BS 8007 recommends the use of grade C35A concrete with restrictions on cement content and water to cement ratio. The characteristic strength of concrete is given as 35 N/mm. 2 The recommended minimum cement content is 325 kg/m 3 and the maximum water-cement ratio must be 0.5. According to BS 8110 the minimum cement content is 300kg/m 3 and the maximum water-cement ratio is 0.55.
Furthermore, BS 8007 sets the maximum cement content for reinforced concrete at 400kg/m. 3 for ordinary Portland cement or cement with GBBs or 450 kg/m 3 Cement with fly ash. For prestressed concrete the quantity must be increased to 500 kg/m 3 and 550 kg/m 3 respectively.
The use of C35A grade concrete improves permeability and reduces heat of hydration. This improves the durability of the concrete.
