Equivalent CO2 Emission and Cost Analysis of Green Self-Compacting Rubberized Concrete

Abubakar Mohammed,Yasser E. Ibrahim,Hani Alanazi,Musa Adamu,Ifeyinwa I. Obianyo,Sylvia E. Kelechi

doi:10.3390/su14010137

Abstract

Global warming and climate changes are the major environmental challenges globally. With CO2 emission being one of the main greenhouse gases emitted to the environment, and cement and concrete production amounting to about 10% of the global CO2 emission, there is a need for the construction industry to utilize an environmentally sustainable material as an alternative to cement. This study analyzed the cost, CO2 emission and strength properties of green self-compacting concrete (SCC) ternary blend containing fly ash, calcium carbide residue (CCR), and crumb rubber (CR) as a replacement material by volume of cement, cementitious material, and fine aggregate, respectively. Cement was replaced with fly ash at 0% and 40% by volume. CCR was used as a replacement at 5% and 10% by volume of cementitious materials, CR replaced fine aggregate in proportions of 10% and 20% by volume. The result indicated that the mix with 0% fly ash and 20% CR replacement of fine aggregate was the most expensive and had the highest CO2 emission. However, the mix with 10% CR, 40% fly ash, and 10% CCR had the lowest CO2 emission and was therefore the greenest SCC mix. The 28-day maximum compressive strength of 45 MPa was achieved in a mix with 0% CR, 0% fly ash, and 10% CCR, while the utmost 28-day splitting tensile strength of 4.1 MPa was achieved with a mix with 10% CR, 0% fly ash, and 5% CCR, and the highest flexural strength at 28 days was 6.7 MPa and was also obtained in a mix with 0% CR, 0% fly ash, and 5% CCR. In conclusion, a green SCC can be produced by substituting 40% cement with fly ash, 10% fine aggregate with CR, and 10% CCR as a replacement by volume of cementitious material, which is highly affordable and has an acceptable strength as recommended for conventional SCC.

Highlights

100% OPC was used, and crumb rubber (CR) was used as a partial replacement by volume of fine aggregates, and calcium carbide residue (CCR) was used as a partial replacement by volume of cementitious materials
40% cement was replaced with fly ash, CR was used as a partial replacement to fine aggregate, and CCR was used as a partial replacement to cementitious materials
CR increased the initial cost of the green self-compacting concrete ternary blend by 2% when compared to the control mix, and these continued to reduce at greater percentage replacements

Summary

Introduction

Climate change has emerged as a major environmental concern. Environmental sustainability is the major challenge of the construction industry, and several measures have recently been taken to overcome excess CO2 emission and greenhouse gas emissions associated with cement and concrete production. About 30 billion tons of concrete is consumed annually all over the world. The production of one ton of concrete generated about 0.5 to 0.6 tons of CO2. In 2019, the CO2 generated from concrete production reached 72.5 kg CO2 /ton. Compared to forty years ago, the quantity of CO2 generated from concrete production has tripled due to the increase in demand of concrete

Methods

Results

Conclusion