Locally available kaolin has been calcined and used as cement replacing material (CRM) in High-strength concrete (HSC). Total five (05) mixes of concrete have been examined using calcined kaolin (CK) of 0, 5, 10, 15 and 20 by weight of cement. For each mix, compressive strength, splitting tensile strength and flexural strength have been determined by preparing three specimens. The effect of CK on the mechanical properties of HSC has been investigated at age of 7, 28, 56 and 90 days. Multiple linear regressions through least square error have been used to develop the expression and to predict the compressive, splitting tensile strengths and flexural strength of HSC. It has been found that CK as CRM increases the strength significantly. The models may predict the strengths closely match the measurements and optimum replacement of cement by CK. © (2014) Trans Tech Publications, Switzerland.