1964_BUILDING_(CONSTRUCTION)_REGULATIONS — Page 121

1985 Ed.]

Building (Construction) Regulations

[CAP. 123

B 121

[Subsidiary]

PART III

CONCRETES OF QUALITY A

7. (1) (a) Preliminary tests should be made for concrete of Quality A.

(b) 6 cubes shall be made for each test and 3 of these cubes shall be tested at the age of 7 days and the remaining 3 at 28 days.

(2) (a) The works resistance to crushing of Quality A concrete shall be determined from sets of 3 consecutive cubes from the same grade of concrete tested at the same age.

(b) For each age at which the resistance to crushing is to be determined at least 3 cubes shall be made for each grade of concrete on each day it is used.

8.

The specified resistance to crushing for the appropriate grade shall be deemed to have been obtained if—

(a) none of the individual crushing resistances is less than the specified resistance to crushing; or

(b) if the average resistance to crushing of each set of 3 consecutive cubes is not less than the specified resistance and the difference between the greatest and least result of the set is not more than 20 per cent of that average.

PART IV

CONCRETES OF SPECIAL MIXES

Number of cubes for Quality A concrete.

Standard of acceptance for Quality A concrete.

9.

(1) (a) Preliminary tests shall be made for special mixes.

(b) For each preliminary test 6 cubes shall be made from each of 2 batches of the same mix proportions.

(c) 3 cubes of each set of 6 cubes shall be tested at 7 days and the remaining 3 at 28 days.

(2) (a) The works resistance to crushing of concrete of special mixes shall be determined from a set of 3 cubes tested at the same age.

(b) For each age at which the resistance to crushing is to be determined, at least 1 set of 3 cubes shall be made for each grade of concrete on each day it is used and if more than 75 m3 of any grade is used in a day 1 set shall be made for each 75 m3 or part thereof.

10. The specified resistance to crushing in accordance with Table VI shall be deemed to have been attained if-

(a) none of the individual resistances to crushing is less than the specified resistance to crushing; or

(b) the average resistance to crushing of each set of 3 consecutive cubes is not less than the specified resistance to crushing and the difference between the greatest and least result of the set is not more than 20 per cent of that average, provided that if individual cubes from 2 consecutive sets fall below the required resistance to crushing the mix shall be adjusted to give a higher strength so that not more than 1 set in 3 consecutive sets shall contain individual results lower than the specified resistance to crushing.

PART V

CONCRETES OF DESIGNED MIXES

11. (1) (a) Preliminary tests shall be made for designed mixes.

(b) For each test 6 cubes shall be made from each of 3 batches of the same mix proportions.

Number of cubes for concrete of special mixes.

L.N. 294/76.

Standard of acceptance for preliminary and works tests of concrete of special mixes.

Number of cubes for concrete of designed mixes.