Skyscraper construction demands perfect concrete that delivers maximum strength, is efficient to process, and emits minimum emissions. To ensure that the right quantities of consistently highquality concrete are available on city-center construction sites whenever they are needed, Sika experts are assisting ready-mix concrete suppliers with their in-depth knowledge and innovative additives.
Driving a concrete mixer is a job that requires maximum concentration. Drivers have to deliver their load right next to Grand Central Station, just where pedestrians hurry across the street with their phones pressed to their ears and where tourists stop without warning to take a photo. Tec Crete delivers up to 100 truckloads of concrete a day to the site of the One Vanderbilt office skyscraper in Manhattan. The building is growing at a rate of up to three stories a week, and at 427 meters, it is the tallest building currently being constructed in New York.
Ultrastable in All Traffic Conditions
The demands the project places on the concrete are huge and start with the logistics. If a truck gets stuck in traffic on its way from the ready-mix plant in Queens, the quality of the concrete must not change in any way. Since space is tight on the building site itself, with no parking or storage areas, every delivery has to follow a strict timetable. Compliance with this timetable is only possible if every load of concrete matches up perfectly to the specifications. If concrete had to be rejected for quality reasons, work would be delayed across the entire site. Furthermore, the concrete has to flow well enough that it can be pumped up to the appropriate story. And once it’s there, it has to cure quickly and satisfy the extremely stringent compressive strength requirements. Three levels of quality control – at the ready-mix plant, on delivery to the site, and when the concrete is poured – make sure that it fulfills all requirements.
Suppliers Trust Sika
All this is done with Sika’s high-performance concrete admixtures. “We source all our additives from Sika”, says Michael Gisonda, Tec Crete’s Sales and Quality Control Manager. The company adapts the additive mixture it uses to the specific requirements of the building. The additives it uses include SikaR ViscoCreteR, SikaR ViscoFlowR, SikaR Stabilizer, and SikaTardR. The mix design is constantly adapted to take account of weatherrelated temperature fluctuations.
Less Noise, More Efficiency
A major city-center construction site brings an additional challenge in the form of noise. Local residents are particularly sensitive to it. But here again, Sika has the right solutions. Because Sika additives make concrete softer, it does not have to be mixed in the truck for as long, needs less pressure to pump, and, as a result, is much quieter to work. Furthermore, it flows better, which reduces both the amount of compacting it needs and the associated noise emissions. Using self-compacting concrete completely eliminates the need for vibration, the method of compaction typically used, and which is often felt to be a nuisance. The lower noise levels mean that many building sites can continue to work at night or weekends, which reduces overall construction time.
> 400 M
is the height to which the high-strength, self-compacting concrete has to be pumped to get to the current job section of the One Vanderbilt in New York.
is the time it can take to drive the 6.5 kilometers from the ready-mix plant to the One Vanderbilt site, depending on traffic.
is the number of trips the trucks make daily to deliver the close-on 70,000 m³ of concrete needed for the One Vanderbilt.
is the pressure at which the concrete is continuously pumped up the building. The concrete must remain cohesive throughout and the pipes must not block up.
truckload of concrete is tested by an independent laboratory to ensure it meets the quality standards for the One Vanderbilt high-rise.