Introduction. The Shatt al-Arab River is of significant economic and social importance to Iraq. Its hydrological regime is determined by the Tigris and Euphrates rivers, groundwater salinity, and climatic conditions. Increased water salinity due to low precipitation degrades water quality and increases the corrosive effects on concrete and reinforced concrete structures in the underwater areas of hydraulic structures. The objective of this study is to develop a corrosion-resistant, high-strength concrete based on a multi-component binder using locally sourced Iraqi raw materials. The objectives of the study include find-ing solutions to improve the durability of concrete structures operating in highly aggressive environments. Materials and Methods. For the production of corrosion-resistant heavy concrete with a multi-component binder, local Iraqi raw materials were mainly used: Portland cement CEM I 52.5N from the Tasluj plant, highly active metakaolin (MK), fly ash from the Baghdad Al-Nahrawan brick factory (FA), ash obtained from burning date kernels (DPA), as well as quartz sand (S) with a fineness modulus Mk = 2.5, crushed granite (CS) with a maximum grain size of 20 mm, polycarboxylate superplasticizer "MasterGleni-um 115" and water-retaining admixture "MECELLOSE PMC 15 US". The corrosion resistance of the de-veloped concrete mixtures was assessed based on the reduction in compressive strength, axial tensile strength and flexural strength, as well as the mass loss of concrete samples after three months of exposure to aggressive environments. Results. It was established that concretes with partial replacement of Portland cement in the binder composition by finely dispersed additives - such as metakaolin and mechanically activated acidic fly ash and date pit ash - possessing high pozzolanic activity due to their elevated content of amorphous silica, which binds free calcium hydroxide into less soluble and chemically stable low-base calcium hydrosilicates (the primary hydration products that enhance the strength of concrete), outperform conventional Portland cement-based heavy concrete in terms of density, strength characteristics, water impermeability, and cor-rosion resistance. This advantage holds true even in a liquid medium simulating the composition of the bot-tom water layer in the Shatt al-Arab delta near the Al-Faw port in Basra, on the Persian Gulf coast in southern Iraq. Notably, the heavy concrete based on an optimized four-component binder demonstrated the best performance. Conclusions. The incorporation of metakaolin and mechanically activated acidic ashes into the multi-component binder densifies the microstructure of the cement paste in the developed concretes and reduces the content of free calcium hydroxide. This contributes to the improvement of their physico-mechanical properties and service performance, including enhanced corrosion resistance across various aggressive environments.
Alwash et al. (Wed,) studied this question.