Nothing Special   »   [go: up one dir, main page]
Scribd Logo
Upload

Welcome to Scribd!

  • 235 views

    Precast Cement Concrete Block Construction - Seminar Report, PPT, PDF For Civil Engineering

    Uploaded by

    Soc Rua Nguyen
    This document discusses the manufacturing process of precast cement concrete blocks. It describes how concrete blocks are made using cement, aggregates, and water. The blocks are cast in molds and cured before use. The document provides specifications for the dimensions, proportions, densities and tolerances of concrete blocks. It also describes how to lay the blocks in mortar to construct walls.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    Precast Cement Concrete Block Construction - Seminar Report, PPT, PDF For Civil Engineering

    Uploaded by

    Soc Rua Nguyen
    235 views12 pages
    This document discusses the manufacturing process of precast cement concrete blocks. It describes how concrete blocks are made using cement, aggregates, and water. The blocks are cast in molds and cured before use. The document provides specifications for the dimensions, proportions, densities and tolerances of concrete blocks. It also describes how to lay the blocks in mortar to construct walls.

    Original Description:

    Original Title

    Precast Cement Concrete Block Construction | Seminar Report, PPT, PDF for Civil Engineering

    Copyright

    © © All Rights Reserved

    Available Formats

    PDF, TXT or read online from Scribd

    Did you find this document useful?

    Is this content inappropriate?

    This document discusses the manufacturing process of precast cement concrete blocks. It describes how concrete blocks are made using cement, aggregates, and water. The blocks are cast in molds and cured before use. The document provides specifications for the dimensions, proportions, densities and tolerances of concrete blocks. It also describes how to lay the blocks in mortar to construct walls.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    235 views12 pages

    Precast Cement Concrete Block Construction - Seminar Report, PPT, PDF For Civil Engineering

    Uploaded by

    Soc Rua Nguyen
    This document discusses the manufacturing process of precast cement concrete blocks. It describes how concrete blocks are made using cement, aggregates, and water. The blocks are cast in molds and cured before use. The document provides specifications for the dimensions, proportions, densities and tolerances of concrete blocks. It also describes how to lay the blocks in mortar to construct walls.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 12

    Abstract

    Published on Sep 29, 2021

    This seminar report justify the manufacturing of cement concrete


    blocks, solid or hollow for various purposes as walling, non load
    bearing member of a structure parapet walls coping precast flooring
    etc. The block density of a concrete block will be calculated by
    dividing the overall volume including holes or cavities. PRECAST
    CEMENT CONCRETE BLOCK is factory made product. It is possible
    to prepare well-made pre-cast products by keeping a high standard
    of finishing.Pre-cast products vary from simple structures such as
    fencing posts, pipes,paving slabs,etc. to elaborate and complicated
    artificial concrete blocks..Due to problem of pollution control and
    shortage of land for brick manufacturing , the precast concrete block
    construction is becoming very advantageous for building
    construction day to day.

    MATERIALS

    1) Cement:- Literally, cement means a binding material. It has the


    property of setting and hardening when mixed with water to attain
    strength. The cement may be natural or artificial.Natural cement is
    manufactured by burning and then crushing natural cement stones,
    which contain argillaceous and calcareous matter.Artificial cement is
    manufactured by burning appropriately proportioned mixture of
    argillaceous and calcareous materials at a very high temperature and
    then grinding the resulting burnt mixture to a fine powder.

    2) Aggregates:-These are the inert or chemically inactive materials


    which form the bulk of cement concrete. These aggregates are
    bound together by means of cement. The aggregates are classified
    :
    into two categories: fine and coarse.

    1. Fine aggregates:-The material which is passed through 4.7625mm


    size B.S test sieve is termed as a fine aggregate. Usually natural river
    sand is used as a fine aggregate.

    2. Coarse aggregate:- The material which is retained on 4.7625mm


    size B.S test sieve is termed as a coarse aggregate. Broken stone is
    generally used as a aggregate.

    3) Water:- This is the least expensive but most important ingredient


    of concrete . Water , which is used for making concrete ,should be
    clean and free from harmful impurities such as oil ,alkali ,acid ,etc. In
    general,water which is fit for drinking should be used for making
    concrete.

    4) Cement concrete:- Cement concrete is a mixture of cement, sand,


    pebbles or crushed rock and water, which, when placed in the
    skeleton of forms and allowed to cure, becomes hard like a stone .
    Cement concrete has attained the status of a major building material
    in all branches of modern construction because of the following
    reasons:

    1. It can be readily moulded into durable structural items of various


    sizes and shapes at practically no considerable labour expenditure.

    2. It is possible to control the properties of cement concrete within


    wide range by using appropriate ingredients and by applying special
    processing techniques-mechanical, chemical and physical.

