Sidewalk tile has long become an integral part of the urban landscape, just as city gardening or asphalt concrete roadways. It would seem that the nothing new can be thought of for the pedestrian paths. Nevertheless, specialists from various scientific and industrial sectors regularly present novelties in this field – both concerning the improvement of such basic performance qualities of tiles as strength and durability, as well as totally innovative solutions that allow, for example, to turn pedestrian paths into a source of electricity.
ASPHALT CONCRETE GOES AWAY
In modern cities, paving tiles slowly, but inevitably displace the usual asphalt-concrete surfaces of pedestrian paths. Possessing more moisture resistance and frost resistance, it also has a more attractive appearance, revitalizing even the standard street in a typical residential area. The tile lasts longer, is less sensitive to mechanical influences and the influence of aggressive environments, and utility service workers spend less time to bring such a coating to the original, elegant look – the colors and shapes of modern tiles, and the number of their combinations tend to infinity. Square and rectangular bricks, fragments with rounded sides, tiles in the form of honeycomb, coil or diamond are among the most common patterns seen on the streets of Russia today. Less common and more decorative forms include tiles in the form of a double T, the so-called Roman stone, imitating an antique stone blocks, tiles in the form of a parquet and a number of other varieties.
Of course, improving the appearance of paving slabs, the leading manufacturers of this material pay no less attention to improving its characteristics. This is achieved mainly through the use of various kinds of functional additives in the production of tiles – and components both chemical and natural.
Cement, water, inert materials, plasticizers and color additives – this is the list of ingredients for the production of traditional concrete pavement tiles, common all over Russia and throughout the post-Soviet space. Considering that we published a series of materials devoted to concrete within the past years, this time we will limit ourselves to the most general description of the production technology of tiles.
Cement used lies between 300 to 700 grade; The most appropriate and the most used is the cement of 500 grade. When buying this material, the rule is observed: “one batch of tile – one producer, one batch of cement”. This is important for obtaining stable characteristics of the finished product: the tiles made with the use of cement from different lots may differ in quality and appearance, which, of course, is unacceptable for the buyer.
Stone or sand are used as inert materials in the manufacture of tiles. A higher quality of the finished product ensures the use of crushed stone fractions of 5-10 millimeters.
While cement and crushed stone are the main components of the mixture for paving slabs, a significant role in the production process is played by additional components, namely, a plasticizer and a dispersant. The dispersant helps to crush any component until a uniform composition is obtained. The plasticizer informs the finished mixture of plasticity and mobility, helps to avoid voids, holes in the finished products made from using a mixture of crushed stone.
In fact, both components are mineral additives that simplify molding and improve end product quality – thanks to them, the paving slab becomes waterproof, frost-resistant, and its strength doubles.
In addition, the tile made with the use of these additives has a visual glossy coating effect. Of the other additives, depending on the wishes of the customer, in the production process dyes can be used. The most commonly used iron oxide pigment dye, or others, which do not burn out under the ultraviolet rays and do not collapse under unfavorable climatic conditions. Depending on the technology used, the additives are placed in the solution in dry form or pre-dissolved in hot water.
Actually, water, which is an integral component in the preparation of any concrete, also plays the role of a plasticizer.
For the production of paving slabs producers apply a special plasticizer, consisting of 80% polymethylene naphthalenesulfonate, 10% sodium sulfate and 10% water. Due to its use, the mortar in the process of making tiles fills the previously prepared forms, forming a smooth surface. The finished products, thanks to the plasticizer contained in them, have increased strength characteristics, frost resistance, and the color dyes contained therein are not washed out.
The two main production technologies for obtaining the desired shape of the tiles are vibrocompression and viberomolding, technologies deserving a deeper explanation at another time.
TILE AND ECOLOGY
Given the increasing awareness of the impact of eco-friendly materials, it would be strange if the recycled raw materials were not used, among other things, for making paving slab. And the primary material used is plastic. The plastic road surface was recently first introduced in Europe, but the eco-friendly paving slabs have been made in Russia for some time and are a source of business for small and medium-sized enterprises.
