Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements

Engineering and Technology Journal e-ISSN: 2456-3358 Volume 10 Issue 11 November-2025, Page No.-7680-7696 DOI: 10.47191/etj/v10i11.01, I.F. – 8.482 © 2025, ETJ 7680 ber 20251 NovemETJ Volume 10 Issue 1, 1 .Ismail, U. O Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements Ismail, U. O.1, Ajala A. M.2, Adebayo A. O.3, Olabemiwo O.A.4, Farayola O. J.5, Akanji E. O.6 1,2,3,4,5 Ladoke Akintola University of Technology, Department of Civil Engineering. 6University of Ibadan, Department of Civil Engineering. ABSTRACT: Concrete is a globally dominant construction material. This study addresses natural sand depletion and waste disposal challenges, aiming to statistically optimize concrete properties using Response Surface Methodology with ground waste bottle glass and cow bone ash replacements. Ordinary Portland Cement (OPC) conforming to BS 12 (1996) was used with river sand partially replaced by ground waste bottle glass (GWBG) and cow bone ash (CBA) in a 1:3:6 mix at 0.50 w/c ratio. Chemical and mineralogical analyses were performed using XRF and XRD, respectively. Workability was evaluated through slump and compacting factor tests, while compressive and tensile strengths were determined per BS standards. Experimental data were statistically optimized using Response Surface Methodology (RSM) in Design-Expert software. The X-ray fluorescence (XRF) analysis of Cow Bone Ash (CBA) revealed CaO, P₂O₅, SiO₂, MgO, and Al₂O₃ contents of 55.3%, 24.7%, 1.52%, 0.48%, and 0.35%, respectively. The X-ray diffraction (XRD) analysis identified hydroxyapatite, calcite, quartz, portlandite, sylvite, magnesite, and hematite with relative intensities of 72.6%, 15.4%, 4.8%, 3.2%, 1.5%, 1.0%, and 0.5%, respectively. The slump height and compacting factor values from 0% to 20% replacements of GWBG with CBA ranges from 55.47 to 34.58 mm and 4.59 to 4.61%, respectively. The 28-day compressive strength and splitting tensile strengths values were 14.85 to 14.41 MPa and 5.59 to 5.47 MPa, respectively. The optimal mix combination of 12.5% GWBG and 7.5% CBA recorded a slump height of 37.22 mm, compacting factor of 0.82, water absorption of 3.84%, compressive strength of 17.94 MPa, and splitting tensile strength of 6.05 MPa. The optimal mix of 12.5% GWBG and 7.5% CBA achieved the best balance of strength, durability, and workability, demonstrating excellent performance for sustainable and eco-efficient concrete production. KEYWORDS: Concrete optimization, Ground waste bottle glass (GWBG), Cow bone ash (CBA), Response surface methodology (RSM), Sustainable construction. 1.0 INTRODUCTION Concrete remains the most widely utilized construction material globally, serving as a fundamental component in infrastructure and structural development. Its versatility, availability, and relatively low cost make it indispensable for both developing and industrialized nations (Diaferio and Varona, 2024). However, the heavy reliance on natural aggregates, particularly river sand, poses a severe threat to ecological balance and environmental sustainability. The excessive extraction of sand from riverbeds and other natural sources has resulted in environmental degradation, loss of biodiversity, and disruption of aquatic ecosystems (Damseth et al., 2024). According to Mehta (2024), global concrete production has exceeded 4.83 billion tons annually, which underscores the immense strain placed on natural resources. The demand for sustainable alternatives has therefore become urgent, leading to a growing interest in the partial replacement of natural aggregates with waste-derived materials. Furthermore, the rapid urbanization and industrialization observed in many developing nations have contributed to the escalating generation of solid wastes, including glass and animal bone residues, which often end up in landfills (Krishna, 2024). The disposal of waste glass poses a major environmental challenge due to its non-biodegradable nature and slow decomposition rate (Adekomaya and Majozi, 2021). Similarly, cow bone ash, a by-product of abattoirs, is typically discarded indiscriminately, creating sanitation and environmental problems in many urban and peri-urban regions (Oduntan and Ndidi, 2024). Incorporating such waste materials into concrete not only provides an effective recycling pathway but also contributes to cleaner environments and reduced landfill accumulation (Almusaed et al., 2024). Previous studies have demonstrated that finely ground glass particles can serve as a partial substitute for fine “Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements” 7681 ber 20251 NovemIssue 1ETJ Volume 10 , 1 .Ismail, U. O aggregate, enhancing certain mechanical and durability properties when appropriately processed (Hakim et al., 2024; Barbhuiya et al., 2025). Consequently, the statistical optimization of concrete properties through Response Surface Methodology (RSM) offers a modern and reliable approach for understanding the complex interaction between multiple mix variables (Hurtado-Alonso et al., 2024). RSM enables the systematic analysis and optimization of input parameters—such as the proportion of waste glass and cow bone ash—to achieve desirable concrete performance outcomes with minimal experimental effort. This approach