Journal Articles

Influence of chemical activation on the strength and durability of lime–corn cob ash cement

Sat, 01 Aug 2026 00:00:00 GMT

Influence of chemical activation on the strength and durability of lime–corn cob ash cement Odiwuor, Vincent O.; Barasa, Stephen S.; Onyambu, Onyambu The slow rate of strength gain and the relatively poor durability of lime–pozzolana binders limit their broader use in sustainable construction applications. This study examined how chemical activation influences the physicochemical characteristics, compressive strength, porosity, and sulfuric acid resistance of lime–corn cob ash (CCA) mortars. CCA was analyzed using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and electrical conductivity tests to evaluate its pozzolanic behavior. Mortars containing a 50:50 lime–CCA ratio were prepared using water, 0.5 M NaOH, and 0.5 M Na2SO4 as mixing media. The results indicated that CCA is rich in silica (61.61% SiO2), with a combined SiO2 + Al2O3 + Fe2O3 content of 72.19%, confirming its suitability as a pozzolanic material. The reduction in electrical conductivity of about 28.1% after 240 min suggests moderate pozzolanic reactivity of CCA. Chemical activation markedly enhanced performance. Compressive strength increased from 2.91 MPa in the non-activated system to 5.92 MPa and 7.77 MPa for Na2SO4 and NaOH-activated mortars, respectively. Porosity showed a decreasing trend from L100–H2O to LCCA50–0.5 M NaOH. Under sulfuric acid exposure, activated mortars experienced lower mass and strength losses than non-activated ones, with NaOH activation providing the best resistance. In contrast, pure lime mortar fully disintegrated under acidic conditions. The results confirm that chemical activation significantly improves the mechanical performance and durability of lime–CCA binders. The study demonstrates the viability of corn cob ash as a sustainable pozzolanic material for low-carbon, non-structural construction applications and highlights the effectiveness of different chemical activators in enhancing lime-based systems.

Performance and Durability of Chemically Activated Lime-Based Cement Blended With Rice Husk Ash

Wed, 01 Jul 2026 00:00:00 GMT

Performance and Durability of Chemically Activated Lime-Based Cement Blended With Rice Husk Ash Odiwuor, Vincent O.; Samita, Fidelis N.; Wetungu, Martin W. Lime–pozzolana binders ofer a low-carbon alternative to conventional materials; however, their practical application is limited by slow strength development and insufcient durability, particularly under aggressive chemical environments. In addition, existing studies on chemical activation have largely focused on OPC-based systems, with limited attention to lime-based binders and their durability performance. This study investigates the efect of chemical activation on the performance and durability of lime–rice husk ash (RHA) mortars. The objective was to evaluate how sodium hydroxide (NaOH) and sodium sulfate (Na2SO4) infuence compressive strength, porosity, and resistance to sulfuric acid attack of lime mortars. Physicochemical characterization confrmed that the RHA contained 94.95% SiO2 with high amorphous content and strong pozzolanic reactivity (> 60% conductivity loss). Results showed that RHA incorporation improved lime mortar performance, while chemical activation signifcantly enhanced these properties. NaOH activation increased compressive strength by 132%, compared to 53% for Na2SO4, relative to the non- activated system. Porosity decreased progressively across the systems, with the lowest values observed in NaOH-activated mortars. Under acid exposure, all RHA-containing mortars outperformed pure lime, which disintegrated completely. Strength and mass losses were lower in activated systems, particularly with NaOH. Deterioration was more severe in 3% H2SO4 than in a 0.5% solution. The fndings indicate that chemical activation improves the short-term performance of lime–RHA mortars, although reaction products were not directly quantifed. These results highlight the potential of chemically activated lime–RHA mortars as sus- tainable construction materials, particularly in resource-constrained regions.

