discussion

what is blinding ?
a layer of link concrete , sand use as blinding

WHat are the purposes of placing blinding under all reinforced concrete
-To form a true level surface


In general ,what would be the proper sequence to construct a reinforced concrete foundation ?

1. Excavation
2. put tumbering
3. but layer of blinding
4. form work
5. reinforcement
6. concreteing
7. remove form work
8. black filling
9. blinding can be form work or interchange

Pile caps

1. Piles are not usually used singly but are formed into a group
2. THe load is distrivuted over the heads of the piles in the group by means of reinforced cast in-situ concrete pile cap
3. Piles should be spaced at such a distance that the group is economically formed and at the same time any interaction between adjacent piles is prevented
4. THe plan shape of the pile cap should be as consercative as possible , and this is usually achieved by having an overhang of 150mm .
5. The main reinforcement is two-directional , formed in bands over the pile heads to spread the loads
6. To provide strucral continuity , the reinforcement in the piles is bonded into the pile cap; this may necesstate the breaking out of the concrete from the heads of the piles to expose the reinforcement .
7. THe heads of piles also penetrate the base of the pile cap some 100 to 150 mm ti ebsyre contitibuity of the members
8. In many piling schemes , especially where capped single piles are used , the pile caps are tied together with reinforced concrete tie beams ,
9. THe beams can be used to carry loadings such as walls to the pile foundations
10. Excavate untul the bottom of pile cap (machine)
11. Manual digging and levelling using hoe ( maan power)
12. Lean concrete about 50mm for easy work area , cutting off piles tops
13. Install pile tap formwork

check your undestanding

Identify and define the following piles by the way in which they transfer their loads to the ground

end bearing ( bearing strata )
friction bearing ( ribbed piles sides )(weak strate )(frictional resistance against pile sides gives support )

Rotary bored piles

1. THe methods of installation of replacement piles have largerly been superseded by the introduction of continuous flight auger , or grout injection piling .
2. This method is highly efficient with exceptionally fast installation possible .
3. A continuous auger of the required length is mounted on a mobile rig and is used to excavate the pile void
4. THe central shaft of the auger is hollow , and is connected to a concrete pumping system , which allow the concrete to be placed as the auger is withdrawn
5. Hence there is no need to provide temporarry support to the sides of the excavation
6. Once the auger is withdwawn , a steel reinforcement cage is forced into the concrete from above
7. THus , the pile is formed quickly and efficiently with little disturbance to surrounding areas

Continuous flight auger

ENd-bearing and friction piles

THis method by which the pile transfer its load to the ground depends upon;

1. The design of the pile
2. The nature of the ground in which it is located

End-bearing and Friction piles

The method by which the pile transfer its load to the ground depends upon ;

End bearing piles acts by passing through unsuitable strata to bear directly upon soil with adequate bearing capactiy

Friction piles are supported by the effects of friction from the ground to the sides of the pile throughtout its length

In practise , all piles derive their support from a combination of these factors

Driven in situ piles

1. Whether in the form of a solid pile or a hollow casing , the driving of the pile casing is aided by the use of a driving toe or shoe , often in the form of a pointed cast-iron fitting at the base of the pile to allow easier penetration of the ground .
2. Considerable levels of noise and vibration are generated as a results of the driving operation . Hence they are generally considered unsuitable for congested sites , where adjacent buildings may be structurally affected , or areas where noise nuisance is undesirable .

Replacement piles

1. Installed by removing a volume of soil and replacing it with a load -supporting pile.
2. SOmetimes referred to as bored piles
3. The holes are bored by using a rotary flight auger .
4. As the excavation progresses , the sides are prevented from collapsing by introducing a shell or casing , or by the use of a viscous liquid called , bentorite
5. THe bentonite is then displaced by concrete as it is poured into the excavation and is stored for further use .
6. THis method is more quiet than the displacement method and does not result in damage to surrounding buildings.

DIsplacement piles

1. Set into ground by forcing or driving a solid pile or hollow casing to the required level below ground , thus displacing the surrounding earth.
2. Generallly driven into the ground by holding them in the correct position against the piling frame and applying hammer blows to the head of the pile .
3. Includes those piles that are preformed or driven in-situ piles

Preformed piles

1. Precast piles of required length may be drive into the ground using a driving rig .
2. ALternatively , the rig may be used to drive a series of short precast sections , which are connected as the work proceeds.
3. The use of second method is the most efficient , since the length required may vary from pile to pile
4. THe use of one piles precast piles inevitably necessitates adjustment of length on site
5. Trimming or extending of one-pieces piles is a difficults task on-sites

