Civil Engineering, Construction Technology

Precast Concrete

WHEN used as a construction system, precast concrete offers several advantages that range from improved quality to safer, long-lasting structures, says the Riyadh-based Al Rashid-Abetong (ARA), which has been serving the Saudi market for more than three decades.

The advantages of precast construction, coupled with the inherent benefits of concrete, provide a superior building material that has been proven the world over for several decades.

“Precast systems offer significant savings in construction, thanks to earlier completion dates, inbuilt fireproofing, reduced formwork, scaffolding, reduced wet trades and increased budget control,” says Munir Sultan, assistant sales and marketing manager. …

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.”
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. …

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.”
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. …

Construction Technology

Hilti’s laser meters set the benchmark

Hilti, the Liechtenstein-based construction solutions provider, has launched its unique range of laser measuring tools that aim to redefine the benchmark for performance and reliability. Equipped with Pulse Power that can emit up to one million laser pulses in a single second, the three new laser range meters – the PD 40, PD 42 and PD 4 models – overshadow all other tools of this kind in terms of measuring performance, reliability and ruggedness, according to Sam Winkler, product manager for measuring systems at the Hilti Regional Office for Middle East and South Asia, located in Jebel Ali Free Zone in the UAE. …

Construction Technology

Hempel offers ‘first line of defence’ for concrete structures

REINFORCED concrete structures in the Middle East require effective protection against the extreme climatic conditions and chloride and sulfide intrusion, which have taken their toll on numerous buildings in the region.To combat these effects at the outset, Hempel offers a proven “first line of defence” known as Contex, which is an anti-carbonation coating system. …

Civil Engineering, Construction Industry, Construction Technology

Infrastructure Breakthrough – iCrete Introduces Revolutionary New Material for Precast Concrete Producers

New iCrete product family will feature speed in application, exceptional reliability and workability, less cement, lower cost, and sections that are thinner and stronger. iCrete mixes and quality systems will revolutionize the precast methods used for construction of pre-fabricated structures and industrial parks, as well as the building of major pipelines, sewers, bridges, roads, tunnels, and railways …

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