provides a predictive framework for evaluating the effects of material substitution on both fresh and hardened concrete properties. By employing this technique, it becomes possible to identify the optimal blend proportions that ensure strength, durability, and workability while minimizing costs and environmental impacts. Thus, RSM serves not only as a statistical optimization tool but also as a strategic instrument in advancing sustainable concrete technology. In addition, adopting waste materials such as ground waste bottle glass and cow bone ash contributes significantly to the principles of circular economy and resource efficiency. The valorization of these wastes in concrete production exemplifies an eco-friendly solution to two pressing challenges—solid waste management and natural resource depletion (El-Emam, 2024). Several recent studies (Tamanna et al., 2020; Steyn et al., 2021) have established that the use of recycled waste glass can reduce the demand for sand while enhancing the impermeability and durability of concrete. Moreover, cow bone ash has been reported to improve cementitious reactions and microstructural densification, leading to better mechanical performance (Mitikie et al., 2025). Therefore, this study situates itself within the framework of sustainable material engineering, aiming to develop a cost-effective and environmentally responsible concrete mixture through the synergy of waste glass and cow bone ash as fine aggregate replacements. The major problem addressed by this study arises from the overexploitation of natural sand, the environmental menace of improper waste disposal, and the lack of optimized methods for integrating alternative fine aggregates into concrete. Sand mining contributes to environmental degradation, groundwater depletion, and the destruction of aquatic ecosystems (Pandey et al., 2023). Meanwhile, glass and bone wastes remain underutilized, despite their potential as substitutes for natural aggregates. The challenge lies in understanding how these materials, when finely ground, influence the rheological, mechanical, and durability characteristics of concrete. Additionally, inconsistencies in the composition and particle size of waste glass have led to contradictory findings in previous studies, necessitating an optimized and statistically validated approach to determine the ideal replacement levels. Therefore, this study seeks to statistically optimize concrete mixes incorporating ground waste bottle glass and cow bone ash, thereby providing a reliable framework for material substitution that aligns with both performance and sustainability requirements. The significance of this study lies in its dual contribution to sustainable construction and waste valorization. By converting abundant waste materials into useful concrete constituents, this research supports environmental conservation and the circular economy model promoted by the United Nations Sustainable Development Goals (Ogunmakinde et al., 2022). The integration of ground waste bottle glass and cow bone ash into concrete production has the potential to reduce reliance on natural sand, mitigate waste accumulation, and minimize greenhouse gas emissions associated with sand mining and cement production (Farooq, 2022). Additionally, the application of RSM enhances the efficiency and scientific precision of material optimization, ensuring reproducibility and practical relevance of the results. Consequently, the outcomes of this study may serve as a benchmark for future research and policy formulation on sustainable material utilization in the construction industry. 2.0 MATERIALS AND METHOD 2.1 Sample Preparation and Mix Proportioning Ordinary Portland Cement (OPC) conforming to BS 12 (1996) specifications was used as the principal binding agent in all concrete mixtures. The fine aggregate consisted of locally sourced river sand, partially replaced by ground waste bottle glass (GWBG) and cow bone ash (CBA), both serving as sustainable fine aggregate substitutes. Coarse aggregate of 20 mm nominal size and potable water were employed in accordance with BS EN 1008 (2002). The concrete was proportioned at a nominal 1:3:6 mix ratio (cement: fine aggregate: coarse aggregate), corresponding to a grade 15 concrete with an expected compressive strength of about 15 N/mm² at 28 days. This mix was adopted because it represents a conventional composition widely used for non-structural or low-load-bearing mass concrete works, offering an economical balance between strength, workability, and material efficiency for comparative evaluation. A constant water–cement ratio (w/c) of 0.50 was maintained across all mix categories to ensure consistency. All materials were batched by weight for precision, and mixing was carried out using a Hobart A200 mechanical mixer (USA) to achieve homogeneity. The mixing sequence involved the dry blending of cement and fine aggregates (including sand, CBA, and GWBG) for two minutes, followed by the introduction of coarse aggregate and gradual addition of water. For CBA-only mixes, the river sand was replaced by 0%, 5%, 10%, 15%, and 20% CBA by weight. Similarly, the GWBG-only mixes followed the same replacement proportions. To evaluate the combined influence “Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements” 