Articles

Infrastruct Structural Testing Services for Construction

There are many structural testing and investigation techniques currently available to Owners, Operators, Engineers and Architects to examine and rapidly assess the condition of their structures. Many of these tests use Non-Destructive Testing or NDT techniques.

When the need for testing arises, either on a construction site or for existing structures, due to unknown structural properties, structural defects or material deterioration, we can use a variety of NDT techniques and intrusive investigations to determine material properties, assess the cause of defects and examine the extent and severity of deterioration. Structural testing and investigations can be used on single elements or can be expanded to assess the overall condition of existing structures.

Testing methods such as cover surveys, half-cell potential surveys and resistivity surveys on embedded reinforcement provide the essential data for a standard condition assessment of reinforcement.

A covermeter survey will quickly determine the depth of cover to reinforcement and with modern covermeters, we can determine reinforcement layout to depths of up to ≈160mm in the concrete. Moreover, covermeters can now generate images of the embedded reinforcement and estimate the rebar diameter for on-site review.

Cover meter surveys are restricted to the top mat of reinforcement in concrete. Hi-frequency Ground Penetration Radar (GPR) systems are now readily available for testing concrete structures and imaging to depths of ≈550mm. GPR for concrete structures is used by Infrastruct to gather information on rebar layouts, locating hidden defects, locating post-tensioning cables and in conjunction with the other test systems below confirming the integrity of concrete structures.

Half-cell potential surveys and resistivity measurements will indicate the risk of reinforcement corrosion in concrete but adopting the Linear Polarisation Resistance (LPR) technique will allow a determination of the rate of reinforcement corrosion.

The need to understand the in-situ compressive strength of concrete is a basic requirement for Engineers and Architects to push forward with their construction projects. Rebound Hammer surveys often referred to as Schmidt Hammer surveys are useful for screening concrete in advance of concrete coring operations. If a calibration curve, specific to a concrete region is prepared, a Schmidt Hammer survey can then be used to estimate the in-situ compressive strength of concrete.

Concrete quality and the integrity of placed concrete will affect the in-situ compressive strength and durability of concrete. Engineers and Architects need to have confidence that the concrete placed on their projects is of good quality and that there are no hidden defects within the concrete.

At Infrastruct, we use different techniques depending on the site conditions and information required. Ultrasonic Pulse Velocity tests, also referred to UPV surveys, are very useful to classify the quality of the in-situ concrete. UPV surveys are completely non-destructive and are useful for many structural configurations.

Ultrasonic Pulse Echo surveys and Impact Echo testing can locate and quantify the extent of hidden defects in hardened concrete. At Infrastruct we use the MIRA pulse echo tomograph and DOCter Impact Echo equipment for location of hidden defects in concrete structures.

Concrete permeability is critical to the durability of concrete in all service environments. Permeability is determined by many different techniques and on-site this can include air permeability testing and water permeation testing. At Infrastruct, we use different techniques, depending on requirements, to carry out concrete permeability surveys including the GWT permeability method from Germann Instruments. Careful surface preparation, understanding the moisture condition of the concrete and measurement of concrete resistivity are important for accurate surveys on existing structures.

Mechanisms that can cause concrete deterioration or corrosion of reinforcement are common and can, under certain conditions, rapidly affect the durability of concrete if we do not know the attack is on-going. Carbonation testing is used to determine the penetration of the carbonation front into concrete over time. The risk of carbonation-induced corrosion increases when the depth of carbonation is equal to or is greater than the depth of rebar cover. The rate of carbonation penetration can be modelled for individual structures for residual service life calculations.

The chloride content of concrete in structures is determined using shallow sampling depth increments, collecting the concrete dust samples and analysing the samples for chloride concentration and plotting a profile of chloride concentration versus depth and comparing the chloride content in the concrete to the depth of reinforcement cover. Chloride testing is essential to determine the risk of chloride induced corrosion of reinforcement in concrete. The rate of chloride ingress is important and can be modelled for individual structures for residual service life calculations.

The above concrete testing systems can provide Engineers and Architects with pertinent information on the condition of their structures. However, it is critical that the information gathered is correct, accurate and taken from specific locations on the structure. We always recommend that structural testing and investigations are carried out by competent engineers and technicians, trained and experienced in the use of structural test equipment.

If you require more information on structural testing and structural investigations, the right test equipment for your project or interpretation of test results or test information then please don’t hesitate to contact us at info@infrastruct.ie.

Covermeter Survey

Covermeter Survey

Cover meter Surveys

Cover meter Surveys

Covermeter Scan Result

Covermeter Scan Result

Half-Cell Potential Survey

Half-Cell Potential Survey

Resistivity Surveys

Resistivity Surveys

Rebound Hammer Survey

Rebound Hammer Survey

Schmidt Hammer Survey

Schmidt Hammer Survey

Ultrasonic Pulse Velocity testing

Ultrasonic Pulse Velocity testing

UPV Survey

UPV Survey

Ultrasonic Pulse Echo Survey

Ultrasonic Pulse Echo Survey

Impact Echo Testing - Infrastruct Structural Testing Services for Construction

Impact Echo Testing

Air permeability of concrete

Air permeability of concrete

Water permeability of concrete

Water permeability of concrete

Carbonation in Concrete

Carbonation in Concrete

Chloride Profile in Concrete

Chloride Profile in Concrete

GPR for Concrete Structures

GPR for Concrete Structures

Rate of reinforcement corrosion using LPR

Rate of reinforcement corrosion using LPR

Covermeter Survey Cover meter Surveys Covermeter Scan Result Half-Cell Potential Survey Resistivity Surveys Rebound Hammer Survey Schmidt Hammer Survey Ultrasonic Pulse Velocity testing UPV Survey Ultrasonic Pulse Echo Survey Impact Echo Testing - Infrastruct Structural Testing Services for Construction Air permeability of concrete Water permeability of concrete Carbonation in Concrete Chloride Profile in Concrete GPR for Concrete Structures Rate of reinforcement corrosion using LPR
Articles

Infrastruct Welcomes New Engineering Staff to the Company

In August, Ethan Mannion and Dr Shahnur Alam Sourav joined Infrastruct to work on structural testing and investigation projects in Ireland and the UK.

Ethan is a Mechanical Engineer with experience in both the manufacturing and construction industries.

Infrastruct Welcomes New Engineering Staff to the Company
Shahnur recently completed his PhD in UCD and joins Infrastruct to further enhance our testing and investigation services.

Infrastruct Welcomes New Engineering Staff to the Company
Since joining Infrastruct, Ethan and Shahnur have been involved in structural investigations in multi-storey buildings, moisture monitoring in both new and existing buildings, non-destructive testing to determine floor slab depth and integrity in open tanks and a Special Inspection of a 72 year old concrete bridge.

These projects involved many types of tests including:

  1. Covermeter and GPR scanning of different types of structural elements
  2. Half-Cell Potential and Resistivity mapping on structural elements
  3. Relative humidity mapping in floor slabs
  4. Pulse Echo mapping of a bridge deck to determine the in-situ depth of the deck
  5. Ultrasonic Pulse Velocity (UPV) testing on structural elements (SonReb Analysis)
  6. Rebound Hammer testing on structural elements
  7. Sampling and testing for carbonation depth and chloride ion concentration of concrete
  8. BRE Screed testing on repairs floors
  9. Anchor testing
  10. Defects mapping

Infrastruct Welcomes New Engineering Staff to the Company
All testing and investigation works completed by Infrastruct is supervised by a Chartered Engineer and we prepare a detailed interpretative report with AutoCAD drawings (as required) for our Clients.

Articles

Impact Echo Testing on Existing Concrete Floors

Impact Echo is a non-destructive test system for examining and assessing concrete elements in structures. Impact Echo is used for:

  1. Location voids and honeycombing in concrete structures (depth of defects in elements)
  2. Locating delamination (at reinforcement) in concrete structures
  3. Determining voids in post-tensioning ducts
  4. Structural thickness of elements.

