Question

Metalling of road usually consists of ______ layers of coats.

(a) 5

(b) 3

(c) 2

(d) 6

This question was addressed to me in final exam.

My question comes from Estimate of Metalled Roads topic in section Road Estimating, Sanitary and Water Supply Work of Civil Engineering Drawing

Answer 1

Correct choice is (b) 3

Easiest explanation: The soiling coat, inter coat and top coat. The metal may be stone ballast, brick ballast, kankar, etc. The inter coat and top coat are made with 12 cm (4 1/2 ”) thick layer loose compacted to 8 cm (3”). The soiling coat may be of brick flat or brick on edge, or of stone boulder or of same type as for the inter or top coat if the sub-soil is good, or may be of greater.  The top or wearing coat may also be of cement concrete bituminous.