Compressive strength of Mortar Cubes

Objective: To calculate the compact strength of the standard cement sand mortar cubes


7.06cm cubes moulds (50cm2 face area)

Apparatus for measuring and blending the vibrator, mortar and compression testing devices.


Lets take 600gm of standard sand and 200gm of cement in the ratio of 1:3 by weight) in a pan. (The regular sand should be of light, quartz, grayish or whitish assortment and must be exclusive of silt. The sand grains must be angular; the form of grains similar to to the sphere-shaped form, lengthened and compressed grains being present there only in very little quantities.

Standard sand will slide through 2mm IS sieve and should be preserved on 90 microns IS sieve with the following element volume distribution:

Blend the sand in cement in dry atmosphere with a trowel for 60 seconds and water should be added next. The measure of water has to be (p/4+3)% of mutual mass of sand and cement where, p refers to the % of water needed to create a paste of average constancy anticipated beforehand. Then add water and blend it till the whole paste is of consistent color. The time period of blending should not be greater than 3 minutes and not lesser than 4 minutes. Straight away after blending the mortar, put the mortar in the cube mould and nudge it with aid of a steel rod. The mortar should be nudged or prodded for at least 20 times in approximately 8 seconds to make sure of exclusion of entrained air. If vibrator device is utilized, the time period of vibration will be approximately 2 minutes at the specific speed of 12000+-400 vibrations /minutes. Then put the cube moulds in maximum temperature of 27±2C and 90% comparative moisture for a whole day. After completion of 24 hours, detach the cubes from the mould and straight away merge them partially in clear water until testing. Remove the cubes from water just prior to testing. Testing should be carried out on their sides exclusive of any kind of packing. The speed of loading must be 350 kg/cm2/minute and consistent. Test should be carried out for at least 3 cubes and report the standard value as the test outcome for both 7days and 28 days compact strength.


Compressive Strength at 7 days= ……….N/mm2

Compressive Strength at 28 days= ……….N/mm2


Range Calculations

Permit-able compressive stress=

Diameter of cross section of cubes=50cm2

Expected load=stress x area x f.s=

Range to be selected is ………..

Compressive Strength

Breaking load= ……………….

Diameter of cross section=………………….

Compressive strength=……………………