The work studies the influence of the addition of 2% calcium carbonate during the drying stage and the efficiency of the firing stage during the manufacturing processof red ceramic bricks. The study was conducted in a factory producing hollow bricks with an installed capacity of 65,000 bricks per burning. Results from the studyshowed that the addition of 2% CaCO3 to the clay paste reduces the drying time by 35% compared with bricks made without addition, and causes a 27% reductionof the fuel consumption in relation to previous burnings without the addition of this flux, due to the reduction of the firing time in the ovens.
Rev. ing. constr. [online]. 2013, vol.28, n.2, pp. 113-124. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732013000200001
This paper presents the study of seismic vulnerability of extradosed bridges during cantilever construction. The seismic response during six construction phases and two in service, before and after creep and shrinkage of concrete takes place, of a 3-span extradosed bridge (60 + 100 + 60 m) were determined by means of finite elements models. Using the approach proposed by Wilson and Holmes (2007), seismic response during construction and in service were compared to determine structural elements with higher vulnerability and to detect critical stages during construction. The results show that the seismic vulnerability of the bridge during construction is higher than in service, this is supported on the fact that during construction annual exceedance probabilities are higher than 0.21%, a commonly adopted value for the seismic design of bridges. Furthermore, it was found that extradosed cables and the towers are the most vulnerable elements and that the stages before the closure of the bridge during construction are the most critical.
Rev. ing. constr. [online]. 2013, vol.28, n.2, pp. 125-139. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732013000200002
The effect of the incorporation of a petrochemical industry waste, named spent fluid catalytic cracking (FCC) in the hydration process and microstructure of cementpaste, was studied. Portland cement (OPC) pastes, with and without addition of meta-kaolin (MK) and silica fume (SF), were used as reference materials. The characterizationof the type of hydration products was performed by using X-ray diffraction (XRD), thermo-gravimetric analysis (TG), scanning electron microscopy (SEM) andnuclear magnetic resonance (NMR). This study is complemented with the evaluation of compressive strength of blended cement mortars up to 90 days of curing. Themain products of hydration in cement pastes, added with FCC, were calcium silicate hydrate (CSH); calcium aluminate hydrates (CAH) and hydrated calcium aluminosilicates(CASH). The addition of 10% of FCC reports lime consumption from 61% to 360 days of curing; this value is higher than the ones reported by the additions ofMK and HS in the same percentage of addition. This indicates a higher reactivity of the FCC, which is manifested even at early ages. It should be noted that, consideringthe dilution factor, the addition of 10% FCC as cement replacement contributes to the strength of the blended material in the order up to an additional 30%. This isindicative of the potential use of this waste as supplementary material in cementitious mixtures.
Rev. ing. constr. [online]. 2013, vol.28, n.2, pp. 141-154. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732013000200003
In this article, the process of adopting the eco-design standard ISO14006 and its influence on the results in the architecture firms sector have been analyzed. With theseaims, following an introduction and a description of the eco-design standard ISO14006, its dissemination has been presented. About this aspect, it should be remarkedthe strong impact that this standards has among the architecture firms. Subsequently, the research methodology based on the study of nine cases is shown. The resultshave been crossed with the data obtained from interviews with consultants, auditors, organizations that act as driving forces and a member of the technical committeeISO/TC207 at different times in the course of the investigation. Motivations, challenges and results of the process of adoption and certification of ISO14006 by architecturefirms are then analyzed. Among the major findings, it was found that the adoption of the standard ISO14006 can be a helpful tool in order to improve the competitivenessof the architecture firms. Finally, in the last chapter of the article, some interesting conclusions both for architecture firms and institutions, in general, are shown.
Rev. ing. constr. [online]. 2013, vol.28, n.2, pp. 155-171. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732013000200004
Labor productivity in construction industry is gaining increasing attention as the industry faces multiple problems related to its workforce. Most of construction projects in the Gaza Strip were suffering from declining productivity and thus causing projects delay, and cost overruns. The aim of this paper is to determine contractors’ perceptions towards the identified productivity improvement factors according to their relative importance in construction projects in the Gaza Strip. A comparison was made with other developed and developing countries. Eighty-three productivity improvement factors were considered in the questionnaire and categorized into eleven groups. A survey was conducted among construction firms in the Gaza Strip to rank these factors by their degree of influence on productivity of construction projects. Ninety questionnaires were randomly distributed among local contractors whereas seventy three valid questionnaires were collected from respondents. The findings of this study indicated that the most significant productivity improvement factors are: closures and economical difficulties, political situation, delivery on time, field management, and material availability. External circumstances group was found the most important group which affects productivity improvement in the Gaza Strip as the unstable political atmosphere affects badly the construction industry. A proactive relationship has to be established among all parties in order to allocate effective productivity improvement plans. It is hoped that, by identifying and ranking the major problems affecting construction productivity should help contractors to facilitate proper solutions as well as determining potentials for productivity improvement. The industry needs to collaborate more with universities and research institutions in order to plan an effective strategy through which construction industry could be enhanced. Training can increase productivity, morale, reduce the load on supervisors, improve safety, and increase organizational stability and flexibility.
Rev. ing. constr. [online]. 2013, vol.28, n.2, pp. 173-206. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732013000200005
In the design of foundations in piled rafts, a great number of unknown facts are determined in order to obtain a rational foundation, which in turn meets the requirements of the project. The use of spreadsheets facilitates the work for the designer, to estimate the dimensions of foundation, thus evaluating the influence of various parameters involved in the design, so as to finally use computer programs for the final calculation. This paper shows the results obtained from spreadsheets programmed by MathCad and, it compares the values of the estimated curve load v/s deformation of spreadsheets with the results of full scale models and others from literature on the subject.
Rev. ing. constr. [online]. 2013, vol.28, n.2, pp. 207-216. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732013000200006
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