Pothole Repairs – A Concrete Solution to a Flexible Problem

Defining the challenge

Flexible pavements have a tendency to deteriorate in rainy season, causing severe inconvenience to the society by way of reduction in traffic speed, rideability, vehicular safety and wear and tear of automobiles. Generally speaking, potholes are voids on the road surface where pieces of the pavement become dislodged, especially during rainy season. Statistics reveal that apart from being acute inconvenience to society at large, potholes lead to many road accidents and deaths. Areas in which many potholes occur may have underlying fundamental problems such as inadequate drainage, pavement strength, or sub-base layer problems. Potholes are caused by a constant dry-wet-hot-cold weather change and regular stress on asphalt streets from traffic flow. These combine to create small cracks in the asphalt, which lets dirt and water from rain to get into the gravel and dirt underneath. 

Repair Mechanism

Ideally, the repair of deteriorated pavement should be accomplished with minimum expense and with the least possible traffic disruption. There are many obvious challenges which impede the effectiveness of repair process and effectiveness. Obviously ineffective repair leads to repetitive maintenance costs and inconvenience during every rainy season. It is not possible to totally stop the traffic movements in the affected roads altogether to conduct the repair. The potholes are often wet and muddy. Total cleaning before applying repair material would be a practical impossibility. There is a balance between allowing the repair work to develop sufficient strength before opening traffic and time of closure of roads. Assuming that repair work could be rapidly done despite above constraints, still the repaired layers would often not resolve the underlying root cause of the damage. Pothole patching is the repair of severe, localized distress in asphalt-surfaced pavements. This maintenance activity is generally intended to be a temporary repair. Full depth reconstruction of the distressed areas is necessary for a permanent repair in most instances. Semi-permanent repair technique for potholes would involve removing water and debris from the pothole before placing repair material. Once the pothole has been cleaned, the edges of the distress are straightened using a pavement saw, jackhammer, milling machine, or similar equipment. After the edges have been straightened and are in sound pavement, the mix is placed. The patch is compacted using a single-drum vibratory roller or a vibratory-plate compactor.

Available techniques

Currently adopted processes as well as recently developed new imported solutions have also failed to fully deliver the intended repairs to the best and optimized satisfaction. Use of hot mix overlays has been the most common approach to the pothole problem. Despite of its relative low initial repair cost, this method is restricted in its applicability during the rainy season itself and also in terms of longevity of the repair work itself. Throw-and-roll procedure that needs to be adopted while using this solution at best leads to temporary repair work. In this methodology the quality of the repaired pavement is often very dependent on level of effort at the time of repair work. In order to achieve semi-permanent repair, the prior painstaking preparation, edge-straightening and compaction of the pothole is very essential. Added to that, the usage of machinery like rollers can further reduce need for re-patching the repaired pavement.

Recently, there have been introduction of imported technologies involving chemically activated cold bitumen based mixes. Though this repair method seems to have longer term strength and improved effectiveness of repair works, these also require prior preparation of affected areas to be effective in the long run. Added to this, the cost of such materials is exorbitantly high. For such expensive methods to have reasonable value to the refurbishing process, a more scientific approach towards performance testing of repair works alongwith knowhow on acceptance and compatibility testing will need to be developed. Otherwise, the experimentation cost of the repair before having a long term database of field performance and consistency would deplete huge funds from municipal corporations.

Thinking out of the box

There is a clear need to arrive at some sort of repair material which solves the current issues effectively. What would be the characteristics required in that dream repair solution? Such repair process would be expected to be quick in execution in the operating roads without disturbing much traffic. That would mean that the material should not be too sensitive to condition of pothole, thereby working on both dry and wet conditions. The effort involved in laying of the material should be less and time taken should be small. This would require the material to have some kind of self compacting and flowing characteristics. For the strength performance of the overlay, there needs to be good bonding with the existing old asphalt or concrete pavement. The repaired patch should allow early traffic movement. Considering huge variations in pothole sizes and depth, it should be possible to use small scale and large scale repairs. Moreover, the repaired section should be able to take heavy loads, have a longer life. The engineering properties of impermeability, toughness and abrasion resistance would definitely be appreciated. The combination of such characteristics from one material and process almost seems like a difficult dream to be achieved. Is there such a solution possible?

