Civil Engineering, Construction Technology

Contex a weapon against corrosion

Contex a weapon against corrosion
Hempel has been on the road promoting its solution to the harmful environmental effects on reinforced concrete. Its anti-carbonation coating system Contex is a proven ‘first line of defence’ against corrosion, says the leading paints and coatings manufacturer.
HEMPEL, a global leader in the production and sales of protective and decorative coatings, recently organised a Middle East roadshow as part of its efforts to communicate with specifiers and customers and introduce new solutions to solve certain engineering problems.
The roadshow seminars, held last month (May 4 to 17) in Kuwait, Bahrain and Saudi Arabia (Riyadh, Jeddah and Makkah), covered two topics that concern both civil and architectural interests – concrete protection and colour trends.
Moataz Kamel, marketing manager for Hempel Middle East (West), spoke about concrete protection, focusing on the aggressive environmental elements that concrete is exposed to and the damage that can occur through exposure to these aggressive agents.
He also presented Contex, Hempel’s highly effective solution for the protection of reinforced concrete against these elements.
A proven ‘first line of defence’, Contex is an anti-carbonation coating system that provides proactive protection to concrete against a wide range of possible attacks and in turn protects steel rebar from corrosion, maintaining both the compressive and tensile strengths of the concrete structure.
Says Kamel: “Reinforced concrete, as an engineering material, is widely used in most civil structures. When used in various structural elements, it needs to withstand various loads that the skeleton of the building is subjected to.
“Reinforced concrete consists of concrete mix comprising cement, water and aggregate in addition to steel rebar. After hardening and curing, the concrete mix acts as a passive layer protecting the steel rebar from corrosion. This protection comes mainly due to the alkalinity of the concrete, which exceeds pH12.”
Reinforced concrete in buildings may come under attack from a number of elements in the environment. These include liquid water, intrusion of carbon dioxide (CO2) and chloride ions, and sulphate attack.”
Carbonation
Elaborating on the process of carbonation, he says: “Carbon dioxide ingresses through pores in the concrete and in the presence of liquid water, it reduces the pH value of the concrete down to pH9. This reduced alkalinity makes the media aggressive on the steel rebar, which starts to corrode.
This apart, the CO2 reacts with calcium hydroxide (CaOH3), one of the chemical compounds in concrete, to produce calcium carbonate (CaCO3), which weakens the material and causes spalling of the concrete cover.
“Also when steel rebar corrodes, its cross-section increases, resulting in internal stresses, which in turn causes cracks in the concrete cover. This process leads to cracking and spalling of the concrete cover, which will further expose the steel rebar to the environment.”
Chloride intrusion
The highly alkaline environment of good quality concrete forms a passive layer surrounding the embedded rebar, which normally prevents the steel from corroding. However, chloride ions if present in the concrete facilitate a local breakdown of the passive layer when the pH value is reduced, resulting in pitting of the steel rebar. Pitting is a form of localised corrosion and occurs mainly in the presence of neutral or acidic solutions containing chlorides or other halides.
