The lack of natural fine aggregate in Japan is serious because the commitment to protect the natural environment is increasing. Many concrete engineers are eager to find fine aggregate sources other than the traditional river and sea sand. Copper slag fine aggregate is expected to be one of the alternatives although the location where the copper slag is available is limited. In this paper, some characteristics of concrete with copper slag will be clarified. The carbonated thickness, resistance to freezing and thawing, thermal resistance, shrinkage strain, creep and setting time have been examined. The strength, slump and durability of concrete with copper slag are not inferior to those of normal concrete. However, copper slag sometimes delays the setting time of concrete even if it produced at the same refinery. The delay of setting time is more than one week in some cases although the durability in concrete is not affected by it. The main reason will be determined and the solution will be given in this paper.

The corrosion resistance of cracked concrete specimens reinforced with bare, stainless, or galvanized steel plates are compared with the corrosion behavior of bare steel reinforcement embedded in concrete specimens coated with a flexible polymer--cement based mortar both before and after specimen cracking. The results in terms of corrosion electrochemical potential and short-circuit electric current measured on the different steel reinforcements are also compared with those related to galvanized reinforcement embedded in hydrophobic concrete specimens. Reinforced concrete specimens were manufactured for each protection method considered and cured before exposure to the test environments. Some specimens were previously cracked by applying flexural stress. The specimens were exposed to increasingly aggressive environments; forty days of full immersion in a 3.5% NaCl solution, simulating a marine environment, were followed by five months of wet-dry cycles using a 10% NaCl solution, simulating a bridge deck treated with deicing salts. The results for the full immersion condition show that negligible corrosion rates were detected in all the cracked specimens, except those treated with the flexible polymer-cement mortar before specimen cracking and the hydrophobic concrete specimens. On the other hand, for the cracked specimens exposed to wet-dry cycles, high corrosion rates were measured for both bare and galvanized steel reinforcement. This was in contrast to the constantly good behavior of stainless steel reinforcement and also of the galvanized steel reinforcement embedded in the hydrophobic concrete.

The effect of a range of curing regimes on the resistance to chloride penetration of concretes has been studied. Concretes with two binder systems namely normal portland cement (NPC) and a 30% fly ash blend (FA) were subjected to four different curings. They include 1-day sealed, 7-day sealed, 7-day wet and a simulated steam curing. Subsequent to each curing regime, the samples of grade 40 concretes were air cured I standard laboratory conditions until the age of 28-day before exposure to 15 cycles and 100 cycles of immersion in 3% NaCl solution and drying. Resistance to chloride ion penetration was evaluated by examining both the chloride profile and diffusion coefficient (calculated by Fick's second law). Thus the role of curing in governing the resistance of concrete to chloride ion penetration was established. NPC concrete was found to be more sensitive to the type of cuing than the fly ash concrete. NPC concrete subjected to 1-day and 7-day sealed curing resulted in lower chloride penetration resistance than the 7-day wet curing. However, the fly ash concrete showed remarkable tolerance to the lack of moist curing giving very similar performance in both 1-day and 7-day sealed curing as the 7-day wet curing. Steam curing resulted in poorer resistance t chloride penetration for both concretes. For each type of curing, the fly ash concretes gave significantly better resistance to chloride penetration than the NPC concrete (of similar grade). Effect of curing on sorptivity and volume of permeable voids (Vpv) of concretes of grades 20, 40 and 50 were also studied. Both sorptivity and Vpv were found to be influenced by the type of curing for both binders. Vpv was found to show correlation to the long-term chloride penetration resistance of the concrete. No such correlation was found for sorptivity values.

The development of a curing time estimator is described: it is based upon an existing model of the microstructure and porosity gradients in the cover concrete that correlates well with relevant hydration and pore structure measurements. The same model also yields capillary porosities that correlate with measurements of compressive strength and water absorption rate. The objective is to provide a single method to estimate curing times for CEM I and CEM II (portland and portland/fly ash) concretes in a wide range of climatic conditions and achieve a consistent, well-defined measure of cover concrete performance. New hydration and pore structure measurements are briefly reviewed in relation to the existing model of microstructure and porosity in cover concrete. Recent developments regarding European standards for curing and concrete durability are considered. A criterion of capillary porosity in the matrix of cover concrete is used to unify the durability-related effects of curing period, cement type, water/binder and climatic conditions. The initial input to the estimator is the cement type to be employed. The nest input is a maximum water/binder, as necessary to ensure durability under the expected exposure conditions; this automatically sets a target capillary porosity in the cover concrete, based upon recent curing period recommendations from European standards committees. Subsequent inputs define the climatic conditions in terms of exposure capillary porosities in the cover concrete for a wide range of curing periods so that a period can be chosen without exceeding the target porosity. Capillary porosities for reduced water/binders, 95and 90% of the input value, are also tabulated to illustrate the reductions in curing period that are possible with these higher concrete qualities. Examples are given to illustrate the effect of each of the eight inputs; water/binder, exposure relative humidity and cement type are the most influential. It is evident that in many cases control of cover concrete performance via curing options is limited relative to the control offered via small changes in the concrete mix proportions of alternative cements.

The results presented in this paper form part of an investigation into the optimisation of ternary blend systems based on normal portland cement, fly ash and silica fume, for the development of high performance concrete. Chloride permeability and oxygen permeability values at the age of 7, 28, 90 and 180 days of concrete containing portland cement, fly ash and silica fume are reported. Fly ash, up to 40%, and silica fume, up to 15%, were incorporated as partial cement replacements for the preparation of various combinations of ternary blended systems. A water-binder ratio of .27 was used for the main group of mixtures. Two other water-binder ratios, .40and .50 were used with selected concrete mixtures to show the effect of this parameter. Based on the experimentally obtained results, prediction models were developed. These enabled the establishment of isoresponse contours showing the interaction between the various parameters investigated.