NCMA CCCM flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Nominal CMU dimensions

A standard concrete masonry unit is nominally 8 in. x 8 in. x 16 in. but actually measures 7-5/8 in. x 7-5/8 in. x 15-5/8 in., allowing a 3/8 in. mortar joint to reach the 8 in. module.

ASTM C90

The standard specification for loadbearing concrete masonry units. It sets minimum compressive strength, absorption, and dimensional tolerances for units used in structural masonry walls.

ASTM C129

The standard specification for nonloadbearing concrete masonry units. These units are used in partitions and veneer where structural load resistance is not required.

ASTM C140

The test method for sampling and testing concrete masonry units. It covers compressive strength, absorption, density, and dimensional measurements used to verify compliance with specifications.

Type M mortar

The highest-strength mortar type, with a minimum compressive strength of 2500 psi. It is used for below-grade and severe-exposure masonry where maximum strength and durability are needed.

Type S mortar

A moderate-high strength mortar with a minimum compressive strength of 1800 psi. It is commonly used at grade and in masonry where lateral strength is important.

Type N mortar

A general-purpose mortar with a minimum compressive strength of 750 psi. It is the typical choice for above-grade, non-severe exposure masonry walls and veneer.

f'm

The specified compressive strength of masonry, determined by the unit strength method or by prism testing. It is the design value used in structural masonry calculations.

Coarse vs. fine grout

Coarse grout uses 1/2 in. maximum aggregate and is used where grout space is at least 2 in. Fine grout uses 3/8 in. aggregate for narrower spaces.

Grout compressive strength

Masonry grout must achieve a minimum compressive strength of 2000 psi at 28 days. This value is specified in TMS 602 and verified by testing.

Flashing height above grade

Exterior masonry flashing must extend at least 8 in. vertically above finished grade. It must include a drip edge and be integrated with weep holes for drainage.

Weep hole spacing

Weep holes are placed at a maximum of 32 in. on center and no more than 16 in. above the flashing line. They allow water collected on the flashing to drain out.

Control joint spacing

Control joints in concrete masonry are spaced at 20 to 25 ft maximum, or 1-1/2 to 2-1/2 times the wall height, whichever is less. They are also placed at openings and corners.

Face shell thickness

Standard hollow concrete masonry units have face shells at least 1-1/4 in. thick. Grouted cells require at least 2 in. of clear space between face shells.

Vertical reinforcement minimum

The minimum vertical reinforcement bar size in typical reinforced concrete masonry walls is a No. 4 bar. Lap splices are commonly 40 bar diameters or per TMS 602 tables.

Mortar joint thickness

Standard mortar joints in concrete masonry are 3/8 in. thick. This dimension is the difference between nominal and actual unit dimensions, maintaining the module.

Paver base depth

Aggregate base for pavers is at least 4 in. for pedestrian use, 6 to 8 in. for vehicular use, compacted in lifts to at least 95% density.

Bedding sand thickness

The bedding sand layer under interlocking pavers is 1 in. after compaction, installed with a screed. It should not exceed 1-1/2 in. to avoid rutting.

Paver thickness

Interlocking concrete pavers are at least 2-3/8 in. (60 mm) thick for pedestrian areas, 2-3/4 in. (70 mm) for residential driveways, and 3-1/8 in. (80 mm) for commercial vehicular areas.

Edge restraint

A rigid edge restraint, such as a concrete curb or aluminum edge, is pinned at 8 to 12 in. on center. It prevents paver migration under vehicular loads.

Joint sand

Joint sand fills the 1/8 to 1/4 in. gaps between pavers. It is typically ASTM C144 or C33 sand; polymeric sand is used for stabilization and must be installed dry.

Drainage slope

Paved hardscape surfaces must slope at least 1% (1/8 in. per foot) away from structures, with 2% typical. Positive drainage to a defined outfall is required.

Subgrade compaction

Native soil subgrade must be proof-rolled and compacted to at least 95% standard Proctor density. Organic material and unstable soils must be removed before base installation.

SRW base embedment

Segmental retaining wall base courses are embedded at least 6 in. below grade, and 12 in. for walls over 4 ft. A leveling pad of compacted aggregate is required.

Geogrid reinforcement

Geogrid layers reinforce segmental retaining walls when wall height or surcharge exceeds unreinforced limits. Grid layers are placed at design spacing and embedded in compacted backfill.

PICP base

Permeable interlocking concrete pavement uses open-graded aggregate base and joint aggregate. A storage reservoir is sized for the design storm; dense-graded base is not used.

Proof rolling

Proof rolling is the process of rolling the subgrade with a loaded truck to identify soft or unstable areas. Weak spots must be removed and replaced before base installation.

Compaction lift thickness

Aggregate base is compacted in lifts of 2 to 4 in. Thicker lifts may not achieve the required 95% density throughout the layer.

Leveling pad

A compacted aggregate leveling pad is placed beneath the first course of a segmental retaining wall. It provides a stable, level base for wall construction.

Weep holes vs. drainage

Weep holes drain water from behind masonry veneer, while hardscape drainage relies on surface slope and subsurface drains. Both prevent water accumulation and damage.

Permeable joint aggregate

Open-graded aggregate in PICP joints allows water to infiltrate between pavers. It must meet the specified gradation and be free of fines that would clog the system.

Base aggregate gradation

Aggregate base for pavers typically meets a dense-graded specification such as ASTM D2940. Gradation affects compaction, permeability, and load distribution.