Shaping circular economy in the built environment in Africa. A bibliometric analysis

Purpose – This paper aims to explore the intellectual structure shaping the circular economy (CE) discourse withinthe built environmentin Africa. Design/methodology/approach – The study adopted a bibliometric analysis approach to explore the intellectual structure of CE in the built environment in Africa. The authors collected 31 papers published between 2005 and2021 fromtheScopus databaseandused VOSviewerfor data analysis. Findings – The ﬁ ndings show that there are six clusters shaping the intellectual structure: demolition, material recovery and reuse; waste as a resource; cellulose and agro-based materials; resilience and low-carbon footprint; recycling materials; and the fourth industrial revolution. The two most cited scholars had three publications each, while the top journal was Resources , Conservation and Recycling . The dominant concepts included CE, sustainability, alternative materials, waste management, lifecycle, demolition and climate change. The study concludes that there is low CE research output in Africa, which implies that the concept is either novel or facing resistance. Research limitations/implications – The data were drawn from one database, Scopus; hence, adoption of alternative databases such as Web of Science, Google Scholar and Dimensions could potentially © Jacob Mhlanga, Theodore C. Haupt and Claudia Loggia. Published by Emerald Publishing Limited. This article is published under the Creative Commons Attribution (CC BY 4.0) licence. Anyone may reproduce, distribute, translate and create derivative works of this article (for both commercial and non-commercial purposes), subject to full attribution to the original publication and authors. The full terms of this licence may be seen at http://creativecommons.org/licences/by/4.0/legalcode

RQ3. Which are the top journals or conferences publishing the most cited articles?
RQ4.What are the dominant practices and concepts that are shaping the current CE trends in Africa?
By answering these research questions, this study seeks to identify the concepts that are shaping circular construction on the African continent while showing the circularity practices that can be adopted by the various construction stakeholders, such as governments, professionals and contractors.

Literature review 2.1 Transition from linearity to circularity in the construction industry
The construction industry has, for a long time, been characterised by a linear model.A linear approach involves a sequential exploitation of natural resources through extraction, use and disposal (Benachio et al., 2020).The concept does not consider any form of recycling or reuse, which subsequently leads to immense waste generation and pollution (Akhimien et al., 2021;Ranjbari et al., 2021).In response to these findings, Pearce and Turner (1990;p. 35) coined the term "circular economy" in addressing the necessity to extend the useful life of resources to reduce the burden for extracting virgin raw materials.For that reason, the CE is anchored on three fundamental principles: reduce, reuse and recycle (Mahanty et al., 2021;Kirchherr et al., 2017;Anastasiades et al., 2021;Leising et al., 2017).However, Potting et al. (2016) identified 10 Rs: recover, recycle, repurpose, remanufacture, refurbish, repair, reuse, reduce, rethink and refuse, which further gives an in-depth perspective on the circularity approach.Recently, Cimen (2021) coined an eleventh R, called "Replace".The replace principle seeks to pursue total eradication of unsustainable materials within the construction industry while advocating for the adoption of alternative biodegradable materials.For instance, the environmental issues caused by the production of Portland cement have seen advancement in its replacement by waste materials such as fly ash, which is more economical and safer for the environment (Asa et al., 2020).The ultimate goal of these principles and practices is for the industry to rethink the design, operational and waste management strategies.Spreafico (2022) suggests various design strategies that are essential in advancing the circularity agenda.More so, the scholar seems to favour quantitative measures in determining the environmental sustainability resulting from circularity practices in contrast to the widely adopted qualitative approaches.To that end, since the concept of circularity in construction is evolving as practitioners and advocates push for a transition from linearity to circularity, there are a wide variety of both established and emerging practices available for industry to consider in this process.
Regardless of the nobility of the cause of transitioning from linearity to circularity, it appears that the construction industry faces a number of hurdles.Kooter et al. (2021) argued that chief among the hindrances of the transition is the unwillingness of the business owners to change their way of doing business.It is in the same vein that Ghisellini et al. (2016) andG orecki et al. (2018) postulated that business models determined how the companies were likely to adopt circularity.It is apparent that the transformation of the construction industry's business models, which have been mainly characterised by linear practices, would perhaps leapfrog the sector towards circularity.Munaro and Tavares (2021) noted that material passports and government incentives such as subsidies were crucial in leading the construction industry to embrace circular practices.Other barriers include lack of collaboration among stakeholders, limited technology adoption, archaic building codes and unclear financial benefits (Vincevica-Gaile et al., 2021;Mhatre et al., 2021;Hart et al., 2019; Shaping circular economy Antwi-Afari et al., 2021;Çetin et al., 2021;Zami, 2020;Spreafico and Spreafico, 2021).On the other hand, construction professionals such as architects, engineers and quantity surveyors have a large role to play (Al Hosni et al., 2020;Minunno et al., 2020).Central to the role of these professionals is convincing clients to adopt new sustainable means of construction even though the associated costs could be higher compared to the conventional approach at the project inception phase (Lovren ci c Butkovi c et al., 2021;Agyemang et al., 2019).Despite the challenges that could be encountered in the construction industry's transition to circular practices, it is evident that any sustainable future relies mainly on how construction activities pay attention to the sustainability agenda.
