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Material Testing Blog

Concrete Testing and Equipment Glossary

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Concrete Testing Equipment

There are a wide variety of terms relating to concrete testing and equipment. To help you make sense of them, Certified MTP has created this concrete testing glossary:  

Air Entrainment

The intentional incorporation of tiny air bubbles (typically smaller than 1 mm) into concrete by adding an air entraining agent to the initial mix. The air entrainment process is meant to increase the workability of the concrete mix and the durability of the final structure after it has hardened. The air bubbles act as a lubricant for all the aggregates and large particles in a concrete mix and absorb stresses caused by expansion and contraction when water is frozen and melted within the porous concrete.

Compressive Strength

The measured maximum resistance of a concrete specimen to compressive loading and stress. Compression occurs when a material is reduced in volume by the application of pressure. Some materials fracture or deform at their compressive strength limit. As a result, determining and assessing the compressive strength of a concrete specimen is essential for designing sound structures and analyzing the quality of existing concrete members.

Curing

The process of maintaining appropriate moisture and temperature conditions at depth and near the surface of freshly laid concrete. Proper concrete curing allows for continued hydration, strength development, volume stability, resistance to freezing and thawing, and abrasion and scaling resistance.

Depending on a variety of factors (mixture proportions, specified strength, ambient weather conditions, size and shape of the concrete member, etc.), the curing process can take various forms. Maintaining moisture in the concrete mix can be accomplished through ponding and immersion, spraying and fogging, saturated wet coverings, left-in-place forms, covering concrete with imperious paper or plastic sheets, and applying membrane-forming curing compounds. On the other hand, using live steam, heating coils, electrical heated forms or pads, or concrete blankets can accelerate strength gaining.

Flexural Strength

The amount of bending force that an unsupported concrete beam can take before it breaks.

In-situ

Meaning “in the original place,” in-situ is concrete that is cast in its final or original location. For example, traditional strip foundations and concrete floors are made by manually pouring liquid concrete into a mould or framework on-site where it is given time to harden. This process is contrasted with pre-cast or ex-situ concrete which is poured and hardened in a controlled environment and then brought on-site to be installed.  

Maturity Meter

Concrete maturity indicates how far curing has progressed in a given structure. The concrete temperature, time, and strength gain data is gathered using maturity meters or sensors that are inserted in concrete beams and columns made of a mix that is identical to the concrete used during construction.

Pachometer

A non-destructive concrete testing device used to locate embedded reinforcing steel in concrete structures. The pachometer generates a magnetic field and measures the reaction between the magnetic field and ferromagnetic materials, such as steel and iron. From this reaction, the pachometer device can determine rebar sizes, spacing, length, orientation, the thickness of the concrete cover, and more.

Penetrometer

This is a device used for measuring the penetrability of soils. Usually round or cone-shaped, the penetrometer is pressed against the soil, and the depth of the resulting hole is measured. The measurement determines whether the soil is strong enough to support a new road made of asphalt concrete.

Petrographic Analysis

A concrete testing technique that examines and evaluates the visible properties and microstructural characteristics of structures. Petrographic analysis and examination can help identify defects and deterioration. The results of the test can help mitigate damage and determine repair or replacement solutions.         

Punching Shear

This occurs when reinforced concrete slabs fail due to high localized shear forces in the structural members or columns. Shear force means there is significant force pushing parts of the structure in one direction and another part of the structure in the opposite direction. For example, force may push downward on a concrete slab while a column supports part of that slab, providing upward force. Localized shear forces will eventually cause failure, and the column will punch through the slab. Punching shear is especially dangerous because no visible signs are shown prior to failure.

Unlike tension, compression, or bending, when a member fails due to shear forces, it is torn in two because each side of the member is being pulled in different directions.

Pycnometer

This piece of concrete testing equipment is used for measuring and comparing the densities — by measuring the volume — of solids. Pycnometers are used extensively for characterizing a wide variety of solids, such as heterogeneous catalysts, carbons, metal powders, soils, ceramics, concrete and other construction materials.

Rebar Chairs or Spacers

These devices secure the reinforcing steel or rebars within a concrete structure. They are used to hold the assembled rebars in place and then become a permanent part of the structure once the final concrete has been poured. Possessing a chair-like shape, rebar spacers can be made of concrete, plastic, and metal. Plastic rebar chairs or spacers have the advantage of affordability and fast processing, but concrete spacers improve the water tightness and strength of the concrete structure by being made of the same raw material.

Schmidt Hammer Testing

A non-destructive form of concrete testing designed to measure the elastic properties or compressive strength of concrete, specifically surface hardness and penetration resistance. The test utilizes the Schmidt Hammer, a device that measures the rebound of a spring-loaded mass impacting against the surface of the sample concrete or rock. This test is helpful for determining the overall strength of a concrete member and identifying potential weak spots.

Shear Wall

A structural member used to resist lateral forces, specifically shear forces. A shear wall is composed of braced panels that counter the effects of lateral loads acting on a structure, such as wind, seismic activity, or applied loads.

Slump Test

This test measures the consistency or workability of fresh concrete before it sets. This process helps ensure uniformity for different loads of concrete under field conditions. Governed by ASTM C143, the slump test determines the suitable ratio of water-to-cement using a mold in the form of the frustum of a slump cone, a non-porous base plate, a measuring scale, and a tamping rod.

A collapsed slump indicates that the water-cement ratio is too high and not appropriate for use. A shear slump means that the result is incomplete, and the concrete needs to be retested. A true slump can be measured in the test. After the mold is removed, the measurement is taken between the top of the cone mold and the top of the concrete slump.

  

Specific Gravity

The ratio between the weight of a given volume of material and the weight of an equal volume of water at a specified temperature. Using the Le Chatelier Flask method, this calculation determines whether the material is able to sink or float in water.

Determining the specific gravity of concrete is important because it is related to the water-cement ratio, which is directly proportional to workability and the strength of a bonding.

Tensile Strength

The concrete’s resistance to being pulled apart or stretched (the opposite of compressive strength).

Tensile Stress

The amount of force pulling or stretching concrete from opposite ends.

Torsion

A twisting action about the longitudinal axis of a structural member. Since one end of the structural member is twisted while the other end is held fixed, diagonal torsional cracks will wrap around the member. In a member without embedded steel reinforcement, cracks would propagate through the member and cause it to fail.

Windsor Probe Testing

A non-destructive type of concrete testing designed to evaluate the compressive strength of in-place concrete. Governed by ASTM C803, Windsor probe testing utilizes an electronic measuring device and probes to accurately and efficiently assess the general quality, uniformity, and relative strength of fresh or mature concrete members.

If you have questions about concrete testing equipment and concrete testing, call or contact Certified MTP to speak with our experts.

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