Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Recently the ASTM D6637 test method of the American Association of Materials Testing (ASTM) was implemented in the National Laboratory of Materials and Structural Models of the University of Costa Rica (LANAMME UCR). In the verification stage of the correct implementation of the test method, we worked with 2 types of geogrids samples used as reinforcement at the national level; which were tested to determine their tensile mechanical properties; ie (ultimate strength and ultimate deformation). Once these characteristics were obtained, we proceeded to compare them with the data reported in their technical specifications. In this stage, inconsistencies were found between the data found at the laboratory level and those reported by the manufacturer; which gave indications of possible overvaluations in the data reported by the manufacturers and marketers of geogrids. There is also evidence of data reports in values ​​different to the MARV specification, which is the one adopted by ASTM in the subject of quality control. This document is derived from the final work of graduation: "Implementation of the test methods for the determination of the properties at the same time in the geogrids and geotextiles according to the ASTM D6637 and ASTM D4595 standards" (see bibliographical reference 6).

In Costa Rica, the most widely used standard in terms of specifications to assess the quality of aggregates for hydraulic concrete corresponds to that of the American Society for Testing and Materials (ASTM), which constitutes the basis for of the standards of the Institute of Technical Standards of Costa Rica (INTECO). Therefore, the graduation requirements of the aggregates that are followed in the country come from the ASTM C33 standard Specification for aggregates for concrete (INTE C15:2014). For mix design, this standard provides grading specifications for nominal maximum sizes of 90 mm, 63 mm, 50 mm, 37,5 mm, 25 mm, 19 mm, 12,7mm and 9,5 mm. However, in recent studies, Hernández (2018) and Delgado (2018), used an aggregate with a nominal maximum size of 16 mm in the production of hydraulic concrete to obtain standard resistance development curves for different types of portland cement that are marketed in the country. In their work, both Hernández and Delgado used coarse river aggregate and coarse pit aggregate. For each case, the specifications for maximum nominal sizes of 12,7 mm and 19 mm provided by the ASTM C33 (INTE C15:2014) standard were used as granulometric reference, since in this standard there are no specifications for aggregate of 16 mm. Aggregate-producing sources at the national level are generating a significant amount of 16 mm aggregate, so it was interesting to carry out an experimental study with statistically valid samples, which allow verifying with an adequate degree of certainty the validity of using the granulometry that best will fit (nominal maximum size: 12,7mm or 19 mm) when using 16 mm aggregate. But also, as part of the study, a proposal for granulometric limits was generated for a size of 16 mm. 

The objective of the research was to carry out a repeatability and reproducibility study in representative samples of small wooden specimens from Spathodea campanulata, Fraxinus americana and Albizia Plurijuga. The experimental strategy assumes two stages. The first consisted of the analysis of the results of the frequencies measured in the three angiosperm species. Its objective was to validate the homogeneity and representativeness of the woods under study. The second stage was oriented to the study of the variations of the frequency results. Its objective was to build repeatability and reproducibility tables and their analysis of variance. A completely randomized and balanced design was prepared. The experimental unit consisted of three homogeneous groups of 40 test tubes of each species. For each species studied, crossover repeatability and reproducibility studies were carried out. The results indicate that for S. campanulata, 97.7% of the total variance is due to the instrument while 2.3% to differences between operators; for F. americana, 99.2% of the total variance is due to the instrument and 0.8% to differences between operators, while for A. plurijuga, 100% of the total variance is due to the instrument while there is no variability due to differences between operators.

This research aims to determine the effects of the use of curing products in hydraulic concrete through laboratory conditions. Although research and technical specifications of curing products indicate improvements in concrete curing, their use and possible advantages must be experimentally verified for the conditions and types of concrete manufactured in Costa Rica. Three types of curing products are used, the first corresponds to a transparent silicate-based curing product that does not produce membrane (C1), the second is a resin-based membrane-forming curing product (C2) and the third is a product Colloidal solution based film-forming curing agent (C3). Through laboratory tests, the compressive strength, modulus of rupture and change in length (expansion or contraction) of concrete are determined for different curing conditions. In general, the results indicate that curing products, at any age of application, do not reduce the expansion or contraction of concrete. For curatives to be adequately effective in developing resistance to shrinkage and flexure in concrete, it must be cured with water for a minimum of three days prior to application of the product. The results suggest better results when applying the curing product 7 days after keeping the specimens in the wet room. 

