Abstract
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.
Highlights
Vietnam is one of the countries with a long coastline of more than 3000 km [1]
To study the effect of cement content on the unconfined compressive strength of soil-cement mixtures, a group of tests were conducted on three dosage rates, which were 250, 300, and 350 kg/m3. e cement proportion is defined as the weight of binder added per unit volume of the soil to be treated, expressed in kg/m3 [46]
Specimens were tested at three different binder contents (250 kg/m3, 300 kg/m3, and 350 kg/m3) and three water/ cement ratios (0.8, 0.9, and 1.0). e results of unconfined compressive strength (UCS) are shown in Table 5 and Figures 2–4
Summary
Vietnam is one of the countries with a long coastline of more than 3000 km [1]. Plains are distributed along the coastline and formed by sedimentation from many rivers such as Red, ai Binh, Ma, Dong Nai, and Mekong. e stratigraphy of these deltas is very complicated and is formed in the Holocene age, that is, young sediments. ese sediments are mainly in soft to very soft state and often make an unfavorable condition for construction activities [1,2,3,4,5,6]. One of the methods that are commonly used for the improvement of soft soil in Vietnam is cement deep mixing (CDM) method [7,8,9,10,11]. E UCS of soil-cement mixtures is often affected by many factors such as soil properties, the chemical reaction, cementitious constituent [26], and type of mixing method [27]. E development of strength of soil treatment depends on the mineralogy of soils, types and cement content, curing period, and environmental conditions of soft ground [12]. Kitazume and Tersahi [28] indicated that the most important factors that affect the properties of soil-cement columns are the binder type, soil properties, mixing type, and curing conditions
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