2.2 Circular economy in the construction industry: emerging concepts, practices and trends Of late, scholars across the world have been seized with a growing research interest of the CE paradigm.The interest has been largely hinged on the fact that the concept serves as an alternative to the linear model, which is deemed unsustainable (Benachio et al., 2020).Buttressing that observation, Norouzi et al. (2021) and Akhimien et al. (2021) noted that between 2016 and 2017, CE studies skyrocketed as academicians pursued the sustainability agenda.As a result, several CE concepts and trends have arisen.Goyal et al. (2020) identified some of the leading CE concepts as measurement strategies and models, CE and sustainability, level of adoption (company, country and regional), 3R model (reduce, reuse and recycle) and the role played by project design.Furthermore, the study concludes that CE research has been characterised by interdisciplinary collaborations because of how its practices permeate across economic sectors.
On the other hand, Norouzi et al. (2021) and Mhatre et al. (2021) identified the emerging concepts in the construction industry as energy efficiency, waste management, enablers and drivers, end-of-life management, alternative construction materials and circular business models.They recommended that smart or green cities and industry 4.0 be the future trends of the industry.Consequently, Owusu-Manu et al. (2021) identified eight parameters that indicate the greenness of cities; air quality, water, sanitation, land use, health and safety, transportation, energy and building and construction.Therefore, the construction industry has a significant role in shaping smart cities.In tandem with that, Tsai et al. (2020) added that incineration, separation and sorting construction solid waste have also gained focus.Contrariwise, Cimen (2021) argued that incineration produces toxic gases that, in turn, deter the circularity agenda.Rahla et al. (2021) augment the findings of Cimen (2021) by suggesting that instead of thinking about incineration and recycling, the industry should explore eco-friendly materials that are biodegradable.Nevertheless, Akhimien et al. (2021) noted that an increase in scholarly publications had demonstrated heightened awareness of the concept.Despite these practices, Cimen (2021) argued that the construction industry still struggles to implement CE.The fragmentation of the industry has perhaps contributed to this situation.As a result, the concept continues to be explored and new practices are emerging and, at the same time, raising a question about whether the industry would ever become fully circular.
Furthermore, some innovative ways of transforming the construction industry to fully adopt circularity continue to emerge.According to de Azevedo et al. (2021), the use of glass waste to form roof tiles has been developed.Arguably, the approach does address the issue of viewing waste as a resource within the construction sector.The CE concepts have also seen the advancement of alternative materials, particularly to reduce the use of carbon-rich products such as cement and lime.For that reason, Marvila et al. (2021) study on the substitution of lime with waste marble and clay residue mined from rocks proved to be a commendable alternative as long as the mixing proportions were adequately applied.It is JEDT clear that the CE appears to provide a solution for how to deal with the waste materials, which are a significant by-product of conventional construction activities (Galvao et al., 2018;Goyal et al., 2020).The CE concepts are in a rapid state of flux, which requires innovative ways to enable a transforming of the traditionally technology-averse construction industry.

Circular economy practices in the African construction industry: opportunities and challenges
The construction industry has, for a long time, been lagging in adopting new concepts and technologies.Recently, Cimen (2021) reviewed the 2017-2020 articles and concluded that the construction industry is struggling to implement CE principles.Such a position could have been necessitated by the multiplicity of stakeholders in the supply chain.Mahanty et al. (2021) observed a structural shift from 2014 to 2015 in CE studies as more attention was being directed towards the social pillar of sustainability.Arguably, such a shift in research was imperative as it considered problems that bedevilled emerging economies such as Africa.Furthermore, Ranjbari et al. (2021) linked waste management attributes with CE and concluded that, with construction industry's generation of enormous waste, CE might prove a game changer in enhancing sustainability.Charef and Lu (2021) argue that business models and supply chain integration provide the basis for the transition towards adopting CE practices in the construction industry.On the other hand, Tsai et al. (2020), as well as Norouzi et al. (2021), in a 2005-2020 bibliometrics analysis using both Web of Science (WoS) and Scopus databases lament that although CE is receiving much scholarly attention, the African continent is being left behind.Delgado and Oyedele (2020) also argue that the limited use of the building information modelling (BIM) during the operational phase of the buildings has possibly hindered the construction industry transitioning towards circularity.The study further argues that the use of BIM has the potential of enhancing the whole lifecycle perspective among stakeholders of the buildings, thus aiding the circularity trajectory.Since the construction industry is still emerging in Africa, ignoring circularity principles could potentially have detrimental effects on the continent's contribution to the sustainable development goals (SDGs).
