The Libeskind Tower And Citylife Project

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Works Going on in the New City Life District in Milan Mapei has always paid a lot of attention to the major changes that the city of Milan has had to tackle during the recent years of major urban design and development. The Group has been playing a leading, hands-on role in the construction of the city’s new skyline. Proof of the Company’s interest and involvement can be found in the articles dedicated to the Porta Nuova project, Expo Milano and the inauguration of the Allianz Tower that has been built in the CityLife area. This district represents one of the largest redevelopment projects in Europe and extends over an area of 366,000m2 with a complex combination of public and private developments for housing, business hubs, shopping centres, services and parkland. And Milan’s new CityLife district has always been Mapei’s jewel in the crown since 2012, when a round-table was held on “The Building Industry: Innovation through Design”, organised by Spazio City Life Group, which highlighted the importance, from a redevelopment and design point of view, of the Three Towers commissioned to three equally famous architects: Arata Isozaki, ZahaHadid and Daniel Libeskind. At the time, Mapei had already works going on in the new citylife district in Milan become the first European company to patent a new family of acrylic-based, super-plasticising admixtures, which allowed the entire ready-mixed and pre-cast concrete industry to make an important step forward in terms of quality, thanks to the possibility of producing fluid concrete mixes with very low water/cement ratios. This is a crucial characteristic for concrete mixes with long workability times, enabling concrete to be poured continuously, including in hot climates, without having to add more water. And it was the use of this new generation of acrylic super-plasticisers that enabled the enormous foundation slab on which CityLife has been built and where, amongst other things, it was essential to keep hydration heat under control to prevent cracking. Located at the centre of the composition formed by the three towers, thanks to its arched conformation (hence the nickname “The Curved One”), the function of the building designed by Libeskind is to act almost as a link between the other two. Its foundations were built in November 2015, while construction work got underway in the spring of this year. Building work is scheduled to continue until 2018 and,

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once completed, the skyscraper will have 31 floors for a total height of 175m and a total commercial surface area of 33,000 m2. Apart from this building, Daniel Libeskind has also designed a residential complex in nearby Via Spinola.
The Concrete Used for The Tower
The base slab for the Libeskind Tower was cast at the end of November 2015. This was a record-breaking operation with 5,890m3 of concrete poured in little more than one day. The contractor Colombo Costruzioni and the concrete company Holcim (Italia) divided the 30 hours of work that had been scheduled into three 10-hour shifts. For each shift there was one general logistics-production foreman, 45 drivers, each one with a 10m3 concrete truck, three operators with pumping equipment with a capacity of 200m3/hour, at least three operators controlling and supervising the production and quality of the mix, 5 operators working in the mixing units, a maintenance technician to look after the equipment, 18 trucks to transport the aggregates, 9 trucks to transport the cement and around one hundred workers on site to lay the concrete and support all the operations while the concrete was being poured. All those involved in this phase, from the contractor to the supplier of the concrete, made sure all required resources were available to ensure that each step was carried out as scheduled to construct the base slab, which has an irregular hexagonal shape up to 66 m by 40 m and a thickness of 2.50 m. After carrying out a series of site surveys, Holcim (Italia) designed a unique mix of C32/40 concrete with exposure class.
Mapei Admixture in Use
All the mixing units were fed with CEM IV 32.5 R LH SR Pozzolan cement manufactured by Holcim (Italia) in their facility in Merone (Northern Italy). They also supplied aggregates from their own quarries in Gorals, Pioltello and Segrate (Northern Italy). As far as the admixtures were concerned,
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Holcim (Italia) worked closely with Mapei to identify the most appropriate product to comply with all the specifications. In this case, the acrylic-based super-plasticiser DYNAMON XTENDW300 R was tested and approved. This product is a watery solution of modified acrylic polymers and is particularly recommended for the production of high quality ready-mixed concrete in compliance with the requirements of UNI 11104- UNI EN 206 standard for high quality concrete in consistency of 650 -700 mm and self-compacting concrete. Mapei Technical Services technicians were also present on site supporting Holcim (Italia) technicians, when the concrete was being poured, with experienced engineers from the Mobile Laboratory Unit to take samples of the concrete. Around 12 hours after pouring the concrete, and once the level of the upper layer had been reached, polythene sheets were placed over the concrete to protect it and maintain the correct level of moisture and thermal gradients. The sheets were removed after around seven days. Thermocouples were placed in the concrete to measure the thermal gradient between the core and surface of the slab and the surrounding temperature near the slab. Thermocouples were placed in the concrete to measure the thermal gradient between the core and surface of the slab and the surrounding temperature near the slab. This data allowed the curing period of the slab to be established very accurately. Reference: RM International, Issue No. 58/2016