Infrastruct uses the Germann Instruments DOCter Impact Echo system.

Impact Echo uses a sharp mechanical impact on the concrete surface to generate stress waves that penetrates through the concrete. The stress waves travels into the concrete and are reflected from the back wall of the element or from an anomaly within the element, for example a void.  The reflected stress wavesare picked up using a sensitive displacement transducer placed about 50mm from the impact point.

Impact echo is an expert system requiring a detailed knowledge of its use, the technique and knowledge of the concrete element under test.

Examples of Use:

  1. Locating Voids in Post-Tensioning Ducts

The team in Infrastruct were requested to non-destructively examine post-tensioned downstand concrete beams and determine the location and condition of the ducts.

We used high frequency GPR to locate the duct profile within each concrete beam and we used the DOCter Impact Echo system at small intervals to assess and record the void condition within the ducts. This was very successful at locating voids in post-tensioning ducts.

Selected duct and tendon exposures were made to confirm the findings of the DOCter Impact Echo system.

Figure 1 shows the DOCter Impact Echo system in use on the Bridge and Figure 2 shows a voided post-tensioning duct located using the DOCterImpact Echo system.

  1. Locating Piles under Existing Floor Slab

The team in Infrastruct were asked to determine, non-destructively, the depth of a concrete slab and to locate buried piles under the concrete slab.

We used a combination of test systemsincluding the impact echo which was particularly useful in areas of congested reinforcement. The piles were located and marked up on the concrete surface and a detailed report prepared for the Client.

Figure 3 shows the DOCter Impact Echo system in use on the floor slab to locate changes in the thickness of the floor.

Articles

Moisture Testing in Concrete Floor Slabs

Concrete floors and screeds should be dry enough to allow resilient floor coverings to be installed without follow-on moisture-related damage.

If moisture is present in a concrete floor slab or screed it can:

  1. Cause damage to the floor covering material
  2. Affect certain flooring adhesives
  3. Cause bubbling, blistering or delamination of the floor coverings
  4. Affect certain types of levelling compounds or underlay materials
  5. Damage certain screed materials
  6. Affect or damage wall or skirting materials or finishes.

The drying out of a concrete floor slab (moisture leaving the slab over time) is typically a slow process and a common method for assessing the floor condition is using in-situ relative humidity probes.

Infrastruct use the Tramexhygro-i2probes for in-situ relative humidity monitoring of concrete floor slabs and screeds.

ASTM Standard F2170-19a ‘Standard Test Method for Determining the Relative Humidity in Concrete Floor Slabs Using in-situ Probes’ describes the quantitative determination of the percent relative humidity in concrete slabs.

A summary of the procedure to measure relative humidity in concrete floor slabs is as follows:

  1. In hardened concrete floors or screeds, drill a hole with a specific diameter in the floor to a predetermined depth and clean out using a hole brush and vacuum system. Avoid embedded reinforcement, if present, in the slab. See Figure 1 showing rotary drilling in a concrete slab with a dust removal system prior to inserting the plastic sleeve.
  2. Push a plastic sleeve, of suitable length, into the drilled hole and cap off and seal. The plastic sleeve allows measurement of the relative humidity of the concrete at a specific depth.
  3. Install the relative humidity probe into the hole and recap as shown in Figure 2.
  4. The Standard F2170-19a recommends a defined number of RH% probes per square meter in the floor slab and requires certain test locations to gather as much information on the moisture distribution in the floor.
  5. Allow at least 24 hours for the RH% probes to achieve moisture equilibrium within the sleeve before making the relative humidity measurement. We measure relative humidity in concrete and screeds using the Tramex CMExpertII system as shown in Figure 3.
  6. Record the result carefully ensuring the reading does not drift by >1% and the probe is in temperature equilibrium with the floor.

Non-Destructive Moisture Measurement

To scan concrete floors for changes in the moisture content, the Infrastruct Team also uses the Tramex CMExpertIIdigital meter (Impedance Mode). In this mode, the meter measures the surface moisture using the electrical impedance principle.

