The compressive strength of mortar, as determined by
utilizing 2-inch or 50mm cubes in accordance with ASTM C109 / C109M - Standard
Test Method for Compressive Strength of Hydraulic Cement Mortars, serves as a
crucial parameter in assessing the durability and load-bearing capacity of
various masonry structures. Mortar, composed of a blend of cement, sand, and
water, finds widespread application in masonry works such as bricklaying, stone
masonry, and plastering of walls and columns. This article aims to delve into
the significance of testing mortar compressive strength, the methods employed
for its determination, and the calculation procedures involved.
Procedure for Determination of
Compressive Strength
To ascertain the compressive strength of standard
cement-sand mortar cubes, a meticulous procedure is followed, employing
specific apparatus and protocols.
Apparatus
The apparatus required for conducting the compressive
strength test includes 7.06cm cube molds with a face area of 50cm², equipment
for gauging and mixing mortar, a vibrator, and a compression testing machine.
1.
Procedure for Compressive Strength of Mortar
2.
Measure 200g of cement and 600g of standard sand
in a 1:3 ratio by weight.
3.
The sand utilized must conform to specified
standards, exhibiting characteristics such as angular grains and passing
through a 2mm IS sieve.
4.
Mix the dry cement and sand thoroughly for one
minute, then gradually add water. The water quantity should be proportional to
the combined weight of cement and sand, determined by a predefined formula
based on the paste's standard consistency.
5.
Continue mixing until a uniform consistency is
achieved, ensuring a mixing duration between 3 to 4 minutes.
6.
Transfer the mortar mixture into cube molds,
compacting it by prodding the mixture 20 times within 8 seconds to eliminate
entrapped air.
7.
If a vibrator is utilized, subject the cube
molds to vibration for a duration of 2 minutes at a specified speed of
12000±400 vibrations per minute.
8.
Place the cube molds in an environment with a
temperature of 27±2°C and 90% relative humidity for 24 hours.
9.
After 24 hours, remove the cubes from the molds
and submerge them in clean water until testing. Testing should be conducted on
their sides without any additional packing.
10.
Employ a uniform rate of loading, typically 350
kg/cm²/minute, for testing three cubes and report the average values as the
compressive strength at both 7 and 28 days.
The results of the mortar cube test are reported in terms of
compressive strength at 7 and 28 days, expressed in N/mm². Additionally,
calculations involve determining the breaking load, cross-sectional area, and
ultimate compressive strength of the mortar samples.
In summary, the compressive strength of mortar serves as a
fundamental parameter in assessing the structural robustness of masonry
constructions. Through meticulous testing procedures and precise calculations,
engineers and construction professionals can ensure the durability and safety
of load-bearing structures, thereby contributing to the overall resilience of
buildings and infrastructure.
No comments:
Post a Comment