Effect of incorporating municipal solid waste incinerated bottom ash in alkali-activated fly ash concrete subjected to accelerated CO2 curing

Abstract

The effect of incorporating bottom ash from municipal solid waste incineration (MIBA) as partial replacement for fly ash (FA) (0%, 15% and 30%) was studied on alkali-activated mortars under two curing environments: conventional climatic chamber (∼0.04% CO2) and carbonation chamber (5% CO2). The microstructural characterization showed that the use of MIBA resulted in a decrease of calcium silicate hydrate gel (C–S–H) and sodium aluminosilicate hydrate (N-A-S-H) observed as “rounded growths” worsening the macrostructural behaviour (compressive/flexural strength, ultrasonic pulse velocity, dynamic Young’ modulus, dry bulk density, shrinkage, depth of carbonation and porosity accessible to water). The accelerated CO2 curing stage produced high amounts of aragonite, observed as “needle-like” formations improving the macrostructural behaviour. One tonne of mixture with MIBA and CO2 curing could decarbonise approximately 3695, 7391 and 10163 m3 of air volume at the age of 7, 14 and 28 days. The combined substitution of FA with MIBA and CO2 curing can be a highly viable technique in plain precast products.