Papers by Author: Khosrow Ghavami

Abstract: The use of compressed earth blocks (CEBs) is widespread in the field of earth construction. They present better mechanical performance than adobe and the equipment for their production is simple. Laboratory testing of compressed earth blocks requires large amounts of material. There are variations of unconfined strength testing procedures such as testing halves of the blocks with layers of mortar between them or testing whole blocks in diverse directions. This complicates the interpretation of test results as the shape factor and mortar characteristics influence the results significantly. Static compaction test can be used to produce cylindrical samples representative of CEBs. The water content of soil used for the production of CEBs is often determined in standard Proctor test while experimental data indicate that the optimum moisture content for static and dynamic compaction is different. The present article addresses the behavior of four soil mixes with varying clay content compacted statically with a constant rate of strain. Static compaction curves were compared with those obtained in standard Proctor test. For all the soil mixes the static optimum moisture content was found to correspond to the start of consolidation. The compaction curve presented no wet side of optimum in contrast to Proctor test. The energy needed to achieve a desired density by static compaction was analyzed for soils with varying clay contents. Static compaction was found to be more efficient than dynamic for clayey soils. An increase in water content was observed to help achieving higher densities at low pressures, which can improve the performance of manual CEB presses.

Abstract: To increase the durability of bamboo it is important to find an easy method to fill the micro and meso structure of the biological matrix using a nanostructural material with an anti-fungical activity. A colloidal solution of silver nanoparticle (Ag-NPs) is a dispersion of metal nanoparticle in water with a diameter between 5-100 nm. Even if the biological mechanism is not completly understood yet, Ag-NPs show a satisfactory bactericidal and antifungical activity. We present a simple and rapid production of Ag-NPs made by a sol-gel synthesis in flow mode by means of microreactor tecnology through a chemical reduction of AgNO₃ with NaBH₄ in presence of two different organic ligands: sodium/potassium tartrate and trisodium citrate. The synthesis of Ag-NPs in continuous flow compared to the batch technique allowed to reduce the time of synthesis, facilitating the reproducibility of the process and consequently obtaining NPs with more uniform physical and chemical characteristics. The microorganisms of the genus Aspergillus were used for the microbiological tests. The effect of different Ag-NPs on microbial growth was observed daily. In particular, it was shown that the response of the fungus is inversely proportional to the size of the nanoparticles, cell growth is disrupt depending on the proportion between silver and organic ligand and microbialstatic effect, especially in relation to sporulation stage was also observed.

Abstract: This paper presents some considerations on the impacts of industrialized construction materials to Planet Earth. It comments about sustainability and show that large part of the present generation has not met their basic needs, starting with the house. So, in this context, with the actual economic model, it becomes difficult to ensure that future generations are able to meet their own needs. Some considerations about possibilities of building with reduced environmental impact is presented. Comments about raw earth as building material are made. New possibilities to give stability to this material against water action is discussed. Finally, it shows some contemporary constructions made with earth in Brazil.

Abstract: The indicators for Science and Technology Innovation (S&T) used for decision-making within the national system of research and innovation related to Non-Conventional Materials and Technologies (NOCMAT), do not concern only the federal political sphere, but also research groups of universities, research institutes and scientific and technical associations. These agents influence is frequently insignificant for decision making when compared to the dominant and centralizing industries which have created their proper indicators for justifying the application of conventional industrialized products. A culture of NOCMAT indicators should be disseminated into the scientific and social communities so that decisions at all levels should be based on relevant, reliable and transparent information, notably at the regional level. The main objective of this paper is to establish the terms of reference of the "NOCMAT Observatory" for Novel Construction Materials & Technologies for Sustainability not yet existing in Brazil, notably defining its role, dynamic organizational framework, "products" and services to be provided.

Abstract: Science and technology have contributed since the Second World War to the economic development without considering adequately different social classes. The intensive Research and Development (R&D) activities in the rapidly growing areas of Science, Technology and Innovation (ST&I) such as new high resistance cements, steel, petrochemical derived materials, among others have not given the opportunity to less developed nations to cut the vicious circle which maintained them technologically dependent on industrialized countries. Also, the results of many successfully realized R&D projects concerned with Non-Conventional Materials and Technologies (NOCMAT) in developing countries including Brazil have not been used in large scale in practice. This is due to the lack of evaluation criteria from planning to project implementation by governmental agencies, private organizations and educational institutions concerned with the newly developed sustainable materials and technologies. The problems of evaluating R&D innovation outputs and impacts for civil construction are complex and need scientific and systematic studies in order to avoid the social and environmental mistakes occurred in industrialized countries. This paper presents four relevant dimensions and its pertinent indicators for NOCMAT projects evaluation concerned with materials, structural elements and technologies of bamboo, soil and composites reinforced with vegetable fibers. Specifically, 1) Political, Strategic and Normative; 2) Organizational; 3) Allocation and Management of Resources; and 4) Technical, Scientific and Economic evaluation dimensions are considered and discussed.

