A SELF-LEVELING SLURRY SCREED, AND A DRY PRODUCT FOR USE IN PREPARING IT

Abstract: The invention relates to self-leveling slurry screeds which, in addition to binder, usually cement, aggregate, usually sand, and water, as well as other conventional slurry screed ingredients, also include fibers, preferably polypropylene fibers. The invention also relates to dry product for use in the preparation of such self-leveling slurry screeds.

Description: A self-leveling slurry screed, and a dry product for use in preparing it The present invention relates to a self-leveling slurry screed and "to a dry product for use in preparing it; on site, water is mixed with the dry product to prepare a ready-to-use self-leveling slurry screed. The use of self-leveling slurry screeds has been known long in the building industry. The flow properties of these products have made possible the development of a new work¬ ing technique, according to which the slurry screeds are usually pumped onto the floor, where they level out and harden to form a surface capable of being coated. Some of the products available on the market are.also suitable for manual leveling. Water is mixed on site with the dry raw ingredients of the self-leveling slurry screeds to form a ready-to-use slurry screed. A typical amount of water mixed with the dry raw ingredients is approximately 20-25 % by weight, calculated from the dry ingredients. The basic raw ingredients include cement, which serves as the binder, sand, various fillers, gypsum as a shrinkage-compensating agent, as well as admix¬ tures which improve adhesion and provide flow properties. It is previously known to prime the base, before the slurry-screeding of the floor, with a mixture of a plastic dispersion and water, the purpose of which is to improve the adhesion of the slurry screed to the base, to prevent the escaping of water from the slurry screed and to prevent the access of air into the slurry screed from the pores in the base. Sometimes the adhesive properties are improved by using a so-called adhesion bridge, in which sand, cement or screed is added to a mixture of a plastic dispersion and water, and the mixture is brushed onto the base to be slurry-screeded. In spite of the steps carried out, slurry screeds require a good base in order to ensure adhesion. The base to be slurry-screeded must be firm and the surface must be clean, for example from cement adhesive. Special bases, such as wooden floors, are not normally suitable as bases for self- leveling slurry screeds, owing to the movement of wood due to moisture. Cement serving as the binder in slurry screeds will shrink when drying and will produce stresses in the slurry screed." If the stresses are high and the base is weak or unsuitable for the slurry screed, the screed may crack, detach from its base and break into fragments. Reinforcing of the slur¬ ry screed by means of, for example, metal mesh, will im¬ prove the situation somewhat, but the method is in practice inconvenient. From GB patent application publication 2 142 619 there is known a composition which contains cement, expansive agent, sand, water, air-entraining agent, and fluidifier. In this publication it is stated that the said composition is self- leveling, or at least partly self-leveling. It is indeed evident from the publication that the composition is cap¬ able of being pumped, but its rapid spreading over the base requires leveling tools. Thus the mixture described in this GB application publication 2 142 619 is a so-called flowing concrete, the fluidity of which is greater than that of conventional basic concrete and which is used in a rather thick layer to reinforce a frame surface cast from basic concrete, in which case it serves at the same time as a reinforcement layer and a coarse leveler. It is further mentioned in this publication that the composition may contain a small amount of polypropylene fibers (less than 0.03 % by weight) to improve the flexural strength of the concrete layer formed. It is the purpose of the present invention to provide a self-leveling slurry screed by means of which the problems mentioned above can be avoided and which, when drying and hardening, will form a coating which has good mechanical properties and adheres firmly to its base. According to the invention, these objects have been accomp¬ lished in a highly satisfactory manner by means of a self- leveling slurry screed which, in addition to binder, aggre¬ gate, possibly admixtures used in the preparation of self- leveling slurry screeds, and water, also contains fibers. The invention also relates to a dry product for use in the preparation of a self-leveling slurry screed for floors, the dry product containing, in addition to binder, aggre¬ gate and possibly admixtures used for the preparation of self-leveling slurry screeds, also fibers. Water is mixed with this dry product on site in an amount of approximately 20-30 %, preferably 22-26 %, calculated from the dry product. The fibers used in the slurry screed and dry product ac¬ cording to the invention may be, for example, synthetic polymer fibers, such as polyolefin, polyacrylic nitrile or polyvinyl alcohol fibers or carbon fibers or other fibers of similar types. Polypropylene fibers are especially ad¬ vantageous. The products according to the invention, i.e. the slurry screed for floors and the dry product, contain fibers pref¬ erably approximately 0.05-3 % by weight, calculated from the dry materials. The typical length of the fibers is 1-20 mm, preferably approximately 5-7 mm. The products according to the invention contain as binder preferably cement, but other binders or binder mixtures can also be used. The products contain as aggregate preferably sand, but other aggregates, such as limestone powder, can also be used. The products according to the invention may additionally contain various admixtures used in products of similar types, for example fillers such as fly ash, adhesives such as polyvinyl acetate (PVA) powder, shrinkage-compensating- agents such as gypsum, flow-promoting agents such as Mel- ment (trademark, manufacturer S K W) , anti-foaming agents, and retarders such as gypsum retarder. The following is a preferred composition of a self-leveling slurry screed according to the invention: 10-40 parts by weight binder, preferably cement 25-60 parts by weight aggregate, preferably sand 20-40 parts by weight filler, preferably fly ash 0.1-5 parts by weight adhesive agent, preferably PVA powder 0.1-10 parts by weight shrinkage-compensating agent, pref¬ erably gypsum 0.1-1 part by weight flow-promoting agent, preferably gypsum 0-1 part by weight other admixtures 0.05-3 parts by weight polypropylene fibers 20-30 parts by weight water, calculated per 100 parts by weight of dry materials. The following is a preferred composition of the dry product according to the invention: 10-40 % by weight binder, preferably cement 25-60 % by weight aggregate, preferably sand 20-40 % by weight filler, preferably fly ash 0.1-5 % by weight adhesive agent, preferably PVA powder 0.1-10 % by weight shrinkage-compensating agent, preferably gypsum 0.1-1 % by weight flow-promoting agent, preferably gypsum 0-1 % by weight other admixtures 0.05-3 % by weight polypropylene fibers. The surprising properties of the fiber-reinforced slurry screed for floors include the ability cf the product to remain self-leveling and pumpable in spite of the addition of fibers, since it could have been expected that the addi¬ tion of fibers would in general lead to the elimination of these properties, or at least to a substantial deteriora¬ tion of these properties. The self-leveling slurry screed according to the invention extends the use of slurry screeds also to surfaces which have traditionally been regarded as problem areas. It has been experienced as a deficiency of normal slurry screeds for floors that they are not suitable for the leveling of bases appearing in renovation and repair construction, such as weak concrete, wood and various compound floors (for example, magnesite floors or gypsum mix floors). The fiber- reinforced slurry screed according to the invention can be used for these purposes. The self-leveling fiber-reinforced slurry screed according to the invention can, in addition, be used for coating a rather soft base, such as a mineral wool base, whereby a well adhering, internally strong, resilient and wear- resistant final coating for use is obtained. The excellent useful properties of the slurry screed ac¬ cording to the invention are achieved by incorporating fibers, especially polypropylene fibers, into the screed. Owing to vigorous agitation, at the preparation step the fibers do not bind to each other but remain detached and are evenly distributed throughout the whole mix. The invention is described below in greater detail with the aid of an example and a comparison experiment. Example A mixture of dry ingredients was prepared by mixing vigor¬ ously the following ingredients: Water was added to this dry product at 23 % by weight, cal¬ culated from the dry product. The obtained slurry .screed is self-leveling and, when hard-- ening, it will form a coating which has excellent mechanr ical properties. Comparison experiment A compression test prism (prism A) was made from the slurry screed prepared in the example presented above and, respec¬ tively, a compression test prism (prism B) was made of a slurry screed which did not contain polypropylene fibers but in other respects corresponded to the slurry screed de- scribed in the example presented above. When prism B is stressed, at a certain stress the prism will fracture, i.e. prism B is brittle. Instead, when the fiber-reinforced prism A is stressed in a corresponding manner, prism A will remain cohesive even at stresses under which prism B will fracture. In other words, the fibers maintain prism A cohesive under stresses which the cement matrix cannot withstand. These test results show that the fiber-reinforced product withstands greater stresses and deformations without frac¬ ture than would a product which is not fiber-reinforced. Under field conditions, for example, in the question of weak bases, the fiber-reinforced structure ensures the functioning of the product, and the slurry screed consti¬ tutes in a certain sense a bearing structure which the fibers keep cohesive.

