Available online at www.CivileJournal.org Civil Engineering Journal (E-ISSN: 2476-3055; ISSN: 2676-6957) Vol. 8, No. 11, November, 2022 2445 Eco-friendly Super Sulphated Cement Concrete Using Vietnam Phosphogypsum and Sodium Carbonate Na 2 CO 3 Ngoc Lam Nguyen 1, 2* , Phuong Le Vu 1, 2 1 Hanoi University of Civil Engineering, No. 55, Giai Phong road, Hai Ba Trung District, Hanoi, Viet Nam. 2 Research group of Recycled Materials in Construction, Hanoi University of Civil Engineering, Hanoi, Viet Nam. Received 28 June 2022; Revised 26 September 2022; Accepted 13 October 2022; Published 01 November 2022 Abstract Sustainable development is one of the critical topics in the construction industry today, especially in reducing CO2 emissions and production energy costs. There have been many studies worldwide on using ground granulated blast furnace slag combined with phosphogypsum (PG) to replace binder (B) in making concrete. However, this topic in Vietnam has not received much attention despite the large backlog of phosphogypsum waste. One of the main disadvantages limiting the feasibility of super-sulphated binders in concrete is the relatively slow hydration and hardening processes, which affect the rate of strength development of mortar and concrete, especially at an early age. In this study, the use of Na2CO3 salt as a quick, solid additive can overcome the disadvantages of this type of binder. Research results show that using 15 to 25% phosphorus gypsum waste (PG) and a combination of 60 to 80% finely granulated blast furnace slag (GGBFS) with a small amount of cement and an activator like Na2CO3 can replace cement in making concrete. The concrete mix has good workability, and the maximum compressive strength after 28 days can reach over 50 MPa. Using industrial wastes as the main ingredients to make binders will improve sustainable development, reducing environmental pollution and the cost of mortar and concrete products in construction. Keywords: Concrete; Industrial Waste; Ground Granulated Blast Furnace Slag; Phosphogypsum; Super Sulphated Cement. 1. Introduction Environmental pollution is a topic attracting the attention of all countries worldwide. The massive development of industrial production in general and the production of building materials, in particular, has posed the problem of increasing emissions and waste, requiring reuse to avoid environmental pollution. Therefore, the research and use of industrial wastes to manufacture building material products have both technical and economic significance, ensuring green and sustainable production. One of the most promising alternative cementing systems is super-sulphated cement (SSC). This binder is mainly composed of ground granulated blast furnace slag (GGBFS), gypsum, and a small amount of alkali activator (such as quick lime, clinker cement, or cement) [1, 2]. Compared with ordinary Portland cement, super-sulphated cement has many advantages, such as low hydration heat evolution, good sulphate resistance, less clinker, and more gypsum. Thus, more solid waste can be consumed [3–6]. This binder can consume a large amount of gypsum in general, phosphogypsum (PG) in particular, and blast furnace slag. Phosphogypsum is a by-product in the fertilizer industry of the wet production of phosphoric acid (H3PO4). In Vietnam, the mountain of phosphogypsum waste is tens of meters high. Many hectares with a reserve of 3.5 million tons of DAP Vinachem Joint Stock Company are in Dinh Vu Industrial Park - Vietnam, causing many people to worry about * Corresponding author: lamnn@huce.edu.vn http://dx.doi.org/10.28991/CEJ-2022-08-11-06 © 2022 by the authors. Licensee C.E.J, Tehran, Iran. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).