Browsing by Author "Paul, Alvaro"

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    Assessing Lightweight Aggregate Efficiency for Maximizing Internal Curing Performance
    (AMER CONCRETE INST, 2011) Paul, Alvaro; Lopez, Mauricio
    Internal curing (IC), which has been extensively investigated in the last decade, has been shown to enhance hydration, diminish autogenous shrinkage, and mitigate early-age cracking due to self-desiccation in high-performance concrete. It also increases the internal porosity of concrete, however, which might reduce mechanical properties. Thus, a better understanding of what makes a lightweight aggregate (LWA) effective and efficient for IC is fundamental to maximize the gains and minimize the shortcomings.
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    Concrete Containing Natural Pozzolans: New Challenges for Internal Curing
    (ASCE-AMER SOC CIVIL ENGINEERS, 2012) Espinoza Hijazin, Gaston; Paul, Alvaro; Lopez, Mauricio
    Natural pozzolans (NP) have proven to be an effective supplementary cementitious material; however, the replacement of ordinary portland cement (OPC) with NP might increase the autogenous and drying shrinkage of concrete. Internal curing (IC) might be of great help when using NP because it can promote the pozzolanic reactions and reduce shrinkage. The aim of this research is to assess the effect of IC in concrete containing NP. Results indicate that a 39% replacement of OPC with NP decreased compressive strength by 15%, decreased chloride ion permeability by 66%, and increased autogenous shrinkage by 40%. IC with prewetted lightweight aggregate showed no significant effect in compressive strength or permeability, but it decreased autogenous shrinkage by up to 58%. NP used in this investigation presented higher chemical shrinkage than OPC, making IC less effective as levels of NP increased. The important decrease in permeability attained through the use of NP and the higher chemical shrinkage of NP makes IC a critical technology to consider in concrete mixtures with NP. DOI: 10.1061/(ASCE)MT.1943-5533.0000421. (C) 2012 American Society of Civil Engineers.
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    On the effect of simulated contamination of chlorides and sulfates on steel rebar corrosion: Electrochemical behavior and surface analysis
    (2022) Melo, Paula; Echague, Matias; Guerra, Carolina; Jin, Qingxu; Sancy, Mamie; Paul, Alvaro
    To understand the effect of sulfate ions on the chloride-induced corrosion of reinforced concrete, this study focuses on the electrochemical behavior and surface analysis of standarded carbon steel that was exposed to simulated pore solutions, with different combinations of high and low chloride and sulfate concentrations. Linear scanning voltammetry and electrochemical impedance spectroscopy were used to monitor the corrosion reaction. Steel surface was characterized by X-ray photoelectron spectroscopy and field emission scanning electron mi-croscopy. Results indicate that the presence of sulfate affects the electrochemical behavior of steel corrosion at a low and high chloride concentration, where the capability of the corrosion protective layer was influenced by the increase of the sulfate and chloride content. Calcium carbonate deposits were observed at the surface of corroded samples, where higher precipitation of calcium carbonate crystals on carbon steel surface is associated with higher rates of localized corrosion.
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    The Emergence of a More Conventional Reading of the Conventionality Control Doctrine
    (2019) Paul, Alvaro
    The Inter-American Court of Human Rights developed a doctrine called conventionality control. In general terms, this doctrine is somewhat similar to the idea of judicial review of legislation, but applied in a transnational forum. According to the Court, conventionality control would require domestic judges and other bodies of States parties to the American Convention on Human Rights (ACHR) to depart from domestic legislation that runs counter to the ACHR or the Inter-American Court's interpretation of the ACHR. Many scholars contend that the application of this doctrine should be carried out even if the domestic bodies that apply it have no constitutional power to do so. Others have a more restrictive interpretation and consider that domestic bodies would have to apply it to the extent of their power, according to their national constitutions. Apparently, the latter interpretation is gaining a wider support, which is desirable, because only this reading would be compatible with the principles of international law, and possibly accepted by all member States.