Abstract
Structural lightweight concrete (LWC) has recently acquired research importance because of its good thermal insulation properties. However, there is a lack of knowledge about its thermal properties at elevated temperatures. The thermal properties, such as thermal conductivity and specific heat, of porous LWC vary depending on the aggregates, air voids, and moisture content of the LWC in question. To study these effects, in this paper, we measured the thermal properties of three types of structural LWCs at different temperatures, combining different characterization techniques, namely, differential scanning calorimetry (DSC), laser flash analysis (LFA), and modified transient plane source (MTPS). Bulk density and porosity were also evaluated. Specific heat is analyzed by the DSC technique from 20 to 1000 °C and the MTPS technique from 20 to 160 °C. Thermal conductivity is studied using MTPS and LFA techniques at temperatures ranging from 20 to 160 °C and 100 to 300 °C, respectively. The results indicate that the thermal properties of LWC are highly affected by moisture content, temperature, and porosity. For LWC, the current Eurocodes 2 and 4 assume a constant value of specific heat (840 J/kg°C). This research reveals variability in temperatures near 150, 450, and 850 °C due to endothermic reactions. Furthermore, for low temperatures, the higher the porosity, the higher the thermal conductivity, while, at high temperatures, the higher the porosity, the lower the thermal conductivity. Thus, Eurocodes 2 and 4 should be updated accordingly. This research contributes to a deeper understanding and more accurate prediction of LWC’s effects on thermal properties at elevated temperatures.
Highlights
Concrete is widely used as a primary structural material in construction due to its numerous advantages, such as strength, durability, ease of fabrication, and non-combustibility [1].Concrete is grouped into different categories based on performance, weight, presence of aggregates [2,3,4], and strength.According to the International Energy Agency (IEA), the current demand for energy is 30% higher than it was in the 1990s [5]
Four tests were performed for each Lightweight concrete (LWC) using the laser flash analysis (LFA) technique, and
Four tests were performed for each LWC using the LFA technique, and the average measurements were calculated
Summary
Concrete is widely used as a primary structural material in construction due to its numerous advantages, such as strength, durability, ease of fabrication, and non-combustibility [1].Concrete is grouped into different categories based on performance (conventional and high performance), weight (normal weight and lightweight), presence of aggregates (fibers, waste materials, and recycles aggregate concrete) [2,3,4], and strength (normal strength, high strength, and ultra-high strength).According to the International Energy Agency (IEA), the current demand for energy is 30% higher than it was in the 1990s [5]. Lightweight concrete (LWC) has been extensively used as both a structural and non-structural building material due to its important advantages, including a longer product life cycle than other construction materials. This type of concrete has low density, excellent behavior at elevated temperatures, and good thermal insulation due to its low thermal conductivity [6,7,8]. To mitigate some of concrete’s environmental problems, LWC has been manufactured using waste from different industries, such as fly ash and blast furnace slag, to substitute components and/or enhance the concrete’s properties [10]
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