Material Exam 2 PDF

# Short Questions ## Pile Foundation - Two types of pile foundation: - Displacement Pile: Steel-H Pile - Replacement Pile: Barrettes ## Concrete - **What are the advantages of using Tremie pipes?** - To prevent concrete contamination. - **What kind of pump can be used in Dewatering?**...

# Short Questions ## Pile Foundation - Two types of pile foundation: - Displacement Pile: Steel-H Pile - Replacement Pile: Barrettes ## Concrete - **What are the advantages of using Tremie pipes?** - To prevent concrete contamination. - **What kind of pump can be used in Dewatering?** - Submerged Pump - Suction Pump - **What is self-compacting concrete?** - Highly workable and even pumpable. - **What materials are added into the concrete so that it could become self-compacting?** - Superplasticizer (pumpable and flowable). ## Formwork - **What are the advantages of using Tremie pipes?** - To prevent concrete contamination. - **Suppose we have three formworks [column, slab, and beams], which formwork could be removed first?** - Wall and Columns (because they can stand on their own) - The strength of beams and slab are too low (horizontal formwork). - **Suppose you got a super tall building; what kind of formwork could be applied for the slab construction that could speed up the construction?** - Fly Form/Table Form. ## Steel - **What are the main steels for the Continuous Beam?** - Top Steel (cantilever) and Bottom Steel (Span) - RC beam RC Column: Top Steel (Over Column) - Over several spans - **What are the main steels for the Simply Supported Beam?** - One span only, main steel will be bottom steel. ## Precast Concrete - **As there will be joint problems (water leakage problem) surrounding with precast, which join is better for improving water tightness by joining precast together?** - Wet Joint (1. Place in-situ concrete topping 2. Give you Monolithic Joint) is better to prevent water leakage because in-situ concrete will cover all the gaps, so we should not rely on gasket or sealing (coz it is totally unreliable). ## Construction Equipment - **Which construction equipment is more silent?** - Hydraulic Vibrator Machine. ## Temperature - **Suppose this room catches fire, and we check damage of the structure. What is the critical temperature of the structure that it will lose half of its strength?** - 600°C (whether the steel and concrete structure) ## Material Handling - **Suppose in a construction site, you want to move the wall tile of sinks from the ground elevation to the fifth floor. What construction machines or plant should you use to pick up this wall tiles?** - Material Hoist (pick up materials only; not for human). ## Sealing - **We got two kinds of materials, epoxy and silicone. Which one is suitable for water tightness jointing?** - Silicone (for water tightness joint) - Epoxy (for concrete spalling) (structural repair). ## Cover - **What materials should be used in the cover spaces?** - Plastic ## Curtain Wall - **There are three types of system in the curtain wall, which one is the most famous one?** - Unitised System, as it is more effective and economical. - Stick System - Semi-Unitised System ## Piles - **Which one is the most popular displacement pile in HK?** - Steel H Pile - **What is the machine for the bored pile installation?** - Temporary steel casing, Hydraulic oscillator, chisels, RCD with roller bit, Underway mark, installing the steel reinforcement cage, and Tremie pipe and hoper. ## Pile Tests - **What are common pile tests?** - Dynamic load test - Static load test - Sonic load test - Sonic logging test - Standard Penetration test - Core Drilling - Vibration test - Lateral Load test - Tension test ## Top-Down Method - **What are the advantages of the top-down method?** - Excavation takes up lots of time. - The top-down construction method can reduce the construction time for the project. - Basement and the superstructure can be constructed at the same time. - It is more advantageous in terms of weathertight working conditions (not affected by inclement weather). ## Deep Basement - **For the depth more than 20 meters (more than 4 levels), we should use [insert method].** - Diaphragm wall + top-down method. - **For the depth less than 10 to 20 meters (less than 3 levels), we should use [insert method].** - Steel Sheet Piling and Cofferdams (Bottom Up method) - Depending on the depth and levels of the basement. ## Risk - **What is the potential risk for building the basement?** - Soil Collapse - Worker's Safety - Disruption of underground utilities (settlement and services) - Neighboring buildings foundations settlement/structures/MTR - Ground Water / Flooding ## Advantages of Precast Concrete - **What are the advantages of precast concrete?** - **Demand on Skilled Labor:** - Semi-skilled labor is required on-site for installing precast elements. - Lower labor cost (wage gap: HK Vs. China) - Aging skilled labor force in HK. - **Reliable Quality Control:** - QC in factory is accurate and reliable. - Substandard quality is discarded before installation. - RFID tags embedded in building products (e.g. precast units) - **Consistent Higher Quality:** - Indoor working environment (shielded from heat and rain) - Use of robots/machinery (consistent workmanship) (e.g. troweling) - Vertical elements cast horizontally (e.g. façade) provide better compaction. - Vibration table (e.g. slab) - offers compaction. - Curing chamber - controlled environment (temperature, humidity, pressure), - Window frame cast BEFORE concreting to lower the risk of water leakage and - waterproofing layer applied to the floor slab in a precast toilet to lower the risk of water leakage. - **Reduce No. of Separate Operations:** - Some elements (e.g. façade, toilet) involve lots of trades/sub-contractors - Different companies involve in conflicts, for example, trades involved in a toilet: plastering, painting, waterproofing, stonework, joiners, suspended ceiling, plumbing/drainage, electricity, and gas. - Precast factory: under the same management for well-planned work. - **Better Continuity Of Operation:** - Production line is smooth due to operation, not affected by weather, and not affected by delays of a particular trade. - A guaranteed steady supply of precast components/elements (logistic). - **Faster Construction:** - There is no need to erect and strike formwork on-site. - There is no need to wait for the concrete to develop strength. - Progress is not affected by weather. - Labor shortage does not impact the project. - **Environmentally Friendly:** - Factory production Vs. Site production: reducing wastage on materials. - Good quality to minimum defective works to lower demand on future repair and maintenance works, - Noise and air pollution - away from the domestic area. - Replace timber formwork. - Recycling (e.g. reinforcement, formwork) - Accurate ordering of material - avoid over ordering causing wastage. - Smooth concrete surface to reduce/eliminate finishes (direct painting or tiling without plastering). - Hollow units to save materials. - Hollow units to reduce dead load to saving structural components (e.g. foundations, columns). - **Prestressed Concrete:** - Fully utilize the strength of materials (concrete and steel rebar). - Pre-tensioning is carried out in the factory (more difficult in site) - Thinner slab, no/shallow beam design to save materials and save foundation cost, reduce building height (thus less wind load). - For example, Cambridge House in Quarry Bay used U-shape pre-tension beams. - **Safer:** - Minimize work at height. - There is a tidier site - housekeeping - More machine-robot to substitute the workers. - Minimize weather exposure (heat, rain). - **Higher Productivity:** - Use of machinery, e.g the vibration table for the compaction - Reduce demand on the tower crane (lifting reinforcement, concrete, formwork) ## Prefabrication - **Once the site has adopted prefabrication, what are the important considerations for prefabrication on the site plan?** - Make sure the tower crane can pick up the material - tower crane capacity in relation to the working radius. - The area in storing the prefabricated material - consider the construction speed, the number of items you can pick up in a day. So, you need to choose a suitable working area to store the prefabricated materials in relation to how fast you consume to pick up all the materials and arrivals of the materials. - The internal access - whether the internal road to allow the car to turn around on site.