The policy direction of the nation informs the direction of the practices within a country.In most cases, policies are informed by research.Contextually, Rademaekers et al. (2020) in their study entitled "Circular Economy in Africa-EU cooperation Continental Report" observe that approximately 96% of the African countries have incorporated at least one CE practice in their policies.For that reason, it is clear that there is growing traction of the concept within the African continent, which perhaps is informed by research in the area spearheaded by collaborations.With regard to collaborative initiatives, Türkeli et al. (2018) focused on CE scientific knowledge in the European Union and China and concluded that for the CE agenda to be permeated globally, there might be a need for collaboration among scholars.Therefore, a series of EU-African collaborative studies were conducted across Africa, and the findings indicated the following key CE practices.
Table 1 illustrates a detailed summary of the practices that are applied by some of the African nations considered to be leaders in the circularity agenda.Evidently, African countries have adopted CE practices at different levels.Nonetheless, some of these practices are fairly new, which has hindered scholars' attempts to ascertain their effectiveness (Mahmoud et al., 2020).These practices, apart from the innovative brick manufacturing, arguably seem to leave much work to be done by the construction industry in terms of fully embracing circularity.For instance, the banning of plastics, importation of materials, revision of building codes and green building certification stem mostly from government The banning of materials that are not bio-degradable allows the construction industry to reduce its impact on the environment (Schmidt et al. 2020;Caschera et al. 2020;Ghosh, 2020) The construction industry produces a vast amount of waste which requires management.Therefore, the adoption of waste management allows the sector to dispose of waste in a responsible manner (Schmidt et al., 2020)

Rwanda
Use of sustainable materials and recycled materials, energy efficiency, environmental performance (green building rating systems), renewable energy, urban forests (green spaces) The use of recycled materials has not been widely adopted in most countries due to various reasons, such as "negative attitude towards waste" and lack of standardisation (Potting et al., 2016).However, Rwanda has shown that the use of these materials reduces a strain on virgin natural resources.Furthermore, reclaiming green spaces allows the cities to restore the ecosystem (Pearlmutter et al., 2020) (continued)

JEDT
policies (Babalola and Harinarain, 2021;Bassi et al., 2021;UNEP, 2018).These practices do agree with the assertion made by Rademaekers et al. (2020) that in their study, a majority of African countries had put policies in place to address issues of circularity.The African continent continues to face both opportunities and challenges in light of adopting CE practices.Some of these opportunities include employment creation, reduction of importing materials, locally available natural resources, agricultural waste materials, construction of low-cost housing, reducing carbon dioxide (CO 2 ) emissions, minimising waste disposal, combatting climate change, cultural conservation, new professions, reclaiming biodiversity and designing out waste (Diaco et al., 2020;Rajput et al., 2020;Pearlmutter, 2020;Meek et al., 2021;Al-Hamrani et al., 2021;Schmidt et al., 2021). Vijaya Prasad et al. (2022) argue that efforts are being made to develop sustainable concrete materials to satisfy the present need of the construction sector, which presents some emerging opportunities within the industry.
The study further identifies geopolymer concrete (GPC) as one of the materials being investigated (Asa et al., 2020).GPC uses alternative binders such as fly ash instead of cement.Therefore, with concrete as a major construction material, sustainable options such as GPC could potentially boost designing for the climate.On the other hand, The recognition of the impact that the construction sector has on the environment is a significant step towards addressing circularity issues.It allows the industry to think in a holistic manner whenever constructing a building (Hossain and Ng, 2019).Therefore, the certification of buildings in view of their impact on the environment has great benefits Zambia Using copper tailings as partial replacement of sand in concrete production The study found out that 30% of sand replacement with copper tailings was the maximum replacement amount to produce optimum compressive strength values from both mixes.With the abundance of copper tailings in Zambia, their use in concrete could increase circularity within the construction industry Source: Adapted from Circular economy in Africa-EU cooperation country reports (2020) and Muleya et al. (2021) Table 1.

Shaping circular economy
that in Zambia due to the abundance of waste copper tailings, there is advanced investigations of replacing sand in concrete aggregates.The opportunities are an indication that the CE within the construction industry is there to enhance the livelihoods of construction stakeholders.
