Rubber Kerb TB "Slate grey"

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 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.

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).