What’s that defect?

There is a central body responsible for the operation, maintenance and improvement of roads. In England it is Highways England who has an obligation to provide safe roads and reliable journeys for the road user, Scottish roads are managed by Transport Scotland, Welsh roads by the Welsh Assembly, local roads by the relevant local authority and roads in London by TfL (Transport for London).

In the English instance Highways England are responsible for the motorways and major trunk roads which totals around 4,300 miles (about 2% of all roads in England by length). Whilst only a small number the roads carry a third of all traffic by milage and two thrids of all heavy good traffic.

Under the Highways (Miscellaneous Provisions) Act 1961, highway authorities have an obligation to maintain public highways to reasonable standards and this is done with the help of a document which is used by the maintainers called the Routine and Winter Service Code (RWSC). This RWSC identifies the Category of the defect, the duration of any hazard mitigation and the permanent repair period duration for the contractual timeframe.

The definition of a Cat 1 defect as defined in the RWSC is;

  • Defects are those that require prompt attention because there is an immediate or imminent safety risk
  • Significant disruption to the normal flow of traffic through the Network
  • Structural deterioration
  • Damage to the environment
  • Offence to road users from graffiti that is obscene, blasphemous or otherwise offensive

The definition of a Cat 2 defects as defined in the RWSC are sub-divided into two categories;

  • Category 2.1 – Not superficial
  • Category 2.2 – Superficial (i.e. does not change the characteristic or function of the asset/item)

To keep it interesting we can look at Cat 1 defects which need us to make safe, permanent repairs within a contractual time frame and defects that, due to their nature and/or location, require intervention from an Incident Support Unit (ISU) within the contractual response times. This will all vary depending upon time of day and location and can either be dealt with immediately by a Network Maintenance Crew, an ISU or where it requires a more expansive response; such as lane closures or traffic management to protect the road user whilst hazard mitigation works take place.

Initially Cat 1 defects can be dealt with in 2 different ways: reactive or proactive, and with everything else the second respective is always better.

Reactive maintenance – Cat 1 defects identified by an external third party source…Police, Highways England Traffic Officers, Local Authorities or occasionally even direct via the public.

Proactive maintenance – Cat 1 defects identified by the Incident Support Units, depot based operatives, office based staff or Inspection teams driving the Network.

In addition to those defects listed in the bulleted points above we can look at defects as examples going forward and what constitutes a Category 1 defect. As always the caveat within the RWSC is that any list should not be regarded as exhaustive, because ultimately a defect can appear at anytime with anything on any Network, this ultimately just makes life that little bit more interesting and challenging.

To get a full idea of what to look for under Cat 1 defects (and in no particular order) I am going to ask around for examples from my contacts and look at the following over the coming months;

  1. Potholes and other local defects in the carriageway/footway/cycle track, including defective ironwork
  2. Excessive standing water and water discharging on to and/or flowing across the road
  3. Damaged road restraint systems and other barriers
  4. Debris and spillage in traffic lanes or on hardshoulders
  5. Kerbing, edging and channel defects
  6. Damaged lighting columns and other street furniture
  7. Damaged, defective, displaced or missing traffic signs or signals
  8. Dirty or otherwise obscure traffic signs and signals
  9. Trees, shrubs and hedges which by virtue of their position or condition constitute hazard to road users and the travelling general public
  10. Displaced roadstuds (particularly the cast “Catseye” type) lying in the carriageway, hardshoulder or laybys
  11. Defective, missing or loose roadstuds
  12. Faults in road structures e.g. impact damage to superstructures, supports or parapets, flood damage, insecure expansion joints
  13. Difference in level (exceeding 20mm) between abutting concrete slabs at transverse or longitudinal joints in the carriageway/footway/cycle track
  14. Rocking gratings or covers in urban areas causing intrusive noise
  15. Damaged boundary fences where animals or children could gain access
  16. Defective road and sign lighting
  17. Overhead wires in a dangerous condition
  18. Blocked gully and piped grip gratings and obstructed channels, grips and slot drains
  19. Earthslips where debris has encroached or is likely to encroach on to the road
  20. Rocks or rock faces constituting a hazard to road users.

What’s that defect… Potholes

Keeping our roadways in good condition is a challenging problem due to harsh weather, unexpected traffic load, accident damage, changes in wheel load locations and normal wear and tear. All these factors degrade even new roads over relatively short periods of time.

As cost constraints and maintenance budgets tighten under the current austerity measures determining which roads need fixing becomes important process and with the introduction of the new Smart Motorway Systems throughout the country trafficking of the joints in the pavement is becoming more prevalent and giving rise to a greater number of failures on the network.

