Soft soil is widely distributed in Vietnam, especially in the coastal area. In engineering practice, soft soil cannot be used to build any construction and needs to be improved or treated before building construction. In addition, Vietnam has many pig-iron or thermal power plants, which annually produce a huge amount of granulated blast furnace slag (GBFS). Thus, the use of this material for soft soil improvement needs to be considered. This paper presents experimental results on the unconfined compressive strength (UCS) of three Vietnam’s soft soils treated with Portland cement and Portland cement with ground granulated blast furnace slag (GGBFS). Binder dosage used in this study is 250, 300, and 350 kg/m³ with the three different water/cement ratios of 0.8, 0.9, and 1.0, respectively. The research results showed that the UCS of soil-cement mixtures depends on soil type, water/cement ratio, cement type, and binder content. Accordingly, the unconfined compressive strength increased with the increase of binder contents, the decrease of the natural water content of soft soil, water/cement ratios, and clay content. The highest value of UCS of treated soils was found for the soil at Site II with the Portland cement content, cement GGBFS, and water/cement ratio of 873 kg/m³, 2355 kg/m³, and 0.8, respectively. Besides, for all the three soils and two binder types, the water/cement ratio of 0.8 was found to be suitable to reach the highest UCS values of treated soil. The research results also showed that the UCS of treated soil with cement GGBFS was higher than that of treated soil with Portland cement. This indicated the effectiveness of the use of Portland cement with GGBFS in soft soil improvement. There is great potential for reducing the environmental problems regarding the waste materials from pig-iron plants in Vietnam and the construction cost as well.

中文翻译：

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越南沿海地区带或不带GGBFS的软土水泥混合物无侧限抗压强度的试验研究

越南，尤其是沿海地区，软土分布广泛。在工程实践中，软土不能用于建造任何建筑，需要在建造建筑之前进行改良或处理。此外，越南有许多生铁或火力发电厂，它们每年产生大量的高炉矿渣粉（GBFS）。因此，需要考虑将该材料用于软土改良。本文介绍了三种越南软土的波特兰水泥和波特兰水泥经粉碎的粒状高炉矿渣（GGBFS）处理后的无侧限抗压强度（UCS）的实验结果。本研究中使用的粘合剂剂量为250、300和350 kg / m ³三种不同的水灰比分别为0.8、0.9和1.0。研究结果表明，土壤-水泥混合物的UCS取决于土壤类型，水灰比，水泥类型和粘合剂含量。因此，无约束抗压强度随着粘合剂含量的增加，软土中天然水含量的降低，水灰比和粘土含量的增加而增加。处理过的土壤的UCS的最高值被发现为在点II土壤与波特兰水泥含量，水泥GGBFS，和873水/水泥比千克/米³，2355公斤/米³，和0.8。此外，对于所有三种土壤和两种黏结剂类型，发现水灰比为0.8可以达到处理后土壤的UCS最高值。研究结果还表明，水泥GGBFS处理过的土壤的UCS高于波特兰水泥处理过的土壤的UCS。这表明将波特兰水泥与GGBFS一起使用可改善软土地质。减少越南生铁厂废料的环境问题以及建设成本具有巨大的潜力。