Applicability of Alkaline Waste and By-products as Low Cost Alternative Neutralizers for Acidic Soils

Acidic soils can induce several negative impacts, especially in agricultural fields. To address these problems, lime is often applied to increase the pH value of acidic soils. Calcium carbonate is the most common and conventional agricultural lime; however, it is a natural and scarce resource. To promote a recycling-based society, alternative neutralizers with lower costs that use alkaline waste and by-products are essential. Therefore, we investigated the effectiveness and applicability of three types of autoclaved lightweight aerated concrete, recycled concrete, steel slag as basic oxygen furnace slag, and fly ash (mainly particles less than 0.106 mm and 0.106–2 mm in size), as alternative neutralizers for three representative acidic soils through laboratory neutralization experiments. The neutralization performance was evaluated by measuring the additive weight percentage of each neutralizer required to convert each acidic soil to neutral soil (pH 7). For neutralizers with two particle sizes, the finer fraction clearly showed lower additive weight percentages indicating higher neutralization performance. Among the six tested alkaline waste and by-products, the steel slag exhibited the highest neutralization performance. In particular, finer fraction steel slag exhibited a high neutralization performance, similar to that of the conventionally used calcium carbonate. This result suggests that fine steel slag (particle size < 0.106 mm) is the most promising and suitable alternative neutralizer.