Using Pozzolanic Materials to Improve Mechanical Properties of Lime-Based Mortar

Mon, 01 Jun 2026 00:00:00 GMT

Using Pozzolanic Materials to Improve Mechanical Properties of Lime-Based Mortar Odiwuor, Vincent O.; Ayabei, Kiplagat; Okoth, Maurice O.; Munyao, Onesmus M. The environmental impact associated with the production of Portland cement has intensifed interest in sustainable alternatives such as lime-based binders. However, their application is constrained by low early strength and slow hardening. This study evaluates rice husk ash (RHA) and sugarcane bagasse ash (SCBA) as pozzolanic additives to enhance the mechanical performance and durability of lime mortars. Hydrated lime was partially replaced (50%) with RHA or SCBA, and the mortars were air-cured for 28 days. Both ashes satisfed the standard pozzolanicity requirements. RHA exhibited a higher amorphous silica content and greater reactivity, whereas SCBA demonstrated slower but sustained pozzolanic activity. The incorporation of these pozzolans signifcantly improved performance. Compressive strength increased from 0.43 MPa for pure lime to 4.64 and 3.84 MPa for RHA and SCBA mortars, respectively. Flexural strength improved from 0.17 to 2.70 MPa and 0.97 MPa for RHA and SCBA mortars, respectively. Water absorption was substantially reduced in the modifed mortars, indicating improved pore structure and du- rability. RHA provided superior strength development and lower permeability, while SCBA ofered moderate strength en- hancement with improved fexibility. These characteristics make both materials suitable for nonstructural applications, including heritage conservation and restoration. The fndings demonstrate that agricultural waste ashes can serve as efective, low-carbon pozzolanic materials for durable lime-based construction.

Pozzolanic reactivity and mortar performance of sugarcane bagasse and sawdust ashes in lime based binders

Sat, 01 Aug 2026 00:00:00 GMT

Pozzolanic reactivity and mortar performance of sugarcane bagasse and sawdust ashes in lime based binders Odiwuor, Vincent O.; Wambu, Enos W.; Okoth, Maurice O.; Kipkemboi, Pius K. The growing energy demand, rising production costs, and environmental impacts associated with ordinary Portland cement have intensified the search for sustainable, low-carbon binders. Lime–pozzolana systems incorporating agricultural waste ashes present a viable alternative; however, their development is often based primarily on strength results, limiting insight into the role of material structure and reactivity. This study comparatively evaluates sugarcane bagasse ash (SCBA) and sawdust ash (SDA) as supplementary cementitious materials in lime-based binders, with emphasis on linking physicochemical properties to performance. The ashes were produced under controlled calcination at 600–700 °C and characterized for oxide composition, mineralogy, particle size distribution, specific surface area, and loss on ignition. SCBA exhibited a high combined content of SiO2 + Al2O3 + Fe2O3 (86.60%) and was predominantly amorphous, whereas SDA showed a significantly lower content (23.16%), higher loss on ignition (15.33%), and a largely crystalline structure, despite possessing a higher specific surface area. Pozzolanic activity was assessed via electrical conductivity measurements. The results revealed faster early reactivity for SDA, attributed to its higher surface area, while SCBA demonstrated more sustained reactivity due to its high amorphous silica content. At 28 days, SCBA–lime mortars achieved compressive strengths of 2.98–3.72 MPa, compared to 1.51–2.52 MPa for SDA–lime mortars across pozzolan-to-lime ratios of 3:1 to 1:1. Similarly, SCBA mortars exhibited higher bulk density (930.6 kg/m3) and lower water absorption (14.14%) than SDA mortars (812.4 kg/m3 and 18.14%, respectively). All mixes exceeded the minimum strength requirement of 2 MPa for lime–pozzolana binders, although they remained significantly lower than the OPC control (48.06 MPa). Overall, SDA enhances early-age reactivity, whereas SCBA provides superior long-term mechanical performance. These findings establish a clear relationship between material characteristics, pozzolanic behavior, and mortar performance, offering practical guidance for the selection of locally available agricultural ashes in sustainable construction.

