22 USThe test piece is then placed on a dry cloth and gently surface dried with the cloth. It is
transferred to a second dry cloth when the first one removes no further moisture. The test piece
is spread out not more than one stone deep on the second cloth and left exposed to atmosphere
away from direct sunlight or any other source of heat for not less than 10 minutes untill it
appears to be completely surface dry. The sample is then weighed (B).
The sample is then carefully introduced in a 1000 ml capacity measuring cylinder and
distilled water is poured by means of 100 ml capacity measuring cylinder while taking care to
remove entrapped air, untill the level of water in the larger cylinder reaches 1000 ml mark. The
quantity of water thus added is recorded in ml or expressed in gram weight (C).
The water in the larger cylinder is drained and the sample is carefully taken out and dried
in an oven at 100 to 110°C for not less than 24 hours. It is then cooled in a desiccators to room
temperature and weighed (A). The room temperature during the test is recorded.
Apparent specific gravity =A
1000 CWater absorption = BA 100
A Apparent Porosity =BA
100
1000 C
The true porosity shall be calculated from the following formula:
True Porosity =True specific gravity – Apparent specific gravity
True Specific gravityWhere
A = Weight of oven-dry test piece (g)
B = Weight of saturated surface-dry test piece (g)
C = Quantity of water added in 1000 ml jar containing the test piece (g)
rX This test is performed by scratching a stone with knife on Mohs scale.
X This test is performed by breaking the stone with a hammer. Toughness is indicated
by resistance to hammering.
QII hiisyesyx2yp2yxi
The various natural agents such as rain, heat, etc. and chemicals deteriorate the stones with time.
Rain water acts both physically and chemically on stones. The physical action is due to the
erosive and transportation powers and the latter due to the decomposition, oxidation and
hydration of the minerals present in the stones.
e
X Alternate wetting by rain and drying by sun causes internal stresses in the
stones and consequent disintegration.
g e
X In industrial areas the acidic rain water reacts with the constituents of stones
leading to its deterioration.