Nondestructive test methods (NDT) have been used to evaluate concrete strength using curves that correlate the NDT measurements with the compressive strength of concrete established by a laboratory testing program. Usually the parameters that affect these curves are the water-cement ratio, the aggregate type, the maximum aggregate size, and the cement type of the concrete. This work presents a study on the correlations between the compressive strength of concrete and measurements from three nondestructive test methods: ultrasonic pulse velocity, probe penetration, and rebound hammer. The study included 30 different concrete mixtures made with materials used in the city of Rio de Janeiro. The compressive strength and nondestructive tests were carried out at ages of 3, 7, 14, 28, and 90 days. Analysis of variance (ANOVA) was used to investigate the importance of different parameters on the results of the compressive strength and nondestructive tests. Simple and multiple regression analyses of the obtained results lead to the proposed expressions for evaluating the compressive strength of concretes used in Rio de Janeiro from measurements using one or two nondestructive tests.

This study was aimed at evaluating an industrial production system of rice husk ash (RHA) with low carbon level. The system, developed in partnership with a local industry, consists of a continuously rotating furnace that can reduce the carbon level of residual RHA through re-burning. Different temperature bands, retention time in the furnace interior, and grinding degree were studied. The results indicate the feasibility of producing a material with reduced carbon levels, which is highly reactive and can be commercially used in the production of high performance concrete.

The use of the maturity approach has been increasing in various fields of concrete construction. In order to estimate the development of a mechanical property of the concrete mixture reliably, it is necessary to previously determine the apparent activation energy of the mixture. This thermal sensitivity index is a function of several parameters including cement type, presence of admixtures, and w/c. This study investigates the influence of silica fume on the apparent activation energy of high-performance concrete mixtures. Following the procedure in ASTM C 1074, various mortar mixtures were prepared with 6 different types of Brazilian cements (CP-I-S, CP-II¬F-32, CP-II-Z-32, CP-III, CP-IV-RS e CP-V-ARI), and with addition of silica fume at two levels (8% and 16% of cement mass). The results indicate that the presence of silica fume increases the value of the apparent activation energy.

The paper describes the results of research on the properties of concrete with the replacement of part of portland cement with bottom ash from municipal solid waste incinerators (MSWI). Results showed that MSWI bottom ash is potentially attractive as mineral addition for the production of concrete, provided that the risk of entrapment of hydrogen bubbles produced by corrosion of aluminium metallic particles in the fresh concrete is prevented. This could be achieved by wet grinding the bottom ash so that reactions leading to gas development could start within the slurry. A great variability was observed in the time required to exhaust the hydrogen gas production; a key factor for this variability was found in the pH of the slurry. A modest amount of cement added in slurry could increase the pH, reduce the time required to exhaust hydrogen evolution and allow manufacturing of quality concrete suitable for aggressive chloride bearing environments.

The south part of Japan is located in the subtropics. Therefore, steel corrosion in concrete in this region easily tends to initiate and progress due to chloride ion ingress into concrete from the seawater. Under this environment, in order to enhance the durability of reinforced concrete structures in which sufficient concrete cover depth can not be secured due to some restrictions, it is very effective to apply adequate surface coating materials on the concrete surface at early age of exposure. To study the durability of concrete with various surface coating materials under marine environment in the subtropics, exposure test was carried out in the south part of Japan. Various tests such as bond strength of surface coating materials, chloride ion content in concrete and corrosion evaluation of steel bar in concrete were carried out after 15 years of exposure. These results indicate that these surface coating materials are very effective in enhancing the durability of concrete under marine environment. This protection against chloride attack was well maintained for 15 years of exposure to a marine environment.