Real NABTEB Bricklaying Questions And Answers.
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NABTEB Bricklaying Questions And Answers 2021
With the aid of neat sketches, show the following tools/equipment:
(i) Brick/Block laying trowel
(ii) Spirit level
(iii) Laying on trowel
A. Explain the basic differences between coarse and fine aggregates.
Coarse aggregates consist primarily of materials large enough to a proportion that cannot pass through
a standard sieve of 4.76mm radius. The maximum size of coarse aggregate is however determined by
the class of work to be carried out.
Fine aggregate is made up of materials small enough to pass through a seize of 4.76mm radius
B. Give two (2) examples of each coarse and fine aggregates
Examples of coarse aggregates include:
(i) Natural gravel
(ii) Crush stone
(iv) Sand stones
While, fine aggregates include:
(i) Natural sand
(ii) Crushed gravel
(iii) Crushed stone
A. With the aid of a line diagram, show the process of manufacture of clay bricks.
B. Explain in detail the difference between continuous and intermittent kilns
In this type of kiln, dried clay bricks otherwise known as green bricks are loaded into steel trucks to form a continuous line that passes into a long chamber that has a firing zone of high temperatures at the centre of it’s length. The trucks are then passed gradually through the kiln. The bricks get warmed as they reach the firing zone. The bricks then get cautiously burnt at controllable temperatures and are allowed to gradually cool before emerging at the exit end of the kiln for unloading and subsequent delivery to site. One notable example of the continuous kiln is the Hoffman type.
In intermittent kilns, bricks are molded, dried and stacked either in enclosures like in the scotch kiln or down-draught kiln. Sometimes the bricks are loaded in exposed sites out the sides and tops of stacks , green bricks are covered with under-burnt bricks to protect the bricks from weather effects
likely to affect it before firing. In both cases of intermittent kilns however, fire-holes are provided
at bases of the stocks or sides as the case maybe. During burning, the fire-holes are filled with
burning material such as coal or coke breeze. The fire material is then ignited and heat gradually rises as the fireworks increases thereby burning the bricks to the required temperature which bakes and hardened the bricks to useful building material.
A. State four (4) precautions to be taken when laying screed to an old concrete floor.
Precautions to be taken before laying screed to an old concrete floor.
(i) Clean off the surface of the concrete floor thoroughly
(ii) Remove only laitance or scum on top of the concrete floor.
(iii) Hack the surface of the concrete to ensure good bondage either manually or mechanically
with a hack hammer.
(iv) Wet the surface with water to ensure hardening and shrinkage of screed and slab
simultaneously. This also prevents detachment of screed from the concrete base .
B. Explain briefly, the following methods of construction used for lay screed finishes.
(i) Monolithic method.
(i) Monolithic method:- This involves laying the screed within three hours of cast-in-situ
concrete slab. The mix is prepared in the proportion of 1:1:2 by weight of cement fine
aggregate or sand and coarse aggregate. The amount of water is just enough to obtain a workability that enhances full compaction. The screed thickness ranges from 12mm to
40mm depending on the slab and purpose of which the floor is prepared.
(ii) Separate method:- This is the application of the screed to a concrete slab that is cast, set
and hardened before the screed is laid on top to finish the floor. In this case, the proportion
of mix is similar to the monolithic type of screeding but the procedure for casting is done in
bays of not exceeding 15m2 .Again, in separate method of screeding, caution has to be taken
as the slab is to be thoroughly cleaned, laitance and scum removed, the slab also has to be
hacked and finally wet with water before screed is laid.
Show with sketches the elevation of the following types of bond up to five course:
State six (6) safety regulations to be observed in the erection of tubular scaffolding.
(i) The scaffolds should be erected under the supervision of a competent personnel.
(ii) They should conform with the construction requirements as contained in the Health and
Safety work Act.
(iii) The scaffold should be strong enough to avoid accidents usually caused by their fall or
(iv) The scaffold should be rigid and fit to carry both work men and materials while in use.
(v) The standards or vertical supports upon which the load is transmitted should rest on a solid
(vi) Platforms should be closely and firmly boarded together and should be wide enough to
carry both men and materials.
(vii) The board should be provided on all platforms higher than 2m and 200mm above the top of
(viii) Guard rails should be provided on all platforms and fixed on the sides of the standards.
Heights of guard rails from top of platform should not be more than 900mm.
(ix) Ladders used for access to various platforms of the scaffold should be firmly secured at the
top and rest on a solid base or wall.
A. State four (4) advantages of pitch fibre pipes.
Advantages of pitch fibre pipes include:
(i) They are used for both domestic and trade wastes.
(ii) They are produced in portable nominal length ranges from 1.7m to 3.0m.
(iii) They also have nominal standard bores which range from 50mm to 225mm.
(iv) They are flexible in their tapered end connection
(v) They are more economical to use in bad ground conditions than clay pipes.
(vi) They can also be coupled with snap ring rubber seals to enhance longitudinal flexibility (the
expansion and contraction).
