The adverse effects of hostile marine environment on concrete structure have inevitably resulted in huge economic loss and may contribute to catastrophic failure. Concrete is susceptible to weathering, particularly under wetting-drying action (WDA), although its current state of the art is well established. The diverse characteristics of WDA at different site locations have compromised the reliability of laboratory works. The objective of this study is to review the impact of WDA on concrete and to provide an overview of the research trend, aiming to identify the research gap. Concrete deterioration mechanisms in marine environment in respect of WDA are identified. The influential factors of WDA are analyzed. The physical and mechanical properties and corrosion resistance of concrete exposed to WDA are discussed. WDA aggravates concrete deterioration by hastening intrusion of inimical compounds such as chloride, sulphate and carbon dioxide. Chloride convection zone can be expanded by two to three times to cause a significant concrete cover loss. Physical damage of concrete starts with efflorescence staining, followed by mortar delamination, aggregate detachment and concrete spalling, leading to loss of mechanical properties. The use of mineral admixtures such as fly ash and silica fume improves concrete resistance against corrosion, but its refining effect may lead to over-accumulation of chloride, risking the long-term durability. Limited research works are identified on synergy between physical and chemical deteriorations, validation of simulated experiment, volume expansion, mass change and tensile strength of concrete.

Meheron (2020) Mechanical and durability performance of marine sand and seawater concrete incorporating silicomanganese slag as coarse aggregate. Construction and Building Materials, 254. p. 119195.

The utilization of natural and artificial lightweight aggregates in lightweight self-compacting concrete (LWSCC) is gaining popularity in research field. Extensive research has been carried out in the past decade all over the world to utilize lightweight aggregates (LWA) in selfcompacting concrete (SCC). LWSCC, which uses renewable aggregates, has great potential to become an alternative material to conventional concrete. The paper is aimed to review the more recent research of physical properties of lightweight aggregates used in developing mix design of lightweight self-compacting concrete. In design, the mix proportion of LWSCC is a crucial factor to achieve the desired fresh and hardened concrete properties. The methods to develop LWSCC mix design with anticipated fresh and hardened concrete are reviewed. Research shows that the mix design LWSCC is preferably proportioned by aggregates packing concept. In addition, discussion on the fresh and hardened concrete properties is made and summarized in this paper. Studies indicate that there is a promising future for the use of lightweight aggregates in SCC as it shows satisfactory filling ability, passing ability, segregation resistance and compressive strength. Research gaps recommendations are then identified through this review to further discover lightweight self-compacting concrete in several aspects, particularly in term of sustainability.

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