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

Costa Rica, as many countries, are implementing the use of polymer-modified asphalts for road construction, the growing market offers several types of polymers that improve the rheological properties of asphalts, significantly. The most common polymers are SBR, SBS, tire rubber in powder, EMA and EVA among others. The modifiers percentages are between 1% to 5 % m/m of the asphalt binder. However, little research has been conducted for quantifying the amount of polymer incorporated into the asphalt binder. Accordingly, the methods to determine qualitatively or quantitatively the presence of polymers present in the asphalt are the objective of this. This article is aimed to asphalt binder’s laboratories, mainly, but also to engineers and professionals working on road construction and Quality Assurance.

The crack resistance should be an issue to take into account in the performance of the asphalt mixture, which has to resist permanent deformation, fatigue and moisture damage. Cracks appear in flexible pavements through two failure mechanisms: reflective cracking and fatigue. The reflective cracking is a type of failure that has received less attention than fatigue cracking. This form of distress should be consider when selecting the asphalt mixture as overlay, to be placed on rigid pavements stabilized bases or simply when the existing layer is very cracked. It is well known that existing cracks propagate to the top layer causing the water to infiltrate causing the rapid deterioration of the pavement structure. This article focuses on the implementation of the overlay test, which is a very practical method which gives enough information about the characteristic cracking of asphalt mixtures, from the beginning of the crack until its propagation behavior, it´s also sensitive enough to measure the changes in the type and asphalt content to discriminate between various types of asphalt mixtures.

The objective of this research is to evaluate the relationship between the type of capping of cylindrical concrete specimens and their respective final value of compressive strength, so that to determine compliance by the method used . We studied three possible methods for making the faces of the cylinder, the first involves placing a mixture of gypsum-cement hardened specimens, the second is to place a mixture of Portland cement made with fresh specimens and the latter refers to the preparation of hardened faces of the specimens by the respective polishing. As a main point of comparison have cylinders with polished faces, considered the most representative, since the failure load is applied directly to the specimen, then analyzed the results of compression of the other elements. As a final result of the research, there is not a significant difference in the value of unconfined compressive strength, therefore the three methods for preparing the faces of the cylinder are acceptable.

This paper describes the basic design of a low-cost boundary layer wind tunnel specially conceived to be much shorter than conventional environmental wind tunnels while allowing for real-time adjustment of vortex size and speed without needing to alter mean flow speed or affecting fan performance. Potential applications include medium scale modeling of atmospheric wind as it interacts with large urban areas, soil erosion, sediment transportation, and large-area pollution dispersion. Also, calibration of some numerical models of two dimensional low-speed fluid flow may be accomplished with adequate instrumentation.

This study shows the validation process for the determination of total trace concentration of lead (Pb), chromium (Cr) and mercury (Hg) in cement matrix using analytical techniques FAAS, GFAAS and CVAAS. The proposed digestion method consisted in a multistage microwave digestion, which showed the capability to dissolve all the sample (0,5 g) in 3,5 h without the presence of particles or remain solid. The linearity of the methods FAAS, GFAAS and CVAAS were corroborated using ordinary least square model (OLS) and using a graphical interpretation of the residuals from the calibration curve. The homoscedasticity of the variance was demonstrated using the Bartlett test. The results show a good agreement and excellent results in terms of linearity of the methods. The sensitivity of the calibration curves remained invariant over the time. The methods showed a small increase of the repeatability and intermediate repeatability comparing with the obtained for aqueous matrix. However, the repeatability components are less than 4 % and 6 %, respectively. The results also showed how the matrix effect, as a source of error in the determination of Cr and Pb by FAAS, was reduced using deuterium lamp as a background correction. The recoveries obtained for FAAS methods were 106.5 % for Pb and 90.5 % for Cr. The Pb and Hg were measured using GFAAS and CVAAS. These methods obtainded a 100% of recovery of the element tested. The LOD obtained in this validation show reach levels of 0.016 mg kg-1 for Cr (FAAS), 0.064 mg kg-1 for Pb (AAS), 8.72 μg kg-1 for Pb (GFAAS) and 0.43 μg kg-1 for Hg (CVAAS). Finally, the uncertainty of these methods had a low impact in the measurement, having in relative terms a level of 3.95 %, 2.28 % y 13.27 % for Pb, Cr and Hg, respectively. It is concluded that these methods show a good performance to measure metals, specifically Pb, Cr and Hg in the cement matrix, if some factors such as proper digestion of the samples and systematic effects correction will be consider.

