Alkali-activated cements and mortars based on blast furnace slag and red clay brick waste

• Red clay brick waste is a physically and chemically active polymineralic additive.
• Red clay brick waste strengthens alkali-activated slag cement and can substitute for up to 60% of the slag.
• The introduction of 40% red clay brick waste to alkali-activated slag cement improves its compressive and flexural strength.

This study investigates the effects of adding various concentrations, sources and compositions of ground red clay brick waste (RCBW) on the properties of fresh and hardened pastes and mortars of alkali-activated slag. The method used to grind the granulated blast furnace slag (GBFS) and RCBW (separate and conjoint) is also assessed, along with the fineness (300–900 m2/kg) of the blended alkali-activated GBFS-RCBW cement, the alkali activator (sodium carbonate or sodium silicate) and the curing conditions (normal conditions or steam curing). The water requirement and setting time for the fresh pastes are also considered; and in the case of the hardened paste and mortar, the water absorption, density and compressive/flexural strength are measured after 1, 3, 7 and 28 days of aging. From the results obtained, it is demonstrated that the addition of 40% RCBW improves the 7- and 28-day strength of blended alkali-activated slag pastes and mortars, and can replace up to 60% of the slag without losing strength.

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