3. Use of Fly Ash as a Cementitious Material with Partial Replacement of Cement in Pavement Concrete - PQC

May 2002 to February 2005
Hindustan Construction Co. Ltd (HCC), Mumbai (R,I)

Present Status and Progress
The entire 28 km stretch was completed and is running with satisfactory performance.
In PQC and DLC, HCC was permitted to use fly ash as cementitious material for Satara – Kolhapur – Kagal section of NH-4.

As per Clause SP 16 of the Technical specification following was to be considered:

• Use of fly ash, as cementitious material in the concrete mix was permitted. However, fly ash content in the mix was not allowed to be more than 40% of the total cementitious material. The maximum allowable content of fly ash was limited to 160 kg/m3 of concrete mix.

• Fly ash requirement was as conforming to IS: 3812, Grade I

• Also a relaxation was allowed in such cases where fly ash was used that from 28 days strength, as 56 days strength shall be tested for compliance

Based on the aforesaid specifications, already approved mix designs incorporating fly ash (at different replacement levels from 25% to 40%) were established for the aforesaid project by HCC.
Fly ash improves workability thus reducing the dosage of admixture. Using fly ash to replace cement reduces the heat of hydration in concrete thus reducing the cost of cooling the concrete. All these have a positive financial implication on the overall cost of concrete. More over strong and durable maintenance free roads are the largest benefit to the owner and end-users.

As fly ash contains higher heat factor, it requires less power in concrete making process resulting in substantial saving of power. It leads to reduction in emission of CO2, thus helping the cause of pollution free environment. By reducing consumption of OPC, the rate of depletion of mineral resources required for production of cement can also be reduced.
Fly ash can be used for producing durable, economical and eco-friendly concrete to be laid in pavements and hence, the contractors, clients and engineers must make a joint effort to promote use of fly ash in pavements particularly for sustainable development and durability of roads and structures

With introduction of rigid pavement expressways and highways, quality concrete usage in pavements has become a practice in India. Upgradation of the National Highways in India through the projects initiated by National Highways Authority of India, like, Golden Quadrilateral, East-West / North-South Corridors and the Port Connectivity is in progress. With the boom in the development of this sector, concrete has been extensively used in roads where road packages are already under execution. However, use of fly ash in concrete has been very limited. With the phases remaining to start there is a huge potential to use fly ash and contribute to the cause of sustainable development. About 7000 km of highway is either just taken up or execution yet to begin for development. Even if 30% of its length involves pavement with concrete, the consumption of concrete will be around 10 Million M3. This means that the amount of cement involved only in this concrete is to the tune of 3.6 Million MT. This huge potential if utilized can make construction more effective by being clean and green.
Amdekar H. S., Kulkarni Y. A., Mokal M. P. “Use of Fly Ash in Concrete Pavement” published in Proceedings of International Congress on Fly Ash Utilization, New Delhi, December 2005