7682 ber 20251 NovemIssue 1ETJ Volume 10 , 1 .Ismail, U. O of both materials, five hybrid mixes were developed, maintaining a total fine aggregate replacement level of 20% distributed in different ratios of GWBG and CBA as depicted in Table 1. This arrangement was designed to provide adequate data points for the Response Surface Methodology (RSM) statistical modeling, enabling detailed analysis of both linear and interaction effects between the two waste materials. Table 1: Mix Proportioning for Concrete Incorporating GWBG and CBA. Mix ID Ground Waste Bottle Glass (% by Sand) Cow Bone Ash (% by Sand) Total Fine Aggregate Replacement (%) M0 0 0 0 M1 0 5 5 M2 0 10 10 M3 0 15 15 M4 0 20 20 M5 5 0 5 M6 10 0 10 M7 15 0 15 M8 20 0 20 M9 15 5 20 M10 10 10 20 M11 5 15 20 M12 12.5 7.5 20 M13 7.5 12.5 20 2.2 Material Characterization The Particle Size Distribution of the GWBG was performed according to BS EN 933-1 (1997) as shown in Plate 1. While, the chemical composition of the cow bone ash was determined using X-Ray Fluorescence (XRF) spectroscopy with a Panalytical Axios FAST XRF Spectrometer (Malvern Panalytical, Netherlands). Mineralogical characterization was conducted using X-Ray Diffraction (XRD) on a Bruker D8 Advance diffractometer (Bruker AXS GmbH, Germany) equipped with Cu Kα radiation (λ = 1.5406 Å) at 40 kV and 40 mA, scanned from 5°–70° (2θ). 2.1 Workability Assessment The workability of fresh concrete was assessed through slump and compacting factor tests in accordance with BS EN 12350-2 (2009) as illustrate in Plate 2, and BS 1881-103 (1983), respectively. The slump test was conducted using a standard Abrams cone (300 mm height, 200 mm base diameter, 100 mm top diameter) and a steel tamping rod of 16 mm diameter. The compacting factor test apparatus comprised two conical hoppers and a cylindrical mould fabricated according to standard dimensions. Each mix proportion was tested immediately after mixing to ensure consistent moisture and temperature conditions. Plate 1: sieve analysis process of the of the GWBG Plate 2: Slump test of the fresh concrete 2.2 Mechanical Strength Evaluation Concrete cubes of 150 mm × 150 mm × 150 mm were prepared for compressive strength tests, while cylindrical specimens of 150 mm × 300 mm were cast for split tensile strength determination. All specimens were demolded after 24 h and cured in water at 25 ± 2 °C for 7, 14, 21, and 28 “Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements” 7683 ber 20251 NovemIssue 1ETJ Volume 10 , 1 .Ismail, U. O days. Compressive strength tests were conducted using a Controls MCC8 Digital Compression Testing Machine (Controls Group, Italy) with a capacity of 2000 kN, conforming to BS EN 12390-3 (2009). Split tensile strength was evaluated using the same machine in accordance with BS EN 12390-6 (2009). The average value of three samples per age was recorded for each test. The compressive strength (fc) was determined using Equation (1): 𝑓𝐶= 𝑃 𝐴 (1) Where: P is the maximum applied load (N), and A is the cross-sectional area of the specimen (mm²). The split tensile strength (ft) was calculated using Equation (2): 𝑓𝑡= 2𝑃 𝜋𝐷𝐿 (2) Where: P is the load at failure (N), D is the diameter (mm), and L is the length of the specimen (mm). 2.3 Statistical Optimization Analysis Experimental data obtained from mechanical tests were analyzed using Response Surface Methodology (RSM) to model and optimize the interaction effects of waste bottle glass and cow bone ash on concrete properties. The statistical analysis was performed using Design-Expert Software (Version 13.0, Stat-Ease Inc., Minneapolis, USA). The Central Composite Design (CCD) approach was adopted to develop regression models, while Analysis of Variance (ANOVA) was employed to determine the statistical significance of each variable and their interactions at a 95% confidence level. Optimization plots and contour diagrams were used to identify the optimum substitution levels that produced the highest compressive and tensile strengths with acceptable workability. The coded levels of factors presented in Table 2 were derived to statistically represent the variation in the substitution of sand with Ground Waste Bottle Glass (GWBG) and Cow Bone Ash (CBA).The selected range of 0–20% was based on preliminary experimental results. The midpoint value of 10% represents the optimum level expected to achieve balanced performance in strength and durability characteristics. The coded factors −1, 0, and +1 correspond to the low, medium, and high replacement levels respectively, aligning with the experimental design framework of the Response Surface Methodology (RSM) approach used in this study. Table 2: Limit and Coded Levels of Factors for the Mix Design Factors Limit Range Factor Levels −1 0 +1 A: Ground Waste Bottle Glass (% by Sand) 0 – 20 0 10 20 B: Cow Bone Ash (% by Sand) 0 – 20 0 10 20 3.0 RESULTS AND DISCUSSION The study evaluated material characteristics, workability, mechanical performance, and optimized concrete properties using Response Surface Methodology for improved performance. 3.1 Characterization of Material The materials used were characterized to determine their physical, chemical, and structural properties for suitability in concrete production using XRD and XRF. The cow bone ash was characterized to identify its chemical composition and assess its potential as a cementitious material. The particle size distribution of GWBG was analyzed to evaluate its fineness and influence on the concrete’s packing density. 