• Allen, G. C.
• Ball, Richard J.
• Ferreira, V. M.
• Labrincha, João A.
• Ribeiro, M. J.
• Senff, L.
• Rajamma, Rejini

Abstract

Cement pastes and mortars were prepared by replacing ordinary Portland cement with different dosages<br/>of biomass fly ashes (0, 10, 20 and 30% BFA) whilst in dry condition. The effect of BFA on the flow<br/>behaviour (spread on table and rheology), setting time, temperature of hydration and electrical resistivity<br/>was studied in this experimental research. Increasing the amount of BFA in the compositions required<br/>extra dosage of water, as a result of particles fineness, tendency for agglomeration and retention/absorption<br/>of water molecules. As a consequence, the relative amount of free water diminishes and the<br/>flowability is poorer. The introduction of BFA also led to an increase in setting time, while the resistivity<br/>obtained from the impedance measurements tends to be lower than the reference paste (ash-free). The<br/>higher concentration of mobile species in the pore solution, namely sodium ions introduced by the ash,<br/>explains that tendency. The hydration temperature of cement pastes tends to decrease with the level of<br/>cement to ash replacement. Between the two tested ashes (from grate and fluidized sand bed furnaces),<br/>differences in particle size and shape, in the amount of residual organic matter and concentration of<br/>inorganic components define minor changes in the workability and setting behaviour. Therefore, the<br/>introduction of biomass fly ashes affects the hardened state features but do not compromise them.

Topics

• impedance spectroscopy
• pore
• resistivity
• Sodium
• cement