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In this study, the effect of curing and drying on the strength and absorption of plain and pozzolanic cement concretes were evaluated. The specimens were cured for 1,3,7,14, 28 and 60 days. At each testing period, specimens were oven dried at 70 degrees C for 2, 8, 12 and 24 hours. The effect of curing and drying on the absorption capacity of concrete specimens was evaluated by measuring 48-hour absorption and volume of permeable voids. The specimens were also tested for compressive strength and moisture content. The results show an increase in the compressive strength in plain and pozzolanic cement concretes with increased curing and drying time. The absorption of these concretes decreased with time of curing and increased with drying period. The absorption of both fly-ash and silica-fume cement concrete specimens decreased significantly after three to seven days of curing. While the absorption of plain concrete specimens were effected significantly by drying period, no significant period was observed, especially after seven days of curing. The volume o permeable voids also decreased with curing. The highest reduction in the absorption and volume of voids was observed in the fly-ash cement concrete specimens.

A series of nine large concrete blocks (750 mm cube), stored outside on an industrial site at the Appleby Frodingham works at Scunthrope in N.E. England were assessed at 7-8 months, 30 months and 7.5 and 10.5 years of age. The concrete contained a normal total cementitious content of 390kg/m and had different levels of ground granulated blast furnace slag in the range 0, 30, 50 and 70% by weight as replacement material for portland cement. Some of the concretes were prepared using gravel and others with crushed limestone as aggregate. The quality and performance of these concretes were determined at each age by testing drilled cores taken from the side face of the blocks, partly protected form driving rain. The assessment involved early hear release data; measurements of the depth of carbonation; oxygen permeability and compressive strength. Comparisons were made between the different concretes on the basis of their comentitous slag content an aggregate types. The results showed that concretes containing 100% normal portland cement or 50% slag have hardly carbonated, although carbonation had progressed to 5 to 6 mm at 2.5 years where 70% slag was used, but there was little change thereafter. Gas permeability decreased slightly as the slag replacement levels were reduced from 70% to 50% and the coefficient of oxygen permeability (ko) values for the inner concrete were in the range .5 to 9 by 10 to the -18th. M2 by 2.5 years which indicated that all concretes had low permeability. Impressive compressive strength gains were realize with time for the slag cement concretes which at 7.5 years were in the rang 82.5 to 105 MPa compared with the plain portland cement concrete at 67.5 MPa, clearly demonstrating the beneficial long term effect of slag on strength development. Benefits were also derived form the use of water reducing admixtures and from using crushed limestone as aggregate. These are discussed in relation to the longer-term performance of the concretes at 10.5 years.

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.

Pozzolanic cements with 50% fly ash, and composite cements with 25% fly ash and 25% ground granulated blastfurnace slag were produced to manufacture high performance concretes. These binders are in agreement with the European standard (EN 197/1) for cements type IV/B and V/A, respectively. Unground and ground fly ash was used for pozolanic and composite cements. Ground slag was used for composite cements. Eight different blended cements were produced and characterized by strength measurements on standard mortar bars. High performance concrete mixtures were all manufactured with a water-to cementitious material ratio as low as .32, a portland cement factor of 235 kg/m3, and a fly ash or slag plus fly ash content of 235 kg/m3. A naphthalene-based superplasticizer was used to produce flowing concretes with a slump in the range of 190-220 mm. A slightly higher dosage of superplasticizer was needed to compensate the slump reduction caused by the fineness increase of the blended cements. Cube concrete specimens were cured at 5 degrees C and 20 degrees C. Compressive strength was measured at 3, 7, 28, and 90 days. The 28-day compressive strength at 20 degrees C was in the range of 60-80 MPa. Early compressive strength (at 3 days) was as high as 30-40 MPa even at the lower curing temperature (5 degree C). Carbonation and chloride penetration tests were carried out to assess the influence of the cement fineness on the durability behavior. In general, the durability of these concretes in terms of carbonation and chloride penetration is excellent. However, there is no significant improvement related to higher fineness of cementitious materials.

For comparing the relative performance of supplementary cementing materials (SCM) with regard to concrete durability, the concept of efficiency factor may be used. The efficiency factor (k-value) is defined as the part of the SCM in an SCM-concrete which can be considered as equivalent to portland cement. In this work, three typical SCM were studied: a silica fume, a low-calcium fly ash and a high-calcium fly ash. Accelerated carbonation and chloride penetration tests were performed. With regard to 28-day compressive strengths, penetration test were performed. With regard to 28-day compressive strengths, k-values of 3, .5, and 1 for silica fume, low-calcium fly ash, and high-calcium fly ash, respectively, were estimated. Mathematical models describing the carbonation propagation and chloride intrusion were applied to estimate the durability k-values. Higher k-values with respect to chloride penetration were found, indicating that SCM reduce the chloride permeability more effectively than they improve the compressive strength. On the contrary, with respect to carbonation depth, k-values of .3, .5, and .7 for silica fume, low-calcium fly ash and high-calcium fly ash, respectively, were estimated. A theoretical explanation of these results is also given.