3.1.1 Characterization of Cow Bone Ash The X-ray fluorescence (XRF) analysis of cow bone ash presented in Table 3 reveals that calcium oxide (CaO) and phosphorus pentoxide (P₂O₅) are the predominant oxides, constituting 55.3% and 24.7% respectively, indicating the calcined material’s strong resemblance to hydroxyapatite minerals. The high CaO concentration suggests a significant potential for pozzolanic or cementitious reactivity when used as a supplementary material in concrete, as calcium-rich ashes have been reported to improve early strength gain and matrix densification. This observation is consistent with the findings of Luka et al. (2022), who attributed enhanced strength properties of blended cement composites to the presence of reactive lime in animal bone ash. In addition, the presence of minor oxides such as SiO₂ (1.52%), Al₂O₃ (0.35%), and Fe₂O₃ (0.25%) further indicates trace pozzolanic potential, although their relatively low proportions suggest that cow bone ash primarily acts as a filler and microstructural stabilizer rather than a highly reactive pozzolan. The limited silica and alumina content may also reduce the secondary formation of calcium silicate hydrate (C–S–H) gels, a trend similarly observed by Almulhim et al. (2022), who noted that the reactivity of bone ash depends more on its calcium-phosphate network than its silicate content. Furthermore, the low quantities of MgO, SO₃, K₂O, and TiO₂ imply reduced risk of deleterious expansion or alkali-silica reaction in concrete mixtures containing the ash. This chemical stability supports the suitability of cow bone ash as a partial cement replacement material with minimal risk of “Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements” 7684 ber 20251 NovemIssue 1ETJ Volume 10 , 1 .Ismail, U. O durability impairment. Overall, the XRF characterization confirms that the ash possesses a highly alkaline, calciumdominated composition capable of improving the mechanical and hydration properties of cementitious materials, aligning with reports by Putra et al. (2024) on the beneficial use of animal bone-derived powders in sustainable concrete development. Table 3: X-Ray Fluorescence (XRF) Analysis of Cow Bone Ash Oxide Cow Bone Ash (%) CaO 55.3 P₂O₅ 24.7 SiO₂ 1.52 MgO 0.48 Al₂O₃ 0.35 Fe₂O₃ 0.25 SO₃ 0.18 K₂O 0.12 Cl 0.05 TiO₂ 0.02 MnO 0.02 CuO 0.01 V₂O₅ 0.01 ZnO 0.01 The X-ray diffraction (XRD) analysis of cow bone ash presented in Table 4 identifies hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) as the dominant crystalline phase, with a relative intensity of 72.6%. This confirms that the ash is primarily composed of calcium-phosphate minerals derived from the calcination of bone matter, which enhances its potential for improving the hydration characteristics of cementitious materials. The prominence of hydroxyapatite aligns with findings by Patil et al. (2025), who reported that bone-derived ashes rich in hydroxyapatite contribute to microstructural refinement and improved bonding within concrete matrices. The presence of calcite (CaCO₃) at 15.4% further indicates partial carbonation during or after the combustion process, contributing to additional filler effects that enhance particle packing and reduce porosity. Similarly, quartz (SiO₂) detected at 4.8% provides limited pozzolanic contribution but supports matrix densification through its inert filling properties, a trend consistent with observations by Adepoju and Fapohunda (2020) on low-silica supplementary materials. The minor peaks corresponding to portlandite (Ca(OH)₂), sylvite (KCl), magnesite (MgCO₃), and hematite (Fe₂O₃) in small proportions (below 4%) suggest the presence of accessory phases that can influence early hydration and durability performance. Table 4: X-Ray Diffraction (XRD) Analysis of Cow Bone Ash S/No Dominant Minerals Identified Chemical Formula Relative Intensity (%) 1 Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) 72.6 2 Calcite (CaCO₃) 15.4 3 Quartz (SiO₂) 4.8 4 Portlandite (Ca(OH)₂) 3.2 5 Sylvite (KCl) 1.5 6 Magnesite (MgCO₃) 1 7 Hematite (Fe₂O₃) 0.5 3.1.2 The Particle Size Distribution of the GWBG The particle size distribution analysis presented in Figure 1 shows that the ground waste bottle glass (GWBG) consists predominantly of well-graded fine aggregates with a significant portion passing through the 4 mm sieve (99.2%) and gradually decreasing to 9.2% at the 0.075 mm sieve size. The distribution indicates a continuous gradation, suggesting an appropriate blend of coarse and fine particles that can “Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements” 7685 ber 20251 NovemIssue 1ETJ Volume 10 , 1 .Ismail, U. O contribute to good packing density and reduced void ratio within the concrete matrix. The calculated particle size parameters—D₆₀ = 0.72 mm, D₃₀ = 0.30 mm, and D₁₀ = 0.11 mm—further reveal a uniformity coefficient (Cu) of 6.55 and a coefficient of curvature (Cc) of 1.13, implying a wellgraded material suitable for partial fine aggregate replacement. This gradation enhances the internal particle arrangement, improving the mechanical interlock and reducing the risk of segregation and bleeding during concrete mixing. Similar findings were reported by Perera et al. (2021), who observed that finely ground glass particles with a broad size distribution enhanced the compaction and strength development of blended concrete mixes. Furthermore, the small percentage of particles below 0.075 mm indicates a limited presence of fines, which minimizes excessive water demand and maintains adequate workability. 