Elevated Temperature Performance of Multiple-Blended Binder Concretes

Abstract

Concretes that contain binary-blended binders (BBB) and ternary-blended binders (TBB) incorporating thermally activated alum sludge ash (AASA), silica fume (SF), ground-granulated blast-furnace slag (GGBS) and palm oil fuel ash (POFA) are exposed to temperatures as high as 800 °C. The water-binder ratio of the multiple-blended binder (MBB) concretes was 0.30, and the total binder and polypropylene (PP) fibre contents were 493 and 1.8 kg/m 3 , respectively. The elevated temperature performance of the MBB concretes is evaluated in terms of the mass loss, compressive strength, ultrasonic pulse velocity (UPV) and surface cracks. The concrete strength deteriorated significantly due to elevated temperature up to 800 °C, but the residual strength of the BBB containing 15 % AASA was higher than that of the control and 20 % AASA concretes. Hightemperature exposure decreased measured UPV values. The concrete weight loss was more pronounced for TBB concretes. The elevated temperature performance of all of the TBB concretes was better than that of the BBB concretes with the same AASA replacement levels. It was observed that PP fibres help reduce spalling. BBB concrete containing 15 % AASA combined with either SF or GGBS or POFA exhibits superior performance at elevated temperature than Portland cement concrete at the same mix design proportion.

Effect of Elevated Temperature on Compressive Strength and Physical Properties of Neem Seed Husk Ash Concrete

“…An average strength loss of 70% was observed for concrete containing NSHA which deteriorated severely up to 800 • C due to the decomposition of C-S-H gel. Such an observation has been reported in previous studies [21,38].…”

“…Such a decrease in mass loss may be attributed by the dense matrices of the NSHA concrete, as compared to the mix which does not contain NSHA, as the mass loss is caused by air voids associated with the loss of free and bound water from the paste. Similar findings were previously reported [21,34]. Greater mass losses were observed for all batches considered at a temperature of 800 • C, which may be attributed to the evaporation of total absorbed and adsorbed water from concrete as it was also observed by Ramesh et al [35].…”

“…At a temperature of 600 • C, cracking and spalling were observed and they became widely noticeable at 800 • C. The spalling behavior is associated with the generated pore pressures and growth of cracks, which in turn are affected by the rate of heating and the composition of the heterogeneous concrete. A similar observation was observed in previous work by Owaid et al [21]. This suggests that the maximum safe temperature of 400 • C can be attained when NSHA admixtures are incorporated in concrete, though the behavior of concrete at temperatures between 400 • C and 600 • C might be considered for future works to be sure of the threshold temperature.…”

“…After cooling, samples were then weighed again and observed for any spalling that might have occurred during the heating process. The recorded weights were then used to determine overall mass loss at each temperature similar to previous studies [21]. Their residual compressive strength was measured using the Compressive Strength Testing Machine with maximum load capacity 3000 kN with a loading scale of 5 kN per division.…”

“…It is therefore essential to investigate the properties of blended concrete to have a clear knowledge of the emerging materials before they are incorporated in concrete production. Since many factors like age of concrete, the inclusion of pozzolanic materials and the type of aggregates used all together influence the strength and macro properties of concrete at elevated temperatures; it is, therefore, important to examine the residual compressive strength for concrete under such exposures for structural safety [21]. A good number of available studies concentrated on assessing the influence of exposure time, the methods of cooling and loading behaviors on the mechanical properties of concrete and incorporating the processed pozzolanic materials from agro wastes like rice husk ash [22,23], palm oil fuel ash [5], bamboo ash [24] and sugar cane bagasse ash [12] subjected to elevated temperatures.…”