To a greater extent, these practices allow the nation to address the issues of climate change as it limits its reliance on virgin materials (Mahmoud et al., 2020).On the other hand, challenges include inconsistent policies, CE skills deficits, sprouting landfills, misalignment of awareness and implementation (closely linked to policy inconsistency, the industry's failure to embrace the practices as they are not aware of the benefits that accrue due to circularity), archaic building standards void of CE practices (dated building codes that are devoid of recent research output with regard to innovative circular practices), lack of secondary markets (including the establishment of the markets that manufacture and sell recycled materials, which are deemed second-hand materials), informal settlements, low research and development and limited continental standards and assessment indicators (Mahmoud et al., 2020;Hemkhaus et al., 2020).In a bid to address circularity assessment problems, Abadi and Sammuneh (2020) postulated a lifecycle circularity assessment framework.The authors argued that central to the failure of the full adoption of the CE were the lack of a unified industry-wide measurement criterion.Nonetheless, it appears that the stance of both local and central governments in fostering a transition towards circularity cannot be overemphasized (Bolger and Doyon, 2019).Therefore, central government policy inconsistency creates a problem that culminates in the lack of standardisation within the industry.On the other hand, the CE seems to require industry professionals to upskill themselves so that they adopt circular practices within their professions (Edike et al., 2021;Dokter et al., 2021).The retooling of construction professionals calls on both academic and professional regulatory bodies to consider offering learning platforms to raise awareness of these CE practices.Furthermore, in Africa, landfills are a significant problem because of the perception that they are a cheaper way of disposing of waste (UNEP, 2018).For that reason, contractors tend to adopt landfills as a waste disposal strategy even though their ecological challenges are well documented.At the same time, clients seem to possess limited interest in the environmental impact caused by landfill disposal of construction wastes (UNEP, 2018;Tunji-Olayeni et al., 2020).Contextually, these opportunities and challenges inform the direction of future research in the ongoing CE debates that are worth exploring.

Materials and methods
The study adopted a quantitative research method, namely, the bibliometrics approach.The bibliometric analysis method is a useful statistical technique that determines the knowledge base of a scientific area of study (Garfield, 1979).More so, the author further notes that the main assumption of the method is that to ascertain any intellectual structure of a topic of interest, publication citations are a true representation of the ongoing discourse in that study area.Nonetheless, Culnan (1986) argued that the use of citation counts to measure publications' impact in shaping a knowledge structure is dependent on their availability, which potentially limits the effectiveness of the technique.However, in addition to citation counts, van Eck and Waltman (2014) complemented that the method statistically analyses published articles and establishes networks based on co-citations, bibliographic coupling, coauthorship and keyword co-occurrences.The study used the citations, co-citations and cooccurrence options to address its aim.
The study sampled data from the Scopus database.Mongeon and Paul-Hus (2015) suggested that WoS and Scopus are the most popular databases and have a wider global coverage.However, Nobre and Tavares (2017) argued that Scopus has the largest collection of abstracts and citations.For that reason, the researchers used Scopus and followed five steps in data collection and analysis, as shown in Figure 1.JEDT Firstly, the search query was comprised of keywords "circular economy" AND ("construction industry" OR "construction*" OR "building*" OR "built environment") on the topic (Title, Abstract, Keywords).Secondly, the authors limited their search to peerreviewed articles and conference proceedings published between 2005 and 30 August 2021.Thirdly, the results were further filtered to include African countries only.Fourthly, the researcher read the abstracts to ascertain the relevance of each article.Finally, relevant data were exported to VOSviewer version 1.6.16for analysis (VOSviewer, 2020).The VOSviewer software is a mapping tool that allows for visualisation of the networks that exist between the articles (van Eck and Waltman, 2010).
In similar studies, Charef and Lu (2021) used the search query "circular economy" AND ("building" OR "construction industry" OR "built environment") AND "business model" OR "supply chain integration", while Mhatre et al. (2021) adopted "circular economy" AND "construction", "circular economy" AND "built environment" and Norouzi et al. (2021) adopted "circular econom*" AND "building OR construction".Although the keywords from the previous studies were almost identical to those in the current study, the researchers differentiated this study by limiting it to African countries to address the existing gap.Unlike, Charef and Lu (2021)

Results
The data set was comprised of a total of 31 peer-reviewed articles (27 journal articles and four conference proceedings).The data was drawn from eight African countries, namely, Morocco, Egypt, Nigeria, South Africa, Tunisia, Malawi, Kenya and Ghana (as shown in Figure 2).
