关键词: 铜渣, 草酸, 缓凝剂, 抗压强度, 凝结时间, 水泥

Abstract: Mixing according to a certain ratio, the copper slag and the oxalic acid were used as raw materials to prepare the copper slag-based oxalate cement by an acid-base reaction. The influence of the mass ratios of copper slag to oxalic acid (CS/OA) and water to cement (W/C), the retarder type and its content on the mechanical properties and setting time of copper slag-based oxalate cement ware discussed. The morphology and phase composition of the copper slag based oxalate cement were analyzed by SEM and XRD. The results showed that with the increase of mass ratios of CS/OA and W/C, the compressive strength increased first and then decreased, and the setting time decreased with the increasing of CS/OA and increased with the increasing of W/C. The borax and the sodium tripolyphosphate had a very negative influence on the compressive strength of the material, which lead to a significant decrease in the mechanical properties of the material as the amounts of the borax and the sodium tripolyphosphate increased. The proper amount of the boric acid can improve the compressive strength of the material and had a good retarding effect, therefore, the boric acid was preferred as a retarder. The material properties were optimum when CS/OA was 4, the W/C was 0.16?0.17, and the boric acid content was 2.5wt%. Its compressive strength reached 38.5 MPa after curing 28 d and the setting time was 24 min. The main hydration product of the copper slag based oxalate cement was a column type FeC2O4?2H2O, which has a dense structure and good crystallization. The addition of the borax and the sodium tripolyphosphate could cause stomata and gap in the copper slag based oxalate cement structure, while the boric acid could promote the hydration reaction to optimize crystallization of the hydrated product without compromising the compactness of the material structure.

Key words: copper slag, oxalic acid, retarder, compressive strength, setting time, cement