BS 8007 has recommended using grade C35A concrete with have limitations in the cement content and the water-cement ratio. The characteristic strength of the concrete has specified as 35 N/mm2. The minimum cement content is recommended as 325 kg/m3 and the maximum water-cement ratio should be 0.5. As per the BS 8110, the minimum cement content is 300 kg/m3 and the maximum water-cement ratio is 0.55.
Further, BS 8007 states the maximum cement content for reinforced concrete of 400 kg/m3 for ordinary portland cement or cement containing gbbs, or 450 kg/m3 cement containing fly ash. For prestressing concrete, quantity should be increased to 500 kg/m3 and 550 kg/m3 respectively.
The use of the grade C35A concrete improves the permeability and reduces the heat of hydration. Therefore, it improves the durability of the concrete.
