Quality Assurance Handbook for Rural Roads Volume-I - pmgsy

Quality Assurance Handbook for Rural Roads
(iii) Organic impurities: Shake the sample with an equal volume of 3% solution of NaOH (Caustic
soda) and allow it to settle for 24 hours. Examine the colour of the liquid above the sand.
Clear or pale yellow colour shows that the sample is tolerably free from organic impurities.
Dark yellow or brown tinge shows that the sand should be washed and tested again. If on
retesting, dark yellow colour persists, the sand should be rejected.
4.4 Cement-Mortar
(i) The cement mortar if unused for more than 30 minutes after addition of water shall be
rejected and removed from site.
(ii) The mix proportion of cement: sand can be checked as follows:
Take about 200 gm of green cement mortar and add 100 ml of water in a measuring jar and
shake the contents well and allow the contents to settle. While the sand gets deposited at the
bottom, cement shall settle above. From the volumes of each, the approximate proportion of
cement and sand can be determined.
(iii) Consistency: Mortar consistency can be checked by the following:
(a) If a small quantity of mortar is dropped from a trowel, the trowel ought to be left
perfectly clean.
(b) A little mortar worked gently in the hands should be easily moulded into a ball; on the
surface of which water would appear.
(c) When the ball is dropped from a height of half a meter (500 mm) on a hard surface, it
must retain its rounded shape.
4.5 Coarse Aggregate
Coarse aggregates shall be hard, strong, non-porous, free from friable, elongated and laminated
particles. They shall be clean and free from clay, coal, vegetable and other organic material.
Two simple tests to check the suitability of stone aggregates are given below:
(i) If the aggregates of a known quantity absorb more than 10 percent of their weight after 24
hours immersion in water, they are considered porous and are avoidable.
(ii) If Mica inclusions persist on the surface, the stone aggregates shall be rejected as presence of
Mica affects durability of concrete.
However, the detailed tests indicated in Table 800.13 are to be conducted before the use of coarse
aggregates in concrete bridge works.
4.6 Cement Concrete
The principal requirements of concrete include workability, strength, durability, impermeability,
and volume changes. Some of the simple tests to determine quality of concrete are described
below:
(i) Consistency: The concrete can be considered to satisfy consistency requirement if an ordinary
iron rammer sinks into concrete mixture by its own weight. It shall run-off a showel unless
showelled very quickly; and shall spread out and settle to a level surface after wheeling for
about 8 m distance in a wheel barrow.
Appendix-1/7