Mechanical and physical performances of concretes made from crushed sands of different geological nature subjected to high temperatures

Effects of Combined Usage of Supplementary Cementitious Materials on the Thermal Properties and Microstructure of High-Performance Concrete at High Temperatures

“…Typical reflections associated with larnite (C 2 S), portlandite (CH), ettringite (AFt), calcite (CaCO 3 ), brown millerite (Ca 4 Al 2 Fe 2 O 10 ) and lime can be found in the reference specimen, as shown in Figure 6a. Some reflections (AFt) disappeared after heating, this could be attributed to the decomposition of AFt after heating to 70 • C, similar results have been obtained by Molay et al [2] and Rashad et al [29]. Up to 400 • C, a progressive reduction of the intensity of the peak of portlandite was obtained, which disappears at 800 • C. Previous research work by Alonso et al [6] obtained a similar observation that the CH crystal began to decompose between 350 • C and 600 • C. The brownmillerite was found in all samples and the same for larnite.…”

“…Calcite could be found in the specimens and even increased in intensity up to 400 • C. Additionally, reflection peaks of calcium aluminum oxide appeared in HPC-2 and HPC-4 mixtures after heating. This could be attributed to the water from the decomposition of hydration products let to rehydrate the anhydrous cement particles [2], which increased the residual strength of concrete at 400 • C. Similar results have been reported by Wang et al [8]. Figure 7 shows the variations of the DTA thermograms of reference concrete, HPC-2 and HPC-4 at RT and high temperatures.…”

“…High-performance concrete (HPC) has been extensively used in ultra-high and ultra-large building structures owing to its high strength and excellent durability [1,2]. However, HPC is extremely vulnerable when subjected to high temperatures due to its low porosity, low permeability and compact microstructure.…”

“…Supplementary cementitious materials (SCMs) contribute to improve the performance of concrete at high temperatures owing to their pozzolanic effects and super micro-filling capacity [14]. Furthermore, the residual unhydrated cementitious materials particles, such as: cement, activated slag [7], FA [14] and MK [7,15] can further react with water, which mainly comes from the vaporization of moisture [2] and dehydration of calcium hydroxide (CH), leading to the formation of dense hydration products [16][17][18].…”

“…This compound makes it possible to improve the high-temperature resistance of HPC containing SCMs subjected to high temperatures. The increasing application of various types of SCMs in concrete makes the high-temperature resistance of HPC even more complex [2,4]. Therefore, the studies of high-temperature resistance of concrete containing SCMs become an urgent issue.…”