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The use of industrial by-products such as fly ash, blast-furnace slag and ferro-silicon condensed silica fume for making concrete block stripped immediately after molding was investigated in order to save natural resources. Zero-slump concretes containing varying by-products were used. Each concrete block having the size of, 150 x150 x540mm,was manufactured by using an instant-stripping mold. After stripping, the blocks were cured in a steam chamber and a water tank of standard manner. Concrete qualitiessuch as compressive strength, dynamic modulus of elasticity, solidity ratio and surface texture were investigated at given ages. The results of these investigations reveal that there is no great difference between the quality of concretes containing small amounts of by-products and that of the plain concrete. The use of blast-furnace slag is more effective for 28- day strength development. The color of concrete using fly ash or slag is white, and the condensed silica fume substitution is advantageous for steam curing. These by-products may have a useful role in concrete block industry.

Laboratory and field studies were conducted on blast-furnace slag aggregates to establish nationwide material standards and recommended practices. Absorption of air-cooled blast-furnace slag kept in water was 2 to 9 times that of natural gravel, while that under pressure of 2.0 MPa was 1.2 to 4 times that kept in water. Absorption characteristics of air-cooled blast-furnace slag under pressure varied depending on its porosity and pore size distribution. Field studies were conducted on the pumpability of blast-furnace slag aggregate concretes. Air-entrained concretes containing air-cooled and granulated blast-furnace slags, and those containing crushed stone and natural sand were pumped and tested for pumping pressure and properties before and after pump-ing. Concrete with air-cooled blast-furnace slag indicated higher pumping pressure than that with crushed stone due to pressure absorption, while no significant change was found for granulated blast-furnace slag concrete. It is concluded that blast-furnace slag aggregate concrete is pumpable without significant slump-loss when such aggregate does not have excessive absorption, and is properly presoaked in water before the mixing of concrete.

Little basic oxygen slag is used as a portland cement concrete aggregate because of its unsoundness in concrete. However, soundness of basic oxygen furnace slag in concrete appears to largely depend upon the mineralogical and chemical compositions of the slag. Several experiments concerning workability, compressive strength and dimensional stability of concrete made with basic oxygen furnace slag were conducted for investigating the possibility of the use of basic oxygen furnace slag as a concrete aggregate. The concrete made with weathered slag showed a much higher slump for a given mix proportion than natural aggregate concrete and the concrete prepared using unweathered slag. The longer the periods during which the slag used wasplaced outdoors, the lower the compressive strength of the slag concrete. The changes in the mineralogical and chemical compositions and the surface texture of basic oxygen furnace slag particles were determined by X-ray diffraction, differential thermal analysis, SEM and EDAX. The results of these experiments show that reduction in compressive strength and high slumps in the concrete made with the weathered slag aggregates arise from slow hydration of C2S and C2F on and/or near the surface of basic oxygen furnace slag during weathering. It may be concluded that basic oxygen furnace slag can be used as a concrete aggregate if the grading of fine slag aggregates coarsened by its slow hydration is improved by adding river sand so as to obtain a workable concrete.

The investigation was carried out by using different amounts of blast furnace slag in blended cements. The slag content of the binder varied from 0 % to 100 % of the weight of the cement. The cement-aggregate ratio in the experiments was 1:15 and the water-cement + slag ratio was 5.9. The compressive strength of the mining-fill-concrete was determined at the age of 28, 91 and 182 days. The specimens were cured at both +8 OC and a t +20 oC. The optimum cement content in the binder when granulated slag was used, was 10 % at both temperatures. Using pelletized slag, the optimum cement content in binding agent was, at +8 oC, 30 %, and at +20 oC, 10 % of the weight of blended cement. At lower temperatures the finer slag gave higher compressive strength results while at the temperature of 20 ‘C no increase in compressive strength was observed.

Methods of production, placement and strength requirements of mine fill are briefly described. The chemical composition and details of the mineralogical nature of a particular quenched copper reverberatory furnace slag, successfully used in fill operations at Mount Isa Mine, Queensland, Australia are discussed. Experimental work on slag reactivity in the presence of Ca(OH)2 is described, and includes studies on the heat of hydration, non-evaporable water and x-ray intensity variations. The reaction product, which is also observed in the presence of hydrating portland cement appears to be a 7.34 & hydrate. Information on hydration characteristics may eventually allow advantageous modifications to be made to the present compositions of the fill material.