Baublatt 2020: Working on piles with brain

In Switzerland, the Brextor system has established itself as an efficient and precise method for pile breaking. But it was a long way to series production, as entrepreneur and inventor Alois Portmann explains while walking around the construction site. The next big step for his company is to expand abroad.

from Stefan Schmid

Machine operator Sandro Hodel guides the milling disc over the pile head with circular movements. In just a few minutes, it works its way through the concrete to the reinforcing bars. As soon as the chisels of the milling disc reach the irons, a slight jolt goes through the excavator. Then, to complete the first phase of pile breaking, the ends of the reinforcing bars are marked with dabs of colour.
The row of piles serves to stabilise the slope, as no anchors can be set due to the proximity to the property boundary. Workers from Aregger are using the system for the first time on the construction site for Energie Opfikon’s new headquarters. Following a theory course and workshop visit to BRC Engineering AG in Rain, Lucerne, the workers are now being introduced to the finer points of pile breaking with the Brextor system. Alois Portmann, BRC owner and inventor of the process, is also on site. He gives personal tips, shows prudent tricks for using the equipment – and how to process the pile heads gently.

tangent pile wall
Milling operations on the inside and outside at the same time are part of the Brextor’s well thought-out principle.

Inner- and Outer Cutter as a Clou

The Brextor Head is used in a second step. The Brextor Head can be coupled to the drive for processing the piles in just a few simple steps. A hole drilled beforehand in the centre of the pile serves to guide the inner cutter and align the physical forces towards the centre. There, the drill head now breaks the core tension of the concrete with the inner cutter. A second milling cutter removes the concrete on the outside, whereby the surface tension must be broken in order to avoid spalling on the pile cylinder. Milling inside and outside at the same time is part of the sophisticated principle of the process.
The conical tip of the inner cutter results in a natural cone that absorbs the slippage on all sides. In order to compensate the circular movements of the excavator bucket, the Brextor head must always be pressed down gently and perpendicularly, otherwise the reinforcement of the piles with a diameter of one metre could be damaged by the cutter. The line manager, an electronic aid instrument, helps the machine operator to compensate for the circular movement of the excavator boom. A laser connected to the machine receiver on the drive unit shows how much material needs to be removed. The drilling process is completed in five to ten minutes. The result is a uniform hollow cylinder in which the reinforcing bars are still located and which must be further processed. The drilling process was almost perfect. «The Brextor system is nothing more than the application of the laws of physics,» explains Portmann.

Pile breaking
In the first phase, the milling disc is used to remove the pile head down to the reinforcing bars (left image). In a second process step, the inner cutter breaks the core tension, while the outer cutter simultaneously breaks the surface tension of the concrete (image right).

Knowing the market

It was a long road before the system was fully developed for rationalised pile breaking, Portmann explains. After gaining experience in the commercial business, the road builder with a foreman’s diploma became self-employed at the turn of the millennium, renting, selling and maintaining construction machinery. He catches the trend early with the rental business. At the same time, he is on the road as a subcontractor on countless construction sites. With an affinity for technology, Portmann is therefore familiar with the needs of the industry and specialised civil engineering. And because he is constantly evaluating devices for his rental programme, he has a good overview of the manufacturers’ offerings. The idea of rationalising the processing of pile heads was born at the family table during a technical discussion between construction professionals. Having learnt about the principle of rock cutters with longitudinal breaking heads for hollowing out piles during a training course, he tries out such a device. Despite certain advantages in processing, he is not satisfied with the result.

Gain experience

Pile breaking with a pile cutter
The result after the second phase of pile breaking is a hollow cylinder in which the reinforcing bars are still located. These are then exposed.

Other procedures also prove to be disadvantageous. Certain devices push off pile heads hydraulically, whereby both the handling and the alignment of the force effect are difficult. These can only be used in areas without reinforcement; in the worst case, bars are bent or torn off, which makes the work for the connecting reinforcement difficult.
To achieve a good quality result, the piles previously had to be processed by hand. And to avoid damage, the smallest possible devices were generally used. However, the method is time-consuming, so larger hydraulic hammers are often used. However, because the effect of impact energy is difficult to control, damage to the piles is almost inevitable. The type and degree of damage is difficult to assess and, in the worst case, only becomes visible long after the impact on the pile head. Due to potential health risks, the legal requirements for hand processing in Germany are being tightened. In France, workers are allowed to carry out pointing work with a hammer drill for a maximum of three hours.

