As the world economies shift to support the United Nations sustainable development goals, new cement manufactures have entered into the Kenyan market producing brands of ordinary Portland Cement meeting the minimum requirement of the Kenya Bureau of Standards. The variant parameter in this brands is the chemical composition of the cement Brands. The aim of this research was to establish the relationship between the cement Brand and the Critical penetration depth of rust and their role in the durability of the reinforced concrete structures. To achieve the desired objective three cement brands out of six brands manufactured in Kenya; CemX, CemY and Cem Z of ordinary Portland cement with compressive strength 42.5N/mm2 were sourced from a wholesaler for the study. Other concrete constituent materials; fine and coarse aggregates and steel were obtained from the local Kenyan market. This research was conducted at the University of Nairobi Structures/ Concrete laboratory and the State Department of Infrastructure in the Ministry of Transport, Infrastructure, Housing and Urban Development of the Government of Kenya. The physical and chemical properties of the materials were investigated for compliance to relevant applicable British and Kenyan standards and if they met the acceptable criteria. Concrete of characteristic strength of 25N/mm2 derived from the DOE method was used. Concrete materials were batched by weight and mixed by a lab electric pan concrete mixer in batches of 0.009 m3 .The concrete batches were tested for consistency by the slump and compaction factor tests. For each brand of cement 9 cubes of 150mmx 150mm x 150mm for compression test, 9 cylinders of 150mm x 300mm for tensile strength and 9 cylinders of 150mm x 300mm for accelerated corrosion test were cast. After 24 hours the cast specimens were demolded and immersed in curing tanks for 27 days. Specimens for compression and tensile test were tested at 7,14 and 28 days while the specimens for accelerated corrosion were immersed in a 3.5% industrial sodium chloride solution under 6V. The accelerated corrosion specimens were monitored for onset of cracks and stopped when the cracks were 0.1mm in width. From the results in the research, the different Kenyan selected cement brands linearly correlate with the critical penetration depth of rust and the rate of corrosion for the evolution of 0.1mm crack width and this is attributed to their chemical composition.