Álvaro Paúl

Assessing Lightweight Aggregate Efficiency for Maximizing Internal Curing Performance

This paper describes how 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. IC also increases the internal porosity of concrete, 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. This paper analyzes the performance of a wide set of LWAs for IC, including artificial and natural LWAs. The water uptake, water release, and pore structure of the LWAs were determined, as well as their performance in concrete, which was assessed using the degree of hydration, compressive strength, chloride ion permeability, and autogenous shrinkage. The results presented in the paper showed that natural LWAs possess higher, coarser, and more interconnected porosity than artificial LWAs. This allows natural LWAs to store more water and present higher and faster water release for IC. Natural LWAs produced concrete with a similar or better performance than that of artificial LWAs in spite of requiring lower dosages. When selecting an LWA for IC, it is important to consider not only its effectiveness in reducing autogenous shrinkage, but also its efficiency and other performance criteria, such as transport properties and compressive strength.

Concrete Containing Natural Pozzolans: New Challenges for Internal Curing

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.

Admissibilidade de provas perante à Corte Interamericana de Direitos Humanos

The Inter-American Court of Human Rights performs a wide evidentiary analysis, which tends to be very flexible in its admission of evidence. This paper tries to decipher the extent, applicability, and content of the Court’s admissibility rules, both the norms established by the Court itself, and those that the Court is obliged to follow. In order to do so, this article will analyze the relevant case law of the Court and provide some examples. Within this analysis, this article refers in depth to some unclear rulings that the Court has made in relation to the exclusion of evidence obtained via coercion, some of which seem to clash with the central role of truth in the Inter-American system.