Risky practical test

«I don’t feel most comfortable with standard solutions, but with specialised applications. If others don’t do it, I occupy this niche,» says Portmann. So another solution had to be found. Mechanics in charge of maintenance realise initial design ideas. Prototypes are created, but still without the desired effect. Well-known manufacturers waved the idea aside after it was presented. He persistently has the design changed. «Not every improvement worked straight away. But I wanted to know why something wasn’t working and how it could be made to work,» says Portmann, describing the tough process of finding the solution through trial and error. A retired agricultural machinery designer with proven expertise in mechanics and hydraulics, who happened to be a neighbour, suggested combining inner and outer cutters in the drilling head. That was the breakthrough. «We achieved a good result straight away,» explains Portmann. However, he continues to lend a sympathetic ear to practitioners on construction sites and receives valuable suggestions on how the design can be modified so that the equipment can be quickly converted and adapted to the respective dimensions of the piles. The system is further optimised for contract work. “that was only possible because we have good mechanics of our own,” emphasises Portmann.
Convinced of the practicality of the invention, he took the big step in 2007 with a contract as a subcontractor for Strabag. Thousands of piles with a diameter of 50 cm had to be processed during the construction of the new Aldi distribution centre in Domdidier (Fribourg CH). «In the worst-case scenario, I would have had to use a hydrulic hammer,» he says laconically, looking back on his courage, but the system passed the practical test.

pile renovation with pile cutter
Foreign substances and dirt in concrete impair the static function of piles. With the inner cutter, piles can be drilled out to a depth of six metres for renovations so that a second pile cage can be concreted in.

Streamline construction processes

The use of the Brextor system and the patent application gives Portmann a technical competitive advantage in the Swiss market for pile breaking. Over time, however, the threat of market dominance caused some suspicion in the industry, which he considers unfounded from today’s perspective. This would have required too many personnel and machines, which would not have made sense for specialised applications. He therefore changes the strategy and also offers the system for sale. The first customer is the company Eberhard. Since then, more and more engineers have recognised the advantages of the process. Experience has shown that planners at the time were not satisfied with the conventional methods of pile breaking, both from a structural engineering and costing perspective. Damage to pile heads due to improper processing had led to conflicts between planners and specialised foundation engineers, says Portmann. It had been difficult to achieve the required quality at the specified costs, which had led to additional claims. As the processing time can be easily estimated with the Brextor system, labour and machine hours can be calculated more accurately. This is also in the interests of the client.
By using the Brextor system and integrating it into the organisational processes, construction programmes could be streamlined, although this requires meticulous planning. «We repeatedly found that there were too few pile heads ready for processing, resulting in costly waiting times,» says Portmann. The process gained definitive acceptance on the market when the Brextor method was explicitly mentioned in a tender. With the changed market presence, a memorable name had to be found for the tried-and-tested appliances, which the staff came up with. The brand is now well established in the Swiss construction industry.

Drilling out piles for renovations

However, Brextor is not only suitable for pile breaking, it is also used for renovation work. If the concrete of a pile is contaminated by inclusions, the core is milled out to a depth of up to six metres, fitted with a new pile cage and filled with structural concrete. The pile head core can also be milled out to create a stable foundation for H-beams or pipes. The device can be used for all piles with a reinforcement cage and structural concrete, which is the case for the vast majority of applications. However, the system is also suitable for use as an earth drilling rig. Brextor cannot be used if there are reinforcing bars in the centre of the piles.

Remove residual concrete
Brextor head and pile head crusher are 1.8 metres long. This allows reinforcements to be exposed to an appropriate height so that the length of the connecting reinforcements fulfils the earthquake safety standards.