    3. It is possible to mechanise completely its preparation and placing


    processes.

    4. It possesses adequate plasticity for mechanical working.


    :
    MANUFACTURING

    Mould:-

    Moulds shall be fabricated using mild steel plates and mild steel
    angles for stiffening the plates.

    The mould should be either fixed type or (box with four side walls
    fixed at corners, and top and bottom open) or split type.

    Split type may be either individual or gang mould. Where the


    compaction of the concrete is done manually, the mould may be
    either fixed type or split type. When the composition of the
    compaction of the blocks is done with surface vibrator, the mould
    shall be only split type (individual or gang mould).

    Demoulding shall be done 5 to 10 minutes after compaction. In case


    of fixed type mould it shall be pulled up with one side handles while
    pressing down the blocks with the place at top with thumb. In case
    of split mould, the sides shall be removed first and the partition
    plates (gang mould) shall be pulled up subsequently.

    After demoulding, the blocks shall be protected until they are


    sufficiently hardened to permit handling without dam

    Proportion:-

    The normal proportion of the mix shall be as specified. To attain


    maximum strength, the water-cement ratio and workability of the mix
    should or controlled and proper compaction of concrete in the mould
    ensure age.
    :
    Fig.1 Concrete Block Mould

    Casting:-

    After mixing, the concrete shall be placed in the moulds immediately,


    being carried in metal gamelas other suitable vessels or by a chute.
    The concrete should be mixed in a concrete mixer and the water-
    cement ratio should be the smallest should be preferably by the use
    of a small immersion vibrator or table vibrator.

    Curing:-

    The blocks hardened shall then be cured in a curing water tank or in


    a curing yard and shall be kept continuously moist for at least 14
    days.

    Drying:-

    After curing, the blocks shall be dried for a period of two to four
    weeks depending upon weather before being used on the work. The
    :
    blocks shall be allowed to complete their initial shrinkage before they
    are laid in a wall.

    Dimensions:-

    Concrete masonry building units shall be made in sizes and shapes


    to fit different construction needs. They include stretcher, corner,
    double corner or pier, jamb, header, jamb, bull nose, and partition
    block, and concrete floor units.
    Concrete block hollow (open or closed) or solid shall be referred to
    by its nominal dimensions.

    The nominal dimensions of concrete block shall be, as follows:

    Length : 400,500 or 600 mm

    Height : 200 or 100mm

    Width : 50, 75, 100, 200, 250 or 300mm

    in addition, block shall be manufactured in half lengths of 200, 250


    or 300mm to correspond to the full lengths
    :
    Tolerances:-

    The maximum variation in the length of the units shall not be more
    than +5mm and maximum variation n height and width of unit, not
    more than +3mm.

    Density:-

    The hollow blocks shall be provided cavities in such a way so as to


    ensure the maximum block density of 1600 kg/m3. The block density
    is the density is the density calculated by dividing the mass of a
    block by the overall volume including holes or cavities.

    Construction Of Masonry

    For single storeyed buildings,the hollows of blocks in foundation and


    basement masonry shall be filled up with sand and only the top
    foundation course shall be of solid blocks. But for two or more
    storeyed buildings,solid concrete blocks shall be used in foundation
    :
    courses, plinth, and basement walls, unless otherwise indicated. If
    hollow blocks are used, their hollows shall be filled up with cement
    concrete 1:3:6 using 12.5 mm nominal size aggregates.

    Wetting of Blocks:-

    Blocks need not be wetted before or during laying in the walls. In


    case the climate conditions so require, the top and the sides of
    blocks may only be slightly moistened so as to prevent absorption of
    water from the mortar and ensure the development of the required
    bond with mortar.

    Laying:-

    Blocks shall be laid in mortar,as indicated and thoroughly bedded in


    mortar, spread over the entire top surface of the previous course of
    blocks to a uniform layer of not less than 10 mm and not more than
    12mm in thickness .

    All course shall be laid truly horizontal and vertical joints made truly
    vertical Blocks shall break joints with those above and below for not
    less than quarter of their length .Precast half length closer and not
    cut from full size blocks shall be used .For battered face ,bedding
    shall be at right angle to the face unless otherwise directed .

    Care shall be taken during construction to see that edge of block are
    not damaged.

    Provision for Door and Window Frames:-


    :
    A course of solid concrete block masonry shall be provided under
    door and window openings (or a 10 cm thick precast concrete sill
    block under windows). The solid shall extend for at least 20 cm
    beyond the opening one either side .For jambs very large doors and
    windows either solid units are used, or the hollows shall be filled in
    with concrete of mix 1:3:6 using 12.5 mm nominal size aggregates.

