Question

Which ASTM cement is most appropriate for the following construction applications? What types of mineral and/or chemical admixtures could be used for each application? Give detailed reasons for your choices.

• Construction of a bridge pier in the sea.

Answer 1

Answer- For the construction of bridge pier in the sea Sulphate resisting cement and super sulphate cement is used. For manufacturing of sulphate resisting cement clinkers of Portland cement is grinded with gypsum.

Manufacturing of super sulphate cement is done by grinding Portland cement clinkers with granulated slag and burnt gypsum. The approximate quantity of the ingredients are - Portland cement clinkers- 5-6%. Granulated slag- 80-90%. Burnt gypsum- 10-15%

Sea water is salty in nature which attack easily on concrete surface. So sulphate resisting cement is used to save the concrete from salt.

Chemical admixtures are used to reduce the quantity of water in concrete for making uniform cement distribution. It makes concrete workable at low water cemet ratio. If more than two admixtures are used its compatibility with other ingredients should be checked such that there should be no chemical reaction in between them. Admixtures containing chlorides are not used.