ACI MFTT key terms

A manufactured building block of clay, concrete, or other material used in masonry construction, typically laid with mortar; concrete masonry units are the most common unit tested in the field.

A mixture of cementitious material, fine aggregate, and water used to bed masonry units and bond them into an assembly; its hardened properties depend on proportions, water content, and curing.

A high-slump cementitious mixture of cement, aggregate, and water placed into masonry cores or collar joints to bond units, fill voids, and increase the strength of the assembly.

A classification in ASTM C270 - Types M, S, N, and O - defined by mortar proportions and minimum compressive strength; Type M is strongest and Type N is a common general-purpose mortar.

Materials such as portland cement, blended hydraulic cement, lime, and masonry cement that react with water to bind the aggregate in mortar and grout.

Sand or crushed stone passing the No. 4 sieve used in mortar and grout; its gradation, clay content, and organic impurities affect workability, water demand, and hardened strength.

Combining mortar materials in a mechanical mixer for a specified time until the batch is uniform; adding water or retempering after initial set is not permitted because it alters strength and workability.

Mortar batched at a plant and delivered to the site, or dry-bagged mortar mixed on site with water; it must meet the same specification requirements as mortar mixed from individual materials.

Selecting a representative portion of material or fresh mixture for testing; samples must be taken randomly, be large enough for all required tests, and be protected from contamination and moisture change.

A defined quantity of material produced or delivered under uniform conditions, from which a sample is taken and to which the resulting test data are applied.

Reducing a bulk field sample to a size suitable for testing by dividing it into quarters and retaining opposite quarters, repeated until the desired mass remains.

The gross cross-sectional area of a masonry unit minus the area of cores, cells, and other voids; unit compressive strength and some absorption values are reported on a net-area basis.

The mass of water absorbed per unit of bed area by a masonry unit during one minute of partial immersion; a high rate means the unit may draw water too quickly from fresh mortar.

The ratio of a masonry unit's 24-hour cold-water absorption to its 5-hour boiling absorption; it reflects pore structure and is used with absorption to judge durability.

The mass of water a masonry unit takes up when immersed, usually expressed as a percentage of its oven-dry mass; it is an indicator of durability and resistance to weathering.

A consistency measurement made on a flow table by jolting a molded cone of mortar and recording the resulting spread as a percentage of the original base diameter.

A field consistency test in which a standard cone is allowed to penetrate fresh mortar; the penetration depth is compared with a specified value to confirm the mortar's consistency.

The amount of mix water in a fresh mortar sample, found by drying a weighed sample in a microwave or oven and comparing wet and dry masses; reported as a percentage.

Field-made specimens, usually 2-in. cubes cast in reusable molds from fresh mortar, cured under standard conditions and tested in compression to verify mortar strength.

Field-made specimens of fresh grout, commonly 3-in. cubes or 3 by 6 in. cylinders, cast in layers, cured, and tested to confirm the grout meets its specified compressive strength.

The consistency of fresh grout measured by the standard slump cone; masonry grout is typically proportioned for a slump of about 8 to 11 inches so it flows into cores.

Placing fresh mortar or grout into specimen molds in layers and consolidating each layer with a tamping rod or mechanical vibrator to eliminate voids before initial set.

Protecting freshly cast field specimens from moisture loss and temperature extremes for the first day or two, before they are transported to the laboratory for final curing.

A small assemblage of masonry units, mortar, and grout (when used) built and tested in compression to estimate the strength of the masonry as it will perform in the wall.

Building prisms in stack bond using the same units, mortar, grout, and workmanship as the wall they represent, with joint thickness and grouting matching field conditions.

Storing prisms under conditions that match the wall they represent, or under the standard laboratory conditions the test method requires, until the specified test age.

The maximum load a prism carries in compression divided by its net area, typically determined at 28 days and used as an index of the compressive strength of the masonry.

Leveling and smoothing the top and bottom bearing surfaces of a prism with mortar, gypsum, or sulfur capping so that the test load is applied uniformly across the section.

The prism height divided by its thickness; because short prisms test higher than tall ones, the ratio is used to adjust measured strength to a standard condition.

The maximum compressive stress a masonry unit can carry, calculated as the test load divided by the unit's net area and reported as required by the applicable standard.

The mass of a masonry unit after it has been soaked and its surface water removed with a damp cloth; used as a baseline in absorption and strength testing.

The mass of a masonry unit after drying in a ventilated oven at the specified temperature until it reaches constant mass; it is the denominator in absorption calculations.

A written record identifying the sample, test method, test conditions, and results, with any deviations or nonconformances noted; it is the documented evidence used to accept or reject the material.

Documented evidence that a technician has the training, experience, and current certification required to perform a test method correctly and to report its results.

Scheduled checks confirming that testing machines, scales, molds, and timing devices meet the tolerances in the applicable standard, with records kept to show continued conformance.

A documented record tracing each sample from field collection through transport, storage, and testing so results can be tied to the material actually sampled.

The published procedure, such as an ASTM standard, that specifies sampling, specimen preparation, testing apparatus, and reporting requirements for a particular masonry test.