Oct 2026· Journal of materials in civil engineering· 0 citations· 38 references
Abstract
The direct use of untreated seawater and sea sand for concrete production may adversely affect the mechanical properties and durability of concrete, thereby limiting their widespread application in civil construction. To address this issue, this study has investigated the performance evolution of seawater–sea sand concrete (SWSSC) under long-term exposure to a natural marine tidal environment. The effects of adding ultrafine metakaolin (UMK) and
nano
-
TiO
2
(NT) were also explored in their enhancement on the SWSSC performance. Seven mix designs, including control, binary (UMK), and ternary (UMK and NT) mixtures, were exposed to real-world tidal wetting–drying cycles for up to 360 days. Mechanical properties, including cubic and axial compressive strengths, elastic modulus, and flexural strength, were periodically evaluated. The results showed continuous strength development in all mixtures, with the ternary group exhibiting the most balanced and cost-effective improvement, where SWSSC-UMK-NT10 reached a 28-day compressive strength of 65.4 MPa. The synergistic action of the UMK and the NT also markedly enhanced the matrix compactness and cracking resistance. Scanning electron microscopy (SEM) revealed the refined pore structures and denser interfacial transition zones in the modified SWSSC. X-ray diffraction (XRD) confirmed a reduction in the harmful crystalline phases and an increase in the formation of dense hydration products. Furthermore, mercury intrusion porosimetry (MIP) demonstrated the reduced total porosity, along with a shift in the pore size distribution toward the finer gel pores, thereby restricting the fluid transport pathways. In conclusion, the combined addition of UMK and NT is an effective strategy to improve the microstructure and durability of SWSSC in marine environments.
In tandem with global urbanization and infrastructure development, the escalating demand for concrete has prompted a search for eco-friendly alternatives against the extraction of river sand for fine aggregate. This study investigates the use of blended sea sand and manufactured sand (M-sand) as an alternative to river sand in concrete, with a focus on mechanical properties and durability. In Stage 1, three control concrete mixes—comprising river sand (RS), sea sand (SS), and M-sand (MS)-were tested alongside blends in which M-sand replaced sea sand at 25%, 50%, and 75% proportions. Evaluations included particle size distribution, compressive strength, workability, and durability via accelerated corrosion and chemical exposure tests. Results identified the 50% sea sand–50% M-sand blend as the optimal mix. In Stage 2, this optimal blend was further assessed against RS and SS concretes for mechanical properties (elastic modulus, splitting tensile strength) and durability characteristics (water absorption, density, void content, and chloride penetration resistance). Stage 3 focused on determining a permissible chloride content for the blend using accelerated corrosion testing. A chloride threshold of 0.05% was established, at or below which the durability performance remained comparable to the control mixes. These findings highlight the potential of SS–MS blended concrete as a sustainable alternative to traditional fine aggregates in construction.
H. Koswaththa, P. Abeyaratne, F. A. Izmie et al.· Ceylon Journal of Science· 0 citations
Coastal erosion severely threatens the stability of sandy shorelines, necessitating low-cost and sustainable bio-mediated treatment methods for shoreline protection. This study investigates an enzyme-induced carbonate precipitation (EICP) approach utilizing crude urease extracted from soybean hulls and concentrated seawater as an ionic source to enhance the erosion resistance of sand. The joint effects of urease activity, solution volume, treatment cycles, seawater concentration, and curing time were systematically evaluated through penetration strength, wind erosion, and hydraulic erosion tests, complemented by carbonate content measurements. Testing results indicate that the urease activity of the soybean hull extract scaled with the dosage, reaching a maximum of 2.27 mmol L
-1
·min
-1
. The seawater-based EICP treatment successfully formed a hardened surface crust, increasing the surface penetration strength to 0.841 MPa, while the critical wind velocity and critical flow velocity increased by up to 7.2 and 6.4 times, respectively, compared with untreated sand. Notably, multi-cycle spraying proved superior to a single application with the same total solution volume. While urease activity was the dominant factor governing carbonate production under relatively low-activity conditions, the number of treatment cycles exerted the strongest influence on hydraulic erosion resistance. Furthermore, power-law relationships were established between erosion-resistance indices and both carbonate content and penetration strength. Carbonate content showed consistently stronger correlations with erosion resistance than penetration strength, indicating that it provides a practical and reliable indicator for evaluating the erosion resistance of seawater-based EICP-treated sand. These findings demonstrate the feasibility of coupling agricultural by-product-derived urease with seawater-based EICP for cost-effective and sustainable stabilization of coastal sandy soils.
Reinforced concrete structures in marine environments deteriorate over time due to the hydrodynamic effects of seawater exposure and the transport of salt-laden, humid air. In particular, fluid-driven permeation and diffusion of chloride and sulfate ions into the porous matrix lead to chemical reactions that cause reinforcement corrosion and strength degradation, thereby shortening the service life of structures and threatening seismic safety. In countries such as Türkiye, which are both coastal and located in an active earthquake zone, evaluating the performance of these structures under prolonged fluid ingress is of great importance. This study investigates the mechanical and microstructural properties of a reinforced concrete structure exposed to long-term marine fluid conditions under real field conditions. Core compressive strength tests, Schmidt hammer tests, and tensile tests on reinforcement steel were conducted on samples taken from the structure. In addition, X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were performed to determine the microstructural characteristics altered by fluid-solid interactions. According to the findings, both the concrete and the reinforcement exhibited strength and durability losses driven by continuous moisture and ion transport. The compressive strength of the concrete did not satisfy regulatory requirements, and microstructural analyses indicated that the C-S-H gel underwent decalcification due to the influx of sulfate and magnesium-rich fluids, Portlandite was largely depleted, and the binder matrix exhibited chemical degradation. Advanced corrosion, cross-sectional loss, and pitting -facilitated by the presence of an aqueous electrolyte- were observed in the reinforcement, leading to reductions in yield strength, ductility, and bond performance. Furthermore, unsuitable aggregate properties and a weak Interfacial Transition Zone (ITZ) created preferential flow paths that accelerated deterioration, significantly reducing the structure's load-bearing capacity.
