Influence of Dregs Waste on the Alkali–Silica Reaction: A Comparative Analysis among Different Types of Cement

Dregs waste, a byproduct from green liquor clarification in the pulp industry, is increasingly generated as global cellulose production rises. This accumulation, along with its underutilization, presents environmental challenges and opportunities for reuse. The study focuses on the high alkali content in dregs, which can impact cement durability. The main objective is to analyze the effect of dregs on the alkali–silica reaction in mortars. Dregs were incorporated into mortar mixtures at 0%, 5%, 10%, and 15% proportions relative to cement mass, using six types of Brazilian cement and a blend with silica fume. The alkali–silica reactivity was assessed via the accelerated mortar prism test (ABNT NBR 15577-4:2018), with compressive strength tests and scanning electron microscopy evaluating structural integrity and microstructural changes. The results indicated that adding 5% dregs improved compressive strength in certain mortars, such as CP V-ARI RS, CP II-F, and CP IV. However, at 15% dregs, compressive strength significantly decreased, particularly in CP V with 10% silica fume. Cements with high pozzolanic content, such as CP IV and CP III, showed strong potential to inhibit ASR expansion. However, of the 28 mixtures analyzed, only four containing CP III had expansions within the limits set by standards. This study highlights the potential of incorporating dregs as a supplementary material in cement, promoting sustainability in the industry and reducing environmental impact.