Large-scale mining of graphite, a crucial strategic mineral, generates substantial amounts of graphite tailings (GT). The stockpiling of this solid waste occupies vast land resources and poses persistent environmental risks due to potential heavy metal leaching. Repurposing GT into construction materials presents a promising solution, with its use as a partial replacement for fine aggregates in cementitious composites being one of the most effective methods. This review systematically consolidates current research on graphite tailings cement mortar (GTCM) and graphite tailings concrete (GTC). Due to its physicochemical properties comparable to natural sand, GT is suitable for producing building materials. Studies consistently demonstrate that a substitution level of 10% to 20% optimizes overall performance. This optimal range enhances particle packing, promotes cement hydration via pozzolanic activity, and refines the microstructure, leading to improved workability, superior mechanical strength, and enhanced durability, including resistance to permeability, freeze–thaw cycles, and chemical attacks. Moreover, the inherent carbon content imparts electrical conductivity to GTC, enabling functional applications like de-icing and structural health monitoring. The successful utilization of GT also extends to lightweight foamed and autoclaved aerated concrete. However, research on the structural behavior of GTC components remains limited. Preliminary findings on beams and columns are encouraging, but comprehensive studies on their seismic performance and design methodologies are urgently needed to facilitate the widespread engineering application of this sustainable material and mitigate the environmental impact of tailings accumulation.

Sustainable design of high strength ECC using steel slag as fine aggregate: Toward waste valorization and environmental benefits

Corrigendum to “Corrosion-induced cracking and flexural behavior of recycled aggregate concrete beams with carbonated recycled coarse and fine aggregates” [Structures 81 (2025) 110377

Heavy rainfall shunts heavy metal transport from runoff to dominant sediment pathways in sludge-amended forest soils.

Replacing river sand in concrete: a review of emerging sustainable fine aggregate materials

The importance of concrete in modem society cannot be underestimated. There is no escaping from the impact of concrete on everyday life. Concrete is a composite material which is made of filler and a binder. Typical concrete is a mixture of fine aggregate (sand), coarse aggregate (rock), cement, and water. Nowadays the usage of concrete is increasing from time to time due to the rapid development of construction industry. The usage of concrete is not only in building construction but also in other areas such as road construction, bridges, harbor and many more. Thus technology in concrete has been developing in many ways to enhance the quality and properties of concrete. This study was made to investigate the nature of partial replacement of rice husk ash and steel slag and its influences on the strength properties of concrete. Properties of hardened concrete like compressive strength and workability was determined for different mix combinations of materials and these values are compared with the corresponding values of conventional concrete. Ordinary Portland cement (OPC) was replaced with Rice Husk Ash (RHA) by weight at 0%, 10%, 20% and 30%. And steel slag with Coarse Aggregate by weight at 0%, 20%, 40% and 60%.

Sand is one of the main materials used in the construction industry and serves as a key component in cement, concrete and mortar. The quality and availability of sand play a crucial role in determining the durability and performance of structures. This study examines the suitability of locally mined fine aggregates for use in cement concrete production, focusing on seven locations around the Dar es Salaam region of Tanzania: Mpigi Magohe, Misugusugu, Ngeta, Mbagala, Mkuranga, Tegeta and Jangwani. Sand quality directly influences concrete strength and durability, making proper selection essential. Physical and morphological properties were tested per ASTM standards, including sieve analysis, water absorption, specific gravity, bulk density, moisture, silt content, and organic matter content. Scanning Electron Microscopy (SEM) was used to evaluate sand morphology. The results showed that fineness modulus ranged from 1.75 to 2.66, water absorption between 1.80 and 6.08%, specific gravity from 2.50 to 2.65, bulk density from 1489 to 1735 kg/m3, silt content between 4.14 and 11.94%, and organic matter content from 0.15 to 0.75%. Morphological analysis revealed Misugusugu sand had the best texture, low porosity and compact grains, followed by Tegeta and Mpigi Magohe, which exhibited well-balanced morphological properties, while Ngeta and Mkuranga had poor morphology and higher porosity. Among these, only Mpigi Magohe and Tegeta sands met ASTM standards for high-quality fine aggregates, suitable for concrete production with a fineness modulus of 2.54 and 2.66, water absorption of 2.4% and 1.8%, specific gravity of 2.61 and 2.63, bulk density of 1621 kg/m3 and 1554 kg/m3, silt content of 4% and 4%, and organic matter content of 0.2% and 0.3% respectively. The study recommends blending of poorly graded sands such as those from Ngeta, Mkuranga, Mbagala and Jangwani with better quality sands from Mpigi Magohe or Tegeta to achieve improved particle size distribution and reduced impurities. Washing of high silt sands is also suggested to reduce contaminants, thereby enhancing the quality of local aggregates for construction purposes.