Other factors
Concrete surfaces may also crack due to various reasons, such as volumetric changes taking place due to drying of concrete; thermal cracks and tension cracks due to tensile stresses, says Kamel.
“These cracks also contribute the process of corrosion by allowing aggressive elements to get inside the concrete section and reach the steel rebar,” he adds.
Contex’s range of acrylic coating systems provides the most comprehensive solution for these problems within the civil industry, providing both water-borne and solvent-borne systems in a wide variety of finishes.
“Contex prevents liquid water, CO2 and chlorides from reaching both the concrete and steel rebar, thus preventing all expected chemical reactions that could cause concrete degradation and initiate steel rebar corrosion,” says Kamel.
At the same time, Contex allows the entrapped humidity to be released from the concrete section, facilitating the breathability of the building.
Finally, Contex has a crack-bridging ability to overcome cracks which may occur on the concrete surface due to previously-mentioned causes. This ability ensures the integrity of the coating system, preventing it from cracking and leaving the concrete section exposed to aggressive environmental effects.
Each of Hempel’s Contex anti-carbonation coating systems has been independently tested and certified by Taylor Woodrow laboratories in the UK, as being able to provide proactive protection to concrete structures against a wide range of possible attacks and defects, he says.
These include chloride intrusion, concrete carbonation, alkali degradation, rebar corrosion, water/vapour entrapment, crack-bridging ability, ultraviolet degradation, and mechanical/impact damage.
Colour trends
As part of the road show, Hempel also focused on the latest colour trends, which will shape the fashion, interiors and many other disciplines during autumn/winter of this year. Mohamed Baitie, regional brand manager, Hempel Middle East (West), presented four main trends to the audience – Contour, Punch, Opal and Roma.
With his presentation, Baitie took the audience on a journey of how the trends were identified before they were finally presented to designers. This was achieved through workshops that brought together selected designers from different industries to create colour palettes to represent the colour trends.
The workshops were conducted by the UK-based Global Colour Research Company, which is one of the leading colour research bureaus in the world in the field of shaping the colour trends globally.
Baitie also went through the concept of every colour trend and its main elements, pointing out however that these trends do not represent certain colour schemes and hence cannot be used directly as colour cards by designers. The four palettes represent the trends of colour, texture, transparency and glossiness, which Hempel takes and translates into its colour proposition through different colour cards that are provided to its customers.
“Hempel as a worldwide leader in the paint industry is keen to base its colour proposition on the latest colour trends created by the most reliable colour research company worldwide,” Baitie concluded.

