Gisleiva Cristina dos Santos Ferreira

Ensaios de arrancamento e de empuxamento aplicados a taliscas de bambu encravadas em corpos-de-prova de solo-cimento

Neste trabalho, taliscas de bambu da especie Dendrocalamus giganteus, engastadas em corpos-de-prova de solo-cimento, foram submetidas a ensaios de arrancamento (pull-out) e de empuxamento (push-out) a fim de se determinar sua resistencia de aderencia. Para esta finalidade, foi utilizado um solo-cimento feito a partir de um solo arenoso que continha aproximadamente 70% de areia. Corpos-de-prova de solo-cimento, de 15 cm de diâmetro e 30 cm de altura, foram moldados com 14% de cimento na umidade otima de 10,7%. As taliscas de bambu foram preparadas com 2 cm de largura e comprimentos de 40, 50 e 60 cm, para o ensaio de arrancamento, e de 70 cm para o ensaio de empuxamento. Metade das taliscas foi deixada sem tratamento impermeabilizante e a outra metade foi revestida com emulsao asfaltica, impregnada com areia limpa grossa, para produzir uma superficie aspera e garantir melhor aderencia com o solo-cimento. Os corpos-de-prova de solo-cimento com as taliscas de bambu engastadas, foram deixados a curar em câmara umida, durante 28 d, antes de serem ensaiados. Ambos os ensaios foram realizados em uma maquina universal de ensaio adaptada, sendo as deformacoes medidas com um relogio comparador aferido, de sensibilidade igual a 0,01 mm. A resistencia de aderencia, quer fosse determinada pelo ensaio de arrancamento quer pelo ensaio de empuxamento, foi obtida dividindo-se a maxima carga verificada no ensaio pela area lateral da talisca de bambu efetivamente engastada no solo-cimento. Os melhores resultados foram obtidos sem aplicacao de material impermeabilizante, para o ensaio de arrancamento, enquanto nenhuma diferenca foi observada entre os dois tratamentos para o ensaio de empuxamento.

Effect of coupling media on velocity and attenuation of ultrasonic waves in Brazilian wood

Coupling media are necessary to ensure that transducers bond to wood specimens to minimize coupling losses and improve the accuracy of ultrasonic measurements. There are several types of coupling media available, and the optimal choice is not known. In this work, we analyzed the results of ultrasonic wave attenuation for 0.1-MHz longitudinal and transverse transducers with six different materials as coupling media in nine species of Brazilian wood with densities in the range 700–1170 kg/m3. Tests were performed using constant pressure on the transducer and with wave propagation in the longitudinal direction. For transverse transducers, the polarization was in the radial and tangential directions. The results were analyzed statistically and showed that, for attenuation in both longitudinal and transverse waves, the material used for coupling had significant effects, whereas the wood species had no effect. For longitudinal waves, the statistical evaluation showed that the coupling material performance was strongly dependent on the species of wood, but it was not possible to observe any tendency of behavior associated with specific anatomical properties.

Cola à base de PVA e argamassa de solo-cimento como alternativas para o assentamento de alvenaria de tijolos maciços de solo-cimento

This study presents the results of an experimental investigation in characterizing the properties of cement soil block masonry using cement-soil mortars and PVA glue. The study deals with the scantily explored area of tensile bond strength of soil-cement block masonry using cement-soil mortars and PVA glue. Flexural bond strength of masonry has been determined by testing stack-bonded prisms using a bond wrench test set-up. The study clearly demonstrates the superiority of cement-soil mortar over other conventional mortar such as cement mortar. The results of this study can be conveniently used to select a proportion for cement-soil mortar or PVA glue proportion for cement soil block masonry structures.

Evaluation of coal fly ash in cementitious matrices

Resumo The addition of ash, initially classified as waste in cement matrices, is essential to achieve the requirements of National Policy of Solid Waste. However, technologies that enable such applications should be sought, especially when the material has adequate pozzolanic activity. The aim of this study was to verify the pozzolanic activity of fly ash from coal burning, from the aluminum manufacturing process, such as mineral admixture in mortars and conventional concrete. For that, physicochemical characterization of the ash sample and the mechanical behavior of mix dosage of mortar and commercially used concrete tests were carried out. Results showed the ash in evaluation has pozzolanicity as relevant standards employed and when inserted in the studied cementitious matrices, showed the expected performance for this type of addition (higher mechanical strength at older ages).