Upon the retrieval of 31 peer-reviewed articles shaping the CE discourse in the African construction industry, the authors generated a bibliographic coupling network to demonstrate the most influential authors and those that are closely related together.With a bibliographic coupling network, the size of the circle indicates the number of publications that the authors have in the subject area (van Eck and Waltman, 2014).Consequently, those with large circles have published extensively on the subject.The bibliographic coupling network was generated using the documents as a unit of analysis.To further ascertain the level of progression of the CE discourse in the African construction industry, the authors ensured that the year of article's publication was also included in the analysis.The study findings are shown in Figure 3. Additionally, Table 2 highlights the top 10 most influential documents that address the CE within the construction industry in Africa.The full list of the 31 documents can be consulted in Appendix A1 in the Supplementary Materials.
The concept of the CE has experienced exponential growth in the recent past.CE has permeated different industrial sectors, and it was necessary to demonstrate how the same principle has fared within the construction industry between 2005 and 2021.To determine the level of growth of CE, particularly within the construction industry, the authors sorted the 31 articles based on their year of publication.The results are as shown in Figure 4. From the findings, it is apparent that the African construction industry is also experiencing growth in the subject.The first article to be published in the African context was in 2016, while in 2017, there was no activity.Afterwards, from the year 2018 to 30 August 2021, there was a steady growth, which indicates that the concept is gaining momentum among scholars.
The CE is relatively in its infancy within the construction industry.For that reason, knowledge generation continues to evolve.However, to date, there are a number of scholars that have contributed immensely to the current CE discourse in the construction industry  Shaping circular economy such that they have shaped the intellectual structure.To show the current intellectual structure of CE in the construction industry in Africa, the authors selected the co-citation option.The co-citation analysis demonstrates how two publications are simultaneously cited by a single document (Norouzi et al., 2021).The analysis indicated how documents are related through sharing a common subject.In doing so, the co-citation analysis signifies the intellectual structure within the subject area.To generate the co-citation analysis, the authors adopted the co-citation and cited authors as a unit of analysis.The threshold was set at a minimum number of three citations per author.One hundred and seventy-one authors met the threshold (see Appendix A2 in Supplementary Materials).The results yielded the diagram as shown in Figure 5 together with the associated clusters.

JEDT
To demonstrate the most-cited scholars in CE in the construction industry in Africa, Table 3 was generated using the following VOSviewer commands: type of analysis: citations; unit of analysis: authors.The minimum number of documents was set at two and the minimum number of citations at ten.The authors set at two the minimum number of documents so that they show authors who had made some scholarly contribution in the field through repeated publication on the same topic.Mhatre et al. (2021) set their minimum at three publications.Again, the citations were set at 10 as per the authors' discretion seeing that Norouzi et al. (2021) study identified the most influential authors through a minimum citation of at least 100.Therefore, to cater for the possibility of an emerging concept, the authors had to set theirs at a minimum of 10.
Table 3 shows the top ten most cited authors in Africa.Akanbi and Oyedele both had three TP, respectively.The most cited authors per publication (56) were Ajayi, Akinade and Bilal, who published two articles each.The other crucial component is that the area is still in its infancy, as evidenced by the total number of publications from the 10 authors, which cements the positions of Norouzi et al. (2021) and Cimen (2021) that there was more to be done within the CE in construction.The study identifies the contemporary voices in Africa who are shaping circular building.These authors play a critical role in spreading the concept throughout the industry.
To highlight the top journals or conferences that published the most-cited articles in CE in the construction industry in Africa, the authors used the following VOSviewer commands: type of analysis: citations; unit of analysis: sources.The threshold was set at a minimum of one publication.Table 4 highlights the top 10 journals or conferences.
Table 4 highlights the top 10 journals and conferences that cited the most articles.Contrary to the findings by Norouzi et al. (2021) that the Journal of Cleaner Production was the most productive journal in Africa, the leading journal in terms of number of citations is Resources, Conservation and Recycling.This perhaps informs the reason why recycling and reuse have gained more traction than other circularity principles (Diaco et al., 2020).It is also interesting to note that circularity in the construction industry has also permeated other disciplines, such as health.Again, conferences in Africa seem to be shaping the discussion of CE within construction, as evidenced by the IGLC 2018, which linked CE with lean construction.Conferences provide a platform for convergence of both researchers and practitioners to debate emerging concepts.Cellulose is another journal that is worth noting because it seems that more agro-based materials from waste are now being explored in Africa.Notes: TP: total publications; TC: total citations; CPP: citations per publication

Shaping circular economy
There are various practices and concepts that drive the CE within the construction industry.These trends, in turn, highlight the focal points to which both the construction stakeholders and researchers should pay close attention to enable the attainment of circular construction.Although some of the CE practices and concepts are generic, to some extent, there are certain concepts that are contextualised.Premised on that, to identify the CE concepts and practices, the authors adopted the co-occurrence network based on all the keywords.The network mainly addressed the RQ4: What are the dominant practices and concepts that are shaping the current CE trends in Africa?The authors used the following VOSviewer commands: type of analysis: co-occurrence; unit of analysis: all keywords, while the threshold was set at a minimum number of two occurrences of a keyword (see Figure 6).Table 5 provides a list of all the keywords, divided into five clusters based on their cooccurrence.

