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Contract No. NL/2017/03 Tung Chung New Town Extension – Reclamation and…

- - - - concrete cube test
        
        test for compressive strength
        
        One sample per each specified quantity of concrete and two 150mmx150mmx150mm test cubes for each samples10.
        
        The cubes shall be made and store in accordance with CS1.
        
        The average cube strength shall be considered as the results of the sample11.
        
        Any test result shall not be less than the grade strength by appropriate amount as stated in GS (2 or 3 MPa)12.
        
        apply load opposite sides of the cubes as cast
        check dimenstion and weight of the cube before testing
        load is increase gradually
        
        The average of any 4 consecutive test results13 shall exceed the grade strength by an appropriate amount as stated in GS (2 to 5 MPa).
        
        In case more than 40 test results are available, a more stringent requireemtn shall be applied that the standard deviation does not exceed 8 MPa. If such limit of deviation is exceeded, the concrete quality shall be investigated.
        
        Concrete cores or other tests shall be carried out in case the requirements for compressive strength do not comply.
        
        7 day cubes may be prepared on request of the Engineer or the Contractor, but no contractual significance
        
        Too large of standard deviation indicates a poor quality control
      - slump test (why)
        
        will you allow contractor to place the concrete if slump test fail?
        
        Slump = min. 75mm / 125mm to reflect the workability
        
        With higher slump, less degree of compaction in a shorter duration is
        
        required to fill up the void
        
        test
        
        One sample per each batch and two specimens for each samples.
        
        The average slump value (from two specimens) shall be within 25mm or 33% of the approved slump value, whichever is greater.
        
        Slump test is a good indication of the consistency of concrete
        
        Slump test is carried out before superplasticiser is added to ensure no excessive water is added.
        
        Too high slump – not used, excessive water? or wrong mix?
        
        Too low slump – difficult to place and compact, too long time in truck mixer
        
        test for workability
      - cement, PFA, aggregates, water
        and admixtures
      - filling joints in concrete
        
        Joint filler:
        
        CJ/MJ
        
        Joint sealant:
        
        Bond breaker tape:
        
        Bearing strip for sliding joint:
        
        Waterstops:
        
        *Design life of a RC structure:
        
        *Concrete in marine structure:
      - concrete finished type F1, F2,F3,F4,F5 (best)
        GS table: 14.1
        
        description of surface: box culvert/water retaining structures are different.....external below FGL, external above FGL, internal
        
        depend on the type of formwork, concrete with PFA/GGBS
      - Test for concrete surface harness
        
        rebound hammer test
        
        presses on concrete surface and it measures the surface hardness of concrete
        
        sensitive to the presence of aggregates and voids at the concrete surface, it is necessary to take more than 10 readings over the area of test (CANNOT SUBSITUTE FOR CONCRETE COMPRESSION TEST)
      - concrete placing method
        
        by pumping
        
        Major problem of pumping for concreting works:
        In pumping operation, the force exerted by pumps must overcome the friction between concrete and pumping pipes, the weight of concrete and the pressure head when placing concrete above the pumps. In fact, as only water is pumpable, it is the water in the concrete that transfers the pressure. The main problem associated with pumping are the effect of segregation and bleeding. To rectify these adverse effects, the proportion of cement is increased to enhance the cohesion in order to reduce segregation and bleeding. On the other hand, a proper selection of aggregate grading helps to improve the pumpability of concrete.
      - curing
        
        by ponding
        
        this method of thermal curing is readily affected by weather condition (cold wind). Moreover, a large amount of water used has to be disposed off the construction sites after curing.
        
        by polythene sheets
        
        this method of curing is based on the principle that there is no flow of air over the concrete surface and thereby no evaporation can take place on top of the freshly concreted surface by provision of Polythene sheet. However, it suffers from the demerit that Polythene sheet can be easily blown off in windy condition and the performance of curing would be affected. Moreover, for water lost due to self-desiccation, this method cannot replenish these losses.
        
        purpose
        
        reduce the rate of heat loss of freshly placed concrete to the atmosphere and to minimize the temperature gradient across concrete cross section
        also, reduce of the loss water from freshly placed concrete to the atmosphere
      - concrete vs grout
        
        Shrinkage of grout is several times that of concrete with same mass (https://www.structuralguide.com/shrinkage-in-concrete/)
        
        The effect of creep of grout is far more than concrete
        
        Heat of hydration of cement with water is more than normal concrete and this leads to the problem of severe cracking.
      - concrete cover
      - marine concrete
        
        sulphate resisting CEMENT (C3A) not used in marine concrete (react with chloride ions) and leads to corrosion of steel
        
        portland cement: C2S, C3S, C3A, C4AF
        
        two types of cement: portland cement(commonly used) & high-alumina cement(banned)
        
        high-alumina cement has a high rate of strength development, resists sulphate attack, stands up very well to sea water, and can withstand prolonged exposure to high temperatures.
        
