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This paper describes a study of the full exploitation of the inherent hydraulic behavior of granulated blast-furnace slag. An attempt was made by laboratory tests and by actual concrete practices to improve the properties of conventional slag cements and develop a high quality binder. Granulated blast-furnace slag pulverized and classified by an industrial mill (Blaine fineness 850 m2/kg> was mixed with ordinary portland cement and semi-crushed granulated blast-furnace slag sand aggregate with the addition of a high-range water-reducing admixture. Workability, strength, and resistance to freezing and thawing cycles, mechanical abrasion and chemical attacks were determined. Microstructures were measured by SEM, and mercury intrusion and nitrogen adsorption porosimetries. Major findings of the research include: 1 . Workable mixtures with ultra-highly pulverized blast-furnace slag can be obtained with the addition of high-range water-reducing admixtures (HRWRA) and have less bleeding. 2. Use of ultra-highly pulverized blast-furnace slag is effective in getting a very dense and uniform structure of the hydrated paste and shows superior characteristics with high-strength concrete having more than 100 MPa, as compared to the straight portland cement high-strength concrete. 3. Densification and reduced calcium hydroxide caused by the hydration of slag remarkably improve the resistance to acid and sulfate attack as well as other characters.

This paper describes how some properties of high compressive- strength concrete (60 -8OMPa) can be improved by the use of very fine ground granulated blast-furnace slag as a partial replacement fqr portland cement. The fineness of very fine ground slag is 715 m/k g 2 (Blaine) made from classifying ordinary ground slag (364 m /kg Blaine) by the air separator. Concrete mixtures containing very fine ground slag were tested varying the substitution ratio of slag to total content of cementitious materials (slag + portland cement) 10, 40,3 and 70 percent. The total cementitious materials were 500 kg/m and 400 kg/m and the water-cement ratios (W/C) were 0.30 and 0.325 respectively. Concrete mixtures containing other materials, such as ordinary ground slag and silica fume, were also tested. The properties of the concrete investigated were compressive strength (at the ages of 7, 28, 56, and 91 days), resistance to freezing and thawing, permeability, and resistance to chloride penetration. A comparison of these properties was made between very fine ground slag and other materials similarly used. It was found that high compressive strength could be obtained with the improvement of permeability, resistance to chloride penetration, and other properties, even if very fine ground slag was substituted for cement at a replacement level of 70 %.

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.

A second source of ground granulated blast-furnace slag ('slag') has become available in the UK, from Purfleet in South East England. The Purfleet slag has a slightly higher lime-silica ratio (c/s) and calcium content than the initial source at Scunthorpe. The slag has a potentially higher rate of hydration because of its chemical composition, but as a consequence can contain up to 30% by volume of merwinite crystallites included within its glass structure. The presence of these crystallites has been found to increase further the reactivity of the slag glass. Scanning election microscope (SEM) studies of concrete containing the slag have confirmed that the glassy particles containing merwinitic crystallites are more reactive than pure glass particles, also that an adequate supply of unreacted glass remains even in mature concrete. Testing of this merwinitic slag has shown no factors disadvantageous to slag reaction or performance and has confirmed that, when blended in appropriate proportions with Portland cement, it can for example, increase sulphate resistance and reduce expansion due to alkali-silica reaction. The results of the investigations reported are supported by a brief review of published literature which confirms that slag performance cannot be directly related to absolute glass content.

Diffusion of sodium chloride, cesium chloride and simulated sea water solutions across and into cement pastes and mortars blended with granulated blast furnace slag has been studied. The temperatures of hydration and diffusion were varied between 23and 6O C. Phase chemistry, depth profiles of chloride, and ion migration measurements across paste membranes were used to follow reaction and diffusion of the salt solutions. It was observed that cement mortars containing the slag showed lower penetration depths of Cl- compared to the control portland cement mortars at normal or moderate temperatures. The diffusion of cesium or chloride ions was retarded significantly through the use of slag blending in pastes. The porosity was lower and pore structure was finer in the case of the blended cement, which is considered to be the primary reason for the beneficial effect on diffusion. Phase chemistry studies of blended slag-cement mortars indicated an absence of detrimental reaction products such as gypsum or brucite after exposure, but the presence of Friedel's salt (tetracalcium aluminate dichloride-lo-hydrate) was detected. Comparisons are also made with blends with fly ash, which also showed relatively favorable effects. The electronegative nature of portland cement was elucidated by Cs+ and Cl- migration in pastes.