Mechanical properties of one-part geopolymer masonry mortar using alkali-fused lead-zinc tailings

Currently, various industrial wastes such as tailings and smelting slag are recycled as raw materials in the field of construction. Tailings such as lead-zinc tailings (LZTs) are generally low-reactivity materials. In this study, LZTs were activated through alkali fusion and combined with slag to synthesize a one-part geopolymer. The optimal preparation process, including calcination temperature, alkali consumption, dwell time, and slag content, was determined using response surface methodology (RSM). Subsequently, the optimal geopolymer sample was used to produce a masonry mortar. Influences of the binder-sand ratio and water-reducing admixtures, including polycarboxylate, naphthalene, and sulfonation melamine, on the properties of the mortars were investigated. Based on the results, the geopolymer paste samples produced by activated LZTs (with 20 % alkali added and calcined at 568 degrees C for 83 min) and 60 % slag content exhibit the optimal compressive strength of 47.2 MPa. Moreover, with a decrease in the binder-sand ratio, the water/binder content required to achieve similar con-sistency increased continuously; thus, the 28-d compressive strength of the mortar samples reduced significantly from 34.0 to 12.8 MPa. Owing to the incorporated three admixtures, the consistency and 28-d compressive strength of mortar samples were significantly improved; in particular, sulfonation melamine was found to in-crease these factors by up to 61 % and 95 %, respectively.