Marcos Oliveira de Paula

Potencial da cinza do bagaço da cana-de-açúcar como material de substituição parcial de cimento Portland

This study is focused on the evaluation of the effects of the partial replacement of Portland cement by sugarcane bagasse ash (CBC) in mortars. The main objective was to find a suitable destination for an agricultural residue generated in an increasing amount in Brazil, as a result of the boom of the use of ethanol as an alternative fuel to gasoline. Also, the use of CBC as a mineral admixture in mortars and concretes contributes to a decrease in the environmental impact of these materials related to cement production. Experimental techniques were applied both for the CBC characterization and for the evaluation of its use as a mineral admixture in mortars, based on mechanical and physical tests. The yield of CBC from sugarcane bagasse burning was 10% (weight basis). The CBC presented a SiO2 content of 84% and a carbon content of 5%. Silica presented both amorphous and crystalline (cristobalite and quartz) structure. The pozzolanicity index applied indicates the reactivity of the CBC. Concerning the compression strength, the results from tests with mortars with up to 30% of CBC content indicated the viability of the partial substitution of cement by up to 20% of the CBC considered.

Thermo-mechanical analysis of Corymbia citriodora wood subjected to thermal gradients

Wood exposed to stress conditions, such as temperature gradients, may lead to collapse of installation structure. The rate at which wood becomes charcoal is crucial because of the reduction of the resistant section. This research aimed to evaluate the thermo-mechanical behavior of Corymbia citriodora wood subjected to temperature gradients and different exposure times, under different treatments (Varnish and CCB), in order to minimize the carbonization process. With respect to mechanical tests, it is possible to affirm that the increase in carbonization temperature and time of exposure of the samples resulted in a decrease in the compression strength parallel to the fibers of the material, causing brittleness. The treatments (Varnish and CCB) tested did not present satisfactory results with respect to combustion delay; therefore, they are not recommended for such purposes.

VARIAÇÃO DOS MÓDULOS DE ELASTICIDADE E RUPTURA EM MADEIRA DE CEDRO-AUSTRALIANO POR MEIO DE ENSAIOS NÃO DESTRUTIVO E DESTRUTIVO

The elastic of modulus is an important mechanical property in the design of timber structures, so obtaining it through several methods needs to be evaluated. This study aimed to evaluate the use of an efficient technique for determining the apparent longitudinal modulus taking into account the relationship range/height ( L/h ) and the influence of the shear modulus by comparing non-destructive tests with static bending tests. The wood used in paper was Toona ciliata M. Roemer (Australian cedar). Non-destructive tests were performed with the techniques of longitudinal and transverse vibration. It was concluded that the assay of longitudinal vibration is most suitable method to obtain the apparent longitudinal elasticity modulus, because the shear forces that occur due to the shear stresses are not significantly influenced by the variations of the ratio L/h . It was also possible to conclude that the relationship range/height, currently 21 in ABNT’s standards, may be replaced by 20, when determining apparent longitudinal elasticity modules and modulus of rupture, through the static bending and free transverse vibration tests.

Evaluation of costs of two harvester models in the cut of Eucalyptus

The present study aimed to carry through the evaluation of costs of two models of harvester in the wood harvesting of Eucalyptus wood. The research evaluated the 6-year old tree fallen and processing, in the cut-to-length system for two models of harvester, in areas located in the cities of Conceição da Barra, 1 Engenheira Florestal, Dr., Professora Adjunta do Departamento de Ciências Florestais e da Madeira, Universidade Federal do Espírito Santo, Av. Governador Lindemberg, 316, Bairro Centro, CEP 29550-000, Jerônimo Monteiro (ES), Brasil. elizabeth@cca.ufes.br 2 Engenheiro Florestal, Dr., Professor Titular do Departamento de Engenharia Florestal, Universidade Federal de Viçosa, Av. P.H. Rolfs, s/n, Campus Universitário, CEP 36570-000, Viçosa (MG), Brasil. machado@ufv.br 3 Engenheiro Florestal, Dr., Professor Adjunto do Departamento de Ciências Florestais e da Madeira, Universidade Federal do Espírito Santo, Av. Governador Lindemberg, 316, Bairro Centro, CEP 29550-000, Jerônimo Monteiro (ES), Brasil. fiedler.pq@cnpq.br 4 Engenheiro Florestal, Dr., Professor Titular do Departamento de Engenharia Florestal, Universidade Federal de Viçosa, Av. P.H. Rolfs, s/n, Campus Universitário, CEP 36570-000, Viçosa (MG), Brasil. machado@ufv.br 5 Engenheiro Civil, Dr., Professor Adjunto do Departamento de Engenharia Rural, Universidade Federal do Espírito Santo, Alto Universitário s/n, Guararema, CEP 29500-000, Alegre (ES), Brasil. marcos.paula@ufes.br 6 Engenheiro Florestal, Msc., Doutorando em Ciências Florestais, Programa de Pós-Graduação em Ciências Florestais, Universidade Federal do Espírito Santo, Av. Governador Lindemberg, 316, Bairro Centro, CEP 29550000, Jerônimo Monteiro (ES), Brasil. flaviocipriano@hotmail.com 7 Engenheira Agrônoma, Dra., Professora Adjunta do Departamento de Engenharia Rural, Universidade Federal do Espírito Santo, Alto Universitário s/n, Guararema, CEP 29500-000, Alegre (ES), Brasil. gisele.moreira@ufes.br 8 Engenheiro Florestal, Mestrando em Ciências Florestais, Programa de Pós-Graduação em Ciências Florestais, Universidade Federal do Espírito Santo, Av. Governador Lindemberg, 316, Bairro Centro, CEP 29550-000, Jerônimo Monteiro (ES), Brasil. coelho.fernando@yahoo.com.br Recebido para publicação em 17/10/2011 e aceito em 25/03/2013