Rogério Carrazedo

Parametric analysis of carbonation process in reinforced concrete structures through Artificial Neural Networks

The aim of this paper is parametrically analyze the main factors that influence on the progress of concrete carbonation front. Therefore, a numerical model was developed using Artificial Neural Networks (ANNs), considering the Multi-Layer Perceptron class, designed in a C++ objectoriented program. The software was fed by experimental degradation data available in the current literature. The results obtained in the parametric analysis, besides adding knowledge to the building pathology area, reinforce concepts already known in the literature, demonstrating the efficiency of ANNs in the investigation of concrete carbonation.

Estudo dos efeitos do uso da escória de aciaria na expansão de corpos de prova sujeitos à reação álcali-agregado

Abstract Resumo Alkali-aggregate reaction is a chemical reaction between cement alkalis and some reactive mineral present in some aggregates, leading to con-crete expansion and cracking. One kind usually observed and studied in Brazil is the alkali-silica reaction, due to its fast development. There are several methods that are effective to control and mitigate this reaction, and one of them is the partial replacement of cement by mineral additions such as pozzolans like fly-ash, silica fume and slag. In this study, we propose the use of electrical steel slag as a partial replacement of cement, evaluating its effectiveness by NBR 15577:2008, employing different proportions as replacement. It seems that the electrical steel slag, despite its expansive behavior, has been effective in the control of the ASR. Keywords : concrete expansion, alkali-aggregate reaction. alkali-silica reaction, pozzolans, steel slag.A reacao alcali-agregado (RAA) e uma reacao que ocorre entre os alcalis do cimento e alguns compostos minerais presentes em determinados agregados, gerando consequencias ao concreto, como por exemplo, fissuracao. A reacao com maiores ocorrencias registrada no Brasil e a re-acao alcali-silica (RAS), devido a rapidez com que esta ocorre em funcao das formas minerais reativas envolvidas. Varios metodos estudados ja se comprovaram eficazes para o controle desta reacao, sendo um deles a substituicao parcial de cimento por adicoes como as pozolanas, dentre as quais podem ser citadas as cinzas volantes e as escorias de origem siderurgica. Neste sentido, este trabalho tem por objetivo o estu-do da utilizacao da escoria de aciaria eletrica como redutor da reacao alcali-agregado, sendo desenvolvido com base nas orientacoes da NBR 15577:2008 Agregados – Reatividade Alcali-Agregado, avaliado para diferentes proporcoes de substituicao parcial de cimento por escoria. A escoria de aciaria eletrica, uma pozolana nao tradicional resultante do processo de producao do aco e de caracteristicas expansivas, teve exito ao reduzir a expansao da RAS.