A team of concrete technologists at the Ready Mix Concrete division of UltraTech Cement spent their major research manhours looking for such a material and process that could achieve such a dream. The findings of this technological elect have led to field applications which seem to be fulfilling this dream. The research points towards superiority of cement based solution for this engineering challenge.  It has been observed that the cement bonds well with both asphalt and concrete. Concrete as a material offers versatility and agility enough that its properties can be modified using speciality chemicals to achieve desired characteristics. It can be adapted to wet, dry and semi-wet process. It is a durable material, can be produced locally. It is easy to handle, without any safety hazards. Based on its research, two kinds of solutions have been recommended, both having fair degree of longevity. The difference of the two processes pertains primarily to the extent of existing damage to the road section.

Metamorphosis of concrete

For the areas where the damages are intermittent and cover multiple lanes, the newly developed UltraTech RapidPave is a Cement Based Metamorphosing Cold Rolled pothole repair solution. It can be brought to the site in various forms of packaging starting from 30kg buckets to 3 to 4 tonnes in truck mixers. Except for minor brooming to remove the mud from the potholes, not much preparatory work is required. So, the traffic diversion would be required literally during only that time when potholes are being patched. The accumulated water in the potholes serves as a part of the hydrating activator for this material. Various other specialized chemical admixtures pre-blended in this concrete add high early hardening strength, toughness and bonding ability in this material. As a result the repaired patches can be opened to traffic within half an hour. The material has been designed to be complemented by the movement of vehicles over the repaired area. The pilot tests of this material have been made in many potholes with grandly successful results.

Thin, white, but hard – UltaThin White Topping

For areas too large to be economically repaired by hand with a small crew, cement based overlay topping is the second solution for this problem. The UltraThin white topping, designed as a high performance concrete, also has the above technical advantages. It does, however, commit a considerable investment in labor, equipment, and materials. Its application requires a considerable degree of skill, coordination, and planning. All loose, broken asphalt is to be removed and replaced. Any deep ruts, depressions, or humps are pre-leveled in advance of the overlay so that the overlay may proceed efficiently. The finishing is done using mechanical pavers. This method leads to permanent repair of the section, even though it may take 3 to 5 days to open the repaired lane for traffic movement.

Taking the Technology to the Road

At Kharghar, Navi Mumbai, on August 8, 2017, A team of concrete experts, a transit mixer loaded with some new concrete based material and some CIDCO officials gathered around a severely damaged intersection near sector 5 of Kharghar node to validate this emerging technology. In about fifteen minutes of discharging this unique concrete and leveling, the hollows were fully leveled. Magically, another fifteen minutes later, cars and auto-rickshaws were seen moving over the level road. ‘Rapid Pave’ is said to be “designed to work in the imperfect environment that exists around these typical deteriorated roads.” The superiority of this method comes from the fact that it uses puddled water itself for its hardening and develops high resistance very quickly. It was observed that this concrete uses its environmental conditions and traffic movement over it to become stronger by the passing hours. Interestingly, the material adapts itself to the shape of the puddle and profile of the road.

On field, the repair work was carried out quickly without bringing any huge machinery or causing long traffic obstructions. The vehicles were welcomed within fifteen minutes to ride over the repaired section. The observations the day after validate that the road has been already used for the full day with unhindered traffic movement without any signs of distress. Finally, the gods of concrete have risen up to take on the demons of puddles and potholes.

As a conscientious and technologically forerunner organization committed to providing practically technical solutions to the needs of the society UltraTech Cement is committed to offer these products and demonstrate to the engineering community that with the use of local knowledge and resources new innovative materials can be used to arrive at better solutions indigenously. Let us together aim to create a city completely free from the menace of potholes. We are ready to extend all our support to various civic bodies in the city and the country to make the product available for these repairs as rapidly as the work can be planned. Some civic authorities are contemplating such discussions to take this further so that this metamorphosing solution to the pothole puddle can be utilized to bring ease to the public on the roads.