Know-how

Concrete

Conventional reinforcement

To strengthen concrete structures in places where shoring is difficult and demolition and restoration of concrete is tricky, RENOFORS designs and implements metal hoop reinforcement systems for columns, corbels, etc. that support the shear forces at beam supports, in addition to extra rebars embedded in the grooves cut into the concrete.

Reinforcement using carbon fabric and slats

The methods using carbon fabric and slats bonded onto concrete structures have developed over the past years to provide efficient, light, and thin reinforcements for load bearing at end restraints, in addition to steel reinforcements in parts under tension of beams, slabs, and decks, as well as for hoop reinforcement of columns.

Renfors applies these methods, which are the subject of a technical evaluation by the CSTB at the outcome of a scrupulous verification of the calculation of vertical loads and a detailed calculation of the reinforcement solution by its engineering and design department.

Whenever necessary, these reinforcement methods are the subject of specific engineering design followed by the installation of protective systems ensuring fire stability to guarantee the permanence of bonds.

Reinforcement and creation using UHPFRC

When conventional concretes do not provide sufficient durability in chemically aggressive environments or when classic solutions to strengthen concrete structures turn out to be too voluminous, Renofors designs and implements reinforcements made of ultra-high performance fibre reinforced concrete (UHPFRC).

Renofors is also able to design and implement all kinds of specific projects for architectural and/or structural uses of this type of concrete.

Protection of steel rebars in concrete

Rebar corrosion pathologies

The Renofors engineering team comprises materials science civil engineers that have scientific experience and who have acquired methods on work sites that enable them to advocate the tests to carry out on concrete to diagnose the source of corrosion on the rebars of a structure.

This expert knowledge allows them to counter the problems of processing the electrochemical phenomenon of corrosion with innovative methods.

Prescription of lab tests that need to be conducted in order to define:

• Mechanical characteristics of the concrete and its rebars (strength, elasticity)
• Characteristics associated with its durability (level of exposure and environment class of concrete - AFREM porosity, water/gas permeability - chloride pollution – ASR and/or sulphate expansion
• Density and position of the reinforcing steel (pachymetry study) combined with the mapping of the structure's potential corrosion

• Prescription of mineralogical studies of cement pastes and aggregates (type and proportions) to identify the composition of the hardened concrete (cement ratio, w/c ratio, presence of slag or pozzolans, of reactive aggregates, or of aggregates for high density cement)


• Definition of tests to measure the concrete's resistivity


• Audit criteria for the laboratories able to conduct these analyses


• Drafting of the scientific summary of the interpretation of the measurements mentioned above

The two main sources of corrosion in rebars

Conventional treatments

As any other civil engineering restoration and building company, Renofors knows how to implement the usual principles of stripping, patching, and passivation of steel reinforcement for concrete structures that show signs of spalling and bursting
For carbonated concrete with a shallow cover and/or easily accessible porosity, the use of an additional corrosion inhibitor can be considered.

However, Renofors' teams will only assess the relevance of these conventional repairs at the outcome of a diagnosis that makes it possible to determine the source of the disorders and whether the corrosion is a local phenomenon or rather all-pervasive throughout the structure, in which case electrochemical treatment should be considered.
In reality, partially diagnosed corrosion followed by isolated repairs of the spalling, which generally are anodic sites, can lead to the displacement of these anodic areas further along the rebars, thus further spreading the corrosion.

The effect of induced anodic areas rapidly leads to further bursting of the concrete close to the resurfacing patches.

Electrochemical treatment of corrosion

Galvanic protection

Renofors designs and installs systems protecting the rebars in concrete against corrosion using galvanic anodes.

When necessary, these anodes can temporarily be switched into impressed current mode to accelerate ion exchanges, so as to dechlorinate or ionize the concrete in the immediate vicinity of the rebars.

Working according to an identical principle as sacrificial anodes on the steel hulls of boats, these anodes are placed in miniature core sampling holes drilled into the concrete close to the rebars and then covered with a controlled resistivity mortar. .

Installed for the lifetime of the structure, they provide a protective galvanic current when corrosion is active. They also act as chloride collector poles.

Projected zinc

Renofors is experimenting with zinc projection techniques on concrete structures to provide galvanic protection that is evenly distributed to the rebars. These processes are complementary to galvanic anodes and seem promising for the treatment of large areas.

Impressed current cathodic protection

Renofors installs cathodic protection systems using low-voltage current impressed onto the structure to protect the rebars of concrete in chlorinated or very humid media.
They consist of sporadic titanium anodes inserted in the concrete or anodic meshes or ribbons primed in a controlled resistivity mortar applied onto the concrete.
The rebars in the concrete are protected by the displacement of the corrosion potential induced by the cathodic protection current delivered between the steel reinforcements and the anodes.

NOVBÉTON treatment: Realkalisation / Dechlorination treatment

Through the combined effects of hydrolysis and electro-osmosis, the patented RENOFORS NOVBÉTON® process allows to raise the pH level of carbonated concrete in the vicinity of the rebars, thus returning them into a passive medium.

This electrochemical process uses impressed current between the rebars in the concrete and an anodic cataplasm temporarily applied to the surface of the structure to enable the treatment of areas subject to corrosion on steel reinforcements within a fortnight. The original appearance of the structure's facing is not affected by this treatment method, thus making it particularly appropriate for structures such as historical monuments among others. A method derived from this process can be used to rid the concrete of harmful chloride pollution, by trapping it in the electrolytic cataplasm through the effect of the polarity of the current used for treatment.

Chemical treatment of corrosion

Corrosion inhibitor

Depending on the concrete’s porosity and on the more or less structural role of the part to be treated, RENOFORS can pulverize various corrosion inhibitors. The corrosion inhibitor treatment aims to form a film of stable oxides on the rebar surface. The type of corrosion inhibitor and its application method are chosen after completion of the diagnosis of the concrete’s pathology. Applications of the inhibitor via a carrying gel allow to achieve deeper penetration deptles of the inhibitor in the concrete as it involves capillary absorption mechanisums, for longer durations until the gel is removed by washing of the concrete surface.