• Energy Research

The building sector’s sustainability requires construction and demolition waste (CDW) to contribute to the circular economy. Among the CDW, recycled concrete aggregates (RA) have been mainly studied to replace natural aggregates. Still, the approval of their use in regulations and standards is slower. Some barriers to the adoption of RA are related to the durability of recycled aggregate concrete (RAC). However, their physical and mechanical properties have been extensively studied. The durability risks associated with sulfate attacks have been solved for conventional concrete. However, sulfate attack on recycled concrete still raises numerous unsolved questions. In this literature review, the experience of sulfate attack on RAC is compiled and analyzed using a compressive framework highlighting the most relevant aspects of the new matrix in RAC and the old matrix of RA to support its relevance to the damaging sulfate process. Suggestions for further research are presented to understand the full extent of this issue and contribute to incorporating and extending recycled aggregates into existing regulations.

Carbon neutrality to limit global warming is an increasing challenge for all industries, particularly for the cement industry, due to the chemical emission of the process. For decades, reducing the clinker factor has been one of the main strategies to reduce the carbon footprint. Additional cuttings in the clinker content of cements seem possible with the upsurge of novel supplementary cementitious materials. This potential contribution represents only a fraction of the required carbon reductions for achieving the goal of carbon neutrality in the coming decades. This paper describes the current situation of the cement industry in Latin America and the Caribbean and the global opportunities and strategies to reduce the carbon footprint of cement and concrete and their adaptation to the regional conditions. Besides describing emerging supplementary cementitious materials, the potential contributions of industrialization and quality control are discussed. Moreover, limitations related to geography and standardization are analyzed. Regional considerations are made given the specific prospects of human development.

Abstract Purpose The construction sector consumes a large quantity of natural resources and generates a great deal of carbon dioxide emissions and wastes, affecting its sustainability. Replacing Portland cement with supplementary cementitious materials (SCM) could reduce the environmental impact. This paper examines the carbon footprint of reinforced concrete columns. It focuses on the influence of increasing the steel cross-section and reducing the clinker factor by replacing Portland cement with SCM. Methods Eighteen concrete mixtures were selected and classified according to the specified compressive strength at 28 days of curing using binary and ternary blended cements. Columns were designed consisting of such concretes and employing different reinforcing steel cross-sections. The Life Cycle Assessment was conducted on ISO 14040 standard. The embodied carbon dioxide (ECO2) of the reinforced concrete columns was determined. Results The results show that the higher the compressive strength of concrete, the lower the carbon footprint of the columns. Concretes with a high volume of SCM replacement and low compressive strength at 28 days do not show the lowest carbon footprint since it requires a greater volume of material to withstand the bearing capacity. The carbon footprint of the columns increases as the steel section increases. Furthermore, increasing the compressive strength of concrete is less beneficial for reducing the carbon footprint of the column when the steel cross-section is increased. Conclusions Portland cement is the component material of concrete that contributes the most to the concrete carbon footprint, and steel has the highest ECO2/ton. Replacing Portland cement with SCM reduces ECO2 at one point of the life cycle and may increase the material volume and ECO2 at another. The lowest carbon footprint of compressed reinforced concrete elements is achieved for the higher-strength concretes and the minimum steel cross-section.