Tacking on technology in construction

Clay Technology magazine
,
5 Mar 2020

Housebuilding in the UK is continuously falling short of the government’s ambitious targets, and companies are turning to new technologies and techniques to improve the situation, while maintaining standards of quality and living. From speeding up production to creating a better environment, Clay Technology takes a look at some of the ways the industry is improving construction.

With housebuilding quotas stunted and the industry waiting to hear the revised plans under the new UK government in the Spring Budget 2020, it is hard to envisage how builders will be able to meet such an aggressive 300,000 newbuild target.

According to the latest figures published by the Ministry of Housing, Communities and Local Government, newbuilds in England, UK, are falling far below par, with annual completed newbuilds totalling nearly 178,000. However, the starting of newbuilds reached only 157,550 between September 2018-2019, which represented a 7% decrease on the previous year. With the construction of dwellings down, it is essential for manufacturers to find more ways to reach those targets.


Making it modular

Prefabrication coupled with cutting edge modelling software and a state-of-the-art factory are helping to deliver new homes at high-speed and to a high quality finish.

UK firm Legal and General (L&G) Modular Housing division has recently planned the development of a new modular housing factory.

The factory is based in Elmet, with the capacity to construct 3,500 homes a year. These pieces are designed and manufactured at the factory then prepared for transportation nation-wide, where they are assembled on-site. L&G said that the production has benefitted from adopting techniques used in other high-production and high-quality industries, including those of aerospace factories.

Advanced software is used to model each property at the primary stages, accounting for the size and configuration, but also for material use and choice, and to minimise wastage. Each element of the building structure is designed for efficient and precise manufacturing of the parts to speed up the assembly stage. L&G said this approach allows the design team to work with millimetre-level accuracy and the knock-on effect to production results in reducing the overall build time by nearly half.

L&G said the combined technologies have helped to reduce the number of defects by up to 80% less than a conventional house built by traditional methods. They are also designed to lower resource consumption, including water and energy, and emissions produced, as well as being recyclable at their end-of-life.

‘What we are doing at Legal & General Modular Homes is ground breaking,’ Legal & General Modular Homes Chief Executive, Rosie Toogood, was reported as saying. ‘We have taken a high-tech engineering approach to developing our product range, designing and manufacturing homes in a truly innovative way that will transform the way homes are built in the UK. We believe modular manufacturing is vital to delivering much-needed homes, alongside supporting new skilled jobs and productivity growth for the UK.’

At present, the company is manufacturing two and three-bedroom modular houses, and is working to expand the technique to make larger structures, such as low-rises and apartment blocks.


Self-cleaning concrete

Sunlight is helping to improve local environments with photocatalyst coatings applied to building surfaces, in a relatively young yet rapidly growing market.

Background levels of pollution are gradually rising due to natural phenomena, but intensive industrial activities and ever-increasing transport emissions, due to growing populations, has meant that pollution is heightened, and even more so in densely urban pockets. While demonised for its high carbon intensity, cement and concrete are helping to address some of these problems on a small scale by wider use of materials such as photocatalytic surface coatings in buildings.

Photocatalyst materials react with natural sunlight to break down toxic pollutants in the ambient air to provide a cleaner, healthier environment. The material can be applied as a coating on indoor and outdoor surfaces for all types of buildings, structures, masonry and even in tunnels. While car parks and road sidings make excellent areas for tackling pollution, for tunnels, the purification capability of the photocatalyst is highly beneficial to address the low ventilation.

The market for photocatalysts is growing steadily, from the relatively low and conservative rate of two years ago to a healthy current position. According to Grand View Research, the global market for photocatalysts is anticipated to increase to US$4.58bln by 2025 with a CAGR of 11.5%. Their applications are many and wide-ranging, offering functionality across various water, air and soil purification applications, such as in wastewater treatment, for gas barriers and managing the growth of unwanted plant life. But buildings and construction projects represent more than half of the application field, and this is set to grow.

Coating building surfaces with a self-cleaning photocatalyst has benefits beyond carbon, as it also protects the area from dirt, dust and stains, and when mixed with a pigment, maintains the original colour vibrancy for longer. Also, while it does not require a significant degree of cleaning, certainly not indoors, outdoor surfaces may be refreshed by wind and rainfall that keep them clean and effective.

Titania has been the primary material used as the basis for photocatalyst materials, but there has been a lot of interest in finding alternatives such as zinc oxide (ZnO) and cadmium sulphide (CdS), and more recently, in pairing it with graphene to enhance the properties.

According to Italy-based manufacturer, Italcementi, typical results of its photocatalytics, for instance the i.active COAT product, show that 1,000m2 of surface coating would be the equivalent of planting 80 trees, taking 30 cars off the road, or removing 10 times the amount of pollution as the same sized leafed area.

Building on this, Italcementi has contributed to a research project to extend these capabilities by incorporating graphene into the formula, taking the efficiency up by 70% higher than use of titania alone.

Under the EU-funded Graphene Flagship programme, a collective of organisations has partnered to investigate the potential to develop this further. The project team includes Italcementi HeidelbergCement Group alongside the Universities of Bologna in Italy, Cambridge in the UK, Eindhoven in the Netherlands, the Israel Institute of Technology in Israel, and several other organisations.

Firstly, the Cambridge team produced graphene via liquid-phase exfoliation using water and atmospheric pressure, and carried out the process in the presence of titania nanoparticles to create the composite nanomaterial. This was used to coat a range of materials, such as exterior building walls, where it proved to degrade pollutants when exposed to sunlight, resulting in photodegradation of matter which could be safely cleaned or washed away.