Discussion
Of the publications retrieved, as shown in Figure 4, the oldest article was published in 2016 by Missaoui and colleagues.Although there was no publication in 2017, the data revealed a   Shaping circular economy steady growth between the years 2018 and 2019.In 2020 a total of 15 articles were published, which represents approximately 49% of the data set.Furthermore, as a build-up to the publication momentum gained in the year 2020, nine articles were already published by 30 August 2021.The findings buttress the studies by Norouzi et al. (2021) and Akhimien et al. (2021), which noted an exponential growth of studies in the area since 2016.Akanbi et al. (2018), as one of the leading authors in the CE in Africa, address issues that relate to the role of BIM being used in the process of enabling the salvaging of waste materials.BIM as a system allows construction professionals to have a virtual view of the lifecycle of buildings (Elmaraghy et al., 2018).Delgado and Oyedele (2020) outlined the extent to which BIM could potentially be a gamechanger in the circularity transition within the construction industry.Potting et al. (2016) noted that the main challenge faced by the construction sector in salvaging materials at the end-of-life is attributed to a reduced appetite by the clients to use second-hand materials.Recycling of materials seems to be taking centre stage in Africa.Interestingly, one of the first authors on the CE in African construction, Missaoui et al. (2016) investigated how to recycle pavers for reuse.The study corroborates the views of various scholars that recycling of construction materials is perceived as the best alternative to extracting raw materials for new buildings (Ranjbari et al., 2021;Cimen, 2021;Mahmoud et al., 2020;Diaco et al., 2020).Demolition, alternative materials and the challenge of the COVID-19 pandemic are part of the issues addressed by CE scholars considering the African continent (Ibn-Mohammed et al., 2021;Limami, 2020;Oumnih, 2019).CE practices appear to be a game changer in addressing a plethora of longstanding challenges within the construction industry, such as waste generation, pollution, material extraction and climate change.Notably, central to the advancement is the employment creation within its value chain, such as waste management and recycling (Edike et al., 2021).Circularity seems to offer opportunities within the construction industry.
However, despite the potential of the concept, the findings also show that CE in the African construction industry is still in its infancy and evolving.Cimen (2021) notes that although the concept is still novel, the main challenge with the construction industry is that it has been a technological laggard (Marvila et al., 2021).However, the current intellectual structure of the CE in the construction industry in Africa, as shown in Figure 2, demonstrates that the sector has been forthcoming in this area.Arguably, these findings indicate that the policies put in place, as highlighted by Rademaekers et al. (2020), are bearing fruit, although the growth is marginal.
Interestingly, Figure 5 shows that there are six common clusters that are shaping African research in the CE based on the co-citation network, and they have been included in: Cluster 1red colour -"demolition, material recovery and reuse".That is the most dominant cluster, with 52 authors and the leading African scholars included, Oyedele, Akanbi and Akinade (Akanbi et al., 2018).Some of the themes include decommission, disassembly, simulation, performance assessment and salvaging (Akanbi et al., 2018(Akanbi et al., , 2019)).Notably, Hemkhaus et al. (2020) and Ranjbari et al. (2021) contended that the construction industry in Africa is contributing to a sizeable amount of demolition waste, and yet there is little reuse of materials.Although it seems that there is activity in the research area on material recovery, Mahmoud et al. (2020) argued that, particularly in Egypt, the CE policies with regard to demolition and waste management are new and have yet to yield any results.Such a situation makes it difficult to ascertain the level of their success.A problem that is likely to inform future studies.
Cluster 2green colourcalled "waste as a resource", which includes themes such as zero waste, alternative materials, residual phosphorous (Taha et al., 2021), flint use, valorisation (El Machi et al., 2021) and environmental protection (Drif et al., 2021).The JEDT concept hinges on the beliefs held by the EMF (2013) and Goyal et al. (2020) that CE should be incorporated within the design stage.However, it seems that in most African countries, waste management is still informal, which deters its use and establishment of secondary markets (Rajput et al., 2020;Potgieter et al., 2020).Such a reality demonstrates an opportunity for reconfiguration of the perceptions of individuals about waste through community engagement and workshops with stakeholders.Cluster 3blue colour -"cellulose and agro-based materials" includes green manufacturing, waste treatment, nanocomposite cellulose (Caschera et al., 2020), cross-laminated secondary timber (Rose et al.,2018), Kenaf fibres, biofibres and biodegradable materials (Ogunbode et al., 2021).These authors seem to be tapping into the knowledge that Africa is largely agro-based, which presents a potential for innovative agro-based construction materials (Caschera et al., 2020).Augmenting these agro-based materials, Schmidt et al. (2020) note that Africa has the potential of optimising its natural agro-based resources through converting them into construction materials (Schmidt et al., 2021).For a continent that is predominantly agrobased, such innovations are likely to enhance circularity.Furthermore, Bonnaire et al. (2020) and Whyte et al. (2020) agree that in Africa, the development of alternative materials from agricultural waste, such as polysaccharides should be explored.
Cluster 4yellow, called "resilience and low carbon footprint", includes sustainability, supply chain resilience, air quality, carbon footprint, transportation and coronavirus disease 2019, popularly known as COVID-19 pandemic (Ibn-Mohammed et al., 2021).The carbon footprint is a significant contributor of climate change (Agyemang et al., 2019).Therefore, a study in this direction is a commendable approach in the attainment of SDGs.Additionally, Mahanty et al. (2021) perceived that although CE has gained traction, environmental sustainability has not been given much attention in the discourse.This observation corroborates the findings of Spreafico ( 2022), who appears to promote the need for a link between CE and environmental sustainability.Therefore, this shows a potential gap that can be further explored within the construction industry.Cluster 5purple "recycling materials" (Edike et al., 2021;Oyinlola et al., 2018;Mahdjoub et al., 2021).The recycling process has gained traction.However, Norouzi et al. (2021) and Mhatre et al. (2021) are of the view that it is an inferior method to reusing because of the energy consumed during the recycling process.The study revealed that in Africa recycling is on the rise, but there seem to be limited standards of the end products, which deter its use.Cluster 6turquoise colour is called the "4th industrial revolution (4IR)" (Hoosain et al., 2020;Turner et al., 2021).Finally, technology is the central part of CE transition.The findings seem to contradict the study by Cimen (2021), who claimed that construction was technology-averse.Nonetheless, Lekan et al. (2021) recommend that the construction sector move towards Construction 4.0 (C4.0) to complement the 4IR.These six clusters demonstrate that Africa is contributing to the CE debate within the construction industry context.
Evidently, CE in the construction industry can be perceived as an evolving concept that is characterised by new principles and practices.For instance, Mahanty et al. (2021) claim that the concept was for a long time characterized by the 3R model (reduce, recycle and reuse) until Potting et al. (2016) noted ten principles.Recently, Cimen (2021) coined the eleventh R called "Replace".Therefore, to ascertain the current trends and future areas to focus on in Africa, the study produced a co-occurrence map on all keywords.Five clusters emerged based on the number of keywords.
Cluster 1red: 17 keywords including CE, compressive strength, wastes and valorisation and alternative materials.The cluster confirmed the urgent call for the construction industry to think of alternative materials and waste management (Bonnaire et al., 2020).However, in other continents, particularly Europe and Asia, alternative Shaping circular economy construction materials are being extensively explored (Marvila et al., 2021).Such advances place Africa in the spotlight to pursue innovative construction materials.The future of construction in Africa seems to be hinging on how well the industry would adapt to innovative methods of construction and materials.
Cluster 2green: 11 keywords including end-of-life, recycling, sustainability and innovation.Galvao et al. (2018) view the CE and sustainability as complementary concepts.To put it another way, the CE exists to make sustainability a reality in the construction industry.Furthermore, as the CE is continually evolving, innovation appears to be its backbone.The innovativeness of the sector has seen the emergence of different types of materials being developed.Cimen is of the view that recycling coupled with end-of-life thinking has a great potential in advancing the circularity trajectory.Notably, other continents, such as Europe, are already advanced in the use of technologies that address both circularity and end-of-life thinking (Marvila et al., 2021).The African continent cannot afford to remain behind.
Cluster 3blue: ten keywords including architectural design, construction and demolition and waste.CE principles appear to affect the entire lifecycle of the projects.Nonetheless, designing circular projects affords the concept a better chance of succeeding within construction (Goyal et al., 2020).The design stage detects the nature of waste products.In other words, the designers have a key role to play in the movement of circularity.However, Dokter et al. (2021) note that the clients tend to be focused on the amount that is incurred during the construction, which determines their appetite for adopting circular practices.Studies do reveal that circular-based construction is expensive at inception, but the accrued benefits to both the economy and environment far outweigh conventional construction techniques (Patwa et al., 2021;Galvao et al., 2018).
