Concrete Technology Mix Design
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Questions and Answers

What is the range of concrete density in kg/cum?

  • 2400 to 2500 (correct)
  • 2600 to 2700
  • 2800 to 2900
  • 2200 to 2300

    • What is the volume of a slump cone in cubic meters?

  • 0.0055
  • 0.0077
  • 0.0066 (correct)
  • 0.0044

    • How is compressive strength tested for concrete as per IS 516?

  • Using a cylinder of 110 mm dia & 220 mm height
  • Using a 100 mm x 100 mm x 100 mm cube (correct)
  • Using a 150 mm x 150 mm x 150 mm cube (correct)
  • Using a 200 mm x 200 mm x 200 mm cube

    • What type of testing involves tasting a piece of mango?

    <p>Destructive testing</p> Signup and view all the answers

    Which of the following statements is true about concrete's strength?

    <p>Concrete is strong in compression</p> Signup and view all the answers

    What is the significance of the water/cement ratio (w/c) in concrete mix design?

    <p>It influences both strength and durability of the concrete.</p> Signup and view all the answers

    Using Abram's Law, what is the relationship between water/cement ratio and strength?

    <p>Lower w/c ratio leads to higher strength.</p> Signup and view all the answers

    What is the role of air content in concrete mix design for M50 grade concrete?

    <p>It increases workability and prevents segregation.</p> Signup and view all the answers

    What is the corrected volume of coarse aggregate (CA) per unit volume of total aggregate (TA) determined for a w/c ratio of 0.29?

    <p>0.682</p> Signup and view all the answers

    What is the final water content used in the concrete mix design for M50 grade concrete?

    <p>198.32 kg/cum</p> Signup and view all the answers

    What does it mean if the maximum cement content for a mix is capped at 450 kg/cum?

    <p>It prevents excessive shrinkage and cracking.</p> Signup and view all the answers

    When designing a concrete mix, if the target mean strength is calculated to be 58.25 MPa, what is the correct approach?

    <p>Use the highest calculated strength.</p> Signup and view all the answers

    What is the significance of specific gravity in the context of coarse aggregate and fine aggregate in concrete mix design?

    <p>It helps in calculating the volume of aggregates.</p> Signup and view all the answers

    How is the volume of total aggregate calculated in the context of the Absolute Volume Method?

    <p>By accounting for air content and volumes of all components.</p> Signup and view all the answers

    For a concrete mix that requires a 150 mm slump, what adjustment is made to the water content?

    <p>It is increased by 12% of the calculated amount.</p> Signup and view all the answers

    What does the 'C:FA:CA:w/c' ratio of 1:2.3:3.1:0.4 represent in concrete mix design?

    <p>Proportions of Cement, Fly Ash, Coarse Aggregate, and Water-Cement ratio</p> Signup and view all the answers

    Which factor does NOT influence the strength of concrete?

    <p>Temperature during mixing</p> Signup and view all the answers

    What is the characteristic strength of concrete according to IS 456-2000?

    <p>It represents the strength of the concrete that tests at 28 days.</p> Signup and view all the answers

    Which component is essential for hydration in concrete?

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

    What is the significance of compaction in concrete mix design?

    <p>It helps eliminate air voids and increases strength.</p> Signup and view all the answers

    Which mineral admixture is commonly used to enhance durability in concrete?

    <p>Fly Ash</p> Signup and view all the answers

    What is the role of curing in concrete technology?

    <p>It prevents premature drying and maintains moisture for hydration.</p> Signup and view all the answers

    What is the correct approach to testing concrete strength?

    <p>Average the results of all test samples to determine strength.</p> Signup and view all the answers

    What is the formula for compressive strength?

    <p>P/A</p> Signup and view all the answers

    What characteristic size of a specimen is specified as per IS 516 for tensile strength testing?

    <p>100 mm x 100 mm x 500 mm</p> Signup and view all the answers

    What is the equation for bending stress in concrete?

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

    When should the results of a tensile strength test be discarded based on the position of crack occurrence?

    <p>When a is less than 170 mm for 150 mm specimens</p> Signup and view all the answers

    What is the split tensile strength formula for a cylinder with a diameter of 150 mm and a height of 300 mm?

    <p>$\frac{2P}{\pi D L}$</p> Signup and view all the answers

    What is represented by the symbol 'E' in the equation related to bending?

    <p>Modulus of Elasticity</p> Signup and view all the answers

    What does 'Z' represent in the bending stress equation?

    <p>Plastic Section Modulus</p> Signup and view all the answers

    What procedure must be followed to determine the modulus of elasticity in concrete?

    <p>Seasoning the specimen with zero extensometer reading</p> Signup and view all the answers

    What is the relationship between moment (M), load (P), and the distance (L) in the equation for bending stress?

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

    Which of the following formulas correctly defines the moment of inertia (I) for a rectangular section?

    <p>I = BD^3/12</p> Signup and view all the answers

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

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

    How much water is actually required to be added to the mix after accounting for water absorption?

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

    What is the total mass of materials required after correction for a standard mix?

    <p>2533.84 kg/cum</p> Signup and view all the answers

    If the volume of the beam is increased by 20%, what is the final volume to be used for calculations?

    <p>1.8 cum</p> Signup and view all the answers

    What is the mass of fine aggregate after the adjustment for water absorption?

    <p>581.78 kg/cum</p> Signup and view all the answers

    When conducting a slump test, what is the ratio of the components used?

    <p>1:1.293:3.024:0.31</p> Signup and view all the answers

    How many bags of cement are required for a beam with a final mass of 810 kg?

    <p>16.2 bags</p> Signup and view all the answers

    Which of the following represents the correct density adjustment for the coarse aggregate in the mix?

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

    To increase the beam's volume for safety, what percentage increment is typically added?

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

    Study Notes

    Factors Influencing Strength of Concrete

    • Cement: Type and dosage affect the strength.
    • Aggregate: Type, dosage, grading, shape, surface texture, strength, and saturated surface dry (SSD) condition impact performance.
    • Mineral Admixtures: Examples include fly ash, GGBFS, rice husk ash (RHA), silica fume (SF), and metakaolin (MK).
    • Water: Essential for hydration, workability, compactability, strength, density, impermeability, and durability.
    • Proportioning: Ratios such as Cement: Fine Aggregate: Coarse Aggregate: Water/Cement (C:FA:CA:w/c) significantly influence mixture performance.
    • Compaction: Types include manual and mechanical.
    • Finishing: Methods can be either manual or mechanical.
    • Curing: Depends on temperature, relative humidity, and other conditions.
    • Testing Age: Strength is typically evaluated at 28 days.
    • Statistical Parameters: Strength is assessed using average values and standard deviation.

    Characteristic Strength

    • Defined as the strength below which no more than 5% of test results are expected to fall, based on IS 456-2000.
    • Characteristic compressive strength is tested on a standard cube (150 mm x 150 mm x 150 mm) after 28 days of curing.

    Selection of Concrete Mix Proportioning

    • Identify target mean strength using formulas.
    • Determine Water/Cement ratio based on strength (Abram’s Law) and durability.
    • Choose lesser of the two w/c ratios.
    • Select water and admixture content based on standards.
    • Calculate cement content using w/c ratio and water content.
    • Ensure cement content meets minimum and maximum standards.
    • Determine the volume of coarse aggregate per total aggregate volume.
    • Adjust and finalize mix calculations using the Absolute Volume Method.

    Concrete Mix Design for M50 Grade

    • Uses 43 Grade Ordinary Portland Cement (OPC) per IS 269-2015.
    • Slump requirement of 150 mm, moderate exposure conditions.
    • Specific gravities: Cement - 3.12, Coarse Aggregate (CA) - 2.8, Fine Aggregate (FA) - 2.58.
    • Water absorption: CA - 0.4%, FA - 0.9%.
    • Well-graded coarse aggregate as per IS 383.

    Target Mean Strength Calculation

    • Formula: Target Mean Strength = fck + 1.65(S) for statistical reliability.
    • Example: For fck = 50 and S = 5, target mean strength calculated as 58.25 MPa.

    Mix Calculations

    • Final water content adjustment accounts for aggregate absorption.
    • Adjustments made for changes in w/c ratio with respect to aggregate size and slump variations.

    Absolute Volume Method

    • Total volume = 1 cubic meter, with 1% entrapped air accounted.
    • Cement volume is determined through specific gravity calculations.
    • Coarse and fine aggregates volumes calculated based on mix proportions.

    Mix Proportions Before and After Correction

    • Initial mix proportions calculated, followed by corrections for aggregate absorption.
    • Adjusted water content based on absorbed water by aggregates is crucial for achieving desired consistency.

    Quantities for Casting a Beam

    • Beam dimensions and volume are calculated and increased by 20% for safety.
    • Quantities of cement, fine aggregate (FA), coarse aggregate (CA), and water are specified for casting the beam.

    Slump Test Requirements

    • Specification of mix ratios for slump tests; understanding unit weight and volumes involved in testing cement consistency.

    Testing Hardened Concrete

    • Adherence to IS 516 standards for both destructive and non-destructive testing methods to evaluate concrete strength and quality.
    • Tests include compressive strength (150 mm cubes), tensile strength via split tests, and modulus of rupture.

    Flexural and Split Tensile Strength

    • Bending theories and calculations of flexural strength are derived from load conditions.
    • Split tensile strength test parameters specified for cylindrical specimens.

    Young’s Modulus of Concrete

    • Explanations related to the compressometer and static load testing for modulus determination as per IS standards.

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    Concrete Mix Designing PDF

    Description

    This quiz covers the essential aspects of concrete mix design, focusing on the selection and proportioning of concrete mixtures. It delves into factors influencing the strength of concrete, including the types and dosages of cement, aggregate properties, and the role of mineral admixtures. Perfect for students studying concrete technology.

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