Per §7.4 (Bond Strength), the bond strength between concrete and steel reinforcement remains approximately linearly proportional to the compressive strength of concrete only UP TO a compressive strength of about:

1. §7.4 reads: 'Bond strength is found to be approximately linearly proportional upto a compressive strength of 20 N/mm². For higher strength of concrete the increase in bond strength becomes progressively smaller and eventually negligible.' 2. Steam-cured cement gives a gel of about 1/20 the specific surface — hence poor bond. _Source: IGNOU ET-522 Block-2 Unit-7 Strength of Concrete, §7.4, p. 54_