Driven in-situ piles

1. The difficulties of providing piles of exactly the correct length , together with the danger of damage to the pile resulting from the percussive driving force , have resultted in the adoption of the use of driven shell or casing piles .
2. With this method , a hollow shell or casing is driven into the ground , using a percussive rig , in a number of short sections , concrete is then poured into the void as the casing is withdrawn , the steel reinforcement having already been lowered into the hole .
3. By this method , an in-situ driven pile is formed in the ground
4. The vibration of the pile casing as it withdrawn from the ground , results in the creation of riged surface to the pile sides , thus taking the most advantage of any frictional support provided by yhr ground

Piles foundations may be definition by instalation method

-Displacement piles (driven )
-Replacement piles (bored )

Definition by load transfer mechanism
-End bearing piles
-Friction piles

Situations which may necessitate the use of piles are :

1. Where insufficient load bearing capacity is offered by the soil at a shallow depth , but sufficient is available at a greater depth
2. Where the nature of the soil at a shallow depth is variable and performance is upredictable , such as in areas of filled land.
3. Where soils at shallow depths are subject to shrinkage or swelling due to seasonal changes .
4. Where buildings are subjected to an uplifting force , and require to be anchored to the ground

Pile foundations may be classified in 2 ways:

1. By the way in whch they are installed
2. BY the way in which they transfer their loads to the ground

Pile foundations

1. Piles are concrete columns , which are either precast and driven ( hammered ) into the ground or cast in holes that are aufered ( drilled ) into the ground down to a level of a firm , stable stratum of subsoil
2. Used to transfer loadings from a higher level to a load bearing medium at a lower level .

Pad foundations

1. Consist of an isolated base under piers or columns.
2. used under point loads such as coluumns , but can be used under ground beams to transfer continuous loads
3. Transfer the loads to a lower level where soil of sufficient loadbearing strats exists
4. Where the subsoil has poor bearing capacity for some depth below the surface , or on made up ground , it is often economic to use iers on pad foundations to support the load of buildings.
5. the piers is function to support the reinforceed concrete ground beams
6. Pits are excavated down to the necessary level , the sides of the excavation temporarily supported and isolated pads of concrete are cast in the bottom of the pits
7. Reinforced concrete piers are cast on the pad foundations up to the underside of the reinforced concrete beams that support walls
8. The piers will be built at the angles , intersection of walls and under the more heabily loaded wall .
9. THe ground beams may be just below or at ground level , the walls being raised off the ground beams
10. THe most economc plan shape is a square , but if the coloumns are close to the site boundary , it may be necessary to use a rectangilar plan shape of equivalent area .
11. THe reaction of the foundation to the load and ground pressures is to cup , and therefore main steel is required in both directions
12. Incorporated in the base will also be the strater bars for a reinforced concrete column

Cellular rafts

1. Used where a reasonable bearing capacity subsoil can be found olny at depths where beam and slab techniques become uneconomic.
2. The construction is similar to reinforced concrete basements excepts that internal walls are used to spread the load over the raft and divide the void into cells
3. Openings can be formed in the cell walls , allowing the voids to be utilised for the housing of services , store rooms or general accommodation

Column splice bars (RC slab ) ( coloumns positioned on wall intersections )

opening in wall and

beam and slab raft(downstand beam and slab raft foundation

1. An alternative to the solid slab raft
2. Used where poor soils are encountered
3. The beams are used to distrbute the column loads , over the area of the raft , which usually results in a reduction of the slab thickness .
4. THe beams can be upstand or downstand depending upon the bearing capacity of the soil near the surface .
5. Downstand beams will gice a saving on excavation costs , whereas upstand beams create a usable voids below the ground floor if a suspended slab is used .
6. Reinforced concrete or steel columns posioned on beam intersections in the centre , reinforced concrete raft spanning over ground beams
7. The reinforced concrete ground beamm is used on poor soils where the beams are employed to spread the column loads over the raft

Wide toe rafts foundations

Where the ground has poor compressibiliry and the loads on the foundations would rewuire a thick & uneconomic flat slab , it is usual to cast the raft as a wide toe raft foundation

1. Recommended for buildings in areas subject to mining subsidence ,
2. Cast on a bed of fine granilar material 100mm thicj so that the raft is not keyed to the ground
3. THe raft is cast with a reinforced concrete stiffening edge beam from which a reinfoced concrete toe extends as a base for the external leaf of a cavity wall.

THe cavity wall is on side of the houses ,and the edge beam with wide toe to support the wall .Then inside the buildings still have an internal load bearing wall , the first layer is 50mm finish ground and the seconf the the reinforced concrete raft and the third is the damp proof membrane and the last 1 is100 mm hardcore with 50mm blinding .

solid slab raft foundation

1. The ground must be at least 50mm thick , and the center must be put a insulation and the second lower layar is 150mm reinforcement concrete with damp proof membrane , the last 1 is 50mm blinding concrete
2. The effect of the load from columns and the ground pressure is to create areas of tension under the columns and areas of tension in the upper part of the raft between the columns ,
3. Thus , the concrete raft is reinforced top and bottom against both upward and downward bending ,
4. A nominal mesh of reinforcement is provided in the faces where tensuon deos not occur to control shrinkage cracking of the concrete

Raft foundation

1. Consist of a raft of reinforced concrete under the whole of a building.
2. Design to spread the load over the whole building area , reducing the load per unit area .
3. Distributing the load in this way causes little % uniform settlement .
4. Used for buildings on compressible ground such as very soft clay and compressible fill material where strip , pad or pile foundations would not provide a stable foundation without excessive excavation .