Physicochemical And Mechanical Performance Of Lime- Based Binders Incorporating Rice Husk Ash And Calcined Clay

Sat, 01 Aug 2026 00:00:00 GMT

Physicochemical And Mechanical Performance Of Lime- Based Binders Incorporating Rice Husk Ash And Calcined Clay Odiwuor, Vincent Onyango,; Wambu, Enos W.; Okoth, Maurice O.; Kipkemboi, Pius K. The environmental concerns linked to ordinary Portland cement have increased the demand for alternative binder systems that utilize locally available resources efficiently and still provide adequate performance. This study investigates the potential of rice husk ash (RHA) and calcined clay (CC) as supplementary pozzolanic materials in lime-based binders. The objective was to comparatively evaluate the influence of these materials on physicochemical properties, reactivity, and mechanical performance and to establish relationships between these parameters. RHA and CC were produced under controlled calcination conditions and characterized using chemical, mineralogical, and surface analyses. Pozzolanic reactivity was assessed through electrical conductivity measurements, while performance was evaluated using water absorption and compressive strength tests. The results showed that both materials satisfied standard chemical requirements for pozzolans; however, their reactivity differed significantly due to variations in structure and surface characteristics. RHA exhibited a predominantly amorphous structure and a high specific surface area, resulting in faster reaction kinetics, greater calcium hydroxide consumption, and slightly higher compressive strength when used in lime-based mortars. In contrast, CC displayed a mixed amorphous–crystalline composition and lower surface area, leading to slower but sustained reactivity. The incorporation of both pozzolans improved compressive strength and reduced water absorption compared to pure lime mortar. After 28 days, blended mortars achieved strengths of approximately 4.2–4.3 MPa, indicating suitability for non-structural applications. The findings demonstrate that binder performance is governed by the combined effects of chemical composition, phase structure, surface properties, and reaction kinetics rather than composition alone. This study provides a systematic comparative assessment of RHA and CC in lime-based systems and highlights the importance of integrating physicochemical characteristics with reactivity measurements to better understand and optimize the performance of sustainable binder materials.

Effects of Adsorbent Dosage and Particle Size on Fluoride Removal Using Calcium-Spiked Moringa oleifera Seed Powder

Mon, 01 Sep 2025 00:00:00 GMT

Effects of Adsorbent Dosage and Particle Size on Fluoride Removal Using Calcium-Spiked Moringa oleifera Seed Powder Chavaregi, Geoffrey,; Lusweti, John; Keronei, Pius Access to safe drinking water remains a major challenge in fluoride-endemic regions, where excessive fluoride concentrations can lead to dental and skeletal fluorosis. This study evaluated the effects of adsorbent dosage, particle size, and particle size classification (mesh size) on the fluoride removal performance of Moringa oleifera seed powder (MOSP) in both calcium-spiked and non-spiked forms. A three-factor factorial batch adsorption experiment was conducted using initial fluoride concentration of 1ppm, dosages of 0.25–2.0 g/100 mL, particle sizes of <250 μm, 250–500 μm, and >500 μm, and mesh classifications of 20 (850 μm), 40 (425 μm), and 60(250 μm). Response variables included fluoride removal efficiency, residual fluoride concentration, and adsorption capacity (qe), measured using a fluoride ion-selective electrode. ANOVA and linear regression were applied to evaluate the dose and size response relationships. Results showed that calcium-spiked MOSP consistently outperformed non-spiked MOSP across all parameters. Fluoride removal efficiency increased with dosage, reaching 88.95% for spiked and 70.34% for non-spiked MOSP at 2.0 g. Finer particle sizes and smaller mesh fractions significantly enhanced removal efficiency and reduced residual fluoride levels, with spiked MOSP at ≤250 μm achieving 89.80% removal and residual fluoride below WHO guidelines. Regression analysis confirmed strong inverse relationships between particle size/mesh size and fluoride removal performance, and positive correlations with dosage. The improved performance of calcium-spiked MOSP is attributed to increased surface-active Ca2+ sites enabling precipitation of CaF2 and enhanced adsorption via electrostatic attraction and ion exchange. These findings indicate that calcium-spiked MOSP, optimally prepared at fine particle size and moderate dosage, is a viable, locally sourced defluoridation medium suitable for rural water treatment systems.

