ABSTRACT The present work assessed the feasibility of applying blasted copper slag (BCS) as addition to cementitious composites. Series with 0-15% of BCS were produced and characterized by compression strength, durability, spread and specific gravity. In fresh state, the workability was enhanced in until 250% when adding the slag. Besides, both mechanical strength and durability indicators of BCSR-added concrete were also improved. Although the greater strength at the ages of 7 and 28 days was achieved for the reference concrete, concretes containing 5% and 7.5% of BCSR also reached the expected resistance of 30 MPa at 28 days. Concretes containing 5% and 10% of the slag were the ones that less absorbed water. The reduction in capillary absorption reached 63% in comparison to the ref concrete for 5% BCS-modified concrete. The incorporation of BCS improved the performance of the reference concrete in terms of both mechanical strength and durability. So, the reuse of the BCS produced after abrasive blasting in concretes was viable and sustainable disposal alternative.

RESUMO Fibras de aço são largamente utilizadas para os mais diversos fins na construção civil. A principal utilização é para reforço estrutural. Nessa aplicação as fibras atuam como ponte de transferência de tensão no compósito por meio do atrito entre a fibra e a matriz. Um meio para potencializar a aplicação de fibras em compósitos cimentícios é a alteração da superfície das fibras por meios físico químicos de modo proporcionar maior interação entre a fibra e a matriz. Neste trabalho é proposto um tratamento químico com dois tipos de silano, o Tetraetoxissilano (TEOS) e o Glicidoxipropiltrimetoxissilano (GPTMS). Foram realizados tratamentos de funcionalização por processo úmido e rota ácida com banhos sequenciais e cura após tratamento com silanos em porções de 1 e 10% em volume na solução e posteriormente analisados por MEV/EDS e método gravimétrico. Foram obtidas fibras de aço com silanos depositados em sua superfície. Foi verificado que quanto maior a concentração do banho de silano, maior é a deposição de silano na superfície das fibras. Em paralelo, verificou-se o aumento expressivo da concentração de silício em função do teor de silano nos banhos de funcionalização. Também se verificou que os filmes de silano quando espessos apresentam fragilidade à abrasão, sendo possível remover parte do filme por meio do atrito entre as fibras.

ABSTRACT Steel fibers are widely used for the most diverse purposes in civil construction. The main use is for structural reinforcement. In this application, the fibers act as a stress transfer bridge in the composite through the friction between the fiber and the matrix. One way to enhance the application of fibers in cementitious composites is to change the surface of the fibers by physical chemical means in order to provide greater interaction between the fiber and the matrix. In this work it is proposed a chemical treatment with two types of silane, Tetraethoxysilane (TEO)S and Glicidoxypropiltrimethoxysilane (GPTMS). Functionalization treatments were carried out by wet process and acid route with sequential baths and cured after treatment with silanes in portions of 1 and 10% by volume in the solution and later analyzed by SEM/EDS and gravimetric method. Steel fibers were obtained with silanes deposited on its surface. It was found that the higher the concentration of the silane bath, the greater the deposition of silane on the surface of the fibers. In parallel, there was an expressive increase in the concentration of silicon as a function of the silane content in the functionalization baths. It was also found that silane films when thick show fragility to abrasion, being possible to remove part of the film through friction between the fibers.

ABSTRACT The study of silanes and polymers with special functions is increasing and the development of materials from silane-based polymers follows this trend. In this way, the hydrolysis of 3-Glycidoxypropyltrimethoxysilane (GPTMS) was studied as a function of the hydrolysis time in solutions with 50% of alcoholic solvents by infrared spectroscopy. It was verified that it was possible to analyze qualitatively and quantitatively the chemical reactions involving the hydrolysis / condensation of GPTMS and the main kinetics variations during the process. The results suggest that up to 30 minutes of hydrolysis, the predominant reactions are hydrolysis of the alkoxy groups, with the generation of the Si-OH groups and alcohol, in this case methanol. From 30 minutes, there is a large amount of silanols in the solution that tend to condense and form siloxane groups, which has this reaction accelerated from 60 minutes. Already, from 70-80 minutes, the reactions tend to decrease the kinetics, due to the absence of silanols and the hydrolysis / condensation process.