Hempel has been on the road promoting its solution to the harmful environmental effects on reinforced concrete. Its anti-carbonation coating system Contex is a proven ‘first line of defence’ against corrosion, says the leading paints and coatings manufacturer. …

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Construction Technology

BASF promotes new-age concrete concept

BASF promotes new-age concrete concept
BASF’s construction chemicals division has recently introduced a new-generation concrete concept, which combines the benefits of traditionally-vibrated concrete with those of self-compacting concrete.
Known as the Smart Dynamic Construction (SDC) concept, it has been developed in response to the new challenges for construction chemicals created by constantly changing construction techniques.
These challenges include the need for energy efficiency, higher concrete durability through perfect covering of reinforcement and higher fluid concretes to save time and money, according to Drummond Welsh, business systems manager for Admixture Systems, BASF Construction Chemicals.
The SDC concept allows the readymix concrete industry to reach these goals, he adds.
“As part of ongoing research over the past three years, BASF has been working on a solution to combine the advantages of traditional vibrated and self-compacting concretes, based on the notion that S5 concrete is not fluid enough and self-compacting concrete is not stable and reliable enough,” Welsh explains.
The result is the SDC concept suitable for upgrading S4 and S5 concretes to a higher performance level, with self-compacting characteristics and the same ease of production as standard concrete, at minimum extra cost. This new-generation concrete is easy to produce and robust in everyday use.
“The SDC concept consists of a mix design with less than 380 kg of fines; a tailor-made Glenium superplasticiser with exceptional workability retention and a low water to cement ratio; and the new RheoMatrix product – a viscosity-modifying agent (VMA) with self-organising molecules as the key element. Concrete mix designs can now be optimised to achieve unmatched and unique performance levels,” says Welsh.
VMAs are chemicals of natural origin or engineered purposely to modify yield stresses and/or plastic viscosity. They stabilise unstable concrete, significantly increasing the yield stress, with much lower increase of plastic viscosity. “Improvement of the yield stress of concrete is not enough to stabilise it; it is necessary to increase plastic viscosity at the same time. Combining the two effects, stability is improved to such an extent that the quantity of fines can be reduced,” he says.
“RheoMatrix 100 consists of a mixture of water-soluble polymers, which modifies the rheological properties of concrete. Its tailored mode of action imparts a level of viscosity within the concrete, enabling the correct balance between fluidity, passing ability and resistance to segregation – apparently opposing properties – to be achieved. This balance is lacking when the fluidity of the concrete is obtained by adding water,” Welsh points out.
Features & benefits
This innovative concept meets the existing and continually increasing demand for more fluid concretes and offers the following features and benefits to the industry without affecting flowability or strength development:
• Robust mix design with less than 380 kg of fines and day-to-day raw material;
• Slump flow between 600 and 700 mm;
• Strength C20 to C35;
• Self-compacting characteristics;
• Prevents segregation and bleeding;
• Can be used with all types of cement;
• Does not affect setting time; and
• Less sensitive to changes in water demand.
Welsh continues: “Thanks to a unique mechanism of action in concrete, savings of fines (less than 0.125 mm) can be achieved. The stable and highly-fluid concrete is close to self-levelling and thus permits installation without subsequent compaction. The placing process is easy enough to be handled by just one operator, which additionally saves up to 40 per cent of work time. This increases placing productivity up to five times. This apart, it is as easy to produce as standard concrete because the mixes are less sensitive to changes in water demand.
“In addition, the low percentage of fines such as cement – the production of which causes carbon dioxide emissions – improves the ecological efficiency of the concrete. Furthermore, this highly-fluid concrete embeds the reinforcement perfectly, giving it optimum protection against external corrosion. This characteristic increases the durability of the concrete and as a result considerably extends the lifespan of structures.
“And, due to its self-compacting characteristics, this concrete does not need to be vibrated, which means no noise and no health-hazardous vibrations for workers. Additionally, the new design guarantees a type of concrete with low stickiness, thus improving its workability.”
Application
RheoMatrix 100 is recommended whenever an increase in mix viscosity would be advantageous, especially for self-compacting concrete with low fines content (material passing the 0.125 mm sieve).
It is a ready-to-use liquid admixture, which should be added to the concrete during the mixing process together with the water. “This is particularly important in order to obtain maximum efficiency. For best performance, it is advisable to continue mixing until the concrete is completely homogeneous,” he emphasises.
In summary, the SDC concept provides a technology to simplify the production and control of a dynamic concrete, which adds economical, ecological and ergonomic values.
“It underlines the commitment of BASF’s construction chemicals division to tailor-made solutions that drive the concrete industry forward. In combination with local technical support and the backing of one of the world’s leading chemical companies, this new concept has the potential to move the market up to the next level of advanced construction practice,” concludes Welsh.

BASF’s construction chemicals division has recently introduced a new-generation concrete concept, which combines the benefits of traditionally-vibrated concrete with those of self-compacting concrete. …

