modul 1 - pengenalan beton

7/22/2019 Modul 1 - Pengenalan Beton

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Modul 1

Pengenalan Beton dan Sifat-sifatnya

Semen Portland / Portland

Cement (PC)


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Pengenalan semen

Pengenalan batu dan pasir

Pengenalan admixtures dan additions

Pengenalan sifat-sifat beton Beton segar

Beton keras


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5


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Pasta = semen + air

Mortar = semen + pasir + air

Beton = semen + pasir + batu +air

Berat jenis Air = 1

Semen = 3.15

Pasir = 2.60

Batu = 2.65


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Semen berwarna ke-abu-abuan Particle size 45m passing #325 sieve

Fungsi gypsum Mengatasi semen bereaksi terlalu cepat

Mengatur strength development

Untuk mengatasi shrinkage

Dalam kimia semen, oksida dan gabungandinyatakan dalam bentuk singkatan sepertiditunjukkan dalam tabel di bawah ini

Oksida Singkatan. Gabungan Singkatan

CaO C 3CaO.SiO2 C3S

SiO2 S 2CaO.SiO2 C2S

Al2O3 A 3CaO.Al2O3 C3A

Fe2O3 F 4CaO.Al2O3.Fe2O3 C4AF

SO3 S CaSO4.2H2O CSH2

H2O H


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Unsur Gabungan Semen Presentaseberdasarkan berat

Tricalcium silicate (3CaO. SiO2) 40%-60%

Bicalcium silicate (2CaO.SiO2) 15%-30%

Tricalcium aluminate (3Cao. Al2O3) 10%

Calcium ferroaluminate (4CaO.Al2

O3

.Fe2

O3

) 8%

Gypsum (CaSO4.2H2O) 5%

Alkalis 0.3%-1.5%


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Tipe semen Portland Type I Semen Portland Normal (OPC)

Type II and V Semen Portland Tahan Sulfat

Type III Semen Portland Kekuatan Awal Tinggi

Type IV Semen Portland Panas Hidrasi Rendah

Air Entraining Portland Cement

dll

Komposisi kimia semen

Komposisi senyawa

Berdasarkan ASTM C-150 StandardSpecification for Portland Cement, andAASHTO M-85 I Normal IA Normal, Air entraining II Moderate sulfate resistance or heat IIA - Moderate sulfate resistance or heat, Air

entraining III High early strength IIIA High early strength, Air entraining IV Low heat of hydration V High sulfate resistance


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Penggunaan Umum

Ready-mixed pemakai terbesar

Paling umum, 90% semen type ini

Type II moderate sulfate resistance

Type V High sulfate resistance


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Batu dan Pasir


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Keringudara

JKP/SSD Basah Kering Oven

waterwaterwater

100xOvenKeringBerat

OvenKeringBerat-SemulaBeratAirKadar =


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Specific gravity is defined as the ratio of the massof a material to the mass of the same volume ofwater

Where Ms = Mass of the materialVs = Volume of the materialw = density of water

ws

s

V

MS.G.=

Bulk S.G can be obtained in terms of :

SSD mass (B), oven dry mass (A) and buoyantmass (C) as follows:

C-B

AS.GBulk =


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If the aggregate used is in SSD condition thenthe mass of water in the permeable poresshould be included in the Bulk S.Gcalculations and the S.G. is known as BulkS.G.SSD.

Bulk S.G.SSD can be given in terms of SSDmass B and buoyant mass C as follows

C-BBS.GBulk SSD =

If the permeable pores are excluded from thetotal volume of the aggregate then theresulting S.G. is known as apparent S.G.

Apparent specific gravity can be obtained in

terms of oven dry mass A, and buoyant massC as follows:

C-A

AS.G.apparent =


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If the three specific gravities are comparedthen: apparent S.G. > bulk S.G.SSD > bulk S.G.

The decision to use which one of the threedifferent specific gravities mentioned abovedepends on the moisture condition of the

aggregate and the application i.e. concrete,asphalt, fill etc.

Gradation is synonymous of particle sizedistribution.

In concrete the amount of paste needed forproduction depends entirely on the particle

size distribution of the aggregate, here pastefills the voids remaining from the aggregates,so more or less paste will be neededdepending on how well smaller particles ofaggregate occupy spaces left by largerparticles. Its a matter of particle sizedistribution.


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To a grand extent, the properties of fresh andhardened concrete will depend on the amountof aggregate packed, as well as the amountof paste present and of course the water tocement ratio. A well distribution of sizeparticles in an aggregate will make a concreteless susceptible to segregation in the fresh

state, and more stable to volumetric changeswhile it develops its designed strengthsuccessfully.

Nominal size of an aggregate (used in normalpractice) is the smallest sieve opening throughwhich most but not all the particles pass.

Maximum size of an aggregate is the maximumsieve size through which all the aggregate will pass.

It is important to focus on the larger particle sizes,when ordering concrete for a given job to avoidinterference with the formwork and reinforcingwhile placing the concrete.


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250 grams of sand was sieved using standardsieves. The mass retained on each sieve isshown in the table below. Plot the cumulativepassing gradation for this sand.

Sieve No. Mass retained (g)

No. 4 0

No 8 27

No. 16 35

No 30 89

No. 50 72

No. 100 23

Pan 4

SieveNo.

Massretained

(g)

%retained

Cumulative% retained

Cumulative% Passing

No. 4 0 0 0 100

No 8 27 10.8 10.8 89.20

No. 16 35 14 24.8 75.20

No 30 89 35.6 60.4 39.60

No. 50 72 28.8 89.2 10.80

No. 100 23 9.2 98.4 1.60

Pan 4 1.6 100 0


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Limits are shown in the next table.

Sieve Size Min. % Passing Max. % Passing

3/8 in 100 ---

No. 4 95 100

No. 8 80 100

No.16 50 85No. 30 25 60

No. 50 5 30

No. 100 0 10

No. 200 0 3


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Sand gradation can be assessed by a singlefactor known as fineness modulus (FM).Fineness modulus is determined by adding upall the percentage cumulative retained onsieve No.100 to sieve No. 4 and then dividethe sum by 100.

100

RetainedCumulativePercentageFM =

Considering previous data from gradation:

For Indiana upper limit:

For Indiana lower limit

83.2100

98.489.260.424.810.80FM =

+++++=

85.3100

10306085100100FM =

+++++=

55.2100

0525508095FM =

+++++=


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It can be seen that for coarser sand (upperlimit) FM value is larger. For finer sand (lowerlimit) FM is smaller, and for data fromgradation FM lies in between the valuesabove.

Fineness modulus is used for quality controlof sand. It allows to asses whether there is

any variation in sand gradation from batch tobatch.

Admixtures and Additions


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Type A.- Waterreduc ing admixtures Improve workabil ity an dens ity of concrete

Type B.- R etarding admixtures For large casting volumes and hot weather

Type C.-Accelerating admixtures Early strength, quic k formwork removal and cold

weather concreting

Type D.- Water-reducing and retarding admixtures Similar to A and B

Type E.- Water-reducing and acceleratingadmixtures

Similar to A and C

Type F.- Water-reducing, high range admixtures High early strength, improve workability and watertightness

Type G.- Water-reducing, high range, and retarding

admixtures

Similar to B and F


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A B C D E F G% water

reduction

7-10 - - 7-10 7-10 12-30 12-30

Time setting earlier delay delay earlier earlier earlier delay

Compressive

Strength

increase decrease same increase increase increase Increase

FlexuralStrength

same decrease decrease same same same same

Length

Change

affect affect affect affect affect affect affect


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Pengenalan Sifat-sifat Beton

Kecocokan materials (suitable materials)

Proporsi campuran (mixture proportions)

Mixing dan transportasi

Pengecoran dan konsolidasi (placing and

consolidation)

Finishing and jointing

Curing

Lingkungan (environment)


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Sifat-sifat Beton Fresh


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Sifat-sifat Beton Keras


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Kuat tekan (compressive strength) yangpaling sering dipergunakan untukmengetahui mutu beton untuk dipergunakandalam: Perhitungan desain

Spesifikasi

Quality control


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modul 1 - pengenalan beton

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