Assessing brick production
Practical Action
You can tell a lot about bricks by soaking them in cold water for 48 hours. If you weigh bricks
before and after soaking, you can calculate the percentage of water they absorb. A good brick
shouldn't absorb more than 15% of its dry mass. If bricks are too absorbent they suck
moisture out of mortar and weaken the bond. You may find the brick dissolves altogether. In
this case, it's definitely underfired - and dangerous to use in any building. The presence of
lime may also be detected by soaking bricks. If lime is present as lumps, it may expand and
cause fractures, exposing powdery white deposits.
BRICK PROBLEM
1. SIZE
(a) Too big in all dimensions
(all types)
PROBABLE REASON
(i) Too many coarse particles
in raw material
POSSIBLE SOLUTION
(i) Sieve out coarse material or
crush soil before moulding
(ii)Underfired
(Either way,(i) or (ii), bricks
are not shrinking as allowed
for)
(iii) Mould or extrusion die is
too big - worn?
(ii) Increase firing temperature
&/or time (increase fuel?)
(iii) Replace
(b) Too thin (sand moulded & Squashed in handling -
slop moulded)
probably when laid to dry on
edge
More care handling bricks &
try moulding a little drier
(c) Too thick (extruded bricks) Cutting wires set wrongly
Adjust settings
(d) Too small in all dimension
(all types)
(i) Die or mould too small
(ii) Too high clay content -
excessive drying shrinkage
(i) Change
(ii) Add sand
(iii) Overburned - excessive
firing shrinkage - may affect
bricks only in hot-spots in kiln
(iii) Use less fuel. Try to avoid
hot-spots by distributing fuel
differently
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