Micro Concreting and Repairing Works of RCC Slabs, Columns and Beams
Repairing of RCC slabs, columns and beams are done when concrete is too deteriorated for epoxy injections to work. And the damaged concrete is to be removed and replaced with fresh concrete.
How is Micro concreting and repairs of RCC slabs and Beams done?
All safety measures concerning the stability and integrity of the structure have to be in place before attempting any removal of the damaged concrete.
First of all, chip and remove all damaged plaster, debonded concrete from the RCC column beam and slabs by manual or mechanical means and the corroded reinforcement bars are exposed. The concrete must be removed completely from the reinforcing bars, providing at least 2cm clearance on all sides.
The reinforcing bars are thoroughly cleaned and inspected; the cross-sections are verified with the original cross-section of the steel for deterioration. If a significant reduction is noticed, new reinforcements are added to the existing steel reinforcements before concreting.
The additional reinforcement bars are drilled and fixed in position using Lok-Fix or similar epoxy sealants.
After a thorough cleaning of the reinforcements, a suitable ( non-toxic preferred) rust remover or rust converter is applied. For example - Rebaklense RR, of M/s Fosroc Chemicals India Ltd or Amandur, manufactured by GK Technocom.
Some removers include a feature to prevent flash rusting which can occur to exposed bare metal.
Once rust is removed, the item is rinsed thoroughly with water and dried. Nitozinc Primer is applied over all the exposed steel reinforcement rods. Then the necessary watertight shuttering is done using good quality marine plywood.
An epoxy bonding agent like Nitobond EP is applied to the old concrete surface. It is for bonding new cementitious materials to existing cementitious surfaces. The new concrete should be added within 3 -6 hours of bonding agent application, i.e while it is still in a tacky state.
If micro concreting materials like Renderoc RG is used it shall be mixed with 12mm down coarse aggregate and specified quantity of water and mixed using power-operated slow speed stirrer.
This mixture can then be poured into the formwork to an average thickness of 85 mm for beam and column.
The next step is plastering the above newly repaired surface with Nitobond SBR which is a polymer bonding agent cum cement mortar/concrete modifier with an average thickness of 20 mm. After which curing compound,
CureCocure WB is applied with a painting brush, to get a complete covering to the micro concrete. This curing compound can also be applied immediately after de shuttering for better results.