    Intersecting Walls:-
    :
    when two wall meet or intersect and the course are to be laid up at
    the same time , a true masonry bond between at least 50% of the
    units at the intersecting is necessary. when such intersecting walls
    are laid up separately, pockets with 20mm maximum vertical spacing
    shall be left in the first wall laid .The corresponding course of the
    second wall shall be built into these pockets.

    Provisions for roof:-

    The course immediately below the roof slab shall be built with solid
    blocks .The top of the roof course shall be finished smooth with a
    layer of cement and coarse sand mortar 1:3,10 mm thick and covered
    with a thick coat of white wash or crude oil , to insure free movement
    of slab.

    Piers:-

    The top course of block in the pier shall be built in solid blocks.
    Hollow concrete block shall not be used for isolated piers, unless
    their hollows are specified to be filled with a cement concrete.
    Fixtures,fitting ,etc. shall be built into the masonry in cement and
    carse sand mortar 1:3 while laying the blocks where possible .Hold
    fasts shall built into the joints of the masonry during laying .

    Holes, chases, sleeves , openings etc. of the required size and shape
    shall be fprmed in the masonry with special blocks while laying,for
    fixing pipes,service lines ,passage of water etc. After service lines
    ,pipes,etc. are fixed ,voids left ,if any , if any , shall be filled up with
    cement concrete 1:3:6 (1 cement :3 coarse sand :6 stone aggregate
    2 mm nominal size ) and neatly finished .

    Finishes:-

    Rendering shall not be done to the walls when walls are wet . Joints
    :
    for plastering or pointing as specified shall be raked to a depth of 12
    mm. joints on internal faces, unless otherwise indicated ,shall be
    raked for plastering . if the internal faces of masonry are not to be
    plastered the joints shall be finished flush as the work proceed or
    pointed flush where so indicated

    ADVANTAGES

    1. Concrete of superior quality is produced as it is possible to have


    better technical control on the production of concrete in factory.

    2. It is not necessary to provide joints in pre-cast construction.

    3. The labour required in the manufacturing process of pre-cast units


    can easily be trained.

    4. The moulds employed for preparing the pre-cast units are of steel
    with exact dimensions in all directions. These moulds are more
    durable and they can be used several times.

    5. The pre-cast articles may be given the desired shape and finish
    with accuracy.

    6. The pre-cast structures can be dismantled ,when required and


    they can be suitably used elsewhere.

    7. The transport and storage of various components of concrete for


    cast-in-situ work are eliminated when pre-cast members are
    adopted.

    8. The work can be completed in a short time, when pre-cast units


    are adopted. When pre-cast structures are to be installed , it is
    evident that the amount of scaffolding and formwork is considerably
    reduced.
    :
    9. When pre-cast structures are to be installed , it is evident that the
    amount of scaffolding and formwork is considerably reduced

    DISADVANTAGES

    1. If not properly handled, the pre-cast units may be damaged during


    transport.

    2. It becomes difficult to produce satisfactory connections between


    the pre-cast members.

    3. It is necessary to arrange for specific equipment for lifting and


    moving of pre-cast units.

    4. The economy achieved in pre-cast construction is partially


    balance by the amount to be spent in transport and handling of pre-
    cast members. It becomes, therefore, necessary to locate the pre-
    cast factory at such a place that transport and handling charges are
    brought down to the minimum possible extent.

    CONCLUSION

    Due to problem of pollution control and shortage of land for brick


    manufacturing , the precast concrete block construction is becoming
    very advantageous for building construction day to day.

    Precast concrete block usually are much larger than ordinary bricks
    and so are much faster to lay for a wall of a given size. Furthermore,
    cinder and concrete blocks typically have much lower water
    absorption rates than brick. They often are used as the structural
    core for veneered brick masonry, or are used alone for the walls of
    factories, garages and other "industrial" buildings where such
    appearance is acceptable or desirable. Such blocks often receive a
    stucco surface for decoration
    :
    REFERENCES

    1. S.C. RANGWALA ,“ENGINEERING MATERIALS “, PRADEEP


    PUBLICATIONS, EIGHTH EDITION 1983,PAGE NO.
    179,181,182,209,210.

    2. Dr. B.C. PUNMIA,”BUILDING CONSTRUCTION”,LAXMI


    PUBLICATIONS, SECOND EDITION 1987,PAGE NO.659,669,671.

    3. SUSHIL KUMAR,”BUILDING CONSTRUCTION”,STANDARD


    PUBLICATIONS, EIGHTH EDITION 1981,PAGE NO. 261,262,263.

    4. www.artcretewales.co.uk/case-studies.html

    5. www.leebrickandblock.com/2006/10/

    6. www.askthebuilder.com/505_Concrete_Block.shtml

    Previous
    Next
    :

    You might also like