Circular Economy: Challenges and Opportunities in the Construction Sector of Kazakhstan

Selection of Circular Proposals in Building Projects: An MCDM Model for Lifecycle Circularity Assessments Using AHP

The circular economy (CE) in construction literature engages with individual CE concepts, mostly at the ‘macro’/‘meso’ levels, and lacks holistic frameworks of indicators for circularity assessments (CAs) to inform decision-making at the ‘micro’ (project) level. This article presents a model using the Analytic Hierarchy Process (AHP) for circular proposal selection in building projects based on a previously validated conceptual framework. The model involves twelve circularity indicators (CIs) classed under five themes relevant to building lifecycle stages. A questionnaire survey was used to establish the final weight vector of CIs. Participants acknowledged the immediate and prolonged effects of design on circularity and viewed waste as ‘design flaws’ but focused on aspirational design indicators relevant to achieving future circularity and missed opportunities for embedding circular materials in design. Moreover, UK participants showed distinctive behaviours towards CAs (proactive/reactive) based on work experience. ‘UK-Experts’ focused on ‘front-end’ design indicators, while ‘UK-Non-experts’ focused on ‘back-end’ waste management indicators. The findings indicate a partial transition to CE better described as a ‘recycle/reuse economy’. CAs and multiple-criteria decision-making (MCDM) techniques facilitate automated decision-making, which provides a new pathway to digital transformation within built environment. Future research will develop a decision-making tool and apply the proposed model in real-life projects.

Legislative, Institutional, Industrial and Governmental Involvement in Circular Economy in Central Asia: A Systematic Review

As the world faces the detrimental effects of humanity on the environment, the circular economy has started receiving a lot of attention as a tool to keep the value of resources. Although in Europe, circular economy principles have become a trend much earlier, CACs still face challenges in adopting them. The current research aims to review the available literature on sustainability, green economy, and circularity development through the adoption of political, industrial, and financial instruments, followed by an assessment of the barriers and opportunities to circular economy development in the CACs. The novelty of this research lies in the systematic review of different state-of-the-art data resources (journal papers, policies, news, and reports) of CACs by different categories: policy regulations, energy, waste, education, water, and agriculture. This research addresses that the CACs have similar circular economy development barriers (e.g., wide use of fossil fuels, water shortage, and lack of effective waste management) and opportunities (e.g., orientation towards sustainable development, foreign cooperation, and green financing). Therefore, performing effective strategic plans that are already directed to circularity, ensuring stakeholders’ involvement, and providing sufficient funding could benefit their circular economy development.

Effects of Concrete Grades and Column Spacings on the Optimal Design of Reinforced Concrete Buildings

This paper investigates the effects of concrete grades and column spacings on the optimal design of reinforced concrete (RC) buildings. To this end, cost design optimization was performed for buildings with three different floor systems: flat plates (FS), flat slabs with drop panels (FSDP), and solid slabs (SS). The evolutionary method provided by the Excel solver was used as the optimization algorithm because it can deal with the complex nature of structural design problems. The objective function was the total construction cost of the building, including the costs of concrete, reinforcement bars, labor, and formwork, while still fulfilling the constraints of the Egyptian code of practice (ECP-18). The applicability of the presented algorithm was investigated in a design example, where the tuning of the evolutionary algorithm control parameters was sought, and the best parameters were investigated. Two case studies were employed to study the impacts of changing the column spacing and concrete grades on the optimal cost for each floor system. The results showed that low concrete grades, (i.e., characteristic strength up to 40 MPa) and column spacings up to 5 m are preferred in terms of direct construction costs for low-rise RC residential buildings.

Spatiotemporal Model to Quantify Stocks of Metal Cladding Products for a Prospective Circular Economy

The traditional linear economy (LE) approach based on a “take-make-dispose” plan that has been used in building activities over a long period has a significant impact on the environment. In the LE approach, the used materials are usually sent to landfills rather than recycled, resulting in resource depletion and excessive carbon emissions. A circular economy (CE) is expected to solve these environmental problems by promoting material “closed-loop systems”. This study was intended to quantify and analyse the global warming potential (GWP) values of specific metal roofing and cladding products to promote CE thinking. A spatiotemporal model integrated with the life cycle assessment (LCA) tool was used to quantify the GWP value of the steel products in the investigated buildings. The study analysed ten case buildings located in six different cities in New Zealand: Auckland, Wellington, Hamilton, Palmerston North, Tauranga, and Christchurch. The production stages (A1–A3), water processing (C3), disposal (C4), and recycle, reuse, and recovery stages (D) were the focus of the study in analysing the GWP values of the product’s life cycle. The study found that the production stages became the most significant emitters (approximately 99.67%) of the investigated steel products’ GWP values compared to other selected life cycle stages. However, when considering the recycling stages of the steel products, the GWP value was reduced up to 32%. Therefore, by implementing the recycling process, the amount of GWP can be reduced, consequently limiting the building activities’ environmental impacts. In addition, the integration of spatial analysis and LCA was found to have potential use and benefit in future urban mining and the development of the CE approach in the construction industry.