In the study reported in this paper. the permeability of normal portland cement (PC) and fly ash (FA) concretes containing 15%. 30% and 45% FA were investigated. These were compared on an equal 28 day strength basis (and therefore had increasing binder contents and reducing W/B with increasing FA content at a given design strength). A further series of FA concretes (45%), combined with two active early strength cements to overcoming low early strength were also considered. The results followed expected behaviour in terms of strength/permeability relationships. It was also found that the permeabilities of FA concretes were lower than those of PC concrete. with greater differences at increasing FA level. The permeability of all concretes cured in water was significantly lower than those of concrete cured in air, but the differences reduced with increasing FA level. suggesting that this concrete may be less sensitive to limited moist curing. Long-term curing in water lead to reductions in permeability for all concretes, while that in ai r generally lead to slight increases. Comparison between pemeabilities of high FA content concretes indicated similar performance between these. although the exact ranking varied slightly depending on the curin g conditions. It was found that the performance of high FA concrete was better than PC concrete under a wide range of temperature and moisture curing conditions, but this may be reversed under low temperature, cold curing conditions. A ranking of the FA concretes to illustrate their potential durability is provided.

After damage due to reinforcement corrosion in carbonated concrete, repair principle W - limiting the water content of concrete - as specified in the Draft Recommandation for Repair Strategies for Concrete Structures Damaged by Reinforcement Corrosion (l), can be applied in the repair of concrete compo-nents. The repair principle involves sealing the concrete surface with a suitable surface protection system after exchanging and reprofiling the damaged concrete areas. As a result the water content in the concrete shall be reduced to such an extent as to bring the corrosion process of the reinforcement to a standstill. The effectiveness of surface coatings as corrosion protection systems has been investigated on carbonated concrete specimens using the simultaneous measurement of corrosion rates and electrolytic concrete resistivities.

Durability issues about fiber reinforced concrete (FRC) have concerned users because of the material properties of the fiber and the subsequent performance of the composite concrete. Users’ concerns have also been addressed by defining durability issues in the specific FRC application. Recently developed, polyolefin FRC provides concerned users the benefits of combining the fiber material from synthetic fibers with the significantly improved concrete properties obtained with steel fibers. Polyolefin FRC was used for construction of a thin bridge deck overlay, a Jersey barrier, a full depth bridge deck slab, whitetopping (concrete on scarified asphalt pavement), and full depth pavement. Data documenting durability evaluations is presented in this paper. Extensive measurements of cracking in plain and FRC concrete Jersey barriers were made to predict the comparative durability. The calculated fatigue life had shown that bridge decks and pavement built with FRC would last longer than those built with plain concrete. Due to the 1993 development and introduction of polyolefin FRC, the long term durability by in-service case studies can only be predicted. These predictions are based on laboratory and field evaluations comparing FRC and plain concrete built in similar projects.

This paper presents extensive long-term data on chloride penetration into unprotected and protected members of a reinforced concrete structure exposed to an aggressive salt-laden environment. The test results up to 11 years of exposure show that chlorides penetrate very rapidly into the concrete from an early stage, and this penetration increases with time. There was a visible peaking of chloride concentration in the vicinity of the location of the reinforcing bars. Structural members protected with the acrylic rubber coating showed an almost total absence of penetration of chlorides throughout the exposure period, and the coating maintains long-term durability of RC structures under marine environment. The accumulated chloride ions in concrete become important for the durability of reinforced concrete and these have been calculated from the distributions of chlorides in relation to the exposure period. Analytical evaluation shows that the accumulated chlorides are expressed by a model represented by an equation with coefficients,where the coefficients are closely related to environmental conditions and characteristics of concrete.

The non-linear diffusion equation has been successfully applied to water movement but only during the drying process. As a model which can be applied to both drying and wetting processes, capillary flow is considered to be worth examining as one possibility in order to establish a universal model. In the first step, one-dimensional water movement within mortar was studied both analytically and experimentally. A model consisting of capillaries with various sizes was adopted and water movement was analyzed by assuming that it was caused by capillary action. A good correlation w a s obtained between numerical results and experimental data. Useful information was also obtained from the analysis concerning the behavior of moving water within mortar.