Where are the Barriers to Sustainable Construction in Africa?Key Note Speech

The construction industry is very resource intensive. At every stage of a project lifecycle, huge pressures are exerted on the natural environment for materials, where raw materials are extracted, delivered to factories, manufactured into building materials, and delivered to construction sites. The construction and post construction use of buildings up to demolition stage involve the consumption of huge volumes of materials and generation of much waste in the process

Potential of Anthill Soil as a Pozzolan in Concrete

Cement is the most utilised construction material and the second most consumed commodity in the world after water. It has been reported that the heavily energy-intensive processes that are involved in its production account for about 7 to 10 % of the total global anthropogenic carbon dioxide (CO2), which is the main cause of climate change; and are also expensive economically. Energy and cost efficiency can however be achieved by reducing on the amount of clinker, and in its place utilising pozzolans, which require less process heating and emit lower levels of CO2. This research aimed to provide an original contribution to the body of knowledge by investigating Anthill Soil (AHS) for pozzolanic properties. Cement was replaced in concrete with AHS by weight using 5% increments by weight, from 0 to 30% at the point of need. Durability was investigated using the water absorption and sulfate tests. Results of the chemical analysis by X-Ray Diffraction (XRD) showed that AHS contained the chemical composition required for pozzolans, and the compressive strengths achieved were for classes that are listed by standards as being durable and suitable for structural applications. The behaviour of AHS in workability, density, gain in compressive strength over time, water absorption and sulfate tests were also consistent with the characteristics of pozzolans, leading to a conclusion that it may be suitable for use as a pozzolan to improve the properties of concrete, reduce on the harmful effects of cement production to the environment and lower the overall cost of concrete, allowing for the construction of low cost buildings

Bibliometric analysis for reviewing published studies in the built environment

Literature review is generally one of the key steps in conducting a scientific research. The overwhelming amount of literature may require significant effort to sort out, screen, and analyse before generating useful information and achieving research objectives in any scholarly work within a given domain. As the text-mining-featured analysis tools (e.g., VosViewer) become available for visualizing and analysing secondary data sources (e.g., literature), the bibliometric analysis is becoming one of the widely adopted methods in reviewing literature, especially for a large amount of secondary sources. In this chapter, bibliometric analysis is firstly defined. The rationale for adopting them when conducting literature review is described. The existing software tools for conducting the text-mining-based analysis (e.g., VosViewer, Gephi, etc.) are introduced. Using two cases in the subject of built environment, the detailed workflow of conducting the science mapping approach involving bibliometric analysis is also described. The network analysis using one of the bibliometric analysis tools (i.e., VosViewer) is showcased. Finally, the general guidance of conducting a bibliometric analysis is summarised, with recommendations provided and common mistakes described

A Critical Analysis Of Collaborative And Disruptive Digital-Driven Built Environment Education

The Covid-19 pandemic has driven the teaching and learning provisions more towards virtual platforms, exposing lack of resilience and technology preparedness. This study aims to provide a critical appraisal of existing pedagogical studies on built environment (e.g., Building Information Modelling or BIM) challenging the opportunism and agency theories in response towards remote education provision provoked by the pandemic. The study consists of critical review of two literature samples, namely how the education sector as a whole has been responding to the pandemic, and the digitalisation-based pedagogy in built environment especially how the pedagogy addresses the pandemic. The review of the second literature sample evaluates longitudinally how BIM-based built environment education had evolved. A conceptual framework incorporating multiple factors from the review of the two literature samples is finally proposed. These factors include educational theories (e.g., Bloom’s Taxonomy), curriculum development addressing assessment, student experience, collaborative learning, delivery approaches, and teaching methods. This review-based study not only provides an overview of the digital built environment pedagogical work in higher education, but also contests the opportunism response to remote or blended learning and how the post-pandemic era could embrace the remote delivery-platforms to engender a variety of pedagogical principles, for example, cross-disciplinary team-based information sharing, experiential learning, and project-based learning. The findings of this study represent a barometer and roadmap for measuring the resilience of higher education and built environment programmes towards pandemic and technological disruptions

Influence of Rice Husk Ash Density on the Workability and Strength of Structural Concrete

