Concrete (Petrography) Testing & Inspection

Concrete is composed of sand, gravel, crushed rock, or other aggregates held together by a hardened paste of cement and water. As the architecture of any major city around the world can attest, concrete is one of the most widely used structural building materials. 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 & water content and type, distribution and quality of aggregates are various factors that effect properties of concrete. It should be noted that a concrete that is durable and otherwise satisfactory under normal atmospheric conditions might be wholly unsuitable under severe, environmental and eroding conditions. Water tightness is essential for hydraulic structures, but strength and rigidity are obviously important requisites for an office building.

Petrographic testing is typcially performed to determine what the underlying cause or reason that failed concrete is due to.  This may involve one or more of a variety of the following concerns commonly found in the premature failure of an existing concrete structure.

Who's At Fault When Things Go Wrong?

Petrographic analysis enables liability to be assigned in the event of a premature concrete failure.  This means that although there are a variety of instrumental variables, identifying the root cause of failure is one of the most important aspects of concrete testing (petrographic analysis).  Once determined who is most responsible, liability can be assigned based on scientific test results performed in accordance with ASTM or other standard practice.  Typically, the responsibility for concrete failure can generally be assigned to one of more of the following:  Ready Mix Supplier; Concrete Contractor Finisher; General Contractor; or Agregate Supplier.  Each has specific concerns that must be examined to determine liability.  They are as follows:

Ready Mix Supplier

• Poor quality air void system
• High water/cement ratio
• Improper setting time due to admixture dosage rate
• Improper mixture proportions

Concrete Contractor - Finisher

• Adding water at the site
• Improper finishing techniques
  • Finishing too early
  • Finishing too late
  • Adding water to surface to facilitate finishing
  • Overworking - loss of entrained air at the surface 
• Improper curing
• Sawcutting of joints
  • Improper timing
  • Improper spacing
  • Improper depth

General Contractor

• Protection of concrete from adverse weather

Aggregate Supplier

• Aggregate quality
  •   Deleterious aggregates
  •   Soft absorptive aggregates - prone to popouts
  •   D-cracking prone aggregates
  •   Alkali-silica reactive aggregates
  •   Dirty aggregates

Petrographic analysis can be used to determine chemical and physical irregularities in concrete. This type of analysis can be used to determine chemical attack, identification of reactive aggregate, strength, mixture proportion estimates (such as water/cement ratio), cement and fly-ash content, corrosion potential of embedded steel, degree of carbonation, aggregate size and distribution, presence of alkali-aggregate or sulfate reaction. This type of information can aid to provide, the root cause of failure and extent of cracking, dusting, scaling or coating delamination.

Matco Services performed petrographic analysis, potential mapping and detailed corrosion investigation on the above bridge. Based on failure analysis findings and root cause, inspection protocol was established.

Concrete Testing, Coating Selection and Failure Analysis: Matco Services highly experienced concrete specialists are available for onsite, laboratory testing and root cause determination for failures of concrete and concrete coatings. Adhesion testing per ASTM standards, FTIR testing, light microscopy, and SEM/EDS are the most common analytical services that we provide for these types of investigations. We also advise in the selection of coatings, considering chemistry and corrosivity of environment, freeze-thaw cycles, and waterproofing requirements.

Concrete Floors and Moisture- 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. Modern construction practices often use vapor retarders to produce a moisture resistant floor. They are not often present in older constructions. High moisture vapor transmission rates for concrete slabs can result in the debonding of tile and carpet; warping of wooden floors and even microbial growth. The moisture vapor emission rate can be determined in accordance with ASTM F1869. Most manufacturers of floor coverings will specify a maximum acceptable moisture transmission rate.

Cracking in Concrete Structures- Cracking and spalling of concrete in parking garage structures in 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 (related to the water/cement ratio), and the presence of waterproof coatings on the concrete surfaces can affect the occurrence of the corrosion process. The volume expansion that happens when iron corrosion products are formed can exert enough localized pressure to crack and eventually spall the concrete cover. The presence of melt water and the use of chloride deicing salts will exacerbate the problem. The potential for corrosion of uncoated reinforcing steel can be determined by performing half cell potential mapping of uncoated concrete in accordance with ASTM C876.

