Stabilization of extremely lightweight aggregate concrete
First Claim
1. Method of producing a monolithic lightweight aggregate concrete of a density of 700-1200 Kg/m3 in fully dried condition composed of lightweight cement mortar including hydraulic cement, sand, fine and extremely lightweight particles, air bubbles and water mixed together with coarse lightweight aggregate,characterized by the fact thatthe low density of the cement mortar of the lightweight aggregate concrete is constituted by replacing sand at least partly by an equivalent volume of small air bubbles with a diameter in the range of approximately from 20 to 500 micrometers so that the volume of air bubbles is in the range of 5 to 30% of the volume of cement mortar and expanded organic and inorganic aggregate of particle density less than 200 Kg/m3 and of a size approximately from 0.2 to 2 mm and a volume from 5-20% of the volume of cement mortar in such a way that the total particle volume of the cement mortar constitutes nearly a continuous size distribution, the stability is increased and the homogenity is maintained of the fresh cement mortar and concrete by adding polymer microparticles and equivalent organic microparticles in the amount of 0.1-5.0% of the cement weight,said polymer microparticles consisting of a mixture of at least two different types,a first type consisting of synthetic polymer particles having a diameter of 0.1-1.0 micrometers on the surface of which an anionic or a combination of anionic-nonionic calcium stable surfactants have been adsorbed to an amount of 0.1-5.0% by weight of the synthetic polymer, anda second type consisting of natural or synthetic polymer microparticles having a diameter of 0.5-10 micrometers on the surface of which an anionic or anionic-nonionic calcium destabilizable combination of surfactants have been adsorbed to an amount of 0.1-5.0% by weight of the natural or synthetic polymer, wherein the weight ratio between the second type microparticles and the first type microparticles is in the range from 1:
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Abstract
Method of producing monolithic mainly cementbound concrete in the density range of 650-1300 kg/m3, preferably of 800-1200 kg m3 with substantially good placing properties both for building in situ and prefabrication. The concrete consists of cement mortar with an air-void volume of 7-18% of the total concrete volume and aggregate consisting of lightweight organic or inorganic material. The smaller particles of the aggregate should be spherical, exceptionally lightweight, hydrophobic and durable against deformation in order to reduce the water content without changing the consistency of the concrete. The production of concrete is based on the aggregate having a continuous distribution of particle size within which the particle density decreases with decreased particle size, that during mixing small as well as big air-voids are created with strengthened and thickened bubble walls, that the thixotropy of the cement paste is strengthened and that air bubbles are replaced with an equivalent volume of sand particles in excess of those which are needed for the creation of air bubbles. The effects are achieved with multifunctional polymer microparticles on which different surfactant systems have been adsorbed. Air bubbles with their thickened walls as well as the most lightweight aggregate particles reduce the difference in density between the continuous medium and the air bubbles - aggregate particles.
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Citations
8 Claims
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1. Method of producing a monolithic lightweight aggregate concrete of a density of 700-1200 Kg/m3 in fully dried condition composed of lightweight cement mortar including hydraulic cement, sand, fine and extremely lightweight particles, air bubbles and water mixed together with coarse lightweight aggregate,
characterized by the fact that the low density of the cement mortar of the lightweight aggregate concrete is constituted by replacing sand at least partly by an equivalent volume of small air bubbles with a diameter in the range of approximately from 20 to 500 micrometers so that the volume of air bubbles is in the range of 5 to 30% of the volume of cement mortar and expanded organic and inorganic aggregate of particle density less than 200 Kg/m3 and of a size approximately from 0.2 to 2 mm and a volume from 5-20% of the volume of cement mortar in such a way that the total particle volume of the cement mortar constitutes nearly a continuous size distribution, the stability is increased and the homogenity is maintained of the fresh cement mortar and concrete by adding polymer microparticles and equivalent organic microparticles in the amount of 0.1-5.0% of the cement weight, said polymer microparticles consisting of a mixture of at least two different types, a first type consisting of synthetic polymer particles having a diameter of 0.1-1.0 micrometers on the surface of which an anionic or a combination of anionic-nonionic calcium stable surfactants have been adsorbed to an amount of 0.1-5.0% by weight of the synthetic polymer, and a second type consisting of natural or synthetic polymer microparticles having a diameter of 0.5-10 micrometers on the surface of which an anionic or anionic-nonionic calcium destabilizable combination of surfactants have been adsorbed to an amount of 0.1-5.0% by weight of the natural or synthetic polymer, wherein the weight ratio between the second type microparticles and the first type microparticles is in the range from 1:
Specification