Construction engineering Pozzolans lime-pozzolan paste reactivity
R. Walker and S. Pavía , Behaviour and Properties of Lime-Pozzolan Pastes, 8th International Masonry Conference, Dresden, July 2010, W. Jäger, B. Haseltine, A. Fried, 2010, 353 - 362
Lime pozzolan mortars have been used by numerous ancient civilizations of builders, and are now
regaining popularity as environmental sustainable alternatives to cements for masonry and concrete
applications. This paper studies the relationship between the composition and physical characteristics
of nine pozzolans and their corresponding reactivity, water demand, setting times and mechanical
properties in lime/pozzolan pastes. A diverse selection of artificial pozzolans were investigated
including Ground Granulated Blastfurnace Slag (GGBS); Leca; Pulverised Fuel Ash (PFA); Calcined
Clay (MetaStar); Microsilica (MS); Rice Husk Ash (RHA); Red Brick Dust (RBD); Tile and Yellow Brick
Each pozzolan was found to have a particular water demand for a given workabililty that was
related to the particle surface area. It was concluded that the pozzolan surface area has a much
greater influence on the water demand of the paste than its particle size or the lime:pozzolan ratio. It
appears from this research, that the effect of the water content of the paste on the setting times
surpasses the influence of the reactivity of the pozzolans. It was also demonstrated that the particle
size of the pozzolan critically affects the set of the paste, both the coarsest and the finest pozzolans
set the fastest; and there is a critical particle size, ranging between 63 and 250um, for which the set
slows down significantly. Finally, it was also noted that pozzolanic reaction takes place at variable
speed for different pozzolans, and that there can be instances when hydration can be slower than
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