The invention relates to a mineral sealing mortar to be applied at the plinth of a building for moisture protection and a building having a plinth to which the sealing mortar is applied according to the respective independent claim.

The technical field of the invention relates to the sealing of buildings and, in particular, the lower portion of the outer wall of the building, i.e. the plinth of a building.

A facade with or without a composite heat insulation system has to be able to withstand a lot. Especially the lower portion thereof is frequently subjected to severe stress. Most of the stress on the surface comes from the impact of spray water, meltwater, as well as soil moisture. The term "moisture protection" as it is used herein includes not only the protection against soil moisture, but also against seeping water or non-pressing surface water. Sealing mortar according to the invention is a sealing compound for use for example as protective layer against moisture, frost and for water resistance.

Known sealing mortars are of an organic type having an organic binder which is for example an epoxy resin. Organic sealing mortars are of advantage with respect to waterproofing. They allow for preventing the introduction of any kind of water impacting on the walls which would enter the wall material. Water entering the wall material is a problem as it causes damages, i.e. due to cracks caused by frost water or algal formation.

Sealing mortar is applied at the plinth of a building, e.g. with a trowel, in a few mm thickness onto a layer of a mineral mortar. The mineral mortar is typically applied in different steps so as to form several layers. Mineral mortars are of disadvantage insofar as they are not waterproofing. Known mortars have a composition comprising a mineral binder, like Portland cement or calcium hydroxide, sand and lime aggregates, fibers and starch. Adhesion improving agents and hydrophobing agents are added, if any, in a low amount. The application of such known "mineral" mortars to the plinth of a building would not solve the problem of providing "moisture protection".

It is known to apply to the plinth of a building several mortar layers for reinforcement and for sealing thereof. A mineral mortar is applied with a reinforcing layer (e.g. a mesh). The drying time depends on the thickness of the applied layer. In any case a long pause is needed because of the mineral mortar needs to completely dry out before the application of the waterproof organic sealing mortar. The drying time causes deliberate pauses in which the applicator normally leaves the construction site and comes come back another day. Typically a first layer of mineral mortar is applied. Since the mineral mortar needs to completely dry out after eight days a first layer of organic sealing mortar can be applied. A second layer of organic sealing mortar is applied one day later. Finishing the surface in this way needs a minimum of ten days. Because usually the applicator has several kilometers to get to the construction site, there is a strong need to avoid pauses during the application of the sealing mortar.

Therefore, it is an object of the present invention, to provide a mineral sealing mortar for moisture protection of the plinth of a building which overcomes or at least greatly reduces the disadvantages known from products already in the market. Especially, there is a need for a sealing mortar which allows for a proper moisture protection of the wall without the necessity of applying additional organic sealing mortar layers.

According to one aspect of the invention, there is provided a mineral sealing mortar for moisture protection of the plinth of a building. The sealing mortar comprises in a dry state 60 wt% to 70 wt% of aggregates, 10 wt% to 25 wt% of a mineral binder, 0.01 wt% to 1.0 wt% of silicates, 0.015 wt% to 1.0 wt% of modified starch, 0.1 wt% to 1.0 wt% of fibers, 0.3 wt% to 0.7 wt% of a hydrophobing agent and 5 wt% to 9 wt% of an adhesion agent. Advantageously, the addition of the hydrophobing agent in combination with the adhesion agent provides a mineral sealing mortar with a sufficient moisture protection and a good applicability. That means the mineral sealing mortar according to the invention does not require any additional moisture protection but rather the capillary water transport is prevented. Tests have shown that adding the hydrophobing agent in combination with the adhesion agent below the given values does not result in sufficient waterproofness, i.e. in a sufficient reduction of the water absorbance. Such a test includes the application of the mineral sealing mortar to a test surface (typical thickness is between 7 to 15 mm). Waiting for 28 days apply water with a pressure of 1.5 bar. The test is passed if no water protrudes through the layer of the mineral sealing mortar. On the other side of the range, above the given values for adding the hydrophobing agent in combination with the adhesion agent, the workability of the material decreases, i.e. due to film formation occurs on the surface of the material.

As modified starch a starch ether can be used. In particular aspects of the invention the mineral sealing mortar additionally comprises a chromat reducing agent or a water retention agent (i.e. methylcellulose).

Advantageously, the mineral sealing mortar according to the invention comprises sand aggregates. Preferably, a first sand aggregate fraction having a grain size of 0,1 to 0,3 mm, and a second sand, aggregates fraction having a grain size of 0,3 to 0,6 mm. The limestone grains preferably have a first fraction of grain in a preferred size of 0,5 to 1 mm and a second fraction is pulverized limestone. The pulverized limestone is of a size preferably has an average grain size smaller than 0,2 mm. All grain sizes are determined by making linear intercepts of the grain boundaries.

Advantageously, the sealing mortar according to the invention comprises aggregates with a defined sieve curve comprising a grain size range from 0.1 to 1.0 mm. Preferably the aggregates have an optimized grain size distribution having a high packing density such that the density of the mortar is enhanced.