Fluoride Removal Efficiency of Calcium-spiked and Non-spiked Moringa Oleifera Seed Powder

Wed, 01 Oct 2025 00:00:00 GMT

Fluoride Removal Efficiency of Calcium-spiked and Non-spiked Moringa Oleifera Seed Powder Chavaregi, Chavaregi; Lusweti, John; Keronei, Pius Fluoride contamination in drinking water remains a widespread public health concern, particularly in arid and semi-arid regions where groundwater is the primary source of potable water. Chronic exposure to elevated fluoride levels—commonly above the World Health Organization’s (WHO) recommended limit of 1.5 mg/L—can result in dental and skeletal fluorosis, affecting millions of people globally. Affordable and effective defluoridation technologies are urgently needed, especially in low-income rural settings. In this study, the fluoride removal efficiency of calcium-spiked and non-spiked Moringa oleifera seed powder was investigated through controlled laboratory batch adsorption experiments. Biosorbents were prepared by treating ground seed powder with 1% calcium chloride solution and characterised based on their performance across five fluoride concentrations (1-20 ppm). Key parameters such as removal efficiency, residual fluoride levels, and adsorption capacity (qe) were evaluated under consistent operating conditions (pH 7, 2 g/50 mL dose, mesh 40, 120 minutes). Results indicated that calcium-spiked Moringa oleifera powder significantly outperformed its non-spiked counterpart. At 1 ppm, the spiked adsorbent achieved 94.35 ±1.15% removal efficiency, compared to 81.45 ±1.35% for the non-spiked. At the highest tested concentration (20 ppm), the spiked biosorbent still removed 72.31 ±1.80% of fluoride, while the non-spiked removed only 54.21 ±1.95%. Linear regression models showed strong inverse correlations between fluoride concentration and removal efficiency (R2 > 0.99, p < 0.001). The spiked adsorbent also resulted in significantly lower residual fluoride concentrations, with final values closer to the WHO guideline. One-way ANOVA confirmed significant differences in adsorption capacity and efficiency between treatments (p < 0.001). These findings highlight the effectiveness of calcium modification in enhancing biosorption performance and suggest that calcium-spiked Moringa oleifera seed powder is a promising, low-cost, and environmentally friendly solution for mitigating fluoride contamination in drinking water.

Antibacterial Activity of the Tender Leaf, Stem Bark and Root Extracts of Guizotia Scabra against Streptococci Bacteria Using Bioassay

Mon, 01 Sep 2025 00:00:00 GMT

Antibacterial Activity of the Tender Leaf, Stem Bark and Root Extracts of Guizotia Scabra against Streptococci Bacteria Using Bioassay Paul, Anjeline Jepchumba; Lagat, Grace; Lutta, Samuel Dental caries remains a major public health concern globally, largely attributed to bacterial pathogens such as Streptococcus mutans and Streptococcus sobrinus. The search for plant-based alternatives to synthetic oral care products has intensified in recent years. This study evaluated the antibacterial activity of ethanol and acetone extracts of Guizotia scabra leaf, stem bark and root against these key oral pathogens in comparison with commercial toothpastes. The ethanol leaf extract exhibited the highest activity against Streptococcus mutans with an inhibition zone of 5.0 mm (62.5%), followed by the root extract (3.0 mm, 37.5%) and stem extract (2.0 mm, 25.0%). Against Streptococcus sobrinus., the ethanol leaf extract recorded 4.0 mm (50.0%), root extract 2.5 mm (31.25%), and stem extract 1.5 mm (18.75%). Similarly, the acetone leaf extract demonstrated the highest inhibition against Streptococcus mutans (4.6 mm, 57.5%) and Streptococcus sobrinus. (4.3 mm, 53.75%), compared to the root extract (2.8 mm, 35.0%; 2.3 mm, 28.75%) and stem extract (1.9 mm, 23.75%; 1.7 mm, 21.25%). In contrast, commercial toothpaste brand 1 produced inhibition zones of 6.0 mm (75.0%) against both pathogens, while brand 2 showed 7.0 mm (87.5%) against Streptococcus mutans and 6.0mm (75.0%) against Streptococcus sobrinus. These findings demonstrate that Guizotia scabra extracts possess significant antibacterial activity, with leaf extracts showing the greatest potential. Although commercial toothpastes were more effective likely due to fluoride and other active ingredients. The results highlight the potential of Guizotia scabra as a natural complementary agent for dental caries prevention. Future research should explore its integration with fluoride or other natural antibacterials to enhance its efficacy. Keywords: Antibacterial Activity, Guizotia scabra, Streptococcus mutans & Streptococcus sobrinus bacteria, Bioassay.

