Set for completion in 1Q19, the 155 m Marienturm tower will be a new landmark in the skyline of Frankfurt’s banking quarter. From Master Builders Solutions®, MasterEase and Master X-Seed concrete admixtures have contributed to the new high-rise office complex.
After the foundation stone was laid in November 2016, the topping out ceremony was held in August 2018. Six days were allocated to the construction of each of the structure’s 38 floors, meaning time was a pressing issue and demands on the 39 500 m3 of concrete were accordingly high.
“One particular challenge was the specified strength at peripheral slab areas of 22 N/mm2 after 14 hours,” said Andreas Arbeiter, Managing Director of ready-mixed producer Sehring Beton. “But with Master X-Seed we even obtained a strength of 26N/mm2 after only 12 hours.”
“Constructing the Marienturm, Master X-Seed enabled us to obtain significantly earlier formwork removal and thus contributed to a faster construction progress,” said Sebastian Dittmar, Head of Application Technology Germany at the Construction Chemicals unit of BASF.
Challenging pumping height
Early strength was not the only challenge during the construction of the tower. Further requirements included pumping the concrete up to a height of 155 m. This required a particular flowability of concrete.
“This is why, next to Master X-Seed, we also used MasterEase, a new range of products that significantly improves the rheology properties of fresh concrete,” said Dittmar. “In this way, we were able to reduce the viscosity of the concrete – its stickiness – and improve its workability. This enabled us to pump the concrete up to the required height”.
“MasterEase is the ideal plasticiser for extreme pumping heights, as in the case of the Marienturm: the admixture reduces viscosity by up to 30% and provides the concrete with ideal rheology properties and a precise early strength that remains available even during extended work cycles,” said Arbeiter.
The company has also noted that a reduction in viscosity facilitates surface troweling, which is an added benefit for ready-mixed producers, but likewise in precast production or the casting of concrete slabs. In this way, it saves time and cost in each construction project, increases the utilisation of vehicles and machinery, and reduces wear-and-tear to mixers, pumps, and piping.
Custom-tailored mix designs
“In order to have the best possible concrete mix available to meet each requirement, close cooperation was vital,” said Nils Winter, Head of the Testing Laboratory at HOCHTIEF Infrastructure’s Technical Competence Center. “Together with the Master Builders Solutions and Sehring Beton teams, we developed a variety of concrete mix designs, with the goal to provide optimal solutions for every weather condition and every construction-site requirement – such as early strength or early trafficking – which only differed in their specific Master X-Seed dosage.”
Read the article online at: https://www.worldcement.com/europe-cis/05032019/master-builders-solutions-contributes-to-new-frankfurt-tower/