CONCRETE CONDITION ASSESSMENT
Our highly experienced concrete specialists are available for onsite, laboratory testing and root cause determination for failures of concrete and concrete coatings. Our comprehensive technical reports are well structured and include photographic documentation, detailed test procedures, and results that will hold up in a court of law.
On-site Concrete Inspection and Testing
Onsite Concrete Non-Destructive And Core Inspection And Condition Assessment Of Reinforced Concrete Typically Includes The Following Test Protocol:
- Review of background information.
- Photographic documentation, site evaluation, environmental considerations.
- Visual examination – to identify surface defects.
- Hammer/chain – to detect delaminations.
- Phenolphthalein – to determine depth of carbonation.
- Chloride content – to identify chloride corrosion.
- Half-cell potential mapping – to determine corrosion risk (map corrosion hot areas).
- Linear polarization – to determine corrosion rate.
- Continuity – to determine continuity / connectedness of rebar.
- Stray current identification – to determine stray current corrosion risk.
- Resistivity – to determine concrete resistivity and corrosion risk.
If required, concrete core samples are marked and retrieved for petrographic analysis. Cores are used for visual observation, compression testing, split tensile testing, verification of NDT and petrographic analysis. Core locations are selected on the basis of visual observations, hammer soundings and impact-echo testing. Concrete core samples can be shipped to Matergenics for a petrographic analysis.
Identifying Corrosion Is Only The Beginning
Determining Its Severity And Immediately Responding Can Prevent Disasters And Save Hundreds, Or Even Thousands Of Lives
Petrographic Analysis
Matergenics specializes in Petrographic Analysis, a review of the concrete matrix using microscopic techniques described in ASTM C856 to determine concrete constituents, quality, and cause of inferior performance, distress, or deterioration. Concrete is composed of sand, gravel, crushed rock, or other aggregates held together by a hardened paste of cement and water. Important properties of concrete are: durability (weather resistance, resistance to chemical deterioration, resistance to erosion), workability, water tightness, strength, elasticity, creep, extensibility, and thermal properties. Entrained air content, cement and water content and type, distribution and quality of aggregates are various factors that affect properties of concrete. Estimating future performance and structural safety of concrete elements can thus be facilitated.
“Matergenics is a pleasure to do business with! They are always ready and willing to assist.”
Mechanisms Leading To Corrosion Of Embedded Steel
Based On The Findings Of The Onsite Inspection, Condition Assessment And Laboratory Petrographic Analysis, An Analytical Review Can Be Performed On Key Structural Elements To Determine Root Cause Of Corrosion
ACCELERATED CORROSION
Hardened concrete is a permeable medium. The rate at which moisture can permeate through a concrete slab is dependent upon the overall quality of the concrete. High moisture vapor transmission rates for concrete slabs can result in the dis-bonding of tile and carpet; warping of wooden floors and even microbial growth..
CRACKING IN CONCETE
Cracking and spalling of concrete in parking garage structures is almost always the result of corrosion of the steel reinforcement. Various factors such as depth of concrete cover over the rebar, depth of carbonation, moisture permeability of the concrete, and the presence of waterproof coatings on the concrete surfaces can affect the occurrence of the corrosion process.
ELECTROCHEMICAL METHODS
The presence of chlorides can lead to severe corrosion issues. As the steel corrodes the iron corrosion products have a greater volume than the metallic steel leading to internal pressures within the concrete which then causes cracking and spalling of the concrete above and adjacent to the corroded steel.
Early Detection & Mitigation
If Accelerated Corrosion Is Captured Early On Coating Application And Cathodic Protection Can Mitigate The Accelerated Corrosion With Low Costs
Design of Suitable Corrosion Protection Measures to Mitigate Corrosion of steel Reinforcement
Cathodic protection and corrosion inhibitors will be considered to mitigate the corrosion of reinforced steel. Cathodic protection (CP) is a method wherein a sufficient amount of electric direct current (DC) is continuously supplied to a submerged or buried metallic structure to mitigate, slow down or temporarily stop the natural corrosion processes from occurring. The DC current corrodes a sacrificial anode when it is connected to a structure to be protected. There are two methods for supplying DC to cathodically protect a structure. They are the following:
- Galvanic anode cathodic protection system.
- Impressed current cathodic protection system.
galvanic anode cathodic protection system
generates DC as a result of the natural electrical potential difference (electrochemical reaction) between the metal to be protected (cathode) and another metal to be sacrificed (anode). The sacrificing metals such as magnesium (Mg), zinc (Zn) or aluminum (Al) all have a lower more negative electrical potential. The current output of this system is affected by factors such as:
- Driving voltage difference between the anode and the cathode.
- Resistivity of the electrolyte (environment).
- pH factor.
- Natural or man made environmental chemistry and/or contaminates.
impressed current cathodic protection system
comprises four main components which together constitute an electrical circuit. They are as follows:
- A controllable DC power source – usually a transformer rectifier.
- An applied anode – a material placed onto or into the concrete or surrounding electrolyte to enable current flow.
- An electrolyte – normally the pore water present within the concrete, or in the case of remote anodes, also the water, soil or mud in which the anodes are placed.
- A return electrical path – normally the electrically continuous reinforcement steel to be protected.
