Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Patent
1995-10-30
1998-09-08
Marcheschi, Michael
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
106711, 106713, 106714, 106724, 106727, 106737, 106802, 106808, 106819, 106823, 524 2, 524650, C04B 1404, C04B 2400, C04B 2412
Patent
active
058041753
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/SE94/00389, filed Apr. 29, 1994.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of producing cement useful for preparing pastes, mortars, concretes and other cement-based materials with high workability at low water content, high strength and strength development and high density. The method includes mechanicochemical treatment of a mineral-polymeric or a mineral mixture of portland cement and a SiO.sub.2 -containing microfiller, for example silica fume, and/or powdery water reducing agents of melamine or naphthalene type in milling equipment, preferably with vibration grinding media.
2. Description of the Related Art
The prior art closest to the method according to the present invention is a method described in an article in Journal Concrete International, October 1992, page 56 with the title "Intermilled Silica Fume in Icelandic Cement" and the method described in the patent GB 2,006,737 for a "Method and apparatus for production of an activated mineral composition."
The first mentioned method (Concrete International, 1992 "Intermilled Silica Fume in Icelandic Cement") discloses milling of a cement clinker with gypsum and other additives together with silica fume. The last component is added in an amount of 5-7.5% by weight of clinker. By said method one tried to achieve a higher level of homogenization of the blended cement in order to obtain a more stable concrete with high mechanical properties. This method does not include the use of a polymeric component (e.g. powdery water reducing agents). There is no disclosure of any substantial increase of the strength development and of the density of the hardened cement paste or concrete. This is the case because due to high hardness and density of the rather coarse cement clinker particles, practically all the energy of the grinding media is used to crush the material without any significant increase of the surface energy of treated cement and consequently there is no increase of the strength development and ultimate strength of cement pastes, mortars and concretes.
The second mentioned method according to GB 2,006,737 suggests well known conventional mechanical grinding and activation of fine-grained cement mortar, which consists of ordinary portland cement with an average particle size of about 10 .mu.m and fine sand with a particle size of 60-1000 .mu.m (0.06-1.00 mm) in a pinned disk mill or vibration mill.
Due to the nature of mineral mixture components, particle size distribution and parameters of treatment, disclosed by this method, the main part of the consumed energy is used for decreasing the particle size of sand and cement and only a small part of it is stored as surface energy. There are also no basic changes and/or modifications of the material microstructure and main properties of the substance. This can easily be illustrated by the relatively low values of ultimate compressive strength of the mortar obtained with this activated cement, namely 55-65 MPa after 28 days of hardening, and also by a rather short period of strength development, as the hydration of the "activated" cement is almost stopped after 7 days of hardening.
Due to the relatively low level of stored surface energy and due to its relaxation, the cement particles start to lose their obtained properties after 2-3 weeks of storage.
Another serious drawback of this method is a drastic increase of the surface area, which according to generally approved knowledge leads to a required increased amount of water in a concrete mixture, i.e. the water to cement ratio, required to maintain workability (plasticity). According to this known method, the water to cement ratio is rather high, about 0.6. This fact is negative from the point of view of increased porosity, increased shrinkage, limited level of strength and low durability.
SUMMARY OF THE INVENTION
The present invention relates to a method for producing cement useful for preparing pastes, mortars, concretes and other cement-based materials, having
REFERENCES:
patent: 4495228 (1985-01-01), Cornwell
patent: 4504020 (1985-03-01), Nishida et al.
patent: 5234754 (1993-08-01), Bache
Haggstrom Marwin
Ronin Vladimir P.
Mangels Alfred J.
Marcheschi Michael
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