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With the increasing numbers of PQC Roads across the country, there are various issues in the PQC pavements which are cropping up and repair solution is the need of hour. In this direction STP Limited has come up with lot of new products in last few years for these repairs.
Repairs can be classified into following categories:
Repair Of Minor CracksThese are very low (small) width cracks or hairline cracks. Such cracks generally do not affect the performance of road surface. Thus, these cracks, unless the severity level increases, need not be repaired. Further observe these cracks over a period of time for enlargement.
Medium Cracks (generally 1 to 5 mm wide)If cracks are not moving then a very low viscosity epoxy resin may be used for its repair with or without fine sand to bond the crack faces.
Partial Depth RepairsThe spalling of concrete occurs near the joints mainly due to adjacent slab load transfer related movement at the joint particularly in summer. The spalling will occur frequently in mid slab locations and other locations mainly due to high slump due to w/c ratio, poor construction or failure of earlier done repairs. Spalls are a localized problem and can be easily repaired with partial depth repair methods.
Full Depth RepairsThe full depth repairs are necessitated due to Transverse Crack in slab in full panel width. This crack may be in one lane or both the lanes. The reasons for such crack are:
In all such cases where cracks are more harmful, then the PQC Panel should be examined carefully, if the panel is to be repaired or removed. If it has to be repaired than use the technique of cross-stitching method. However, if that portion of panel is to be removed and then recast the panel as indicated by Removal of Existing Unsound Concrete.
Some Of These Repair Methods Are Described Here
I. Repair by Grouting of Low Viscosity Epoxy Material (ShaliGrout EI)
a. Equipment For Repair Depending upon the method of repair the following equipments may be used.
b. Preparation For Crack Repair
Fix Injection ports (Nipples) of plastic or similar material ie nozzles of 6-8 mm in diameter and 100mm length into the holes. Keep the projection of nozzle outside the PQC to about 20 mm.
c. Repair Procedure
l or similar product of very low viscosity.
d. Finishing Of Repair Surface Of Crack
e. Curing Of Repaired Surface
II. Repair By Stitching Or Cross-Stitching Of Cracks: Cross-Stitching is a repair technique mostly used for longitudinal cracks which are in reasonably good condition. The purpose of cross-stitching is to maintain aggregate interlock and provide added reinforcement for strength. The tie bars used in cross-stitching prevent the crack from vertical and horizontal movement or widening. This technique knits the cracked portions of the slab together and reduces the chances of crack to grow further.
Cross-stitching uses deformed tie bars drilled across the crack at an angle of 30-40 degrees. Deformed steel bars of 10-12 mm diameter are sufficient to hold the crack tightly closed and enhance aggregate interlock. Full depth holes of 18-20 mm diameter are drilled at a pitch distance of 300 mm with offset of about 150 mm from the crack. The holes are drilled alternately from each side of the crack so that it passes through the crack from left to right, while the next from right to left. After drilling, the holes are flushed with high pressure air to clean out any residual dust. Then a high strength epoxy gel adhesive is injected into the hole. Immediately after injecting epoxy, deformed steel bars are inserted into each hole. The crack is sealed at the top with epoxy modified sealant.
III. Surface Repairs Of The Pavements: especially for the areas where aggregates are exposed due to various reasons like after concreting, sudden rain started or due to more tear & wear of concrete: a. A suitable surface repair Mortar (ShaliFix SC 40) may be used followed by wetting of Surface and application of Primer (ShaliSBR Latex). b. Surface shall be cured using a suitable curing Compound/Water curing.
Material that are used in these repairs are:
For further details and live demo please get in touch with STP Limited’s technical team.
For further information,visit: www.stpltd.com
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