Concrete Mix Design and Strength Evaluation
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Questions and Answers

What is the recommended characteristic strength for a concrete mix designated as M30?

  • 25 MPa
  • 35 MPa
  • 20 MPa
  • 30 MPa (correct)

    • Which factor does NOT influence the strength of concrete?

  • Type of Cement
  • Water to Cement Ratio
  • Ambient Temperature (correct)
  • Type of Aggregate

    • Which mineral admixture is NOT mentioned in the factors influencing concrete strength?

  • Silica Fume
  • Superplasticizer (correct)
  • Ground Granulated Blast-Furnace Slag (GGBFS)
  • Fly Ash

    • What is the significance of the age at testing mentioned for concrete design?

    <p>Strength is assessed at 28 days as standard.</p> Signup and view all the answers

    Which dosage ratio of Cement, Fine Aggregate (FA), Coarse Aggregate (CA), and water (w/c) is mentioned?

    <p>1:2.3:3.1:0.4</p> Signup and view all the answers

    What is the term used to refer to the average value and standard deviation of concrete strength?

    <p>Statistical Parameter</p> Signup and view all the answers

    Which type of compaction methods are mentioned in the factors influencing concrete strength?

    <p>Manual and Mechanical</p> Signup and view all the answers

    Which of the following is NOT a method of curing mentioned to influence the strength of concrete?

    <p>Air Drying</p> Signup and view all the answers

    What is the purpose of using fibre reinforced high strength concrete in zones of high seismicity?

    <p>To improve flexibility and ductility</p> Signup and view all the answers

    What is the characteristic shape of the core sample used for testing compressive strength?

    <p>Cylindrical</p> Signup and view all the answers

    What is the corrected cylindrical strength when the compressive strength for the core sample is 22 MPa?

    <p>20.9 MPa</p> Signup and view all the answers

    How is equivalent cube strength derived from corrected cylindrical strength?

    <p>By multiplying corrected strength by 5/4</p> Signup and view all the answers

    What does a lower ultrasonic pulse velocity indicate about the quality of concrete?

    <p>Presence of voids or cracks</p> Signup and view all the answers

    Why are calibration curves specific to a type of aggregate and cement?

    <p>They are not universally valid due to material differences</p> Signup and view all the answers

    What does a higher velocity in ultrasonic pulse testing signify?

    <p>Better concrete quality in terms of density</p> Signup and view all the answers

    What is the typical height-to-diameter (H/D) ratio for core samples mentioned?

    <p>1.6</p> Signup and view all the answers

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

    <p>1360.87 kg/cum</p> Signup and view all the answers

    How much actual water needs to be added to the concrete mix after corrections?

    <p>141.19 kg/cum</p> Signup and view all the answers

    What is the mix proportion ratio for fine aggregate after correction?

    <p>1.293</p> Signup and view all the answers

    What increase factor is used to estimate the volume required for casting the beam?

    <p>20%</p> Signup and view all the answers

    What is the total weight of cement required to cast the beam?

    <p>810 kg</p> Signup and view all the answers

    What is the specific gravity of fine aggregate used in the calculations?

    <p>1.304</p> Signup and view all the answers

    Which component has the highest mass in the mix proportions after correction?

    <p>Coarse Aggregate</p> Signup and view all the answers

    What is the volume of a beam with dimensions 500 x 600 x 5000 mm in cubic meters?

    <p>1.5 cum</p> Signup and view all the answers

    What is the water absorption percentage for coarse aggregate as stated?

    <p>0.4%</p> Signup and view all the answers

    What is the proportion of water to cement in the corrected mix?

    <p>0.31</p> Signup and view all the answers

    What process is followed to ensure concrete density in the testing described?

    <p>Maintaining stress for a minute and reducing it to a fixed point.</p> Signup and view all the answers

    During the second loading cycle, what stress level should be maintained before reduction?

    <p>C + 1.5 kg/cm2</p> Signup and view all the answers

    What characteristic of High Strength Concrete (HSC) impacts its use in multi-storeyed buildings?

    <p>HSC allows for smaller column sizes.</p> Signup and view all the answers

    What major drawback does High Strength Concrete (HSC) have in seismic situations?

    <p>HSC has limited ductility.</p> Signup and view all the answers

    When is concrete assumed to be fully dense according to the loading procedure?

    <p>When the current reading matches the previous reading.</p> Signup and view all the answers

    What type of stress-strain relationship is described as linear-elastic?

    <p>There is a direct proportion between stress and strain during loading and unloading.</p> Signup and view all the answers

    What is the typical strength characteristic of Normal Strength Concrete (NSC)?

    <p>Lower than High Strength Concrete (HSC).</p> Signup and view all the answers

    In terms of ductility for multi-storeyed buildings, which concrete option is preferred?

    <p>NSC is preferred for its adequate ductility.</p> Signup and view all the answers

    What is the formula for calculating compressive strength?

