Construction Techniques and Materials
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Questions and Answers

What is the primary advantage of using Tremie pipes in construction?

  • To prevent concrete contamination (correct)
  • To reduce the cost of concrete
  • To increase the speed of pouring concrete
  • To enhance the concrete's strength

    • Which formwork can typically be removed first in a construction project?

  • Beam Formwork
  • Foundation Formwork
  • Slab Formwork
  • Wall and Column Formwork (correct)

    • What is the role of a superplasticizer in concrete?

  • To enhance the concrete's thermal resistance
  • To improve workability and make it pumpable (correct)
  • To make concrete set faster
  • To reduce the drying time of concrete

    • Which type of joint is most effective for improving water tightness in precast structures?

    <p>Wet Joint</p> Signup and view all the answers

    What type of construction pump is suitable for dewatering operations?

    <p>Submerged Pump</p> Signup and view all the answers

    What is the critical temperature at which a building's structure loses half its strength?

    <p>600°C</p> Signup and view all the answers

    For a super tall building, which formwork system is preferred to speed up slab construction?

    <p>Fly Form/Table Form</p> Signup and view all the answers

    Which construction equipment is regarded as being quieter during operation?

    <p>Hydraulic Vibrator Machine</p> Signup and view all the answers

    What is one advantage of using precast concrete in terms of operational efficiency?

    <p>Production is less impacted by weather conditions.</p> Signup and view all the answers

    Which factor contributes to the environmental benefits of precast concrete?

    <p>Reduction in noise and air pollution.</p> Signup and view all the answers

    How does the use of prestressed concrete help in construction?

    <p>It fully utilizes the strength of both concrete and steel rebar.</p> Signup and view all the answers

    Why is a waterproofing layer recommended in precast toilets?

    <p>To lower the risk of water leakage.</p> Signup and view all the answers

    What is a result of reducing the number of separate operations in construction?

    <p>Enhanced management under a single entity.</p> Signup and view all the answers

    What operational challenge is directly addressed by the factory setting of precast concrete?

    <p>Delays caused by adverse weather conditions.</p> Signup and view all the answers

    What safety advantage does precast production offer over traditional construction methods?

    <p>Minimized exposure of workers to hazardous weather.</p> Signup and view all the answers

    Which material is suitable for achieving water tightness in jointing applications?

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

    Which of the following describes a benefit of using a vibration table in concrete compaction?

    <p>It improves the density and strength of the concrete.</p> Signup and view all the answers

    What is the primary advantage of the unitised system in curtain wall construction?

    <p>It is the most effective and economical option</p> Signup and view all the answers

    Which option is a common test used to assess the performance of piles?

    <p>Sonic logging test</p> Signup and view all the answers

    What is the recommended method for basement depths exceeding 20 meters?

    <p>Diaphragm wall plus top-down method</p> Signup and view all the answers

    Which of the following is NOT considered a potential risk when constructing a basement?

    <p>Soil Stability Monitoring</p> Signup and view all the answers

    Which of these factors is an advantage of using precast concrete components?

    <p>Ensures consistent and higher quality due to controlled environments</p> Signup and view all the answers

    What makes the steel H pile a popular choice in Hong Kong for displacement piles?

    <p>Higher load capacity and adaptability</p> Signup and view all the answers

    Which of the following describes the effect of the top-down construction method?

    <p>It allows concurrent construction of the basement and superstructure</p> Signup and view all the answers

    What is the main purpose of the temporary steel casing during the installation of machine dug piles?

    <p>To prevent soil collapse during drilling</p> Signup and view all the answers

    Which of the following is NOT an important consideration for prefabrication on the site plan?

    <p>The preferred material colors for the prefab items</p> Signup and view all the answers

    What is the minimum depth of penetration for the bellout formed at the base of the pile?

    <p>300 mm</p> Signup and view all the answers

    In what scenario would a reversed circulation drill (RCD) be most appropriate?

    <p>When working with a rock stratum</p> Signup and view all the answers

    What method is employed to clean the borehole base before placing the reinforcement cage?

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

    Which factor must be considered when determining the area for storing prefabricated materials?

    <p>The anticipated construction speed</p> Signup and view all the answers

    What is the primary purpose of using spacers with the reinforcement cage during pile installation?

    <p>To maintain adequate concrete cover</p> Signup and view all the answers

    What sequence follows the insertion of the temporary steel casing in pile installation?

    <p>Boring the hole using a rotary auger</p> Signup and view all the answers

    What is the role of the beam and slab system in this construction method?

    <p>To provide lateral support to the diaphragm wall.</p> Signup and view all the answers

    Which step directly follows the backfilling of bored holes with soil?

    <p>Exposing the upper portion of stanchions.</p> Signup and view all the answers

    What is the purpose of the temporary openings made in the slabs?

    <p>To provide access for excavating machinery.</p> Signup and view all the answers

    At what stage of the construction process is soil removal facilitated by ramps?

    <p>While excavating for the first level of the basement.</p> Signup and view all the answers

    What is the first step in the construction procedures for the top-down method?

    <p>Constructing diaphragm walls.</p> Signup and view all the answers

    What is the primary purpose of the tremie pipe during the concreting process?

    <p>To allow concrete to flow without contamination</p> Signup and view all the answers

    Which operation is conducted after the concrete acquires adequate strength in piling?