Flexural and shear behaviour of concrete beams reinforced with bamboo

The performance of bamboo as reinforcement in concrete structures can be successful if safety limit conditions are considered. The aim of this paper is to evaluate the feasibility of bamboo strips application as a flexure and shear reinforcement in concrete beams. Culms from Dendrocalamus giganteus were split and employed as reinforcement using rectangular sections of 20 mm width × natural length of the bamboo. Experimental analysis of six simply supported bamboo-reinforced concrete beams subjected to two point loads was carried out up to collapse. The ultimate test loads for the different beams were compared to the loads predicted according to ACI 318 (steel reinforced concrete beams regulation). Finally, a recommendation based on the analysis of the results for the design of such beams is proposed.

Functional and environmental performance of waste foundry sand applied in landfills

The use of waste foundry sand (WFS) up to 70% of soil mixtures in landfills has shown substantial promise, taking into account the great volume of this waste and the environmental parameters. The objective of this research was to investigate the utility and environmental benefits of a clay soil mixed with a waste foundry sand sample to cover landfills of solid waste. Environmental, physical, chemical and mechanical tests were performed on a sample of WFS and a mixture of soil plus 70% waste foundry sand.The use of waste foundry sand (WFS) up to 70% of soil mixtures in landfills has shown substantial promise, taking into account the great volume of this waste and the environmental parameters. The objective of this research was to investigate the utility and environmental benefits of a clay soil mixed with a waste foundry sand sample to cover landfills of solid waste. Environmental, physical, chemical and mechanical tests were performed on a sample of WFS and a mixture of soil plus 70% waste foundry sand.

Inspection of Historic Building Facades for a Development of Restoration Project

The objective of this study was to substantiate the importance of inspection and preliminary tests before the interventions of restoration of historic building. To do this, set up a building listed as Brazilian historical heritage for a case study. Through inspection was possible to identify the proliferation of biofilm as pathology with greater incidence and testing allowed the knowledge of the characteristics of the materials of the facades. Thus, the combination of the two processes was essential for the preparation of the restoration project, indicating the most appropriate therapies to types of pathologies found.

Avaliação de blocos de concreto vazados não convencionais por ensaios não destrutivos e destrutivos

The aim of this study was to evaluate cementitious matrices properties by partial replacement of Portland cement by silica fume (SF) or by rice husk ash (RHA), and their application in nonbearing hollow blocks, tested by destructive and non-destructive methods. The following mixtures were produced: reference (100% of Portland cement) and Portland cement replacement (10% by mass) with SF or RHA. The non-destructive testing showed that the highest values of UPV were obtained for SF-based blocks and RHA-based blocks. The destructive test showed better results for SF-based blocks, but there was no statistical difference between the RHA-based and control ones.

Capacidade resistente e modos de ruptura de vigas de concreto armado reforçadas à flexão com fibras de carbono

Para se projetar um reforco a flexao com material polimerico reforcado com fibras, em uma viga de concreto armado, e necessario que o engenheiro responsavel opte por trabalhar sem a utilizacao de mecanismos de incremento de ancoragem, obviamente dentro de niveis seguros, ou utilize artificios que lhe garantam alcancar a deformacao ultima de projeto da fibra fornecida pelo fabricante da manta. Nesse artigo, e apresentada a base para o calculo das duas metodologias, segundo os criterios mais expressivos existentes, e sao feitas comparacoes com resultados experimentais. Para o reforco sem ancoragem, verificou-se que, para se evitarem as indesejadas rupturas prematuras e bruscas, as metodologias propostas pelos ACI e FIB mostraram-se adequadas. Para se garantir a deformacao ultima da fibra, foi estudado um mecanismo com ancoragem lateral a 45° feito com o proprio material da fibra. Nesse caso, utilizou-se o processo de secoes balanceadas, para a previsao do modo de ruptura, e, em seguida, foram feitas as devidas comparacoes entre os valores esperados com os resultados obtidos nos ensaios em laboratorio.