In-situ reinforced concrete is expensive. Prior to starting there are some key checks, areas to set up, materials and pre-work processes to be considered but foremost to avoid any quality issues on site we should ask, “Has pre-cast concrete been considered as alternative?“.
Despite this we can’t always go with the factory controlled alternative so pre-start and pre-work considerations are essential here I list a few that I consider;
- Ensure a complete specification for the site has been received addressing strength and durability; ensure mix designs have the correct cement type, water/cement ratios, work-ability. Its also important to check that all mix designs have been approved by structural engineer, materials engineer and designer, before works commence. Test the mix… if not then you’re not ready.
- Ensure an adequate clean storage area is available before reinforcement is delivered. Rebar can get dirty, bent, lost and damaged from poor storage…
- Ensure that the cement type and delivered concrete temperature have been considered in the shutter design and the rate of pour. – We can look at winter working and summer working in more detail later but all these things factor into a successful defect free pour.
- Have the number of mix designs been kept to a minimum? Its all well that you have multiple options and are they clearly named as more than once a wrong mix has gone into a pour only to have it broken out at a later date when you discover that the blinding mix is in a column.
- Is testing equipment on site and operational and has the Lab been certified and checked? Do you have a cube tank and is that heated and operational?
- If you have not carried out a plant inspection then it is well worth doing so as seeing the set up, location, routes to site and facilities is vitally important.
- Plan large pours meticulously and early with concrete suppliers, your onsite batching facility, plant suppliers and subcontractors, etc. Be aware of the time between placing fresh concrete on already placed fresh concrete, taking into consideration heat developing in the concrete during curing. as the last thing that is needed is a defect.
- Make sure that your method statements take into account precautions to protect against cold/hot weather, rain and drying wind and ensure the operatives and supervisors are aware of what needs to be done to protect the work.
This isn’t an exhaustive list and nothing can prepare you more than knowledge, experience and planning and just one last thing if that wasn’t enough… it is also important to note that it is the purchaser that assumes the responsibility for technical correctness of the concrete specification.