No abstract

In developing countries, construction and demolition waste (CDW) is disposed to landfill, causing social, environmental, and economic crises. In these nations, CDW exponentially increase due to their rapid economic growth, industrialization, and urbanization. This paper aims to examine the possibility of recycling concrete waste for production of new concrete in Ethiopia. Physical and mechanical characteristics of recycled concrete aggregate (RCA) acquired from concrete waste are thoroughly examined. Though the RCA exhibited relatively lesser performance compared with the natural coarse aggregate (NCA), it reveals the same properties as of normal-weight aggregates in several instances. The performance of concrete specimens which employ RCA up to 20% is evaluated from workability, strength, and permeability aspects. The utilization of RCA slightly affects the workability and the water permeability properties of the concretes. Replacement of 10% of the NCA by the RCA enhances the compressive strength of the hardened concrete by 8%. The difference between the splitting tensile strength of the concretes which employ RCA and conventional aggregates is trivial. Generally, this work demonstrates the practicability of concrete waste recycling to produce new concrete or construction materials in Ethiopian context.

No abstract

Buildings use a wide range of construction materials, and the manufacturing of each material consumes energy and emits CO2. Several studies have already been conducted to evaluate the embodied energy and the related CO2 emissions of building materials, which are mainly based on case studies from developed countries. There is a considerable gap in cases of developing countries regarding assessment of embodied energy and CO2 emissions of these building materials. This study identified the top five most used construction materials (cement, sand, coarse aggregates, hollow concrete blocks, and reinforcement bars), which are also prime sources of waste generation during construction in the Ethiopian building construction sector. Then, what followed was the evaluation of the embodied energies and CO2 emissions of these materials by examining five commercial and public buildings within the cradle-to-site lifecycle boundary. The evaluation results demonstrated that cement, hollow concrete blocks (HCB), and reinforcement bars (rebars) are the major consumers of energy and major CO2 emitters. Cumulatively, they were responsible for 94% of the embodied energy and 98% of the CO2 emissions. The waste part of the construction materials has inflated the embodied energy and the subsequent CO2 emissions considerably. The study also recommended several strategies for the reduction of embodied energy and the related CO2 emissions. The research delivers critical insights into embodied energy and CO2 emissions of the five most used building materials in the Ethiopian construction industry, as there are no prior studies on this theme. This might be a cause to arouse awareness and interest among the policy makers and the wider public to clearly understand the importance of research on this crucial issue to develop national energy and CO2 descriptors for construction materials, in order to take care of our naturally endowed, but yet fragile, human habitat.

No abstract