Khosrow Ghavami

Development of vegetable fibre-mortar composites of improved durability

The primary concern for vegetable fibre reinforced mortar composites (VFRMC) is the durability of the fibres in the alkaline environment of cement. The composites may undergo a reduction in strength and toughness as a result of weakening of the fibres by a combination of alkali attack and mineralisation through the migration of hydration products to lumens and spaces. This paper presents several approaches used to improve the durability performance of VFRMCs incorporating sisal and coconut fibres. These include carbonation of the matrix in a CO2-rich environment; the immersion of fibres in slurried silica fume prior to incorporation in the ordinary Portland cement (OPC) matrix; partial replacement of OPC matrix by undensified silica fume or blast-furnace slag and a combination of fibre immersion in slurried silica fume and cement replacement. The durability of the modified VFRMC was studied by determining the effects of ageing in water, exposure to cycles of wetting and drying and open air weathering on the microstructures and flexural behaviour of the composites. Immersion of natural fibres in a silica fume slurry before their addition to cement-based composites was found to be an effective means of reducing embrittlement of the composite in the environments studied. Early cure of composites in a CO2-rich environment and the partial replacement of OPC by undensified silica fume were also efficient approaches in obtaining a composite of improved durability. The use of slag as a partial cement replacement had no effect on reducing the embrittlement of the composite.

Behaviour of composite soil reinforced with natural fibres

Abstract Next to the food shortage, the housing shortage is one of the most crucial problems on earth. To improve this situation and make it possible to build more houses, particularly for low-income families, it is necessary to examine all locally available materials which can be used for construction. Bamboo, sisal and coconut fibres are materials which are available in abundance in Brazil and are not used in civil construction. To increase the amount of information concerning the physical and mechanical behaviour of these materials several research programmes were executed at Pontifical Universidade Catolica in Rio de Janeiro (PUC-Rio) and Universidade Federal da Paraiba (UFPb) under the general supervision of the first author. In this paper new results are presented concerning the application of sisal and coconut fibres in conjunction with three types of locally appropriate soil for the production of composite soil blocks reinforced with sisal and coconut fibres.

Ultimate load behaviour of bamboo-reinforced lightweight concrete beams

Abstract The classification of seven bamboos studied in accordance to their physical and mechanical properties, the type and method of application of water repellent treatment of bamboo splints and the bond strength between bamboo and lightweight concrete are described in this paper. The results of the experimental analysis of two simplysupported bamboo-reinforced lightweight concrete beams with an overall length of 340 cm and a cross-section of 12 cm by 30 cm width and height, respectively, subjected to two point loads up to collapse are presented. One beam of the same dimensions and concrete mix reinforced with steel was also tested for comparison of the results. Finally a recommendation based on the analysis of the results for the design of such beams is proposed.

Experimental study of stiffened plates in compression up to collapse

Abstract This paper presents the results of an experimental study to examine the behaviour of longitudinally stiffened steel plate with and without transversal stiffeners subjected to uniform axial in-plane load up to collapse. The main objectives in this investigation were to find the influence of the cross-section type of the longitudinal stiffeners and their spacings on the buckling mode and the maximum collapse load. For this purpose most commonly used stiffeners of rectangular (R-), L- and T-type cross-sections for the longitudinal and only T-tyoe cross-section for transversal stiffeners were chosen. The test results have also provided data to evaluate the design formulae for the stiffened plates according to the Brazilian Code for Steel Bridges . Some other codes and recommendations were also studied and were used to calculate the buckling load of the tested plates for comparison.

Treatments of non-wood plant fibres used as reinforcement in composite materials

This paper presents a summary of the knowledge on fibres and pulps of non wood tropical plants used as reinforcement in cementitious composites accumulated during the recent years by Guadeloupean and Brazilian teams participating in collaborative work. Vegetable fibres represent a good alternative as non-conventional materials for the construction of ecological and sustainable buildings. The use of such renewable resources contributes to the development of sustainable technologies. The main objective of the paper is to emphasize the use of agricultural wastes in the production of cement based composites. The botanical, chemical, physical, morphological and mechanical properties of fibres from various plants are described. The effects of different treatments on physical, chemical and mechanical properties of fibres are presented. The most effective treatments in influencing the mechanical and physical properties are pyrolysis and alkaline ones, according to the type of plant. The final choice will have to consider fibre availability, and treatment costs.