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Construction Law

‘Swift’ arbitration is key

‘Swift’ arbitration is key
by Dr Chandana Jayalath
Construction contracts often include ‘keep working provisions’ for the parties to perform their obligations, despite the existence of a dispute. The contract may expressly forbid the contractor’s right to suspend work or terminate the contract, although inconsistent with the local law.
For example, under English law, there is a statutory right to suspend work for non-payment, which can not be excluded by contract.
Also, the employer may have the right to require a contractor to proceed with variations despite the time and cost consequences, not having been agreed in advance. In a fixed lump sum contract, the contractor may lodge a claim for variation, but the employer might deny it upfront on the basis of ‘lump sum’ or pay half of the cost pending evaluation at a later stage. The engineer may ask the contractor to go ahead with the rates he deems suitable whenever the contractor has no option, because of his obligation to complete works on time.
Although the contractor is supposedly responsible for quantity errors, in any typical lump sum contract where the quantities are said to be actual and correct, he will purposely keep silent in a windfall such as overestimated quantities that bring him money for nothingAlthough the contract expressly says no re-measurement is possible, the losing party may bring out this case and attempt to interpret the function of re-measurement as the ‘standard practice’.
There is usually a term implied to the effect that the client will not prevent the contractor from carrying out work in accordance with the terms of the contract, which is sometimes referred to as the prevention principle. In the UK case of Peak Construction (Liverpool) Ltd v McKinney Foundations Ltd (1970), some defective work was discovered before practical completion had been achieved.
The client was responsible for long delays owing to failure to approve a scheme of remedial works. A dispute arose concerning the contractor’s entitlement to an extension of time. Unfortunately, there was no specific provision for an extension of time when the contractor is delayed by the client, which is a fatal shortcoming in the contract. Another aspect is that many contracts do not have a mechanism to compensate the loss behind unprecedented price escalation in the Gulf region. This is where swift solutions are required to minimise potential losses suffered by parties, instead of allowing ‘loss to prevail where it lies’, particularly when contracts are silent.
Perhaps some claims are indeed necessary and the provision for making claims is essential in order to accommodate unavoidable changes, for example by granting justifiable extensions without invalidating the contract. However, problems arise when the provision is abused, for example by contractors who allegedly tender at low prices with the objective of profiting from their claims. For example, the government sector has now been bombarded by claims more than ever before.
Claims specialists have been busy with compiling claims for work suspended in recession. On the other hand, clients who attempt to aggressively suppress legitimate claims may provoke exaggerated, unjustified or even frivolous claims with the help of their in-house experts. Needless to say, the vicious circles generated by such exaggerated actions and reactions definitely add to the avoidable costs of construction.
The author therefore strongly believes in a speedy, flexible and a fair process, indeed a gentlemanly way to resolve disputes between gentlemen, as Alexis Mourre says, rather than too formal court lawyering. This is where ‘swift’ arbitration comes into play in the context of construction thus minimising the legal expenses for making and breaking claims and demoting the tendency towards interim awards and temporarily-binding decisions.
CW

by Dr Chandana Jayalath

Construction contracts often include ‘keep working provisions’ for the parties to perform their obligations, despite the existence of a dispute. The contract may expressly forbid the contractor’s right to suspend work or terminate the contract, although inconsistent with the local law. …

