ACI Special Inspector key terms

A measure of the consistency of fresh concrete, found by filling a standard cone, lifting it, and recording how far the settled concrete drops. Higher values indicate wetter, more flowable mixtures.

A consistency test used mainly for highly flowable or self-consolidating concrete, in which the spread diameter of concrete after a slump cone is lifted is measured instead of vertical drop.

The ease with which fresh concrete can be mixed, placed, consolidated, and finished without segregation or loss of uniformity. It reflects the combined effects of consistency, cohesion, and placeability.

The mass of water in a mixture divided by the total mass of cement plus supplementary cementitious materials. It strongly governs strength, permeability, and durability of hardened concrete.

The intentional introduction of tiny, evenly distributed air bubbles into concrete, usually with an admixture, to improve resistance to freezing and thawing and to deicing chemicals.

A field or laboratory procedure that measures the percentage of entrained and entrapped air in fresh concrete, commonly by the pressure, volumetric, or gravimetric method.

Any material other than water, aggregate, cement, or reinforcing fibers added to a concrete mixture before or during mixing to modify fresh or hardened properties, such as set time, air content, or strength.

The separation of coarse aggregate or paste from the rest of the concrete mass, often caused by excessive water, over-vibration, or dropping concrete from too great a height.

The migration of mixing water to the surface of freshly placed concrete as heavier solids settle. Excessive bleeding can weaken the surface layer and promote cracking or poor bond.

The process of removing entrapped air and compacting fresh concrete into forms and around reinforcement, typically by internal vibration, to produce a dense, uniform mass.

The maximum stress a hardened concrete specimen can carry in compression, usually determined by testing cylinders or cores and expressed in force per unit area.

A standard molded concrete test specimen, commonly 6 by 12 inches or 4 by 8 inches, cast and cured under controlled conditions for compressive strength testing.

Applying a smooth, flat layer of material such as sulfur mortar, gypsum, or neoprene to the ends of a concrete test cylinder so the load is distributed evenly during compression testing.

Maintaining adequate moisture and temperature in concrete after placement so cement hydration can continue and the concrete can develop its intended strength and durability.

Voids or cavities left in concrete where mortar has not filled the spaces between coarse aggregate particles, usually resulting from inadequate consolidation, blocked placement, or segregation.

The temporary molds, supports, and bracing that hold fresh concrete in the required shape and position until it hardens enough to stand on its own.

A coating applied to form surfaces to prevent hardened concrete from bonding to the forms and to ease stripping without damaging the concrete surface.

A tension member, often with cones or washers, that holds opposing form faces at the correct spacing against the pressure of fresh concrete and is later removed or cut back.

A plane of weakness formed where fresh concrete is placed against concrete that has already stiffened or set, preventing a proper bond between the two layers.

A planned stopping place in a concrete placement where fresh concrete is later placed against hardened concrete, typically prepared and bonded to create a continuous structural element.

A formed or sawed groove that creates a deliberate plane of weakness so drying shrinkage cracking occurs in a controlled location rather than randomly across the slab surface.

A groove cut or formed in a slab or wall to regulate where shrinkage or movement cracks will occur, keeping them straight and narrow rather than random.

The distance from the outer surface of concrete to the nearest surface of embedded reinforcement. Adequate cover protects steel from corrosion and provides fire resistance.

Steel bars, welded wire, fibers, or prestressing strands placed in concrete to resist tensile and shear forces that plain concrete cannot carry.

A connection made by overlapping the ends of two reinforcing bars so that forces transfer from one bar to the other through the surrounding concrete over the specified overlap length.

A device such as a chair, bolster, or dobie that holds reinforcement at the specified position and maintains the required concrete cover during placement and consolidation.

A review performed before concrete is placed to verify forms, reinforcement, embedded items, subgrade, and cleanliness are correct and ready, so defects are caught before they are buried.

The proportioning of cement, water, aggregates, and admixtures to achieve specified fresh and hardened properties at the lowest reasonable cost for the intended application.

A test mixture produced to verify that a proposed mix design meets requirements for consistency, air content, strength, and other properties before it is used in production.

The mass of concrete per unit volume, commonly determined by weighing a filled standard measure. It is used to compute yield and to check air content by the gravimetric method.

The volume of concrete actually produced per batch compared with the volume the mix design was intended to produce; a low yield often signals errors in batching or excess air.

The time required for fresh concrete to reach initial and final set, as measured by penetration resistance; it affects finishing, joint timing, and admixture performance.

The required rate at which field samples of concrete are taken for strength or other testing, commonly based on volume placed, area of slab, or number of truckloads.

A portion of fresh concrete taken from a delivery or placement and used to mold test specimens or perform acceptance tests representing that concrete.

Testing performed to determine whether concrete or construction complies with the specification, usually involving strength, air content, slump, or dimensional checks compared with limits.

A documented condition in which work, materials, or test results fail to meet a specified requirement, triggering review, reporting, and corrective action.

Extracting a cylindrical sample of hardened concrete from a structure, typically to verify in-place strength or to investigate suspected defects.