Alkali-activated concrete mixes with ground granulated blast furnace slag and paper sludge ash in seawater environments

Abstract

Predicted sea level rise due to global warming will necessitate the construction of coastal defenses to protect the populations in the vicinity of the coasts. Large quantities of concrete will be required with consecutive increases in greenhouse emissions, hence an increasing need for alternative to Ordinary Portland Cement (OPC) cements. Feasible potential alternatives could be found in alkali-activated cements, which also include industrial by-products or waste materials. This paper presents a laboratory study of concrete mixes based on the alkali-activation of an industrial by-product, ground granulated blast furnace slag (GGBFS) and includes an industrial waste, paper slugde ash (PSA) in the alkali-activator mixes. The use of seawater as mixing and curing water was also examined. The compressive strength and a number of durability-related properties of alkali-activated mixes in marine environment were investigated and compared to OPC systems. The incorporation of paper sludge ash led to high early strengths, a decrease in the effective porosity of alkali-activated slag concretes and generally a reduced water absorption, and enhanced the performance against chloride ion attack in mixes with freshwater, as well as the resistance of the cements in sulphate attack especially when mixed with seawater. The addition of seawater in the mixes increased the resistance to sulphate attack and the compressive strength in alkali-activated systems, as opposed to OPC concretes in which mixing and curing in seawater had deleterious effects. The study gives promise for the suitability of the tested alkali-activated concrete mixes in seawater environments.