PUDLO was specified by the ECI contractor, Morrison Construction, and designers, Hyder Consulting, and accepted by the Highways Agency for remodelling Junction 15 of the M40. BBA approved, PUDLO is a chloride-free cementitious powder additive designed primarily to provide integral waterproofing of Portland cement concrete and sand/cement render. With the addition of a hydrophobic pore blocker and plasticiser to line and fill pores, it reduces both water absorption and permeability by altering the capillary structure of concrete. This protects against moisture-borne corrosion and, consequently, extends the service life of the concrete structure.
Built at a cost of £76.8m, the 31- month scheme of works has improved traffic flow and safety at a busy intersection which carries 75,000 vehicles per day. It opened in autumn 2010. Work included widening of the existing M40 Junction 15 roundabout to 4 lanes and construction of several bridges: the M40 Longbridge Bypass Bridge, a four-span bridge to carry a new dual carriageway over the M40, the A46 Chasefields Bridge and Sherbourne River Bridge. A new roundabout has also been built with a number of underpasses to allow the safe movement of farm vehicles and non-motorised users under the A46.
PUDLO was specified for concrete panels to TerraClass™ retaining wall solutions manufactured by the Reinforced Earth Company for various parts of the scheme. It was used in 1500m2 of precast facing panels to a retained height of 6.5m in abutments and retaining walls to the A46 Chasefields Bridge. PUDLO has also been used in 250m2 of panels to 6.5m height in retaining walls to the M40 Longbridge Bypass Bridge, and in a further 130m2 of panels to 4.5m height in retaining walls to Sherbourne Brook Culvert.
Added to the concrete mix as part of Reinforced Earth Company’s quality controlled panel casting procedures, PUDLO provides integral corrosion and waterproofing of the concrete panels without the need for hand applied waterproofing. As an intrinsic part of the structural composition of the concrete, PUDLO protection is effectively ‘cast into’ the panels.
Alan Sleigh of PUDLO said: “All corrosive mechanisms to concrete are moisture borne. In waterproofing the concrete, PUDLO extends the durability by eliminating the ability of moisture carrying these corrosive elements from penetrating the concrete. Additionally, PUDLO enhances the chloride resistance, dimensional stability and compressive strength, and reduces drying shrinkage, cracking and the rate of carbonation. “These all help to increase the resilience of concrete used in bridge parapets, abutments and retaining walls to the effects of high-exposure class environment, to extend asset life for better return on investment.”