3.2 Workability of Fresh Concrete 3.2.1 Slump value The results of the slump test presented in Figure 2 show notable variations in the workability of concrete mixes incorporating different proportions of ground waste bottle glass (GWBG) and cow bone ash (CBA). The control mix, containing 0% GWBG and 0% CBA, recorded the highest slump value of 55.47 mm, indicating optimal workability under normal conditions. However, as the CBA content increased from 5% to 20% at a constant 0% GWBG, the slump values decreased progressively from 48.62 mm to 34.58 mm, demonstrating a reduction in workability due to the high lime and phosphate content of CBA, which tends to increase water demand and reduce fluidity. Figure 1: Particle Size Distribution of the GWBG This behavior agrees with the findings of Win et al. (2022), who reported that ashes with high calcium oxide content reduce slump by enhancing particle cohesion and reducing free water in the mix. Conversely, the mixes containing only GWBG showed irregular variations in slump. For instance, 10% GWBG achieved a relatively high slump value of 45.29 mm, while further increases to 15% and 20% drastically reduced workability to 15.36 mm and 10.42 mm, respectively. This fluctuation can be attributed to the angular and smooth surface texture of crushed glass particles, which at lower levels may enhance flow but, at higher dosages, restrict paste coating and aggregate lubrication. Similar findings were reported by Abdulmunem and Hasan (2022), who observed that fine glass particles initially improve flowability but lead to stiff mixes when used excessively due to particle interference effects. For blended mixes of GWBG and CBA, moderate combinations such as 12.5% GWBG + 7.5% CBA and 10% GWBG + 10% CBA exhibited improved slump values of 37.22 mm and 33.56 mm, respectively, compared to other hybrid mixes. This suggests a synergistic interaction between the materials, where the fine glass particles help offset the water absorption tendency of CBA. These results are consistent with the observations of Chen et al. (2021), who reported that balanced combinations of pozzolanic and inert waste materials can enhance the flow behavior of concrete by optimizing particle packing and paste distribution. The compacting factor values presented in Figure 3 demonstrate the influence of ground waste bottle glass (GWBG) and cow bone ash (CBA) on the consistency and workability of fresh concrete. The control mix (0% GWBG + 0% CBA) recorded a compacting factor of 0.90, indicating a relatively high degree of workability typical of a well0 20 40 60 80 100 120 0.04 0.2 1 5 Paercentage of Passing (%) Sieve size (mm) d 10 d 30 d 60 “Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements” 7686 ber 20251 NovemIssue 1ETJ Volume 10 , 1 .Ismail, U. O proportioned nominal mix. As the percentage of CBA increased from 5% to 20%, the compacting factor gradually declined from 0.86 to 0.77, suggesting that CBA reduced the ease of compaction due to its high lime and phosphate content, which increase the surface area and water absorption capacity of the mix. Similarly, when GWBG was used independently, the compacting factor exhibited considerable variation. At 10% GWBG, the value peaked at 0.97, indicating improved flow and reduced internal resistance, likely due to the fine glass particles enhancing paste lubrication. Figure 2: Slump Height (mm) of Fresh Concrete Incorporating CBA and GWBG. However, higher replacements of 15% and 20% caused a sharp decline to 0.64 and 0.52, respectively, as excessive glass content reduced the paste volume available to coat aggregates, thereby hindering compaction. This trend aligns with the findings of Siddika et al. (2021), who noted that fine glass particles improve mix density only up to an optimal level, beyond which they cause particle segregation and stiffness. For hybrid combinations of GWBG and CBA, moderate blends such as 12.5% GWBG + 7.5% CBA and 10% GWBG + 10% CBA recorded compacting factors of 0.82 and 0.78, respectively. These values indicate that balanced proportions of both materials can yield a workable mix with adequate cohesion and compaction efficiency. This synergistic performance is consistent with the findings of Adeboje et al. (2022), who highlighted that blending supplementary materials with complementary physical and chemical characteristics enhances mix uniformity and packing efficiency. Figure 3: Compaction of Fresh Concrete Incorporating CBA and GWBG. 3.3 Mechanical Properties of Concrete 3.3.1 Water Absorption The results of the water absorption test presented in Figure 4, illustrate the influence of ground waste bottle glass (GWBG) and cow bone ash (CBA) on the permeability characteristics of concrete at different curing ages. The control mix (0% GWBG + 0% CBA) exhibited water absorption values of 2.44%, 3.53%, 