01.04.2023 Ι Reducing demand for fresh process water, Elematic’s new compact wastewater recycling device is also low maintenance. Used in the production of precast concrete elements, it joins other Elematic machinery in helping to make precast technology more sustainable.

With the arrival of the compact automatic wastewater-recycling device, Elematic is underlining the ability of its production technology to make precast concrete elements – and hollow core systems in particular – even more sustainable method of construction.

Complementing the much bigger filtration solutions the company has long offered, the 600mm (W) x 2,000mm (H) x 2,000mm (D) unit is capable of filtering up to 24m³ of water to below 10ppm of solid content daily. With a scraper conveyer automatically removing the settled solids, the device can operate for several days without manual intervention.The remaining sludge is then dry enough to be transported away using a regular truck for recycling. Perhaps for use as an affordable booster in batching and mixing plants for precast production, or in the ready-mix concrete industry.

“Companies can reduce their concrete consumption by several percentage points, depending on how many openings they’re creating,” explains Jani Eilola, Product Director, Floor Technologies, at Elematic. “With concrete accounting for 50% of precast production costs, being able to reduce its use by 5% will have a huge effect on profitability, saving the average precast factory about €67,500 annually.”

Doing more with less

These otherwise significant raw material savings pale in comparison with the huge reductions made possible by the attributes of hollow core slabs in general. Their optimized geometry, with large round or shaped voids, not only requires approximately half the concrete used in a solid, cast in-situ slab of the same size, but the drier mixture requires much less water, while the prestressed strands remove the need for many kilos of steel for reinforcement.

This minimalist attitude to material use even rubs off on to nearby vertical structures, such as column-beam or structural walls. The typically wider span (up to 23m) and superior load-bearing capacity of the pre-stressed hollow-core slabs allows for substantial reductions in the number of supporting columns required. It´s making them the preferred floor element in many shopping malls, office buildings, parking garages, etc.

The sustainability advantages of hollow core elements even remain evident years after the construction phase, due to their superior insulation and thermal properties that decrease the lifetime CO₂ load of a building. In fact, the cooling abilities of precast concrete buildings – which have less need for HVAC than the timber structures often thought of as being ‘greener’ – may well be a key benefit, as climate change advances.

“We’ve been using insulation for decades to keep precast concrete apartments warm,” continues Eilola, “but those in warmer climates now need to use insulation to keep them cool, and reduce their demand for cooling energy. The foundations and frame of a building could constitute 10-15% of its CO₂ emissions, but the use of hollow core can reduce that by around 50%,” says Eilola. “We have carried out studies on reducing the carbon footprint of a hollow core slab – the biggest factor is, of course, the cement – but there’s also the transport, so if your delivery trucks switch to biodiesel, or perhaps electric, you could save €1-2.50/m² of produced slab in terms of ETS (Emissions Trading System), maybe 10% of the direct production costs. Using additional methods, you can reduce emissions by up to 70% through switching to hollow core solutions.”

Ultimately, sustainability and significant financial savings are inextricably linked in the precast construction industry – a key reason for the immense popularity of hollow core slabs around the world.