Concrete blocks and slabs, due to their technical properties and stylish design, have become the most popular material for paving surfaces in domestic gardens and public spaces. They have practically replaced pavers made of natural materials, due to their cost-effectiveness, availability and the fact that they retain their technical and aesthetic properties for many years with minimal maintenance. However, it is worth noting a few characteristics of this material to ensure its qualities are preserved for the long term.
Choose the thickness to suit the location
A very important consideration when deciding to purchase concrete pavers or slabs and use them for surfacing is selecting the appropriate thickness for the location and intended use. The principle here is very simple: the thicker the elements, the greater the surface’s load-bearing capacity. Therefore, for use on terraces and footpaths in the garden, concrete precast elements less than 6 cm thick can be used successfully. If passenger vehicles are to drive over the surface from time to time, the thickness of the elements should be around 6 cm. If, however, there is to be heavy vehicle traffic, those with a thickness of 8 cm will be suitable. If even greater load-bearing capacity is required to withstand loads caused by traffic such as lorries, construction machinery or agricultural machinery, it is recommended to choose elements with a thickness of 10 or 12 cm. The intended use of the paving slabs can be easily checked in the so-called declarations of performance, which every manufacturer provides. The principle of selecting paving slab thickness for specific loads does not preclude the use of thicker slabs in areas where people or lighter vehicles move. However, this does not work the other way round, as doing so risks causing permanent damage or cracking. Choosing the right thickness is something we can influence, so it is not worth taking risks by relying solely on our sense of design when making a choice.
Micro-cracks, efflorescence and colour variations
If efflorescence appears on a freshly laid surface of pavers or concrete slabs, and the entire construction process was carried out ‘by the book’, there is nothing to worry about. This can happen immediately after the pavers have been laid. It is the result of natural chemical processes occurring in the lime contained in the cement. The white deposit is calcium carbonate, which, under the influence of rainwater and carbon dioxide, gradually begins to transform into calcium bicarbonate and dissolves, subsequently washing away with the rainwater. Sometimes this process may take a little longer; however, it has no negative impact on the technical properties of the surface and is not considered a product defect. The same applies to hairline micro-cracks on the surface of concrete pavers and slabs, which can be observed after rain, on a drying surface. This phenomenon is caused by natural shrinkage occurring during the cement setting process.
Another issue that may cause surprise when laying a surface of concrete pavers and slabs is the colour variation between different batches of material. This is due to the significant colour variation in the raw materials used to make the precast concrete elements, namely sand, gravel and cement. To avoid this, the surface should be laid using several pallets (at least three) at once. Mixing the pavers ensures a uniform appearance and avoids a patchwork effect, making the surface look natural and attractive.
However, the natural properties of the pavers and their correct laying to achieve the best visual and aesthetic effect are not the only things to consider when deciding to use them for a surface…
Pavers that score top marks
Proper maintenance is also extremely important; whilst it is not particularly labour-intensive, it does require a degree of regularity. Impregnation is a key treatment. The main aim of this process is to protect the pavers from stains that can permanently affect their appearance and are sometimes difficult to remove, such as dirt, clay, coffee, wine or oils. “This can be done using specialist products designed for this purpose. Waterproofing should be repeated from time to time, depending on the frequency and intensity of use of the surface. It is not recommended to apply the product immediately after laying the surface. Waterproofing can only be carried out once efflorescence has disappeared from the pavers and concrete slabs. There are many types of impregnating agents available on the market,” emphasises Krzysztof Wilk, Chief Technologist at Polbruk S.A. Impregnation is the basic protection for pavers and slabs; however, it is also important to keep the surface clean on an ongoing basis.
It is also worth remembering that although precast concrete products are characterised by high durability and resistance, it is extremely important to maintain them properly during the winter. Without going into detail, you should not allow a layer of snow to remain on the surface; clear it using plastic tools rather than metal ones (which can cause permanent mechanical damage to the surface); and use magnesium chloride instead of salt, which will prevent white efflorescence on the surface. If we follow this advice, we will keep a surface made of precast concrete elements in good condition for many years to come.
Concrete pavers and slabs are almost ideal materials for paving around the home or in public spaces, as evidenced by their ever-growing popularity. However, before purchasing them, it is worth knowing how to select them for specific applications, what kind of performance we can expect from them, and also how to maintain and care for them properly so that they serve us for as long as possible.
