The natural ingredients of pavers
Pavers are made from a sophisticated mixture of different types of clay, sand, and other auxiliary materials. All of our raw materials are natural, and the clay is extracted locally, making our products extremely sustainable.
Local river clay
Many of our pavers contain large proportions of local river clay. River clay comprises clay, sand, and organic materials that rivers carry from the mountains and deposit in lower-lying deltas. The river clay for our pavers is extracted from the floodplains, often close to our plants. Using local river clay helps to lower the environmental impact of transport. In addition, river clay is officially regarded as a renewable raw material. As rivers deposit a new layer of clay every year, river clay is extremely sustainable. River clay has a lower purity, making it a ‘secondary’ clay. It contains relatively high quantities of sand, and its composition is not always consistent. As such, river clay is less stable than primary clay.
Primary clay
To produce high-quality pavers that satisfy market requirements, we also use primary clay. This clay was formed more than one million years ago and can be found in the ground in areas such as Westerwald and Oberlausitz in Germany. Primary clay is extremely pure, with a high clay content, and contains virtually no sand. It can be compared with the porcelain clay often used to produce kitchenware. For our Oberlausitz plant, the majority of the clay is extracted from quarries within a fifteen-kilometre radius of the plant. The extraction process often results in the creation of new nature areas. One of the features of primary clay is its high firing stability in the kiln.
Lava and chamotte
The clays we use are too greasy to be used on their own. In technical terms, the clay mixture is not sufficiently plastic for forming pavers, so we temper the clay with lava and chamotte.
Lava is an inert material extracted from the Eifel low mountain range in Germany. The extracted material is ground and sieved. Lava is essentially ‘pre-fired’, which means that it does not release quartz during firing. Lava improves both firing and drying behaviour. It gives the shaped pavers an open structure, allowing them to dry evenly from the core to the outside.
Chamotte is ground brick, a residual product from our own production process. The grain size is equivalent to that of sand. Like lava, chamotte is fired once, preventing it from decomposing when it is heated. Clay can crack if the temperature rises or falls too quickly during firing. Adding chamotte or lava to the clay mixture reduces the risk of cracking.
Moulded and wirecut
We use a different mixture for our moulded and wirecut pavers. The clay mixture for wirecut pavers largely comprises primary clay. To produce a good clay bar, the clay needs to be greasier and drier. Otherwise, the bar will sag.
The mixture used for moulded pavers is mostly composed of river clay, which contains more moisture, sand, and other materials due to the journey that the clay particles make before being deposited in lower-lying deltas. The higher moisture content means that the clay can be more easily pressed into and out of the moulds. Newly moulded pavers are much softer and can be kneaded more easily than newly formed wirecut pavers.
In many cases, the type of paver that is most representative of the streetscape in a country or region is determined by culture and history. The Netherlands has historically used moulded pavers, while Germany has traditionally used wirecut pavers. This is due to the local availability of raw materials: river clay in the river deltas of the Netherlands and primary clay in Germany.
Clay and colours
Clay is an important factor in determining the final colour of the pavers. A high iron content in the clay produces a red colour after firing, while lime gives more of a yellow colour. The type of clay also determines the colour. A large proportion of primary clay tends to produce more pronounced colours. To produce some colours, we need to add natural minerals, such as manganese oxide. The colour of the sand in sand-coated pavers is also a determining factor in their appearance. The atmosphere in the kiln is also important – the temperature, firing curve, stacking method of the pavers on the kiln trolleys, and oxygen content in the kiln all have an impact on the final colour and colour nuance. You can create your own unique colour mix by combining different colours.
Quality control
The quality of our pavers depends on getting the composition of our clay mixtures exactly right. That is why our clay mixtures are checked every day by independent experts and bodies. They measure the clay content, the ratio of coarse to fine sand, and the quantities of iron, lime, and organic substances. This allows us to adjust the composition and achieve the perfect mixture.
Everything you need to know about paving
Contact an expert
Customer Service
Advice on bricks, brick slips and pavers.
+44 (0)1954 268 075 [email protected] Ask your question