Investigation mechanical characteristics and permeability of concrete with pozzolanic materials: a sustainable approach

Concrete is the most widely used construction material in the world. Therefore, the production of concrete with characteristics such as high strength and durability has received the attention of researchers. In alignment with sustainable development objectives, a pivotal focus within the construction industry has been the exploration of viable alternatives to conventional cement. In this study, the mechanical characteristics and permeability of the prepared samples containing pozzolanic materials (natural and synthetic) have been investigated by using the experimental method. To achieve the objectives of this research, six unique concrete mix formulations were developed, each incorporating silica fume, metakaolin (as a synthetic pozzolanic additive), and zeolite (as a natural pozzolanic substance). The performance outcomes of these mixes were then systematically evaluated against a baseline mixture that did not contain any pozzolanic components. Four distinct curing methods were employed: a humid environment (referred to as group A), a dry environment (designated as group B), and two corrosive environments (denoted as groups C and D). Compressive strength tests were conducted at 7, 14, 28, and 90 days, alongside indirect tensile strength tests at 28 and 90 days. Additionally, samples subjected to sulfuric solution (H2SO4) curing with a controlled pH of 1 at 90 days were compared against standard curing conditions. The permeability of the samples was evaluated through initial and final water absorption measurements, as well as penetration of water under pressure tests. Substituting 10% of the cement content with metakaolin and silica fume in the concrete mixing design enhanced the 28-day compressive strength under both humid and dry curing conditions, as compared to the control mixture. Incorporating a 10% substitution of cement with both natural and synthetic pozzolanic additives can beneficially preserve a portion of the compressive and tensile integrity that is otherwise diminished by sulfuric acid exposure, relative to the standard mix. Furthermore, this substitution enhances the mechanical robustness of the concrete. Replacing 10% of cement with natural and synthetic pozzolanic materials has a positive effect on maintaining part of the compressive and tensile strength loss due to sulfuric acid attacks compared to the control mixture, and the use of these materials improved the concrete's mechanical performance. The results indicate that incorporating pozzolanic materials (such as silica fume, metakaolin, and zeolite) leads to a reduction in initial water absorption compared to the control mix. Notably, this reduction is more pronounced in samples containing silica fume than in those containing metakaolin and zeolite.