4.47%, and 4.59% at 7, 14, 21, and 28 days, 55.47 48.62 42.38 38.27 34.58 25.43 45.29 15.36 10.42 27.81 33.56 29.64 37.22 31.49 0 10 20 30 40 50 60 Slum Height Variation of Mix Proportions 0.9 0.86 0.83 0.79 0.77 0.7 0.97 0.64 0.52 0.74 0.78 0.71 0.82 0.76 0 0.2 0.4 0.6 0.8 1 1.2 Compacting Value Variation of Mix Proportions “Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements” 7687 ber 20251 NovemIssue 1ETJ Volume 10 , 1 .Ismail, U. O respectively. This gradual increase with curing age indicates continuous hydration and capillary refinement, which is typical of conventional concrete. For mixes containing only CBA, a reduction in water absorption was observed up to the 10% replacement level, where values dropped to 2.18% at 7 days and 3.88% at 28 days. This decline signifies that moderate CBA inclusion improves pore structure densification due to the pozzolanic reaction between bone ash-derived CaO and cementitious compounds. However, further increase beyond 15% led to higher absorption (up to 4.61% at 20% CBA), implying that excessive CBA introduces unreacted particles that increase void content. This pattern aligns with the findings of Wang et al. (2022), who reported that bone ash enhances concrete impermeability only up to an optimal dosage, beyond which the microstructure becomes more porous. Conversely, the use of GWBG alone produced a continuous rise in water absorption across all curing ages, with the highest value of 7.65% recorded at 20% GWBG and 28 days. This trend suggests that glass powder, when used excessively, disrupts the cement matrix by creating microcracks and incomplete bonding zones. The observation agrees with the results of Nahi et al. (2020), who found that high glass powder content increases concrete permeability due to reduced paste cohesion and internal stress concentration. Hybrid combinations of GWBG and CBA, however, showed improved performance compared to single replacements. The mix containing 12.5% GWBG + 7.5% CBA exhibited the lowest water absorption at 28 days (3.84%), indicating optimal synergistic interaction between both materials. Similarly, the 10% GWBG + 10% CBA and 15% GWBG + 5% CBA mixes recorded relatively low absorption values of 3.91% and 4.12%, respectively. These results suggest that the reactive silica in GWBG and the calcium-rich nature of CBA complement each other, leading to the formation of additional calcium silicate hydrate (C–S–H) gel that refines pore structure and limits water ingress. Figure 4: Water Absorption of Concrete Incorporating GWBG and CBA 3.3.2 Compressive Strength The compressive strength results presented in Figure 5, reveal the influence of ground waste bottle glass (GWBG) and cow bone ash (CBA) on the strength development of concrete at different curing ages. The control mix (0% GWBG + 0% CBA) recorded compressive strengths of 13.87, 12.54, 12.38, and 14.85 N/mm² at 7, 14, 21, and 28 days, respectively, indicating a moderate strength gain with age. This trend reflects normal hydration progression, where the formation of calcium silicate hydrate (C–S–H) continues over time, enhancing the microstructural integrity of the concrete matrix. Concrete mixes incorporating only CBA exhibited an initial improvement in strength up to the 10% replacement level, with the highest 28-day strength of 17.04 N/mm² achieved at 10% CBA. This increase signifies the effective pozzolanic reactivity of CBA, which provides additional calcium and silica for secondary hydration reactions that refine pore structure and improve bonding within the matrix. However, beyond the 10% level, a decline in strength was observed, as seen in the 20% CBA mix, which recorded a lower 28-day strength of 14.41 N/mm². This reduction may be attributed to the dilution effect, where excessive CBA reduces the available cementitious content. This behavior corresponds with the findings of Abdulwahab et al. (2025), who reported that bone ash enhances strength at optimal levels but reduces it when the replacement becomes excessive due to incomplete reaction of surplus ash particles. Similarly, mixes containing only GWBG exhibited inconsistent performance, with strength generally decreasing 0 5 10 15 20 25 Water Absorption (%) Variation of Mix Proportions 28 days 21 days 14 days 7 days “Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements” 7688 ber 20251 NovemIssue 1ETJ Volume 10 , 1 .Ismail, U. O as the GWBG content increased. The 10% GWBG mix attained a moderate 28-day strength of 11.93 N/mm², while the 20% GWBG mix declined significantly to 6.84 N/mm². This decline can be linked to the inert nature of glass particles at higher dosages, which may act as weak inclusions within the matrix, thereby increasing porosity and weakening interfacial bonding. The observed trend aligns with the findings of Sivasuriyan and Koda, (2025), who noted that high glass powder content tends to impair strength development due to poor cementitious reaction and increased brittleness of the matrix. In contrast, hybrid combinations of GWBG and CBA demonstrated a significant enhancement in compressive strength compared to the single additive mixes. The blend containing 12.5% GWBG + 7.5% CBA recorded the highest 28-day compressive strength of 17.94 N/mm², followed closely by the 10% GWBG + 10% CBA mix with 17.28 N/mm². These results indicate a synergistic effect between GWBG and CBA, where the reactive silica in the glass powder combines with the calcium oxide content of CBA to form additional C–S–H gel, which densifies the microstructure and strengthens the interfacial transition zone. Similar findings were reported by Nawaz et al. (2025), who observed that combined pozzolanic materials containing silica and calcium-rich phases enhance concrete strength through complementary hydration and filler mechanisms. 