Concrete Block Masonry

siennatearfulUrbain et civil

25 nov. 2013 (il y a 3 années et 11 mois)

67 vue(s)


GUYANA STANDARD

Section 8
-

Concrete and Block


Masonry


Scope


Reinforced Concrete Practice


Concrete Quality


Production of Concrete


Protection for Reinforcement






SCOPE




This code specifies the requirements for concrete and
block masonry used in structures or buildings.


Reinforced Concrete Practice



deals with materials such as Cement, stone,
aggregates, water and metal reinforcement



Cement, aggregates and metal reinforcement shall
confirm to the Specifications given by the ASTM or the
British Standard Institution.


The maximum size of coarse aggregates shall not be
larger than:


-

1/5 the narrowest dimensions between the
sides of forms

Reinforced Concrete Practice cont’d


-

1/3 the depth of slabs


-

¾ the maximum clear spacing between
individual reinforcing bars or bundles of bars




Water shall be clean and free from oils, acids, salts,
alkalis, organic materials or other detrimental
substances to concrete or reinforcement.


Concrete Quality



Based on the design requirements of a particular
structure, the engineer or architect would specify the
quality required.


Concrete Grade

Characteristic
Strength (N/mm
2
)


Category


10


15



20


25


10


15



20


25


-


Reinforced concrete with
lightweight aggregate


Reinforced concrete
with dense

aggregate


Production of Concrete


1. Handling, batching and mixing shall conform to
ASTM C 94



The processes for conveying, depositing and curing is
also outlined in the standard


. Formwork and Embedded Pipes

In the
design

of formwork, the following factors should be considered:


-

rate and
method

of placing concrete


-

construction loads


-

special form requirements for construction of shells, domes, architectural concrete or similar types
of elements.




Conduits and Pipes Embedded in Concrete


Conduits, pipes and sleeves of any material not harmful to concrete may be embedded in concrete with
the approval of the Engineer.



Conduits and pipes of
aluminium

shall not be embedded in concrete unless effectively coated or
covered to prevent
aluminium
-
concrete reaction or electrolytic action between
aluminium

and steel.








Protection for Reinforcement

The following minimum concrete cover shall be
provided for reinforcement:


Minimum Cover, mm

(i)
Concrete cast against and


permanently exposed to earth 70


(ii)
Concrete exposed to earth or weather


-

No. 20 to No. 55 bars 50


-

No. 15, 40



Protection for Reinforcement
-

cont’d



Minimum Cover, mm



(iii) Concrete not exposed to weather


or in contact with ground


(a) slabs, walls, joists


-

No. 45 and No. 55 40


-

No. 35 bar or smaller 20


(b) Beams, columns


-

primary reinforcement,


ties, stirrups 40



Block Masonry


Sizes


The nominal sizes for Concrete blocks are:


400 mm long x 200 mm high with a tolerance of + or


3 mm in
both dimensions


Standard thickness shall be 100mm, or 150 mm


Blocks shall be of two hole pattern, and shall have a net cross
sectional area not less than 50% nor greater than 60% of the
gross cross sectional area. The thickness of the face, shell and
web shall be 35 mm



Certification


Applications for permission to construct block masonry
structures shall be accompanied by a certificate from an engineer
or architect.


Block Masonry


Testing



When tested in accordance with ASTM C 140, the
Grade A blocks the maximum absorption of water
shall not exceed 208 kg/cu m of normal weight.



Test for compression strength of blocks shall be made
at 28 days, and a test shall be carried out for each 5000
blocks, each test consisting of 5 blocks.




Block Masonry


Mortar for Blockwork


The mix proportion for mortar shall be 1 part cement:
3 parts sand to achieve a strength at 28 days of 10
N/mm
2