HEAT STRESS EFFECTS ON CONSTRUCTION LABOUR PRODUCTIVITY IN HOT SEASONS: A CASE STUDY OF REBAR AND MOULDING WORKERS IN CAMBODIA

This study investigates the impact of heat stress on construction labour productivity (CLP), the Perceptual Strain Index (PeSI), and work intensity among rebar and moulding construction workers in Phnom Penh, Cambodia. Thirty-four healthy workers aged 18 to 54 volunteered during the hot months from March to June 2023. Heat stress was measured using the Wet Bulb Globe Temperature (WBGT) collected on-site. Physiological responses, such as heart rate, were monitored. The percentage of maximum heart rate (%HRmax) was computed to determine the work intensity. Perceptual responses were measured using PeSI. CLP was measured by observing the direct work productivity of participants. CLP was then quantified as the percentage of time participants/workers dedicated to direct tasks. ANOVA and correlation were applied for analysing the effect of WBGT on CLP, PeSI, and %HRmax. Results indicate that higher WBGT levels significantly reduce construction labour productivity (Pr = 1.1e-06). The average CLP declines from 74% to 48% as WBGT increases from 26℃ to 35℃. Heat stress is significantly positively correlated with PeSI (r = 0.466, Pr = 2e-16)) and %HRmax (r = 0.247, Pr = 4.78e-12), indicating increased heart rates and perceived strain with rising temperatures. Despite stable physical effort, productivity declines due to physiological or psychological factors linked to heat exposure. These findings suggest that workers' perceived exertion intensifies as risk of heat stress increase, negatively impacting well-being and productivity. This study provides valuable insights into the challenges faced by construction workers during Cambodia’s hot months and emphasises the need for strategies to mitigate heat-related impacts and enhance productivity in the construction sector.