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Concrete In Australia : June 2008
Concrete sawing project at paper mill A large roadsaw and remote control wallsaws worked in close proximity. Concrete Sawing and Drilling Association Australia (CSDAA) members Cut and Core, Roosta Concreting and Diacore recently teamed up to complete a project at the Norske Skog Paper Mill in Albury. The works to be undertaken were associated with the upgrade of conveyor systems which required the removal of suspended slabs, in some cases up to 2m thick. Due to the precise tolerances specifi ed percussion demolition was not allowed to solve the challenges of this major schedule of work. Speed of removal was a big factor and it was decided that a combination of roadsawing, wallsawing, core drilling and wiresawing would be the preferred methods employed. Labour was a top priority in planning the works with much of it to be carried out during plant shutdowns. During these shutdowns Cut and Core and Roosta Concreting had up to 14 personnel on site at any one time all working 12 hour around-the-clock shifts. The depth of the concrete was generally 500mm to 700mm, and in some cases heavily reinforced. Some areas were up to 2m thick which needed to be wiresawn. Due to the depth of concrete and steel reinforcing, 32kW and 49kW roadsaws were used, as well as large remote controlled wallsaws and wiresaws. Another critical aspect of the project was protecting new structural steel which in some instances had been placed just prior to the cutting. This meant that when cutting, it was imperative that blades did not penetrate too far through the slab and damage the steelwork. Success in this area was achieved. Planning for the project began eight months before a blade or drill bit touched the concrete. Cutting sequences for safe and effi cient removal were planned which also had to work into riggers and structural steel programs. Due to all of the works being on suspended slabs with the blocks being craned out, safe lift loads also had to be calculated. Slurry control also was addressed. The fi rst section of conveyor to be removed was 19m long and 1.5m wide, with the cuts made through 600mm thick concrete. It was to be removed in 5 sections, each calculated to weigh around 5t, which was well within the lifting limits. Core holes were drilled at each crosscut to allow for wire feed. It was decided to wiresaw the crosscuts for speed and to eliminate the need for several more core holes to reduce overcuts. Longitudinal cuts were then undertaken, with one 48 Concrete in Australia Vol 34 No 2 of these cuts being placed at a two degree angle to ensure no jamming occurred. As these cuts were completed, supporting braces, which doubled as lifting braces, were fi xed onto each section. Once all the longitudinal cuts were complete and all the supports were placed, the crosscuts were then wiresawn and sections removed. Sydney CSDAA member Diacore was contracted to carry out the wiresawing on this stage. The same process was repeated during the second stage of works for other conveyor removals. Other works during stage two included wiresawing of pits of 2m depth, machine bases and other sections of suspended slab. Cut and Core had suffi cient labour available for this stage and carried out all of their own wiresawing for this and subsequent stages of the mill upgrade. During this stage there were also several 600mm and 700mm diameter core holes drilled throughout the mill. Thick suspended slabs were slung by crane while being cut. Where it was safe to do so, several fronts were worked simultaneously with up to fi ve drill rigs, three roadsaws, the wallsaw and wiresaws working continuously. While cutting was underway, another gang was maintaining slurry control and removal while riggers were continually manufacturing and installing individual lifting braces for each section to be removed. Ongoing site safety was effectively managed at all stages of the work. As the project continued Cut and Core was required on site for wiresawing of machine bases as well as several hundred core holes for new services to be fed to the new systems. In total approximately 300 lineal metres of core drilling of various diameter holes up to 700mm were drilled, 280 lineal metres of up to 600mm thick concrete was cut using roadsaws, 90 lineal metres of up to 740 mm thick concrete was cut using hydraulic wallsaws and approximately 90m2 of wiresawing was completed. All works undertaken were completed on time and with no safety incidents. For further information on CSDAA go to www.csdaa.com.au.