Concrete Structures
Concrete structures are typically found in all industries. We carry a variety of tools an instrumentation in order to perform an assessment on the existing condition of the structure both internally and externally, followed on by performing the required engineering checks to determine the best course for remediation.
Some of the instruments and test methods we commonly use are as below:
Some of the instruments and test methods we commonly use are as below:
Strain Measurement
Strain Gauges can be installed on concrete structures just like steel and timber structures.
They are generally very long (60mm+) in comparison to steel strain gauges in order to account for the fact concrete is made of materials with variable modulus.
For more information, See our Strain Measurement Page .
They are generally very long (60mm+) in comparison to steel strain gauges in order to account for the fact concrete is made of materials with variable modulus.
For more information, See our Strain Measurement Page .
Carbonation Testing
Carbonation testing is a general method employed to measure the remaining protective properties of the concrete. Concrete protects steel reinforcement by providing a highly alkaline environment. As concrete ages, its alkalinity slowly reduces, extending from the surface inwards. This eventually leads to reinforcement corrosion. . While small core samples are commonly used as a way to understand the level of carbonation ingress, when performed over a larger area, it is readily apparent that the level of carbonation is not uniform over a surface. This is generally why spalling occurs in some areas and not others.
Half Cell Testing is used in conjunction with carbonation testing as a way to map areas of corrosion that are not yest visible.
this assists greatly with tightening project scopes when it comes time for repair.
Half Cell Testing is used in conjunction with carbonation testing as a way to map areas of corrosion that are not yest visible.
this assists greatly with tightening project scopes when it comes time for repair.
Reinforcement Cover
Reinforcement cover measurement is a method of understanding the amount of concrete cover that is present over reinforcing steel. As we carry concrete scanning equipment, this is generally displayed on screen negating the need for cover measurement. We do however occasionally pull out the cover meter and attach a suitable probe (there are several probe types) if we want to double check other results.
Reinforcement Corrosion Mapping - Half Cell Testing
Half Cell testing refers to a qualitive method of corrosion mapping. The instrument uses a clamp and probe to create an electrical circuit from the reinforcement, through the concrete.
Typically we combine this method with concrete scanning and carbonation testing as a way to locate, and core adjacent to reinforcement to allow bonding of the half cell instrument earth and attain a sample for carbonation testing.
It has proven very effective at mapping internal corrosion in areas where there is no apparent degradation. It is also a very useful test for mapping the limits of a corroded area in order to allow for more controlled project planning and expenditure.
Typically we combine this method with concrete scanning and carbonation testing as a way to locate, and core adjacent to reinforcement to allow bonding of the half cell instrument earth and attain a sample for carbonation testing.
It has proven very effective at mapping internal corrosion in areas where there is no apparent degradation. It is also a very useful test for mapping the limits of a corroded area in order to allow for more controlled project planning and expenditure.
Compressive Strength Testing
Compression testing of concrete typically falls into two categories - Destructive via core sampling, or Non destructive via Schmidt Hammer. Both have their respective places in engineering inspection & assessment.
Non Destructive Testing via Schmidt Hammer
Schmidt hammers are mechanically actuated instruments that measure how much energy concrete reflects when struck.
Through years of research, common rebound curves have been developed for general assessment of compressive strength.
They offer an inexpensive and non intrusive approach to testing of the compressive strength of concrete and are a commonly used method for existing structures. We carry both mechanical Schmidt Hammers for general site work as well as high end programmable Schmidt Hammers that are able to be calibrated to concrete batches. programmable Schmidt Hammers act as a method of quality control for checking concrete curing rates , comparing batches on large volume projects and for providing a method of measurement for early formwork stripping.
In their unprogrammed or raw mechanical state however, Schmidt hammers are considered a blunt instrument.
Do not let an engineer or contractor sell you information based on uncorrected mechanical Schmidt hammer results alone.
Through years of research, common rebound curves have been developed for general assessment of compressive strength.
They offer an inexpensive and non intrusive approach to testing of the compressive strength of concrete and are a commonly used method for existing structures. We carry both mechanical Schmidt Hammers for general site work as well as high end programmable Schmidt Hammers that are able to be calibrated to concrete batches. programmable Schmidt Hammers act as a method of quality control for checking concrete curing rates , comparing batches on large volume projects and for providing a method of measurement for early formwork stripping.
In their unprogrammed or raw mechanical state however, Schmidt hammers are considered a blunt instrument.
Do not let an engineer or contractor sell you information based on uncorrected mechanical Schmidt hammer results alone.
Destructive testing via Concrete Coring
A suitable area for coring is first determined based on the geometry of the structure. Careful consideration to structural integrity is considered before all coring activities. Concrete scanning is then employed in order to ensure no reinforcement or electrical sources are present. Once the core is removed, the hole is thoroughly cleaned backfilled with a high grade epoxy.
The core sample is immediately placed in water, transported to base and processed into set sample lengths. A NATA accredited laboratory is then engaged to perform compressive strength testing of the samples and provide a compressive strength report.
The core sample is immediately placed in water, transported to base and processed into set sample lengths. A NATA accredited laboratory is then engaged to perform compressive strength testing of the samples and provide a compressive strength report.
Comparison between concrete Coring & Schmidt hammer methods:
The below is a very good example on why coring is the preferred method of compressive strength testing when possible for setting the baseline. A few years ago, Mechanical Schmidt hammer testing was performed on an area of concrete adjacent to the core sample. As shown, site testing read a result of 50-60 MPA using a Mechanical Schmidt Hammer. Due to the large soft clay bricks present in the core sample, under laboratory compressive testing, compressive strength was below 20 MPa.
Such a large deviation in measurement can prove dangerous for the inexperienced.
Such a large deviation in measurement can prove dangerous for the inexperienced.
Compressive Strength testing of Sample removed from site
Combined Method:
In order to make full use of our programmable Schmidt Hammer, we first take core samples and test the sample both in its pre crush state as a prepared cylinder, as well as prior to the core being removed. Once laboratory compressive testing has concluded, the results are then fed back into the Schmidt hammer software to create a correction curve. This means that the hammer will now give much more accurate results when testing the remaining areas of a structure, substantially cutting down on concrete coring.
Ultrasonic Pulse Velocity
Ultrasonic Pulse Velocity (UPV) is a method to understand the internal characteristics of concrete, in particular, the speed that energy travels through concrete. It is useful for checking homogeneity of concrete ( walls, slender piles and piers in particular).
UPV also compliments other test methods such as Pile Integrity Testing in which the wave speed measurement of the concrete can be entered into the software of the Piling Instrument, improving on data.
UPV also compliments other test methods such as Pile Integrity Testing in which the wave speed measurement of the concrete can be entered into the software of the Piling Instrument, improving on data.
Concrete Scanning
We employ the latest in technology Ground Penetrating Radar (GPR) to allow for the detection , depth and location of steel reinforcing, electrical conduits and post tensioning cables. Other than for rebar location, this is used in a variety of manners from ensuring that the area is free of hidden objects before core drilling in supermarkets and buildings, to estimation of slab thickness and detection of piles.
A recent example of other benefits of GPR is on a bridge where a timber pile rotted away, producing a large void detected by the scanner during reinforcement location. Subsequent exposure of the pile revealed the full extent of the damage as shown below:
A recent example of other benefits of GPR is on a bridge where a timber pile rotted away, producing a large void detected by the scanner during reinforcement location. Subsequent exposure of the pile revealed the full extent of the damage as shown below:
