188 / 2022-04-30 22:06:33

Development of low-carbon concrete for improving durability of composite foundation with plain concrete piles under marine environment

Low-carbon concrete,Cementing efficiency factor,Fly ash,Ground granulated blast-furnace slag,Marine environment

Low-grade concrete is commonly applied in composite foundations with plain concrete piles. Fly ash (FA) has been widely used in low-grade concrete, but the content is typically no more than 40% of the binder. In coastal areas, concrete can be attacked by ions in seawater, which can react with the hydration products, resulting in the dissolution and formation of expansive products that can lead to cracking. Moreover, service conditions of alternate drying-wetting and sudden changes in groundwater levels can accelerate the deterioration of concrete. To improve the durability of composite foundations with plain concrete piles, increasing the content of supplementary cementing material (SCM), such as fly ash and ground granulated blast-furnace slag (GGBS), can be an effective approach. Additionally, the use of SCM helps lower the embodied carbon in concrete, which is beneficial for achieving carbon neutrality.



This study aims to explore the feasibility of using high-volume SCM to improve the durability of C15 concrete in the marine environment. First, the cementing efficiency factors (k) of both FA and GGBS at various dosages were ascertained, and mortar with 40-80% SCM was designed based on the relationship between the equivalent water/cement ratio and compressive strength (Fig. 1). Then, the compressive strength and marine erosion resistance of mortar were tested, and an optimized binder composition was obtained. Finally, based on the aforementioned results, a new mix proportion of C15 concrete was designed, and it was compared with commercially available concrete (with 40% FA) in terms of mechanical properties, material cost, environmental impacts, and durability in the marine environment.



The results showed a linear relationship between the k value and the dosage of SCM (Fig. 2 and Fig. 3).  Concrete with 60% FA or 40-80% GGBS reaches or even slightly exceeds the 28-day compressive strength of the control group (concrete with 40% FA) (Fig.4). As for the environmental impacts, concrete with 60-80% SCM was eco-friendly in terms of low embodied carbon and embodied energy (Fig.5). The durability of concrete in the marine environment can be compared by the anti-erosion coefficients, and the results will be obtained soon. The findings from this study can shed light on the design of low-carbon and durable low-grade concrete.