| New Fetter Lane, London |
| Contractor: |
Alfred McAlpine plc |
| Subcontractors: |
Byrne Bros (Formwork) Ltd |
| Concrete Supplier: |
Hanson Premix |
| Volume: |
50,000 m3 |
| Concrete Description: |
60N/mm2, 80N/mm2 & Post Tension Mixes. |
| Admixtures Used: |
Glenium SKY 544, Glenium C315 & Glenium 27 |
Background
Pre-war, the east of the New Street Square site was home to a large printing works with the remainder taken up with residential developments. Although the printing works survived extensive bomb damage during the war, the site was redeveloped by the late 1960s / early 1970s into an office development. Current works required the demolition of existing buildings to make way for a new office complex, comprising eighteen, twelve, eleven, six and two storey buildings.
Demolition of the site was completed in 2005. Building B, the largest on the site, has been taken by Deloittes with occupation expected by the end of 2007.
BASF Admixtures
This new 1,000,000 square ft office development utilises high-strength mixes and the post-tension method, a technique of pre-stressing whereby steel elements (tendons) are tensioned after the concrete has hardened.
BASF’s Glenium C315 admixture was used specifically in the columns on this project. Glenium C315 is a unique third generation superplasticizer primarily developed for the use in the concrete industry where the highest durability and performance is required. Its unique mechanism of action greatly improves the effectiveness of cement dispersion, and gives the ability to work with an extremely low water/cement ratio, allowing for the manufacture of high performance concrete with high early (18-24 hours) and final strengths. Concrete of high density and low permeability is also produced.
Also used on this project was Glenium 27 for self-compacting concrete, which offers the lowest possible water/cement ratio and no segregation or bleeding. Compared to traditional superplasticizers, Glenium 27 reduces the need to risk retempering concrete on the job site with additional water and improves the engineering properties of concrete such as early and ultimate strengths modulus of elasticity; bond strength to steel, depths of carbonation, impermeability, resistance to chemical aggressive agents, shrinkage and creep.
As high-strength mixes were required on this contract, Glenium 544 Sky was also specified, as its ability to offer faster strength development, as well as improved concrete surfaces, was important.