sudden thermal shock cycles than AAS/SF. The elevated temperature performance of alkali-activated ground granulated blast-furnace slag/silica fume (SF) at ratios of 100/0, 95/5, 90/10 and 85/15wt.%, activated with sodium silicate is presented. The specimens were exposed to elevated temperatures ranging from 400°C to 1000°C with an increment of 200°C. Compressive strengths before and after firing were measured. Water quenching test was applied to determine thermal shock resistance of various mixtures. The various decomposition phases formed were identified using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectra (EDS). The results indicated that the compressive strengths before and after firing increased with the presence of SF up to 800°C, then decreased at 1000°C in comparison with neat activated slag specimens. The relative strength of the neat alkali-activated slag paste was superior and the inclusion of SF had adversely impact on the thermal shock resistance.