Browsing by Author "Onyenokporo, Nwakaego"

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    Exploring Rice Husk Ash As A Supplementary Cementitious Material And Its Impact On Building Energy Performance
    (De Montfort University, 2023-10) Onyenokporo, Nwakaego
    Global cement production is responsible for 5-7% of anthropogenic greenhouse gases produced annually and is one of the biggest contributors to the reduction of finite natural resources. This excessive production and utilisation of cement is currently considered unsustainable due to its negative impacts on the environment, especially with regard to climate change and its resulting effects. Alternative measures have been recommended to reduce the negative impact of cement production. One of these alternatives is the use of supplementary cementitious materials (SCMs) for the partial replacement of cement in construction. Rice husks, an agricultural waste, are one of these SCMs and have been selected for this study due to the large quantities being produced in the study context and their ability to combine with hydrated cement to form compounds possessing cementing properties. In addition to rising global cement consumption and waste production, energy consumption is also rising. Building operations account for 55% of global energy consumption. As the building envelope is a major contributor to building energy performance, especially the external walls, its optimisation is therefore imperative to reduce energy consumption and carbon dioxide emissions. This research aimed to critically investigate the use of Nigerian rice husk ash as a supplementary cementitious material, its influence on the thermal properties of sandcrete blocks, and the resulting impact on building energy performance. A mix of methods, including observations, surveys (questionnaires and interviews), experimental investigation, and simulation study, were employed for this study to properly address each of the objectives set out. The results of the interviews and questionnaires served to provide evidence on the perceptions of householders and building professionals on the use of rice husk ash (RHA) and RHA blended blocks and also gather reasons for its low utilisation from building experts and researchers who have done similar studies. The environmental investigation included the production of RHA using rice husks from a major rice mill in Nigeria to justify rice husk ash as a suitable supplementary cementitious material for partial cement replacement. The production of the RHA masonry blocks followed, and tests were conducted in line with the research questions set out for this study to determine the effects of Nigerian rice husk ash on the physical and thermal properties of sandcrete blocks. Amorphous RHA was produced, which complied with the ASTM C618-19 standard for testing and utilisation of SCMs. Three variations of RHA block samples were then created for this investigation: RHA 5%, RHA 10%, and RHA 15%. For the three variations used, RHA15% recorded the best thermal performance when compared to the control sample. It recorded a U-value of 3.04 W/m2K. This was followed by the RHA10%, which recorded a U-value of 3.34 W/m2K. The average values for RHA5% did not record any significant difference in thermal properties when compared to the control sample, which had a U-value of 3.67 W/m2K. The building simulation results helped quantify the improvements to building energy performance from reuse of the rice waste using prototype buildings from the study context (a bungalow and a duplex/storey building). The largest improvement to the building fabric was recorded with the RHA15% blocks, which resulted in a 9.9% and 11.3% reduction in solar heat gains through the external walls for the bungalow and duplex/storey building, respectively. This led to a 6.55% and 4.2% reduction in cooling loads and a 4.1% and 2.8% reduction in CO2 emissions, respectively, for the bungalow and duplex/storey building. Furthermore, questionnaires and interviews revealed that participants would readily use the RHA blended blocks if they were inexpensive, strong enough for use, and blended well with other materials. The outcomes of this research will prove useful to householders, researchers, architects, and policymakers in their decision-making processes, and will be valuable in bridging the knowledge gap as well as introducing new methods that can be adopted for similar studies.
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    Thermal Characterisation of composite walls made from waste Materials
    (2022-08-10) Messahel, Bilal; Onyenokporo, Nwakaego; Beizaee, Arash; Oyinlola, M. A.
    Sustainable development has been an ever-growing global concern over the years, especially with respect to the environment. The construction sector is a major cause for concern due to the devastating effects traditional building materials, manufacturing processes and procurement, have on the environment. Inadequate housing in developing countries is also another major sustainable development challenge. These illustrate the cogent need for developing new methods of delivering sustainable housing that can be accessible to low-income communities who have little or no access to finances. This study compares the thermal performance of low-cost building components made from incorporating waste materials in cement blocks, thereby reducing the quantity of new materials needed. Three samples (wall panels) were made. Each panel was 330mm × 330mm × 240mm and incorporated 25 × 500ml plastic bottles laid horizontally in rows. A sand and cement mixture (ratio 1:3) was used as a binder and filled the gaps between the plastic bottles. The bottles in the first sample were filled with sand, those in the second were filled with water, and those in the third with used plastic carrier bags. A guarded hot box was developed to experimentally measure the U-values of the samples following the BS EN ISO 8990 standards. It was observed that the samples with the plastic bags had the lowest U-value, about 60% lower than samples with sand. The results show a promising potential for low-grade plastic waste to be used as a means of improving the thermal performance of low-cost buildings.
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    Thermal Comfort Perception of Occupants in an Upcycled Bottle House in Abuja, Nigeria.