In this project, the feasibility of laminated wood beams as a sustainable construction option in comparison to traditional materials is presented. To do this, an evaluation index was developed, wich takes into account the information of content, distance, process, modulation and maintenance of each material; providing a simplified and preliminary result of the sustainability of the materials for decision making in projects. Additionally the laminated beam, solid wood beam, concrete beam and steel beam were evaluated. Confirming that wood is a more environmentally friendly material, wheter presented as a solid wood beam or laminated beam.

The demands for construction materials are increasing, their sources are scarce and the management of construction and demolition waste is very complex. The research that supported this article sought to study the characteristics of coarse aggregate for construction from civil works waste, and compare them with traditional virgin aggregates, in order to assess their possible use. We worked with three sources of raw material for recycling: masonry walls, precast tiles, and cast-in-place concrete (test cylinders); all facilitated by the LanammeUCR. The standards established by INTECO were followed, both for the characterization of the recycled aggregates and for the mix designs. Three different percentages of recycled coarse aggregate were used in the mixtures, substituting the natural one. The results showed small variations regarding the behavior of the virgin aggregate, especially in absorption, unit weight and wear. Very favorable results were obtained in terms of the compressive strength of the concretes with recycled coarse aggregate, always contemplating a mix design that adjusted to its characteristics. Among the limitations is that the durability of manufactured concrete was not studied; recycled fine aggregate was not used either. Both phenomena will be addressed in future research. At the end of the investigation, it is concluded that the recycling of coarse aggregate is technically feasible.

Due to the scarcity and high transportation costs of stone aggregates in the east and northeast of Bolivia, different alternatives have been sought for their partial or complete replacement in the construction industry and, specifically, to produce concrete. The objective of this research is to evaluate the workability, compressive strength, and ultrasonic pulse velocity (UPV) of concrete produced entirely with coarse lateritic aggregates and a commercial superplasticizer additive. Using the IPT/EPUSP method, concrete with coarse lateritic aggregate was dosed for 30 MPa (design compressive strength). Five different percentages of additive (by weight of cement) were considered: 0% (reference), 0.6, 0.8, 1 and 1.2%. Although the superplasticizer additive improves workability at higher percentages, the mixtures with 0.6, 0.8 and 1% presented higher compressive strength and VPU, when compared to the reference (0%). 1.2% of additive presented the lowest values ​​of compressive strength and VPU. The use of additives, in this case superplasticizer, is beneficial for the workability and compressive strength of lateritic concrete, but the most appropriate content for its use must be defined.

In this investigation, the performance and cost of workforce, material, and equipment in the application of plaster with industrialized mortar were estimated. The measurements were made in three housing projects of one and two levels, located within Alajuela, Heredia, San José or Cartago, Costa Rica. In the first two, mortars of different brands were used, however, the application methodology was manual in both cases. In the third project the same mortar was used as one of the previous projects, but it was applied mechanically. For the data analysis obtained, the statistical student-t test was used, with a reliability of 90%. It should be noted that the results are valid only for projects with characteristics like the ones used in this study. According to the results, the cost of the plastering applied manually is very similar to the one applied with a sprayer machine, since the savings in workforce cost is approximately equivalent to the amount necessary to amortize the equipment and the additional cost of the projectable material.

This paper presents the modal parameters of a 17,5 m high building, due to environmental vibrations, obtained using methods in the frequency and time domain available in the ARTeMIS Modal v.5.0 software, with the aim to evaluate its efficiency to conduct Operational Modal Analysis using data of ambient vibration tests in buildings. In the measurement, the roving sensors technique was used for a total of six test setups, with four TitanSMA triaxial accelerographs. The processing was carried out using the softwares: Geopsy and ARTeMIS Modal, with which no difference was found, and in the analysis five vibration modes were identified through spectral analysis, while the results in the time domain were inconsistent. In addition, the Modal Assurance Criterion (MAC) was used for a cross control between the modal shapes obtained with the two different domains (time and frequency).

In emerging economies, the implementation of Transportation Infrastructure Management is a prevailing need. In order to use limited available resources in the most efficient way, technology emerges as a strategic ally. For the purpose of pavement and bridge preservation, different methodologies have been developed for the detection of overweight vehicles. This article presents the implementation and validation of Bridge Weigh-In-Motion (BWIM) located in Costa Rica through the instrumentation of an in-service highway bridge with minimal instrumentation requirements. The approach used was based on the concept of influence area from strain response time histories. Given the location of the sensors near the bridge abutment to reduce installation requirements, two types of strain responses were analyzed based on horizontal strain and shear strain in order to define quantity and location of sensors for possible implementations. Two calibration trucks were used as reference for calibration and the weight from over 90 trucks were estimated and compared to static measurements from a nearby permanent static weigh station.