Most preferably, the amount of adhesion agent is from 5 to 9 wt%. This amount is advantageous since the balance between workability and moisture resistance is kept best. According to one aspect, the adhesion agent is a redispersible polymer powder which allows preparing a dry mix of the mineral sealing mortar to be mixed with water at the construction site. As adhesion agent for example a copolymer of vinyl acetate, ethylene and higher vinyl esters can be used. These adhesion agents additionally act as hydrophobing agents so as to support the effect of the added hydrophobing agent. Preferably, the amount of hydrophobing agent between 0.3 to 0.7 wt%. Preferably, the hydrophobing agent is oleochemical hydrophobing agent, in particular with a carbon chain length from 14 to 18, for example in form of a sodium soap. The mineral sealing mortar can comprise 0.01 wt% to 1.0 wt% of silicates. Silicates according to the invention comprise air void reducer and/or rheological agents. According to a preferred embodiment of the invention air void reducer and rheological agents can be contained in similar amounts. A person skilled in the art knows what compounds are suitable for these purposes. Phyllosilicates or clays are useful, for example, as rheological agents.

Advantageously the mineral sealing mortar further comprises an air void reducing agent to reduce the porosity of the set mineral sealing mortar. This allows reducing the capillaries and, hence, the production of high-density, air-poor set mortar, in particular, with a minimum of pores at the surface thereof. Preferred air void reducing agents are blends of modified fatty, alkoxylated compounds and emulsifiers in emulsion form. Compounds useful for this purpose are known to the person skilled in the art.

According to one aspect of the invention the fibers added to the mineral sealing mortar are short cut fibers. Short cut fibers are of advantage because of the fiber length of 1.5 mm to 6 mm what is short enough to allow for a good applicability and provides a good strength. Preferably, the fibers can be polyvinyl alcohol fibers (PVA), polyvinyl chloride fibers (PVC), polyacrylonitrile fibers (PAN), polyamide fibers (PA), polyester fibers (PE), or polypropylene fibers (PP).

Another aspect relates to that the binder is Portland cement or calcium hydroxide or Portland cement and/or calcium hydroxide in combination with metakaolin. Furthermore, hydraulic lime or high hydraulic lime or trass flour can be used instead of Portland cement or calcium hydroxide.

In the following, the invention will be described in further detail by means of an example with reference to the drawing of Fig.1 which is a sectional view of a plinth of a building. In the example of Fig. 1 , the plinth 21 of a building is formed on the lower portion of the outer wall 22 of the building and extends below the upper edge of the raw bottom 23 of the ground floor. For thermally insulating plinth 21 (i.e. below an ETIC system 4 covering outer wall 22 of the base floor), insulation panels 1 1 (e.g. EPS insulation panels) are fixed to plinth 21. Known solutions described in the introductory part (not shown) in which insulation panels are covered by a reinforcing layer which comprises a mineral mortar in which a reinforcing mesh is laid, wherein the mineral mortar does not provide waterproofness, have an organic mortar is applied for sealing thereof. In difference thereto in the present illustration of the invention, only a single type of mortar, a layer of mineral sealing mortar 12 which might accommodate a reinforcing web (not shown) is applied to insulation panels 1 1. According to the invention a single type of mineral sealing mortar 12 is applied for moisture protection. Mineral sealing mortar 12 comprises 60 wt% to70 wt% of sand aggregates in a size of 0.1 to 0.3 mm and in a size of 0.3 to 0.6 mm, limestone grains in a size of 0.5 to 1 mm and pulverized limestone. As mineral binder 10 wt% to 25 wt% of calcium hydroxide, Portland cement and metakaolin are added. Further, the composition preferably comprises 0.1 wt% to 1.0 wt% of fibers and 0.15 wt% to 1.0 wt% of starch ether and/or cellulose

In the shown example the moisture protection is achieved due to adding to the mineral sealing mortar about 5 wt% to 9 wt% of the adhesive agent and about 0.3 wt% to 0.7 wt% of the hydrophobing agent which results in a sufficient moisture barrier and prevents the capillary water transport.

The water proofing properties of the mineral sealing mortar were tested according to DIN 1048-5, however, the amount of applied mortar was 12.5 kg/m ² and the prisms size was 20 x 20 x 4 cm ³ Before testing, the coated prisms of concrete were kept for 28 days in normed climate according to DIN 50014-23/50-2.

After 28 days of 0.15 bar water load no moisture ingress was found on the fracture surfaces of the broken concrete prisms. Tensile bond strength was tested according to DIN EN 1542. Concrete prisms of the same size as above were coated with the mortar in an amount of 12.5 kg/m ² . The testing of the tensile bond strength after standard conditions, water immersion, and after freeze-thaw cycles according to EN 1348 were conducted directly following the respective storage on 5 replicates, each.

After storing at standard conditions and at a testing velocity of 100 N/s average tensile bond strength was 0.80 N/mm ² . Failure was 100 % due to cohesion failure.

After water immersion and at the same testing velocity as above, average tensile bond strength was 0.54 N/mm ² . Failure was 100 % due to cohesion failure.

After 25 freeze-thaw cycles in 7 days and at the same testing velocity as above, average tensile bond strength was 0.58 N/mm ² . Failure was 100 % due to cohesion failure.