    (2023-06) Oyinlola, M. A.; Beizaee, Arash; Onyenokporo, Nwakaego; Takyie, Emefa; Adekeye, Olutola
    Several studies have shown that the use of upcycled materials for construction is a viable intervention for delivering affordable and adequate housing in low-income communities. However, information regarding in-situ performance of buildings made from upcycled materials is scarce in the literature. This paper compares the thermal performance of a building with walls made of sand-filled plastic bottles (Bottle House) with two other conventional buildings, one made of mud bricks (Mud House) and another made of sandcrete blocks (Cement House). In order to obtain the thermal sensation vote (TSV) of the occupants, thermal comfort questionnaires were developed based on ISO 7730 standard using the seven-point ASHRAE thermal sensation scale. Also, a Testo 480 multifunction meter which comprised of an anemometer, radiant globe thermometer, air thermometer, and Relative Humidity probe, was used to concurrently calculate the predicted mean vote (PMV). From the results of the thermal sensation votes (TSV) based on occupant’s survey, mean vote from participants of -2.0, 2.0 and 2.5 were observed for the bottle house, mud house and cement house respectively. In comparison, using the extended PMV thermal comfort model better suited for non-air-conditioned buildings in warm climates, adjusted PMV mean values of 1.9, 2.1 and 2.1 were recorded for the bottle house, mud house and cement house respectively. The TSV and PMV results both indicate that occupants of the bottle house felt more thermally comfortable when compared to occupants in the other dwellings. The results of this paper will provide evidence on the prospects of upcycling plastic waste for construction and its impact on occupant’s thermal comfort when compared to conventional building materials.
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    Thermal performance characterization of cement-based masonry blocks incorporating rice husk ash
    (Elsevier, 2023-07-21) Onyenokporo, Nwakaego; Taki, A. H.; Zapata, Luis; Oyinlola, M. A.
    Owing to climate change and its effects, interest has grown in finding alternative building materials to improve the energy efficiency of building envelopes and reduce CO2 emissions and costs. This study focuses on the thermal performance of cement-based masonry blocks, which are popular in many parts of the world for masonry wall construction. Masonry blocks were incorporated with rice husks, which are agricultural wastes commonly found in tropical countries and are usually dumped in landfills. Previous research on the use of rice husk ash (RHA) for construction purposes has focused on the durability properties of the product without much consideration for properties such as thermal conductivity or thermal transmittance coefficient (U-value), which are important for quantifying the overall energy performance of buildings. High U-values of building elements typically result in high heat gains in tropical countries, which increases the use of mechanical cooling systems to improve occupants’ thermal comfort, thereby increasing building energy consumption. The study involved an experimental investigation using the laboratory hot box and heat flow metre method for U-value measurements in accordance with BS EN ISO 8990 and 9869. Several samples were prepared by partially replacing Portland cement with 5%, 10%, and 15% RHA by weight of cement. The results reflect up to a 17% reduction in the U values and thermal conductivities of all block samples. The lowest value of 3.04 W/m2K was obtained from RHA 15% compared to 3.67 W/m2K from the control sample. The results of this study show the prospects of improving building energy consumption, occupants’ thermal comfort, and building CO2 emissions using masonry blocks incorporating RHA for external building walls in tropical countries.
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    Upcycled construction materials to reduce dwelling overheating in tropical climates: The bottle house
    (Elsevier, 2023-03-06) Roberts, Ben; Beizaee, Arash; Onyenokporo, Nwakaego; Oyinlola, M. A.
    Component testing indicates that overheating in tropical buildings could be reduced using walls built from upcycled sand-filled plastic bottles, which also reduces building costs and prevents waste from polluting the environment. It is not yet known, however, how these bottle-composite walls influence thermal comfort in dwellings in-situ. This study presents the world's first in-situ measurement of indoor temperature in a “bottle house” which is compared to four other traditional dwellings, two with mud walls and two with sandcrete walls, over a 76-day monitoring period between April and June 2019. Aside from the wall and ceiling construction, the dwellings were otherwise similar in design and located in the same settlement in Abuja, Nigeria. The results showed that on average the bottle house was 2.4 °C cooler than the hottest mud dwelling and 1.8 °C cooler than the hottest sandcrete dwelling. Overheating, determined using the adaptive thermal comfort criteria, occurred in all five dwellings but was lowest in the bottle house. On the day with the highest maximum outdoor temperature (38.2 °C), the bottle house was the coolest dwelling during night time sleeping hours and was 3.4 °C cooler than the hottest mud dwelling during daytime waking hours, although 2.0 °C warmer than the coolest house, which had sandcrete walls. Thus, bottle-composite walls could be a suitable low-cost construction method which contributes to reducing overheating in tropical climates but require additional heat mitigation measures to reduce indoor temperatures to comfortable levels on the hottest days.
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    Upcycling Agricultural and Plastic Waste for Sustainable Construction: A review
    (Taylor and Francis, 2023-01-30) Messahel, Bilal; Onyenokporo, Nwakaego; Takyie, Emefa; Beizaee, Arash; Oyinlola, M. A.
    The production of conventional construction materials such as concrete, cement, and bricks, has contributed significantly to the high environmental footprint associated with the construction industry. Moreover, there is a global push to deviate from the linear take-use-dispose model to a circular economy model, which incorporates upcycling and reuse of materials. This paper reviews the application of agricultural and plastic wastes, in construction, exploring the performance of the resulting component using five key parameters: compressive strength, tensile strength, flexural strength, density, and thermal conductivity. The study showed that the compressive, tensile, and flexural strengths can be increased slightly by increasing waste content, however, this only occurs in a narrow range after which an increase in waste content reduces the mechanical strength. This reduced strength can be attributed to a weaker bond resulting from the increased waste content. It also suggests that components may not directly benefit from the mechanical properties of waste materials. The waste materials resulted in a lower density which has implications for lightweight applications. Similarly, both waste materials were observed to improve the thermal insulation properties which is an advantage for improving thermal comfort in buildings. Despite the reduction in mechanical strength, it was observed that components with waste materials can be used for non-structural elements, thereby reducing the quantity and cost of new materials to be used. The application of these wastes in construction offers a pathway to reducing the environmental impact of construction, avoiding reliance on landfills for waste disposal, and reducing construction costs.