To confirm the efficacy, the rate at which graphene-titania and lone titania could degrade nitrogen oxides was measured, reporting a 70% increase in the composite’s performance. This was followed by testing the degradation of rhodamine B, it being a suitable marker to compare results for a range of volatile organic pollutants. 40% more rhodamine B was broken down by the composite, although this was performed in water and under UV irradiation.

‘Coupling graphene to titania gave us excellent results in powder form, and it could be applied to different materials, of which concrete is a good example for the widespread use, helping us to achieve a healthier environment,’ Goisis said. ‘It is low-maintenance and environmentally friendly, as it just requires the sun’s energy and no other input.’


SureBrick

Forterra Head of Design, Technical Services and MMC, Richard Willetts, discusses the benefits of a new brick slip system that makes construction easier, while still being flexible enough for different designs.

Developing new systems and creating modern construction methods are essential for  industry to meet the demands of today’s construction markets. Forterra is just one of the UK based companies investing in technology as a way to deliver newbuilds and maintain high quality structures economically and quickly. In response to industry feedback that stated there were few systems that that did not rely on adhesives, even fewer were fully non-combustible and that the systems available imposed too many architectural restrictions, the company developed a new product line – SureBrick.

The system was set up to ensure that any traditionally designed building can still be constructed using a brick slip façade system, while allowing for the architectural features to be replicated.

The technique was researched with input from architects, specifiers and clients to ensure it met the criteria of all stages of the processes. It has been created to work for several types of projects and is suitable for use in in all newbuild and refurbishment projects, from public or high-rise buildings to volumetric modular construction. It can be fixed to a variety of backing wall types including steel framing systems, timber frame and concrete.

Following a soft launch in 2019, several projects have been completed using the SureBrick system. This includes Pinewood, a self-build project located in Durham, UK, and it is also part of a high-rise development in Manchester, called Outwood Wharf.

Adaptable system

SureBrick is a straightforward system with few components. The components are standard zinc magnesium coated SureBrick rails, brick slips (22–90mm-thick), real single piece brick pistol corners, special shaped bricks where required, stainless steel rails and fixings to suit the substrate. Slips can be cut from bricks or purpose manufactured.

The system is the first in the UK that can deliver complex and complete architectural flexibility including using soft mud or extruded bricks, one-piece corners, projections, shapes, detailing, and bond patterns, while all bricks are mechanically retained. Architects or designers would not have to compromise the design to accommodate it.

From a design perspective, the system is compatible with any 65mm frost-resistant brick and can easily incorporate traditional brick detailing and coursing alignments. Projects that require brick matching with local product types or existing buildings can therefore be accommodated. These results in thousands of design variances.

When it comes to technical properties, SureBrick is the result of extensive development and rigorous performance testing, ranging from exposure to thermal and weather cycles, fire, impact, corrosion and wind load resistance. In terms of onsite advantages, it is simple to install, removing the need for highly trained construction workers, and can be adjusted to accommodate site tolerances.

The mechanical fix eliminates long-term risks relating to poor installation and weather. Moreover, the system renders buildings windproof and watertight early in the construction programme, contributing to a faster and more cost-effective build process overall.

The system can easily incorporate traditional brick detailing and is also flexible in the way it is installed. Through the design of the carrier rails, bed joints can be increased by approximately 2mm. This provides 27mm per vertical metre of adjustment, which allows installers to accommodate construction tolerances and ensure brick coursing aligns properly with windows and doors. As well as allowing for flexibility in design and installation, addressing the weight benefits was also one of the key drivers for specifying a brick slip façade system - greatly reduced weight in comparison with traditional brickwork. This results in smaller foundations, and lighter systems also require less primary and secondary wall structure to support the system too. Not only does this reduce the cost of construction, it also reduces the environmental impact.

Further to this, smaller and lighter components mean fewer deliveries to site, which is of particular benefit for inner-city projects. Of course, where used on high-rise buildings, these benefits are multiplied. SureBrick is not only significantly lighter weight than traditional masonry, it is also lighter than many other brick slip façade systems.

Materials and testing

As the system’s overarching aim is to be easy to use while still allowing for creative freedom, the materials employed for the technique must  also be straightforward. SureBrick comprises only three materials – metal, clay brick and mortar – and is tested and certified as A1 non-combustible to EN 13501-1, meaning that the system is fire safe and there is no need for additional project specific testing. This offers a clear advantage regarding the construction of high-rise buildings. The process is windproof and watertight early on in the construction phase.

To test for weather and frost resistance, a single-storey wall panel was constructed and subjected to repeated heat, rain and freeze thaw cycles over a period of many weeks. This test is designed to replicate extreme weather conditions and accelerated ageing. Following this, the very same weathered panel was impacted with soft and hard bodies, and brick slips were hydraulically pulled out of the rails to measure the long-term system performance.

The Centre for Window and Cladding Technology sequence of testing required construction of a much larger, two-storey wall which underwent air and weather-tightness testing, plus wind load resistance, and again following all of this, impact. At various stages, the system was exposed to 600Pa wind driven rain with flow rates of 3.4L of water applied per square metre of façade every minute. For the wind load resistance, dynamic pressures of up to 3,600Pa were imposed using an aero engine to see if the system plastically deformed or buckled under extreme conditions.

Care was taken to ensure the walls used in these tests were representative of real-world situations and structures. Consequently, hard and soft brick types were investigated, as well as window interfaces, soldier courses, projecting and shaped bricks.

For the fire classification, samples of the key constituents were taken and tested in different ways, including cylindrical and powder form. To gain an A1 rating, all components must pass the tests and the composite make-up of the system by mass must also meet the requirements of the standard. Again, four combinations of the system were successfully tested to provide evidence-based comfort for specifiers. All testing was undertaken at third party UKAS accredited sites or laboratories.