Evaluating the thermal performance of waste-enhanced compressed earth blocks compared to conventional masonry in extreme heat using a modified ASTM C1363 method

In the context of increasing urban climate challenges and building sector energy demands, this research investigates the thermal conductivity of waste-enhanced compressed earth blocks (CEBs) compared to conventional masonry units under extreme heat conditions typical of Gulf Cooperation Council (GCC) regions. Ten CEB formulations incorporating up to 30% industrial and plastic waste materials—including polyethylene terephthalate (PET), hydrated lime (HL), steel slag, and polypropylene (PP)—were evaluated against autoclaved aerated concrete (AAC) and concrete masonry units (CMU) benchmarks. A custom-designed hot box apparatus based on modified ASTM C1363-24 protocol was used to assess dynamic thermal response of full-scale wall panels through 29-hour heating-cooling cycles, complemented by steady-state Heat Flow Meter (HFM) measurements. Results demonstrated that CEBs incorporating PET or HL achieved superior insulation, with low decrement factors (0.24-0.29) and environmental chamber temperatures approaching AAC performance, indicating effective thermal damping. Conversely, steel slag and PP blends exhibited higher thermal conductivity, elevated decrement factors (0.60-0.61), and diminished insulation capacity. HFM testing confirmed these trends, with PET-enhanced CEBs achieving thermal conductivity values (0.23 W/m·°C) comparable to AAC (0.14 W/m·°C). These findings demonstrate that strategic integration of selected waste materials in CEBs provides a viable pathway toward thermally efficient and environmentally sustainable construction in hot climates, reducing cement consumption while enhancing building envelope performance and occupant thermal comfort. • Modified ASTM C1363 hot box simulates realistic hot climate diurnal conditions • Ten waste formulations tested: PET and HL outperform steel slag and PP blends • Dynamic testing reveals transient thermal metrics critical for hot climates • CEBs with 30 % PET show thermal conductivity of 0.23 W/m.°C, near AAC levels • Dual-method validation confirms performance across dynamic and steady-state tests