ResearchArticle An Experimental Study on Unconfined Compressive Strength of SoftSoil-CementMixtureswithorwithoutGGBFSintheCoastal Area of Vietnam Son Bui Truong ,NuNguyenThi ,andDuongNguyenThanh HanoiUniversityofMiningandGeology,No.18VienStreet,DucangWard,BacTuLiemDistrict,Hanoi,Vietnam Correspondence should be addressed to Son Bui Truong; buitruongson@humg.edu.vn Received 15 January 2020; Revised 6 June 2020; Accepted 13 June 2020; Published 30 June 2020 Academic Editor: Li Li Copyright © 2020 Son Bui Truong et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 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). us, the use of this material for soft soil improvement needs to be considered. is paper presents experimental results on the unconfined com- pressive 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/m 3 with the three different water/cement ratios of 0.8, 0.9, and 1.0, respectively. e 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. e 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/m 3 ,2355kg/m 3 , 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. e research results also showed that the UCS of treated soil with cement GGBFS was higher than that of treated soil with Portland cement. is indicated the effectiveness of the use of Portland cement with GGBFS in soft soil improvement. ere is great potential for reducing the environmental problems regarding the waste materials from pig-iron plants in Vietnam and the construction cost as well. 1.Introduction Vietnam is one of the countries with a long coastline of more than 3000km [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 Ho- locene age, that is, young sediments. ese sediments are mainly in soft to very soft state and often make an unfa- vorable condition for construction activities [1–6]. Recently, the demand for infrastructure development in Vietnam is on the rise. us, there is great attention to the areas with poor soil conditions. However, the soil in these areas needs to be improved before building construction. So far, one of the methods that are commonly used for the improvement of soft soil in Vietnam is cement deep mixing (CDM) method [7–11]. is method has been also widely used in the world, especially in southeast Asian countries [12]. Regarding the use of cement for soil improvement, some main properties of soil-cement mixtures, including the unconfined compressive strength, the elastic modulus (E 50 ), small-strain shear modulus, and strain-dependent shear stiffness, have been widely investigated [12–19]. e un- confined compressive strength (UCS) is one of the most important strength parameters of cement-stabilized soils and has received much attention from the literature [15–17, 20–25]. Abbey et al. [24] indicated that UCS is the most essential parameter to design the cut-off walls for the Hindawi Advances in Civil Engineering Volume 2020, Article ID 7243704, 12 pages https://doi.org/10.1155/2020/7243704