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Project Management

Construction Safety Management

Construction Safety Management
A GENERAL OUTLINE OF RESPONSIBILITIES FOR JOBSITE SAFETY RELATED TO “CONSTRUCTION” WORK
The following material outlines the basic responsibilities for jobsite safety related to various projects when performed by a General Contractor and various sub-contractors in the construction industry. This construction work might involve the construction of new facilities, facility maintenance, re-build, or modification. While the basic concepts of jobsite safety apply in every case, the degree of responsibility for jobsite safety assigned to the various parties involved depends on the nature of the work being performed and the degree to which necessary knowledge and resources are or should be reasonably available to them.
RESPONSIBILITY OF THE “PRIME” OR “GENERAL” CONTRACTOR FOR OVERALL JOBSITE/WORKPLACE CONSTRUCTION SAFETY
The serious nature of common construction jobsite hazards typically involved in such work, in terms of the relatively high frequency and severity of worker injuries, should dictate special efforts by top construction management to establish and conduct conspicuous, high quality safety programming for the benefit of all persons at their jobsites.
Because workplace safety is so important in regard to construction work, it is essential that initial responsibility for overall jobsite safety be clearly accepted by one party with the authority to initiate and accomplish what is required to achieve jobsite safety.
In terms of effectiveness, safe working conditions at construction jobsites are best achieved when the prime or general contractor assumes his rightful leadership role and takes primary responsibility to (a) establish, (b) coordinate, (c) monitor, and (d) generally manage the overall basic safety program content and structure for all parties and persons at his jobsite. Undefined authority among the parties involved related to jobsite safety is not a workable arrangement for such an important matter that literally effects the life and limb of each and every worker on the jobsite.
It is a logical conclusion that the prime or general contractor should assume initial and overall safety responsibility and safety program leadership at his jobsite. He has primary and overall authority and control of his jobsite. He ultimately controls access to the construction site. All persons performing work at his jobsite are either his employees or have been directly or indirectly hired or controlled by him. In addition, the prime or general contractor will, in various degrees, direct, supervise, coordinate, or monitor the progress of the work and perform various inspections to assure that the work complies with provisions of the contract and associated plans and specifications.
For these and other reasons, on a construction jobsite, the prime or general contractor possesses a singular responsibility to conduct specific jobsite safety programming. This programming should establish and provide a workplace free of recognized hazards which have the potential to cause serious injury to workers, or other individuals, at the jobsite.
When warranted by circumstances, the prime or general contractor may assign certain specific safety activities to other contractors. These contractors will then share a corresponding responsibility for jobsite safety.
DELEGATION OF SAFETY RESPONSIBILITY BY A “PRIME” OR “GENERAL” CONTRACTOR TO A “SUB” CONTRACTOR
When a prime or general contractor engages one or more sub-contractors, the sub-contractor should have a verifiable, high quality safety program. When the prime or general contractor assigns certain safety management responsibilities to a sub-contractor, reasonable adherence to state-of-the-art prudent practice holds that such a sub-contractor shall be deemed to have joint responsibility for jobsite safety. That is, while responsibility for jobsite safety may be shared with a sub-contractor, the prime or general contractor retains overall responsibility.
To illustrate this point, consider the following comparison. When a prime or general contractor delegates construction tasks to one or more specialty sub-contractors, a reasonable and prudent prime or general contractor will continue to monitor the delegated work to ensure compliance with his directives and the project plans and specifications. Certainly the party that hired the prime or general contractor reasonably expects this.
In a similar fashion, due to the importance of jobsite safety, when a prime or general contractor assigns safety responsibility and associated performance to one or more specialty contractors, a reasonable and prudent prime contractor will continue to monitor the work assigned to ensure compliance with reasonable state-of-the-art safety practice and any specific safety requirements contained in the project plans and specifications. The prime or general contractor can never relinquish his overall leadership role to ensure that a reasonable, state-of-the-art safety program is established and conducted at the jobsite.
RESPONSIBILITY OF SUB-CONTRACTORS
If it can be timely arranged or the opportunity is offered to specialty craft sub-contractors, they should actively participate in the development of the overall project safety program established during pre-job safety planning sessions conducted by the prime or general contractor, so that hazards specific to their trade are addressed. Regardless, sub-contractors have the responsibility to (a) actively participate and adhere to the safety program advanced by the prime and general contractors presented to them during pre-job planning sessions, (b) establish and implement their own safety program relative to general safe work methods and specific craft hazards not requiring assistance, cooperation, or coordination with others, (c) utilize communication procedures established by the prime and general contractors to discuss safety issues as they arise, and (d) coordinate their craft activities with the prime and general contractors and other sub-contractors as such work might relate to the safety of all workers and other individuals at the jobsite.
© Nelson & Associates, 1993

The following material outlines the basic responsibilities for jobsite safety related to various projects when performed by a General Contractor and various sub-contractors in the construction industry. This construction work might involve the construction of new facilities, facility maintenance, re-build, or modification. While the basic concepts of jobsite safety apply in every case, the degree of responsibility for jobsite safety assigned to the various parties involved depends on the nature of the work being performed and the degree to which necessary knowledge and resources are or should be reasonably available to them. …

