High Performance Concrete Overview
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High Performance Concrete Overview

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Questions and Answers

What is the primary characteristic of pervious concrete?

  • Low water-cement ratio
  • Smooth surface finish
  • High porosity (correct)
  • High compressive strength

    • Which of the following applications is most suitable for high performance concrete?

  • Residential patio construction
  • Oil drilling platforms (correct)
  • Parking areas with light traffic
  • Sidewalk installation

    • What is a key feature of stamped concrete?

  • It is devoid of any texture
  • It has low durability
  • It is patterned to resemble natural materials (correct)
  • It requires high water-cement ratio

    • What effect does a low water-cement ratio have on concrete?

    <p>Reduces permeability</p> Signup and view all the answers

    Which characteristic is NOT associated with high performance concrete?

    <p>High dissolution rate</p> Signup and view all the answers

    What is a common issue that can arise from poor segregation in concrete?

    <p>Honeycombing effects</p> Signup and view all the answers

    What role do super-plasticizers play in concrete mixtures?

    <p>Enhance workability without increasing water content</p> Signup and view all the answers

    Which of the following is an effect of bleeding in concrete?

    <p>Reduction in the strength of the surface layer</p> Signup and view all the answers

    What does segregation in concrete refer to?

    <p>The separation of cement paste from aggregates during handling</p> Signup and view all the answers

    Which of the following factors does NOT affect the workability of concrete?

    <p>Environmental temperature</p> Signup and view all the answers

    How does the increase in fineness of cement affect the water requirement for workability?

    <p>More water is required for the same workability</p> Signup and view all the answers

    What is the impact of using more cement in the concrete mix?

    <p>Improves the workability by providing lubrication</p> Signup and view all the answers

    What effect does the increase in the proportion of coarse aggregates have on workability?

    <p>Increases workability</p> Signup and view all the answers

    How does the grading of aggregates affect the workability of concrete?

    <p>Increasing the fineness modulus requires decreasing coarse aggregates</p> Signup and view all the answers

    Which type of admixture improves workability without increasing the water/cement ratio?

    <p>Water-reducing admixtures</p> Signup and view all the answers

    Bleeding in concrete typically results in:

    <p>A surface layer of water on the concrete</p> Signup and view all the answers

    What is one negative consequence of over-vibrating high-workability concrete?

    <p>It causes segregation of the mix.</p> Signup and view all the answers

    Which method is primarily used to eliminate air pockets in concrete?

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

    What is one potential impact of honeycombing in concrete?

    <p>Decreased structural integrity.</p> Signup and view all the answers

    What effect does bleeding have on freshly poured concrete?

    <p>It decreases the final strength of the concrete.</p> Signup and view all the answers

    Which technique is NOT recommended for improving the curing process of concrete?

    <p>Allowing for rapid drying in the air.</p> Signup and view all the answers

    Which factor does NOT typically influence mix proportioning in concrete?

    <p>Color of the concrete.</p> Signup and view all the answers

    What role do admixtures play in concrete mixtures?

    <p>They can modify characteristics such as strength and setting time.</p> Signup and view all the answers

    Which type of vibrator is best suited for thin layers of concrete?

    <p>Surface vibrator</p> Signup and view all the answers

    Study Notes

    High Performance Concrete

    • Concrete made with a carefully designed mix, mixed, transported, placed, consolidated and cured properly
    • It can be used in structures requiring long service lives, such as oil drilling platforms, long-span bridges and parking structures
    • Delivers high performance with good curing and construction practices

    Characteristics of High Performance Concrete

    • High early strength
    • High strength
    • High modulus of elasticity
    • High abrasion resistance
    • High durability and long life in severe environments
    • Low permeability and diffusion
    • Resistance to chemical attack
    • High resistance to frost and deicer scaling damage
    • Toughness and impact resistance
    • Volume stability
    • Ease of placement
    • Compaction without segregation
    • Inhibition of bacterial and mold growth

    Stamped Concrete

    • Concrete is patterned or textured to resemble brick, slate, flagstone, stone, tile, wood
    • Common applications include patios, sidewalks, driveways, pool decks and interior flooring
    • Less expensive alternative to materials such as stone, slate or brick

    Factors Affecting Workability

    • Mix Proportion:
      • The ratio of fine and coarse aggregates in relation to cement quantity
      • More cement results in a richer concrete, facilitating mobility and flow of aggregates
      • A lower cement quantity makes less paste available for aggregates, hindering mobility
    • Size of Aggregates:
      • Workability decreases with an increase in the surface area of aggregates
      • As the maximum size of coarse aggregate is increased, the surface area is decreased, improving workability
    • Shape of Aggregates:
      • Rounder particles have a decreased surface area, leading to improved workability
    • Surface Texture of Aggregates:
      • Rough textured aggregates have a larger surface area compared to smooth textured aggregates of the same volume
      • Concrete with smooth surfaces is more workable than concrete with rough textured aggregates
    • Grading of Aggregates:
      • Increasing the fineness modulus of fine aggregates requires a decrease in the amount of coarse aggregate to maintain workability
      • Increasing coarse aggregate proportion generally benefits workability
    • Use of Admixtures:
      • Admixtures such as water-reducing admixtures, superplasticizers and air-entraining admixtures can improve workability
      • They enhance workability even when using a low water/cement ratio

    Segregation

    • The separation of cement paste and aggregates of concrete during handling and placement
    • High-workability mixes should not be over-vibrated, as this can cause segregation
    • Vibration can be used to mold concrete around embedment, such as reinforcement, and to eliminate air pockets

    Compacting

    • Vibrators:
      • Internal vibrators compact concrete through direct contact
      • Form vibrators are attached to the formwork and transfer vibrations to the concrete
      • Surface vibrators are placed on top of the concrete, suitable for thin concrete layers

    Finishing

    • Compacting or hand tamping may leave an uneven surface
    • Surfaces are finished smoothly or according to desired pattern using floats, trowels and screeds
    • Floating followed by steel troweling is used for a smooth, hard, dense surface
    • Embedding aggregate particles just beneath the surface removes imperfections, humps and voids, compacting the mortar for further finishing operations
    • A slip-resistant surface is achieved by brooming before concrete hardens, but only after it has hardened enough to retain the scoring impression

    Curing

    • Maintaining moisture and temperature to promote hydration and strength gain
    • Concrete should be cured in a suitable environment
    • Drying in air during the early stages of hardening generally reduces strength
    • Curing keeps the concrete saturated to prevent the loss of water from the water-filled capillaries
    • Hydration can only occur when the vapor pressure in the capillaries is sufficiently high

    Curing Methods

    • Maintain the presence of water in concrete
    • Seal the surface to prevent water from escaping
    • Apply heat and additional moisture
    • Consider the size and shape of the structure when choosing a method

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    Description

    This quiz explores the characteristics and applications of high performance concrete, including its unique properties that make it suitable for structures with long service lives. Additionally, it touches on stamped concrete and its aesthetic uses. Test your knowledge on concrete types and their benefits.

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