Specification Part 3 - Road & Bridge Works - Urban Administration ...

401. GRANULAR SUB-BASE
401.1. General
(i) Granular sub base shall consist of laying and compacting well-graded material on previously prepared subgrade
with these Specifications.
(ii) The material shall be laid in layer or in layers as sub-base according to the requirement and according to the
lines, grades and cross -sections shown on the approved drawings or as directed by the Engineer in charge.
401.2. Materials for granular sub base
401.2.1.
(a) The natural sand, moorum, gravel, crushed stone, or combination thereof as required shall be used for
granular sub base.
(b) Materials like crushed slag crushed concrete, brick metal and kankar may be allowed only with the specific
approval of the Engineer in charge.
(c) The material shall be free from organic or other deleterious constituents.
(d) The granular sub base material shall be conform to one of the three grading given in Table 400-1.
401.2.2. Physical requirements of granular sub base material:
(i) The material shall have a 10% fines value of 50 kilo Newton (KN) or more when tested in compliance with
BS:812 (Part 111).
(ii) The water absorption value of the coarse aggregate shall be determined as per IS: 2386 (Pan 3).
(iii) If this value is greater than 2%, the soundness test shall be carried out on the material delivered to site as
per IS: 383.
(iv) For Grading II and III materials, the CBR shall be determined at the density and moisture content likely to be
developed in equilibrium conditions which shall be taken as being the density relating to a uniform air voids
content of 5 %.