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• Recycled concretes were produced in the laboratory and in the concrete plant. • Physico-mechanical properties of the recycled concretes are analyzed and compared. • Placement of recycled concrete in situ is described. • Cost analysis of recycled concretes was performed. • Environmental impact categories of recycled aggregate were obtained. This research combines technical, economic and environmental analysis of the use of recycled aggregates from construction and demolition wastes in concrete production. Firstly, an experimental campaign to evaluate the effect of recycled aggregate on mechanical properties was developed. The mixture designs studied were: a reference concrete (without recycled aggregate), two concretes with 20% and 100% replacement of coarse natural aggregate by recycled concrete aggregate; and three concretes with 20, 50 and 100% replacement of coarse natural aggregate by mixed recycled aggregate. To analyze their technical feasibility, these concretes were made in the laboratory and in a concrete plant. The economic viability was also studied indicating the additional costs incurred due to the utilization of recycled aggregate in different economic scenarios. Finally, the differences in environmental impacts were analyzed for each concrete. For this purpose, energy consumption, global warming, eutrophication, acidification, photochemical ozone creation, waste generation, and abiotic depletion were accounted. 20% replacement of recycled concrete aggregates does not cause practically variations in the cost or the environmental loads, only a reduction of waste generation and abiotic depletion of 8% and 10.6% respectively. In contrast, the use of 100% replacement by mixed aggregates may increase the global warming indicator an 11% when double transport distance is assumed. But in exchange, the waste generation decreases 35% and the abiotic depletion 50%. Aggregate transport distance is a key factor that will determine the cost, energy consumption, and global warming of the mixed recycled aggregate. [ABSTRACT FROM AUTHOR]

This article describes a study on the viability of using waste from the paper industry: biomass boiler ash and green liquor dregs to fabricate mortars and concretes. Both types of ash were characterized by obtaining their chemical and mineralogical composition, their organic matter content, granulometry, adsorption and other common tests for construction materials. Seven different mortars were fabricated, one for reference made up of cement, sand, and water, three in which 10, 20, or 30% of the cement was replaced by biomass ash, and three others in which 10, 20, or 30% of the cement was replaced with dregs. Test specimens were fabricated with these mortars to conduct flexural and compression tests. Flexural strength is reduced for all the mortars studied. Compressive strength increases for the mortars fabricated with biomass ash and decreases for the mortar with dregs. Finally, 5 concretes were made, one of them as a reference (neither biomass ash nor dregs added), two of them with replacements of 10 and 20% of biomass ash instead of cement and another two with replacements of 10 and 20% of dregs instead of cement. The compressive and tensile splitting strength increase when a 10% of ash is replaced and decrease in all the other cases. The modulus of elasticity always decreases. [ABSTRACT FROM AUTHOR]

This research aims to study the influence of biomass ashes in the evolution of E-Modulus at an early age (0–7 days) in concretes with different percentages of replacement of cement by biomass ash (0%, 15% and 30%). Its behaviour was evaluated through the continuous monitoring of the E-Modulus method as well as using a NDT: measurement of internal electrical conductivity. Whereas at 7 days the influence of a replacement of 15% of biomass ash on E-Modulus is negligible, during the first day the negative influence is very important, with values of loss of E-Modulus higher than 70%. The influence of the biomass ash in the evolution of internal electrical conductivity suggests that the biomass ash could reduce the chloride ion penetration resistance, even in concrete with 15% of biomass ash that did not induce a decrease of the E-Modulus at 7 days. The influence of the biomass ash in the correlations of E-Modulus and electrical conductivity has been studied. Maturity corrections were made. [ABSTRACT FROM AUTHOR]

This research studies the influence of temperature on the evolution of compressive strength and on its correlations with the ultrasonic pulse velocity in concretes and eco-concretes, with a focus on the ages between 1 and 28 days. To that end, 9 concrete mixtures are studied, with parametric variations in the following components: (i) the type of aggregate, including several replacement ratios of recycled aggregate; (ii) water/cement ratio; (iii) cement content, as well as its partial replacement with biomass ashes. These 9 mixtures can be further divided in two major groups: 6 vibrated concretes and 3 self-compacting concretes. The 6 mixtures of vibrated concretes are: a mixture of reference, three mixtures with partial replacement of fine and coarse recycled concrete aggregates (8%, 20% and 31% replacement), and two mixtures with partial replacement of cement with biomass ashes from the paper industry (15% and 30% replacement). The 3 remaining mixtures corresponding to self-compacting concretes are: one reference mixture of self-compacting concrete and two additional mixtures with partial replacement of fine and coarse recycled concrete aggregates from precast elements (20% and 50% replacement). The influence of temperature on the evolution of strength in each of the mixtures is determined for curing temperatures of 5 °C, 20 °C and 45 °C. The study further includes the evaluation of the influence that temperature and mixture parameters (particularly those of eco-concretes) have on the relationship between compressive strength and ultrasonic pulse velocity. [ABSTRACT FROM AUTHOR]