Strength Testing: Compressive strength is the primary structural characteristic of concrete. Both it and other kinds of physical characteristics can be measured in our laboratories.

We have a vast array of laboratory and field testing equipment. All of Matco Services testing equipment is calibrated on a routine basis in accordance with both national and international standards, and is ready to be put to use at a moment's notice.

An illustrated formal report documents the results of the investigation. If necessary, Matco Services personnel can usually be on site almost immediately when requested during emergency situations.

We Value Our Customers... Throughout the years, we have noticed that much of our business comes from repeat customers. Our expertise and well-equipped lab can account for much of this, but we believe there is something more to it. We attribute it to the fact that we promote an open and friendly environment that is never too busy to meet your needs. At Matco Services, we value your business whether you are a large corporation or a small enterprise. We will provide you with the attention you need and deserve. We invite you to visit us and get to know our staff, and share in the learning experience.

Why Choose Matco Services? As one of the premier testing and failure analysis firms featuring state of the art equipment, Matco Services is able to provide a unique and diverse blend of services. Thousands of investigations have been performed at Matco Services, ranging from jet engines and boiler tubes, to computer components and implants. Projects are not only conducted on your schedule from initiation to completion with competent and experienced personnel, and conducted in a discrete manner that ensures confidentiality as well.

Typical Projects

Although Matco Services work is vital to its clients, it is rarely seen by the public. Here are some examples of recent jobs in which Matco Services provided the timely, competent, customer-oriented engineering analysis that made the difference.

Failure Analysis: Metallurgical support for a major commercial airline fleet (US Airways) that includes failure analysis investigations, corrosion investigations, and quality control testing. Bridge and construction failure investigations are routinly performed at Matco Services.

Corrosion Engineering: Cathodic protection system design and installation for a submerged ocean tunnel for the off-loading facility of the largest liquified natural gas (LNG) process facility in the United States . Our certified team of corrosion investigators can perform testing to evaluate the integrity of pressure vessels. These include refineries, underground and above ground oil, gas and chemical process facilities Our team has performed such analyses nation and worldwide, and will travel to your project site at a moments notice for emergency evaluations.

Paint/Coating Analysis: On-site and laboratory investigation of paint delamination failures (flaking and peeling) on galvanized structural members of several major stadiums in the United States.

On-site Inspection: Our certified team of inspectors can perform non-destructive testing on project sites to evaluate the integrity of large structures. Our team has performed such analyses nation and worldwide, and will travel to your project site at a moments notice for emergency evaluations. Such large structure evaluations have included off-shore oil platforms, wind power generation towers, concrete domes and stadiums, large underground cooling systems, and large elevated water towers. Our projects have taken us from Aloha Stadium in Hawaii to Alyeska Ski Resort in Alaska; from bridges in the Bahamas to titanium structures in Tokyo, Japan and damage evaluation of hurrican in Florida. This project included roofing, siding, paint and internal water damage for a large structure.

Enviromental Testing: Comparative testing of the resistance of pharmaceutical labels to environmental stresses (MFG, Humidity, and QUV testing) for a major drug company to determine what labels held up the best.

Fire Investigation: Same-day analysis of the effects of a truck fire on the superstructure of a major highway bridge to determine whether or not the highway could remain open.

Explosion Investigations: Failure analysis of a gas main explosion that caused casualities.

Power Plants: Failure analysis and remaining life determination of boiler components in the power industry.

Implant Materials: Electrochemical corrosion evaluation and failure analysis of implant materials such as hips, knees, stents, etc. to improve products and performance.

Galvanized Steel: How its microstructure and galvanized layer chemistry affect its appearance and corrosion resistance. Prevention and evaluation of storage rust, cracking of galvanized layer, failure of painted galvanized steel. Cabinet salt spray testing, EIS testing of painted galvanized steel and metallurgical characterization tests are routinly performed for galavanized and painted galvanized steel panels.

Utility and Light Poles & Lattices: Inspection and evaluation of galvanized, corten and painted carbon steel utility, light poles/lattices. Failure analysis, fatigue investigations, protective coating evaluation, life expectancy determination, corrosion evaluation, underground, ground level and above ground were included in this investigations

R&D: Research & Development of new materials, coatings and sensors for the pipeline, construction/chemical industry.