Prakash Lecture 28-1-10

8/9/2019 Prakash Lecture 28-1-10

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BASICS OF CONCRETE TECHNOLOGY

by

Prakash Channappagoudar, VP (Structural Designs), SKA/TEBS


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Concrete PropertiesConcrete Properties

VersatileVersatile

CheapestCheapest

Strong & DurableStrong & Durable

Does not Rust orDoes not Rust or Rot. In fact, strengthRot. In fact, strength

increases with time.increases with time.

Does Not Need a CoatingDoes Not Need a Coating

Excellent Resistance toExcellent Resistance to FireFire


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Types of concreteTypes of concrete

Based on unit weight:1) Normal-weight concrete (2400kg/Cum)

2) Light-weight concrete (< 1800 kg/Cum)

3) Heavy-weight concrete (>3200 kg/Cum)

Based on Strength: (As per IS:456-2000)

1) Ordinary concrete: (10-20 MPa)

2) Standard concrete (25 to 55 MPa)3) High Strength concrete (60-80 MPa)


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Constituents of Concrete

CEMENT

FINE AGGREGATES

COARSE AGGREGATES WATER

ADMIXTURES

MINERAL

CHEMICAL


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CEMENT


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a. 33 Grade ordinary Portland cement conforming to IS 269

b. 43 Grade ordinary Portland cement conforming to IS 8112

c. 53 Grade ordinary Portland cement conforming to IS 12269

d. Rapid hardening Portland cement conforming to IS 8041

e. Portland slag cement conforming to IS 455

f. Portland pozzolana cement (fly ash based) conforming to IS 1489 (Part 1)

g. Portland pozzolana cement (calcined clay based) conforming to IS 1489 (Part 2)

h. Hydrophobic cement conforming to IS 8043

i. Low heat Portland cement conforming to IS 12600

j. Sulphate resisting Portland cement conforming to IS 12330

Types of Cement recommended by IS 456


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High Early Strength Cement

OPC OPC

Low Heat of Hydration Cement


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a. 72 1 hour not less than 23 MPa

b. 168 2 hour not less than 33 MPa

c. 672 4 hour not less than 43 MPa

43 Grade Ordinary Portland Cement Compressive strength IS 8112

53 Grade Ordinary Portland Cement Compressive strength - IS 12269

a. 72 1 hour not less than 27 MPa

b. 168 2 hour not less than 37 MPa

c. 672 4 hour not less than 53 MPa


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FINE AGGREGATE (SAND)


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SIEVE ANALYSIS OF FINE AGGREGATES AS PER IS 383


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BULKAGE OF SAND


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CRUSHED ROCK FINES

A BYPRODUCT OF CA CRUSHING UNITS.

NEEDS TO BE WASHED WITH WATER/AIR AS ITCONTAINS EXCESSIVE FINES.

AS IT CONTAINS FLAKY MATERIAL, SHOULD BE USEDWITH CAUTION.

MUST SATISFY THE GRADATION REQUIREMENTS OFIS:383.

BETTER TO GO FOR MANUFACTURED SAND, MADE BY

VERTICAL SHAFT IMPACTORS. (BARMAC B SERIES VSICRUSHER).

MANUFACTURED SAND CONTAINS CUBIC SHAPEDPARTICLES AND HENCE HAVE LESSER VOID CONTENT.


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COARSE AGGREGATES


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SIEVE ANALYSIS OF COARSE AGGREGATES AS PER IS 383


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Effect of Aggregate SizeEffect of Aggregate Size


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Tests on aggregates and Acceptable limits IS 383

Other than for wearing

surfaces

For wearing surfaces

Aggregate Crushing Value Shall not exceed 45% Shall not exceed 30%

Aggregates Impact Value Shall not exceed 45% Shall not exceed 30%

Aggregate Abrasion Value Shall not exceed 50% Shall not exceed 30%


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WATER


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Permissible Limits of Deleterious materials in water as per IS 456


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FLY ASH

MINERAL ADMIXTURES

GGBS


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Mineral Admixtures recommended by IS 456

1. Pozzolanasa. Fly ash (pulverized fuel ash)

b. Calcined clay based

2. Silica fume

3. Ground Granulated Blast Furnace Slag

4. Rice husk ash

5. Metakaoline


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EFFECT OF FLYASH ON REDUCTION OF Ca(OH)2


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EFFECT OF FLYASH ON HEAT RELEASE


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EFFECT OF FLYASH ON STRENGTH (IN 28 DAYS)


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EFECT OF FLYASH ON STRENGTH (IN ONE YEAR)


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EFECT OF GGBS ON STRENGTH


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CHEMICAL ADMIXTURES


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CHEMICAL ADMIXTURES

WATER REDUCERS (HRWRA) / SUPERPLASTICISERS

RETARDERS

VISCOSITY MODIFIERS (VMA) WATER PROOFING CHEMICALS

ACCELERATORS

AIR ENTRAINING AGENTS

CORROSION INHIBITORS

COLOURING PIGMENTS


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CONCRETE


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Grades of Concrete as per IS 456


