Design and performance evaluation of ultra-lightweight geopolymer concrete

This article presents the development of a sustainable ultra-lightweight geopolymer concrete (with a dry density = 800 kg/m3) for both thermal insulating and load bearing purposes. A predesigned mineral precursor resulted from industrial by-products is used as the raw material for alkali activation and NaOH with a low concentration of 2–3 M is used as the alkali activator, together with a specially designed additive as superplasticizer. The ultra-lightweight property is achieved by applying a waste glass produced expanded lightweight material as aggregates. The effects of influential parameters including the design approach, liquid/binder ratio, binder/aggregate ratio, particle size and air entraining agent on the properties of the designed concrete are evaluated. An ultra-lightweight concrete with a proper workability is obtained and the hardened concrete shows excellence performances in terms of mechanical property, thermal property and durability. At a moderate compressive strength (10 MPa), an excellent thermal conductivity of 0.11 W/(m·K) is resulted. Furthermore, a very low thermal conductivity of 0.07 W/(m·K) is reached at a compressive strength of 8 MPa, indicating great potential for the production of a load bearing and highly insulating building material as an alternative for the traditional materials