High-volume rock wool waste blended cements

Significant quantities of rock wool wastes (RWW) are produced globally, resulting in environmental concerns regarding their disposal in landfills and leaching. The concrete industry presents a common approach for recycling and reusing RWW. According to ASTM C618 RWW is classified as pozzolanic and is suitable for use in cement-based mixes. The chemical composition of RWW is similar to pozzolanic materials, resulting in its use as supplementary cementitious materials (SCMs) in concrete mixes and precursors for alkali activation. As SCM, RWW has been studied extensively in the laboratory in the range of 0%–40% cement replacement by mass. Increasing the RWW content in the mixes reduces carbon emissions, costs, and compressive strength. Considering strength, 10% RWW content yields the lowest carbon intensity and cost intensity. RWW-based AAMs can significantly reduce CO2 emissions, energy consumption, and costs. Depending on the activator employed, C-(N-)A-S-H gel is the primary reaction product. This chapter reviews the inherent properties and usability of RWW in construction materials, including: (1) the manufacturing process of rock wool and its wastes, (2) activity estimation and quality assessment (physical and chemical compositions) of RWW, (3) properties of RWW-blended cements at both fresh and hardened stages, (4) use of RWW in alkali-activated materials (AAMs) and (5) associated environmental impact and cost evaluation.