In this paper are presented some of the technologic properties of cementitious material elaborated by alkali activation of aluminosilicates are presented. More specifically it is about the properties of alkali activated fly ash concrete and mortar (without Portland cement). So depending on the type of alkali activator that is used and after a previous thermal curing, the resulting material will show an interesting list of properties and features that includes: high  initial mechanical strengths (under flexure and compression), low drying shrinkage, and a very good matrix-steel bonding, as well as an excellent strength to acid attack and an excellent behaviour when is exposed to fire. That is the reason why these new cements, due to their magnificent and durable technologic features as well as its easy adaptability to the existing installations in the precast industry, can be used in a variety of applications, for example: elaboration of railroad cross ties, blocks for building or paving, and so others.

Rev. ing. constr. [online]. 2009, vol.24, n.3, pp. 213-232. ISSN 0718-5073.  http://dx.doi.org/10.4067/S0718-50732009000300001

The effectiveness of calcium nitrite based corrosión inhibitor as a prevention method of steel reinforcing bars embedded in cracked concrete slabs was investigated. A factorial design was deveioped to evalúate the effect of cracking in concrete considering crack width and water-to-cement ratio as factors. Then, the effect of a constant dosage of 25 L/m3 of Calcium Nitrate Inhibitor (CNI) on different crack sizes for 0.4 w/c ratio concrete was evaluated. The response was the corrosión current density using linear polarization resistance of small-scale concrete slabs containing steel reinforcement with a cover depth of 20 mm. The slabs were exposed to a natural marine environment during five years with two cycles of wetting and drying per day at the Fundy Bay Maine, U. S. A. The specimens were also visually inspected on regular basis and the surface damage was recorded. It was found that for most of the cases the use of CNI inhibitor was beneficial in both uncracked and cracked concrete.

Rev. ing. constr. [online]. 2009, vol.24, n.3, pp. 233-244. ISSN 0718-5073.  http://dx.doi.org/10.4067/S0718-50732009000300002

One of the most important depassivation mechanisms of steel reinforcement in concrete is that caused by the neutralisation of the cement matrix. In this work, a summary of the development of a model for the carbonation of cementitious matrixes (UR-CORE) is presented. On one hand, in-situ monitoring of the changes that take place in the phase composition of cement pastes during accelerated carbonation (100% C02) for different binders, is reported, by taking Neutrón Diffraction patterns in parallel with the carbonation experiments. The variation of the intensity of chosen reflections for each phase along the experiment supplied data, in real time, for fractional conversión of different phases. On the second hand, fitting of these results allowed to make a quantitative approach to the kinetics of the carbonation of the different phases, and develop the UR-CORE model that is based on the principies of the "unreacted-core" systems, typical of chemical engineering processes.

Rev. ing. constr. [online]. 2009, vol.24, n.3, pp. 245-258. ISSN 0718-5073.  http://dx.doi.org/10.4067/S0718-50732009000300003

The present research intends to develop studies on reinforced concrete beams by applying controlled damage corrosion to cross-sectional reinforcements, thus finding relationships between different stirrups corrosion levels and shear strength due to diagonal tensile stress. Two series of eight beam specimens were constructed, each series having a stirrup spacing distance of 150 and 200 mm. The beams are exposed under wetting/drying cycles, with a 3.5% NaCl solution. In this paper, preliminary results are discussed related to the control of stirrups corrosion potential while the beams are exposed to NaCl. The obtained results will allow understanding the effect of stirrups corrosion level upon beams shear strength behavior, and the corresponding cracking pattern

Rev. ing. constr. [online]. 2009, vol.24, n.3, pp. 259-270. ISSN 0718-5073.  http://dx.doi.org/10.4067/S0718-50732009000300004

The present research shows the results of an equation that allows to dose pervious concrete in function of water to cement ratio and the required interconnected void content in hardened concrete. Eighteen different mixtures - with w/c ratio between 0.29 and 0.41- were analyzed using this equation. The samples were made in the laboratory and compacted with a heavy roller simulating site conditions. The results allow a good characterization of these mixtures both mechanical and hydraulic behavior. Reliationships between void contents, infiltration rate and flexural strength were found.

Rev. ing. constr. [online]. 2009, vol.24, n.3, pp. 271-284. ISSN 0718-5073.  http://dx.doi.org/10.4067/S0718-50732009000300005

This paper presents the stages of a training program of manpower in the field of Civil Construction for a period of two years; it has been developed in order to get the versatility of the workers. The research was conducted with 22 workers in a pilot site in the city of Encarnación in Paraguay, enabling this to obtain data on changes in production and the impact these have generated in the construction process. The training program was implemented in the workplace, the construction site, starting with a survey about the needs of the operators, this, to make decisions about the disciplines that would be administered. Later, after the training there were qualitative and quantitative assessments. Once completed the workers training on competencies, it undertook a survey of services performed by them in relation to productivity and quality, the results were compared with another group of not trained workers. With this work it was found that it is very important for a company to improve the human resources management, since it gives more prestige to have a staff of qualified and multi-skilled workers, it also became clear that this achieves an increase in the productivity and quality indicators.

Rev. ing. constr. [online]. 2009, vol.24, n.3, pp. 285-309. ISSN 0718-5073.  http://dx.doi.org/10.4067/S0718-50732009000300006