ABSTRACT
The management of Waste-to-Energy Bottom Ash (WtE-BA), generated during the incineration of waste, poses a global challenge. Presently, the majority of WtE-BA is disposed of in landfills due to the lack of alternatives. Meanwhile, the construction industry remains the primary consumer of raw materials and significantly contributes to Greenhouse Gas Emissions. This study attempts to address these issues by utilizing the fine fraction of WtE-BA (<2 mm) as a raw material for aerated mortar production. Thanks to its metallic aluminum content, WtE-BA is utilized as an aerating agent. The study investigates how the quantities of water and WtE-BA, as well as its granulometric sub-fractions, impact the properties of the final product. An analysis of properties such as density, compressive strength, and thermal conductivity was conducted. Additionally, the environmental impact of each raw material (i.e. WtE-BA, cement and sand) was assessed through leaching tests and elemental content analysis enabling the determination of their individual contribution to the presence of trace elements in the produced mortars. The aforementioned properties are discussed using microstructure and porosity analyses. The findings demonstrate that the quantity of water is a crucial factor in controlling the aeration of mortars, whereas the granulometry of the WtE-BA particles did not significantly affect their macro-properties. Furthermore, this study highlights that WtE-BA based mortars has the potential to exhibit better environmental and insulating performances than standard aerated mortar of equal density and strength. The differences in pore size and type between WtE-BA and aerated mortars can account for the variation in performance. Thus, WtE-BA proves to be an effective substitute for aerating agent in the production of aerated mortars.
Subject(s)
Coal Ash , Incineration , Environment , WaterABSTRACT
The objective of this study is to determine the influence of recycled glass powder (GP) on the physico-mechanical behavior and durability of a ternary cementitious binder containing calcined clay_metakaolin (MK) or rice husk ash (RHA). Different mortars were produced and characterized in fresh and hardened states. Reference mortars were produced using 100% cement CEM II/B-L 42.5R and 70% CEM + 30% MK or RHA. Test mortars were produced with the substitution of the MK or RHA with the GP and keeping the rate of the substitution at 30%; i.e., in ratios of 20:10, 15:15, and 20:10 of MK/RHA:GP. The water/binder weight ratio was maintained at 0.5, and the consistency of all mortars was adjusted using an admixture (superplasticizer/binder weight ratio of 0.75%). The substitution of MK and RHA with GP reduces the water demand to achieve the normal consistency of pastes and therefore increases the workability of mortars containing both binders CEM+MK+GP and CEM+RHA+GP. The substitution of MK and RHA with GP slightly reduces the compressive strength for both binders. The water-accessible porosity slightly increases for the substitution of MK and reduces for the substitution of RHA with GP. The mass losses after acid attack slightly increase with the substitution with GP, lower for the MK than the RHA up to 15% GP, but it remained far below that of 100% CEM. The results show that the substitution of MK and RHA with GP can improve the physical properties and durability of the mortars compared with that of 100% CEM, but it slightly decreases the mechanical properties due to the low rate of the pozzolanic reactivity of the GP. Further studies should seek to understand the reactivity behavior of the GP at the microstructure scale and therefore improve the mechanical performance of GP based mortar.
ABSTRACT
This study explored the pozzolanic reactivity of granite powder (GP) and its influence on the microstructure of cement paste. An analysis of the physical properties (water demand, setting time, heat of hydration and total shrinkage), compressive strength and durability indicators (water absorption, porosity, acid attack and chloride ions diffusion) was carried out on mortar containing 10%, 15% and 20% of GP as partial substitution to cement (CEM I 42.5 R) in the short and long term. The results showed that the GP does not exhibit pozzolanic reactivity and that it reduces the heat of hydration. Water demand and setting time were not affected by the GP. The compressive strength decreases with increasing the content of GP; but in the long term, the compressive strength was not affected for 10% GP substitution. The presence of granite powder in mortar induces an increase in porosity, which led to an increase in the diffusion properties of fluids (capillary water absorption and chloride ions diffusion).