The expansion of the accelerated test in mortar bars test immersed for 14 days in an aggressive solution (IRAM 1674) as well as the kinetic analysis according to RILEM AAR-2 recommendations for the study of the potencial deleterious of the aggregate in the alkali-silica reaction are presented in this work. The main objective is to contribute to the interpretation of the test results based on the analysis of the growth in expansion with the time of immersion (kinetic analysis) and in this way, get more reliability. The kinetic analysis consists in adjusting by least squares fit of the experimental data of expansion to a known mathematical model (model KAMJ), where the parameters lnk and M are obtained from. The kinetic parameters lnk and M are associated with the behavior of the reaction. Although a limit value for lnk of -6 is proposed in the literature (lower values are non-reactive aggregates and higher values are deleterious aggregate), from the analysis of the experimental data it was observed that low values of this parameter could be associated with not asymptotic growth of expansion and, therefore, the aggregates presents a deleterious behavior. The lnk/M coefficient is considered a good indicator to evaluate the behavior of the aggregate. However, in order to define a limit value for lnk/M coefficient, it is necessary to establish a correlation with the tests on long-term concrete prism (1 year or more) or the field experience of the aggregate behavior.

In Costa Rica, the prefabricated system of columns and horizontal tiles is one of the most used options in social housing projects developed by the BAHNVI. The BAHNVI is the mortgage housing bank of Costa Rica, it is in charge of assigning housing credits financed by the Government of Costa Rica to vulnerable sectors of the population in order to fulfill their housing needs. As a direct consequence, the supply of this product has increased considerably in recent years by small and medium-sized companies distributed throughout the national territory. As a way to ensure the good quality of these products the Technical Standards Institute of Costa Rica, INTECO, has developed a standard for prefabricated concrete elements for the construction of single-family housing using the system of columns and horizontal tiles. The first edition of this standard was published in 2013 and in February 2017 the second edition was published. This last edition exposes changes in normative aspects, experimental methods and sampling methods. Since the publication of the first edition of the standard, there has been a significant increase in the quality of the verification of this products and a great develop in research work on the subject. This paper describes the main national researches developed in the field and its relation with the evolution of technical regulations.

Bridge Weigh-In-Motion (BWIM) systems have been used successfully to identify some of the properties of the trucks that travel over a highway. However, is not always easy to control the sources of uncertainty and therefore the reliability of the results might be affected. In this research, the effect of possible experimental difficulties on the BWIM method based on strain measurements was studied. In particular, three effects were analyzed: the noise level present on the signal, the location of the sensors on the bridge and the sampling rate used for data acquisition. These effects were modeled numerically by adding synthetic noise to an idealized wave response. The results are discussed with focus on the possible consequences on the estimation of velocities and gross vehicle weight of truck during field tests.

The Technical Standards Institute of Costa Rica (INTECO) was created in 1987 in response to a Costa Rican need for technical standardization. INTECO has greatly evolved over the years developing a very wide range of regulations with around 30 technical committees and more than 500 published standards. Within these committees is the "CTN 04 bituminous mixtures and asphalts binders” which belongs to the category of Asphalt Mixtures, developed in 2004 thanks to the efforts of LanammeUCR. This document includes a summary of each INTECO standard related to asphalt mixes, with illustrative images of equipment and professional LanammeUCR recommendations to ensure the correct application of these processes. This summary also includes three comparative tables wth the most important differences present in: equipment, procedures and precision and bias between the latest AASHTO and ASTM bituminous mixtures standards and their equivalent to INTECO standard. These methods have not being updated in Costa Rica in more than seven years, so the former members of the technical committee as well as anyone in the field are invited to be part of a new team to not only update these rules but also create new ones.

The Technical Standards Institute of Costa Rica (INTECO) was created in 1987 in response to a Costa Rican need for technical standardization. INTECO has greatly evolved over the years developing a very wide range of regulations with around 30 technical committees and more than 500 published standards. Within these committees is the "CTN 04 Bituminous Mixtures and Asphalts Binders” which belongs to the category of Asphalt Mixtures, developed in 2004 thanks to the efforts of LanammeUCR. This document includes a summary of each INTECO standard related to Asphalt Mixes, with illustrative images of equipment and recommendations by professionals of LanammeUCR to ensure the correct application of these processes. This summary also includes three comparative tables with the most important differences of equipment, procedures and precision and bias between the latest AASHTO and ASTM bituminous mixtures standards and their equivalent to INTECO standard. These methods have not being updated in Costa Rica in more than seven years, so the former members of the technical committee as well as anyone in the field are invited to be part of a new team to not only update these rules but also create new ones.