Measured against standards

For the connecting reinforcement of the superstructure, the exposed reinforcement can be of different lengths. For floor slabs, the reinforcement must be less high than for pillars, which must fulfil earthquake safety standards. In this case, the pile head reinforcement must have a certain length. Only then can the ironworker connect the sub-reinforcement and further reinforcement. The Head with the cutters and the piel head crusher are designed in such a way that reinforcements up to a height of 1.8 metres can be exposed as standard. The measure is not chosen at random. To ensure that the tensile forces of the reinforcement can act continuously, a rule of thumb in structural engineering states that the height of the overlap must be forty times the diameter of the iron, as the construction practitioner Portmann explains. With 40 mm iron, the dimension would therefore be 1.6 metres. «With a length of 1.8 metres, we are on the safe side. This covers 90 per cent of the required mass for the exposed reinforcement,» says Portmann. However, customised products with longer components are possible.

Flexible thanks to modular system

The Brextor system comprises several attachments that can be customised to the different pile sizes. Due to standardisation, there is little tolerance on the outside when removing concrete, which is why the outer cutter must always be adapted to the respective conditions. The outer cutter can be replaced in 20 minutes, while the inner cutter takes around 45 minutes. A hexagon spanner is all that is needed to convert and replace the various components, which are secured with bolts. The changeover time is correspondingly shorter for rows of the same pile head sizes. Thanks to the modular system, all parts of the head and the outer cutter can be combined. In addition, the heads and milling discs use the same drive unit. This makes it possible to process piles with diameter 100 and 80 mm with a 50 mm inner cutter and only change the outer cutter in each case.

Pile breaking
The pile head crusher exposes the reinforcing bars (phase 3). Remnants on the concrete surface and between the reinforcing bars are removed with an electric hammer.

Targets for foreign expansion

The Brextor system is well placed to become a standard for pile breaking in Switzerland. Winning the special “Internationalisation” award at the Swiss Innovation Challenge 2017 was the impetus to offer the system on global markets. BRC Engineering AG was founded in April 2019 to drive market development internationally. Clear targets for international expansion have been formulated in the business plan for 2021 and 2022, with the system enjoying patent protection in the most important markets for 20 years since its registration in 2007. «I am convinced that our system will establish itself on the market», says Portmann.
The company already has a distribution agreement with Kinshofer, which specialises in attachments, for market development in Europe and, since mid-August, a cooperation agreement with the Singapore-based trading company ICE Far East Pte. Ltd. The focus will initially be on Malaysia, Hong Kong, Singapore and Thailand. During technical discussions in Bangkok, Portmann was able to see for himself the interest in the process and the construction expertise. Even in Asia, pile breaking has not been solved. Large areas of many countries are located at low sea level. Due to the unstable subsoil, pile foundations are therefore very important. BRC Engineering AG also maintains close contacts with the Arab market and South Africa. According to the company’s calculations based on market studies, the global market potential for special applications of pile breaking is estimated at 750 million dollars.
The system is to be further developed especially for the Asian market, where piles with a diameter of two and a half to three metres are not uncommon, whereby the height of 1.8 metres is to be retained for head and pile head crusher. The designers can also imagine a kind of mini-brextor for processing small piles and equipping the system with an electric drive. In order to be able to produce higher quantities, the system was developed to series maturity. Components such as the carbide chisels are sourced from German suppliers, while mounting plates, inner cutter carriers and parts of the pile head crusher are sourced from Italy. The expansion abroad also gives rise to discussions about relocating production to the sales markets. However, Portmann wants to retain the local production site as far as possible. «My greatest wish is that we can keep production and therefore jobs in Switzerland.»

Handover of Brextor to Aregger AG
The company Aregger is using the device in Opfikon for the first time. Picture: Entrepreneur Hans Aregger, Brextor inventor Alois Portmann and Urs Odermatt, Head of Civil Engineering at Aregger (from left).

Use of pile head crusher

In the meantime, the workers at Aregger AG are working on a third step: uncovering the reinforcement in the hollow cylinder that was created after the Head was used. To do this, they have mounted the pile head crusher on the drive module. Machine operator Hodel positions it next to the hollow cylinder and then crumbles the concrete with a force of 150 tonnes. It takes skill not to damage the reinforcement. Then a slight twist, another squeeze and the reinforcement becomes visible. Finally, an electric hammer is used to remove the concrete residue between the bars. It takes a quarter of an hour for the bars to protrude from the pile in a condition suitable for further processing. If everything goes well, the 143 piles on this construction site will be completed in a week. ■

Original press release in German.

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