Retrofitting PT Slab on Grade

Grouting Services designed and constructed the largest PT slab on grade in NZ for Lion Breweries in 2008 covering some 50,000sq.m. In 2017, a change of use in a section of the processing facility meant that a large section of the PT slab (40m x 30m) needed to be cut out and replaced with a PT slab incorporating drains and falls. Bonded PT slabs on grade are constructed with pre-stressing tendons housed within a galvanised duct which is injected with grout post slab construction and tensioning. Cutting a bonded PT tendon is structurally the same as cutting through conventional reinforcement. However, it is imperative that the integrity of the grouting is first verified. Several inspection holes were made and the PT tendons exposed to check the grout integrity. All tendons exposed and cut on site were observed to be fully grouted. While this was expected, it is pleasing to see the validation of the quality assurance methods and supervision on site, particularly given each longitudinal and transverse tendons in the original PT slab were 100m and 50m long respectively with 5-strands. The work was undertaken in conjunction with Conset Construction and specialist PT slab designer.