Controlling Movement in Concrete Tanks
In order to ensure success of your remedial repairs it is imperative that your tank/trough/pit has basic structural integrity.
Excessive movement from foundation, load and temperature fluctuation are the primary causes of cracking. Minimising this movement will contribute to restoring your structure as "fit for purpose". Some options to reduce movement if needed are:
Banding
External reinforcement is placed around the structure at key locations to assist (or take over) from inadequate or decayed reinforcement.
Generally for tanks up to 75,000 litres (15000 gallons) the addition of two hoops of high tensile deformed bar will be adequate if placed around the tank under tension. This is cost effective and can be done with ease with two people. See diagram.
Method
Purchase Y12 bar (or similar) in 6m lengths. Join by welding to achieve correct circumference of tank (2x36mm welds at joins). Weld short length of chain to each end. Wrap around tank, hold together with chain dogs. Using two chain dogs (double dogging), tension bands as much as possible prior to welding band ends together.
Band Placement Guide
Stapling
In some cases it will suit better to staple rather than band. Eg. Troughs, oblong structures or where there is poor access for banding. Staples can easily be made from steel rod (suggest Y12 high tensile) and placed over cracks into holes drilled into the substrate either side of crack.
Method
Cut 12mm bar into 200mm lengths. Bend 30mm at each end to 90 degrees. Drill corresponding holes into structure at slight angle away from crack. Hammer staple in. Render over (filling holes). Angled holes will have a tensioning effect on the bar.
Underpinning
It is important that your structure is well founded. Ideally it will be on a base of compacted crushed rock. If the base has eroded or washed out, it is suggested that you reinstate the missing portion by forcing additional material under the structure. This is known as underpinning. When you have achieved this, it is recommended that the new material is held in by retaining boards, larger rocks or stabilised crushed rock (weak-mix concrete) to prevent washing.
Be sure to call us if you have any questions.
Phone 03 54488680 or 1800 248380
Fax 03 54488650
