Rubber interlocking paver VG "Brick red"

The apparent density of a material describes the ratio of its mass to its total volume, including all pores, cavities, and air inclusions. For WARCO products, this value typically ranges between 600 and 1250 kg/m³. To clearly present the apparent density of a specific product, WARCO uses a scale from 1 to 5, with each scale value corresponding to a specific density range. For example, scale value 2 represents an apparent density between 780 and 840 kg/m³.

The physical density, also known as mass density, indicates the ratio of a substance’s mass to its pure material volume without considering cavities. It is expressed in units such as g/cm³ or kg/m³. For comparison: Water has a density of approximately 1 g/cm³ at 4 °C.

WARCO processes rubber granulate in its products, which is predominantly obtained from recycled used tyres. This so-called ELT granulate (End-of-Life Tyres) mainly consists of styrene-butadiene rubber (SBR) and natural rubber (NR) and has a physical density of around 1200 kg/m³. Some WARCO products also contain, or exclusively consist of, newly manufactured ethylene-propylene-diene rubber (EPDM), with a density of about 1600 kg/m³.

Since WARCO products are not made from solid rubber but from a mixture of rubber granulate and polyurethane binder, pressed into shaped elements with a defined proportion of pores and air inclusions, the specification of apparent density is crucial. It significantly influences the properties of the final product:

• Surface structure and resistance: Higher density leads to a firmer, smoother, and more resistant surface.

• Water permeability: Products with lower density are generally more water-permeable, making them particularly suitable for applications such as sports or impact protection flooring.

• Elasticity: Lower density results in softer and more elastic materials, while denser products are harder and more dimensionally stable.

By precisely adjusting the apparent density to the intended use, WARCO products can be optimally tailored to various requirements – from shock-absorbing impact protection mats to durable floor coverings for heavily used areas.

Rubber is an elastic material characterised by its ability to deform under tension or compression and then return to its original shape. This property makes rubber particularly effective for shock absorption, vibration reduction and impact sound insulation. In products made from polyurethane (PU) bonded rubber granules, the damping behaviour is further influenced by the elastic binder and the structure and density of the sheets.

A scale of 1 to 5 is used to rate the elastic, shock-absorbing and vibration-damping properties of a rubber product. A value of 1 represents slight but noticeable damping, while a value of 5 indicates exceptionally high damping performance. This classification is based on empirical studies and comparative measurements.

The elasticity of rubber and its importance

Rubber is made up of long, elastic molecular chains that temporarily adopt an ordered structure under mechanical stress. When the stress is removed, they return to their original disordered form, giving the material its high resilience. This elasticity enables efficient shock and vibration absorption.

Shock absorption - absorbing kinetic energy

Rubber can absorb kinetic energy through deformation and convert it into heat. On impact, the material deforms, reducing the forces acting on it. The damping effect is not linear, but increases with greater deformation. This means that rubber provides moderate damping at low loads, which increases significantly at high loads.

Vibration damping - reducing unwanted vibration

Rubber has viscoelastic properties, which means it has both elastic and viscous damping characteristics. Elastic damping occurs when vibrational energy is converted to heat by internal restoring forces, while viscous damping absorbs kinetic energy by internal friction. This makes rubber particularly effective in reducing vibration and shock.

Impact sound insulation - minimising footfall and impact sound

Impact sound insulation refers to measures taken to reduce the noise generated by walking or moving objects on a surface. Because of its elastic structure, rubber can effectively absorb and minimise these sounds. In addition, the material is wear resistant, ensuring that its sound-absorbing properties remain effective over a long period of time.

To determine the suitability of a WARCO product for a specific application, we recommend an individual assessment based on an on-site material sample.

The slip resistance of a floor covering describes its ability to prevent slipping. The EN 14041 standard defines Class DS and states that a floor covering must have a dynamic coefficient of friction of at least 0.30 under dry and clean conditions. Floor coverings that meet or exceed this value are considered slip resistant and contribute to user safety. Adequate slip resistance is particularly important in areas with heavy foot traffic.

The dynamic coefficient of friction is determined using the test method specified in EN 13893. This involves measuring the frictional resistance under standardised conditions using a sliding device. This procedure ensures that the measured values are reliable and reproducible.

A scale from 1 to 5 allows a more detailed classification of slip resistance. A scale value of 1 corresponds to a dynamic coefficient of friction of 0.30, which is the minimum requirement for Class DS. A scale value of 5 corresponds to a coefficient of 0.60, which is twice the minimum value for class DS. The classification of the scale values is based on tests carried out on representative samples, with the results interpolated accordingly.

For rubber granulate floorcoverings, slip resistance is significantly influenced by the physical density, granule size and structure of the material. A higher compression force during manufacture results in a denser material and a smoother, less slip-resistant surface. The type of granules used - fine, coarse or fibrous - affects the surface texture. The higher the scale value, the rougher the surface, the more pronounced the feel of the granules and the more open the pore structure. Depending on the composition of the granules, the texture can range from fine-grained to rough and grippy or even smooth and velvety.

New rubber granule flooring may require a break-in period before achieving optimum slip resistance. This can be due to release agent residues that are deposited on the surface during production and only completely removed by use or cleaning.

The condition of a floorcovering also plays a crucial role in maintaining slip resistance. Dirt build-up or inadequate cleaning can reduce the coefficient of friction and compromise safety. Regular cleaning and proper maintenance are essential to maintain slip resistance.

The abrasion resistance of a floorcovering describes its ability to withstand material loss due to friction or wear. It is a key factor in determining the durability, functionality and quality of rubber granulate flooring.