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PMP Hints

Interview New Team Members

Interview New Team Members
Once your project is approved and ready to execute, a project team must be put together. Some of the resources might be full-time, some part-time. You may have a mix of contractors and employees. In many cases, the employee team members are assigned based on availability and best fit. However, in some cases, you need to hire for the positions. These could be employee hires or contractors.
The interview process is important – even more so if the person will be a full-time employee. Here are a few simple rules to remember before your interview.
Understand the job opening. Sometimes people interview a candidate and afterward wonder what position the candidate was being interviewed for. You can best evaluate the candidate if you have a mental picture of what he will be doing.
Understand your role. Different people usually have different roles and expectations in the interview process. For instance, you might be asked to comment on whether the candidate is a good personality fit for the team. You might also be asked to perform a technical interview. Each interviewer should understand whether he has specific interview expectations.
Be prepared. Make sure that you have reviewed the candidate’s resume ahead of time. Jot down some questions that will allow you to gain insight into the person’s background and ability. You may also have additional questions that your company requires you to ask as part of a standard review process.
Clear your mind. Do not go into the interview thinking about the sales promotion that is not going well or the problem you need to fix. While you are in the interview, focus on the discussion at hand.
Ask and listen. Have you been to an interview where the interviewer did all the talking? That is not what you are there for. Instead, ask questions and listen to the responses. Ask follow-up questions when possible to keep a dialog going.
It is good if multiple members of your team are part of the interview process. In this case, there are two main formats. The first is the “revolving door”. You get the candidate in a room and bring in the interviewers one at a time. Similarly the candidate can move from office to office to speak one-on-one with the interviewers. This method gives everyone a chance to gain an independent opinion of the candidate from different perspectives and using different questions, but it does require a longer time commitment from the candidate.
The second format is the “Spanish Inquisition.” You get the interview team in one room with the candidate. This approach lets everyone hear the same story one time and is the most efficient use of the candidate’s time. One drawback is that it can be very intimidating. You need to go out of your way to maintain a friendly and casual atmosphere. Many people’s preference for a group interview is the Inquisition, since everyone hears the same story and it gives some indication of how well the candidate responds under some pressure.
Your company is relying on you to help ensure that qualified candidates are hired. This is an important job and should be taken seriously. Whether you interview one-on-one or in a group, make sure you ask thoughtful questions and listen carefully to the responses. Then, be prepared to provide honest feedback during the interview debriefing process. This increases the value you provide to the interview process and helps your company make good, long-term hires for the future.

Once your project is approved and ready to execute, a project team must be put together. Some of the resources might be full-time, some part-time. You may have a mix of contractors and employees. In many cases, the employee team members are assigned based on availability and best fit. However, in some cases, you need to hire for the positions. These could be employee hires or contractors. …

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PMP Hints

Engage the Client Early in Issues Management

Engage the Client Early in Issues Management
Issues management tends to go more smoothly when the entire project team is comfortable working through the issues management process from the very start. If issues arise early in a project, be sure to follow your issues management process and get the client engaged in the solution. Issues become more urgent as you get closer to your end-date. Don’t let these be the first issues the client gets involved with. Earlier issues management experience will cause the client to see issues as just temporary hurdles that need to be overcome. If you haven’t engaged the client earlier in the issues management process, the client may cause more harm than good when you absolutely need him at the end, since he is not familiar with the issues management process.

Issues management tends to go more smoothly when the entire project team is comfortable working through the issues management process from the very start. …

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Contract Administration

Contractor woes

by Jeffrey Badman

Hill International director Jeffrey Badman.The contractor has submitted his extension of time claim, some months have passed but no award or response has been forthcoming from the engineer – an all too familiar scenario experienced by most contractors at one time or another.

So what can the contractor do next? There are some initial practical avenues that can be taken in an attempt to secure an award: …

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Construction Law

Disputes in Dubai: more to come?

Dubai has recently seen record numbers of construction-related court cases and arbitrations and its arbitral institutions should now prepare for a second wave before the year-end, writes HENRY QUINLAN*.
DUBAI has not escaped the widespread effects of the global economic downturn, which has had a wide impact on the construction sector, largely due to the enormous number and scope of projects in the emirate.
Liquidity has been one of the main casualties of the downturn which, together with falling property values, has put both developers and contractors under significant financial pressure. …

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