Mônica Regina Garcez

Reactivity Assessment of Residual Rice-Husk Ashes

AbstractThe production of rice-husk ash without controlled burning results in pozzolans with different physicochemical characteristics. The amorphous content of residual rice-husk ash (RRHA) is rel...

Application of heat-activated films as a new generation of adhesives used for bonding fiber reinforced polymers to concrete

The application of FRP for post-strengthening of concrete structures induces the use of elevated temperatures to minimize the curing time of the adhesive. The replacement of traditional adhesives by Heat-Activated Films (HAF), with higher glass transition temperatures (Tg), is na interesting prospect, and has been motivating studies regarding the viability of applying termo-activated adhesives. For this study, notched beams post-strengthened with CFRP bonded with two types of heat-activated films (epoxy and phenolic based) and one classical adhesive were tested in bending at EMPA (Swiss Federal Laboratories for Material Testing and Research). To verify the stress redistribution on the notched beams, a computational model, which divides the structure in solid elements, was implemented. The analysis of the behavior of the concrete-laminate interface demonstrates that numerical models are an efficient tool to supplement and explain experimental data.

ASSESSMENT OF MIX PROPORTIONS FOR DEVELOPING LIGHTWEIGHT CEMENTITIOUS COMPOSITES WITH WOOD WASTES

1 Received on 20.01.2016 accepted for publication on 11.11.2016. 2 Universidade Federal do Rio Grande do Sul, Departamento Interdisciplinar, Tramandaí, RS Brasil. E-mail: <monica.garcez@ufrgs.br>. 3 Universidade Federal de Pelotas, Centro de Engenharias, Pelotas, RS Brasil. E-mail: <estelagarcez@gmail.com>. 4 Universidade Federal de Pelotas, Graduanda em Engenharia Civil, Pelotas, RS Brasil. E-mail: <ali.oli.edi@bol.com.br>. 5 Universidade Federal de Pelotas, Engenharia Industrial Madeireira, Pelotas, RS Brasil. E-mail: <darcigatto@yahoo.com>. *Corresponding author.

AVALIAÇÃO DO DESEMPENHO DE ARGAMASSAS DE ASSENTAMENTO MODIFICADAS POLIMERICAMENTE PARA ALVENARIA ESTRUTURAL

Structural masonry requires technological advances to equated the actual state of development constructions that usually operates with the conventional reinforced concrete structures. Evaluate different technological alternatives it is a necessity in order to improve the performance and mechanical properties of masonry. This study aims to use polymer-modified bedding mortars for structural masonry to increase the mechanical strength and ductility. For this purpose a standard mortar is used with addition of 0%, 5% and 10% of polyvinyl acetate (PVA) and copolymer styrene-butadiene rubber (SBR). Several tests to characterize the mortars, that include, in fresh condition (quantity of incorporated air) and hardened condition (dynamic modulus of elasticity, flexural strength, compressive strength and mercury intrusion porosimetry), were performed. It was also performed compressive strength tests in prisms ceramic blocks with the different types of mortars and adherence tests between block and mortars. The results show that the mortar with 10% PVA recorded the best mechanical performance. This mortar has an increased adherence to substrate and obtained the compressive strength higher than the value obtained with 0% polymer materials. Keywords: structural masonry, bedding mortar, polymer.

Mortar Effect of Rice Husk Ash Burning on Fluidized Flow and Sliding Grid

The rice in the south of Brazil is one of the main economy activities, which produce a large volume of waste coming from the beneficiation industries. The main goal of this research is evaluate the feasibility of use of rice husk ash, burning on fluidized flow (FF) and sliding grid (SG) for mortars. The characterization methods of rice husk ash (RHA) included loss on ignition, particle size distribution by laser, x-ray diffraction, x-ray fluorescence spectrometer, pozzolanic activity index and specific mass. Mortar specimens were molded with the proportion of 1:3 in mass and water/binder ratio of 0.51. The Portland cement was replaced by RHA with the proportion of 10%, 15% and 20%. Compressive strength, water absorption, air voids content, hydration-releasing heat curves, mercury intrusion porosimetry and scanning electron microscope were performed for all mortars. The mechanical performance of mortar with RHA replacement, shows to be satisfactory and feasible alternative for the final waste disposal.

Reforço de vigas de concreto armado com laminados de PRFC protendidos. Parte 2: Análise sob ação de carregamento cíclico.

Different FPR post-strengthening techniques have been developed and applied in existing structures aiming to increase their load capacity. Most of the FRP systems used nowadays consist of carbon fibers embedded in epoxy matrices (CFRP). Regardless of the advantages and the good results shown by the CFRP post-strengthen technique, experimental studies show that, in most cases, the failure of post-strengthened structures is premature. Aiming to better use the tensile strength of the carbon fiber strips used as post-strengthening material, the application of prestressed CFRP strips started to be investigated. The main purpose of this paper is to analyze the effects of the composite prestressing in the performance of the CFRP post strengthening technique. The experimental program was based on flexural tests on post-strengthened reinforced concrete beams subjected to static - part 1 and cyclic - part 2 loading. Experimental results allowed the analysis of the quality and shortcomings of post-strengthen system studied, which resulted in valuable considerations about the analyzed post-strengthened beams.Diferentes tecnicas de reforco que utilizam sistemas PRF formados com fibras de carbono envolvidas em matriz epoxidica (PRFC) tem sido aplicadas em todo o mundo em estruturas que necessitam aumentar recuperar sua capacidade resistente. Apesar dos bons resultados obtidos e das vantagens associadas a estas tecnicas, estudos experimentais mostram que a ruptura das estruturas reforcadas frequentemente acontece de forma prematura, sem o esgotamento da capacidade resistente do PRFC. Recentemente, a utilizacao de PRFC protendidos comecou a ser investigada, visando a um melhor aproveitamento da resistencia a tracao dos laminados de fibra de carbono. Dentro deste proposito, este artigo busca analisar a eficiencia da tecnica de protensao de compositos laminados, atraves da realizacao de ensaios a flexao com carregamento estatico – parte 1 e ciclico – parte 2. Os resultados obtidos possibilitaram a analise das qualidades e fraquezas do sistema de reforco estudado, permitindo a obtencao de consideracoes relevantes sobre as estruturas reforcadas estudadas.

Analytical solution to simulate the behavior of reinforced concrete beams post-strengthened with FRP strips

Aiming to develop an analytical solution to describe the behavior of reinforced concrete beams post-strengthened with FRP systems, with or without prestressing, a non-linear solution based on a tri-linear moment-curvature response was proposed. Three characteristic points were used to define the stages of the moment-curvature diagram: concrete cracking, steel yielding and ultimate capacity of the cross section. The load-deflection responses of the post-strengthened beams were then obtained by a double integration of the moment-curvature curve. This analytical procedure was implemented using the Matlab ® software and the results obtained have closely matched the experimental data collected in bending tests performed in concrete beams post-strengthened with post-tensioned and non post-tensioned FRP strips.