Quality Management and Avoiding Common Defects – Pre-work considerations for in-situ reinforced concrete

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…
Poor Rebar Storage
Dirty, damaged and bent from passing traffic and mud splatter makes expensive delays from reordering or cleaning prior to concrete or fixing
  • 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.
Pour Planning...
Delays between deliveries, breakdowns and a lack of contingency can result in real quality issues.
  • 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.

Record Keeping and Site Diaries

The more I look the more I realise that people are becoming more dependent on technology for recording. This is not a bad thing, photographs that contain exif data can be helpful as they give position, date, time and location. Remembering what happened and where when the Commercial Team are looking to recover costs or the Forensic Planner is trying piece together a timeline from a disaster project is always difficult so a good site diary is always a massive bonus.

Site Diaries must be maintained by the Section Managers, Supervisory and Engineering staff as nominated by Project Management. The Site Diary will constitute a formalised daily record of contractor performance and as such can be submissible.

The following points indicate the type of information that should be included in the Engineers site diary;

  1. Project Name or Project Number.
  2. Discipline and/or Section – eg. Section 5A and Drainage, Roadworks, Structures etc…
  3. Shift start time and finish time plus the type of shift eg. Day, Night etc…
  4. Weather Conditions – This should be broken down in to AM and PM and can be simplified in to a  simple one or two word statement eg. Fog, Sunny, Showers, Snow, Heavy Rain.
  5. Which operation(s) are ongoing or have started in the area under your Engineering supervision and their progress, this should be a brief description and should include the following key items;
    • Location of the activity, eg. GL G-I and 7-8 or CH196+980-20+050 Northbound
    • What the activity is, such as Earthworks Topsoil Strip, Site Clearance, Steel Erection, fixed reinforcement, poured concrete to wall etc…
    • Any rough quantities of materials imported, concrete poured etc…
    • The type of plant undertaking the work and  a short description of what is there, eg. Cat 316 or Terex AC200-1, 40t ADT, Stihl Saw, 4” Pump etc…
    • The number of men and their discipline undertaking the activity, eg. 2nr Joiners, 1nr General Operative etc…
  6. Any unforeseen situation eg. Hard dig experienced by a sub-contractor installing drainage, obstructions that possibly had not been identified in a site investigation, unchartered services etc…
  7. Any occurrence that has delayed an operation which should include;
    • Who or what was delayed
    • Who or what was ‘responsible’ for causing the delay eg. us, sub-contract, general public interface.
    • A description of what occurred to cause the delay, eg. Plant break down, delayed concrete order, road traffic accident closing a carriageway, design query.
    • The duration of the delay and the time that this delay started eg. 13:00-16:00hrs (3hrs).
    • Any mitigation that was undertaken to prevent unproductive time, eg. The drainage was stopped due to level issues and a clash with a culvert and the gang was moved on to completing MH’s. This should include any plant that has remained stood due to the change in plan.
  8. Any verbal discussions with the Client, Sub-contractors, Clients Representative, Third Parties (eg. HA, Building Control, Local Council, HSE, EA etc…). This should include any agreements that were made with the parties involved.
  9. Any instructions that you gave to other members of staff/operative or sub-contractors working for us.
  10. Any instructions that you were given by the Designer, Architect or Clients Representative.
  11. Any variations on, or changes agreed to the specification
  12. A description of any incidents or occurrences which have resulted in;
    • Accidents
    • Dangerous Occurrences
    • Damage to Private Property
    • Damage to the works completed or work in progress
    • Damage to Statutory Authority Services eg. Water, Gas, Telecommunications etc…
  13. Anything else that you think may be relevant. It does not matter if your observation encompasses another section of work, what you see  may be relevant to unnecessary costs incurred by your Business unit or could give further insight in to what is occurring in a section of works.

You should get in to the habit of completing a daily site diary during the course of the day wherever possible, a short time spent writing in to a note book what you may have seen or on to a diary sheet as you leave an area or whilst you chainman is driving through site helps greatly with spreading the workload. This prevents the need for stopping on at the end of the day to write up what has happened or in some instances forgetting what has happened during the course of a day.

A detailed diary gives a good indication of what is happening on site and some of the items listed above may have contractual implications which could require notification to your Line Manager or the Quantity Surveyor responsible for a works package or sub-contractor.

Once complete the Site Diary must be distributed in accordance with the requirements of the Project. A copy must be distributed to the Commercial and Engineering functions as a minimum.