A pothole is a structural failure in the road surface where there is a loss of carriageway surface material resulting in a void being formed, and/or, a void in the carriageway surface layer that requires prompt attention because there is either a significant safety risk to the travelling public or major disruption to the normal flow of traffic. They need two things to form. Water and traffic, something which we have plenty of. The depression itself penetrates all the way through the surface course down to the base course and is the result of moisture infiltration and usually the end result of untreated crazing. As crazing becomes severe, the interconnected cracks create small chunks of pavement, which can be dislodged as vehicles drive over them. The remaining hole after the pavement chunk is dislodged is called a pothole.

There is no formal definition for a pothole recognised nationally. A pothole for this instance has been defined as a sharp edged depression anywhere in the carriageway where part or all of the surface layers have been removed and is identified when its maximum horizontal dimension is greater than 300mm and is 40mm+ in depth:

The following are for guidance only as smaller voids in more heavily trafficked areas may also be Cat 1 defects from my experience of Maintenance;

  • Voids with dimensions of 40-50mm in depth and 300mm in any direction should be considered a Cat 1 defect with a 24 hour response.
  • Voids greater than 50mm in depth and greater than 300mm in any direction should be considered a Cat 1 defect with emergency response and requires immediate attention

Designing a road…

I’ve not long finished putting a road through planning and I was asked what and how it all comes about. How you justify it, and what is entailed in actually deciding the route and designing it…

When you identify a route to be improved it normally comes about because there are problems with the existing stretch of road. This may be linked to congestion relief, unreliable journey times, a poor safety record or the need for useful access improvements.

The need for improvement will be justified through economic analysis. These economics will normally be analysed by looking at local factors such as the traffic figures. Interrogation of these figures will give traffic predictions and allow models to be produced based on observed numbers (traffic counts, mobile data ect…) by the traffic engineers. The traffic models generated through bespoke software predict various scenarios when looking at suggested improvement schemes. Once the need and the appropriate traffic models have been finalised work can then start on the proposed route.

Proposing a route is carried out by studying the terrain through which the road is to pass and identifying constraints on any route selected. There will be things like buildings, road crossings, rivers, canals, railways, airfields, areas of special landscape or environmental interest, archaeology, strategic utility infrastructure, type of soils or underlying geology etc., all of which will impact in some way on the proposed route under review.

A factor when making any selection of a route will be to recognise the type of road that will be required. For instance will it be single carriageway, dual carriageway, motorway standard. Will it need to change in character along the route? All these decisions are determined by the traffic demands and traffic models. It is logical that a road carrying more traffic will require more lanes and a greater capacity to enable it to flow freely. These matters are all covered by standards.

It then is a matter of making an assessment of the most appropriate routes through/over/under/around the constraints, or, if possible, incorporating some measure to accommodate the constraint within the design by some special feature, i.e. tunnel, bridge, culvert, creation of alternative habitat, etc.

The route selected will have to comply with the standards for minimum curvature required for the type of road required. These are all pre-determined in standards and recognise the type of road and the anticipated speed. This is required for both the horizontal and vertical alignment of the road.

Where there is a need to link back into existing highway networks, junctions will be required. Again, the type of junction will be driven by the traffic demands. There are standards that apply to the type of junction appropriate for the traffic flow and the resulting geometry standards associated with the junction choice. There will be the need to look at the roads crossing the route and decisions made to assess whether to link the road with a junction, take it across the road, but not directly connected, or stop it up altogether.

An important factor in highway construction is the amount and position of where “muck” has to be excavated and transported. This is determined by designing the road’s vertical alignment. It is desirable to obtain a “earthworks balance” for the highway. That is to say, all the material excavated in cutting will have somewhere for it to be placed on a part of the highway on embankment so that no material will need to be imported or taken off site. This assists in the economics of a scheme as “muck shift” is a large portion of the overall cost.

If a number of options for a route are found from the above exercise, these can be tested and compared.

The assessment of alternative routes will be made by comparing each option in turn against a number of factors. These will include things like;

  • Resulting geometrical layout
  • Overall affect on traffic in the long term
  • Economics and benefits
  • Affect on drivers and whether the layout is complicated
  • Affect on Non-Motorised Users – footpaths, bridleways, cycle paths
  • Affect on the local traffic whilst being constructed
  • Complexity of the construction activities and the impact on the surrounding people
  • Amount of land required
  • Affect on property – any buildings require demolition?
  • Environmental impact and affect on important ecological areas
  • Affect on Statutory undertakers and possible impacts of diversions
  • Type and suitability of the terrain – geotechnical considerations

Having made a preferred selection using the process above, the option can then be designed in sufficient detail so that the land required to construct the scheme can be identified.

