The Smart City project started in Belagavi early in 20l7 after being selected as one of the first 20 such projects in India, winning a contest between all the major cities in the country. However, for various reasons, Major of the works are in unfinished condition and completed project’s has reached shabby condition.
Smart City has laid concrete from Vantamuri slum to Harsha Hotel and International Cricket stadium road are now having big cracks in which slabs are getting seperated. To tackle this issue, Smart City has gone for ‘Slab Stitching technique’
Repair By Stitching or Cross-stitching of Cracks :
What is Stitching of Concrete slab ?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 silicon / epoxy modified sealant.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.
Why Concrete Cracks :
Concrete Cracks First it is necessary to understand why the concrete cracks. There can be many reasons why the concrete cracks. These need to be understood from its reaction and setting pattern point of view. The main reason is improper concrete mix design and laying / jointing practice related to the inherent nature of concrete to change volumetrically due to moisture, reaction and thermal effects etc. The incidence of cracks can be minimized by improving concrete mix design, laying time weather condition and jointing practices with timely saw cutting and properly managed curing.
Concrete roads, properly designed and constructed, should require little, if any, maintenance over its design life. Still, proper and timed maintenance may extend the life of the pavement even beyond designed service life. Concrete pavements undergo stress and strain due to traffic and climatic effects. However, as long as sub grade is properly compacted, any variation/change in support (due to moisture-changes) has little effect on performance. Proper weather during construction and laying / jointing practice will eliminate most premature distresses. Otherwise, some shrinkage cracking may appear before the road is opened to traffic. Normally, there is no reason why a concrete road should not perform well during the designed life span if properly laid and cared through maintenance.