Raft foundation can be considered under 4 categories :

Solid slab raft

1. Sometimes called flat slab raft foundation .
2. Construction of uniform thickness over the whole raft area ,
3. Can be wasteful because the design must be based on the situation existing where the heaviest load occurs
4. Used under small buildings such a bungalows and two storey houses where the comparatively small loads on foundation scan be spreas safety and economically

Distribution of forces in a strip foundation

1. Reinfoced concrete strip foundations are used to support and transmit the loads from heavy walls .
2. THe effect of the wall on the relatively thin foundation is to act as a poit load , and the resultant ground pressure will induce tension on the uderside across the width of the strip
3. Tensile reinforcement is therefore required in the lower face of the strip , with distrivution bars in the second layer running longitudinally
4. The reinforcement will also assist the strip in spanning any weak pockets of soil encountered in the excavations

Wide strip foundations

1. Strip foundation on subsoild with poor bearing capacity , such as soft sandy clay , may need to be considerably wider than traditional strip foundation
2. However , to keep increasing the width and depth of the concrete ensuring that the foundation does not shear makes the process unconomical ,
3. THe alternative is to dorm a strip of steel-reinforced concrete.
4. Concrete is strong in compression , but is weak in tension
5. THe effect of the downward pressure of the wall on the middle of the foundation and the opposing force of the ground spreas across the base of the foundation attempts to bend the foundation upwardsl this places the top of the foundation in compression and the base of the foundation in tension .
6. TO add tensile properties to the foundation , steel reinforcing bars are cast in the lower edges where tenson will occurs.
7. THere has to be a sufficient cover of concrete below the steel reinforcing rods to ensure a good bond between the concrete and steel and to protect the steel from corrosion

Narrow strip foundations

1. Stiff clay subsoils have good bearing strength and are subject to seasonal volume change
2. Because of seaspnal changes , it is practice to adopt a foundation depth of at least 0.9m to provide a stable foundation
3. A deep strip foundation will go to a depth where the clay soil is unaffected by seasonal changes .
4. Also known as deep strip foundation or trench fill foundation.
5. Because of the good bearing capacity of the clay , the foundatuion just need to be little wider than the thickness of the wall to be supported.
6. Trenches are usually formed by using mechanical excavators
7. THe trench is filled with concrete as soon as possible so that the sides of the trench do not fall in and the exposed clay bed does not dry out and shrink.

(cavity wall , brick cuter and concrete block inner skin) (load bearing internal wall )

Dimension of a strip foundations

cavity wall, internal load bearing wall
min 150 mm thick strip concrete foundation
thickness of the foundation should be equal to p or 150 ,, , whichever is greater.
wall should be central on foundation

1. Dimension of strip foundations
2. If the thickness of a concrete strip foundation (without steel reinforcement ) were less than its projection each side of a wall , the concrete might fail through the weight of the wall causing 45 degree shear crack
3. If this occured , the bearing surface of the foundation on the ground would be reduced to less than that necessary for stability
4. Where the load is place directly on top of the concrete foundation and compressed between the ground , the foundaton remains stable . However , the concrete outside the 45 degree angle experience some tension as the reaction of the ground attempts to lever the foundation upwards , this the foundation would fail.

tranditional strip foundations

1. THe width of a concrete strip foundation depend on the bearing capacity of the subsoil and the load on the foundation .
2. THe greater the bearing capacity of the subsoil , the less the width of the doundation and vice versa
3. The concrete strip will generally be wider than the thickness of the wall L

• For the convenience of filing a wider trench with concrete , due to the width of the excavation bucket
• For the convenience of laying brick below ground , allowing adequate working space .
• THe minimum width of a strip foundation is 450mm which gives a resonable bearing area for most two storey houses on most subsoils.
• The practical minimum depth of a strip foundation is usually 450mm to allow for the removal of top soil and variations in ground level.
• THe minimum thickness of concrete for a strip foundation is generally 150mm and the concrete should be at least as thick as the projection of the strip each side of the wall where the concrete is not reinforced.

reinforcement concrete foundation(mass concrete foundation )

foundation tend sto bend , the uper fibres being compressed and the lower fibres being strencthed and put in tension-remedies increase size of base or design as a reinforced concrete foundations.(imposed loads induces tensile stresses in excess of concrete own resistenace)

