Research Article
Performance Indices Assessment of Blended Groundnut Shell and Rice Husk Ashes as Stabilizers for Agbede Soil
Ibrahim Abdulrazaq Olayinka*
,
Olugbenga Ifabiyi,
Wasiu John,
Ogbebor John Imentinyan
Issue:
Volume 11, Issue 3, September 2026
Pages:
61-75
Received:
20 April 2026
Accepted:
25 July 2026
Published:
22 August 2026
Abstract: Expansive soils in Nigeria, such as Agbede soil, are generally unsuitable for engineering applications due to their high plasticity, volumetric instability, and low load-bearing capacity. Although conventional stabilizers like cement and lime are effective, their high cost and environmental impacts necessitate the exploration of sustainable alternatives. This study evaluates the geotechnical performance of Agbede soil stabilized with groundnut shell ash (GSA) and rice husk ash (RHA), individually and in blended proportions, as eco-friendly and cost-effective stabilizing agents. Laboratory investigations were carried out in accordance with BS 1377 (1990) standards and included particle size distribution, specific gravity, Atterberg limits, Standard Proctor compaction, California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS), and microstructural analysis using Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM/EDX). The natural Agbede soil was classified as a highly plastic clay with a plasticity index (PI) of 32%, a maximum dry density (MDD) of 1.85 g/cm3, and low strength characteristics, confirming its inadequacy for direct use in highway subgrade construction. The incorporation of GSA and RHA resulted in progressive improvement of the soil’s engineering properties. Plasticity was significantly reduced, with the PI decreasing to 14% at a 15% GSA content. Compaction characteristics improved, as the MDD increased to a peak value of 1.92 g/cm3 at 10% GSA, while the optimum moisture content (OMC) decreased from 14.3% for the untreated soil to 13.5%. Strength performance improved markedly, with CBR values increasing from 7% to 21% for GSA-treated soil and reaching up to 24% for blended GSA–RHA mixtures. Similarly, UCS values increased from 120 kN/m² in the untreated soil to 280 kN/m² at 15% GSA. SEM/EDX analysis confirmed the formation of cementitious compounds, particularly calcium silicate hydrates, which enhanced inter-particle bonding and reduced pore spaces. The study concludes that groundnut shell ash and rice husk ash are viable, sustainable, and effective stabilizers for expansive soils. Their application significantly improves strength, durability, and overall geotechnical performance while contributing to agricultural waste management. An optimal blend of 10% GSA and 10% RHA was identified as providing a balanced combination of mechanical performance and constructability, making the stabilized soil suitable for subgrade and other highway engineering applications.
Abstract: Expansive soils in Nigeria, such as Agbede soil, are generally unsuitable for engineering applications due to their high plasticity, volumetric instability, and low load-bearing capacity. Although conventional stabilizers like cement and lime are effective, their high cost and environmental impacts necessitate the exploration of sustainable alterna...
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Research Article
A Multi‑pollutant Ventilation Strategy Under the Indoor Air Quality Procedure for Single‑family Houses
Qiwen Jiang*
Issue:
Volume 11, Issue 3, September 2026
Pages:
76-83
Received:
1 August 2026
Accepted:
11 August 2026
Published:
8 September 2026
Abstract: Balancing energy consumption and indoor air quality (IAQ) in single‑family houses is challenging because cooking‑generated PM2.5 and volatile organic compounds (VOCs) are episodic and occupancy‑dependent, and prescriptive ventilation rates cannot follow these transient loads. The ASHRAE 62.1 Indoor Air Quality Procedure (IAQP) offers a performance‑based alternative that permits reduced ventilation when contaminant levels remain within limits, but a validated residential strategy that combines real‑time occupancy with continuous CO2, PM2.5, and VOC sensing has not been demonstrated. This study proposes an occupancy–indoor environmental quality (OCC‑IEQ) strategy and evaluates it alongside fixed‑thermostat, schedule‑based (SCH), and occupancy‑triggered (OCC) controls using a co‑simulation of a multi‑zone house. The strategies are assessed against IAQ limits of PM2.5 ≤ 15 µg/m3, CO2 ≤ 900 ppm, and TVOC ≤ 500 µg/m3, with a minimum energy saving target of 15%. The OCC‑IEQ strategy achieves a 33.3 % reduction in annual HVAC energy cost, and maintains all three pollutants within limits. The schedule‑based and occupancy‑triggered strategies failed to control PM2.5, and the occupancy‑triggered strategy yielded limited energy savings due to overnight temperature drift. By treating permissible concentration bands as an operational resource, OCC‑IEQ dynamically modulates the outdoor air fraction to balance energy efficiency and indoor air quality protection. These findings demonstrate that a performance‑based multi‑pollutant ventilation strategy guided by the IAQP can achieve substantial energy savings and comprehensive IAQ compliance in dwellings.
Abstract: Balancing energy consumption and indoor air quality (IAQ) in single‑family houses is challenging because cooking‑generated PM2.5 and volatile organic compounds (VOCs) are episodic and occupancy‑dependent, and prescriptive ventilation rates cannot follow these transient loads. The ASHRAE 62.1 Indoor Air Quality Procedure (IAQP) offers a performance‑...
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