Volume 9Enero - Diciembre 2019

This paper presents a synthesis of the experimental results obtained from testing the evolution of the compressive strength in concrete made with different modified cements at different ages. It includes the characterization of two aggregates of different provenances (river and quarry) and three types of modified cements. The cements tested correspond to MM/C (P-C) -28, MM/C (C-P) -28 and MC/A - AR. The objective of the study was to generate the standard resistance development curves of six concrete mixtures (in percentage terms), using these cements and aggregates. The characterization tests were conducted out following the INTECO and ASTM standards. The curing of concrete specimens took place in a humid chamber at 4 different ages (3, 7, 28 and 56 days). The strength of the concrete was obtained through tests on the Universal Machine, and the results were processed and validated statistically, using the acceptance parameters of the ACI 214-2002 report. From the analysis, it was possible to generate the curves of standard development of resistance for all the cements under study using two provenances of aggregates, including an inferential statistical analysis for the resistance results of the concretes. It was concluded that, by varying the origin of the aggregate for the same cement, the resistance of the concrete is significantly different (on statistical terms), as for the same aggregate when the type of cement is changed.

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).

Chip seals are an alternative to preserve the current condition of a road and to improve some of its characteristics such as impermeability and surface texture. Despite its benefits, there is currently no formally defined test method to evaluate the laboratory performance of chipseals elaborated from different materials or design methodologies. For this reason, in this article, based on a series of modifications made to the ASTM D7000 test, the performance of chipseals developed from the design methodologies adopted by the transportation agencies TxDOT and Austroads is compared. These methodologies start from the two most fundamental lines of thought for the design of asphaltic surface treatments, the Hanson principles, used in the Austroads method and the Kearby principles, used in the TxDOT method. From the tests carried out, it was determined that the Austroads methodology promotes chipseals that would have a greater amount of
remaining aggregate, after simulating the effects of vehicular traffic on the samples of asphaltic surface  treatments prepared, being an aspect that could positively influence their performance.

The quality control of concrete paving blocks in Ecuador has remained unchanged since 1987, using as a criterion of quality and durability the value of the compressive strength of the block under the concept of global indicator. This indicator assumes that when the axial load carrying capacity specification is met, it will cover requirements such as abrasion resistance, therefore the expectations of the paving surface design life. However, in recent years an early deterioration of the paving brick surfaces has been verified in general despite compliance with the axial load carrying capacity requirements established in the Ecuadorian standard. Under these conditions, the University, the construction industry and the Ecuadorian Standardization Institute (INEN) decided to adapt a new control standard in which the indicator of acceptance is broken down into several physical and mechanical parameters, using the European standard EN 1338 as a reference document. Among the parameters, the quantification and assessment of abrasion resistance became of greater interest, both because of the lack of abrasion resistance of most of the production in the country, as well as the test method to be used. The present article, based on a traditional statistical analysis of 516 abrasion resistance tests by means of the wide wheel abrasion test method (EN 1338) performed at the Construction Materials laboratory of the Pontifical Catholic University of Ecuador (PUCE) between 2010 and 2015, verified the symmetrical normal distribution behavior of the two lots in which the data were classified; one corresponding to plants that maintain quality control processes and another to plants without control in addition, quantified the characteristic tyre track value according to the abrasion test in the analysis period. Through the information obtained, the need for abrasion control has been justified, as well as the recommendation to establish a specification for Ecuador, different from that established in the European standard