针对钢渣自身水化活性偏低,易导致钢渣混凝土早期强度劣化的实际问题,研究合成聚羧酸盐分散剂(PCE)改性水化硅酸钙(C-S-H)纳米复合材料(C-S-H/PCE),表征分析该复合材料的微观结构,剖析其在钢渣胶凝体系中的协同作用机制,并探究不同掺量对钢渣水泥砂浆早期核心性能的影响规律。试验结果表明:C-S-H/PCE可显著加快钢渣水泥砂浆的凝结硬化进程,砂浆凝结时间随复合材料掺量增加呈线性递减趋势;该纳米复合材料可有效提升浆体抗压强度、细化浆体内部孔隙结构,对1 d龄期内砂浆早期性能强化效果尤为突出;此外,C-S-H/PCE可有效激发胶凝体系早期水化反应、提升整体早期水化程度;其不仅能诱导水泥基体生成更多水化产物、加速全体系水化进程,且水化产物种类未发生改变,保障了胶凝材料性能的稳定性与可控性,为钢渣水泥砂浆的性能优化及钢渣资源化高效利用提供了全新技术路径。

[Objective] With the rapid development of the iron and steel industry, steel slag, a by-product of iron and steel smelting, has become a key focus for environmental protection and sustainable development. However, its low activity can lead to a reduction in the early strength of concrete. Calcium silicate hydrate (C-S-H) not only shortens or even eliminates the induction period through homogeneous nucleation but also provides an excellent physical filling effect without negatively affecting later strength. This feature gives C-S-H broader application potential and greater prospects compared with traditional early-strength agents. However, C-S-H tends to agglomerate due to its small particle size and large specific surface area, which reduces its accelerating effect. [Methods] In this study, calcium silicate hydrate/polycarboxylate ether (C-S-H/PCE) materials were synthesized, and the effects of different dosages of C-S-H/PCE on the setting time, compressive strength, pore structure, and cement hydration of steel slag cement mortar were systematically investigated. The setting time of the cement mortar was measured following the standard test methods for water consistency, setting time, and stability of cement (GB/T 1346). Following the cement mortar strength test method (GB/T 17671-2021), the compressive strength of cement mortar was measured at 6 h, 8 h, 12 h, 18 h, 1 d, 3 d, 7 d, and 28 d. The porosity of the cement mortar after 1 d, 3 d, and 7 d of curing was determined using an Autopore IV 9520 mercury porosimeter. The thermal stability of the mortar at 3 d, 7 d, and 28 d was analyzed using a NETZSCH STA 2500 thermogravimetric analyzer. The mineral composition of steel slag cement mortar with varying C-S-H/PCE content was qualitatively analyzed using a Shimadzu XRD-6100 X-ray diffractometer. [Results] The adsorption of Ca²⁺ by C-S-H/PCE followed the Langmuir adsorption model. The results indicated that Ca²⁺ adsorption by C-S-H/PCE was monolayer, with a maximum adsorption capacity (Qmax) of 26.19 mg/g. Incorporating an appropriate amount of C-S-H/PCE into steel slag cement mortar effectively accelerated its setting time. The reduction in setting time was proportional to the C-S-H/PCE dosage. Higher C-S-H levels led to shorter times for the cement mortar to reach both initial and final setting. Adding C-S-H/PCE enhanced the compressive strength of steel slag cement mortar, particularly at early stages (within 1 day). Higher C-S-H/PCE content resulted in greater early compressive strength, while the rate of compressive strength increase decreased with curing age. Incorporating an appropriate amount of C-S-H/PCE effectively improved the compactness of steel slag cement mortar and refined its pore structure. This effect was particularly pronounced at early stages of mortar curing, during which C-S-H/PCE significantly reduced porosity. As C-S-H/PCE content increased, the number of macropores decreased significantly, while the proportion of gel pores and mesopores increased, promoting a denser and finer pore structure. [Conclusion] C-S-H/PCE not only stimulates the formation of additional hydration products and accelerates the overall hydration process but also does not alter the types of hydration products, ensuring the stability and controllability of cement properties, and providing a new approach for optimizing steel slag cement mortar performance. This study provides a solid theoretical foundation and technical guidance for the scientific and rational utilization of steel slag in concrete, promoting its practical application and the sustainable development of steel slag resources.