ABSTRACT This work aims the performance of concretes copper slag-added evaluated in fresh state by slump test and in hardened state by compression strength in 7 and 28 days of cement hydration, durability indexes as water absorption and binder efficiency by cement index. In fresh state, the results showed that the samples with copper slag presented lower slump than the reference sample. In hardened state, with 30% of copper slag addition, the compression strength was reduced only by 9% and 8% in comparison with the control series, for 7 and 28 days, receptively. Also, for 28 and 48 days of cement hydration, the water absorption showed lower values in the series with copper slag, indicating a beneficial performance of this waste in the cementitious matrix. Also, the binder efficiency was verified in the work. As the higher the slag in the mixture, lower was the cement consumption and, consequently, higher was the efficiency of the cement, resulting in a low increased in the cement index. The control series, at 28 days of cement hydration, achieved 11 kg•m-3•MPa-1 while the 30% copper slag-added series achieved 12 kg•m-3•MPa-1, which is only 9% higher than series with no consumption of copper slag, indicating a great performance of the copper slag in this cementitious matrix.

ABSTRACT This work deals with the effect in fresh and hardened properties of nano-TiO2 as addition in cement-based mortars. Three commercial nano-TiO2 powders were characterized by laser granulometry, XRD, FRX, zeta potential, BET and SEM. Two cementitious mortars were produced with nano-TiO2, an industrialized and a non-industrialized type; then, these mortars were characterized by flowability, surface roughness, flexural strength and surface fracture. The results showed that the nano-TiO2 addition reduced the flowability in terms of spread on table of the mortars. For surface roughness, in the industrialized mortars, the nanoparticles resulted in a smoother surface, while in the non-industrialized mortars, the nanoparticles formed a rougher surface. For flexural strength, in the non-industrialized mortars, the higher the nanoparticles amount, the higher the strength, while in the industrialized mortars no tendency was verified. In addition, from SEM analysis, it was noted that the fracture of the samples presented a tortuous aspect and growth through the region between cement paste and aggregates.

RESUMO Este artigo buscou verificar a substituição parcial do agregado natural, areia (NA) por agregado de concreto reciclado (RCA) ou agregado leve (LWA) em argamassas, sob a hipótese que agregados pré-molhados produziriam melhoras nas propriedades da argamassa. Para isso, avaliou-se as propriedades das argamassas no estado fresco, como massa específica, teor de ar incorporado, consistência e calor de hidratação, bem como as propriedades no estado endurecido, como massa específica, resistência à compressão e à flexão, e instabilidade dimensional, com 0% e 100% de saturação. Os resultados mostram que as argamassas preparadas com agregado natural (75%) e agregado de concreto reciclado (25%) possuem propriedades semelhantes às argamassas preparadas com apenas agregado natural (100%) e que a pré-molhagem dos agregados não influenciou significativamente as propriedades das argamassas. Assim, constatou-se que, a substituição parcial do agregado natural por agregado de concreto reciclado é uma alternativa viável para a produção de argamassa.

ABSTRACT This paper examines the suitability of partially replacing natural aggregate, sand, (NA) with recycled concrete aggregate (RCA) or lightweight aggregate (LWA) in mortars, under the hypothesis that pre-wetting aggregates would produce improvement in mortar properties. Fresh mortar properties such as density, entrained air content, consistency and heat of hydration, as well as hardened mortar properties such as dry density, compressive and flexural strength, and dimensional instability at 0% and 100% saturation were determined. The results show that mortars made with natural aggregate (75%) and recycled concrete aggregate (25%) have similar properties to mortars made with only natural aggregate (100%) and that pre-wetting the aggregates does not influence the properties of mortars significantly. Therefore, partial replacement with recycled concrete aggregate is a viable alternative for producing mortar.