In consideration of the application of Ervas Adhesive Reinforcement afterwards, for quality purposes we may carry out various relevant tests of the material and the reinforcement system. The procedures for these tests will be divided in the following groups:


1.1      Supporting power foundation (quality and preparation)
1.2      Re-profiling mortar / matrix systems
1.3      Testing in the framework of quality care

During planning, the constructor of the project must repeatedly assess which of the tests listed here are necessary. It rarely ever happens that all listed points are relevant simultaneously and from a quality point of view. The selected tests must be included in the list of performances to be carried out.

Under all circumstances, the constructor of the project and the company carrying out the works must warrant that the works are executed in accordance with the relevant statistical measurements. In any case, the supporting parts may be removed only after the Ervas Adhesive Reinforcement is applied and after the engineer responsible for this has approved this.

1.1    Supporting power of the foundation (quality and preparation)

Determining the compressive strength of the concrete by taking samples or by using a concrete test hammer.

The scope of the test must be chosen in such a way that sufficient information is gained about the distribution of the strength of the concrete. Critical spots, especially around anchors, must be thoroughly examined. One possible investigative procedure is by taking samples with a core drill and to have these core samples checked in a laboratory. However, determining the strength of the concrete with a concrete test hammer will often suffice.

Determining the tension in the adhesive layer on the surface of the concrete and on the leveling mortar.

The bonding of the carbon laminate on the concrete surface is a decisive factor for the choice of the Ervas Adhesive Reinforcement to be applied later. The tractive forces from the Adhesive Reinforcement are conveyed through shear stresses, vertically on the concrete surface, into the concrete. Depending on the Ervas Adhesive reinforcement we recommend the following values for the quality of the supporting power of the foundation:

Ervas Adhesive Reinforcement


fct minimum value tractive strength

of the supporting foundation

Ervas G-Sheet (glass fiber)

> 0.2 N/mm²

Ervas C-Sheet / A-Sheet (C+A fiber coat)

> 1.0 N/mm²

Ervas CFK-laminates

> 1.5 N/mm²

Table 1: Minimal tractive strength of the supporting foundation fct

The tractive force of the concrete will be determined in at least three places on the concrete surface prepared for this purpose. The diameter of the strut used in the inspection is 50 mm and the ring-shaped groove must penetrate 5 mm into the concrete.

In case leveling mortar is used, on the edge of the leveling layer one inspection per square meter is required, or three inspections for larger surfaces. For each supporting strut, a ring-shaped groove with an inner diameter of 50 mm must be drilled into the core of the concrete. The objective that is aimed at in terms of tractive force is expressed in the form of an average value. Basically you should take account of a larger spread. This is why the following procedure is preferred:

The average value fctm that is the result of at least three inspections, may not be less than the value fct listed in table 1.

Evenness of the prepared concrete surface.
Tests have shown that recently applied laminates from Ervas will break loose from the concrete when the concrete is largely uneven. The high bending stiffness of the laminate will cause it to stretch out, immediately after it is pressed on. The adhesion of the fresh glue is not sufficient to keep the laminate in place against the concrete surface. Around the holes, underneath the laminate there will be hollow spaces arising in the glue. These defects will weaken the bond and are very dangerous at the outer edges of the anchors. A concave curvature, which presses the Ervas Adhesive Reinforcement against the concrete is not rejected.

Unevenness in the concrete surface must be re-profiled with repair mortar or leveling mortar respectively, which are certified as system.
Ervas Adhesive Reinforcement may not be glued to an uneven supporting foundation, because this may cause undesired torsion.

When using a metal strip of 2 meters in length, there may be no uneven parts in excess of 5 mm. Over a 30 cm length, the uneven part may not exceed 1 mm. Only leveling mortar inspected as a system may be used.

Prior to gluing, the air temperature, the relative atmospheric humidity, the dew point, the temperature of the concrete and the Ervas Adhesive Reinforcement and the moistness of the concrete must be checked.

Determining the dew point
To calculate the dew point temperature requires the relative atmospheric humidity and the air temperature to be measured. This way, the accompanying dew point temperature can be calculated. In order to assess the extent of the danger of condensation forming, the dew point temperature must be compared to the temperature on the surface of the component. This temperature must be at least 3°C higher than the dew point temperature.

Moistness of the supporting foundation in concrete

Warming up the surface provides a first indication whether or not there is interfering moisture present. A moist surface will become lighter in colour when it dries up. In terms of quantity, the level of moisture may be determined with the aid of a CM moisture meter.

1.2    Re-profiling mortar / matrix systems

When attaching mineral building materials (contract) to  the full surface, you must in any case consider a number of physical aspects. Thirty to fifty percent of the surface of the component must allow for water vapour to pass through. It is therefore not sensible to fully enclose the surface with a matrix from epoxy resin.

Ervas Adhesive Reinforcement has a special epoxy matrix which has been improved in terms of quality, based on cement. The collaboration between these binding agents, which are fundamentally different from each other, is achieved because as a result of pressure of the vapour, the cement crystals settle into the previously arisen frame from epoxy resin. With the system-certified glue, the forces from the strengthening fiber are passed on to the supporting foundation. The producers of the Ervas Adhesive Reinforcement have carried out extensive tests and systematic surveys with these binding agents.

1.3    Surveys with a view on quality care

Surveys of glue
With a view to survey glue, you may use 40 x 40 x 160 mm prisms. Based on these test strips, the tractive force in bending and the elasticity modulus are determined. These prisms must be produced on the basis of the final mix of the day. If the charge of the glue changes in the course of the working day, two additional prisms must be produced and checked.

Connecting Ervas Adhesive Reinforcement
The quality of the connection of the applied FRP reinforcement measures are of considerable importance. The connection may be checked by determining the tractive strength.

For these tests you need to use a core drill in order to drill ring-shaped grooves through the FRP- matrix, with the grooves penetrating 5 mm into the concrete. Then the supporting struts are adhered to the drilled out FRP to check the tractive strength. The concrete is supposed to break here.

This method will allow you to monitor the behaviour of the concrete in the long term. For instance, when building bridges you can test the tractive strength every ten years again.

Evenness of glued Ervas Adhesive Reinforcement
Prior to applying the product you must check of the foundation is sufficiently even. The deviation of a perfect surface over a 30 cm distance may not exceed 1 mm here and over a 2 meter distance no more than 5 mm. Curvatures that press the Ervas Adhesive Reinforcement against the concrete will not be rejected.