CEM 200 KEY TERMS

PCC

Portland Cement Concrete; a concrete mixture made from portland cement, water, fine aggregate, coarse aggregate, and sometimes admixtures.

PC

Portland Cement; the gray powder binder used in PCC.

Cement

A binding material that reacts with water and hardens. In this class, cement usually means portland cement.

Concrete

Cement paste plus fine aggregate plus coarse aggregate.

Cement Paste

Portland cement mixed with water; the binder portion of concrete.

Mortar

Cement paste plus fine aggregate, usually sand.

Grout

A fluid cementitious mixture made with cement paste, fine aggregate or no fine aggregate, small coarse aggregate when needed, and more water.

Binder

The part of the mix that holds materials together; in PCC, the binder is cement paste.

Filler

The solid material that occupies volume in concrete; aggregates act as fillers.

Fine Aggregate (FA)

Sand-sized aggregate used in mortar and concrete.

Coarse Aggregate (CA)

Larger aggregate such as gravel or crushed stone used in concrete.

Admixture

A material added to concrete besides cement, water, and aggregates to change fresh or hardened properties.

Hydraulic Cement

Cement that hardens by reacting with water.

Hydration

The reaction of portland cement with water that forms new compounds and causes hardening and strength gain.

Curing

Maintaining moisture and proper conditions so hydration can continue and concrete can gain strength.

Drying

Loss of moisture from concrete; drying is not the same as curing and does not create strength.

Water/Cement Ratio (w/c)

The weight of water divided by the weight of cement in a mix.

Workability

The ease with which fresh concrete can be mixed, placed, consolidated, and finished.

Consistency

The fluidity or wetness of fresh concrete.

Cohesiveness

The ability of fresh concrete to stay together without separating.

Slump Test

A test used to measure the consistency and workability of fresh concrete.

True Slump

A slump condition where the concrete subsides evenly and remains generally intact.

Shear Slump

A slump condition where part of the concrete mass slides or shears sideways.

Collapsed Slump

A slump condition where the concrete collapses, usually because the mix is too wet or unstable.

Zero Slump

A very stiff concrete condition where little or no settlement occurs after the slump cone is removed.

Segregation

Separation of coarse aggregate from the paste or mortar in fresh concrete.

Bleeding

The upward movement of excess water to the surface of freshly placed concrete.

Entrapped Air

Unintended air voids trapped in concrete during mixing and placement.

Air-Entrained Concrete

Concrete with intentionally added microscopic air bubbles to improve freeze-thaw durability and workability.

Compressive Strength

The ability of hardened concrete to resist crushing loads.

f′c

The specified compressive strength of concrete, usually measured at 28 days.

28-Day Strength

The standard concrete strength age used for many ASTM tests and design requirements.

ASTM C39

The standard test method for compressive strength of concrete cylinders.

Splitting Tensile Strength

A test used to estimate concrete tensile strength, usually about one-tenth of compressive strength.

Flexure

Bending action in a structural member such as a beam or slab.

Shear

A force action where one part of a member tends to slide past another part.

Torsion

Twisting action in a structural member.

Elasticity

The ability of a material to return to its original shape after load is removed.

Modulus of Elasticity

A measure of stiffness; it relates stress to strain within the elastic range.

Stress

Internal force per unit area within a material.

Strain

Deformation of a material caused by stress.

Type I Cement

General-purpose portland cement.

Type II Cement

Portland cement with moderate sulfate resistance.

Type III Cement

Portland cement that provides high early strength and high heat of hydration.

Type IV Cement

Portland cement with low heat of hydration.

Type V Cement

Portland cement with high resistance to severe sulfate action.

Type I/II Cement

The portland cement type used in the course labs.

Heat of Hydration

Heat released during the cement-water hydration reaction.

Cement Fineness

The particle size condition of cement; finer cement has more surface area for hydration.

Soundness

The ability of hardened cement paste to maintain volume stability after setting.

Setting Time

The time required for cement paste to begin and complete stiffening.