Propriedades físicas e mecânicas do colmo inteiro do bambu da espécie Guadua angustifolia

This work presents recent research results concerning the bamboo Guadua angustifolia carried out at the Pontificia Universidade Catolica, Rio de Janeiro, in which the physical, mechanical and meso-structural properties of the whole bamboo culms were determined. The main objective of this study is to make it possible for professionals to use bamboo more frequently as a structural element. The obtained results allow the engineers and architects to choose for their projects the required dimensions such as diameter, thickness and internodal distance, bending stresses, maximum tensile, compression and shearing stresses. The changing of the volumetric fraction along the bamboo thickness and their mechanical properties along the total length of the studied bamboo culms are presented.

Effects of Methane Cold Plasma in Sisal Fibers

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.

Compósitos à base de cimento reforçado com polpa celulósica de bambu. Parte II: Uso de resíduos cerâmicos na matriz

This paper is the second part of a series of two articles concerning the experimental results of newly developed composite with cementations matrix reinforced with bamboo pulp. In this part the results of the investigations concerning the partial substitution of Portland cement by grinded residues from a brick factory are presented. The cement was partially replaced in percentages of 20, 30 and 40% by weight. These composites were reinforced with only refined bamboo pulp. The same procedures described in Part I were adopted and used in the experimental program. Considering the results of the mechanical properties it is verified that 20% of cement replacement presented the best results.

Behavior of cement mortar reinforced with Amazonian fibers subjected to compression

In recent years, there has been intense research worldwide for alternative materials to substitute asbestos fiber, a component of asbestos cement, which has been found to be hazardous to human and animal health and has been banned in many countries. Since 1979 the Non-conventional Materials Research Group of PUC-Rio has carried out research on the application of vegetable fibers, available in abundance in Brazil, for the fabrication of construction components, aiming mainly at the fabrication of popular housing. The Curaua fiber has been studied, as it is already of popular use in the manufacture of ropes, baskets and carpets in the region, known as Baixo Amazonas, in the state of Para, Brazil, where the first plantations have been organized on a commercial scale. In this work, mechanical properties of the Curaua fiber, as well as their application as a cementicious matrix reinforcement, have been studied. The performance of Curaua fiber and its composites was compared with other vegetable fibers, such as sisal and jute, as a substitute for asbestos fiber and its composites. The data on sisal fibres from previous works by the same research group at PUC-Rio was considered for comparison. The behavior of jute fiber, as well as cementicious composites, reinforced with jute and sisal fibers, has also been studied in this work. The results have shown that the Curaua fiber has appropriate physical and mechanical characteristics that make it suitable to be used as reinforcement of cementicious matrixes, with a high ductility and post-cracking resistance capacity.

Compósitos à base de cimento reforçados com polpa celulósica de bambu. Parte I: Determinação do teor de reforço ótimo

This work presents the experimental results of a study which intended to develop a composite with cementations matrix reinforced with bamboo pulp. Two types of pulps were used: refined and unrefined pulps. The fibre content varied between 0 and 16% cement (weight basis). After the preparation of fresh composite mix the experimental specimens were prepared applying a specially developed process based on Hastshek method using suction then moulding and pressing. The compression, tension and the flexural behavior and their constitutive relations were established using 5 cm diameter by 10 cm high cylindrical specimens and three point bending tests at respectively. The energy absorbing capacity of the new composites was also established. Physical properties such as water absorption, apparent porosity, dry and humid density were also obtained. The results showed a better performance of composites with refined fibres when compared to those with unrefined ones. It was observed that the optimum fibre content was approximately 8% of refined fibre which improved the mechanical properties of the composites.