A Review of the Utilisation of Hydrated Lime (CL-90) in Engineering Applications and it’s Sustainability Implications

Lime is one of the widely used materials in several industries, with an estimated production of 430 million tons worldwide, with the iron, steel and metal industries as the leader, using 250 million tons, followed by the construction industry using around 75 million tons and the chemical industry with 55 million tons usage per annum worldwide. The broadly used types of lime are quick lime CaO (CL90 Q), hydrated lime Ca(OH)2 (CL90 S), hydraulic lime and lime putty. The primary purpose of hydrated lime is to induce alkalinity and use it as filler material to control porosity. Hydrated lime, unlike hydraulic lime, does not exhibit much-cementing properties on mixing with water. Therefore, it requires blending with suitable binders like cement, pozzolans, and bitumen to acquire better binding characteristics. Hydrated lime is widely used in the iron and steel industry as a cheap, sustainable material for converting iron into pig iron and steel and improving the durability of refractories in the blast furnace. The agriculture and food industry also relies heavily on hydrated lime to be used as a purifying flocculating coagulating agent, especially in the sugar industry. The hydrated lime acts as an alkali activator, deodorising and anti-bacterial chemical in treating wastewater/sludge, agricultural fields and environmental protection. The hydrated lime is used to treat wet, marine and cohesive expansive clayey soils as it absorbs moisture and improves engineering properties like compressibility, strength, plasticity, bearing capacity, consistency, sheer strength and shrinkage etc. One of the main usages of hydrated lime in civil engineering applications is in cementbased mortars as a plasticiser. Therefore, the hydrated lime can be recommended for use in diverse industries and multi-purpose roles.