Presents field data of up to 8 years on chloride penetration into concrete and consequent steel corrosion in a test structure exposed to an aggressive environment favoring rapid transportation of chloride ions into concrete. The structure consisted of reinforced concrete beams, slabs, and columns. Two types of concrete, one without salt and the other containing 0.5 percent NaCl by weight of concrete, were used in the construction. Parts of the structure were left exposed and unprotected, while the other half was protected with a highly elastic acrylic rubber coating previously subjected to intensive examination. The chloride contents in the structural members were determined regularly over a period of 8 years. In addition, the influence of the coating and the different salt concentrations on corrosion of the embedded steel were evaluated. It is shown that the acrylic rubber coating can almost totally protect the concrete from chloride penetration and consequent steel corrosion and maintain this protective effect for many years.

Reduction in the useful service life of bridge decks in the USA and Europe and reinforced concrete structures in tropical countries due to reinforcement corrosion has been of major concern to the engineering community throughout the world. In both situations, the presence of chloride ions in sufficient quantities is the primary cause of the initiation of reinforcement corrosion. Chlorides are contributed by deicer salts in the bridge structures, while soils and groundwater charged with high concentrations of salts in tropical countries contribute significant quantities of chloride ions. In the latter regions, the low precipitation and high evaporation rates result in high salinities in the soil and groundwater. In this investigation, cement paste, mortar, and reinforced concrete specimens made with two plain cements and three blended cements were placed in a 15.7 CL - (26 percent NaCl) solution. The performance of the plain and blended cements in resisting reinforcement corrosion was evaluated by monitoring the corrosion activity at regular intervals. The effect of high concentrations of chloride salts on the physical properties was monitored by measuring compressive strength reduction. Results indicate retrogression of strength in blended cement mortar specimens placed in the chloride solutions compared to those cured in potable water. This behavior was more pronounced in the silica fume cement. However, the resistance to reinforcement corrosion of the blended cements, particularly silica fume cement, was better than the plain cements.

Despite the excellent resistance of high-performance (HP) concretes in the presence of aggressive agents, instances of application have shown that the microstructure of the concrete surface can be greatly disturbed by the curing method, thereby compromising durability on the part covering the reinforcement. Paper presents results of a study on three concrete design mixes (one reference concrete and two HP concretes with and without silica fume), each subjected to three curing methods and three durability tests. Results on carbonation, variation in free lime, and microcracking indicate that HP concrete with silica fume is more sensitive to the curing method than the reference concrete or concrete without silica fume, as evidenced by increased carbonation and a larger reduction in alkalinity. The study of microcracking in the various concretes showed that desiccation causes more microcracking in the HP concrete with silica fume than in the HP concrete without silica fume. Results of microstructural inspection and physical and chemical tests explain these variations in mechanical properties and carbonation behavior of various concretes, depending on the curing method.

The object of this publication is to determine the relationship between the cracking in loaded reinforced concrete and the corrosion of embedded steel. Paper deals with the synthesis carried out for 7 years on reinforced concrete elements kept in a loading state, in a confined salt fog. The test specimens are 3-m-long beams, which is a sufficient size to be representative of the actual operating conditions of the reinforced concrete structures. Steel electrode potential measurements are performed on all beams kept in a salt fog environment to evaluate the state of the steel corrosion by a nondestructive way. The development of damage in concrete specimens is monitored by means of a scanning electronic microscope. The bending of the beams leads to the development of cracks that are neither preceded nor accompanied by microcracks, but the cement paste-aggregate interfaces are damaged in the tensile areas. On the other hand, the corrosion of steel leads to a secondary cracking that is branched out. Chloride penetration in concrete is obtained by measuring out free chlorides and bound chlorides in different samples extracted from different locations of the beams. Then, several parameters are studied, such as the effect of the location of the beam in the storage enclosure, the loading state of the beam area, and the intensity of the mechanical stress applied. Moreover, a relation is established between the rate of free chlorides measured and the embedded steel corrosion. The rate of corrosion is influenced by the concrete cover thickness even in the presence of cracks.

To evaluate repaired method of damaged concrete, the Japan Concrete Institute had set up the research committee on Repair of Concrete Structures in 1990. The research committee consists of three task groups, marine exposure test group, state-of-the-art report task group, and theoretical analysis task group. The effect of coating, repair materials, and repair method on corrosion of reinforcement embedded in the concrete is evaluated by both experimental and theoretical manner in the committee. In this paper, the results of marine exposure tests up to 18 months are reported. The chloride-damage simulated specimens are repaired by 26 companies using different materials and methods, and the same type of nine specimens are also prepared with different types of repair materials and different thickness of coating to evaluate the effect of these factors. These specimens are exposed on the Izu coast in Shizuoka, Japan. Brightness, color change, and cracks on coating, and electrochemical properties of reinforcements are measured at the ages of 6,12, and 18 months. Cracks and corrosion stains are observed for specimens without coatings, independent of the existence of internal chloride, while there are no cracks and corrosion stains on the coated specimens. Appearance of coating on the specimens depends on the type of the coating applied. Also swelling, peeling, and cracking of the coating are observed for several specimens. The electrochemical properties of reinforcement depend on the type of coating, and a new method to evaluate deterioration of coating using an electrochemical method is proposed.