    <p>$\frac{P}{A}$</p> Signup and view all the answers

    What dimensions are specified for the split tensile strength cylinder?

    <p>150 mm diameter &amp; 300 mm height</p> Signup and view all the answers

    Which method is NOT mentioned as an indirect method for measuring tensile strength?

    <p>Direct tensile test</p> Signup and view all the answers

    In the context of flexural strength, which equation represents the bending stress?

    <p>$f = \frac{M y}{I}$</p> Signup and view all the answers

    What is the recommended size of the specimen used for testing according to IS 516?

    <p>Both A and C</p> Signup and view all the answers

    At what distance from the support should the crack occur for the results to be considered valid?

    <p>Less than 170 mm for 150 mm specimens</p> Signup and view all the answers

    What is the value of Young's modulus for concrete according to IS 516-1959?

    <p>Dependent on specimen seasoning</p> Signup and view all the answers

    In the formula for split tensile strength, what does the variable 'L' represent?

    <p>Length of the cylinder</p> Signup and view all the answers

    How is the flexural strength of a concrete specimen calculated?

    <p>$f = \frac{PL}{6I}$</p> Signup and view all the answers

    Study Notes

    Concrete Mix Design

    • Concrete strength heavily depends on cement type, cement dosage, aggregate type, and aggregate dosage.
    • Water is vital for hydration and affects workability, compactability, strength, density, impermeability, and durability.
    • Proper proportioning of cement, fine aggregate, coarse aggregate, and water is crucial for achieving desired strength.
    • Compaction and finishing play key roles in concrete quality.
    • Curing is vital for concrete strength development and should be controlled for temperature and humidity.
    • Concrete strength is evaluated at 28 days.
    • Concrete strength is a statistical parameter with an average value and standard deviation.

    Sustainability and Durability

    • Durability is a critical aspect of sustainability.

    Characteristic Strength

    • The characteristic strength is the strength below which only 5% of test results should fall, as defined by IS 456-2000.
    • The standard testing method is compression testing of 150mm x 150mm x 150mm cubes at 28 days under normal curing.
    • M30 refers to concrete with a characteristic compressive strength of 30 MPa.

    Selection of Concrete Mix Proportioning

    • The first step in selecting a mix is determining the target mean strength.
    • For areas prone to high seismicity, fiber-reinforced high-strength concrete might be preferred.

    Testing Methods

    • Core samples are used for non-destructive testing of finished structures like bridges and roads.
    • Corrected cylinder strength is calculated using a correction factor and converted to equivalent cube strength.
    • Ultrasonic Pulse Velocity (UPV) is a non-destructive test that measures concrete quality, homogeneity, and density.
    • A higher velocity indicates good quality concrete.
    • A lower velocity suggests voids, low density, or potential cracks.
    • Calibration curves are required to relate velocity to strength for a specific aggregate and cement type.

    Mix Proportioning Example

    • In a mix design example, the water absorption of aggregates is accounted for to calculate the actual water content.
    • Trial mixes are cast and tested before final concreting to ensure the desired strength and quality.

    Required Quantities

    • Example calculations show how to determine the quantity of materials required for a specific volume of concrete.
    • For a 1.5 cubic meter beam, the required quantities of cement, fine aggregate, coarse aggregate, and water are calculated.

    Slump Test

    • The slump test measures the workability of the concrete mixture.

    Tensile Strength

    • Tensile strength is determined indirectly using two methods:
      • Split tensile strength test
      • Modulus of rupture test

    Compressive Strength

    • Compressive strength is calculated by dividing the load applied to the concrete specimen by its cross-sectional area.

    Flexural Strength & Modulus of Rupture

    • Flexural strength refers to the concrete's ability to resist bending forces.
    • Modulus of rupture is a measure of flexural strength.
    • The mathematical relationship between bending moment, stress, and section properties is used in the analysis.

    Split Tensile Strength

    • The split tensile strength is determined by measuring the load required to split a cylindrical concrete specimen.

    Young's Modulus of Concrete

    • Young's modulus (E) determines the stiffness of concrete and can be determined using a compressometer.

    Seasoning to Determine Modulus of Elasticity

    • Concrete specimens are seasoned to determine modulus of elasticity according to IS 516-1959.
    • The process involves applying controlled loads and measuring the strain to ensure the concrete is fully dense and its internal voids are minimized.

    Stress-Strain Relationship

    • The stress-strain relationship describes how concrete behaves under loading.
    • It can be linear or non-linear, and elastic or non-elastic, depending on the characteristics of the concrete.

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    Concrete Mix Designing PDF

    Description

    This quiz focuses on the essential aspects of concrete mix design, including the important factors that influence concrete strength such as cement type, aggregate type, and water. It also covers the significance of proper curing and compaction for achieving durability and sustainability in concrete structures. Test your knowledge on the principles of concrete mixing and strength evaluation.

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