Influence of Partial Fine Aggregate Replacement with HDPE Plastic Waste on Concrete Compressive Strength: Melt Processing Vs. Water Quenching

Pervious concrete (PC) exhibits lower mechanical strength than conventional concrete due to inherent porosity. However, research suggests that incorporating fine aggregates enhances mechanical and physical properties. This study investigates, for the first time, the incorporation of small amounts of crushed mussel shells (MS) as fine aggregate in PC, relative to natural sand (NS). Seven mixtures were prepared with varying replacement levels of coarse aggregate by NS or MS. Binder drainage, mechanical, hydraulic, and physical properties were evaluated. Mixtures containing NS showed the highest compressive strength, split tensile strength, and Young’s modulus. Both fine aggregates reduced porosity and permeability. Compared to NS, MS resulted in lower mechanical strength due to higher porosity and distinct microstructural characteristics. Overall, partial replacement with NS until 5% enhanced mechanical performance, whereas MS was better at lower levels (3%), highlighting the role of fine aggregate type and content in balancing mechanical and porous characteristics of PC.

ABSTRACT Pavement texture polishing under vehicle loads is the main cause of skid resistance degradation. For Portland cement concrete (PCC) pavement, the repeated vehicle load is directly borne by the surface mortar. However, no standardized polishing method exists to characterize the skid resistance degradation of the surface mortar, and the mechanism of the texture evolution and skid resistance degradation during polishing remains unclear. In this study, the 3D topography scanning and the British pendulum tester were utilized to investigate the texture evolution of the surface mortar and its impact on skid resistance during accelerated polishing. A multi-scale analysis method based on the bearing area curve (BAC) and power spectral density (PSD) analysis was proposed. The relationship between the surface mortar texture and British pendulum number (BPN) under dry and wet conditions was established. The results indicate that the high-frequency texture of the surface mortar exhibits a non-uniform vertical distribution. The top topography corresponding at 10% material ratio (mr) shows the strongest correlation with BPN under dry conditions. For wet conditions, the texture with wavelengths λ > 0.25 mm provided by fine aggregates is key to enhancing the skid resistance. The findings provide a theoretical basis and technical guide for PCC pavement texture optimization.

Reinforced concrete is currently the most widely used system in the construction industry due to its excellent properties, including its durability, workability, lifetime, and compressive strength. However, reinforced concrete structures have disadvantages, such as corrosion, that affect their performance and may even lead to unexpected and/or premature failures. The main cause of this type of failure is the presence of chlorides, mostly from seawater. In this context, cathodic protection is one of the most efficient methods for protecting reinforced steel from corrosion. However, it is very expensive due to the high resistivity of concrete. In this research work, it is proposed to modify concrete by partially replacing the fine aggregate with rPET and CBF, thus exploiting the mechanical properties of rPET to promote energy dissipation, mitigating the stresses to which the reinforced concrete system is exposed and increasing its compressive strength. Furthermore, due to its hygroscopicity, CBF is used to promote moisture retention and reduce the resistivity of the concrete, thus facilitating cathodic protection of the reinforcing steel through the impressed current. The results indicate that the presence of rPET increases the compressive strength of concrete by approximately 8% in comparison with the reference sample after 28 days of curing, while the presence of CBF reduces the resistivity of concrete, ultimately increasing the cathodic protection efficiency of the reinforcing steel.