Claims: Claims 1. A self-leveling slurry screed which contains binder, aggregate, polypropylene fibers and possibly admixtures used in self-leveling slurry screeds, as well as water, characterized in that the amount of polypropylene fibers is 0.05-3 % by weight, calculated from the dry ingredients. 2. A slurry screed according to Claim 1, characterized in that the length of the fibers is approximately 1-20 mm, especially 5-7 mm. 3. A slurry screed according to Claim 1 or 2, character¬ ized in that it contains cement as binder and sand as ag¬ gregate. 4. A slurry screed according to any of the above claims, characterized in that as admixtures it contains filler such as fly ash, adhesive agent such as polyvinyl acetate pow¬ der, shrinkage-compensating agent such as gypsum, and flow- promoting agent. 5. A slurry screed according to any of the above claims, characterized in that it contains 10-40 parts by weight cement, 25-60 parts by weight sand, 20-40 parts by weight fly ash, 0.1-5 parts by weight polyvinyl acetate powder, 0.1-10 parts by weight gypsum, 0.1-1 part by weight flow-promoting agent, and 0.05-3 parts by weight polypropylene fibers, as well as 20-30 parts by weight water, calculated per 100 parts by weight dry ingredients. 6. A dry product for use in the preparation of a self- leveling slurry screed, containing binder, aggregate, poly¬ propylene fibers, and possibly admixtures used in the pre- paration self-leveling slurry screeds, characterized in that the amount of polypropylene fibers in the dry product is 0.05-3 % by weight. 7. A dry product according to Claim 6, characterized in that the length of the fibers is approximately 1-20 mm, especially 5-7 mm. 8. A dry product according to Claim 6 or 7, characterized in that it contains cement as binder and sand as aggregate. 9. A dry product according to any of Claims 6-8, charac¬ terized in that as admixtures it contains filler such as fly ash, adhesive agent such as polyvinyl acetate powder, shrinkage-compensating agent such as gypsum, and flow- promoting agent. 10. A dry product according to any of Claims 6-9, charac¬ terized in that it contains 10-40 % by weight cement, 25-60 % by weight sand, 20-40 % by weight fly ash, 0.1-5 % by weight polyvinyl acetate powder, 0.1-10 % by weight gypsum, 0.1-1 % by weight flow-promoting agent, and 0.05-3 % by weight polypropylene fibers.

Inventors: AALGARS RAINER ALLAN, HYYTIAE ARMAS TOIVO, LE BELL JEAN, LEINO MARKKU, SUNDEN FRED, TURTO HELENA INKERI, AALGARS, RAINER, ALLAN, HYYTIAE, ARMAS, TOIVO, LE BELL, JEAN, LEINO, MARKKU, SUNDEN, FRED, TURTO, HELENA, INKERI
Applicants: PARTEK AB, OY PARTEK AB
Application year: 1987
Main classification: C04B16
IPC codes: C04B22, C04B28