A concern with a great number of bridges with significant pathological problems was the motivating factor to carry out this research. Small and medium size bridges have significant relevance for the economic and social development of the country, because they must ensure the transit of people, vehicles with raw material and local produce. However, the precarious conditions of bridges in the urban and rural areas make the displacement difficult, causing discomfort and unsafety for users. Furthermore, the transportation costs for producers and the maintenance for the local government continue to increase. This article intends to show the conservation conditions of small and medium sized bridges in the urban and rural region of Campinas (SP)-Brazil. Thus, this study is based on the analysis of four bridges of this region, in which is presented several examples in situ of the pathological manifestations in concrete, steel and wood bridges. This article also focuses on the design of bridges and its relationship with the pathological condition establishing concepts that could be applied to the corrective method and the pathology identification in concrete, steel and wood bridges. Finally, it aims to conclude that the most appropriate way to avoid a pathological state is preventive maintenance.
Rev. ing. constr. [online]. 2011, vol.26, n.1, pp. 05-24. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732011000100001
Currently economical and environmental advantages of cement clinker replacement by other supplementary cementious materials are well known. For example calcined clays, such as metakaolin, have drawn special attention during recent years. It is well known that these admixtures added to mortars and concretes improve mechanical strength as well as durability. The purpose of this study is to evaluate the behavior of physical-mechanical properties and durability in micro-concretes, by employing calcinated and grinded clays as replacement material, by 30% of ordinary Portland cement (OPC). Therefore, clay soil was employed, which is mainly composed by low-purity-kaolin mineral, so as to obtain calcined clays to be used as supplementary cementious minerals. Best results for compressive strength at 28 days were obtained by sedimentary calcined clays, which have higher content of kaolin mineral thanks to a purification process by means of raw material sedimentation conducted on this admixture only. Nevertheless, capillary water absorption tests delivered best results for calcined clay soil, which finesse is quite high. Lower values showed by this admixture, as much for capillary porosity and sorptivity, revealed there was a predominance of compaction and impermeability phenomena achieved by cementious matrix using such fine material, over the effect of puzzolanic reaction. Micro-structure studies on C-S-H gel, employing energy dispersive x-ray (EDX) technique, demonstrated that the use of calcined clays as replacement of RPC favors the creation of quite stable hydration products, mainly monosulfos of hemicabo and monocarbo types, which is convenient for concrete against possible deterioration actions from different mechanisms.
Rev. ing. constr. [online]. 2011, vol.26, n.1, pp. 25-40. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732011000100002
To bid or not to bid for a certain project is considered to be a crucial decision for contractors' survival. The objective of this paper is to identify and rank the factors that affect the bid/no bid decision according to their relative importance from the perspective of the local contractors operating in the Gaza Strip, Palestine. A total of seventy-eight factors were identified through a comprehensive literature review to evaluate the most important factors that affect the contractors' decisions to bid or not in the Gaza strip. A survey was conducted on a sample of seventy three contractors classified under the building category, and sixty five of them responded with response rate 89%. The results illustrate that, the financial capability of the contractors, the reputation of the clients, the financial capability of the clients, the financial values of the project, the availability of construction raw materials in the local markets, and the stability of the construction industry were the most critical factors affecting the contractors bid-no bid decisions. This study suggests that contractors and clients should improve their financial systems and capabilities in order to stay in business.
Rev. ing. constr. [online]. 2011, vol.26, n.1, pp. 41-60. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732011000100003
Due to the development of Bogota (main city of Colombia) and to its increase of population, transport systems have been constructed in the last decade. Although these systems increase the well-being of the citizens, the traffic could generate vibrations problems. These vibrations could affect the people and the constructions near to highways. These effects can be important for high levels of vibrations. These vibrations, depend, among others aspects, of the mechanical characteristics of the soils. Considering the future plans of construction of transportation systems in Bogota, vibrations due to traffic and railroad in 6 sites of Bogota were registered. In this places were indentified typical soils of the seismic microzoning of Bogota. Measurements were made to register the vibrations due to the train of the savannah, Transmilenio (articulated buses) and public transport mainly. With this information curves of attenuation of acceleration and speed were determined. The actual vibrations levels are perceived by the people but they do not cause problems to the buildings. However, these vibration levels are the datum point of future measurements when increase the traffic, the weight and the speed of the vehicles.
Rev. ing. constr. [online]. 2011, vol.26, n.1, pp. 61-80. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732011000100004
In this work the technique of impedance spectroscopy electrochemistry (EIS) was used to evaluate the effects of carbon dioxide on the corrosion of ASTM A 706 structural steel embedded in concrete with alkali activated slag (AAS), AAS concrete is a mixture of ground granulated slag, fine and coarse aggregates and alkaline solution (sodium silicate) in the amount required for the concrete mix. The study was conducted in comparison with specimens exposed to natural conditions with a low concentration of CO 2 (0.03% CO2 ). The carbonation of the concrete was obtained through accelerated carbonation under controlled conditions (3% CO2, 65% of relative humidity and 20ºC of temperature). The data of Impedance in the middle frequency region 1mHz - 100KHz. A high frequency response was found using the interface-specific exposure and low frequency response corresponding to the specific interface – steel. EIS was used to established the ability to achieve passivation of steel embedded in AAS concrete in natural and accelerated environmental conditions.
Rev. ing. constr. [online]. 2011, vol.26, n.1, pp. 81-94. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732011000100005
Radon gas is a pathological agent for inhabitants of buildings where it is present. Due to its origin in uranium decay chain, it bears radioactive effects that inside human body lead to higher risks of developing lung cancer. It comes from soils containing granite masses or other substrates containing uranium. It enters through common material used in constructions, such as concrete ground slabs, basement walls, etc. In order to avoid such gas immission into inhabited rooms, several measurements cab be considered for existing buildings. This study intends to show the results obtained for radon reductions by means of different constructive solutions, already designed and executed so as to stop radon gas immission into a prototype building constructed for this specific purpose.
Rev. ing. constr. [online]. 2011, vol.26, n.1, pp. 95-121. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732011000100006
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