Testing of Concrete masonry Blocks
Concrete masonry bricks are very useful in the rural areas as it is cheap, easily found and can form less strong buildings, the compressive strength of the bricks should be tested.
And in urban areas these kinds of buildings may present a combination of both office and houses or grocery stores and houses or offices and retail stores.
Concrete can be changed into formed masonry units like Hollow and Solid normal and light weight concrete blocks in right size to use for load and non-load bearing units for fencings or wallings. These concrete blocks are used more in the regions where soil bricks are costly, have less strength and not available all the time. As per the structural needs of masonry unit, the concrete mixes can be arranged using available ingredients or if not be suitable then with in the most economical distance.
Hollow concrete blocks are used for normal masonry when reinforced is used and it should not be leaner than 1 part cement of 8 parts room dry sand by volume. Compressive strength of concrete blocks or concrete masonry units is important to know the fitness of these in construction works for different reasons. Concrete masonry blocks are normally made of cement, amount and water which are usually comes in rectangular shape used in construction of masonry structure.
20 full sized units shall be counted for length, wide and height and the center units shall be calculated for least thickness of face, shells and webs.
The minimal dimensions of concrete masonry block differ in three things such as:
- Length: 400/500/600mm
- Width: 200/100mm
- Height: 50, 75, 100, 150, 200 or 300mm.
Tests on Concrete Masonry Block Units
various tests are done on concrete masonry unit to check all the requirements, but among them three most applied tests are discussed in this article. The blocks of same mix shall be taken and classified to these following tests:
- Dimension measurement for all types of blocks
- Density of the concrete masonry blocks (3 blocks)
- Compressive Strength tests
In this step all the blocks should be verified and calculated by the length, width and height with steel scale. After checking if the block found hollow, then the thickness of the web and face shell are calculated with caliper ruler, next a report need to be prepared included average length, width and height of block and with least face shell and web thickness using recorded dimensions.
At first the block has to be heated in the oven to 100°c, then the heated block need to be cooled in the room temperature. Next measure the dimensions of block to find out the volume and weight of it, the density of the block is calculated form a calculation and the standard density of 3 blocks will be the final block density. The formula is: mass/volume (kg/m3 )
the average compressive strength of concrete masonry block is calculated by taking 8 blocks and all of them should be tested with in 3days after gathered in lab where the age of the blocks should be 28 days. The compressive strength is calculated in the Compressive
Strength Testing machine which has tow steel bearing blocks, one is in fixed position on which the masonry unit is kept and the other movable one can transfer the load to the masonry unit while applying. When the masonry unit’s bearing area is more than the steel blocks’ bearing area some different steel plates will be used. Those plates are organized on steel blocks in a way that the centre of masonry unit agreed with the center of thrust of blocks, bearing area units are completed with the Sulphur and granular materials coating. Then the unit in testing machine is placed and one-half of the expected highest loads are followed at a minimum rate while the rest is applied in not less than 2 minutes. Te load of masonry unit fails and the highest load is divided by basic sectional area of unit will give the compressive strength of block. By applying the same method, find out the rest 7 blocks’ compressive strength and then calculate the average strength of the 8 blocks which will be the final compressive strength of concrete masonry unit.