B. State four (4) advantages of flexible joints over rigid joints in drain construction.
Advantages of flexible joints over rigid joints include:
(i) Flexible joints produce the economy of expansion but rigid joints are prone to damage
under bad ground conditions.
(ii) Rigid joints are usually applied to pipes of smaller bores made mainly of clay or concrete
materials while flexible joints could be applied to both small and bigger sizes of pipes
providing additional protection to the joints.
(iii) Flexible joints when jointly used with the pipes have ability to absorb movement and
distribute the pressure uniformly over the surface area of its coverage.
(iv) Flexible joints are made of more durable materials and can withstand both thermal and
other forces exerted on them.
A. Apart from ordinary Portland cement, describe two other cements both in use and manufactured.
(i) Rapid Hardening Portland Cement: This is made by mixing together chalk or limestone, with
clay or shale, heating them to a clinker and grinding them to finer powder than that for
ordinary Portland cement. The setting time is similar to that of O.P.C. But it develops
strength more rapidly. It enables form work to be struck earlier.
(ii) Extra-Rapid Hardening P.C: Manufactured by adding an accelerator e.g calcium chloride
(cacl2) to rapid hardening Portland cement. It has quick initial set. Hardening much faster
than rapid hardening p.c. It is particularly useful in cold weather. Allows concreting to
continue during low (not freezing) temperature. It is also useful for marine work in intertidal conditions.
(iii) High Alumund Cement: Made from chalk and bauxite, black in color. Develops high strength
in 24 hours, making it responsibly useful for emergency work and in cold weather. It resists
sulphate attack and some weak acids and most organic liquids.
(iv) Hydrophobic Cement: Made by adding substances to Portland cement and during the
grinding process, which form a water repellant film around each grain of cement. The
cement can thus be stored under humid and damp conditions without deterioration. During
the mixing process, the film is rubbed off and normal hydration takes place.
(v) White Cements:- By special manufacturing process and selection of raw materials, the
amount of iron in the Portland cement is considerably reduced. It is used for manufacturing
precast concrete products and in a production of cement points.
B. What is the effect of gypsum in cement and what percentage is used.
Gypsum in cement helps to retard the setting time of cement, thus allowing the work for which the
cement is required to be done before setting and hardening take place. The percentage of Gypsum used
a. With neat sketches describe dependent and independent scaffolding.
b. Give four (4) reasons why the use of tabular scaffolding in preferred.
Tabular scaffolding is preferred because
(i) It is lighter in weight.
(ii) It is easier to erect and dismantle.
(iii) It is more durable.
(iv) It is stronger.
(v) It is safer.
a. Define the following sewage/drainage terms:-
(iii) Half channel
(i) A manhole is an inspection chamber exceeding 900mm in depth. There are iron steps or
ladder built in the manhole wall at 300mm height to provide access into the manhole where
the depth is.
(ii) Benching is a weathering construction made at the sides of the invert of a manhole or
inspection chamber to control the flow of sewage and to allow a man to stand.
(iii) Half Channel is a pipe cut along its length either in half and used at the internal bottom of
the inspection chamber or manhole. It may also be formed with concrete.
b. Sketch a pipe showing spigot and socket ends.
c. Give two (2) advantages of separate system of drainage.
(i) Reduction in the cost of pumping/evacuation
(ii) Reduction in the cost of sewage treatment
A. Describe in sequence the method of rendering an old neglected wall.
The sequence is as follows:
(i) The brick joints should be raked out to form a key for the under coat
(ii) The surface of the wall should be made free of dirt and other things that will impair
(iii) Wet the surface with water
(iv) Apply rich mix mortar under coat
(v) Scratch the under coat to form key for the final coat.
B. Specify the correct mortar in external wall and internal wall surface furnishing.
For the external wall surface:
1 part of Portland cement
½ part lime; 44 ½ parts of sand by volume.
1:1:5 to 6 parts cement, lime and sand OR
1 part cement to 6 parts sand.
For Internal wall Finish:
1:0: ¼ of cement lime and sand.
C. List two advantages of rendering.
Advantages of Rendering:
(i) It prevents water penetration.
(ii) It improves appearance.
(iii) Weather proof.
Two floors are to be tiled. The size of each floor is 20m x 150mm. Allow 5% of cutting and wastage
(i) The number of tiles to be used for the whole floors and
(ii) The cost of tiles to be used if a crate of 80 tiles cost 1250.00naira.
With a scale of 1:10, draw a section through 1brick external wall showing the following in your drawing.
1. Foundation concrete
2. Footing coarse
4. Concrete slab
6. Floor screed
B. Mention two (2) methods of bridging an opening
(i) By the use of the wood lintel
(ii) By the use of concrete lintel
(iii) By the use of arches
(iv) By the use of solid bricks
C. State two (2) precautions to be observed when it becomes necessary that a word lintel be used.
(i) Ensure that the wood is hard
(ii) Make certain that the wood is free of defects
(iii) Ensure that the span of the opening is not too large.
(iv) Ensure that the lintel is not exposed to weather
(v) Make sure that the wood lintel is minimally loaded.
(vi) Use timber of large section.
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