AN EXPERIMENTAL INVESTIGATION ON INCORPORATION OF FINE AGGREGATE WITH GLASS POWDER AND CEMENT WITH ZEOLITE TO MITIGATE THE URBAN HEAT ISLAND EFFECT: A REVIEW

The urban heat island effect, characterised by systematically elevated air and surface temperatures in built-up areas relative to their rural surroundings, has become one of the most pressing environmental challenges facing rapidly urbanising tropical cities. Concrete and cementitious pavements, which constitute a dominant fraction of the exposed urban fabric, contribute through their comparatively low solar reflectance, high volumetric heat capacity and high thermal conductivity, which together promote daytime heat storage and nocturnal re-radiation. Concurrently the construction sector faces mounting pressure to reduce embodied carbon and dependence on natural river sand. This review consolidates the published evidence on two complementary interventions: partial substitution of fine aggregate with waste glass powder (WGP) and of ordinary Portland cement with natural zeolite. Literature spanning mechanical, thermal, optical, durability and microstructural characterisation is synthesised through comparative tables and graphical trend analyses. The evidence indicates that WGP substitution at 15–20 % of fine aggregate raises surface albedo, marginally improves 28-day compressive strength and reduces thermal conductivity, while natural zeolite at 10–15 % cement replacement refines pore structure, consumes calcium hydroxide, suppresses the alkali–silica reaction (ASR) risk associated with glass, and further lowers conductivity through its intrinsic cage porosity. The combined system exhibits genuine complementarity: the zeolite mitigates the principal durability liability of the glass, while the glass compensates for the early-age strength penalty of the zeolite. Reported and projected data suggest peak slab surface temperature reductions of 5–8 °C and conductivity reductions of up to 30 % relative to a control mix. The review closes by identifying the principal research gaps — most notably the near-absence of studies examining the two materials in combination under field-representative thermal loading — and proposes a four-phase experimental programme to address them.