Innovative robotic solution provides productivityPublished 10/5 at 14:01
Construction is currently underway in the Philippines on a massive bridge system connecting Cebu City with Cordova on the southern end of Mactan Island. The 8.5km Cebu-Cordova Link Expressway, slated for completion in 2021, will span the Mactan Channel with a 51m navigational clearance for shipping vessels. It promises to ease congestion between Cebu and Mactan and boost economic activities throughout the region by providing additional access to the island and the Mactan-Cebu International Airport for an estimated 50,000 vehicles a day.
The project relies on a carefully choreographed plan of simultaneous operations to meet strict deadlines. Expert logistics allow crews to avoid many hurdles; however, unforeseen challenges can still arise. When a bad batch of concrete threatened to derail progress on one of the bridge’s first pylons, project managers needed a creative solution that could quickly remove the poor quality concrete without damaging the rebar or putting the project behind schedule. Hydrodemolition was the only process with the precision and productivity to keep the project on track.
Cebu Link Joint Venture (CLJV) contacted Singapore based Asia Waterjet Equipment, the region’s premier hydrodemolition experts. Access and site conditions presented quite a challenge, but with decades of experience in some of the most hazardous applications, Asia Waterjet Equipment was more than up to the task. With the clock ticking and monsoon season in full swing, the team arrived onsite with an Aquajet ‘Aqua Cutter’ 710V hydrodemolition robot and Jetstream HP water jetting pump.
Passion for problem solving
“Our focus has always been providing the cutting edge tools to make challenging applications safer and more efficient,” said Chris Parkhill, Asia Waterjet Equipment sales director for Southeast Asia. “From the very beginning, we’ve been involved in some of the most hazardous operations out there. We understand the demands and dangers, which is why we partner with industry leading equipment manufacturers for robust solutions that maximise safety and productivity.” Pairing the right tools with experienced team members has earned Asia Waterjet Equipment a reputation for high quality results. In emerging markets, such as the Philippines, this expertise puts the company at the forefront. “From North Africa to South East Asia, we cover a lot of ground but being able to meet the contractor where they are is key to a successful solution,” added Parkhill.
CLJV was conducting construction on several bridge pylons simultaneously. To minimise disruptions to the local community, the project’s primary staging area, as well as the initial pylon, were only accessible from the coast. This meant the concrete had to be mixed 2.5km down the coast then transported by barge to the jobsite. From there, the barge was grounded, and the trucks disembarked directly onto the beach, with the pylon being 30m inland. Overall, the transportation delay had no negative impact on the concrete, although a complication with a single delivery threatened to throw the entire project behind schedule and over budget. Parkhill explains: “When you are working with concrete, sometimes things don’t go to plan. It’s a delicate equation, after all, and even a slight miscalculation can ruin the mixture. Unfortunately, when that happens, there isn’t an easy fix.”
Crews knew there was a problem immediately. The concrete was already setting as they pumped. Vibrating and other correctional methods failed, and the pour was ultimately unsuccessful. Even worse, the concrete fell 350mm short, leaving a mesh of exposed rebar. For CLJV and Asia Waterjet Equipment, the challenges were adding up, making for a very difficult repair. While CLJV had budgeted time and money for small complications, it could not afford to demolish the whole nearly complete pylon and start again.
Crews with handheld breakers or excavators could remove the poor quality concrete, but only by destroying the rebar. “There was no option; the rebar and existing good concrete had to be protected,” Parkhill said. “If CLJV went with traditional demolition methods, they’d have to open, pry apart where possible or cut the rebar and manually jack hammer out the bad concrete. There’s no guarantee a man using a jack hammer could gauge what’s good and what’s bad, so they’d end up removing extra. Then they’d have to bend the rebar back into place without breaking it, or weld or cut new threads and join with it threaded couplers. It would add weeks to the project and a significant cost to the budget. They simply couldn’t afford it.” Hydrodemolition proved the ideal solution using high pressure water jets manipulated by an automated robot to remove layers of deteriorated and damaged concrete as well as cleaning and descaling the exposed rebar, and removing non visible contaminants such as dirt and mud.
Building and crossing bridges
Productivity was also a concern. With simultaneous construction continuing on several other pylons in the area, crews needed to remove the poor quality concrete and complete repairs. With the ability to complete concrete removal tasks up to 25 times faster than a hand lance, the Aqua Cutter provided the necessary solution to keep the project on schedule. To assist, Asia Waterjet Equipment brought in Aquajet special application manager Kjell Isaksson to support the operation. “There were a lot of variables and no room for error,” Parkhill said. “To minimise the risk of delays, we decided it would be best to have an Aquajet specialist on site.”
Like the cement trucks, the Aqua Cutter and all support equipment, had to access the site from the Mactan Chanel. Proximity to the water and the frequent heavy rains of the monsoon season made ground conditions difficult. However, since the Aqua Cutter is tracked and self-propelled, the uneven, muddy terrain presented no problems. This mobility was also necessary for tackling the demolition itself. Once lifted the 4m onto the pile cap by a crane, the robot was able to easily manoeuvre over the rebar.
To help reduce cost and increase production, Asia Waterjet Equipment opted to use seawater for the majority of the demolition rather than bring in fresh water. The company continually filled two 20m3 tanks directly from the Mactan Chanel. The hydrodemolition robot operated at 1,000bar removing 10m3 of poor quality concrete at a depth of 150mm-250mm in days. “With the Aquajet Aqua Cutter, we increased productivity to a point where construction was back on schedule,” Parkhill said. “Without hydrodemolition, there’s no way CLJV would have been able to do that.”