HOW TO PERFORM COMPRESSIVE STRENGTH TEST OF CEMENT(IS:4031-PART 6-1988) ?

Compressive strength of cement is determined by performing the compressive strength test on mortar cubes compacted by vibration machine. For the preparation of cement mortar, Standard sand (IS:650) is used. The specimen is prepared in the form of cubes 70.6 mm x 70.6 mm x 70.6 mm.

OBJECTIVE

To determine the compressive strength of mortar cubes (standard).

APPARATUS

• Cubic Mould : The capacity of cubic mould is 70.6 x 70.6 x 70.6 mm3 (IS : 10080).

• Vibration Machine : The vibration machine should be works as per the IS : 10080.

• Balance : The balance measuring weigh 1000 g with an accuracy of 1 g.

• Measuring Cylinder : The capacity of measuring cylinder s 200 ml with an accuracy of 1 mm.

• Enamel tray, Trowel, Poking rod other apparatus required.

PROCEDURE

• The test specimens are 70.6 mm cubes having face area of about 5000 sq. mm. Large size specimen cubes cannot be made since cement shrinks and cracks may develop. 

• The temperature of water and test room should be 27°± 2°C. 

• A mixture of cement and standard sand in the proportion 1:3 by weight is mixed dry with a trowel for one minute and then with water until the mixture is of uniform colour. 

• Three specimen cubes are prepared. The material for each cube is mixed separately. 

• The quantities of cement, standard sand and water are 185 g, 555 g and (P/4) + 3.5, respectively where P = percentage of water required to produce a paste of standard consistency. 

• The mould is filled completely with the cement paste and is placed on the vibration table. Vibrations are imparted for about 2 minutes at a speed of 12000±400 per minute.

• The cubes are then removed from the moulds and submerged in clean fresh water and are taken out just prior to testing in a compression testing machine.

• Compressive strength is taken to be the average of the results of the three cubes. 

• The load is applied starting from zero at a rate of 35 N/sq mm/minute. The compressive strength is calculated from the crushing load divided by the average area over which the load is applied.The result is expressed in N/mm2.

CALCULATION

P = Maximum load applied to the cube.

A=Cross sectional area (Calculated from the mean dimensions).

Compressive strength is reported to the nearest 0.5 N/mm². when wrong specimen have prepared, or that give strengths differing by more than 10% from the average value of all the test specimen should not be considered.

STANDARD SPECIFICATION

CEMENT TYPE	COMPRESSIVE STRENGTH (Mpa)
	1 Day	3 Days	7 Days	28 Days
OPC(33)	not specified	16	22	33
OPC(43)	not specified	23	33	43
OPC(53)	not specified	27	27	53
SRC	not specified	10	16	33
PPC	not specified	16	22	33
RHPC	16	27	—	—
PSC	not specified	16	22	33
High alumina	30	35	—	—
Super sulphated	not specified	15	22	30
Low heat	not specified	10	16	35

HOW TO CHECK SOUNDNESS OF CEMENT BY LEE-CHATELIERS MATHOD (IS:4031-(PART 3)-1988) ?

In the soundness test a specimen of hardened cement paste is boiled for a fixed time so that any tendency to expand is speeded up and can be detected. Soundness means the ability to resist volume expansion.

OBJECTIVE

To determine the soundness of hardened cement paste by le-Chateliers method.

APPARATUS

• Le-Chateliers Apparatus : The size of apparatus should be made as per IS: 5514.

• Water Bath : The water bath should have a minimum temperature 100 with an accuracy of 1. 

• Caliper : The measuring length of caliper is 30 cm with 0.5 mm accuracy.

• Measuring Cylinder : The volume of measuring cylinder is 100 ml with an accuracy of 1 ml.

• Balance : The should weigh 100 g accurately with an accuracy of 1 g.

• Glass sheets (2 nos), Enamel tray, trowel are the other apparatus required for test.

PROCEDURE

• The mould is placed on a glass sheet and is filled with neat cement paste formed by gauging 100 g cement with 0.78 times the water required to give a paste of standard consistency. 

• The mould is covered with a glass sheet and a small weight is placed on the covering glass sheet. 

• The mould is then submerged in the water at temperature of 27°-32°C. 

• After 24 hours, the mould is taken out and the distance separating the indicator points is measured to the nearest 0.5 mm (L1). 

• The mould is again submerged in water. The water is now boiled for 3 hours. 

• The mould is removed from water and is cooled down. 

• The distance between the indicator points is measured again to the nearest of 0.5 mm (L2). 

• The difference between the two measurements represents the unsoundness of cement.

CALCULATION

The difference between the two  measurements to the nearest of 0.5 mm represents the unsoundness of cement.

Soundness Of Cement = L₁-L₂

PRECAUTIONS

• All the measurements should be done accurately.

• Extra pressure should not apply while filling the moulds.

• During boiling water level should not fall below the height of the mould.

STANDARD SPECIFICATIONS

Type/Name of cement	Reference Indian standard	Expansion (max.)
OPC (33)	IS:269-1989	10 mm
OPC (43)	IS:8112-1989	10 mm
OPC (53)	IS:12269-1987	10 mm
Rapid hardening	IS:8041-1990	10 mm
Low heat cement	IS:12600-1989	10 mm
Super sulphated	IS:6909-1990	5 mm
Portland pozzolana	IS:1489-1991(part 1)	10 mm
PSC	IS:455-1976	10 mm
High alumina cement	IS:6452-1989	5 mm
SRC	IS:12330-1988	10 mm
Masonry cement	IS:3466-1988	10 mm
IRS-T-40	Railway standards	5 mm