Background: Ambient yoghurt, also known as room-temperature yoghurt, has gained increasing attention due to its convenience in distribution and consumption without needing cold storage. To ensure extended shelf life, ambient yoghurt normally undergoes an additional heat treatment during manufacturing, the post-fermentation sterilisation process (typically at 65–85 °C), which may induce the formation of fine particle aggregates and result in undesirable textural attributes, particularly graininess. Assessing textural attributes of such products remains a challenge. Methods: By mimicking the oral behaviour of ambient yoghurt, this study uses rheological as well as tribological techniques for objective assessment of the textural sensations of slipperiness and graininess. Various experimental conditions, including the amount of saliva incorporation, sliding speed, and ball-contact and plate-contact lubrication, were examined, and results were analysed against perceived texture by panellists. Main findings: The results indicate that viscosity changes are closely associated with perceived slipperiness under the tested conditions. The friction coefficient obtained from a plate-contact tribometer shows a positive correlation with the sensation of graininess (Pearson’s r was 0.74, p < 0.05, N = 8). It was also observed that a 20% saliva incorporation showed the closest agreement with sensory perception, although this observation should be interpreted cautiously due to the limited sample size. Implications: Results obtained from this work indicate the feasibility of using rheology and tribology techniques for texture prediction in ambient yoghurt. The findings are exploratory in nature, and further studies with larger sample sets are required to validate the proposed approach. The methodology presented here may serve as a reference framework for investigating texture perception in other dairy systems.

The primary objective of this study is to bridge the gap between descriptive geometry and mechanistic design by establishing a dual-domain fractal framework to analyze the internal architecture of asphalt mixtures. This research quantitatively assesses the sensitivity of volumetric indicators—namely air voids (VV), voids in mineral aggregate (VMA), and voids filled with asphalt (VFA)—by employing the coarse aggregate fractal dimension (Dc), the fine aggregate fractal dimension (Df), and the coarse-to-fine ratio (k) through Grey Relational Analysis (GRA). The findings demonstrate that whereas Df and k substantially influence macro-volumetric parameters, the mesoscopic void fractal dimension (DV) remains structurally unchanged, indicating that gradation predominantly dictates void volume rather than geometric intricacy. Sensitivity rankings create a prevailing hierarchy: Process Control (Compaction) > Skeleton Regulation (Dc) > Phase Filling (Pb) > Gradation Adjustment (k, Df). Dc is recognized as the principal regulator of VMA, while binder content (Pb) governs VFA. A “Robust Design” methodology is suggested, emphasizing Dc to stabilize the mineral framework and reduce sensitivity to construction variations. A comparative investigation reveals that the optimized gradation (OG) achieves a more stable volumetric condition and enhanced mechanical performance relative to conventional empirical gradations. Specifically, the OG group demonstrated a substantial 112% enhancement in dynamic stability (2617 times/mm compared to 1230 times/mm) and a 75% increase in average film thickness (AFT), while ensuring consistent moisture and low-temperature resistance. In conclusion, this study transforms asphalt mixture design from empirical trial-and-error to a precision-engineered methodology, providing a robust instrument for optimizing the long-term durability of pavements in extreme cold and arid environments.

Abstract The incorporation of nanomaterials in concrete improves mechanical strength, durability, and resistance to environmental effects, presenting a sustainable approach for modern construction. This research employs symbolic regression approaches, namely Gene Expression Programming (GEP) and Multi Expression Programming (MEP), to forecast the compressive strength of nano enhanced (nano TiO 2 and nano SiO 2 ) concretes. The developed models were trained and validated using a comprehensive experimental database and evaluated through multiple statistical metrics. Based on the comparative performance metrics, the MEP model clearly outperformed the GEP model, achieving higher predictive accuracy (R 2 = 0.954), lower error values (RMSE = 5.427 MPa, MAE = 4.596 MPa, MAPE = 10.40 %), and stronger reliability (NSE = 0.953) compared to the GEP model (R 2 = 0.914). Model performance was illustrated through Taylor’s diagram. Partial Dependence Plots (PDPs) and Individual Conditional Expectation (ICE) plots were used to examine feature importance and interaction effects, showing that concrete age, cement, slag, and nano silica enhance strength, whereas higher water content and fine aggregate proportions reduce it. These results highlight the potential of MEP-based modeling to optimize mix design and promote the sustainable use of nanomaterials and supplementary cementitious materials (SCMs) in concrete, offering valuable guidance for sustainable construction.