Measurements are non-destructive and large areas can be scanned quickly. See Figure 4 showing the Tramex CMExpertIIdigital meter in operation on a floor slab.

Articles

Permeability Testing On Underground Concrete Tanks

In early 2020, Infrastruct was requested to carry out in-situ permeability testing on underground reinforced concrete tanks for a large and well-known Irish manufacturing Company. The testing on the concrete tanks was required to assess, non-destructively, the in-situ quality of the concrete and its resistance to water penetration prior to entering service for the Company.

The permeability of concrete to liquids has major implications for the durability of the concrete during its service life and on its ability to retain the liquid within the tank structure. While there is no one standard test method recommended, Infrastruct uses the Germann Instruments GWT test system for the on-site assessment of water permeability.

The GWT system can be used for:

1. Evaluation of the water permeation of the skin-concrete in finished concrete structures.
2. Testing the water tightness of construction joints and sealed control joints.
3. Testing the concrete surface before and after the application of a protective water-proof coating to assess the effectiveness of the coating and its application.
4. Evaluation of the water permeation properties of masonry structures.

Photographs 1 and 2 below show the GWT test system on the reinforced concrete walls of the underground reinforced concrete tank. Note the marked-up location of the embedded reinforcement within the walls, it is recommended to avoid testing over the reinforcement.

The results of the GWT testing was recorded on-site by our Engineers and a comprehensive report, with interpretation, was prepared for our Client.

For more information on GWT testing or any structural testing and investigations, please contact Dr Thomas Callanan in Infrastruct Asset Management Services Limited.

Articles

BRE Screed Testing On Floors

Infrastruct was requested by a materials manufacturer in January 2020 to carry out in-situ testing on a floating screed floor.

The methodology to assess the In-situ Crushing Resistance (ISCR) of bonded, unbonded and floating screeds is provided in BS 8204-1:2003 ‘Screeds, Bases and In Situ Floorings – Part 1: Concrete Bases and Cementitious Levelling Screeds to receive Floorings’.

Infrastruct used the BRE Screed Tester for the in-situ testing on this screed. The equipment used a 2kg weight (floating screed, Category C only) dropped 1m down a vertical rod onto a foot piece to impact the screed surface over a 500mm2 area. The surface indentation caused by the four consecutive blows onto the screed in the same area was measured and recorded using a simple portable dial gauge device.

This test is very useful for identifying zones of poor compaction beneath an apparently good surface.

Photographs 1 and 2 below show the BRE Screed Tester using the 2kg weight on the Category C floating screed and the portable dial gauge device, zeroed on the test area before the testing and replaced on the test area after the testing to measure the indentation depth.

The results of the testing was recorded on-site by our Engineer and a comprehensive report, with interpretation of the results, was prepared for our Client.

For more information on screed testing, please contact Dr Thomas Callanan in Infrastruct Asset Management Services Limited.

Articles

Non-Destructive Testing On Reinforced Concrete Tanks

Infrastruct was contacted by the Consulting Engineers on a project to carry out non-destructive testing on a new, above ground reinforced concrete tank. The tank was designed to retain sewage as part of the treatment process and the Engineers needed confirmation that there were no hidden defects or anomalies within the walls of the structure.

Random 1200x1200mm test areas were selected on the walls of the structure and the following testing was carried out:

1. GPR surveys on selected sections of the concrete walls to identify the location of embedded reinforcement and scan for evidence of hidden voids within the walls.
2. Check the in-situ concrete integrity using the MIRA pulse echo tomographer to generate cross section images of the concrete walls to examine the concrete for internal voids or other hidden defects within the concrete.
3. Water permeation testing (GWT) to assess the permeability of the finished concrete tank walls (permeation of water under an applied pressure of 100kPa).
4. Ultrasonic Pulse Velocity (UPV) measurements to evaluate the depth of selected cracks.
5. Crack width measurements using a microscope to check the width of selected cracks.

Photographs 1, 2 and 3 below show the test equipment in use on the walls of the tank.