3.3.3 Splitting Tensile Strength The splitting tensile strength results presented in Figure 6, show the influence of ground waste bottle glass (GWBG) and cow bone ash (CBA) on the tensile performance of concrete over different curing ages. The control mix (0% GWBG + 0% CBA) achieved tensile strengths of 5.43, 5.51, 5.56, and 5.59 N/mm² at 7, 14, 21, and 28 days, respectively. This gradual improvement with curing age reflects the continued hydration of cement and densification of the concrete matrix. The relatively moderate strength of the control mix provides a reference for assessing the effects of CBA and GWBG on the tensile behavior of concrete. Concrete containing only CBA exhibited a steady improvement in tensile strength up to a replacement level of 10%, which recorded a 28-day strength of 5.95 N/mm². This enhancement indicates that the fine CBA particles contributed to micro-filling and secondary pozzolanic reactions, promoting better interfacial bonding between the cement paste and aggregates. The increase in strength up to the optimum level can be Figure 5: Compressive Strength of Concrete Incorporating GWBG and CBA (N/mm²). attributed to the availability of reactive calcium and phosphate compounds that enhance matrix cohesion. However, a decline was observed beyond 10% CBA, with the 20% replacement mix showing a lower tensile strength of 5.47 N/mm², likely due to excessive dilution of the cementitious phase. This behavior corresponds with the observation of Becerra-Duitama and Rojas-Avellaneda, (2022), who reported that moderate inclusion of bone ash improves tensile strength through pozzolanic reactivity, while higher proportions tend to reduce performance due to incomplete hydration. On the other hand, concrete mixes incorporating only GWBG generally exhibited lower tensile strength values than the control. The 5% GWBG mix recorded the lowest 28-day tensile strength of 3.62 N/mm², whereas a slight improvement was noticed at 10% GWBG is 4.31 N/mm². The overall reduction in tensile capacity with increasing GWBG content can be linked to the brittle nature of glass and its relatively poor bond with the cement matrix when used alone. Moreover, the smooth surface texture of the glass particles limits mechanical interlocking, resulting in weaker tensile resistance. This observation is consistent with the findings of 0 10 20 30 40 50 60 70 80 Compressive Strength (N/mm²) Variation of Mix Proportions 28 days 21 days 14 days 7 days “Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements” 7695 ber 20251 NovemIssue 1ETJ Volume 10 , 1 .Ismail, U. O 8. Becerra-Duitama, J. A., and Rojas-Avellaneda, D. (2022). Pozzolans: A review. Engineering and Applied Science Research, 49(4), 495-504. 9. British Standards Institution (BSI). (1983). BS 1881103: Testing concrete – Part 103: Method for determination of compacting factor. London: British Standards Institution. 10. British Standards Institution (BSI). (1996). BS 12: Specification for ordinary and rapid hardening Portland cement. London: British Standards Institution. 11. British Standards Institution (BSI). (1997). BS EN 933-1: Tests for geometrical properties of aggregates – Part 1: Determination of particle size distribution – Sieving method. London: British Standards Institution. 12. British Standards Institution (BSI). (2002). BS EN 1008: Mixing water for concrete – Specification for sampling, testing and assessing the suitability of water, including water recovered from processes in the concrete industry, as mixing water for concrete. London: British Standards Institution. 13. British Standards Institution (BSI). (2009a). BS EN 12350-2: Testing fresh concrete – Part 2: Slump test. London: British Standards Institution. 14. British Standards Institution (BSI). (2009b). BS EN 12390-3: Testing hardened concrete – Part 3: Compressive strength of test specimens. London: British Standards Institution. 15. British Standards Institution (BSI). (2009c). BS EN 12390-6: Testing hardened concrete – Part 6: Tensile splitting strength of test specimens. London: British Standards Institution. 16. Chen, J. J., Guan, G. X., Ng, P. L., Kwan, A. K. H., and Chu, S. H. (2021). Packing optimization of paste and aggregate phases for sustainability and performance improvement of concrete. Advanced Powder Technology, 32(4), 987-997. 17. Choi, H. J., Kim, M. J., Oh, T., Jang, Y. S., Park, J. J., and Yoo, D. Y. (2022). Mechanical properties of high-strength strain-hardening cementitious composites (HS-SHCC) with hybrid supplementary cementitious materials under various curing conditions. Journal of Building Engineering, 57, 104912. 18. Damseth, S., Thakur, K., Kumar, R., Kumar, S., Mahajan, D., Kumari, H., and Sharma, A. K. (2024). Assessing the impacts of river bed mining on aquatic ecosystems: A critical review of effects on water quality and biodiversity. HydroResearch, 7, 122130. 