Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2000-11-10
2003-06-03
Wood, Elizabeth D. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S694000, C106S718000, C106S719000, C106S803000, C106S811000
Reexamination Certificate
active
06572696
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to the field of additives designed for conglomerate building materials, and more specifically to the sector of projectable conglomerates such as projected mortar and concrete.
PRIOR ART OF THE INVENTION
The increase that the use of conglomerates has experimented in the building sector, as well as the onset of new preparation techniques thereof and of placement techniques (projected, injected, prefabricated conglomerates . . . ), is closely related to the use of products added thereto in small amounts. These products are known as additives and without their use it would be impossible to obtain more competitive products in technical and economic aspects than conventional products.
Among the different types of applications in which conglomerates require the use of additives for the purpose of achieving a satisfactory performance, are projectable conglomerates such as projected mortar and concrete. These are used for a diversity of applications among which stand out, supporting tunnels, stabilizing slopes, public works and covering facades.
Although projectable conglomerate materials are on many occasions of a very different nature, they have a series of fundamental properties and characteristics in common, for the purpose of achieving satisfactory yields in respect of the overall performance qualities for which they are manufactured. Among these characteristics, and fundamental properties, it should be emphasized that they must be capable of being dry or wet pumped by mechanical means in dense or diluted flow, in addition to having good adherence to the surfaces on which they are projected, good docility, suitable water retention, sufficient open time, absence of segregation of the components and of water exudation, good strength against compression, suitable surface texture, absence of cracks and good frost resistance.
Thus, projectable conglomerate materials must have a good adherence that is manifested in that when being projected on a surface, they must endure the least possible rebounding.
The docility of projected conglomerate materials leads to good workability in the facing on which they have been projected, consisting in a reduction of the effort and therefore of the time, that the worker must use to achieve a satisfactory final finish.
Suitable rheological behavior directly affects pumpability and workability of the projectable conglomerate material. This is due to the fact that the material, when being subjected to shear stress, should reduce its viscosity in order to reduce the necessary pumping energy per unit of mass, as well as the possible problems of clogging hoses and tubing of the projection equipment; however, when the shear stress inherent in stirring ceases, the materials should recover their colloidal structure increasing their viscosity and plasticity, for the purpose of obtaining effective covering of the surface on which they have been projected and for the purpose of reducing to the minimum the losses of material caused by the rebounding of the materials from the surface on which they have been projected.
Performance is a fundamental parameter for the efficiency and economy of projectable conglomerate building materials and refers basically to the covered surface per unit of projected mass for a same thickness of an applied layer.
Water retaining capacity is a determining property for correct setting of projectable conglomerate materials and has a direct relationship to their final resistance.
The open time of projectable conglomerate materials should be long enough so as to allow, before the setting thereof, their final finish to be carried out by the worker.
It is important that projectable conglomerate materials do not show segregation or exudation so that they have a correct homogeneity, for which purpose it is necessary to avoid separation of the components of the materials, in the tanks and pumping systems as well as once they have been applied to the surfaces.
Projectable conglomerate materials should also have a sufficient strength against compression so as to support the stresses they are subjected to once they have been projected. This is especially important when protecting surfaces and correcting stability problems in tunnels and other underground constructions.
The final texture and absence of cracks directly affect the durability of conglomerate materials, as well as the protection and consolidation of the surfaces on which they are projected. The absence of cracks is a critical factor for acceptance by workers who carry out the projection of the materials, as well as by the final users of the materials.
Frost resistance is important in applications of projectable conglomerate materials on facings and surfaces exposed to adverse weather conditions. This implies a direct impact on the durability and impermeability of consolidated surfaces and, consequently, on the profitability and efficiency of projection processes.
The above mentioned parameters and qualities should be taken into account when designing projectable conglomerate building materials.
Therefore, in the design of projectable conglomerate materials, such as projected mortar and projected concrete, in addition to establishing the proportions among the conventional components such as cement, aggregates and water in terms of the specific applications of the materials, the use of additives the purpose of which is to improve or modify the properties of the materials in the fresh and/or hardened state, is essential. Basically, the proportion of such additives should not be higher than 5% of the weight of the conglomerate component and they are normally added during the dry premixing, or otherwise during kneading with water, the “UNE-Una Norma Española=A Spanish Regulation”83200 Regulations (additives for concrete, mortar and paste) and subsequent ones depending on the additive in question, having to be complied with.
There is a diversity of additives for projectable conglomerate materials, among which the following groups should be emphasized:
Water reducing agents/fluidizers:(=the plasticizers). These additives, also called plasticizers, are used to increase the docility of projected building materials at a constant water/cement ratio, or to reduce this ratio to a constant docility. In general, plasticizers improve thixotropy, strength against compression, adherence and docility. However, they are very sensitive to overdose in which case they produce an excess inclusion of air, delays in setting or collapses of cohesiveness.
Promoters: These additives shorten the setting and/or hardening times and their use is very widespread in projectable conglomerate materials in view of the fact that, due to the peculiarities of the projecting process, placement in very short periods of time is required. Excess use of these additives produces mechanical regression and therefore dosage thereof must be strictly controlled.
Aerating agents: These additives have as their main function to improve icing-deicing cycle resistance.
Retarders: These additives delay the setting time of projectable conglomerate materials, which results in an extension of the open time and the possibility of working at temperatures higher than 25° C. They coadjuvate water retention and provide thixotropy to fresh material, carrying out “self-curing” which is very beneficial for the final quality of projected conglomerate materials.
Anti-rebound agents: These additives, such as for example conventional attapulgite and sepiolite, improve the fresh adherence and reduce the rebounding of projectable conglomerate materials.
Water retaining agents: These additives are products which due to their molecular structure and to their surface properties bind to the water by means of “weak bonds” and retain it in the matrix of the conglomerates during the setting and hardening process, thereby avoiding rapid drying and improving adherence.
Combinations of all the above mentioned additives are used in the formulation of projectable conglomerate materials, there no
Alvarez Berenguer Antonio
Del Valle Álvarez Bernardo Enrique
Hidalgo Martín Manuel
Limpo Orozco Francisco Javier
Klauber & Jackson
Tolsa, S.A.
Wood Elizabeth D.
LandOfFree
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