C₃S

Tricalcium silicate; a portland cement compound that provides high early strength and high heat of hydration.

C₂S

Dicalcium silicate; a portland cement compound that hydrates slowly and provides later strength.

C₃A

Tricalcium aluminate; a cement compound that reacts quickly, gives fast early behavior, releases high heat, and reduces sulfate resistance.

C₄AF

Tetracalcium aluminoferrite; a cement compound that contributes little strength but helps reduce clinkering temperature.

Cleanness

The absence of harmful substances such as clay, silt, and organics in aggregate.

Gradation

The distribution of different aggregate particle sizes.

Sieve Analysis

A test used to determine aggregate gradation by separating particles through stacked sieves.

Pan

The bottom container in a sieve analysis that catches material passing all sieves.

Fineness Modulus (FM)

A numerical index of aggregate fineness or coarseness, usually applied to fine aggregate.

Particle Shape

The form of aggregate particles, such as rounded, angular, flat, or elongated.

Texture

The surface condition of aggregate particles, such as smooth or rough.

Specific Gravity (SG)

The ratio of a material’s density to the density of water.

Unit Weight

Weight per unit volume, commonly expressed in pounds per cubic foot.

Absorption

The amount of water an aggregate can take into its pores.

Moisture Content (MC)

The amount of water present in or on aggregate at the time of mixing.

Oven-Dry Aggregate

Aggregate with no moisture; it can absorb water from the concrete mix.

Air-Dry Aggregate

Aggregate with some moisture but still able to absorb water from the mix.

SSD Aggregate

Saturated Surface Dry aggregate; pores are full of water but the surface is dry, so it neither adds nor takes water from the mix.

Damp or Wet Aggregate

Aggregate with surface moisture greater than SSD; it can add water to the mix.

Maximum Size of Aggregate (MSA)

The largest aggregate size selected for a concrete mix.

Dry-Rodded Unit Weight

The compacted unit weight of coarse aggregate used in ACI mix design calculations.

ACI

American Concrete Institute; organization that provides concrete standards, guides, and design methods.

ACI Mix Design

A method used to proportion PCC ingredients for required workability, strength, durability, and exposure.

Free Mixing Water

The amount of water selected for the mix before correcting for aggregate moisture.

Cement Content

The amount of cement required in the mix, often found from water requirement divided by w/c requirement.

Moisture Correction

Adjustment of batch water and aggregate weights based on field aggregate moisture.

Accelerator

An admixture that speeds setting or early strength gain.

Retarder

An admixture that slows setting and extends workability.

Water Reducer

An admixture that lowers water demand while improving workability.

Air-Entraining Agent (AEA)

An admixture that intentionally adds small air bubbles to concrete.

Rebar

Steel reinforcement placed in concrete to resist tension, flexure, and cracking.

Plain Rebar

Smooth reinforcing bar, often used where sliding is needed.

Deformed Rebar

Reinforcing bar with ribs or ridges that improve bond with concrete.

Mesh / WWR / WWM

Welded wire reinforcement or welded wire mesh used as reinforcement in concrete.

Yield Strength

The stress level at which steel begins to permanently deform.

Rebar Identification Marks

Marks on rebar showing production mill, bar size, steel type, and yield strength.

ASTM

ASTM International, formerly the American Society for Testing and Materials; develops material and testing standards.

Vicat Apparatus

A device used to test normal consistency and setting characteristics of portland cement.

PPE

Personal Protective Equipment, such as goggles, gloves, aprons, and proper footwear.

Machine Guarding

Protective barriers or devices that prevent contact with dangerous moving parts.

Emergency Response

Required action during a lab emergency, including calling for help, evacuation, eyewash, shower, or fire response.

Eyewash Station

Emergency equipment used to flush chemicals from the eyes for at least 15 minutes.

St. Francis Dam Failure

A 1928 dam failure discussed in class; the course identifies the primary cause as poor engineering and misunderstood geology leading to undercutting.

Efflorescence

A white surface deposit caused when moisture carries soluble salts to the concrete surface and the salts crystallize.