Concrete hardening retarder

Details Concrete hardening retarder Concrete hardening retarder

1999-12-15

2004-05-04

Zalukaeva, Tatyana (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S320000, C525S327800, C525S328900, C525S330200, C525S367000, C525S369000, C428S343000, C428S480000, C528S302000, C528S308700, C264S299000

Reexamination Certificate

active

06730764

ABSTRACT:

TECHNICAL FIELD
The present invention relates to concrete surface retarders and more particularly to concrete surface retarders used in the fields of tapes, sheets and films when previously applying tiles to precast concrete panels (PC panels), whereby smears on the surfaces of tiles can be removed with ease or the surface of aggregate is easily washed up and made exposed by directly applying the retarder on the surface of concrete.
BACKGROUND ART
The external walls of constructions such as buildings are in many cases decorated with tiles to make the external appearance thereof better and more beautiful. However, applying tiles on site to the concrete wall surface already made requires many workers and takes long time. Moreover, the adhesive strength of tiles to concrete is not always sufficient and some fixed tiles may be separated from and fall off the concrete wall surface.
For such reasons, the tile preapplied panel method has been employed, in which panels for concrete with tiles thereon are fabricated in factories beforehand and assembled on site. In this tile preapplied panel method, generally, the required number of tiles are arranged like a matrix and adhered to a tacky adhesive sheet to give a tile pack, and the obtained tile pack is placed on the inner surface of a form. Thereafter, with reinforcemnts arranged inside the form if necessary, concrete is poured into the form and left for a set. Then, after the set of the concrete, the form is disassembled to give a precast concrete (PC) panel.
By the way, in the tile preapplied panel method using tile packs, when a pack simply consisting of a tacky adhesive sheet and tiles adhered thereto is used, concrete which will later be fed to a form completely fills up the gaps (joints) between the tiles and therefore no joint section can be formed. Accordingly, tile packs of which the joints between the tiles are stuffed with tapes cut from a sheet of, e.g., urethane foam or polyethylene foam, or with a net-like shaped article punched out so as to fit the joints are usually employed. However, in such method, treatment of joints is laborious, leading to low productivity.
Moreover, in the tile preapplied panel method, inescapably, part of concrete leaks through joints and reach the surfaces of tiles. So, after the set of the concrete followed by the removal of the form, the cured or set concrete composition (mortar component) leaked onto the tile surfaces must be scraped off. It has been conventional that the cured or hardened concrete sticking to the tile surfaces is manually scraped off with a tool such as a scraper, a cutter knife. However, besides the cured concrete being so hard, the tile surfaces must be prevented from being damaged, making the scraping step troublesome and time- and effort-consuming. In addition to this, a fear of damaging the tile surface makes mechanically removing the set or cured concrete more difficult. As can be understood from the above, in the production of conventional tile packs, treatment of joints is complicated and troublesome and finishing the tile surface is difficult.
To make the tile surface treatment more easier and simpler, e.g., Japanese Patent Application Laid-Open No. 29821/1973 (JP-A-48-29821) and Japanese Patent Application Laid-Open No. 118325/1996 (JP-A-8-118325) propose a method for easily removing smears of concrete using a cement set retarder which is an additive to concrete.
Japanese Patent Application Laid-Open No. 29821/1973 (JP-A-48-29821) discloses a method in which the outer surfaces of a plurality of tiles are adhered to a tile sheet made of paper using a bonding agent blended with a cement set retarder. In this method, however, a large amount of water contained in the concrete composition is absorbed into the tile sheet paper, and the absorbed water tends to render the sheet wrinkled or swollen. As a result, the retarder cannot act sufficiently at the gap formed between the tile surfaces and the tile sheet and cannot give sufficient effects. Moreover, the bonding agent prevents the retarder from coming into contact with concrete and therefore the retarder cannot fully exhibit its effects.
Moreover, Japanese Patent Application Laid-Open No. 118325/1996 (JP-A-8-118325) discloses a method in which a sheet of which the adhesive layer contains a cement set retarder is used. In this method, however, there is a crucial problem that the adhesive layer often prevents the set retarder from coming into contact with concrete and consequently the retarder incorporated to the layer cannot fully exhibit its effects. Further, according to this method, the mortar component remaining on the tile surfaces can be removed with ease but to a limited extent, and efficient treatment of the joints between the tiles cannot be expected.
Japanese Patent Application Laid-Open No. 183643/1997 (JP-A-9-183643) discloses a cement retarder comprising a polyester obtained by the reaction of a polycarboxylic acid component having 2 to 6 carbon atoms in the main chain with a polyol component containing a polyhydric alcohol or condensate thereof having 2 to 4 carbon atoms, wherein the weight average molecular weight of the polyester is 300 to 100,000. The above cement retarder is poor in adhesion properties and needs to be used together with an adhesive, bonding agent, etc. However, the addition of an adhesive (bonding agent) in such an amount as to give sufficient adhesion causes a deterioration in cement set retardancy and therefore it is difficult to hold both curing or setting retardancy and adhesion properties compatibly.
As can be understood from the above, in the conventional concrete retarders, an adhesive component and a cement set retardative component are different from each other and such different components are simply mixed or blended. Considering the fact that the adhesive component does not have the effect of retarding the set of concrete and that the retardative component does not have the adhering effect, the idea of giving a single surface two different functions, i.e., the functions of adhering the tile surface to concrete and retarding the set of concrete, is itself contradictory and has a lot of problems. In fact, as was described above, since the effects of the retarders are hindered by the adhesive component or adhesive layer, development of new techniques has been desired.
Thus, it is an object of the present invention to provide a concrete retarder having both adhesion or adhesion properties and retardancy compatibly, and a concrete set retardative sheet using the same.
It is further object of the present invention to provide a concrete retarder which has adhesion and retardancy both at high levels and is capable of forming joint sections with good precision, and a concrete retardative sheet using the same.
It is yet another object of the present invention to provide a tile pack using the above sheet, and a process for producing a decorative concrete product using the tile pack.
It is yet another object of the present invention to provide a process for conveniently producing a decorative concrete product.
DISCLOSURE OF INVENTION
The present invention is done for achieving the above objects and characterized in that a retarder itself has adhesion or adhesion properties.
To summarize, the concrete retarder of the present invention is a concrete retarder comprising, as a main component, a polymer (A) having the ability of retarding the curing or set of concrete upon contact with unset concrete, and the polymer (A) has a low glass transition temperature (Tg) component having a Tg of not higher than −5° C. and a surface tension of not higher than 45 mN/m as a structural unit. The content of the low Tg component having a glass transition temperature (Tg) of not higher than −5° C. is about 10% by weight or more relative to the whole polymer (A). The polymer (A) may have a functional group which is able to form a salt with a metal ion (particularly, a free acid group, or a group capable of forming an acid group by hydrolysis). The polymer (A) may have a hydrophilic group (part

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