Supplementary cementitious materials (SCMs) have been known to improve the properties of fresh and hardened concrete, and at the same time enhance the sustainability of concrete. Rice husk Ash (RHA), is one such material, but has neither been widely studied nor applied in practice. This work investigated the effect of the density of RHA on the workability and compressive strength of fresh and hardened RHA-replaced concrete respectively. Cement was replaced with RHA in concrete by weight (RHA-W) and by volume (RHA-V) at steps of 0%, 5%, 7.5%, 10%, 15%, 20%, 25% and 30%. The 0% replacement was used as the reference point from which performances were measured. Results showed that unlike the characteristic of other established pozzolans, RHA significantly reduced the workability of wet concrete and the rate of compressive strength gain over curing time due to a high water demand that is caused by the increased volume of replaced concrete, which results from its low density. Workability reduced with increased replacement for both RHA-W and RHA-V. Replacements of above 15% were not possible for the RHA-W due to the high water demand. However, replacements of up to 30% were achieved for the RHA-V. RHA-W specimens achieved lower compressive strengths and were observed to gain strength at a lower rate over the 28 to 91-days period of curing compared to RHA-V specimens. This behavior was attributed to the shortage of water that is necessary for the hydration of cement and subsequent pozzolanic reaction, which is the basis of the contribution that is made to the strength and performance of concrete by SCMs. However, the compressive strengths achieved were above the study’s target concrete strength of class C32/40 at 91 days, which is among those classes that are listed as being durable and suitable for structural applications. A conclusion that RHA should supplement cements by volumetric replacement rather than simple substitution by weight was drawn

Modern Methods Of Construction A Technique In Achieving Affordable Housing In Nigeria

The urban environment in Nigeria accounts for over 51.16% of the population and is the main source of economic development within the country. With the increase in population as a result of rural-urban migration, population growth, urban development, decrease in mortality rate amongst others, there is a need for affordable housing provision. It is has been argued based on extensive research, that the development of good housing and infrastructure, can increase the average life expectancy of people, quality of life, increase the health standard and also attract investment and thus, further develop the economy. Unfortunately, the discourse on affordable housing has not developed a model that meets the Nigerian urban populace that is in desperate need of housing. With a larger percentage of Nigerians living in these areas, coupled with the continual rise in rural-urban migration, it is imperative to ensure that focus should be placed on the developing modern methods of construction (MMC) that can meet housing needs. Modern methods of construction is a broad terminology that embraces a variety of offsite manufacturing and onsite practices that provides a range of options to traditional house buildings. It is in light of these facts, this paper analyses the effects of affordable housing in the urban environment and the role MMC plays in its development. This qualitative study is based on current knowledge from preliminary research, analysing how affordable housing can be achieved with MMC. The conclusion of this research will suggest the benefits of MMC practices and create an avenue for further research on affordable housing

Performance of Class F Pulverised Fuel Ash and Ground Granulated Blast Furnace Slag in Ternary Concrete Mixes

Cement is the most utilised material after water, and the processes that are involved in making it are energy intensive, contributing to about 7% of the total global anthropogenic carbon dioxide (CO2). Energy efficiency can however be achieved by using Supplementary Cementitious Materials (SCMs) such as Pulverised Fuel Ash (PFA) and Ground Granulated Blast Furnace Slag (GGBS) which demand less process heating and emit fewer levels of CO2. This work examined the advantages of substituting cement using PFA and GGBS in ternary (2 SCMs) concrete at steps of 0%, 5%, 7.5%, 10%, 15%, 20%, 25%, and 30%. It was found that PFA increased the workability of GGBS, whereas GGBS improved the strength of PFA. The densities of the resultant concrete were below those of the 0% replacement as well as those of individual binary (1 SCM) concretes. The tensile strengths of the ternary concrete were lower than those of the binary concretes, whereas the gains in compressive strengths over curing time were higher at lower replacements for the ternary concrete compared with the 0% replacement and the binary concretes, but lower at higher replacements. The findings indicate that PFA and GGBS could be used together to improve the properties of concrete where each falls short