        However, if exposed to hot, wet conditions, its strength may be considerably reduced by the conversion of the hydrated cement to a form which is chemically more stable but mechanically weaker.
        
        The main components of Portland cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite. In sulphate resisting cement it contains a low amount of tricalcium aluminate in order to avoid sulphate attack.
        Otherwise tricalcium aluminate would react with sulphates to form calcium sulphoaluminate and gypsum that cause expansion and crack the concrete structure.
        However for marine concrete sulphate resisting cement should not be used because tricalcium aluminate has high affinity for chloride ions. This is based on the possible reaction of chloride ions and tricalcium aluminate to form calcium chloroaluminate hydrate as suggested by P. Kumar Mehta (1991) and the reduction of which may increase the rate of chloride attack to the concrete marine structure and result in faster corrosion of steel reinforcement in marine structures.
    - - Reinforcement connector: coupler
      - Reinforcing steels
        
        cat A-E
        
        coating:epoxy / hot dip galvanizing
        
        sampling rate refer to GS15 table 15.1
        
        public lab for testing
        
        mill certificate, delivery note, heat no., bar bending schedule
  - - - 1.Easy handling and installation due to low weight and flexibility Internal, external and microbiological corrosion resistance
        
        2.Good hydraulic properties and No encrustations
        
        3.Good abrasion resistance Good chemical resistance Frost resistance Environmentally-friendly
        
        4.Suitabillty for contact with food stuffs (will not impart taste/odour to drinking water.
        
        5.Life-span of more than 50 years (low annual depreciation costs)
    - - type D1,E1,F1,G1,H,I,J,L (according to DSD standard drawing)
    - - type A
      - type B
  - - - 1 Hold points mean construction activities, stages, elements and particular aspects or details of any item of works, the inspection and acceptance of which by the site supervisor staff must be obtained before the contractor can proceed to the next construction activity, stage, element and particular aspect/detail of such works.
        2 Witness points are tests of materials/equipment, performance tests of prototypes as well as testing and commissioning of any item of works/installations, which require the site supervisor staff’s witnessing or recording. The contractor may however proceed to the next hold points or witness points even if such witnessing and recording have not been conducted by the site supervisor staff within the notified time frame.
      - type of record
  - - - MTIA
- - - - Marine Traffic Assessment and set up marine management working group...to coordinate marine traffic with nearby stakeholders and interfacing contractors
      - Marine Logistic team (to liaise with relevant authorities)
    - - plant: Split barges are deployed for dumping public fill to -2.5mPD. Afterwards, end dipping of public fill by dump trucks will be carried out up to +2.5mPD which is the designed reclamation level.
      - mudwave (failure of slip surface)
        to solve it....use derrick barges by grab method to place the public fill (ensure the loading is even distributed)
  - - - reclamation procedures:
        (1) place of geotextile
        (2) place 1.5m sand blanket
        (3) place public fill until -2.5mPD by slipt barge(hopper)
        (4) then the seabed become shallow...then use end-tipping by dump truck to fill until +2.5mPD(for deep depth).....(for shallow depth) use derrick barge by grab method to place the public fill to prevent mad wave issue
        (5) DONE
        
        in case of mud wave, what to do?
        
        function of geotexile
        
        (i) they separate reclamation fill from marine mud.
        
        (ii) they may act as reinforcement to enhance the stability of reclamation.
        
        However, the reinforcement function is still under heated debate because it's performance as reinforcement depends on several factors like the directional strength of woven geotextiles and damage effect by installation of vertical band drains.
        
        function of sand blanket
        
        (i) it spreads the load of future public dump on top of it.
        (ii) it acts as drainage path for dissipation of excess pore water pressure for band drain installation.
      - remove material from seabed....by suction hopper / grab dradger
        
        environmental issue: turbulence (EIAO)
    - - background of BC6
        twin-cell unit
        175m long with 45m precast section
- - - - SRE, RE
        
        CIVIL ARE(MEEEE)
        
        Quantity Survey Team
        
        Survey Team
        
        Inspection Team
        
        Drafting Team
        
        Adminstration Team (GO: SCO, CO, ACO, CA, Site clerk)
        
        Labour Relation Team
        
        record for main con staff, subcon workers. to ensure the salary are paid on time, according to government law
        
        (1) mainly do contract admin & site supervision works-->ensure comply with contract requirement (Contractor provided the works according to contract requirements)
        (2) monitor the progress
        (3) uphold safety & health & environmental (SHE) standards
        (4) management & coordination
        (5) commercial issues
        
        (4) design review!! (need to revise on structural side of box culvert)
        
        dead load by self-weight, soil load, traffic load, lateral earth pressure, hydraulic pressure induced by groundwater and hydraulic pressure induced by container water and surcharge
        
        bearing, sliding and overturning against the factor of safety