LEVELLING MATERIAL

Abstract: Levelling material for use as levelling layer for uneven substrates composed by a coarse levelling layer and a loading layer. The coarse levelling layer is at least 10 mm thick and consists of a pumpable coarse levelling compound with a binder content of 4-14 % of the dry weight, water-binder ratio of 1-5 and a content of sand plus filler of 85-95 % of the dry weight. The compressive strength is 2-17 MPa. The loading layer is of such a type that it rests with all of its bottom surface evenly distributed over the top surface of the coarse levelling layer and has an even thickness. In a preferred version, the loading layer is a fine levelling layer. This fine levelling layer has a thickness of 2-15 mm and consists of a pumpable fine levelling compound with a shrinkage of at most 0.15 %.

Description: Levelling material The present invention deals with a screed material or levelling compound of the kind that is described in the preamble of the claim and that is to be used in the production of so called levelling layers, which are intended to level uneven substrates, e.g. concrete constructions, with the purpose of achieving a surface which is smooth and even enough to serve as a floor surface. Since a long time levelling of e.g. concrete constructions have been done by casting onto the load bearing concrete structure a relatively thick layer of a cement mortar. This early solution of the problem however has considerable disadvantages, among which it can be mentioned that the ' method is very time consuming and labour intensive. Another technique that has been used to make the concrete substrate smooth and even enough to fulfill the requirements of the later floor coverings, has been that one has tried to make the concrete itself even enough, e.g. by vibration casting, power floating etc, but this technique has not functioned well in practice, because it is costly and time consuming. From the Swedish patent SE 435 049 a self levelling compound is known for levelling uneven substrates. However, when the demand of levelling is great because the unevenness exceeds 10-20 mm, which often is the case for prefabricated concrete elements, the high consumption of material leads to too high costs when you want to meet the requirements for loading capacity which normally are asked for. A common requirement in local codes of practice, e.g. the Swedish Hus AMA 83, is that the levelling compound shall have an adhesion of at least 0.5 MPa measured after loading with a rolling office chair castor according to the Swedish Standard SS 92 35 07. The loading capacity of a product is determined by the content of polymer and the content of binder. These two ingredients constitute the major part of the production cost. The present invention has the aim to achieve a new levelling material of the decribed kind and with considerably lower costs than with traditional techniques for the production of levelling layers on uneven substrates, where the unevenness is great, e.g. exceeds 10-20 mm. This is of utmost importance, since the development trend goes towards thicker levelling layers because of increased requirements on sound insulation and also because of demands for placing installations in the floor screed. This aim is achieved by the invention with a levelling material of the described kind and which is characterized by the means in the characterizing part of claim 1. It has been found that with this levelling material, a floor can be produced, which in the long run fulfills the demand for loading capacity for fiooings of at least 0.5 MPa, measured according to the above mentioned standard and which can be produced with a coarse levelling layer with relatively low production costs, in spite of the fact that the loading capacity of the coarse levelling layer itself is lower than the finished floor which is produced thereof. As a loading layer, any material which is suited for the purpose can used such as wood, steel, metal, plastic, ceramic, fine levelling compounds of known kind etc. As example of production of a finished, levelled floor with the use of the levelling material according to the invention, a revelling can be applied in two layers. The first layer is made of the pumpable coarse levelling compound which is applied at a thickness of at least 10 mm. On this coarse levelling compound then a wearing or loading layer is applied consisting of a fine levelling compound with 2-15 mm thickness, preferably 5-10 mm Since the coarse levelling compound shall not constitute the finished surface, it can, as mentioned before, be made considerably weaker than usual and thereby can the costs for binder and polymer be kept low. The binder content is 4-14 %, preferably 5-10 % of the dry weight of the levelling compound. The binder in the coarse levelling compound, which preferably is hydraulic, can e.g. be high aluminous