Cluster 4yellow: nine keywords including climate change and human and viral disease.Due to lockdown restrictions imposed to curtail the COVID-19 pandemic, supply chains were allegedly disrupted, resulting in the utilisation of local products.The restrictions may have had a favourable impact on decreasing carbon emissions that contribute to climate change (Babalola and Harinarain, 2021;Hemkhaus et al., 2020).Ibn-Mohammed et al. (2021) argue that COVID-19, although it affected the livelihood of humans across the globe, also presented the world with the opportunity to rethink how it affects the environment.With limited transport mobility due to lockdowns, cities arguably became "clean cities" (Owusu-Manu et al., 2021).Some of the lessons from that experience which could be adopted in construction include the use of clean energies so that the industry contributes meaningfully to the climate change agenda.
Finally, Cluster 5purple: seven keywords including of additives, life cycle and phosphogypsum.There is an ongoing debate about how to replace concrete as a construction material because of its climate-changing impacts due to carbon dioxide emissions (Al-Hamrani et al., 2021).The study suggests that Africa has also joined the discourse.However, contrary to Mahanty et al. (2021), who found a correlation between social sustainability and CE, such a link is lacking in Africa.Given the severity of Africa's social problems, it is critical to expand research in this area.

Conclusions
The CE in the construction industry remains inadequately explored in Africa.The study analysed 31 articles that were published from 2005 to 2021 and shows that the concept remains relatively new in Africa.Although that is the case, it seems that most African countries have incorporated CE principles in their policies.Nonetheless, these policies are still new for one to ascertain their effectiveness.JEDT Furthermore, of the articles analysed, the six clusters, "demolition, material recovery and reuse", "waste as a resource", "cellulose and agro-based materials", "resilience and low carbon footprint", "recycling materials" and "4th industrial revolution" are shaping CE knowledge in the construction industry in Africa.
The most-cited authors in Africa include Akanbi, Oyedele, Ajayi, Akinade and Bilal.Although these authors were most cited, they had articles ranging between two and three.It should be noted that regardless of the low research output, these leading authors are making significant contributions to the ongoing circularity discourse from an African perspective.Having African contribution is of paramount importance in unravelling to the world how the continent addresses the transition from linearity to circular practices.
Evidently, the number of CE publications is quite low, ranging between two and four.This is, perhaps, a matter of concern, particularly in terms of furthering circularity.In theory, the study demonstrates that CE research output in the African construction sector is low, revealing possible gaps in the area that might be studied to expose circularity inclinations across the continent.In terms of practice, the study suggests circularity practices that might inform policy formulation and industry restructuring.
This study made a significant contribution by articulating the CE's intellectual structure, identifying prominent scholars and highlighting platforms responsible for bringing Africa towards circularity, as well as providing concepts that will shape future trends.It should be noted that the current study used the Scopus database because of its enormous collection of abstracts and citations, which may have limited the number of articles reviewed.Finally, further study on CE in construction should be conducted using alternative databases such as WoS, Google Scholar and Dimensions to ensure a comprehensive bibliometric analysis and ascertaining of the implementation of the concept in Africa.Note: Search string: TITLE-ABS-KEY ("circular economy" AND ("construction industry" OR "construction*" OR "building*" OR "built environment")) Table A1. JEDT , who focused mostly on factors, Mhatre et al. (2021) and Norouzi et al. (2021) paid attention on the CE practices in the building sector, and they both included articles published from Africa.Nonetheless, in their analyses, these scholars concentrated more on publications with high publications and citations indices, which obscured the focus of African scholars.Furthermore, both these studies identified some of the influential scholars in Africa as Akinade O.O, Bilal M. and Clinton A.O.
Figure 1.Overview of the data mining procedure Figure 2. The summary of the CE in construction industry publications inAfrica (2005Africa ( -2021)   ) Figure 4.The evolution of CE publications in the construction industry in Africa (2005-2021) Figure 6.The map based on the co-occurrence of all the keywords (2005-2021)

Table 2 .
Top Akanbi et al. (2018) Salvaging building materials in a circular economy: A BIM-based whole-life performance estimator Resources, Conservation and Recycling Ibn-Mohammed et al. (2021) A critical review of the impacts of COVID-19 on the global economy and ecosystems and opportunities for circular economy strategies Resources, Conservation and Recycling Mabroum et al. (2020) Elaboration of geopolymers based on clays by-products from phosphate mines for construction applications