    <p>Removing the excess contaminated concrete</p> Signup and view all the answers

    What role does bentonite slurry play during the excavation of diaphragm walls?

    <p>It provides hydrostatic pressure to support the soil</p> Signup and view all the answers

    How is the panel width of typically excavated trenches determined for stable soil?

    <p>Between 4 m to 6 m</p> Signup and view all the answers

    What is required at the end of each panel during diaphragm wall construction?

    <p>Vertical tubes to form a semicircular recess</p> Signup and view all the answers

    When is the tremie pipe tip required to be placed during the concreting process?

    <p>Around 2 to 3 metres below the surface</p> Signup and view all the answers

    What happens to the bentonite slurry once the concrete has hardened?

    <p>It is pumped to a de-sanding plant for reuse</p> Signup and view all the answers

    What is the function of the box-outs attached to the reinforcement cage in diaphragm wall constructions?

    <p>To form junctions of floors and walls</p> Signup and view all the answers

    Study Notes

    Pile Types

    • Two main pile types exist: displacement piles (Steel-H Piles) and replacement piles (Barrettes)

    Tremie Pipe Advantages

    • Prevents concrete contamination

    Formwork Removal Priority

    • Walls and columns can be removed first due to their structural independence from beams and slabs.

    Dewatering Pumps

    • Submerged pumps and suction pumps are used for dewatering

    Self-Compacting Concrete

    • Highly workable and pumpable

    Concrete Additives

    • Superplasticizer increases workability and flowability of concrete

    Slab Formwork

    • Fly form or table form is suitable for speeding up tall building slab construction

    Continuous Beam Steel

    • Top steel (cantilever) and bottom steel (span) are important reinforcing components

    Simply Supported Beam Steel

    • Bottom steel is the main reinforcing component for a single-span beam.

    Joint Problems in Precast Structures

    • Wet joint (Monolithic Joint) using in-situ concrete topping is superior to a dry joint for preventing water leakage, since it fills gaps and doesn't rely on unreliable gaskets or sealants.

    Construction Equipment Noise

    • Hydraulic vibrator machines are known for their quiet operation contrasted with other construction equipment.

    Design Considerations for Fire-Damaged Structures

    • Temperature of 600°C for steel and concrete structural failure

    Moving Wall Tiles

    • Material hoist machinery is specifically designed to move items (but not personnel).

    Concrete Joint Material

    • Epoxy is used for concrete spalling repair whereas silicone provides lasting water tightness.

    Formwork Cover Material

    • Plastic sheets are commonly used to cover formwork spaces.

    Curtain Wall Systems

    • The unised system is the most prevalent and efficient curtain wall system.
    • Steel H pile is the most popular displacement pile in Hong Kong (HK).

    Bored Pile Installation

    • The process of bored pile installation involves a temporary steel casing, a hydraulic oscillator, chisel, reinforced cage, and tremie pipe.

    Common Pile Tests

    • Pile tests may include dynamic load tests, static load tests, sonic load tests, sonic logging tests, standard penetration tests, core drilling, vibration tests, lateral load tests, and tension tests.

    Top-Down Construction Advantages

    • Reduced construction time, simultaneous basement & superstructure construction, and enhanced weather protection.

    Deep Basement Construction Methods

    • Diaphragm wall plus top-down method for depths exceeding 20 meters; Steel sheet piling and cofferdams (bottom-up method) for shallower basements (10-20 meter).

    Basement Risk Factors

    • Soil collapse, worker safety, disruption of utilities, differential settlement affecting neighboring structures/MTR, and ground water/flooding

    Precast Concrete Advantages

    • Skilled labor demand reduced in favor of semi-skilled labor on site for precast elements installation, lower labor costs, reliable quality control (factory QC), consistent quality (indoor shielded from weather and rain environments), use of robots and machinery, vibration tables for improved compaction, controlled curing chambers for temperature, humidity, and pressure control, time efficient process in the construction workflow.

    Precast Construction Site Considerations

    • Ensuring tower crane capacity in relation to working radius to safely handle prefabricated materials.
    • Choosing appropriate storage area for prefabricated materials based on construction rate and material delivery timing.
    • Planning internal access pathways for prefabricated material delivery vehicles.

    Machine Dug Piles Installation

    • Precise site location determination, initial hole boring using rotary auger, positioning and protection using temporary steel casing, continuous boring until required depth, forming a bell-out, cleaning the borehole, embedding reinforcement cage, pouring concrete with tremie pipes ensuring no spillage, removing casing, excavating to the concrete cut-off level, removing contaminated concrete, and finally casting pile cap.

    Diaphragm Wall Installation

    • Creating guide walls for trenching machinery, using hydrofraise or hydro-mill cutters, utilizing bentonite slurry support, recirculating bentonite, placing stop-ends, building the semicircular wall recess to ensure watertight connections, and removing excess soil

    Top-Down Construction Method

    • Forming bored holes, establishing steel stanchions, creating a ground floor slab, and subsequently excavating the basement and constructing the structure iteratively, progressively working upwards.

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    Description

    This quiz covers essential construction techniques and materials used in modern building projects. Topics include pile types, self-compacting concrete, formwork removal, and reinforcement in beams. Test your knowledge on the fundamental concepts that enhance construction efficiency and safety.

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