1. SCOPE & SIGNEFICANCE:
a) This test method is used to determine the setting time of hydraulic cement by vicat needle apparatus.
b) According to ASTM specification, the initial setting time shall not be less than 45 minutes but in the field we prefer an initial setting of cement not less then 90 minutes.
2. RELATED THEORY:
a) SETTING:
Setting is a physical change & setting process is that process in which its plastic behavior is terminated or finished or lost.
b) HARDING:
Harding is the rate of gain of strength which involves chemical change.
c) INITIAL SETTING TIME:
It is the time from movement when water is adds until the paste seated to the fluid or plastic of the time about 30 minutes.
d) FINAL SETTING TIME:
It is the time elapsed between the initial contact of cement and water at the time when the smaller needle does not leave any impression on the cement paste.
3. APPARATUS:
a) Digital balance.
b) Glass graduates (200 or 250) ml capacity.
c) Vicat apparatus with the plunger end, 10 mm in diameter.
d) Ring vicat mould and containers.
e) Vicat stand.
f) Stop watch.
4. DIAGRAMS:
Fig: 2.1 (Digital Balance)
Fig: 2.2(Glass Graduates 250 ml)
Fig: 2.3 (Vicat apparatus)
Fig: 2.4 (stop watch)
5. MATERIAL:
a) Cement & Water.
6. PROCEDURE:
a) Place the dry paddle and the dry bowl in the mixing position in the mixer.
b) Place all the mixing water in the bowl.
c) Add the cement to the water and allow 30 s for absorption of the water.
d) Start the mixer at low speed for 30 s
e) Stop for (15 s) and make sure no materials have collected on the sides of the bowel.
f) Start mixing at medium speed for (1 min).
g) Quickly form the cement paste into the approximate shape of a ball with gloved hands
h) Putting hand at (15cm) distance, throw the cement paste ball from hand to hand six times.
i) Press the ball into the larger end of the conical ring completely fills the ring with paste.
j) Remove the excess at the larger end by a single movement of the palm of the hand. Place the ring on its larger end on the base of the plate of Vicat apparatus.
k) Slice off the excess paste at the smaller end at the top of the ring by a single sharp- ended trowel and smooth the top. (Take care not to compress the paste).
l) Center the paste under the plunger end which shall be brought in contact with the surface of the paste, and tighten the set-screw.
m) Set the movable indicator to the upper zero mark of the scale or take an initial reading, and release the rod immediately. This must not exceed 30 seconds after completion of mixing.
n) The paste shall be of normal consistency when the rod settles to a point 10±1mm below the original surface in 30 seconds after being released.
o) Make trial paste with varying percentages of water until the normal
p) Consistency is obtained. Make each trial with fresh cement.
7. CALCULATION & RESULT:
READING SCALE
(in millimeter) TIME
(In minutes)
1 40 0
2 40 10
3 36 10
4 35 5
Table 7.1
TOTAL TIME = 25 minutes
Final setting time = F.S.T= 90+1.2(initial setting time)
= 90+1.2(25)
= 90+30
= 120 minutes
8. PRECAUTION:
a) Take 650gm of cement on the scale.
b) Take neither 175ml of water, nor less nor greater than, according to the weight of cement.
c) Take scale on zero before the process.
d) Take an accurate stop watch of good quality.
e) Take clear the instruments, that there is no extra material.
a) This test method is used to determine the setting time of hydraulic cement by vicat needle apparatus.
b) According to ASTM specification, the initial setting time shall not be less than 45 minutes but in the field we prefer an initial setting of cement not less then 90 minutes.
2. RELATED THEORY:
a) SETTING:
Setting is a physical change & setting process is that process in which its plastic behavior is terminated or finished or lost.
b) HARDING:
Harding is the rate of gain of strength which involves chemical change.
c) INITIAL SETTING TIME:
It is the time from movement when water is adds until the paste seated to the fluid or plastic of the time about 30 minutes.
d) FINAL SETTING TIME:
It is the time elapsed between the initial contact of cement and water at the time when the smaller needle does not leave any impression on the cement paste.
3. APPARATUS:
a) Digital balance.
b) Glass graduates (200 or 250) ml capacity.
c) Vicat apparatus with the plunger end, 10 mm in diameter.
d) Ring vicat mould and containers.
e) Vicat stand.
f) Stop watch.
4. DIAGRAMS:
Fig: 2.1 (Digital Balance)
Fig: 2.2(Glass Graduates 250 ml)
Fig: 2.3 (Vicat apparatus)
Fig: 2.4 (stop watch)
5. MATERIAL:
a) Cement & Water.
6. PROCEDURE:
a) Place the dry paddle and the dry bowl in the mixing position in the mixer.
b) Place all the mixing water in the bowl.
c) Add the cement to the water and allow 30 s for absorption of the water.
d) Start the mixer at low speed for 30 s
e) Stop for (15 s) and make sure no materials have collected on the sides of the bowel.
f) Start mixing at medium speed for (1 min).
g) Quickly form the cement paste into the approximate shape of a ball with gloved hands
h) Putting hand at (15cm) distance, throw the cement paste ball from hand to hand six times.
i) Press the ball into the larger end of the conical ring completely fills the ring with paste.
j) Remove the excess at the larger end by a single movement of the palm of the hand. Place the ring on its larger end on the base of the plate of Vicat apparatus.
k) Slice off the excess paste at the smaller end at the top of the ring by a single sharp- ended trowel and smooth the top. (Take care not to compress the paste).
l) Center the paste under the plunger end which shall be brought in contact with the surface of the paste, and tighten the set-screw.
m) Set the movable indicator to the upper zero mark of the scale or take an initial reading, and release the rod immediately. This must not exceed 30 seconds after completion of mixing.
n) The paste shall be of normal consistency when the rod settles to a point 10±1mm below the original surface in 30 seconds after being released.
o) Make trial paste with varying percentages of water until the normal
p) Consistency is obtained. Make each trial with fresh cement.
7. CALCULATION & RESULT:
READING SCALE
(in millimeter) TIME
(In minutes)
1 40 0
2 40 10
3 36 10
4 35 5
Table 7.1
TOTAL TIME = 25 minutes
Final setting time = F.S.T= 90+1.2(initial setting time)
= 90+1.2(25)
= 90+30
= 120 minutes
8. PRECAUTION:
a) Take 650gm of cement on the scale.
b) Take neither 175ml of water, nor less nor greater than, according to the weight of cement.
c) Take scale on zero before the process.
d) Take an accurate stop watch of good quality.
e) Take clear the instruments, that there is no extra material.
