The Central Library construction site has its own story, and so do the Library’s construction workers. Their professional skills stretch beyond construction, with prime examples being carpenter Tarja, who used to work as a farmer, and crane operator Ricardo, who would be just as at home in the cockpit of a plane.
Naturally, crane drivers enjoy being up in the air, but few would be quite as comfortable if the cabin grew wings. Cuban-born Ricardo Oliva, or ‘Riku’, on the other hand, could sweep into the skies with great skill. Born in Havana, he used to be a pilot in the Cuban army and loves being up in the Helsinki skyline. He only wishes that the crane were taller, as you can’t see far enough from 40 metres!
The crane arrived on site in the second week of March, and since then Ricardo’s commute has been up and down the crane’s steps. Many people’s motivation for the job would stop right there, but Riku enjoys being up in the cab, and is looking forward to the summer and the views growing even more beautiful.
“There are lots of great buildings around you! Sometimes there’s time to take a look at the scenery, although your primary focus must, of course, be on what’s going on on the construction site. I’ve been working as a crane driver for nine years, and have also been involved with maintenance work on the machinery at the depot. I came from the depot in the middle of the forest to the sky in the middle of the city.”
Ricardo has been living in Finland for 25 years. He left Cuba because “we had a little revolution there”. In Finland, things are peaceful, as they are up in the crane cab – sometimes it can be a little bit too lonely though. Occasionally Riku daydreams of working down in the pit with other people. Broadening his expertise is an aim of Riku’s.
“I’m always gaining experience. It’s a bad day if I don’t learn anything!”
The crane lets beavers fly too. E.M. Pekkinen Oy’s logo is being shown off with pride for the first time between the cab and the counterweight, higher than on any flagpole. Pekkinen will be the main subcontractor for the Central Library project until the autumn, and the procurement of the crane falls within its duties. The company, whose activities are focused on excavation, will be celebrating 56 years in business this year, but never before has procuring a tower crane appeared on its agenda. To create the foundations, a crane lower than 40 metres would have been sufficient. However, it’s not hard to imagine the scraping sound if the crane were not clear of the roof of the building opposite when rotating…
So that the crane remains securely in place, it has been bolted into the bedrock and a secure concrete foundation has been built around it. This will allow it to lift loads of up to 2,400 kg, i.e. the combined weight of a couple of cars, to heights of up to 60 metres from the base.
Ramp disappears to make way for walls
Until now it has been possible to drive down into the pit with vehicles with caterpillar tracks, as well as those with rubber wheels, along the ramp located at the southern end. In March work was started to disassemble the ramp located in the Sanomatalo corner.
Vehicle access will be removed as socle construction is also due to start in the pit. Gradually, the foundations for the library’s basement will encompass the entire pit. As vehicle access will no longer be available into the construction pit, supplies and machines will have to be lowered into the pit by crane.
Also in March, the earth at the southern end of the excavation site shook from time to time as explosives in the bedrock were detonated for the reserve excavation for the central tunnel.
The workers access the depths of the pit via stairs built at the northern end. Although when looking down from above, all may seem calm down on the ground, there is always something going on. Boards are being put in place on the walls, the socles are being reinforced and cast, and, more centrally, the foundations for the northern end of the steel arc that will support the library are being constructed.
Large-scale dental equipment
The bedrock construction can, in places, be compared to the work of a dentist. To start with, the ‘cavities’ must be removed and the area levelled in preparation for the filling, as the concrete cannot be poured onto ragged bedrock.
A mini-excavator removes the loose pieces of bedrock and stones. Work can be started on building the walls when there is a sufficiently intact surface. The bedrock can also be strengthened by injecting a strengthening substance, such as microcement, into it.
Pekkinen’s ‘dental equipment’ also includes air compressors. They produce compressed air which is blown on the bedrock surface to clean it. There cannot be any sand or pieces of rock left under the foundations. Site manager Kyösti Kontio puts the blowpipes in place.
All the while, the crane is lowering new materials down into the pit, to be used for the foundations i.e. the socle moulds. The moulds are made of boards and plywood planks. The bedrock surface phase requires manual work, but pre-constructed large moulds will also be brought in soon. Using the pre-constructed moulds, six-metre-high sections of wall can be put in place- one 11-metre-long piece at a time.
From farmer to carpenter
The only woman on the construction site is a carpenter. Tarja Smolander has been working on construction sites for the past seven years, and feels at home within the construction sector. In the Central Library pit she works on the moulds.
“I trained as a farmer, and made my living from farming for five years. Working self-employed within that sector wasn’t very profitable, so I moved into construction work. I do everything within construction work, right down to putting nails in, and over the years I’ve gathered experience from a wide variety of tasks.
Of course it’s tough and heavy work, but I enjoy it. I feel ownership of my work. This is definitely my thing.”
Approximately 30% of the moulding is now complete, so with the concrete casting still to come, the phase still has a number of months left to go. At the same time as work with the moulds starts at the southern end, at the northern end the workers can move on to building the walls.
During the middle phases at the construction site, the foundations for the northern end of the steel arc – which will support the library – are set to be cast. The library’s framework will be supported by an unparalleled arc solution, which will allow for a completely open lobby space, unobstructed by pillars. The span of the arc will be 105 metres, and its southern end will be located in front of Sanomatalo.
Water is constantly seeping from the bedrock, so pumping the water away is an ongoing process, and the bedrock is being injected to make it more compact. It will take until the summer to reach a drier phase.
Theory and practice come together in the construction site office. The site management team – from the left: Jarmo Ahokas, Risto Sell and Kyösti Kontio – explain the technical realisation in advance and in detail before a solution is put into practice. This allows every stage to progress safely, efficiently and economically.