Concrete based on recycled aggregates – Recycling and environmental analysis: A case study of paris’ region

Abstract

The use of recycled concrete aggregates as an alternative source of coarse aggregates for the production of new concrete can help to solve the problem of depleting natural resources and that of growing waste disposal crisis. However, their recycling could decrease the concrete performance, particularly for low grade recycled aggregates (RA). To compensate for this decrease, cement content can be adjusted and hence, the environmental interest of RA has to be assessed. This study aims at assessing the environmental footprint of recycled aggregate concrete (RAC), compared to natural aggregate one (NAC), considering the grade of used RA and the aggregates’ delivery distance, at the scale of Paris’ region.From the strength point of view, the use of RA induces a decrease of RAC performance, which is proportional to their content. This decrease can be compensated for by increasing cement content. For 50% of RA dosage, 16% of additional cement is necessary to achieve the compressive strength of NAC, when low-grade-RA are used (RA_1). Recycling high grade RA (RA_2 and RA_3), affects slightly RAC compressive strength and 3% of additional cement are enough to compensate for its decrease. Pre-saturating these RA, reduces by 35% the amount of additional cement.From an environmental point of view, recycled aggregates can be an alternative for natural ones and the environmental footprint of RAC can be limited by using high grade RA. Furthermore, the delivery distance of NA is the key parameter in assessing the environmental impacts of RAC, compared to NAC. Results showed that global warming indicator impact is greater for NAC, compared to RAC with 50% of RA, provided that NA delivery distance exceeds 50km, which is the case in Paris’ region. With 20% of substitution rate, high-grade RA improve all environmental impacts of RAC, except Waste, compared to NAC.