Plastic bottles, plastic bags, broken plastic boxes are the prime sources of raw material for the production of plastic tiles. The purchase price of the raw material is cheap (about 3 rubles per kilogram) -however, the production and recycling plants together with the cost of organizing of several plastic reception points and their advertising add up to a significant amount. The market price of tiles made of plastic is much lower than that of common concrete analogs, making them more attractive to the buyer. With the growing complexity of production processes and multiplication of different variants and shapes of plastic tiles, this product will be more popular in the years to come.
Although the production of sidewalk tiles from recyclable materials is a relatively new business for Russia, domestic entrepreneurs are actively experimenting in this field. In the Far Eastern city of Blagoveshchensk, production of concrete tiles with the addition of rubber from recycled tires is booming. Automotive rubber gave pedestrian coating a special elasticity, which was repeatedly noted by the townspeople. The addition of rubber chips increases the strength and frost resistance of such a tile. With almost identical appearance and improved characteristics, the tiles with the addition of recycled rubber are a real solution to the problem of large amounts of garbage in the form of automobile tires, the burning of which causes great damage to the environment.
Environmental innovation often has money saving or inventors business savvy at its core. In the manufacture of paving slabs these producers use those groups of waste that the metropolis accumulates in excess and values at next to nothing. In the city of Belov, Kemerovo region, in addition to the already mentioned rubber and plastic, even glass and paper are used as additives in raw materials for the production of paving slabs and curb stones. Obtained in this way, products cost buyers much cheaper than concrete, and their production helps the populous Kuzbass get rid of tens and hundreds of tons of garbage a year.
POWER AT YOUR FEET
Although the segment of paving slabs production is conservative, we see great innovative initiatives not only in materials used, but in the whole concept of pedestrian walkway.
American companies Onyx Solar and Studio 39 together with students of George Washington University developed a paving tile capable of accumulating solar energy and use it for street lighting – or accumulate it for later use for any other purposes.
The first pedestrian walkway, assembled from innovative tiles, appeared on the university campus. It consists of 27 fragments with solar batteries capable of producing 400 watts of electricity. A small amount – but this is enough to illuminate the path itself with LED lights throughout the night. There are 450 of them in the track, and all of them are built into the covering of the footpath.
This is simple, as the solution may seem, turned out to be quite difficult at the stage of its implementation. Solar batteries are fragile things and to use them on a pedestrian path that is exposed to the mechanical effects of constant stepping was a challenge. The developers then offered special translucent batteries, resistant to mechanical stress. In addition, a separate technical solution was required, which made it possible to secure the electronic filling of track fragments from rain and atmospheric moisture – which was also done.
As a result, the cost of such innovative tile was significantly higher than traditional tile – however, as the developers assure, due to savings in street lighting and due to the ability to supply electricity to adjacent objects, it will pay off fairly quickly. How quickly, however, they did not specify.
It should be noted that in addition to its energy efficiency, tiles with built-in solar panels have an unusual and very attractive appearance.
The further destiny of the innovative product – whether it will remain only an experimental object or will be launched into mass production – will be solved by the results of testing, which is continuing at the present time. Note that, in addition to its obvious novelty and attractiveness, such pavement tiles also have their limitations – a necessary condition for its use in this or that area is a sufficient number of clear, sunny days per year.
Concluding this brief tour into the world of paving slabs, we note that in the future the market of these products used for the improvement of our life in the city, adjacent and industrial areas is simply huge. The growing demand for these products is determined by the useful qualities of the tile itself, which is increasingly replaced by other types of coatings.
Perhaps the most important of the properties of tiles is its ability to serve for a long time without loss of appearance and properties. Paving tiles are easy to lay – as with the use of special modern technology, if it comes to large areas, or manually. It is even easier to carry out repair work, in which damaged fragments of such a coating are promptly replaced with new ones. This material has an aesthetic appearance, it tolerates weather cataclysms – and puddles on it simply do not form due to the fact that the water goes into small gaps between the tiles … Therefore, one does not need to be an expert to predict that the need for paving slabs in Russia, where the construction sector is experiencing an upturn again, and will grow steadily from year to year.