Bricks are undoubtebly amongst the most commonly used construction materials anywhere. Incidentally, concrete is regarded as the most used construction material in the world in terms of weight or volume according to some estimates.
Knowing a few simple yet important quality related details as well as about few quality tests on this widely used construction material (ie brick) can be beneficial not only to civil engineers or construction personnel but also to any individual planning to build a house that would consume bricks galore. The quality related tests, to be discussed herein, are based on Indian standards. That may exude a bit of technical flavour but, in actuality, these are quite simple tests.
Years back, this author had inspected these quality tests at quality control laboratories in project sites a number of times and can tell from his experience that these are quite simple to understand or carry out and anyone, with or without technical knowledge in this domain, can conduct or get them done with ease in order to have a good idea about the quality of bricks to be used.
Bricks of different varieties are available in the market such as clay bricks, cement bricks, fly ash bricks and so on. However, the most commonly used and readily available type is the clay brick. The details and quality tests to be discussed in this submit are on clay bricks.
Two quite common and sticky issues concerning clay bricks are dampness & efflorescence. Once these problems begin showing up in an already completed structure or in any brickwork it is quite difficult to shake them off and they could prove to be quite a headache in the years to come. The easy way out is to go for quality bricks that are capable of withstanding these problems which can be seen in many buildings in many places. Discussed below are few general details that should come in handy for anyone and four commonly conducted quality tests on clay bricks.
First, the details:
Bricks to be used for any quality construction work such as residential, office, commercial or industrial buildings, etc should have smooth and good appearance. They should be of uniform sizes and shapes and should appear reddish in colour.
They should be well burnt. That is, they should neither be over-burnt nor under-burnt. Over-cooked and under-cooked ones won’t appear uniformly reddish. They would show shades of blue and sometimes even black or so. Usually, they won’t be of uniform shape as well.
When dropped from a height of about one meter on a dry firm ground (not on a concrete, plastered, etc surface) the brick should not show any damage.
When two randomly picked up bricks are struck mildly with each other they should produce a ringing sound.
When touching the surface of a brick the same should feel smooth (not silky though) and hard. Bricks with too rough, soft or dusty texture are usually of medium or low quality. This particular point is based on the very own observation of the author – so, one may accept it or ignore it.
For best results, bricks should be kept immersed in water for one to two hours prior to their use.
While it is quite common to have joint (mortar) thickness of 6 to 10 mm, care should be taken to ensure that maximum thickness of the joints don’t exceed half an inch.
Now, about the quality tests : Four simple tests usually performed on common clay bricks in quality control laboratories at construction sites are a) water absorption test b) efflorescence test c) test of compressive strength d) test of dimensions.
a) Water absorption test : Five bricks are picked at random from a stack of bricks intended to be used. They are then dried thoroughly in a laboratory oven at a temperature between 105¤C to 110¤C. Thereafter they are cooled and weighed separately. Then they are kept immersed in cold water (27¤C or – 2¤C). After 24 hours the bricks are taken out of water and excess surface water is wiped off using a damp fabric. Immediately after, they are weighed again separately. Supposing that the dry weight of a brick is Wd and the wet weight of the same brick is Ww, the water absorption capacity of the brick expressed in percentage of it’s dry wt. is = (Ww – Wd)/Wd X 100.
Upon calculating the same for each of the 5 bricks the average is found out which is considered as the water absorption capacity for the bricks. The water absorption capacity of first class bricks should not exceed 20% when calculated as described above. The same for 2nd and 3rd class bricks are not to exceed 22% and 25% respectively. For any superior quality brickwork, first class bricks only are recommended while 2nd & 3rd class clay bricks are advised for moderate to low quality work.
Contd. in Part-B …..