Browsing by Author "Izquierdo, Silvia"

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    Carbonation and chloride penetration performance of self-compacting concrete with masonry and concrete wastes
    (2024) Silva, Yimmy Fernando; Izquierdo, Silvia; Delvasto, Silvio; Araya-Letelier, Gerardo
    In this research, masonry and concrete construction and demolition wastes (CDWs) were used as supplementary cementitious material (25% vol. residue of masonry, RM) and recycled coarse aggregate (RCA) in increasing levels (0%, 50% and 100% vol. residue of concrete), respectively, in the development of self-compacting concrete (SCC). The performance of SCC mixtures was evaluated in terms of fresh properties, compressive strength, resistance to both accelerated (1% CO2, 65% R.H. and 23 degrees C temperature) and natural carbonation as well as chloride penetration. Experimental results showed a monotonic workability reduction associated to the incorporation of increasing levels of RCA. In compressive strength, the SCC with RCA showed the greatest increase in this mechanical property after 28 days of accelerated exposure in the carbonation chamber, when compared to its water-cured counterpart. Yet, at 360 days of accelerated carbonation exposure, all SCCs showed compressive strength reductions compared to their water-cured counterparts. On the other hand, the chloride permeability resistance of the SCCs was low and very low at the ages evaluated. Thus, the findings of this study indicate that the use of CDW can generate SCCs with adequate fresh properties, compressive strength and carbonation and chloride penetration performance, which offers benefits for the environment.
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    Exploring the Potential of Alternative Materials in Concrete Mixtures: Effect of Copper Slag on Mechanical Properties and Carbonation Resistance
    (2023) Silva Urrego, Yimmy Fernando; Villaquirán-Caicedo, Mónica A.; Izquierdo, Silvia
    In this study, the effect on the flowability, compressive strength, absorption, sorptivity, and carbonation resistance of concrete with different copper slag (CS) replacement ratios was investigated. For this research, four concrete mixes with different percentages of CS were made (0%, 10%, 20%, and 30% of CS as replacement of cement by volume). In addition, the microstructure was analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), and thermogravimetric analysis (TG–DTG). The results shows that the incorporation of CS reduces the workability and compressive strength of the mixtures, being more significant in concrete with 30% CS. The carbonation depth of concrete with CS increases monotonically with increasing CS. In addition, the compressive strength of the carbonated (20% and 30% CS) concretes show a loss of compressive strength at 90 days of exposure when compared to their water-cured counterparts. The use of low percentages of CS does not generate a decrease in workability and its mechanical effect is not significant at prolonged ages, so the use of this waste as SCM in percentages close to 10% is a viable alternative to the sustainability of concrete and the management of this residue.
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    Short and long-term physical and mechanical characterization of self-compacting concrete made with masonry and concrete residue
    (2021) Silva Urrego, Yimmy Fernando; Delvasto, Silvio; Izquierdo, Silvia; Araya Letelier, Gerardo Andrés
    This study aims to investigate the fresh and hardened properties of self-compacting concrete (SCC) made with residue of masonry (RM) and concrete waste (CW). The RM was added as supplementary cementitious material (SCM), replacing ordinary Portland cement (OPC), in 25% by volume and the SCC mixtures were designed incorporating five increasing amounts of CW as recycled coarse aggregate (RCA) (0%, 25%, 50%, 75%, and 100%), which were compared with a reference SCC with a 100% OPC and natural coarse aggregate (NCA). Both fresh state (workability, passing ability and viscosity) and hardened state (compressive strength, indirect tensile strength, flexural strength, porosity and capillary suction) properties of SCCs were evaluated, including short and long-term evaluations. The results show that RCA generates a loss in the fluidity, flow rate, passing ability and filling capacity of SCC, presenting the greatest decrease of workability in high percentages (75% and 100%) of RCA. However, all the SCCs managed to be in the required ranges by the EFNARC. In the hardened state, the mechanical properties generally weakened with increasing replacements of RCA, but the reduction rate was minimal when the content of RCA did not exceed 50%, being 1.22% less at 360 days when compared to the reference mixture’s compressive strength. Finally, the presence of RM at long ages generated a positive effect on properties when compared to the reference SCC, which can be used to compensate the moderate strength reductions generated by low-to-medium replacement ratios of RCA leading to sustainable SCCs incorporating both residues (RM and CW) with similar performance than conventional SCCs.