It is at this point that, subject to on-going public consultation, the scheme could be taken through the planning process. The resulting acceptance (or otherwise) of this process, the scheme would be taken forward to detailed design and construction. At this point the scheme will only be changed in matters of detail brought about by detailed design. The overall layout and scope of the scheme would be unchanged.

  1. makes roads safe and useful
  2. makes roads understandable
  3. fits in context and is restrained
  4. is environmentally sustainable
  5. is long-lasting

Quality Management and Avoiding Common Defects – Seasonal working with concrete

Winter working

Two different temperatures have to be considered when working with concrete in cold weather, firstly the ambient air temperature and secondly the concrete temperature at time of delivery. The definition of cold weather is a period during the day or night when the ambient air temperature will fall below 2°C. The BS and EN standard states that the temperature of the concrete should not fall below 5°C until the concrete achieves a strength of 2 N/mm² and that the temperature of fresh concrete shall not be less than 5°C at the time of delivery.

Therefore general good practice is to only place concrete when the ambient air temperature is 2°C and rising. However, following best practice and through early engagement with the supply chain, concrete could be placed down to 0°C with not unforeseeable risk.

  • Ensure batching facilities have heated water and heated aggregate bins.
  • Review sequence, logistics, materials and methodologies to ensure best practice is followed.
  • Remove frost from rebar and formwork before pouring.
  • Monitor the concrete temperature as it arrives on site. Reject any that is below 5°C.
  • Temperature must be 2°C and rising (sometimes 4°C and rising, check specification).
  • Apply frost blankets quickly at the end of the pour; avoid thermal shock when removing.
  • Concrete will be frost damaged unless 2 N/mm² or stronger.
  • Measure the temperature gradient for large pours; thermal gradient control (insulated shutters, quilts etc.) must be designed to control the thermal gradient.
  • Concrete will ‘go off’ slower. Allow more time for slabs and beams to cure, and measure strength before striking.
  • In wall pours control the rate of rise to keep shutter pressures as designed. Masonry and Render.
  • Temperature must be 2°C and rising (sometimes 4°C and rising, check specification).
  • Provide frost protection for minimum 24hrs.
  • Avoid retarded mortar.
  • Special admixtures can be used to accelerate the set.
  • For rendered elevations, ensure the cement particle board, insulation and render are applied in quick succession; the CPB and insulation will deteriorate in a day or less if exposed to bad weather.
  • Maintain moisture in wet mortar.
  • Cover completed work with polythene to avoid desiccation.

Summer working

Again with concrete pours that take place in warm weather the same two different temperatures need to be considered, the ambient air temperature and the concrete temperature at time of delivery. Ambient temperatures up to about 20°C should not on their own cause significant problems, especially in damp or humid conditions but when the ambient temperatures of 20°C and above are in partnership to low humidity and drying winds consideration of a more efficient curing regime is needed.

The target temperature of concrete on delivery from the chute should not be more than 30°C.

  • Make appropriate modifications to concrete mixtures to manage rate of slup loss, setting time and other characteristics. Retarders, extended set control admixtures, synthetic fibers or other proven local solutions may be helpful.
  • The consistence of the material is affected. The slump/flow/slump flow of concrete reduces more rapidly. If there is water added to improve the consistence it decreases the concretes compressive strength, potentially increases permeability and ultimately affects the durability of the structure.
  • The hot weather will accelerate the loss of moisture from the surface and therefore increase the risk of plastic shrinkage cracking. Consideration of some form of protection is needed. If using hessian and water, you will need to rewet the hessian frequently (up to four times per hour) to ensure that it is effective.
  • On hot or dry days when the conditions are conducive to plastic shrinkage consider dampening the sub-grade, pans and forms and reinforcement prior to pouring concrete, do not allow water to pond however during and after this process.
  • Check the weather forecast to pick the best time to pour. Consider starting large pours at 6am or earlier avoiding working during the hottest part of the day, often between noon and mid-afternoon.
  • As the concrete temperatures increase the setting time reduces and impacts the time to place, compact and finish the concrete. Consideration of more labour is needed to achieve the work and schedule the rate of concrete delivery to avoid overloading the labour and/or equipment.
  • Consideration of how to maintain the labour in hot conditions. On a hot day you need to have access to drinking water at all times to avoid exhaustion during manual work. Also, sunscreen should be applied before starting the pour.
  • Keeping equipment out of direct sunlight until it is required to lay the concrete is a small but effective measure. This will stop the equipment from heating the concrete while it is being poured.
  • Concrete will go off quicker. Begin final finishing operations as soon as the water sheen has left the surface. Apply curing measures immediately on finishing an area; on a large slab this will be while pouring is still in progress in other areas.
  • In large elements or rich mixes faster hydration of cementitious materials down to high ambient temperatures can result in higher maximum concrete temperatures and thermal cracking.
  • Changes in temperature of the concrete may also result in cracking particularly where concrete is placed on a hot day followed by a cool night.
  • With the increased rate of hydration the surface of the concrete will dry quicker which leads to premature finish being applied, trapping of bleed water and possible debonding of the top surface with subsequent flaking/de-lamination
  • Delays in transport should be minimised although in numerous cases this is a difficult task.

