Ben W James, CEO & Co-founder, Global Road Technology, explains the different types of stabilisation techniques that need to be adopted in challenging rural areas, sub-Himalayan regions and north-east states.
The Indian road sector has undergone phenomenal growth over the last decade and is growing exponentially now due to the new government's focus on the sector. The pace of road construction is even higher in rural areas, sub-Himalayan regions, international border areas and north-eastern (NE) states, as part of providing better connectivity and access for defence requirements.
Accordingly, soil/aggregate requirements for infrastructure, especially roads, has increased and reached a level where availability of these materials has become a major challenge. Non-availability of suitable soil and aggregates has made projects unviable and cost prohibitive. These factors have delayed several important projects and are even blocking development in certain aggregate deficient regions - predominately in the NE.
Aggregate scarcity will increase further as part of the government's environmental conservation rules and restrictions on quarry activities. Apart from this, road projects in NE states and sub-Himalayan regions have many other engineering and financial challenges; a few of them have been itemised below:
Considering all the factors mentioned above, 'Cold-In-Place-Recycling (CIPR)' and different types of stabilisation techniques will need to be adopted in these challenging areas.
The stabilisation of soil/aggregate is being used worldwide towards optimal usage of the threatened reserves of the same. Though soil stabilisation exists in Indian codes, the concept is yet to be exploited on the ground to aim at critical mass. The concept of CIPR has recently been incorporated in IRC-37(2012), the CIPR and Cement Treated Base (CTB) has been approved by the National Highways Authority of India (NHAI) in a few projects, but is yet to be applied as general practice.
Soil/aggregate stabilisation and CIPR provide a comprehensive solution for rehabilitation of existing road networks and greenfield road construction, that will suit the requirements of the sub-Himalayan and NE regions.
Major components of road stabilisation technology
The road stabilisation process can be divided into three major components: Design Process and codes: Stabilisation and CIPR requirements in Indian design codes have been adopted from AUSTROADS and need further updating with respect to gradation requirements of materials to be stabilised. The material requirements and envelope shall include larger-size particles and shall be flexible as soon as strength requirements are met. This particular modification will allow engineers to utilise existing materials to a large extent up to GSB layers. This will also allow usage of locally available marginal materials. Specialised laboratory equipment are also required to be developed in India; currently these lab equipment are being imported at high cost. Stabilisation agents (materials): The stabilisation process can use a wide range of stabilisation agents, i.e., soil-aggregate mix, lime, cement, fly ash, foundry sand, slag, foamed bitumen, emulsion, polymers and other proprietary chemical stabilisers.
Stabilisation equipment: Specialised heavy road recyclers capable of cutting existing soil/aggregate/asphalt, mixing in place, adding water and other stabilisation agents as per requirement, speed independent stabilisation agent spreader (cement, lime, polymer, etc.), heavy padfoot rollers (20 t static and 40 t dynamic capacity) and pneumatic tyre rollers are essential components of the stabilisation process in general.
Advantages of soil/aggregate stabilisation and CIPR tech Major advantages of using soil/aggregate stabilisation and CIPR technology are as follows: