STANDARD CONSISTENCY AND SETTING TIMES TEST OF CEMENT || Kathmandu University Syllabus

Kathmandu University Civil Labs

STANDARD CONSISTENCY AND SETTING TIMES TEST OF CEMENT

OBJECTIVE:

To determine: i) Standard Consistency ii) Initial and final setting times of a cement sample

APPARATUS REQUIRED:

1) Vicat apparatus with Vicat Plunger (10±0.05mm diameter)

2) Vicat needle ( c/s area 1mm2 with flat end needle for initial setting time and circular, c/s area 1mm2

with annular attachment at the end for final setting time)

3) Vicat Mould

4) Gauging trowel

5) Measuring jar

6) Weighing balance

7) Stopwatch

8) Glass base plate

THEORY:

The amount of water needed to prepare the plastic mix is known as the consistency of cement. The

amount of water used in hydrating cement affect setting time (more water, more time needed for

setting).Also, the different batches of cement differ in fineness, pastes with the same water content may

differ inconsistency when first mixed. For this reason, the consistency of the paste is standardized by

varying the water content until the paste has a given resistance to penetration when it is first mixed.

Standard consistency of cement paste is defined as the consistency which will permit the Vicat plunger to

penetrate to a point 5 to 7 mm from bottom of the Vicat Mould. When testing a Portland cement it is

necessary to carry out the trial mixes until a mix of the required consistency is obtained. The quantity of

water required to produce a paste of standard consistency is needed for the determination of the water

content of mortar for tensile test, soundness test and setting time tests.

It is essential that cement set neither too rapidly nor too slowly. In the first case, there might be

insufficient time to transport and place the concrete before it becomes too rigid. In the second case too

long a setting period tends to slow up the work unduly, also it might postpone the actual use of the

structure because of in adequate strength at the desired age. When water is added cement paste gradually

becomes less plastic, hard and stiff, which is known as the setting. Two periods of times are used to assess

the setting behaviour. These are called the initial setting and the final setting time. During initial setting

time cement loses its plasticity and do not reunite while during final setting time cement attains

sufficient hardness and strength and becomes stiff. Initial setting time helps in estimating the time

available for mixing, transporting, placing and shaping the cement paste. It should not be confused with

hardening, which refers to the gain in mechanical strength after the paste has solidified. The setting time

measures the time taken for the cement paste to offer a certain degree of resistance of penetration of a

special attachment pressed into it.

PROCEDURE:

A) Standard Consistency

i) Take 400 gm of cement for one mould and prepare a paste of the cement with a weighed

quantity of water, taking care that the time of gauging is not less than 3 minutes and not more

than 5 minutes.

ii) Gauging time is counted from the time of adding water to the dry cement until commencing

to fill the mould. Fill the Vicat mould with this paste, the mould resting upon non-porous

plate.

iii) After completely filling the mould, smooth off the surface of the paste, making it level with

the top of the mould. The mould may be slightly shaken to expel air.

iv) Place the test block in the mould with the non-porous plate resisting under the rod bearing the

plunger. Lower the plunger gently to touch the surface of the test block and quickly, release,

allowing it to sink into the paste.

v) Prepare trial test specimen with varying percentages of water (firstly at an interval of 4%,

that is of 20%, 24% and 28% and then at an interval of 1 % and 0.25% between the

percentage range determined by the previous test) and test as described in step (i) to step (iv)

until the amount of water necessary for making up the standard consistency as defined is

found.

B) Initial and Final Setting Time

i) Take 400 gm of cement and prepare a neat cement paste with 0.85P water by weight of

cement. where P = standard consistency of cement as found in (A).

ii) Gauge time is kept between 3 to 5 minutes. Start the stopwatch at the instant when the water

is added to the cement.

iii) Keep the Vicat mould in the non-porous glass plate and fill the cement paste in it.

iv) After completely filling the mould, it should be shaken slightly to expel the air.

v) Smooth off the surface of paste making it level with the top of the mould.

vi) For the initial setting time, place the test block and the non-porous plate under the rod bearing

the needle having 1 sq. mm. cross-section.

vii) Lower the needle gently till in contact with the test block and quickly release allowing it to

penetrate in to test block.

viii) In the beginning, the needle completely pierces the test block. Repeat this procedure until the

needle fails to pierce the block for about 5 mm measured from the bottom of the mould.

ix) The period elapsing between the time when water is added to the cement and the time at

which the needle fails to pierce the test block by about 5 mm is the initial setting time.

x) For the determination of the final setting time, replace the needle of the Vicat apparatus by the

needle with an annular attachment.

xi) The period elapsing between the time when the water is added to the cement and the time at

which needle fails to make an impression on the surface of the test block shall be final sett

Figure

OBSERVATIONS AND CALCULATIONS:

A) Standard Consistency

Weight of cement taken for one mould = 400 gm

Type of cement =

SN Weight of

Water, gm

% of water

added

Initial reading

mm

Final reading

mm

Penetration from bottom

mm

(Initial reading is the indicator reading when the lower end of the plunger touches the bottom

non-porous surface of the mould.)

% of water for Standard Consistency =

B) Initial and Final Setting Time

Weight of cement taken for one mould = 400 gm

Type of cement =

Quantity of water added to cement = 0.85* quantity of water required for

standard consistency

=

SN Time

min

Initial reading

mm

Final reading

mm

Penetration from

bottom, mm

The initial setting time of the given sample of cement = ......... min.

The final setting time of the given sample of cement = ......... min.

CONCLUSION:

Go through the above-mentioned drive link for clarity.