1. REQUIREMENTS
a) Specified minimum strength = 20 N/Sq mm

b) Durability requirements
i) Exposure Moderate
ii) Minimum Cement Content = 300 Kgs/cum

c) Cement
(Refer Table No. 5 of IS:456-2000)
i) Make Chetak (Birla)
ii) Type OPC
iii) Grade 43

d) Workability
i) compacting factor = 0.7

e) Degree of quality control Good
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CONCRETE MIX DESIGN (GRADE M60)

(a) DESIGN STIPULATION:-
Target strength = 60Mpa
Max size of aggregate used = 12.5 mm
Specific gravity of cement = 3.15
Specific gravity of fine aggregate (F.A) = 2.6
Specific gravity of Coarse aggregate (C.A) = 2.64
Dry Rodded Bulk Density of fine aggregate = 1726 Kg/m³
Dry Rodded Bulk Density of coarse aggregate = 1638 Kg/m³
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Instant Concrete road repair solution
By Mr. Mangesh Dhamele
Dy. Manager. Choksey Structural Engineering

INTRODUCTION
The Durability of road structures depends on the quality of its maintenance & minor renovations. Maintenance keeps the roadway safe, provides good driving conditions & prolongs the life of the pavement, thus protecting the road investment.

Currently in India more than 2000 km of concrete road is in the operation since last few years. Most of the projects completed by NHAI, MSRDC and other state government authorities. Though the quality & procedural aspects, specifications / guidelines clearly mentions in IRC, MoRTH, but still we observes that various minor cracks, potholes and joints edge spalling in the PQC due to various factors which requires maintenance. Maintenance includes the prompt sealing of cracks & filling of potholes to prevent water entering through the surface.

Repairs and rehabilitation of concrete roads are required to have a smooth riding quality as well as avoid inconvenience causing to the vehicles. We need to have a durable repair products to avoid of cost of various factors like :

a) Diverting the traffic for repairs
b) Inconvenience to the traffic
c) Repeatedly cost of repairs by using conventional methods.
REQUIREMENT OF THE PRODUCT FOR REPAIRS OF CONCRETE SURFACE
1) Resistant to abrasion and weather conditions.
2) Skid resistance, non-reflective finish with colour matching with concrete
3) Fast setting so that repaired patch can accept traffic in as little as one hour.
4) Resistance to deicing chemicals & various industrial chemicals
5) Jet fuel and other fuel resistance like petrol, diesel, oil and grease.
6) Good bond between concrete and steel, Impermeable.
7) Flexible enough to accommodate anticipated expansion and contraction.
8 ) Ultra-violet Resistance, User friendly and paintable.
9) Manufacturer of the material should have the good track record & experience in such kind of repair products.
10) Economical

CONVENTIONAL METHODS OF REPAIR CONCRETE STRUCTURES
Though we have developed our specifications and guidelines to lay the PQC up to the international standards, but now considering the deteriorating conditions of the concrete roads, we have to develop the good specifications and proper guidelines / application systems to repair and rehabilitation of concrete surfaces permanently.
Currently following are the various conventional methods we are using for the repairs of concrete road.

1) Repair by fast setting water based cement compound
2) Repair by epoxy mortar, which is non-UV Resistance material.
3) Repairs of PQC by laying bituminous concrete or bitumen in the cracks & potholes.
4) Other conventional methods

NEXT GENERATION FAST SETTING COMPOUND DELPATCH
In 1983, The D.S. Brown Company introduced Delcrete^TM Elastomeric Concrete. The rigid, yet flexible connection Delcrete^TM provided between steel and concrete soon made it the premier solution for bridge and highway spall repair as a permanent repair solution for high performance pavements, which would offer minimum downtime and, at the same time, limit exposure of work crews to traffic.

D.S. Brown engineers formulated Delpatch^TM Elastomeric Concrete from the original Delcrete^TM product. Delpatch^TM a new generation of elastomeric concrete has two main uses. First, it is an excellent patching material for cracks and spalls on airport runways and highways. Second, Delpatch ^TM provides an easy to use solution in retrofitting airport runways with lighting & bridges with expansion joints.

Delpatch vs Others

A. Existing condition before repair:

After construction of PQC, various cracks has developed due to various reasons like

a) Settlement of the sub-base
b) Surface cracks due to high wind-velocity during laying of PQC
c) Late initial cut of PQC

We have found that various major potholes, cracks and joint spalling at various junctions of Jogeshwari Vikhroli Link Road, Mumbai and at Mumbai international airport wherein contractor or government authorities are unable to repair by epoxy, as epoxies are not UV Resistant or by cementatious material and also they are unable to hold the traffic for conventional repairs.

Following are the few photographs shows deteriorating concrete surfaces and cracks, which requires repair on priority basis to avoid further damage to take place.

Conclusions:
We can conclude with the recommendation of Delpatch should be the material which can be used for such kind of repairs which are critical and important.
This material can be used for following repairs and rehabilitations of:

1. Concrete roads & patches including underpasses
2. Expressways, aprons of airports, where we can not hold the traffic for the sake of repairs of the deterioted patches
3. Nosing wheel areas, where the loads expected more than 150 - 200 tonnes per 2 sq.ft. Area
4. Replacing the expansion joints - which we can complete in one night, actually such kind of practices adopted in US, and other part of the world, where replacement of expansion joint is essential but at the same time, contractor does not have the permission to hold the traffic for longer time.
5. Heavy Industrial floors, shop floors.
6. Light conduits to put lights on the runways.
7. All the surfaces exposed to the sunlight.
8. A top surface of spillways, bucket area of Dams, where water pressure is more, & surface is exposed to sunlight.

The mix design of Mix Design For M35 Grade Of Concrete for pile foundations provided here is for reference purpose only. Actual site conditions vary and thus this should be adjusted as per the location and other factors.

Grade of Concrete : M35
Characteristic Strength (Fck) : 35 Mpa
Standard Deviation : 1.91 Mpa*
Target Mean Strength : T.M.S.= Fck +1.65 x S.D.
(from I.S 456-2000) = 35+ 1.65×1.91
= 38.15 Mpa
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Filler materials are gaining widespread popularity and becoming very important because they help in increasing some of the mix properties and also lower the usage of binder which is usually more expensive
Here is the table showing some common filler materials along with binders