6. BRICK AND CONCRETE BLOCK WORK
6.1 Scope of work
Furnish all labour, material and equipment for the complete building of brick and concrete block work as shown on the drawings, as specified herein and as evidently necessary to complete the work.
Before starting the work the contractor shall submit the following to the Engineer and receive his written approval.
6.2.1 Manufacturer and sample blocks
Before precasting concrete block, the name and official address of the concrete block manufacturer, if the contractor intends to use a sub, contractor, sample block and sources of cement and aggregate making up the concrete block shall be submitted to the Engineer for his written approval.
6.3.1 Masonry brick
Brick shall be locally available products conforming to D.S. 3921 or equivalent and be hard, well baked and shall have a uniform and sufficient compressive strength appropriate to the use. The shape of the bricks shall be rectangular. Brick used in foundation shall be misakhraj brick or equivalent.
6.3.2 Concrete blocks
All concrete blocks shall conform to ASTM C129, B.S 2028 or equivalent unless otherwise specified as follows:
a. Concrete block shall be manufactured in accordance with the specification stated herein,
b. block shall be manufactured of Portland cement and locally available aggregate by mixing and compacting using an electric machine,
c. block shall be reasonably uniform in compressive strength and in all dimensions and shall be straight and free from cracks, chips or other defects.
Specification of the materials shall be in accordance with section ( 4_2), " Concrete work "
6.3.3 Joint mortar materials
cement shall be specified in section 4_2_1 ( concrete work)
Sand shall be clean sharp, coarse, well _ graded and shall conform to ASTM C-144 ( Aggregate for Mrrary jortar ) or B»S. 1200 ( Building sand from Natural aourcec)
water proofing additive shall conform to B.S 3826 or equivalent, other admixtures, such as a type which reduces early water loss from the masonry units and produces an expansion action in the plastic grout sufficient to off_set initial shrinkage and promote bonding of the grout , may be used when approved by the Engineer.
6. 4 Workmanship
6.4.1 The contractor shall provide a masonry foreman who is thoroughly experience, competent and skilled in masonry construction .
The foremen shall personally supervise the mixing and placing of all mortar. Masonry reinforcing and anchoring must be done in strict accordance with the drawing and specifications.
6.4.3 Mixing of joint Mortar
a. Standard proportion of mortar mix for the joint of bricks and blocks shall be: cement to sand = 1:3, or as directed by the Engineer, sulphate resisting cement shall be used in mortars below damp proof course
i. Mix mortar by mechanical mixer or by hand on a clean level board.
ii. mix thoroughly so that all individual constituents are incorporated evenly but do not over-mix mortars containing plasticizers.
iii. Keep mixer clean at all times.
iv. Use mortar with in one hours of discharge from mixer at normal taaporturo . In no case chalj nortor be used after the initial set has taken place. Reconstitution of mortar will not permitted.
6.4.4 Laying units
All work shall be laid true to dimensions and be plumb, square in bond and properly anchored with vertical and horizontal straight joints that are in line, plumb, horizantal and true . Brick laying for protective chin for waterproofing memberane shall be laid in running bond with standard 2_3mm joints horizontally and vertically. All surfaces of waterproof memberane to receive briek laying shall be throughly domed masnory mortar shall be spead over the cntir surface of joints. laying out of the bricks shall be arranged so that vertical joint are staggered Salf bricks or other shapes shall be used where required, All hollow block shall be laid cells vertical and with full nortar coverage on all top and side faces, horizontally and vertically. Cells of hollow blocks to be grouted with concrete or nortar are those carrying the horizontal and vertical reinforcement and also abutting cells, with or without reinforcing, cells of hollow block forming the cider, of entrances and doorways and cantilevered fins of walls and those so indicated on the drawings or so required by the Engineer.
In Icying concrete solid blocks, pounding of comers and jambs after units liave been set in position shall be avoided, where an adjustment must be made after the mortar lias startde to cat, the mortar shall be removed and replaced with fresh mortar, colls of unfinished ends shall not exposed, Bond all interesting masonry walls together as indicated or a approved by the Engineer, When necessary to out masonry units, preference must be given to the use of power oquipreiit . Cutting shall be kept to a minimum.
A protective covering of mortar shall be fornecl around the reinforcing bars at a minimum depth of 20 mm, laying for brick work shall be as shown on the drawings. when it in not specified on the drawings, the contractor shall follow the instruction of the Engineer.
Joints of masonry units which will be exposed or painted. form a concave joint section.
Joints which are not to bo visible in the finished work to be dtruck off with the trowel as the work proceeds.
joints on the oufaces of fair_faced work shall be finished to provide as mooth surface flush with the brick and or block
face or a keyed joint of approved profile aa the work proceeded
All hole in corposed rjasomy shall be repaired, and the walls pointed. Defective joints shall be trowelled out and repointcd with nortar.