cement, different kinds of gypsum, portland cement, natural cement or combinations thereof. The water content is e.g. 15-20 % of the dry weight of the levelling compound, which means that the water-binder ratio, i.e. the water content divided by the binder content, is 1-5, preferably 1.5- 4. The water content and the water-binder ratio is determined so that a pumpable compound is obtained. The coarse levelling compound contains 85-95 % by weight of sand and filler, preferably 89-94 % by weight. The filler can e.g. be ground dolomite, ground lime stone, pulverized fuel ash from coal fired power stations, ground granulated blast furnace slag or combinations thereof. Except for binder, sand and filler, the coarse levelling matierial contains additives which are conventionally used in levelling compounds, viz plasticizer, polymer, cellulose, salts and antifoamϊng agents, altogether not more than 1 % by weight. The content of polymer is considerably lower than in conventional levelling compounds. 3-8 MPa, while its resistance against wheel loading according to the Swedish Standard SS 92 35 07 is less or equal to 0.4 MPa, i.e. considerably less than the finished floor surface. On top of the described coarse levelling layer e.g. a conventional levelling compound is applied at 2-15 mm thickness, preferably 5-10 mm, which in the following is called fine levelling layer. This compound is pumped and is preferably self smoothing. The requirements on this material is on one hand that the shrinkage should be at the most 0.15 %, preferably at the most 0.10 %, when measured at drying in 50 % RH and on the other hand that it shall have a resistance against rolling wheel loading measured according the Swedish Standard SS 92 35 07 which is at least 0.5 MPa, which fullfills the requirements on the finished floor. The requirements regarding maximum shrinkage is caused by the risk that fine levelling layer otherwise can disrupt the relatively weak coarse levelling layer. The same is the case for the requirement for a maximum layer thickness of 15 mm. Of course, this risk does not exist with loading layers made of wood or other floor coverings where there is no more shrinkage after the application of the floor covering. The requirement regarding resistance to loading is caused by the fact that the combined layer shall be able to withstand rolling wheel loading. The same goes for the requirement of a minimum thickness of 2 mm for such a fine levelling layer. Examples of commersial products which can serve as fine levelling layers are as follows: Universal and Grov from Strabruken AB - 147 Pronto and 311 Grosso from Allman Byggnadsservice AB Vetonit levelling compound from Partek Vetonit AB K15 from Ardex Chemie GmbH The invention will in the following be described by non-restricting examples. In the examples, the percentages given are by weight of the total dry weight unless otherwise stated. Example 1 Coarse levelling compounds were made with binder contents, water-binder ratios and filler and sand contents according to Table 1. Table 1 Compositions of coarse levelling layers. The binder consisted of 2/3 high aluminious cement and 1/3 anhydrate gypsum. The filler consisted of ground dolomite. The other additives amounting to 1 % of the dry weight were of conventional kinds, viz plasticizers, polymer, cellulose, unorganic salts and defoamers. However, the content of polymer was considerably lower than normally. On these coarse levelling layers, except for samle number 7, a fine levelling layer was applied at 5 mm thickness. This fine levelling layer had the following composition: The ingredients in the conventional fine levelling layer were the same as in the coarse levelling layer, only the proportions were very different. The shrinkage of the fine levelling compound was tested after drying in 50 % RH and was found to be 0.07 %. The compressive strength of the seven coarse levelling materials was tested on cast test specimens after 28 days. The specimens were 40 x 40 x 160 mm and were stored in 50 % RH. in Table 2 and the figure, which shows the compressive strength of the coarse levelling layer as a function of the binder content, curve A, and the corresponding water-binder, ratios, curve B. The numbers on the curve are the sample numbers according to table 1 and 2. Table 2 Compressive strength of coarse levelling compound and the resistance against wheel loading of the combined layer. Further, the resistance to wheel loading was tested according to the Swedish Standard SS 92 35 07. The results from this testing are also shown in Table 2, where samples 1-6 consist of a combined layer of coarse and fine levelling layers, while sample 7 consists solely of a coarse levelling layer. From tables 1 and 2, it can be seen that the coarse levelling compound alone cannot withstand the wheel loading requirement of 0.5 MPa even at a binder content of 14 %. However, when there is a fine levelling layer on top, the combined layer can fulfill the loading requirement, provided that the binder content is at least 4 %. Example 2 The new levelling material and the described technique was tested in full scale in a building project. Two different formulations of coarse levelling compound were used as follows: Binder Water-binder Filler + ratio sand Formulation 1 7 % 2.5 92 % Formulation 2 10 % 1.8 89 % The coarse levelling compound was produced as a dry mortar on a factory and 17.5 % and 18 % water resp. was added at the building site in a continous mixerpump. it was pumped out on the substrate, which consisted of prestressed concrete elements, to a thickness of 40-60 mm. After a few hours, the surface could be walked upon, and then a 5-10 mm thick layer of a conventional fine levelling compound - with the product name Universal from Strabruken AB - was pumped out. The floor surfaces were inspected after eight weeks and no skrinkage cracks could be observed, neither when formulation 1 nor formulation 2 had been used. The new levelling material and the described technique with a relatively weak coarse levelling layer with low binder content and high water-binder ratio however has shown to have further advantages. The drying time can be shortened towards half the time that is needed for conventional levelling compounds. Further, it has been possible to use screws when applying bases for partition walls, which is considerably quicker and less complicated than using tradition fastening with a bolting gun. The coarse- levelling material furthermore can be used alone, without fine levelling layer in such cases when the described loading requirement is not applicable, e.g. where there is little loading or where the flooring can take the loading which otherwise the fine levelling layer should take. Examples of the latter is wooden floors and ceramic tiles. Still another advantage is that the coarse levelling material is very economic to remove when reparing or renovating.

Claims: Claims 1. Levelling material for levelling uneven substrates, which matierial is applied on the substrate in at least two layers, one coarse levelling layer of at least 10 mm thickness made of a pumpable coarse levelling compound and on this a loading layer characterized in that the coarse levelling layer consists of a pumpable coarse levelling compound having a binder content of 4-14 %, preferably 5-10 % of the dry weight of the compound, a water- binder ratio of 1-5, preferably 1.5-4, chosen so that a pumpable compound is achieved and a content of sand and filler of 85-95 %, preferably 89-94* % by weight, that the coarse levelling layer of said composition is adjusted to have a compressive strength after 28 days hardening of 2-17 MPa, preferably 3-8 MPa and that the loading layer is of such a type that it rests with all of its bottom surface evenly distributed over the top surface of the coarse levelling layer and has an even thickness. 2. Levelling material according to claim 1, characterized i n that the loading layer consists of a fine levelling layer with a thickness of 2-15 mm, preferably 5-10 mm, a shrinkage after drying in 50 % RH of at the most 0.15 %, preferably at the most 0.1 %. 3. Levelling material according to claim 1 or 2, characterized in that the loading layer is made of a pumpable preferably self smoothing fine levelling compound with a shrinkage after drying in 50 % RH of at the most 0.15 %, preferably at the rfiost 0.1 %. AMΘIDED CLAIMS [received by the International Bureau on 22 September 1993 (22.09.93); original claims 1-3 replaced by amended claims 1 (1 page)] Levelling material for levelling uneven substrates, which material is applied on the substrate in at least two layers, one coarse levelling layer of at least 10 mm thickness made of a pumpable coarse levelling compound and on this a loading layer c h a r a c t e r i z e d i n that the coarse levelling layer consists of a pumpable coarse levelling compound having a binder content of 4-14 %, preferably 5-10 % of the dry weight of the compound, a content of sand and filler of 85-95 %, preferably 89-94 % by weight and a water-binder ratio of 1-5, preferably 1.5-4, chosen so that a pumpable compound is achieved, that the coarse levelling layer of said composition is adjusted to have a compressive strength after 28 days hardening of 2-17 MPa, preferably 3-8 MPa and that the loading layer consist of a pumpable, preferably self smoothing, fine levelling compound being of a wheel loading resistant kind with a layer thickness of 2-15 mm, preferably 5-10 mm, and a shrinkage after drying in 50 % RH of at the most 0.15 %, preferably at the most 0.1 %.

Inventors: ALEXANDERSON JOHAN, SAEFSTROEM BO, ALEXANDERSON, JOHAN, SAEFSTROEM, BO
Applicants: STRABRUKEN AB, STRAABRUKEN AB
Application year: 1993
Main classification: C09D5
IPC codes: C09D5, E04F15