Concrete Technology Quiz: Seismic Zones & Materials

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Questions and Answers

What is the primary purpose of using fibre reinforced high strength concrete?

To enhance durability in areas with high seismic activity (correct)

To simplify the concrete mixing process

To increase strength in zones of low seismicity

To reduce the cost of construction

What is the H/D ratio of the core sample mentioned in the content?

1.5

1.0

2.0

1.6 (correct)

How is the equivalent cube strength calculated from the corrected cylindrical strength?

By multiplying the corrected strength by 1.25 (correct)

By dividing the corrected strength by 1.25

By subtracting 5 from the corrected strength

By adding 5 to the corrected strength

What indicates a higher ultrasonic pulse velocity in concrete?

High density and homogeneity Signup and view all the answers

What correction factor is used when converting cylindrical strength to equivalent cube strength?

1.25 Signup and view all the answers

What does a lower ultrasonic pulse velocity signify about the concrete?

It may contain more voids or less density Signup and view all the answers

Which of the following is true regarding calibration curves for ultrasonic testing?

They must be established for specific aggregate and cement types Signup and view all the answers

What is the target mean strength for the M50 grade concrete mix?

58.25 MPa Signup and view all the answers

What is the minimum water/cement ratio to be considered for durability purposes?

0.29 Signup and view all the answers

What is the effect of capping core samples before testing?

It ensures uniform load distribution during compression tests Signup and view all the answers

How much water content is finalized for the mix design?

198.32 kg/cum Signup and view all the answers

What is the maximum cement content allowed for the M50 concrete mix?

450 kg/cum Signup and view all the answers

What is the corrected volume of coarse aggregate per unit volume of total aggregate after modifications?

0.682 Signup and view all the answers

What is the specific gravity of coarse aggregate used in the mix design?

2.8 Signup and view all the answers

Which method is used for mix calculations in this design?

Absolute Volume Method Signup and view all the answers

What factor is used to adjust water content for the desired slump increase?

4 Signup and view all the answers

What is the volume of fine aggregate per unit volume of total aggregate calculated?

0.318 Signup and view all the answers

In what zone is the sand classified as per the specifications?

Zone III Signup and view all the answers

What is the weight of cement required per cubic meter if the density of concrete is considered as 2500 kg/cum?

444.3 kg/cum Signup and view all the answers

What is the purpose of Non Destructive Testing in construction?

To assess the condition of structures without causing damage Signup and view all the answers

Which method is described as Destructive Testing when evaluating human health?

Blood testing Signup and view all the answers

According to IS 516, what are the dimensions of the standard cube for testing Compressive Strength of concrete?

150 mm x 150 mm x 150 mm or 100 mm x 100 mm x 100 mm Signup and view all the answers

What is the approximate volume of a slump cone based on the given dimensions?

0.0066 cum Signup and view all the answers

What is the actual mass of fine aggregate after considering water absorption?

581.78 kg/cum Signup and view all the answers

How much total water is absorbed by coarse and fine aggregates combined?

10.69 kg/cum Signup and view all the answers

What is the corrected actual mass of coarse aggregate after accounting for water absorption?

1360.87 kg Signup and view all the answers

What is the total weight of materials required to cast a beam of volume 1.8 cum?

2533.84 kg Signup and view all the answers

What is the volume of concrete needed after increasing the initial beam volume by 20%?

1.8 cum Signup and view all the answers

What is the ratio of the mix proportion for conducting a slump test?

1:1.293:3.024:0.31 Signup and view all the answers

How much water is needed to be added to the concrete mix after adjustments for absorption?

141.19 kg/cum Signup and view all the answers

What is the specific gravity of coarse aggregate used in the mix proportion?

1.0 Signup and view all the answers

What is the weight of cement required for a volume of concrete of 1.8 cum?

810 kg Signup and view all the answers

What total weight of fine aggregate will be needed for the concrete mix at a ratio of 1:1.293:3.024:0.31?

1047.2 kg Signup and view all the answers

What should be done during the first cycle of testing concrete strength?

Load up to a stress of (C+1.5) kg/cm2 and maintain for 1 minute. Signup and view all the answers

What does it indicate when the extensometer reading remains unchanged during subsequent cycles?

