SP91 This contains 78 symposium papers, bringing together the expertise of representatives from industry, government and universities. These volumes present the latest advances in the use of fly ash, silica fume, slag and natural pozzolans in concrete. New technologies are explored to provide ways in which these valuable mineral by-products can best be used to conserve both resources and energy. Case studies include: the effect of fly ash on physical properties of concrete; evaluation of kiln dust in concrete; effect of condensed silica fume on the strength development of concrete, and the influence of slag cement on the water sorptivity of concrete.

The effect of condensed silica fume on the strength deve-lopment in concrete was studied by replacement of 0, 5,10, and 20% cement by silica fume. No admixtures was used. For all the mixes,about the same strength was obtained up to 7 days. From then on,the mixes with silica fume produced an increased strength development compared to that of pure cement. At a partial replacement of cement by 20%, the compressive strength at 28 and 90 days was increased by 43 and 55%, respectively, with respect to the strength at 7 days.

The aim of the paper is to determine to what degree the strength of mortar and concrete is affected by the way in which blast furnace granulated slag is added. The influence of the fo the compressive strength of imentally: 1) Intergrinding of (cl 2) Separate grinding of ed by dry mixing bef 3) Separate grinding of lowing methods of adding the slag on mortar and concrete was studied exper-nker + gypsum) and slag. clinker + gypsum) and of slag, follow-re batching. (clinker + gypsum) and of slag and separate batching into the mixer. The variables considered for this study were: slag/(slag + clinker) ratio in the cementitious material (0, 0.342, 0.50 and 0.658), age of test (3, 7, 28, 90, 180 and 360 days) and fineness of cementitious material (330, 360 and 400 m2/kg). Rilem -Cemburepu mortar prismsand cylinders of concrete having 19 mm maximun size of aggregate were tested for strength. The results were analysed statistically, and it was found that the differences observed between the various methods were generally non-significant.

Although abundant data are available on early-age properties of blended cement concretes, relatively little information has been published on the long-term durability of blended cement concretes in service. The paper is a summary of an investigation of over two hundred structures in Australia. Some of these have service lives in excess of twenty years. Cored materials from some of the structures are described, and petrological and mineralogical examination allow conclusions on the efficacy hydration processes under field curing to be made. Porosity and permeability is discussed. Carbonation and corrosion effects on long-term durability are considered by the examination of data obtained from in situ concretes. The interactions between cement content and water: cement ratio on carbonation rate is discussed, and data from concretes both from in service and laboratory mixes are considered. Cracking is the predominant defect observed on most of the examined concrete surfaces and the role of pozzolans on elastic deformations, creep and shrinkage of concrete in structures is discussed. Data suggest that, for those structures studied, the long-term durability of blended cement concretes is at least the equal of ordinary portland cement concretes under service conditions.

Drying shrinkage and creep of concrete with condensed silica fume are experimentally analyzed and compared with those of concrete without condensed silica fume. Specimens for drying shrinkage tests and creep tests are manufactured by two kind of curing methods, namely, standard and autoclave curing, and are measured in air at 20°C and 50% R.H.. Some specimens are measured in water at 20°C. Measurements for volume change and weight change are continued for 800 days. Within the scope of this research the following conclusions may be drawn: (1) Drying shrinkage of concrete with condensed silica fume is lower than that of concrete without condensed silica fume at the same water-cement ratio. But in case of standard curing, the values of drying shrinkage per unit cement paste volume are roughly the same for both concretes with and without condensed silica fume at the same compressive strength; while in case of autoclave curing, the values are higher for concrete with condensed silica fume at the same compressive strength. (2) Creep in air is high for concrete with condensed silica fume in both cases of standard curing and autoclave curing. Creep in water is high for concrete with condensed silica fume in case of standard curing, but creep in water is low for concrete with condensed silica fume in case of autoclave curing.