International Concrete Abstracts Portal

Portland cement concrete has shown great potential for recycling different waste materials. Solid waste incorporated concrete (SWC) is considered to have positive environmental advantages. However, the utilization of solid wastes may negatively impact the mechanical performance and durability of concrete. Therefore, any change in the performance metrics of SWC should be accounted for in the comparative life cycle assessment (LCA). This article will review the functional equivalency with respect to the mechanical performance and durability metrics for SWC incorporating four main streams of solid wastes; recycled concrete aggregate, municipal solid waste incineration ashes, scrap tire rubber, and polyethylene terephthalate. It will be shown that while in most cases, SWC may have an inferior compressive strength and/or durability pre-treatment, sorting, and appropriate replacement rate of the solid wastes may solve the problem and make SWC functionally equal to the conventional concrete. Moreover, some types of SWC such as those incorporating scrap tire rubber and polyethylene terephthalate may be more advantageous if used in specific applications where dynamic loads are prevalent given their superior impact resistance. Finally, the article will discuss new insights into defining the functional unit based on the performance and application of SWC to conduct a reliable LCA.

To support a rapid integration of sustainability principles into paving concrete practice, this study provides a closer look into readily implementable cement and concrete decarbonization strategies. To do so, this study relies on combined stakeholder involvement, quantitative analysis using Life Cycle Assessment (LCA), and the state-of-the-practice in the US paving concrete industry to understand merits of each solution. The results indicate that concrete mix design optimization is a promising, yet not widely applied solution that can reduce costs, enhance durability, and provide average carbon emissions savings of 14 percent. Use of supplementary cementitious materials (SCM) is another solution with multiple benefits, however, the use of SCM is already widely implemented across the USA. Industry-wide improvement in cement carbon footprint due to energy efficiency can provide additional savings of up to 10 percent. Quantifying the environmental footprint of concrete is critical to inform decision-making and enable more sustainable outcomes.

Concrete is the substance most consumed by humanity after water. Blended cements in which part of the energy intensive clinker is replaced by supplementary cementitious materials (SCMs) are the by far the most realistic means to obtain large scale CO2 reductions in the short-to-midterm, attending the urgency of the climate emergency. LC3, blended cement produced by the combination of limestone, calcined clays and Portland cement provides a solution that achieves equivalent mechanical performance to OPC, better durability against chloride penetration and ASR and a reduction of CO2 emissions by about 40%. Due to the similarities of LC3 with OPC, it is a material that can be adopted today using the same construction equipment and workforce worldwide.

This research studies the use of a fractional coarse aggregate replacement product (PA). PA is a unique blend comprised of recycled plastics, glass, and minerals; all collected from the waste stream. The use of PA and other similar products may contribute to reducing plastic waste in the waste stream. To test the feasibility of PA as a partial, natural aggregate replacement, four different mixtures of concrete were batched and tested. The concrete mixtures were based on the standard commercial interior normal-weight concrete mixture. This is a non-air-entrained mixture, provided by a local concrete batching plant (MCM), with a design strength of 4000 psi (27.6 MPa). The four concrete mixtures tested were a control mixture with no variations to the original mixture design as well as three mixtures with 15%, 30%, and 45% coarse aggregate replacement by volume. The compression strength, tensile splitting strength, modulus of rupture, and density of the concrete are examined. The focus of the paper is the concrete compressive strength because it is the primary determining factor in concrete design. Fresh concrete properties and hardened concrete properties were examined and recorded. Slight changes to the overall fresh concrete properties of workability, density, and slump were recorded. The hardened concrete properties include compression, tensile splitting, and modulus of rupture. The results of the compression tests show a strength proportionally decreased with the percent increase in PA replacement – 15% replacement with an 18.1% decrease, 30% replacement with a 35.6% decrease, and a 45% replacement indicated a 45.3% decrease at the 28-day test. The results of the tensile splitting tests and modulus of rupture tests both indicate similar results of a decrease in strength as the replacement rate of PA increased.

The present study addresses the effective utilization of tannery sludge as a partial replacement of fly ash in brick manufacturing. The main objective of this research is to determine the optimal sludge content that can be incorporated in flyash bricks and thereby to assess the key engineering properties while mitigating potential radiological emissions. Sludge incorporated bricks were cast with the tannery sludge varying from 5% to 30 %. The bricks were tested for its compressive strength, water absorption, efflorescence and radiological tests. Samples were prepared for radiation test with varying percentage of tannery sludge. Various parameters, including internal and external hazard indices, radium equivalent activity (Req), annual effective dose rates, and absorbed dose rates, were thoroughly examined in this research. The results of various tests revealed that the newly formulated fly ash tannery bricks showed significant compressive strength upto 20% replacement. The water absorption and efflorescence were found to be within permissible limit as per BIS IS 3495. The gamma-ray spectrometry measurements of Primordial radionuclide activity concentrations, including Uranium-238, Thorium-232, and Potassium-K, in sludge bricks were found well within the permissible limits as per UNSCEAR 2000. The radium equivalent activity was found below the permissible limit of 370 Bq/kg. The absorbed gamma dose, radioactivity level index, external hazard index, indoor effective dose rate and outdoor effective dose rate, were all determined to be below the threshold of one (1.0), indicating that they were comfortably within the safety standards recommended. The results claimed the tannery sludge did not pose any serious radiation effect and it can be utilized as an eco-friendly as well as user- friendly construction material.