Mechanical properties and thermal conductivity of lightweight geopolymer concrete

Geopolymer concrete can be considered as the key factor which does not utilize Portland cement, nor releases green house gases. With the increasing use of lightweight concrete in precast products for construction, there is a need for a better production of new lightweight concrete that has more effectively design and optimize the characteristics of precast products. It has been found in this investigation that locally artificial lightweight aggregate can be used to produce lightweight fly ash geopolymer concrete. Four concrete mixtures were prepared with artificial coarse lightweight aggregate and different contents of artificial lightweight fine aggregate (25, 50, 75 and 100%) as a volumetric replacement to natural normal weight fine aggregate (sand); in addition to reference lightweight geopolymer concrete (LWGPC) containing natural normal weight fine aggregate. Properties of lightweight geopolymer concrete including, compressive strength, flexural strength, splitting tensile strength, thermal conductivity, and ultrasonic pulse velocity were investigated. The results show that the replacement of natural normal weight fine aggregate by 25, 50, 75 and 100% artificial fine lightweight aggregate leads to a decrease in compressive strength relative to the reference LWGPC at 28 day age, the compressive strength is 32.60, 30.73, 30.56, and 28.73 MPa, beside it has a low thermal conductivity of 0.925, 0.825, 0.658, and 0.620 W/m.K respectively which remains the concrete ideal for structural requirements.