Slag/diatomite based alkali activated lightweight composites containing waste andesite sand: mechanical, insulating, microstructural and durability properties

Waste andesite sand (AS) is produced when cutting andesite stone and doing other stone dressing procedures. Problems with storage and environmental pollution may result from the disposal of AS. These issues might be resolved using AS in the manufacturing of alkali-activated composites. Pozzolanic powders are used extensively in the construction sector to reduce the need for cement, which lowers the price of making concrete and lessens environmental pollution from CO2 emissions from cement producers. This paper reports the findings of an experimental examination into the impact of diatomite powder and waste andesite sand on the microstructural, durability, and mechanical characteristics of environmental-friendly alkali-activated lightweight composites (AALC). Ground blast furnace slag (GBFS) and diatomite powder (DP) were used as the main solid precursors, silica sand (SS) and waste andesite sand (AS) were used as filers for the design of AALC mixtures. The alkaline activators adopted in this study were sodium hydroxide and sodium silicate. Physico-mechanical characteristics, transport properties, thermal conductivity, sorptivity, and drying shrinkage of generated AALC mixes were also examined in addition to its performance under freeze-thaw (F–T) cycles and high temperatures. SEM analyses of the AALC were conducted to investigate the microstructure of the produced specimens. Sixteen AALC mixtures were created using GBFS/DP ratios of 100/0, 90/10, 80/20 and 70/30 and AS was used to replace silica sand (SS) in four diferent rates of 0%, 25%, 50%, and 100%. Prior to ambient curing, the manufactured samples were cured at 80°C for 24 h to quicken geopolymerization. The findings showed that the mixture with 100% GBFS and 100% AS had a maximum compressive strength of around 60 MPa. When GBFS was replaced with 20% and 30% DP, the compressive strength of AALC specimens was drastically reduced. The AALC mixtures containing 20% and 30% DP showed the lowest thermal conductivity results. The best high-temperature resistance was demonstrated by the mixture D20A50, which comprises 20% DP and 50% AS and experiences a strength loss of 20.7% at 900 C. The best resistance to freezing and thawing exposure was found in mixtures that contained 10% DP and 50% AS.