Size of foundations increased to provide the resistance against the induced tensile stresses -generally not economic due to the extra excavation and material required
(wall or column )


reinforced concrete foundation
strip foudation

1. Consist of continuous strip foundation of mass or reinforced concrete , formes centrally under loadbearing walls.
2. Used to transfer long continuous loads such as walls.
3. THe continouos strip serves as a level base on which the wall is built.
4. THe most economic form of foundation for small buildings on compact soils.

building construction lecture 3

design & construction of reinforcement concrete foundations

1. Foundations are usually made of either mass or reinforced concrete.
2. Where a structure has olny light loadings , such as a domestic building , it is sufficient to use a mass concrete foundations .
3. Where buildings are either heavy , or transmit the loadings at a series of points , such as in a framed buildings , it is uneconomic to use mass concrete foundation.
4. Where byulding either heavy or transmit the loadings at a series of points , such as in a framed building , it is uneconomic to use mass concrete foundation.
5. The thickness of a mass concrete foundations for a heavy point load would result in a foundation that is costly and adds unnecessary load to the subsoil.
6. Reinforced concrete foundations are generally cheaper and easier to construct than mass concrete foundations but will require a structural engineer to formulate an economic design .
7. The engineer must define the areas in which tension occurs and specify the reinforcement require , as concrete is material which is weak in tension
8. Concrete is a mixture of cement , sand , aggregates and water in controlled proportions .
9. It is the most suitable material to construct foundation as it is a durable material of adequate strength
10. But concrete is a material which is strong in compression but weak in tension .
11. If its tensile strength is exceeded , cracks will occur and resulting in a weak and unsuitable foundation.
12. One method of providing tensile resistance is to include steel bar as a form of teinforcement in the concrete foundation to resist all the tensile forces induced into the foundations .
13. Steel is material which is readily available and has high tensile strength.

Topic 1: Groundwork & Foundations

He Bab 3 Pluraliti dan masyarakat Pluralistik Di Malaysia 3

Sememangnya tidak dapat dinafikan bahawa sejumlah besar ilmu saintifik sosial mengenai Alam Melayu selepas penjajahan Eropah telah dijana , dihasil dan dikontekstualisasikan dalam rangka kerja masyarakat pluralistik kerana negara bangsa sebagai suatu kategori analitikal lebih diutamakan . Sebagai contoh , kaum Penan do Borneo Tengah ( seperti juga nenek moyang mereka ) telah berpindah-randah dengan bebasnya ke sana sini antara Indonesia dan Malaysia demi mencari rezeki untuk meneruskan hidup bersama-sama dengan kelompok suku lain dan para pedagang luar tanpa mempedulikan kewujudan sempadan politik , Namun demikian , ahli antropologi kelihatan begitu selesa dalam kepalsuan dengan kegharahan analitikal m saintifik dan akademik mereka untuk memisahkan kaum penan Indonesia dan Malausia sefangkan pada hakikatnya mereka merupakan makhluk manusia yang satu dan sama.

Sebagai guru dan penyelidik dalam bidang kemanusiaan dan sains sosial , tugas utama adalah untuk memisahkan hakikat sebenar daripada konstrksi sosial . Tugas ini bukanlah sesuatu yang mudah tetapi percubaan mesti dilakukan . Semoga dengan itu , kita berada pada kedudukan lebh baik utntuk memahami bagaimana kajian Alam Melayu sebagai satu korpus ilmu telah diguna pakai di luar dunia akademik.

Pola masyarakat pelbagai bangsa pada zzaman sebelum kedatangan orang Eropah terbentuk melalui proses semula jadi , Mereka datang berdagang secara sukarela untuk mencari kehidupan dan kekayaan , Kedatangan mereka disertai bersama oleh ahli keluarga . Jika mereka mengambil keputusan untuk terus menetap di Alam Melayu , mala sudah tentu keputusan itu merupakan keputusan berasaskan persetujuan sebulat suara bersama ahli keluarga masing-masing , Keputusan hidup yang terhasil daripada persetujuan tanpa paksaan menjamin ketenangan fikiran dan perasaan mereka , Hasilnya , mereka berjaya mewujudkan interaksi yang mesra dengan penduduk tempatan , Terdapat unsur-unsur akomodasi dalam kehidupan masyarakat pluralistik pada zaman tersebut . Mereka secara sukarela sanggup berkahwin dengan penduduk tempatan . COntohnya , masyarakat Cina Baba ialah keturunan Cina yang telah berkahwin dengan masyarakat tempatan , Di samping itu , mereka juga mengamalkan budaya kehidupan orang Melayu , Selain itu , amalan dan adat resam yang dibawa masuk oleh mereka juga diterima pakai oleh penduduk tempaan . Adat bersandng , bunga manggar dan bunga telur

He Bab 3 Pluraliti dan masyarakat Pluralistik Di Malaysia 2

Diskusi di atas memperlihatkan ciri-ciri masyarakat Alam Melayu hidup dalam kepluralitian semula jadi yang terjadi tanpa paksaan oleh mana-mana pihak atau kuasa . Ciri kepluralitian Alam Melayu sebelum kedatangan orang Eropah yang fleksibel ini dirompak , diubah suai dan sebahagiannya terhapus dengan kedatangan kuasa kolonial dan imperial Eropah . Mereka seterusnya memperkenalkan sistem kerajaan mereka yang menggalakkan perkembangan masyarakat pluralistik .

Akibat daripada terlaksanannya undang-undang kolonial dan bertapaknya masyarakat pluralistik serta kemudian diikuti dengan terbentuknya negara bangsa m rangka dan cara mengupas perkembangan baharu ini juga turut mengalami perubahan . Kini , para penganalisis semestinya mengambik kira realiti masyarakat pluralistik seta perkembangan selanjutnya yang dijana oleh kewujudan satu masyarakat pluralistik di wilayah ini . Kita mula menyempitkan fokus kupasan kita kepada hal ehwal dalam sesebuah negara , kumpulan etnik , hubungan antara negara bangsa permasalahan dalaman satu-satu negara bangsa , nasionalisme dan sebagainya . Perkembangan ini telah mewujudkan apa yang dikenali sebagai nasionalisme metodologika ( methodological nationalism ) , satu cara membina dan menggunakkan ilmu berasaskan kewlyahan sesebuah negara , Metode ini mengetepikan konsep yang menganjurjan bahwa kehidupan sosial merupakan suatu fenomena sejagat dan tanpa sempadan , maka hasilnya wujud apa yang dikenali sebagai kajian-kajian Indonesia , Filipina , Malaysia dan seterusnya .

Kerangka rujukan menjadi semakin semput dengan kewujudan Perang Diingin dan teori modenisasi , Para penganalisis membincangkan isu-isu kemiskinan dan keperluan asas di pedesaan negara tertentu , memfokuskan perhatian kepada penentangan dan peperangan , kawasan dan penduduk miskin di bandar dan pembangunan ekonomi dalam kalangan petani dan pekebun kecil . Isu-isu yang ditumpukan oleh disiplin tertentu ( seperti antropologi ) menjadi semakin sempit apabila difokuskan kepada komuniti tertentu di kawasan terpencil , peperangan khusus di kawasan pergunungan , projek pengairan yang gagal atau identiti gender etnik minoriti di bandar

He Bab 3 Pluraliti dan masyarakat Pluralistik Di Malaysia

Pengenalan
Pluralisme budaya bukan fenomena baharu dalam Alam Melayu , Interaksi antara pelbagai budaya seperti Arab pra-Islam , Hinduisme,Buddhisme,Arab Islam dan Eropah ( yang diwakili oleh Portugis , Sepanyol , Belanda dan British ) dengan budaya Alam Melayu telah berlaku sekurang-kurangnya sejak abad ke-5 Masihi lagi. Pertemuan dan pertembungan budaya-budaya besar dunia tersebut telah melahirkan satu ciri fenomena sosial yang istimewa dalam Alam Melayu , iaitu denomena kepluralitian budaya. Justeru , bab ini akan menjelaskan hakikat sejarah tersebut yang akan dibahagikan kepada dua tahap utama , iaitu kepluralitian budaya dalam Alam Melayu dan dikikuti dengan kepelbagaian budaya di Malaysia .

Pluralisme budaya Alam Melayu
Dua konsep utama yang sering digunakan untuk menjelaskan ciri Alam Melayu ialah pluralisme dan masyarakat pluralistik (plural society ).Kedua-dua konsep ini merupakan konstruksi saintifik sosial yang terhasil daripada kajian emporikal yang dilakukan di wilayah ini . Apabila para sarjana melakukan penyelidikan dan menulis mengenai Alam Melayu sebelum kedatangan Eropah , mereka pasti mengambil kira reality kepelbagaian Alam Melayu pada waktu itu sebagai satu wilayah yang menjadi tempat pertemuan pelbagai tamadun dan budaya utama dunia. Tiupan angin dan arus laut bersatu membawa manusia dari seluruh dunia yang didorong oleh serampang tiga mata utama , iaitu pengembangan agama kekayaan dan kemegahan ( Gospel , Gold and glory ). Hasilnya , di jawa terdapat seorang raja Hindu yang menggunakan nama arab dan melayani para pedagang Eropah . Di Champa , raja Melayu seta rakyat baginda yang beragama Hindu (selepas abad ke-16 terdapat dalam kalangan raja champa yang telah menganut agama Islam ) menjalankan urusan perniagaan dengan negara India , Vhina dan Kepulauan Melayu . Ertinya , rangka kerja pluralisme tidak dapat dielakkan dalam kajian mengenai jangka masa tersebut yang merangkumi kepelbagaian budaya dan tradisi berwarna-warni .

consistency of concrete

1. Describe the state of fresh concrete
2. Measure of wetness of fluidity
3. Wet concrete are more workable than dry concrete

Describtion

-mobility

• The ease which the mix can flow into and completely fill the formwork or mould

-Compactability

• The ease with which a given mix can be fully compacted , all ( most of ) the trapped air being removed

Workability

Full compaction

High density

Good strength of concrete

Consistency

-Describe the stete of fresh concrete

-Measure of wetness of fluidity

-wet concrete are more workable than dry concrete

What is workability

• The ease with which a concrete mix can be handled from mixer to its compacted shape
• The amo unt of mechanical work , or energy , required to produce full compaction of concrete without segregation

#3main characteristics:

• Consistency
• Mobility
• Compactability

Factors to achieve good concrete mx design:

1. Well graded aggregates
2. Material batched by weight
3. Low water /cement ratio

• Enough for hydration , compaction , workability
• Not too much water -voids

Factors to achieve good concrete mix design

THese factors have been discussed in previous chapters . THe following served as a summary of what you have learnt :

1. Suitable material :

• Quality of water-drinkable
• Clean & suitable aggregate
• Correct types of cement

Factors affecting Properties of concrete

• W/C ratio
• Agg /cement ratio
• Grading , surface texture , shape , strength and stiffness of aggregate particles
• Maximum sie of aggregate
• Temperature
• Age of concrete
• Curing
• Frost
• Entrained air

Measurement of ingredient of cement concrete

• Cement

-by weight

• Fine aggregates

-By weight

-But for ordianry works or if facil ities of weighing are not available , it can be by volume . Hoevert , allowance for bulking must be kept in view .

Coarse aggregate

-By weight or volume ( no problem for bulking )

Water

-By volume ( 1kg=1 littler )

-Adjustment should be made for the present of water in sand and aggregates

Concrete mix design

To achieve maximum strength and maximum durability

Learning outcome
-upon completion of this section , you should be able to :

• Describe the meaning of workability
• Outline the test for workability ; namely slump test , compaction factor test and vebe consistometer test

Concrete ( fresh concrete , workability )

• Is an artificial material , obtained by mixing together cement , coarse aggregates , fine aggregae and water m in suitable proportions
• All these ingredients ,when freshly mixed , produce a plastic mass which can be poured into suitable forms or moulds , to give desired shapes to the resulting solid mass

water repellers

-Decrease permeability
-Prevent absorption of rain water

Superplasticisers

1. Same as water reducer : but more effective
2. Disperse by coating cement partivles thus separating and dispersing the cement in the water phase
3. Use to faciliiitate placing e.g pump mix ( high workability ) give early and extremly high strength and durability ( reducton of w/c ratio )
4. Adverse effect : increase bleeding and segregation tendency , increase shrinkage

Retarder

1. Delay onset of setting and hardening i.e extending the time between initial mixing and final compaction
2. Use in how weather where large concrete pour
3. Frequently used in ready-mixed concrete
4. Uses influenced by aggregate type and grading
5. Do not adversely affect 28-day strength
6. Adverse affect : increase bleeding with some types , increase drying shringkage , reduction early - strength development

Bonding agent (Concrete)

1. Increases bond strength between new and old concrete surface ( sometimes cement -paste slurry is been used )
2. Use for pactching and remedial work
3. Adverse effect : some reduction in compressive strength

Water reducer

1. Increase workability or slump ( if w/C remain ) , strength ( reduce water ) ;
2. Reduce cement and water content ( given same workability and strength )
3. Use to facilitate placing or to give higher strength and durability
4. Adverse effect : increase drying shringkage ; some types may incrase bleeding and retard the setting time

accelerators of formation of concrete (setting )

1. Calcium chloride ( most common ) , calcium formate
2. Increase rate of setting and hardening
3. High heat evolution
4. Use in winter and rapid removal of formw
5. Adverse effect : increase drying shringkage reduce resistance to sulphate attack , > 2% calcium chloride > corrosion of rebar

Accelerators

1. Should be chloride -free eg. calcium formate to avoids metallic corrosion and reduction in concrete strength
2. affect setting olny
3. use for emergency repair work

( stop pressure leaks )

Types of admixtures

1. Air -entrainers
2. Accelerators
3. Retarders
4. Water reduces
5. Superplasticisers
6. Bonding agents
7. Water Repellers

Admixtures affect

Hydration
Leberation of heat
Formation of pores
Development of gel

To achive

Workable , fhinishable , strong , Durable ,
and watertight concrete

olny consider admixtures when other methods dont work or not economical

Air -Entrainer

1. Formation of small stable discrete bubbles
2. improved workability ( high slump )
3. Increase resistance to frost action
4. Reduction in bleeding and water gain
5. Use for road and runway construction
6. Adverse effect : some reduction in strength
7. The incorporation of void space within concrete decreases its crushing sttrength by 6% for every 1% of air -entrained . However , it is partially offset by using lower water content .

olny consider admixtures when other methods dont work or not economical

Air-Entrainer

1. Formation of small stable discrete bubbles
2. Improved workability ( higher slump )
3. Increases resistance to frost action
4. Reduction in bleeding and water gain
5. Use for road any runway construction
6. Adverse effect : some reduction in strength
7. The incorporation of voids space within concrete decreases its crushing strength by 6% for every offset by using lower water content

Amixture vs additive

• Admixture

1. Substance ( other than cement , water aggregates or rebar ) added during or immediately before mixing to improve / Alter the properties of concrete ( eg . accelerators )
2. -note : doses are usually very small ( less than 1 % )

• Effect very sensities to variation in dose
• side effect

1. Additive

• Substance added by cement manufactureres to midify properties of cement ( eg. Gypsum )

strength

The strength of water/cement is inversely with strength

Admixture

1. Other than using special cement , admixture can be used to change certain properties in concrete more effectively
2. To reduce cost of concrete construction
3. To ensure quality of concrete during mixing , transporting , placing a, and curing in adverse weather conditions
4. To overcome certain emergencies during concreting operations

Seawater

Does not have adverse effect on the strength and durability of concrete but will cause :

1. Surface dampness
2. Efflorescenes
3. staining
4. Risk of corrosion of steel
5. More rapid and early strength gain but 28-day strength will be lower i.e. 10-20 % ( can be compensated for by using a lower W/C ratio )

How much water to use to make concrete

1. common to use 0.4-0.6 water / cement ratio
2. olny 0.23 is required for hydration
3. Extra water required for hydration and compaction
4. If not enough water , compaction not done properly , result in high porosity

Maximum permitted concentration of various harmful element As suggested by 1.s.1

1. Organic solid 0.02%
2. Inoganic solid 0.03%
3. Sulphates 0.05%
4. Alkali chloride 0.10%

TOlerable level of impurities in mixing water

Impurity
Suspended matter (urbidity ) - 2000 - silt , clay , organic matter , entrain air , decrease setting times 400 ppm for

Algae- 500-1000 - Entrain air

Carbonates -1000 - Decrease setting times

Bicarbonates - 400-1000 - 400 ppm for bicarbonates of ca, MG


Sodium sulphate - 10000 - may increase early strength , but reduce later strength

Magnesium sulphate - 40000 strength , but reduce later strength

sodium chloride - 20000 0 decrease setting times

Calcium chloride - 50000 - Increase early

Magnesium chloride - 40000 - strength reduce , ultimate strength


Iron salt -40000 - retard set
phosphates arsenates , borates - 500 - retard set
salts of Zn , Cu , Pb , Mn , Sa -500 - retard set
Inorganic acids - 10000 , ph not less than 3.0
sodium hydroxide - 500 -
spdium sulphate -100- should stest concrete affect setting behavior
sugar - 500 - ,,

Learning outcome

-upon completion of this section you should be able to :

1. describe the requirement of suitable water for mixing concrete
2. Explain the usage of the main types of admixtures used in mixing concrete

Quality of mixing water : BS3148

Drinking water & tap water

Ph of 6.0 to 8.0 or possibly even 9.0

concrete ( water & admixture )

-Function

1. Chemical reaction with cement and thus causing it to set and harden
2. Lubricate the aggregates in concrete
3. Mixing , placing and compacting concrete
4. Washing aggregates
5. Curing

Why use clean water ?

• Impurities in water ( large quantity of suspended solids , excessive amount of dissolved solids , or salts , or appreciable amount of organic materials ) will :

1. Affect setting
2. Affect strength
3. Cause staining on concrete surface
4. cause corrosion of reinforcement
5. Drying shrinkage
6. Efflorescene
7. Acidic water affect setting and hardening of concrete ; alkaline water = quick setting and low strength

Single sized and well graded aggregates

uniform size aggregate

1. position at few point of contact
2. Poor interlocking
3. High percentage of void

Well graded aggregates

• Position at many point of contact
• Excellent interworking

Mixture of coarse and fine aggregate

1. friction at many point f contact
2. Good interlocking
3. Few voids
4. Economical preparation

Single sized and well graded aggregates

uniform ( single sized aggregate )

- A large percentage of particles are approximately the same /one size

-Gap grading is defined as grading in which one or more size fractions ( intermediate size ) are of very few % or omitted

Grading of aggregate

1. Particle size distrivution of aggregate is called grading
2. Expressed in terms of % by weight retained on a series of sieves
3. 80mm,40mm , 20mm , 10mm and 4.75mm sieves are used for grading of coarse aggregate
4. 10mm , 4.75 mm , 2.36 mm , 1.18mm , 600-UM , 300UM , 150um are used for fine aggregates

Well

-Consist of aggregates with different sizes and are approcimately equal amount , although there wll be very small amounts of the largest and the smallest particles

-Fill as much as possible of the total space
-Voids between particles can be filled efficiently with slightly smaller ones

Grading of aggregates

-Objective -to assist in producing concrete with

• Satisfactiry plastic properties ( workability , cohesion , resist bleeding )
• Satisfactory hardened properties ( strength , durability , surface finish )

1. There is no universal ideal grading for the aggregates

Colorimetric test

-result:

• The darker the colour , the greater organic impurities
• If colour is darker than the standard yellow colour specified ( colour chart available for checking ) the aggregates has high organic content .

test for ascetaining the amount of organic impurities in fine aggregates

1. put the aggregates in the bottle
2. put 3 percent of soudium hydroxide into the bottle
3. allow to stand for 24 hour
4. examine colour of the soulution
5. Soulution with organic material will be suspended at the bottom of the bottles

Cleanliness of clay silt and dust

-Present in gravel and sand depost as surface coating
-Large quantity may reduce strength of concrete due to weak bonding

• Salt contamination

1. Sand from seashore
2. Can be removed by washing
3. If high level , salt may cause efflorescence in concrete and corrosion of steel reinfrocement

Cleanliness of aggregates

• Should be clean and free from the following :
• Organic impurities

1. Organic matter such as decay of vegetable matters
2. interfere with hydration process
3. Washing may remove organic impurities in sand

surface texture of aggeregates

Glassy-conchoulat fracture- black fiat m vittrevous slag

Smooth- water-worn , or smooth due to fracture of laminated or fine-gained rock

Granular- Fracture showing more or less uniform rounded grainins-sandstom , oolite

Rough- Rough fracture by fine or medium grained rock containing no easily visible crystalline constituents-basalt , feteite , porphyry , limestone

Cystalline - Containing easily visible crystalline constutuents - Grmite , gabbro , gneiss

Honeycombed - With visible pores and cavities -Brick , pumice , formed slag , clunker , expanded clay

Shapes and texture summary

-Angular shape and rough texture aggregates -Provide highest bonding strength
-Rounded shape and smooth texture aggregates- provide best workability but lower strength

types of shapes

Angular , rounded , flaky , elongated , flaky and elongated

shapes classificication

Rounded-Fully water worn or completely shapes by attraction -river or seashore , gravel deset , seashote , and wind-blown sand

Irregular-Naturally irregular , or partly shaped by attrition habing rounded edges

Flaky -Material of which the hickness is small relative to the other two dimensions

Angular -Possesing well -defines edges formed at the intersection of rough planar faces-Crushed rocks of all types , talus , crushed slag

Elongated - Material , angular , in which the length is considerably larger than the other two dimension

Flaky and elongated -Material having the length consderatbly larger than the other two dimension

Flaky and Elongated-Material having the length considerably larger than the width , and the width considerably lager than the thickness

Surface texture of concrete

surface texture

• Rough

1. Provide better bonding strength
2. Lower workability

• Smooth

1. Weaker bond
2. Higher workability

• Glassy

1. Should be rejected

• Other

1. Good bond

Shapes and texture

-Shape

• Rounded ( about 35% vold)

1. Less specific surface area
2. Weaker bond
3. Better workability
4. Does not give high strength concrete

• Irregular

1. High surface area
2. Good bond
3. Low workability
4. Does not give high strength concrete

Shapes and texture affect the strength and workability of concrete

• Angular ( about 40 percent vold )

1. Provide highest specific surface area
2. Provide better bonding therefore better strength of concrete
3. Lower workability

• Flat , Elongated or flaky

1. Obkectionable
2. Weaker bond
3. Lower workability
4. Does not give high strength concrete
5. % of elongated and flaky of aggregates should not more than 10-15 percent

Properties / characteristic

1. Shapes / texture
2. Cleanliness
3. Bulking
4. Grading
5. Strength
6. Density

Classification of concrete

-Heavyweight

1. Contain heavy metal atoms such as iron
2. Concrete density 4000 to 8500 kg/M3 ( very high density )
3. Uses to resist force of flowing water , nuclear -radiation -shielding

-Normal /Ordinary weight

1. Natural or artificial
2. Suitable for most purpose
3. concrete density =2300 to 2500 kg/m3

-lightweight

1. Natural or artificial
2. Bulk density =350 to 850 kg/m3 for coarse and 750-1100 kg/m3 for fine aggregates ( low density )
3. High porosity , less strong and specially prepared
4. To reduce weight for the upper parts of a structure
5. To insulate concrete
6. Has tendency to stain concrete surface ( iron compounds washed out by rain )

Source of concrete

-Natural

1. Crushed rocks , sand and gravel
2. From river beds , quarries , sea -beds , cooled volcanos

-Artificial ( man -made )

1. Broken bricks , blast furnace slagg