Xu Chen, Wang Xiaolei, Liu Libo, Li Yancang
College of Civil Engineering, Hebei University of Engineering, Handan 056038, China.
Materials (Basel). 2025 May 25;18(11):2474. doi: 10.3390/ma18112474.
This study aims to address the challenge of backfill compaction in the confined spaces of municipal utility tunnel trenches and to develop an environmentally friendly, zero-cement-based backfill material. The research focuses on the excavation slag soil from a utility tunnel project in Handan. An alkali-activated industrial-solid-waste-excavated slag-soil-based controllable low-strength material (CLSM) was developed, using NaOH as the activator, a slag-fly ash composite system as the binder, and steel slag-excavated slag as the fine aggregate. The effects of the water-to-solid ratio (0.40-0.45) and the binder-to-sand ratio (0.20-0.40) on CLSM fluidity were studied to determine optimal values for these parameters. Additionally, the influence of excavated soil content (45-65%), slag content (30-70%), and NaOH content (1-5%) on fluidity (flowability and bleeding rate) and mechanical properties (3-day, 7-day, and 28-day unconfined compressive strength (UCS)) was investigated. The results showed that when the water-to-solid ratio is 0.445 and the binder-to-sand ratio is 0.30, the material meets both experimental and practical requirements. CLSM fluidity was mainly influenced by the excavated soil and slag contents, while NaOH content had minimal effect. The unconfined compressive strength at different curing ages was negatively correlated with the excavated soil content, while it was positively correlated with slag and NaOH content. Based on these findings, the preparation of "zero-cement" CLSM using industrial solid waste and excavation slag is feasible. For trench backfill projects, a mix of 50-60% excavated soil, 40-60% slag, and 3-5% NaOH is recommended for optimal engineering performance. CLSM is a new type of green backfill material that uses excavated soil and industrial solid waste to prepare alkali-activated materials. It can effectively increase the amount of excavated soil and alleviate energy consumption. This is conducive to the reuse of resources, environmental protection, and sustainable development.
本研究旨在应对市政公用隧道沟槽有限空间内回填压实的挑战，并开发一种环保的、零水泥基的回填材料。研究聚焦于邯郸某公用隧道项目的开挖渣土。以NaOH为激发剂，矿渣-粉煤灰复合体系为胶凝材料，钢渣-开挖渣土为细骨料，开发了一种碱激发工业固体废弃物-开挖渣土基可控低强度材料（CLSM）。研究了水固比（0.40 - 0.45）和胶砂比（0.20 - 0.40）对CLSM流动性的影响，以确定这些参数的最佳值。此外还研究了开挖土含量（45 - 65%）、矿渣含量（30 - 70%）和NaOH含量（1 - 5%）对流动性（流动度和泌水率）和力学性能（3天、7天和28天无侧限抗压强度（UCS））的影响。结果表明，当水固比为0.445且胶砂比为0.30时，该材料满足试验和实际要求。CLSM的流动性主要受开挖土和矿渣含量的影响，而NaOH含量的影响最小。不同养护龄期的无侧限抗压强度与开挖土含量呈负相关，与矿渣和NaOH含量呈正相关。基于这些发现，利用工业固体废弃物和开挖渣土制备“零水泥”CLSM是可行的。对于沟槽回填工程，建议采用50 - 60%的开挖土、40 - 60%的矿渣和3 - 5%的NaOH混合，以获得最佳工程性能。CLSM是一种利用开挖土和工业固体废弃物制备碱激发材料的新型绿色回填材料。它可以有效增加开挖土的用量，降低能耗。这有利于资源的再利用和环境保护以及可持续发展。