The progressive depletion of natural aggregate resources and the increasing emphasis on sustainable construction practices have intensified interest in incorporating recycled concrete aggregate (RCA) into cement-based materials. This study provides a comprehensive evaluation of the influence of partially replacing natural fine aggregate with fine RCA on the physical, mechanical, and durability properties, as well as the microstructure, of cement mortars. Mortar mixtures containing 25%, 50%, 75%, and 100% RCA were tested and compared with a reference mix MC. The experimental program included measurements of bulk density, compressive and flexural strength, water absorption, and freeze–thaw resistance. Additionally, microstructural observations were performed to assess the effect of RCA on the internal structure of matured mortars. The results demonstrated that the intrinsic characteristics of RCA—particularly its higher water absorption and lower density—significantly affected the pore structure and mechanical behavior of the cement mortars. Mortars with RCA exhibited enhanced early-age compressive and flexural strength, especially at substitution levels of 50–100%, attributed to the activation of residual cement paste adhering to the recycled particles. However, increased porosity and water absorption in RCA-based mixes led to a higher sensitivity to freeze–thaw cycles compared with the reference mix. Overall, the findings indicate that incorporating fine RCA up to 50% enables the production of mortars with performance comparable to conventional mixtures under non-freezing conditions, while, under freeze–thaw exposure, comparable performance is achieved at replacement levels up to 25%, contributing to improved resource efficiency and reduced environmental impact. This study confirms the viability of fine RCA in cement mortars, emphasizing the importance of controlling pore structure development to maintain long-term durability. Additionally, it demonstrates that the use of recycled concrete aggregates provides a sustainable alternative to natural sand in mortar production.

Abstract Carbonated recycled aggregates can improve the durability of recycled aggregate concrete (RAC). In this paper, accelerated corrosion test and scanning electron microscope–energy‐dispersive spectroscopy (SEM–EDS) test were conducted on the carbonated recycled aggregate concrete (CRAC) to investigate the effects of the carbonated recycled coarse aggregate (CRCA), the carbonated recycled fine aggregate (CRFA), and the short‐term load on the corrosion‐induced cracking characteristics of CRAC. The results showed that the CRAC with high replacement ratio of both CRCA and CRFA exhibited comparable or even better corrosion resistance than the CRAC with low replacement ratio where only the recycled fine aggregate (RFA) was carbonated. The highly porous old mortar adhering to recycled coarse aggregate (RCA) was filled during carbonation by reaction products, but the efficacy of carbonation strengthening RCA was limited. Carbonation strengthening partially enhanced the performance of RFA, but the persistent microstructural deficiencies in CRFA resulted in inferior properties compared with the natural fine aggregate. When the CRFA replacement ratio increased from 30% to 50%, the CRAC exhibited a maximum increase of 4.63% in the average mass loss of steel bars, an increase of 87.64% in the total area of corrosion‐induced cracking, and an increase of 84.62% in the mean value of width of corrosion‐induced cracks. Under high short‐term load level, the CRAC with both CRCA and CRFA exhibited corrosion resistance comparable to that of CRAC treated only on RFA under low short‐term load level. The research findings can provide data support for the application of CRAC.

Towards standardisation of zinc slag as a sustainable fine aggregate substitute in concrete.