19. Diaferio, M., and Varona, F. B. (2024). Concrete Structures: Latest Advances and Prospects for a Sustainable Future. Applied Sciences, 14(9), 3803. 20. El-Emam, D. A. (2024). Valorization of solid waste products from a variety of sectors in wastewater treatment processes. In Technical Landfills and Waste Management: Volume 2: Municipal Solid Waste Management (pp. 207-257). Cham: Springer Nature Switzerland. 21. Hakim, S. J. S., Mhaya, A. M., Mokhatar, S. N., Kamarudin, A. F., Tong, Y. G., and Chik, T. N. T. (2024, June). Towards greener concrete: a comprehensive review of waste glass powder as a partial fine aggregate substitute. In IOP Conference Series: Earth and Environmental Science (Vol. 1347, No. 1, p. 012072). IOP Publishing. 22. Hurtado-Alonso, N., Manso-Morato, J., RevillaCuesta, V., Skaf, M., and Ortega-Lopez, V. (2024). Optimization of cementitious mixes through response surface method: a systematic review. Archives of Civil and Mechanical Engineering, 25(1), 54. 23. Krishna, V. (2024). Characterization and compositional analysis of municipal solid waste in developing and developed world—An insight. In Solid Waste Management for Resource-Efficient Systems (pp. 3-27). Elsevier. 24. Luka, J., Olubajo, O. O., and Abuthakir, I. (2022). A Study on Portland Limestone Cement Blended with Animal Bone Ash and Metakaolin. American Journal of Chemical Engineering, 10(3), 103-115. 25. Mehta, V. (2024). Sustainable approaches in concrete production: an in-depth review of waste foundry sand utilization and environmental considerations. Environmental Science and Pollution Research, 31(16), 23435-23461. 26. Mitikie, B. B., Wubetie, T. A., and Elsaigh, W. A. (2025). Synergistic effect of cattle bone and rice husk ash on mechanical and microstructural properties of cement mortar. Scientific Reports, 15(1), 34160. 27. Nahi, S., Leklou, N., Khelidj, A., Oudjit, M. N., and Zenati, A. (2020). Properties of cement pastes and mortars containing recycled green glass powder. Construction and Building Materials, 262, 120875. 28. Nawaz, S., Akram, N., Sher, F., Tahir, S., Khan, W. R., Malik, A. M., and Siddique, F. A. (2025). AgroWaste-Based Cement Substitution: Synergistic Effects of Green Gram Pod Ash and Eggshell Powder on Concrete Strength. Kashf Journal of Multidisciplinary Research, 2(09), 208-226. “Statistical Optimization of Concrete Properties using Response Surface Methodology Incorporating Ground Waste Bottle Glass and Cow Bone Ash as Fine Aggregate Replacements” 7696 ber 20251 NovemIssue 1ETJ Volume 10 , 1 .Ismail, U. O 29. Oduntan, O. B., and Ndidi, N. O. (2024). 6. Assessment and availability of aquafeed: potential for alternative feed ingredient development in Nigeria. An overview on local alternative ingredients, aquafeed supply and feeding management in selected African countries, 197. 30. Ogunmakinde, O. E., Egbelakin, T., and Sher, W. (2022). Contributions of the circular economy to the UN sustainable development goals through sustainable construction. Resources, Conservation and Recycling, 178, 106023. 31. Pandey, S., Kumar, G., Kumari, N., and Pandey, R. (2023). Assessment of causes and impacts of sand mining on river ecosystem. Hydrogeochemistry of aquatic ecosystems, 357-379. 32. Patil, S., Thanikodi, S., Palaniyappan, S., Giri, J., Hourani, A. O., and Azizi, M. (2025). Sustainable synthesis of marine-derived hydroxyapatite for biomedical applications: a systematic review on extraction methods and bioactivity. Advanced Manufacturing: Polymer and Composites Science, 11(1), 2508547. 33. Perera, S. T. A. M., Zhu, J., Saberian, M., Liu, M., Cameron, D., Maqsood, T., and Li, J. (2021). Application of glass in subsurface pavement layers: A comprehensive review. Sustainability, 13(21), 11825. 34. Putra, N. E., Zhou, J., and Zadpoor, A. A. (2024). Sustainable sources of raw materials for additive manufacturing of bone‐substituting biomaterials. Advanced Healthcare Materials, 13(1), 2301837. 35. Siddika, A., Hajimohammadi, A., Ferdous, W., and Sahajwalla, V. (2021). Roles of waste glass and the effect of process parameters on the properties of sustainable cement and geopolymer concrete—a state-of-the-art review. Polymers, 13(22), 3935. 36. Sivasuriyan, A., and Koda, E. (2025). Incorporation of waste glass powder in the sustainable development of concrete. Materials, 18(14), 3223. 37. Steyn, Z. C., Babafemi, A. J., Fataar, H., and Combrinck, R. (2021). Concrete containing waste recycled glass, plastic and rubber as sand replacement. Construction and Building Materials, 269, 121242. 38. Tamanna, N., Tuladhar, R., and Sivakugan, N. (2020). Performance of recycled waste glass sand as partial replacement of sand in concrete. Construction and Building Materials, 239, 117804. 39. Wang, L., Zhou, S., Shi, Y., Huang, Y., Zhao, F., Huo, T., and Tang, S. (2022). The influence of fly ash dosages on the permeability, pore structure and fractal features of face slab concrete. Fractal and Fractional, 6(9), 476. 40. Win, T. T., Wattanapornprom, R., Prasittisopin, L., Pansuk, W., and Pheinsusom, P. (2022). Investigation of fineness and calcium-oxide content in fly ash from ASEAN region on properties and durability of cement–fly ash system. Engineering Journal, 26(5), 77-90.