Background of Research on Nano Concrete:
Though stone is the strongest constituent of concrete the strength of stone is not evident in compressive strength. It is the bond-strength at transition zone which reflects as the grade strength of concrete. This is evident where, cement is normally increased to upgrade the strength of concrete but not the input of stone. Here the research dimension came into question: “Since stone is the constituent of concrete transition zone do develop surrounding the stone that pronounces the grade strength of concrete. Why not avoid stone so much so the transition zone?” The pursuit of this research though paid dividends where if the control concrete with 350 kg of cement input gives strength of M25-M30, for the same input of cement Nano Concrete has given a strength of over M60.
This wonder product is called No-Aggregate Concrete (NAC), which means a concrete without sand and stone. It is also christened as Nano Concrete since the pore structure in NAC does refined to nano pores as against micro pores common with matrix of the control concrete. The detailed technical note is given below:
Tech. Note on NAC Dec 2015
The Dhwaja Sthambham (the sacred post in front of the temple) of Lord Venkateswara Swamy Temple on the hill, opposite to BHPV Township in Visakhapatnam, has deteriorated due to ingress of moisture that facilitated development of pest. Hence the Punah-Pratishta of this sacred pillar was conducted on 3rd-5th February 2014. This time, the temple authorities desired to make it resistive to pest attach and approached the scientists. the pit, holding the Pillar, is filled with Nano Concrete (NAC) for its characteristic ability in rendering absolute impermeability (27-100 Coulombs) associated with high strength (60 MPa at 28-day and 100-120 MPa at 1-year).
The idea for this research stems out of the practice witnessed at Bangladesh where, in order to meet the need for aggregate of concrete in the absence of hillocks, they break clay bricks in portable jaw crushers. Here emerged the research thought: “while clay bricks of 15-20 MPa could be crushed as aggregate and used in structural concrete, why not NAC stone with its strength of over 60 MPa!”
Exactly at this point of time, NTPC has called for ideas under National Grand Challenge (2019) for Mass Scale Fly Ash Utilisation and this innovation has bagged the 1st Prize. There upon NTPC opted to construct a demo-building totally with NACA concrete for which the inventors have cast over 90 tons of NAC boulders, crushed into 20 & 10 mm aggregate in commercial crusher and supplied for this structure.
Posted in R&D
Tagged FLY ASH, NAC, NACA