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  1. Zambo

    Concrete Admixtures

    I m looking for an online resource that will start me off on a guideline i am starting to make. I want to find out the typical base chemicals that are used in both concrete plasticisers and retarders (my expectation being that a retarder for example could be based on 2 or 3 different chenicals)...
  2. Zambo

    Bored Pile Detailing

    On large diameter bored piles i typically see piles overcast (i.e. the concrete placed say 1.2m above cut off level) this pushes out any concrete mixed at the top with polymer and also covers the rebar at the top of the pile protecting it during excavation. This usually works out well because a...
  3. Zambo

    LNG Tank

    I have worked on various prestressed structures over the years and I am now working on a large LNG Tank. I am wondering about not using a specialist post tensioning company but inststead do the prestressing with our own resources. We can buy all the materials including anchorages. The equupment...
  4. Zambo

    Marine Clay

    Would it be reasonable, as a rule of thumb, to define the presence of marine clay as a clay soil where the SPT value N = 0. The reason for this question is to determine the likelihood of Negative skin friction. We have consolidated soils but it is difficult to show that further consolidation and...
  5. Zambo

    Slope Stability - Open cut excavation

    I have a foundation about 3m deep which I want to excavate open cut. I have space available around the excavation so do not need to add the expense of an earth support system. But how to calculate a safe angle for the stability of the excavated face. The excavation is in sand and I plan to use...
  6. Zambo

    Concrete Cover

    I am interested in board members views about concrete cover and construction joints. Over the years if the drawings show either a column penetrating into a slab or beam or a bored pile penetrating into a pilecap I would allow the horizontal bars to sit directly onto the construction joint...
  7. Zambo

    lightning protection down conductors

    I have a 220m structure that requires a lightning protection system. I am used to seeing 75mm2 or 120mm2 copper tape, but I want to find a way to justify the design. ANSI/NFPA 780 gives me a minimum of 58mm2 IEC 61024-1 I think, but I'm not sure has a minimum requirement of 50mm2. Can anyone...
  8. Zambo

    Sheet pile design

    I want to design a cantiliver sheet pile excavation support system for a foundation. The foundation is 20m diameter and 4m deep, soils are sand for 3m depth and then medium dense clay. I have a graph that gives me an answer for sheet pile length and section. But can anyone point me towards...
  9. Zambo

    Mozambique

    Does anyone have experience of work in Mozambique, in urban and industrial areas - not rural? I am pricing a job for which we need a reliable supply of concrete,apart from strength the construction method requires good control of workability and we will be using retarders and plasticisers. The...
  10. Zambo

    In need of a definition

    I am looking for a definition, but need some substantiation (a quote from a text book or other source) Is a raft foundation a structure supported directly by the underlying soil or can it also include a foundation supported by piles? Any help appreciated.
  11. Zambo

    Large Foundation India

    We are planning to cast a 10,000m3 foundation in India in a single pour. It will take about 8 weeks to get the formwork and rebar in place and then we will proceed with casting in about 4 or 5 days, assuming we can get enough resources together i.e batching plants, trucks and concrete pumps...
  12. Zambo

    Rain - force majeur, act of God?

    I'm working on a project, non-standard conditions of contract. For "bad weather" as the contractor we are referred to a clause covering force majeur (which includes acts of God). But is unseasonally heavy rain covered by such a clause? Of course maybe the contractor has to prove the rain has...
  13. Zambo

    Reducing Concrete Strength

    I am in a remote location using 20MPa concrete (about 3,000 PSI, I think!) This concrete mix design used to show about 70% strength at 7 days and gain strength normally until the 28 day cubes were crushed. Now this has become random with either a few % rise in strength or sometimes a small...
  14. Zambo

    Wall saw cutting rates

    We are using a Hilti wall saw for a demolition project. There is about 3,000m of reinforced concrete wall to cut, we have a wall saw with diamond tipped cutting discs. THe wall thickness is 300mm. Does anyone have experience of a similar job and knows the cutting speed and the number of metres...
  15. Zambo

    Design of temporary pad foundation

    I have a question about the design of a pad foundation. We had an SI carried out which included borehole log, SPT results and lab soil tests. The SI was professionally done and then this was given to a structural engineer to carry out the design of a temporary pad foundation for a tower crane...
  16. Zambo

    Painting Concrete

    We are painting concrete using an epoxy primer followed by acrylic poyurethane top coat. Total DFT is 300 microns. We planned to use WFT readings and then as a check random Elcometer destructive DFT tests. We were then told that this sort of DFT scratch test was not to be used and we must use a...
  17. Zambo

    Jet Grouting

    We propose to use jet grout columns to create a foundation to support a relatively small rock breakwater. The columns will be constructed approx 20m into the seabed (depth of water averaging 10m). Has anyone any experience on this type of project, one concern is environmental issues from escape...
  18. Zambo

    Diaphragm wall permeability spec

    Can anyone recommend to me an international standard or code of practice for diaphragm wall construction. The specific point I'm interested in is a permeability specification for the completed wall including the vertical panel joints. Thank you for your advice.
  19. Zambo

    Excavation by grab

    I have seen clamshell grabs used for dredging (silt or sand) and for rock (say 3-10 tonne blasted rock) but what about excavation. Is it possible to use a wire operated clamshell to excavate a stiff clay? Or is it necessary to excavate with hydraulic equipment and use the mechanical grab just...
  20. Zambo

    Groundwater monitoring

    We have a 20m deep concrete cut-off wall. We will excavate to one side of the wall and pump out water to form a base slab. On the other side of the wall there is a property line about 25m away. We want to carry out groundwater monitoring to ensure our pumpng has not significantly lowered the...

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