Abstract: One of the main problems in using vegetable fibers as reinforcement in aggressive cement matrix is the penetration of alkaline products in the porous structure of the filaments, making them very fragile with the time. In this sense a series of physical and chemical methods of surface modification has been used in order to improve its characteristics. The plasma surface modification technique is a physical method surface modification that utilizes ionized gas at low pressure to change the chemical nature and the substrate surface morphology of both organic and inorganic materials without changing their intrinsic properties. This is considered an environmentally friendly process without generation of contamination and has a low operating cost compared to some chemical (such as silane based) treatments. In the present study, the sisal fibers were treated with methane plasma generated by direct electric current during 10, 20 and 30 min with gas flow of 5 cm³/s and current of 0.10 A. The study presents some mechanical, physics and chemical characteristics of sisal fiber after being subjected to treatment with methane cold plasma. The results presented indicate that treatment with methane cold plasma induced changes in sisal fibers at all times of exposure to treatment (10, 20 and 30 min). However, the major changes in structural and mechanical components may be seen in fibers treated with 10 min of exposure to plasma.

Abstract: There are more than one thousand of bamboo species around the world, but in some areas the most common is the Bambusa vulgaris. Comparing with other species used in construction, it is more susceptible to insect attack and its strength is slower. This work shows some studies made using culms of this bamboo with the aim to improve its durability and mechanical properties by impregnation of polymeric resins into their vases. Some information about Bambusa vulgaris microstructure is done. The percentage of vases, fibers and parenchyma was measured using an optical microscope. The absorption of this species in liquids with different viscosities was determined. Using an equipment to force the liquid into the vases, time of penetration of fluids with different viscosity was measured. Results show that the fluids penetrate most easily in the internal vases, where the diameter is greater than that close to external face of the culms and confirm that it is possible to fill the bamboo vases with viscous fluid as oil or polymeric resins. The attack of insect was eliminated when a impregnation with a resin made by 80 % de styrene + 20 % de metilmetacriyate was applied to Bambusa vulgaris culms.

Abstract: The present worldwide socio economical system created the actual situation where almost two third of world population lives under the minimum living conditions which have been established by the United Nations criteria. To overcome these deficiencies, there is an urgent need to establish a new paradigm for promoting conservation and environmental sustainability. This paper presents the evaluation criteria for this major concern. The main variables considered are: sufficient availability, renewability, adequate physical-mechanical characteristics, cost efficiency, easy access, simple production, local technology adapted to local conditions, and durability. The non-conventional materials and technologies (NOCMAT) minimize adverse impacts into the environment and also provide adequate products for a market increasingly competitive. Thus, very strict norms and clean technologies should be implemented. Positive results in Brazilian research institutions have been developed on the use of NOCMAT (bamboo, vegetable fibers, bio-composites, recycled conventional materials, etc.) since 1979 at the Pontifical Catholic University of Rio de Janeiro (PUC-Rio, Department of Civil Engineering). Nevertheless, these NOCMAT are not yet sufficiently disseminated and employed in the country due to the lack of sufficient investments. Thus, government incentives and private initiatives must be increased substantially to change this panorama in Brazil.

Abstract: The results of many successfully realized Research and Development (R&D) concerned with non-conventional materials and technologies (NOCMAT) in developing countries including Brazil have not been used in large scale in practice. This is due to the lack of selection and evaluation criteria and concepts from planning and designing to implementation programs by governmental agencies and private organizations concerned with the newly developed sustainable materials and technologies. The problems of selecting and evaluating R&D innovation outputs and impacts for construction are complex and need scientific and systematic studies in order to avoid the social and environmental mistakes occurred in industrialized countries after the Second World War. This paper presents a logical framework for the implementation of pertinent indicators to be used as a tool in R&D of NOCMAT projects selection and evaluation concerned with materials, structural elements and technologies of bamboo and composites reinforced with vegetable fibers. Indicators, related to the efficiency, effectiveness, impact, relevance and sustainability of such projects are considered and discussed.

Abstract: In this paper the result of an investigation using finite element model (FEM) of a simple bamboo pin joint as commonly used in many types of structures especially in plane and space structures is presented. The nonlinear pressure distributions at the contact area of a steel pin in a bamboo circular hole were analyzed considering the anisotropy and heterogeneity of the functionally graded material. In turn the obtained results of the analysis are compared with those based on simplified constitutive models assuming isotropic and homogeneous representations for bamboo. The experimental results are compared with the results obtained from both methods. The assumption of the bamboo as an orthotropic material presented more reliable design method of bamboo structures Although the different maximum forces applied in each case, local stress are relatively high on both cases, showing that this type of connection depends on local reinforcements to be a safe connection. Finally the suggestion that bamboo joints at the hole can be improved by reducing the stress concentration factors, through applying reinforcing elements such as natural fiber straps composites close to the hole.