A scale of 1 to 5 is used to classify abrasion resistance. A score of 1 indicates that the minimum requirements of BS 7188 are met, while a score of 5 indicates excellent abrasion resistance in accordance with this standard. The classification is based on test results obtained from representative products and then interpolated.

Abrasion resistance is determined using a standardised method in accordance with BS 7188. A sample of material is tested using the Taber Abraser, a device in which two standardised abrasive wheels apply a defined pressure and speed to the sample over a specified number of cycles.

To assess material wear, the sample is weighed before and after each test cycle. The difference between the initial weight and the weight after the test represents the incremental weight loss, which is used as a measure of wear.

In addition, the ageing of the material under atmospheric conditions and its behaviour under progressive abrasion are considered over several test cycles. From these tests, the wear index and wear ratio are calculated, giving an indication of the long-term durability and suitability of the floor covering.

Water permeability, also known as hydraulic conductivity, describes the ability of a porous material to absorb and allow the passage of water. In the case of floor coverings, this is measured by the water infiltration rate, which indicates the quantity of water that, under the influence of gravity, penetrates and percolates through the material within one hour.

A scale ranging from 1 to 5 is used for classifying water permeability. A rating of 1 corresponds to a water infiltration rate of 0 mm/h, indicating nearly complete water impermeability. In contrast, a rating of 5 represents high water permeability with an infiltration rate of approx. 1000 mm/h – meaning around 1000 litres of water per square metre per hour can be absorbed. This classification is based on test results from representative tiles that have been interpolated for the respective product.

The water permeability of a material may change over time, particularly if the pore structure becomes blocked by external influences. This can occur, for example, when sand penetrates the surface or due to insufficient cleaning, as is often the case with livestock mats.

High water permeability, with ratings between 3 and 5, offers significant advantages in outdoor applications. In newly designed areas, elaborate drainage systems or surface gradients are often unnecessary, as rainwater can seep directly through the tile covering. This prevents puddle formation and ensures that the area remains permeable. Additionally, since the underlying substrate is not sealed, this property contributes to the environmental friendliness of the covering.

Tiles with low or no water permeability, classified with ratings 1 and 2, are thus only suitable for indoor use or covered spaces.

EN 16165 defines standardised test procedures throughout Europe for determining the slip resistance of floor coverings when walked on with shoes or barefoot. It includes four approved test methods that take into account dry, wet and soiled floor conditions. The introduction of this standard has replaced national regulations such as DIN 51130.

A practical test method is the measurement on an inclined plane using a test person. This determines the angle of inclination at which safe walking is still possible. The slip resistance classes established in Germany, from R9 to R13, are retained. For testing on slippery surfaces, the floorcovering to be evaluated is wetted with a standardised test liquid.

WARCO floor coverings are generally classified as R10. In addition, they are rated on a scale from 1 to 5, which describes the angle of acceptance: a scale value of 1 corresponds to an average acceptance angle of up to 10°, while a value of 5 corresponds to an angle of 17°. This classification is based on tests carried out in accordance with DIN 51130 on representative sample panels, with the results interpolated for the product.

The slip resistance of rubber granulate floorcoverings is significantly influenced by the physical density, granule size and structure of the material used. A higher compression force during manufacture results in a denser material, making the surface smoother and less textured. Depending on the granule size - fine, coarse or fibrous - the surface properties vary. As the granule size increases, the surface becomes rougher, the granules are more tactile and the structure becomes more open.

The texture of rubber granulate surfaces can range from fine-grained to grippy and even velvety soft. New floor coverings often require a break-in period before reaching their final slip resistance. This is often due to release agent residues deposited on the surface during production, which are gradually removed by use and cleaning.

Maintaining a consistently high level of slip resistance requires proper maintenance and regular cleaning. Dirt build-up and inadequate maintenance can reduce slip resistance and compromise the safety of the flooring. Professional maintenance ensures that the slip resistance properties remain effective in the long term.

Thermal insulation, also known as heat insulation, refers to measures that reduce the exchange of heat between an object or space and its surroundings. This heat transfer occurs through three physical mechanisms: conduction, radiation and convection.

Conduction describes the transfer of heat by direct molecular contact within a material. Substances with low thermal conductivity, such as insulating materials, reduce this effect. Radiation occurs via electromagnetic waves and can be influenced by materials that reflect or absorb heat. Convection refers to the transport of heat by moving fluids or gases and can be minimised by appropriate material structures.

A key parameter for thermal insulation is thermal conductivity, measured in watts per metre per Kelvin (W/(m-K)). It indicates the amount of heat that passes through a material one metre thick in one second when there is a temperature difference of one Kelvin between its two sides. The lower the value, the better the insulating properties of the material.

Rubber has a thermal conductivity of between 0.13 and 0.18 W/(m-K), depending on its composition. The thermal conductivity of WARCO rubber granules is between 0.14 and 0.07 W/(m-K). These values are based on measurements taken on representative samples and interpolated for the product.

The actual thermal conductivity of rubber granulate slabs is significantly influenced by the density, texture and thickness of the material. A thicker slab with a pronounced drainage profile and a density of 800 kg/m³ will have a significantly lower thermal conductivity than a compact 8 mm thick slab with a density of 1200 kg/m³.

For comparison: Highly insulating materials such as extruded polystyrene (XPS), glass wool or mineral wool have a thermal conductivity of around 0.03 W/(m-K), while dense natural stone such as marble has a much higher value of around 2.8 W/(m-K).