None the less when it comes to planning any pour with any amount of concrete you will need the knowledge and advice of an expert. Whether that is you, a contractor or your concrete supplier depends on your project, what you are doing and how much risk it entails. To avoid pouring concrete incorrectly careful consideration and forethought is a must.

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.

Quality Management and Avoiding the Common (and less common) Defects

Dip visible in NW kerb line
Structures settlement and the after effects on kerbs and surfacing can also affect the bridge joints, making this an expensive fix for the contractor if he has not managed to sew up the earthworks package and does not have supporting quality compaction records.

Poor quality in the construction industry is one of the most common issues that results in lost time and additional costs to a contract. Year on year it costs contractors millions of pounds, damages relationships with Clients, places additional pressures on Site Teams attempting to complete a contract or results in further intervention from Designers through lengthy reports. The implication of finding such workmanship issues can be carefully navigated through controls and an understanding of what is required and what is expected from the specification/design prior to putting people to work. As with most things any defects in construction require re-work to correct the problem and the longer defects remain uncorrected, the more rework we are likely to encounter and the more rework there is likely to be involved. Ensuring that the work force and supervision have the right skills and knowledge, right tools and materials and, following completion, the right protection will all help prevent this from happening.

In the next series of posts I have decided to look at specific issues with different activities and to compile a list of checks that can be undertaken by the Engineer or Supervisor, with some examples,  to help check and ensure that we are identifying the major and sometimes minor details that people miss when planning or executing an activity. As suggested earlier defects can be avoided by sufficient planning and adequate monitoring. Allowing enough time for the work to be done properly and in the correct sequence is always particularly important.

The first at avoiding common defects will look at one of  the most common and versatile construction materials used in civil engineering – reinforced concrete. Following on from that I will go through various other trades and activities which include;

  • Formwork
  • Falsework and Temporary Works
  • Pre-concrete Checks
  • Concrete Checks
  • Earthworks Planning, Bulk Cut/Fill Operations and Finishes
  • Drainage Planning, Pipelaying and Chambers
  • Roadworks – Type 1 Sub-base
  • Roadworks – Kerbs and Finishes
  • Surfacing
  • Sheet and Bearing Piles
  • Setting Out Checks
  • Landscaping
  • Safety Fencing
  • Signs
  • Temporary Works
  • Bridge Bearings

Whilst we review the checks that we should look in the coming weeks there are some simple first steps that can be implemented to ensure the right ethos is achieved with the team to achieve good planning, good leadership and a culture that promotes good quality.

  1. Ensure everyone knows and understands the contractual project requirements and specifications from the designer and the client or clients representative. No client wants a bad job.
  2. Always read the label – People should be encouraged to refer to British Standards, European Standards and Trade or Manufacturer literature. Instructions are there for a reason, if you don’t follow them it will not go well.
  3. Learn to recognise what good looks like. If it doesn’t look right, it probably isn’t and don’t be afraid to stop the work if anything looks wrong. Allowing it to continue could cost more money.
  4. Make sure that everyone is qualified, competent and capable for the activity that you are planning to execute. Hiring a bricklayer when you need a joiner will never work. You should never assume specialist trades know what acceptable quality is, just because they come in a van with a logo on it does not mean they know what they are doing.
  5. Don’t assume a manufactured product is correct, always check what you pay for. Quality is still an issue in a factory, even where quality controls are stricter.
  6. Follow the Inspection and Test Plan set out by the Quality Team and Quality Manager, get involved with its production and complete quality inspection records as the work progresses. Quality can be as onerous as you like and sometimes those with the most letters after their name don’t always realise the workload they are enforcing on people.
  7. Ensure everyone understands the activity, the sequence and what is expected and always take photographs of the works as they progress and get sign off from those accountable or executing the work.

The Hidden Cost – Pipe damage – Early CCTV can avoid the need to excavate drainage well after installation, reducing costs and identifying defects early.

Making sure that we have enough competent supervision for the normal working week is essential before we move to increase working time to either weekend and/or night work as these are times when defects occur most frequently. We should also scrutinise our reliance on our supply chain and their ability to supervise and correct defects in the manor that we require, from painful experience there will always be a percentage that will not return to undertake the work so early intervention is essential.

Effectively its down to you to ensure that you are right first time because if you think quality is expensive…try building it twice.

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.