With the depletion of natural sand and gravel resources and increasing emphasis on environmental protection, natural aggregates suitable for concrete production are becoming increasingly scarce. Steel slag, a by-product of steelmaking, is produced in substantial quantities yet remains underutilized due to its low recycling rate. Owing to the high strength and excellent compatibility of steel slag particles with cementitious materials, they demonstrate significant potential as a replacement for natural river sand in fine aggregate applications. However, the volumetric instability of steel slag has long been a major impediment to its widespread adoption in cement-based composites. This study examines the stability performance of cement mortar containing steel slag aggregate, with the objective of clarifying the mechanisms responsible for dimensional instability resulting from steel slag incorporation. When the replacement level exceeds 40%, the dimensional stability of the mortar deteriorates markedly. The initial contents of free CaO (f-CaO) and free MgO (f-MgO) in the steel slag were determined to be 1.58% and 1.14%, respectively. Following 50 h of hydrothermal treatment, 69.6% of f-CaO and 44.3% of f-MgO had hydrated, causing internal volumetric expansion and subsequent particle fracturing. Under elevated temperature conditions, over-burned lime demonstrated 220% volumetric expansion and completed its reaction within 40 min, consequently impairing early-age stability. In contrast, periclase (dead-burned MgO) exhibited 34% expansion and attained a reaction degree of merely 13.3%, suggesting a more substantial impact on long-term stability. For each mixture, linear expansion measurements were performed on n = 5 independent specimens, and results are reported as mean ± standard deviation.

The thixotropy, shootability, and mechanical properties of wet-mix shotcrete (WMS) mixtures with high replacement rates of recycled fine aggregate (RFA) of 75% and 100% are examined in this study. Four different alternatives including reduced free mixing water and addition of metakaolin (MK), thixotropy enhancing agent (TEA), and polypropylene fibres (PPF) are evaluated in order to improve the WMS properties. Test results demonstrated that the build-up thickness improved by 1.3- to 2-folds with the incorporation of MK, PPF, and TEA, reflecting their suitability to overcome the inferior shootability at high RFA additions. The TEA significantly increased the development of thixotropy, which was ascribed to the chemical reactions that create a gel and dense network structure. The use of 1% TEA in the mix containing 75% RFA increased by 64% the thixotropic initial shear stress. Nevertheless, this was accompanied with the highest drop in strength, requiring proper tailoring of the dosage rate and mortar composition. Mixtures prepared with reduced water-to-binder ratio from 0.45 to 0.4 compensated the drop in strength due to high RFA rates. Yet, this alternative is not an efficient to counterbalance the decline in shootability, given the increased superplasticizer demand that promotes bleeding and sagging despite the high thixotropy.

The depletion of natural resources has created an urgent need to identify alternative, sustainable materials for construction. Simultaneously, the rapid global accumulation and improper disposal of electronic waste (E-waste), particularly in developing countries, have raised significant environmental and public health concerns. This study investigates the use of electronic plastic waste (E-PW) as a partial replacement for fine aggregate in concrete, with replacement levels of 5%, 10%, 15%, and 20% evaluated at different curing ages. While the inclusion of E-PW led to reductions in mechanical and durability performance compared to conventional concrete, these effects were mitigated by replacing 10% of the cement with silica fume (SF). The enhancement provided by SF demonstrated improved strength and performance in the E-PW concrete mixtures. According to SEM results, SF highlights the interfacial transition zone (ITZ) associated with E-PW in the OPC matrix. The best performing mix for blends containing E-PW and SF were M7 (5% E-PW + 10% SF), achieved a compressive strength of 37.69MPa, a flexural strength of 5.36MPa, and a splitting tensile strength of 3.91MPa at 56 days, surpassing those of the reference concrete. An environmental perspective, life cycle assessment demonstrated that a 20% replacement of fine aggregates with E-PW reduced the overall environmental burden by 5.3% and lowered the global warming potential by 1.43%, equivalent to saving approximately 4-5kg CO₂-eq per cubic meter of concrete. Hence, the findings support the potential for producing eco-efficient concrete by partially replacing natural sand with E-waste, contributing to resource conservation and environmental sustainability.