Structural Renovations secured the works to complete concrete repair and masonry stabilisation to Westlands Primary School in Kent, working as a specialist sub-contractor to Kier Construction.
Westlands Primary School was constructed in the 1960’s and is a typical example of many schools built during the period with brick facades, reinforced concrete features such as window cills, window surrounds, columns and flat roofs with overhangs.
The window cills, lintels and surrounds are constructed from reconstituted stone or ‘engineered stone,’ using natural stone aggregates, such as portland, mixed with a cementitious binder, that is intended to resemble natural quarried stone. A recurring issue with this type of construction is that the embedded mild steel reinforcement which is used to provide tensile strength is compromised by both low cover and the relative high porosity of the reconstituted stone. This leads to expansive corrosion of the reinforcement (due to the presence of moisture and oxygen) and causes the ‘stone’ to crack and spall. Entire sections can be damaged by this process and repair is generally the most cost effective and practical method of treatment.
The treatment in this instance was to mechanically remove all loose and defective ‘stone’ together with any reinforcement that had lost significant section. New stainless steel reinforcement was fixed in position using a two part polyester resin. A temporary timber shuttter was formed to the profile of the area to be reinstated, which included drip, upstands and falls. The prepared broken back surface and reinforcement was coated with Sika MonoTop 610 and reinstated with Sika MonoTop 615 back to the original surface profile.
The brickwork in places at Westlands Primary School had diagonal, stepped cracking which required stabilisation. These were reinforced using Helifix Helibars set in Helifix Helibond Grout, a non-shrink cementitious grout, within the bed joints at regular centres along the length of the crack. Once installed the reinforced areas were repointed to match the existing pointing.
The works are to be completed over a number of phases to suit both the major refurbishment scheme by the Principal Contractor as well as the school term times and operating hours.