Abstract
This paper is part of a wide-ranging investigation on the use of flue gas desulphurisation (FGD) waste in cement-based materials. It reports the results on the porosity and pore size distribution of cement paste containing varying amounts of simulated FGD waste. The water to binder ratio was 0.5. The binder consists of cement and simulated FGD. The FGD is a combination of fly ash and gypsum ranging from 0% to 100%. Cement in the pastes was partially replaced with 25% FGD (by weight). The porosity and pore size distribution of cement pastes was determined during the early stage of hydration. Increasing the amount of gypsum does not increase the pore volume. However, increasing the amount of gypsum in the paste leads to an increase in the threshold diameter and a decrease in the percentage of small pores in the paste, both indicating a coarser pore structure. The results of this investigation were compared with data at longer curing periods.
Highlights
The coal power industry generates a substantial amount of waste worldwide
The total pore volume (TPV) of the fly ash (FA)-G blended pastes (P2ÁP8) tends to be higher than that exhibited by the reference paste (P1)
Pastes P2 and P3 which contain the highest amount of fly ash in the FA-G blend (100% and 95%, respectively) record the highest TPV
Summary
The coal power industry generates a substantial amount of waste worldwide. Large amounts of harmful gases such as CO2, SOx and NOx are emitted into the atmosphere, causing environmental problems. This optimum FGD composition represents an SO3 content of 8.87% It corresponds to siliceous and pozzolanic active fly ashes of SO3 content under 10% obtained from dry and semi-dry flue gas cleaning processes at many power plants in Europe. Introducing FGD waste material into concrete will affect its properties and performance These include porosity and pore size distribution. If FGD wastes residues are to be used in construction materials such as concrete, the basic properties of concrete containing these wastes need to be determined Among these properties are the porosity and pore size distribution. This paper is part of a wider investigation on the use of FGD wastes in concrete applications It reports the results on porosity and pore size distribution of pastes containing simulated FGD at the age of 1 day of curing (i.e. during the early age of hydration). Simulated FGD was a combination of fly ash and gypsum. Mangat et al (2006) showed that FGD can be simulated by mixing different combinations of fly ash and gypsum
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