Fluoride distribution in selected foodstuffs from Nakuru County, Kenya, and the risk factors for its human overexposure

Sun, 01 Jan 2023 00:00:00 GMT

Fluoride distribution in selected foodstuffs from Nakuru County, Kenya, and the risk factors for its human overexposure Nelima, Delphine; Wambu, Enos W.; Kituyi, John L. Critical data on the impacts of fluoride (F) in food systems along the Eastern Africa Rift Valley System (EARS) is needed for public health risk assessment and for the development of strategies for ameliorating its deleterious effects among the affected communities. Long-term F overexposure causes dental and skeletal fluorosis, and leads to neurotoxicity, which impacts several important body functions. Investigating F exposure pathways is of essence to inform and safeguard public health of the affected communities. The current study assessed the F levels in potatoes (Solanum tuberosum L.), beans (Phaseolus vulgaris L.) and garden peas (Possum sativa) from Nakuru County, Kenya, by potentiometric analysis using F ion-selective electrodes. It then evaluated the risk factors for excessive human exposure to F through contaminated foodstuffs. The mean F levels in the potatoes (8.50 ± 4.70 mg/kg), beans (8.02 ± 4.12 mg/kg) and peas (4.99 ± 1.25 mg/kg) exceeded recommended dietary allowances (RDA) level of 4 mg/kg endorsed by US Institute of Medicine for the different categories of people. The F distribution trends in beans and potatoes reflected the environmental patterns of F contamination of the study area but the spatial extent Fin the peas indicated existence of partial resistance of the pea plants to environmental F uptake. The results indicated that both the beans and the potatoes were more liable to accumulating greater amounts of F from the environment than garden peas and that all the three foodstuffs contained high F levels that posed greater risk of F overexposure and its deleterious impacts among the young children, male populations, and in people of greater body weight and high physical activity levels.

Antioxidant and Antidiabetic Effects of Mondia whitei Root Extract in Streptozotocin-Induced Diabetic Wistar Rats

Wed, 01 Jan 2025 00:00:00 GMT

Antioxidant and Antidiabetic Effects of Mondia whitei Root Extract in Streptozotocin-Induced Diabetic Wistar Rats Gitau, Kennedy K.; et. al... Diabetes mellitus (DM) is a chronic metabolic disorder characterized by persistent hyperglycemia and is a major contributor to global morbidity and mortality. Although Mondia whitei has been traditionally used for its antidiabetic and antioxidant effects, scientific evidence supporting these claims remains limited. This study aimed to evaluate the therapeutic potential of Mondia whitei root extract in a streptozotocin (STZ)-induced diabetic Wistar rat model. Phytochemical screening of M. whitei root extract revealed the presence of saponins, phenols, flavonoids, tannins, alkaloids, glycosides, coumarins, steroids, and terpenoids. Antioxidant activity was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) assays. DM was induced with 65 mg/kg body weight STZ. Rats were grouped into normal control, diabetic control, 200 mg/kg extract, 400 mg/kg extract, and 100 mg/kg metformin treated groups. Treatments were administered orally for 21 days. Fasting blood sugar (FBS) and body weight were measured weekly. At termination, blood and liver tissues were collected for analysis. M. whitei extract exhibited strong antioxidant activity in vitro. The 400 mg/kg dose significantly reduced FBS levels, nearing metformin’s hypoglycemic effect when compared to diabetic control. The extract also significantly lowered serum gamma-glutamyl transferase (GGT), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lipids, and malondialdehyde (MDA), while increasing FRAP values in liver and plasma while serum creatinine and urea levels were reduced, though not significantly. The phytochemical-rich M. whitei root extract showed significant antidiabetic, antioxidant, hypolipidemic, and hepatoprotective activities, supporting its potential as a natural alternative for managing DM and its complications.