Pave the way


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When you see a concrete pavement with large amounts of grass growing through it, it is one of two things: Either the paving fails catastrophically, or you are looking at something widely referred to as “grass concrete.” For Bob Hooden, the occasional use of the term “turf concrete” is a frequent cause of frustration. “It’s Hoover Syndrome – People tend to think that everything paving lawn is“ concrete turf. ”But he says. This is because Grasscrete is the name of the main product that the company that owns and manages with: Grass Concrete, based in Wakefield, West Yorkshire. For the first time in the December / January 2021 issue of The Construction Index. Register online. Howden is keen to get this message across, especially now, as the company celebrates its 50th anniversary. Over the years, Grass Concrete has exported its reinforced concrete paving system to Worldwide and currently has 30 licenses serving 65 countries.Grasscrete is widely used in locations requiring strong and durable pavement but where the harsh, arid appearance of a continuous concrete surface is undesirable – for example, driveways, access roads, and parking lots. But it is increasingly appreciated. With the increasing incidence of extreme weather events due to climate change, runoff from solid, impenetrable landscapes is a major contributor to floods and pollution. A Paving that allows rainwater to absorb instead of running directly into a drainage system with an additional charge is much better. Grasscrete was invented in the 1960s by Jack Blackburn, a local authority engineer from Huddersfield. He understood the benefit of perforated concrete paving surfaces – in fact there were already products on the market. But he also understood the limitations of the current systems. All of these products were precast like any block paving system. Although it is suitable for areas with light traffic, it does not work well in locations such as lanes, where traffic is constantly passing the same lanes. “You get what we call“ elephant tracks, ”“ and it quickly turns rotting. ”With precast concrete blocks, this can only be prevented by lining the blocks in a solid and impermeable base path – which harms the paving’s ability to absorb Surface water. Grasscrete is an on-site reinforced concrete system and thus much stronger than block surfaces. The primary component of the system is the styrene slurry mold used to form the concrete structure. This is provided in 600 mm x 600 mm units which Howden describes as being similar to an “egg box” Inverted. ” The units are placed on the prepared surface to create a continuous mold and then a standard steel reinforcing mesh of 200mm x 200mm BS 4483 is placed on top with plastic mold ‘domes’ inside the grid. Then the concrete is poured over the plastic mold and pulled from a level above the mold . Once the concrete has reached sufficient strength, the surface is burned to burn the exposed plastic at the top. This opens up the voids inside the mold and remains only to spread the topsoil over the paving and sow it. The neat feature of the system is that the holes form cut cones that open at the bottom to give the grass roots Plenty of room to grow. A problem with other systems is that limited root growth impairs plants that can then die in dry weather. “Originally, Grasscrete was valued primarily for its aesthetic properties,” Howden says. “In the 1970s, we were dealing with modular construction and system building and the ability to incorporate green spaces into the urban environment was a boon,” he explains. But in recent years the demand for sustainable urban drainage systems (SuDs) has boosted the demand for Grasscrete and is now one of the main reasons for its use. While surface water will easily drain through the Grasscrete system, its ability to mitigate runoff depends on what happens below the pavement. “It’s not just a matter of how quickly the water drains,” Howden explains. Some SuDs collect surface water and temporarily store it in underground tanks or cell tanks. But Howden says the drainage blanket and the 150mm layer of micro-material that accumulates underneath Grasscrete can help preserve the natural hydrology. “And you can store the water and use it for irrigation,” he adds. The full potential of lawn paving for flood mitigation was greatly demonstrated by the holder of Grass Concrete’s license in Hong Kong during the rapid urbanization of new territories in the 1970s. The construction work resulted in a massive increase in surface runoff and regular flooding. The initial approach to addressing this was to create open drainage canals and slopes that were sprayed with concrete to prevent landslides and rock falls. Not only did this accelerate the runoff, it also severely damaged the natural fauna and flora, particularly in the indigenous wetland areas. Pressure from lobbying groups and the creation of a state environmental committee gave Grass Concrete, through its licensee, an opportunity to demonstrate its benefits. The change started in earnest since 1985 with the construction of the Lam Tsuen River training scheme near Tai Po. Instead of the usual solid concrete construction, this drainage channel has been lined with Grasscrete to become not only a reliable asset for flood relief but also a focus for a country garden that has developed around. At the same time, back in the United Kingdom, the need arose to create a clear standard for lawn paving systems under dense water flow. With a number of systems now available and no official standard in place, the Building Industry Research and Information Association (CIRIA) has set out to address this issue. In 1986, after completion of field trials, CIRIA published an enhanced grassy waterways design that demonstrated, among other things, that the lawn under dense flow becomes more hydraulically more efficient than was originally understood. The result of this was the ability for future drainage channels to be smaller in the department, have less impact and be less expensive. While Grass Concrete originally licensed its system to third parties, in the mid-1970s it began competing with current precast concrete systems in its own version, called Grass Block. Then the company decided to expand the contracting field, installing its own system on site, as well as selling it to third parties for installation. In 1981, Howden joined the company as a contract manager to develop this side of the business. “One of the reasons for this is that we were looking at how to control the level of fixtures – because at that time, we were supplying plastic molds and letting people throw them on site,” says Howden. From now on, business in the UK is completely centralized; The network of licensees was dismantled and Grass Concrete has taken over all installation work. “Customers have given confidence that the installation was primarily done by the manufacturer,” explains Howden. The contractual side of the business grew rapidly and in 2005 Howden led an administrative purchase from then-owner Sir Rodney Walker. “As Sir Rodney became less and less an executive within the company, they became more executives, and that culminated in the acquisition.” Around this time, the need for flood protection has demonstrated an increased focus on Grass Concrete, as it is already the case in the domestic market in general. “The UK is a huge market,” says Houdin. “In terms of sales volume, it represents about 85% – by value, that is – not by volume. That’s because, with international licensors, what we do is sell them makers of styrene blanks which of course represent a fraction of the installation cost.” In terms of units, we are probably selling an equal amount abroad as we do in the UK, but in terms of financial data it is probably 15%. ”Howden says the company, which reported sales of around £ 4m last year, is growing steadily by 10%. Approximately% per year He admits that Brexit has had a depressing effect, but Covid-19 has not affected businesses much. “We have worked properly through the pandemic, and one of the factors there is that a lot of our work is related to floods,” he says. This was classified as primary work, and hence work continued in most cases. We were able to continue and are approaching normal levels now. “We just finished a large parking project for Saracens Rugby in Barnet – it was an 8,000 square meter installation. As for the flood defense projects, we just finished one in Buckington, East Yorkshire and another in Saltash, Cornwall.” Howden adds: “We tend to have at least one flood defense project on the go at any given time, and there’s a number in the pipeline as well.” This article was first published in the December / January 2021 issue of The Construction Index. Register online. Story? Email [email protected]


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