M. Altun, Yusuf Çetinkaya, M. Durgun et al.· Turkish Journal of Civil Eng...· 0 citations
The global demand for concrete has escalated rapidly due to the swift expansion of residential and commercial infrastructure. This phenomenon has consequently intensified cement manufacturing and aggravated anthropogenic carbon dioxide (CO2) emissions. To tackle these environmental issues and restrict fluid-induced microcracking in concrete elements, this experimental work evaluates the engineering properties of modified M20 concrete utilizing agro-industrial byproducts as alternative cementitious binders. In this study, Ordinary Portland Cement (OPC) was partially substituted with Class F fly ash at replacement levels of 30%, 35%, and 40%, alongside rice husk ash (RHA) at 5% and 10% by weight, establishing six distinct replacement categories. A total of seventy-seven cube specimens (150 mm × 150 mm × 150 mm) were fabricated to investigate workability, water absorption, compressive strength development, and water permeability resistance. The laboratory outcomes demonstrate that high cement substitution rates significantly alter the internal pore network, thereby governing both the strength gain and long-term durability behavior. Slump values across all formulated design mixes exceeded 100 mm, classifying the fresh concrete as collapsed slumps with high fluid consistency. Although the unblended control mixture displayed the highest 28-day compressive strength (19.53 N/mm²) and superior fluid penetration resistance (80.44 mm depth), the ternary blend containing 5% RHA and 40% fly ash was identified as the optimal eco-friendly formulation. This specific matrix yielded a 28-day compressive strength of 17.79 N/mm² and recorded the highest resistance to water penetration among all modified cohorts (141.00 mm). Even though the high volume of fly ash prevented the blended mixes from satisfying the empirical threshold of standard M20 concrete, the formulated green concrete exhibits promising technical viability for structural applications under the M15 classification. Ultimately, this research validates viable pathways for recycling natural waste products to minimize infrastructure deterioration and promote circular economy strategies within the construction sector.
C. Lee, Julia Binti Mohamed Uyob, Muhammad Akmal Bin Daud· ICEETE Conference Series· 0 citations
Sabkha soils, widely distributed in arid coastal regions, are characterized by high salinity, metastable structure, and low bearing capacity, posing significant challenges for geotechnical applications. Although sustainable stabilization methods have been increasingly explored, the application of alkali-activated waste glass powder (WGP) to highly saline sabkha soils, with emphasis on linking engineering performance to microstructural characteristics, remains insufficiently investigated. This study investigates the effectiveness of alkali-activated WGP as a sustainable and environmentally beneficial stabilizer for sabkha soil. WGP was incorporated at 10-30% by dry soil mass and activated using a sodium silicate-sodium hydroxide solution (Na₂SiO₃: NaOH = 2:1). The treated soils were evaluated through Standard Proctor compaction, California Bearing Ratio (CBR) under soaked and unsoaked conditions, and unconfined compressive strength (UCS) at curing periods up to 90 days, complemented by Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) analysis. The results reveal a property-dependent optimum WGP content. The highest CBR was achieved at 10% WGP (290% under soaked conditions and 180% under unsoaked conditions), while maximum UCS was obtained at 20% WGP, reaching 3550 kPa at 90 days. Although the untreated sabkha soil exhibited relatively high soaked CBR due to temporary salt-induced bonding, alkali activation provided a more stable cementation mechanism, resulting in improved mechanical performance. This distinction indicates that bearing resistance and compressive strength are governed by different mechanisms of stabilization. Excess WGP content (30%) led to reduced performance due to incomplete activation and disruption of particle interlocking. SEM-EDS observations indicated the development of a denser and better-bonded matrix that is consistent with the possible formation of sodium aluminosilicate hydrate (N-A-S-H) gel, accompanied by reduced pore connectivity and improved load transfer. The findings demonstrate that alkali-activated WGP provides an effective and more sustainable approach for stabilizing highly saline sabkha soils, highlighting the importance of property-dependent binder optimization for ground improvement in saline environments.
Samia Bouzouaid, H. Charrak, Ahmed Rafik Belakhdar et al.· Scientific Reports· 0 citations
The use of desert sands as an alternative to river sand in concrete may be limited by the presence of internally sourced sulfate and chloride ions, which may affect hydration and long-term performance. This study investigates the influence of naturally contaminated desert sands on the fresh and hardened properties of cement-based materials. Mortar mixtures produced with sands from three sites of the Atacama Desert were compared with mixtures containing artificially contaminated sands designed to reproduce equivalent ionic release during mixing. Hydration kinetics by isothermal calorimetry, strength development, and susceptibility to internal sulfate attack (ISA) were evaluated using isothermal calorimetry, compressive strength testing, and length change measurements. Results show that chloride contents up to 1.0% by mass of dry sand accelerated early hydration and increased 7-day compressive strength by up to 15% relative to the reference mixture. Conversely, sulfate contents of 0.24% reduced 28-day compressive strength by up to 18% and promoted long-term expansion associated with ISA. Mixtures containing combined moderate sulfate and high chloride levels exhibited enhanced early hydration without significant strength loss at later ages. The novelty of this study lies in linking ion release from natural desert sands to equivalent artificial contamination, enabling a systematic evaluation of internal sulfate–chloride interactions in cement-based materials.
P. Melo, Brandon S. Byers, Qingxu Jin et al.· Journal of materials in civi...· 0 citations