Suitability of Corncob Ash as a supplementary Cementitious Material

Cement is the most utilized construction material, and the second most consumed commodity in the world after water. Its demand has soared proportionately with the exponential rise in population in a bid to match the required development. The heavily energy-intensive processes that are involved in its production contribute to about 7 to 10 per cent (%) of the total global emissions, with potentially adverse environmental implications, and are also economically expensive. These processes, and generally those of the production of concrete consume heavily on natural resources such as sand, gravel, water, coal and crushed rock, mining of which mars the environment. It is however possible, that energy and cost efficiency can be achieved by reducing on the amount of clinker, and in its place utilising supplementary cementitious materials (SCMs) that require less process heating and emit fewer levels of carbon dioxide (CO2). This study investigated the ability of corncob ash (CCA) to be used as a SCM by testing for pozzolanic or hydraulic properties and performance in sulfate environments. Experiments were carried our by supplementing cement by weight in concrete mixes with CCA at 5%, 7.5%, 10%, 15%, 20%, 25% and 30% steps at the point of need. Results were compared with a control specimen, which was made with 100% cement. Durability was tested using the sulfate elongation test. The results showed impressive compressive strengths that were suitable for structural applications. It was concluded from the sulfate elongation test that CCA supplemented concrete could be used in aggressive environments with an advantage. The results showed good repeatability and highlight the potential of CCA as an effective pozzolan, which could enhance the sustainability and economic aspect of concrete, as well as improve its properties in both the wet and hardened states

Permeability of Corncob Ash, Anthill soils and Rice husk replaced concrete

Durability of concrete is defined as its ability to resist any form of deterioration, allowing it to retain its original form and quality after exposure to the environment of its intended use. Permeability is the most important aspect of durability and service lives of concrete structures, and is measured by the ease with which a gas or liquid can get into and pass through concrete, or rate at which water under pressure can flow through interconnected voids within concrete. It has been suggested that pozzolanic reactions from Supplementary Cementitious Materials (SCMs) help in filling up pores using the Calcium Silicate Hydrate (C-S-H) gel that is formed during the secondary hydration of cement, through the reaction of calcium hydrixide [Ca(OH)2] with silicon dioxide (SiO2), which densifies the pore structure and transition zone, thereby reducing permeability from the packing effect of unreacted particles. This work investigated the water absorption performance of Corncob Ash (CCA), Anthill Soil (AHS) and Rice Husk Ash (RHA) concrete specimens. Tests were conducted on specimens that were found to have achieved the highest compressive strengths from strength tests and also on specimens that were made out of 30% (per cent) cement replacements. Results indicated that the water performance of all the three materials, including that of the ternary specimens of CCA and AHS were above those of the control specimens at highest compressive strength, and highlight the potential of using CCA, AHS and RHA at lower replacements to improve the durability of concrete

Viability of using Corncob Ash as a Pozzolan in Concrete

Cement is the most utilised construction material, its global consumption only seconding that of water. Its demand has soared proportionately with the exponential rise in population to match required development. The heavily energy-intensive processes that are involved in its production contribute to about 7% (per cent) to 10% of the total global carbon dioxide (CO2) emissions, with potentially adverse environmental implications and are economically expensive. These processes, and those of the production of concrete consume heavily on natural resources such as sand, gravel, water, coal and crushed rock, the mining of which mars the environment. It is however possible, that energy and cost efficiency can be achieved by reducing on the amount of clinker, and in its place utilizing pozolanic materials that require less process heating and emit fewer levels of CO2. This study investigated the viability of corncob ash for use as a pozzolan in concrete. Tests were carried our by replacing cement by weight in concrete mixes with corncob ash at 5%, 7.5%, 10%, 15% and 20%steps at the point of need. The results were compared with a control specimen that was made with 100% cement (0% CCA). Durability was tested using the sulfate elongation test on specimens that were immersed in a 5% sodium sulfate (Na2SO4) solution. From the results, all replacements achieved impressive compressive strengths that were suitable for structural applications, while the sulfate elongation tests showed that CCA could be used in Na2SO4 aggressive environments with an advantage. The findings also showed good repeatability and highlighted the potential of CCA to be used as an effective pozzolan in concrete