Surface index
Periodontal index used to measure the presence of calculus (supra- and subgingival) on the four mandibular incisors.
1)The workability of concrete depends on surface area of the aggregate. Consideration of specific surface sometimes gives misleading results of the “Workability”.
2)Thus surface index has been introduced. It is an empirical number related to the specific surface of the particle with more weightage given to finer fractions.
3)The total surface index of a mixture of aggregate is calculated by multiplying the percentage of material retained on its sieve by the corresponding surface index and to their sum is added a constant of 330 and the result is divided 1000.
