Interview with Mr. Sotiris Askanis, Project Manager of The Corniche
What did you concrete?
We casted the raft of the Corniche building. The preparation started from 06:00 Friday morning and the actual concrete started going in at about 00:30 Saturday morning, so 18 hours after the preparation began. Four concrete pumps were used, 1,673m3 of C50 grade concrete was placed. We had 4 crews which were dealing with the four pumps and there were 5 people per crew, so there were 20 people placing the concrete throughout a 16 hour period. They started at 00:30 Saturday morning and ended at about 16:30 Saturday afternoon.
Two batching plants were preparing concrete; one on each side of Limassol. We must have had about 30 trucks circulating around Limassol transporting the material to site. We did the whole thing right in the centre of town, in extremely restricted space without obstructing any traffic, closing any streets or obstructing any pedestrian movement which was quite an achievement.
We buried more than 400 tons of steel in the cast. All together that night more than half a million euros worth of material in steel and concrete were irreversibly fused together. You cannot get it wrong. So you can imagine the preparation that took place beforehand.
Why didn’t you do the casting during the day, from early morning hours until early evening hours?
It has to be at night to reduce the impact of traffic, it also has to be a Friday night because all the people who work for a period of 16 hours nonstop, the batching plants, the truck drivers the crews and the pump operators, must have the next day off which is conveniently a Sunday.
Do you need experienced workers for the casting concrete operation? Or can you employ even new members of the crew?
Well, we have done it before at The Address a year and a half ago. It was relatively similar quantity, was done with three pumps instead of four; but The Address was easier because it was not in the centre of town, we did not have problems with traffic, we did not have problems with space, we did not have any problems like that. But we have done it before in those types of quantities so we do have the experienced crews.
Were there any improvements from the previous casting concrete to the one in The Corniche?
Yes. We were more prepared – we had contingency plans in case something went wrong with the power, the water and the workforce. So we had 4 tone tanks filled with water in case there was a water supply cut for whatever reason and we also had a standby bowser off-site in case the water tanks weren’t adequate. We had three standby generators in case there was a power cut for whatever reason. We had standby lighting in case the floodlights did not work. In other words, we were extremely well prepared. We even had standby crews waiting at home to be called in any event and a mechanic and plumber on site to deal with any water/power issues quickly.
Two structural engineers, a concrete chemist and a field concrete technician were all on site throughout the 16 hour period.
I do not think anything could have possibly gone wrong that we weren’t prepared for.
Did anything go wrong?
Not really, no. It was very important for us to be well prepared because you feel far more comfortable while you are doing it knowing that you have Plan B, C and D for any sort of scenario. We had all that, we were ready, we knew the plan, we have done it before so we know how to prepare.
So is it the largest casting concrete of the project?
Yes, The Address was 1,630 m3, this was 1,673 m3, slightly bigger. So it is the biggest concrete pour the company has ever done.
We used various advanced concrete mixtures which were specified by the supervising engineers. One of these included microsilica in combination with finer aggregate sizes and it was used only for certain parts.
Why was this special concrete used only for certain parts?
There was one part under the core of the building where the raft was 200 cm thick and heavily filled with massive amounts of steel rebar. So microsilica and plasticizers together with finer aggregates were used to fill all the voids, maintain strength of the mix and cool down the high volume of concrete a bit.
What are the lessons learned? What would you improve for the next time?
Well there was a minor issue with the casting sequence which was not followed 100% at the beginning because of a miscommunication between casting crews and pump operators. However, this was swiftly dealt with and anything lost from it was very quickly won back with a simple redesign of the sequence which fully satisfied the specification.
The one thing I would improve is the communication from before about the sequence between crews and pump operators. But that is the only thing, everything else was just perfect.
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