Conservation of Heritage Masonry Structures Within Cauvery Basin Waterworks

Conservation of Heritage Masonry Structures Within Cauvery Basin WaterworksSafe & Sustainable Infrastructure

ABOUT THE PROJECT

This project will develop new techniques to repair and rehabilitate heritage masonry.

NOTABLE ACHIEVEMENTS (October 2016)

• Researchers have developed a novel Nanolime material that improve strength and which can be retrofitted to heritage structures more effectively
• The new material has been placed on the KRS dam and is currently being evaluated to ensure effective performance after seasonal water table exposure

PROJECT UPDATE (April 2016)

Researchers have completed a study on the effect of Nanolime on the strength and permeability of lime mortars reinforced with polymeric microfibers. As expected with controlled low strength composites, polymer microfibers improve the strength of lime mortars, both in compression and in tension. However, in what appears to be counter-intuitive, polymer microfibers can increase the permeability in such controlled low strength composites, beyond an optimal dosage. It is seen that although the mean pore size drops with the introduction of microfibers, there is an increase in pore-connectivity in the presence of fibres. Therefore, in comparison with normal strength Portland cement concrete or mortar, a much lower fibre dosage is recommended for superior water tightness. The addition of Nanolime improves water permeability of lime mortar by nearly two orders of magnitude and this works in synergy with microfibers. The innovative mixes developed at the University of Alberta and the National Institute of Engineering, Mysore have been adapted to suit local material availability, especially in the context of waterworks pre-dating the use of Portland cement in India. In the year 2016-2017, field trials are planned to repoint and regrout stone masonry on the century old KRS Dam across the River Cauvery near Mysore, India.

RESEARCH ABSTRACT

The Krishna Raja Sagara Dam was built in the 1920s with stone masonry using a lime-pozzolan binder. These waterworks are accepted as critical heritage infrastructure for the Karnataka State, India which must endure for future generations. Intervention towards repair and rehabilitation of heritage masonry has shown the inadequacy of using modern building materials and binders, specifically Portland cement-based systems, in preserving the integrity of their heritage value. It is clear therefore that a delicate balance is needed between using traditional building materials and modern techniques so as not to disturb their functionality. Hence there exists a tremendous need to understand pre-Portland cementitious systems and tailor modern substitutes for durable repair, especially for their water tightness. Accordingly, in this proposal, using a combination of rheological, mechanical and durability evaluation, the repair systems will be characterized first at the material scale. A shortlist of successful trials will subsequently be tested for system performance and component compatibility in a masonry element. The knowledge gained will be field tested on an aqueduct in the Cauvery Basin that mimics the temperature, humidity and loading conditions typical of the challenges surrounding conservation of the KRS Dam.