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WORKABILITY OF CONCRETE


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DEGREE OFWORKABILITY OF CONCRETE AS PER IS 456


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COMPACTING FACTOR APPARATUS IS 1199


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FLOW TABLE APPARATUS IS 1199


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MOULD FOR FLOW TEST IS 1199


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Minimum Cement Content,MaximumWater-Cement Ratio andMinimum Grade of

Concrete for Different Exposures with NormalWeight Aggregates of 20 mm Nominal

Maximum Size IS 456


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Environmental exposure conditions as per IS 456


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Frequency of sampling as per IS 456


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INITIAL & FINAL SETTING OF CONCRETE


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Concrete CuringConcrete Curing

Must be keptMoistMust be keptMoist

Moisture Needed for:Moisture Needed for:

HydrationHydration

(Development of Strength)(Development of Strength)


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READY MIXED CONCRETE


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Materials testing requirements Aggregates IS 4926

Minimum test frequencies

-Continued-


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Materials testing requirements Aggregates IS 4926 (Contd)


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Sampling of ReadyMixed Concrete IS 4926

1) Allow the truck-mixer to remix the concrete at site.

2) Allow at least the first one-third of a CuM of

concrete to be discharged.

3) Take at least 4 incremental samples from theremainder of the load.

4) Avoid sampling the last CuM of concrete.

5) Thoroughly re-mix this composite sample either on

a mixing tray or in the sampling bucket.6) Proceed with the required testing.


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DELIVERY TICKET INFORMATION - IS 4926

a. Name or number of the ready-mixed concrete depot.

b. Serial number of the ticket.

c. Date.

d. Truck number.e. Name of the Purchaser.

f. Name and location of site.

g. Grade or mix description of the concrete.

h. Specified target workability.

i. Minimum cement content (if specified).j. Type of cement and grade (if specified).

k. Maximum free water-cement ratio (if specified).

l. Nominal maximum size of aggregate.

G-1 The following information shall be included in the delivery ticket to

accompany the load to the purchaser:


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m. Generic type or name of any chemical and mineral admixtures included.

n. Quantity of concrete in M3

o. Time of loading.

p. Signature of the plant operator.

q. A statement warning the purchaser of the precautions needed to be taken

when working with cement and wet concrete.

G-2. On site, the following information will be added.

a. Time of arrival on site.

b. Time when discharge was completed.

c. Any water/admixture added by the supplier to meet the specified

workability.

d. Any extra water/admixture added at the request of the purchaser of the

concrete, or his representative, and his signature.

e. Pouring location.

f. Signature of the purchaser or his representative confirming discharge of

the load.

DELIVERY TICKET INFORMATION - IS 4926 (Contd)


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Sample collected

Slump Measured

Cone Removed and Concrete

Allowed to Slump

Slump Cone Filled


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REASONS FOR SLUM

P LOSS


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CONCRETEMIX DESIGN

(Ref: IS: 10262)

Objective :To determine the proportion of ingredients that

would produce a workable concrete mix that is

durable, and ofrequired strength,

and at a minimum cost.

Principles ofMix Design- Workable mix

- Use as little cement as possible

- Use as little water as possible

- Gravel and sand to be proportioned to achieve a dense mix- Maximum size of aggregates should be as large as possible, tominimize surface area of aggregates


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CONCRETEMIX DESIGN (Contd)

Methods ofMix Design

- Volumetric method (arbitrary)

- Proportioning from field data method

- Proportioning by trial mixtures method

- Mass proportioning method- Absolute volume method (BIS approved method)

BIS Design based on Absolute Volume

1. Calculate target concrete strength as per the degree of quality control at site.

2. Find the w/c ratio for the target strength as per the grade of cement used.3. Check this w/c ratio w.r.t exposure condition.

4. Select the maximum size of coarse aggregates


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ConcreteMix Design (cont.)

5. Find maximum water content in Kgs for the given size of CA.6. Calculate Cement content from w/c ratio and step 5.

7. Check this cement with the minimum cement requirement for the given

exposure condition.

8. Find quantity of FA as % of total aggregates for the given size of CA.

9. Select the Compaction factor as per the task.10. Find NMC and air content of the aggregates.

11. Apply corrections to water content for NMC of FA & CA.

12. Apply corrections to FA content for change in Compacting factor.

13. Calculate the weights of CA and FA.

14. Find the weights of field mix (containing moisture) per unit volume.15. Compute the field mix proportions.

16. Cast Cubes and test them to confirm they give target strength.


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ACCEPTANCE CRITERIA

AS PER IS-456 :2000

Specified

Grade

Average strength

of 3 specimens

(N/sq.mm)

Individual test

results

(N/sq.mm)

M20 ormoreu

fck + 4N/sq.mm

u

fck - 4N/sq.mm

Note:

If std. deviation is established at work site,

the av. str. should be u fck + 0.825 Sd

******


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KEEP INMIND

THANK YOU


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THANK YOU

Prakash Lecture 28-1-10

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