Concrete has achieved full density. Signup and view all the answers

How does high-strength concrete (HSC) affect column size in multi-storeyed buildings?

Reduces the size of columns. Signup and view all the answers

What is a significant drawback of using HSC in multi-storeyed buildings during an earthquake?

HSC has limited ductility. Signup and view all the answers

What characteristic does normal-strength concrete (NSC) have compared to HSC?

NSC has larger column sizes. Signup and view all the answers

In the context of stress and strain, what does 'linear-elastic' refer to?

Same stress-strain curve during loading and unloading. Signup and view all the answers

Which type of concrete is preferred when ductility is critical for safety?

Normal-strength concrete (NSC). Signup and view all the answers

What equation correctly represents stress in terms of load and area?

Stress = P/A. Signup and view all the answers

Study Notes

Seismic Zones and Concrete Use

Use of Fibre Reinforced High Strength Concrete is recommended for areas with high seismic activity.

Core Sample Testing

Core samples for testing are taken from finished structures like roads and bridges.
Cylindrical core samples have varying height-to-diameter (H/D) ratios, commonly 1.6.
Compressive strength of a core sample (22 MPa) is corrected using a factor of 0.95 for actual strength (20.9 MPa).
Equivalent cube strength is derived from corrected cylindrical strength, calculated as 26.125 MPa.

Ultrasonic Pulse Velocity Test

Conducted as per IS 516 (Part 5/Sec 1) 2018.
Measures concrete quality through velocity, indicating homogeneity and density.
High velocity suggests good quality; low velocity indicates voids, lower density, or cracks.
Calibration curves must be specific to the aggregate and cement types used.

Concrete Mix Design Process

Determine the required water/cement ratio based on strength (Abram’s Law) and durability.
Selection involves ascertaining water and admixture content.
Cement content is calculated using water/cement ratio and total water content.
Adjustments are made for the volume of coarse aggregate (CA) per total aggregate (TA).
Mix calculations utilize the Absolute Volume Method for accuracy.

M50 Grade Concrete Mix Design

Material choices include 43 Grade Ordinary Portland Cement (IS 269-2015) and 20 mm maximum aggregate size.
Target mean strength is calculated as 58.25 MPa and derived using statistical factors from IS guidelines.
Required water/cement ratio established as 0.29 for strength and 0.5 for durability; lower value (0.29) is chosen.
Water content for a 150 mm slump is set at 198.32 kg/cum after adjustments.

Final Mix Composition

Cement content fixed at 450 kg/cum; adjusted for water content due to aggregate absorption.
Total aggregate volume calculated, with proportions for fine aggregate (FA) and coarse aggregate (CA) as 0.318 and 0.682 respectively.
Actual water to be added post calculations is found to be 141.19 kg/cum after accounting for absorption.

Beam Example for Quantities

Beam dimensions (500 x 600 x 5000 mm) yield a volume of 1.5 cum, increased to 1.8 cum for wastage.
Total material requirements from this volume include 810 kg cement, 1047.2 kg FA, and 2449.6 kg CA.

Slump Test for Fresh Concrete

Slump test determines workability using a concrete ratio of 1:1.293:3.024:0.31.
Unit weight of concrete estimated between 2400 to 2500 kg/cum for concrete mix calculations.

Testing of Hardened Concrete

Both destructive and non-destructive testing methods are outlined under IS norms.
Destructive tests involve evaluating compressive strength based on standard cube or cylinder sizes.
Strength testing entails cyclical loading and measurement of extensometer readings until internal voids are minimized.

Stress and Strain Concepts

Discusses linear stress proportional to strain, emphasizing linear-elastic and non-linear responses.
Normal concrete shows limited strength capacity; hence, high strength concrete (HSC) is preferred for structural applications.

Material Preferences for Construction

High Strength Concrete (HSC) is chosen for multi-storey buildings to reduce column size, but may compromise ductility.
Normal Strength Concrete (NSC) maintains adequate ductility despite larger column sizes, offering safety during seismic events.

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Description

Test your knowledge on the use of fibre reinforced high strength concrete in regions of high seismic activity. This quiz covers key concepts from the Concrete Technology course, focusing on mix design and testing methods. Enhance your understanding of structural integrity in earthquake-prone areas.