Most previous investigations of the influence of curing on the durability-related properties of concrete are confused by the influence of factors associated with the assessment procedure or type of test specimen. This paper presents an experimental investigation in which every attempt was made to eliminate factors that would otherwise mask the real influence of curing. The transport based testing regime developed allowed cover thickness specimens to he tested sequentially for sorptivity, vapour diffusion and gas permeability. Mercury intrusion porosimetry and scanning electron microscopy were used to investigate the effects of curing on microstructure. In spite of the inherent variability associated with transport tests, the testing regime was effective in discriminating between the short-term effects of the different curing regimes on concrete transport properties. Generally, the effect of w/c was more important than the effect of curing.

Concrete members were once considered as maintenance free. However, it is clear that some have deteriorated and required maintenance work. This paper attempts to evaluate the factors influencing the total cost of RC members during their service life when structures gradually deteriorate and require maintenance work. The form of deterioration considered here is salt attack, and the repairing method involves restoration of the member to its original cross-section. Total maintenance cost is expressed as present cost based on the coefficient of current price. The main factors calculated in the paper are the deterioration ratio of RC members at the repair stage, the actual interest ratio (including the capital ratio and the price fluctuation ratio), and the cost loss for expected structural failure. Calculation results indicate that the life cylce cost of a structure is greatly affected by these factors (especially the actual interest ratio), and that they have to be decided cautiously.

Recently, a number of cases of damaged concrete structures due to alkali-silica reaction (ASR) and/or chloride-induced steel corrosion have been reported. Some ASR-affected concrete structures have been found to be in a severe condition when ASR expansion has continued for a long period. An inspection for the footing of concrete piers was carried out and fractures at bends in steel bars on the edge of the footing was found. It is considered that the fractures were due to excessive ASR expansion in the concrete. However, mechanism of fracture of steel bar due to excessive ASR expansion is not clear. And as results, a model footing made with reactive aggregate was made and tested. In this study, the relationship between the ASR expansion and the stress of steel bar was investigated. From the experimental results, it was found that thestress at the bends in steel bar due to ASR expansion was attained at the yield point of steel bar or beyond it.

Chloride induced reinforcement corrosion represents an enormous problem world-wide. The exposure conditions for concrete structures in the Persian Gulf area constitute one of the most aggressive climatic environments in the world. In this region, interaction between concrete and environment controls material performance and has resulted in premature deterioration and low durability of concrete structures and is of major concern. This paper reports experience from in-situ investigations on the effects of differ- ent dosages of silica fume and also a surface coating system applied to concrete decks in Persian Gulf area. The specimens were kept in various placement conditions: fully submerged zone, tidal zone, atmospheric zone, underground zone and laboratory conditions. The focus is placed on the abilitv to prevent chloride ingress. Moreover, the test results have been compared to numerical results obtained, using Life-365 model proposed by Thomas and Bentz.

Measurements of relative humidity (RH) by means of wooden sticks of the species Ramin (Gonystylus macrophyllum) have been used in Norway since 1995. The method is especially applicable to concrete with high internal humidity as in structures damaged by Alkali Aggregate Reaction (AAR) or freezing and thawing. Results up to now show that the relative humidity is stable 5 cm from the surface and that ingress of rainwater is an important Source of water in most of the outdoor exposed concrete structures. Correlation tests have shown that wooden sticks still are in good condition and reliable after 7 years continuous use. Measurements on surface treated columns and beams in two structures show that the relative humidity 5-cm from the surface decreased significantly during four years monitoring, which was not the case in untreated concrete. It is concluded that surface treatment is able to reduce the relative humidity in concrete structures exposed to rainwater.