The results of the testing was recorded on-site by our Engineers and a comprehensive report, with interpretation of all the results, was prepared for our Client.

For more information on non-destructive testing of concrete structures, please contact Dr Thomas Callanan in Infrastruct Asset Management Services Limited.

Articles

Reinforcement Scanning On Concrete Slats & Slabs

In late 2019, Infrastruct was instructed by the Contractor building a large Slatted Unit in the Midlands to carry out a covermeter survey to confirm the presence of embedded reinforcement in each concrete slat and slab forming the Slatted Unit.

Infrastruct used a combination of the following equipment to confirm the presence of reinforcement in each slat and slab in the Slatted Unit:

1. Proceq PM-650 Covermeter with the extension handle for line scanning on the concrete surface
2. Hilti PS-1000 X-Scan GPR system to locate reinforcement deep within certain slabs.

Photographs 1 and 2 below the Proceq PM650 and Hilti PS-1000 being used to scan the top surface of the concrete elements to locate and confirm the presence of embedded reinforcement.

The results of the testing was recorded on-site by our Engineer and a comprehensive report, with interpretation, was prepared for our Client.

For more information on testing concrete elements and structures for agricultural use, please contact Dr Thomas Callanan in Infrastruct Asset Management Services Limited.

Articles

Building Investigations

Late in 2019 Infrastruct was instructed by our Client to carry out testing and investigations on an old multi-storey building which was showing evidence of significant distress and deterioration. The goal of the structural testing and material investigation works was to conclusively determine the cause of the distress and deterioration.

The testing and investigation works included:

1. Reinforcement cover and layout surveys
2. Half-Cell Potential surveys
3. Carbonation depth measurements
4.Concrete dust sampling for chloride content analysis (laboratory testing)
5.Ultrasonic Pulse Velocity (UPV) testing on concrete beams and columns
6. Coring for:
a) Compressive strength and estimation of the characteristic compressive strength of the concrete
b) Petrographic examination of the concrete.

Photographs 1 and 2 below show the testing on the columns to determine the cover to the reinforcement and the UPV results for in-situ concrete quality assessment.

The results of the testing were recorded on-site by our staff and a comprehensive report, with interpretation, was prepared for our Client. The cause of the deterioration in the concrete was determined by the testing programme.

For more information on structural testing and investigations on buildings or other structures, please contact Dr Thomas Callanan in Infrastruct Asset Management Services Limited.

Articles

Non-Destructive Testing on Railway Track Slabs

Infrastruct was part of an engineering team that carried out a range of structural testing and investigations on reinforced concrete track slabs in a tunnel in Scotland.

Infrastruct used combination of non-destructive testing systems on this project to investigate the integrity of two separate sections of track slab.

The non-destructive testing systems used by Infrastruct to locate and target weaker areas or to locate areas with structural changes in the track slab were as follows:

  1. s’MASH Impulse Response to survey on the top surface of the concrete track slab. This testing was completed in a grid pattern on the top surface of the track slab to rapidly identify suspect areas for further investigations using other testing systems. In total, there were 328 s’MASH test points recorded and analysed.
  2. MIRA Pulse Echo Tomography on the top surface of the concrete track slab to graphically examine the concrete integrity in the suspect areas of the track slab.  Selected areas on the slab were scanned using the MIRA pulse echo system to determine if major voids or anomalies were present within or beneath the track slab.
  3. Impact Echo (Olsen CTG-2D) to survey the selected locations and map the changes in the slab thickness.
  4. Ground Penetrating Radar (GPR) to survey the slab using a 1GHz antenna on the top surface and locate embedded reinforcement and other services.

The combination of s’MASH Impulse Response, MIRA Pulse Echo Tomography, CTG-2D Impact Echo and GPR proved successful on this project in determining the defects under the track slab.

The results of the non-destructive testing were recorded on-site by our Engineers and a comprehensive report, with interpretation was prepared for our Client.

For more information on non-destructive testing on structures, please contact Dr Thomas Callanan in Infrastruct Asset Management Services Limited.

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