A cement mix based on an inorganic hydraulic cement, for example, Portland Cement, an air-cooled blast furnace slag and silica fume produces concretes having strength characteristics superior to those achieved by the cement alone; furthermore this cement mix is superior to a corresponding mix based on the inorganic hydraulic cement, and the air-cooled slag without the silica fume, and to a corresponding mix based on the cement and silica fume without the slag; additionally a cost saving in the expensive Portland Cement is achieved by use of the air-cooled slag which is a waste material and cheaper than granulated or pelletized slag.
Embodiments of the invention provide a slag manufactured aggregate suitable for inclusion in one or more of concrete, precast concrete, cellular concrete, or precast cellular concrete. Concretes, precast concretes, cellular concretes, and precast cellular concretes comprising the slag manufactured aggregate are also included in embodiments of the invention. Methods of making the foregoing aggregates and concretes are also included herein.
A cement admixture of a low environmental load type, capable of reducing hexavalent chromium, having a small slump loss or heat of hydration, hardly neutralized and capable of suppressing autogenous shrinkage to a low level; a cement composition; and cement concrete employing it, are presented. The cement admixture comprises a slowly cooled slag powder which contains melilite as the main component and which has a carbon dioxide absorption of at least 2%, has a CO.sub.2 absorption of at least 2%, has a loss on ignition of at most 5%, contains at least 0.5% of sulfur present as non-sulfuric acid form sulfur and/or has a concentration of non-sulfuric acid form sulfur to elute, of at least 100 mg/l, and further, preferably, has a degree of vitrification of at most 30%, a melilite lattice constant a of from 7.73 to 7.82 and/or a Blaine specific surface area of at least 4,000 cm.sup.2/g.
A method for the production of cement clinker comprises the introduction of vitrified slag into the feedstock stream prior to the clinkering zone. The addition of vitrified slag can increase the clinker output rates and/or reduce the energy requirements for maintaining the kiln temperatures. In one embodiment, the vitrified slag is a vitrified blast furnace slag.
Cementitious compositions and methods for making the compositions wherein the compositions include high volume of mineral admixtures such as fly ash and blast-furnace slag in combination with rice hull ash. In one embodiment, the cementitious composition is a blend of hydraulic cement, rice hull ash and a mineral addition selected from fly ash and blast-furnace slag. The cementitious compositions can advantageously have high early and 28-day compressive strength and a very low permeability rating.
The present invention relates to admixtures production and to a method of application of the admixtures in cement and concrete technology. The method allows production of high-strength and high durable cement based systems, as well as cement systems with specially designed properties of cheap high-volume mineral admixture cements.
