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Glossary of Terms

The following glossary of terms mainly intended for landscape architects, developers and other professional builders.

For the "Do-It-Yourselfer", please call the St. Vrain Block staff (303.833.4144) for any questions or further explanation you may need. Or, contact us online with your project questions. We always welcome the opportunity to be of service!

Abrasion: The mechanical wearing, grinding, scraping or rubbing away (or down) of paver surface by friction or impact, or both.

Absorption: Weight of water incorporated by a concrete paver unit during immersion under prescribed conditions, typically expressed as a percentage relating to the dry weight of the unit.

Aggregate: Sand, gravel, shell, slag, or crushed stone used in base materials, mixed with cement to make concrete, or with asphalt.

Aspect Ratio: The overall length of a paver divided by its thickness.
Example: A 4 in. (100 mm) wide by 8 in. (200 mm) long by 31/8 in. (80 mm) thick paver has an aspect ratio of 2.5. Compare to Plan Ratio.

ASTM C 936: American Society for Testing and Materials, Standard Specification for Solid Concrete Interlocking Paving Units. This product standard defines dimensions, dimensional tolerances, maximum absorption, minimum compressive strength, maximum abrasion and freeze-thaw durability through various test methods.

Band Cutter: A plier-like tool designed to cut metal or plastic bands around cubes and bundles of paving units without injury.

Base or Base Course: A material of a designed thickness placed under the surface wearing course of paving units and bedding course. It is placed over a subbase or a subgrade to support the surface course and bedding. A base course can be compacted aggregate, cement or asphalt stabilized aggregate, asphalt or concrete.

Base Rake: A rake with a flat and toothed side to move and level aggregate base (similar in appearance to an asphalt lute). A base rake can be used to evenly spread joint sand on the surface of paving units for faster drying.

Bedding Sand or Bedding Course: A layer of coarse, washed sand screeded smooth for bedding the pavers. The sand can be natural or manufactured (crushed from larger rocks) and should conform to the grading requirements of ASTM C 33 or CSA A23.1 with limits on the percent passing the No. 200 (0.075 mm) sieve. A screeded sand layer is 1 to 11/2 in. (25 to 40 mm) thick.

Bentonite Clay: Clay with a high content of the mineral montmorillonite, usually characterized by high swelling on wetting that can be used to help seal paver joints.

Best Management Practice (BMP): A structural device or non-structural program designed to reduce storm water runoff and water pollution.

Blending Pavers: Mixing colored concrete pavers from three or four cubes to insure an even color distribution.

Cement, Portland: Hydraulic cement produced by pulverizing clinker consisting essentially of hydraulic calcium silicates, and usually containing one or more forms of calcium sulfate.

Chamfer: A 45° beveled edge around the top of a paver unit usually 1/16 to 1/4 in. (2-6 mm) wide. It allows water to drain from the surface, facilitates snow removal, helps prevent edge chipping, and delineates the individual paving units.

Clay: Fine-grained soil or the fine-grained portion of soil that can be made to exhibit plasticity (putty-like properties) within a range of water contents, and that exhibits considerable strength when air-dry. The term can designate soil particles finer than 0.002 mm (0.005 mm in some cases).

Coarse Aggregate: Aggregate predominantly retained on the U.S. Standard No. 4 (4.75 mm) sieve; or that portion of an aggregate retained on the No. 4 (4.75 mm) sieve.

Compaction: The process of inducing close packing of solid particles such as soil, sand, or aggregate.

Compressive Strength: The measured maximum resistance of a concrete paver to loading expressed as force per unit cross-sectional area such as pounds per square inch or newtons per square millimeter (mega pascals).

Concrete Block Pavement: A system of paving consisting of discrete, hand-sized paving units of either rectangular or dentated shapes, manufactured from concrete. Either type of shape is placed in an interlocking pattern, compacted into coarse bedding sand, the joints filled with sand and compacted again to start interlock. The paving units and bedding sand are placed over an unbound or bound aggregate layer. Also called interlocking concrete pavement.

Concrete Pavers: Concrete paving units, rectangular, square or dentated, capable of being placed with one hand into a laying pattern. The surface area is typically less than 100 in.2 (0.065 m2) and the overall length to thickness is 4 or less. Compare to Paving Slab.

Concrete Sand: Washed sand used in the manufacture of ready-mix concrete which conforms to the grading requirements of ASTM C 33 or CSA A23.1. See Bedding Sand.

Course: A row of pavers.

Creep: Slow lateral movement of pavers from horizontal forces such as braking tires. The movement is usually imperceptible except to observations over a long duration.

Crushed Stone: A product used for pavement bases made from mechanical crushing of rocks, boulders, or large cobblestones at a quarry. All faces of each aggregate have well defined edges resulting from the crushing operation.

Crusher Run: The total unscreened product of a stone crusher.

Density: The mass per unit volume.

Dry Mix Joint Sand Stabilizer: Joint sand treated with chemicals that when placed in contact with water, activates them to bind the sand particles together. This stabilizes the joint sand, reduces its permeability, sand loss and helps prevent weeds.

Edge Paver: A paving unit made with a straight, flush side, or cut straight for placement against an edge restraint.

Edge Restraint: A curb, edging, building or other stationary object that contains the sand and pavers so they do not spread and lose interlock. It can be exposed or hidden from view.

Efflorescence: A white deposit of calcium carbonate on concrete surfaces. It results from the reaction of calcium hydroxide with carbon dioxide from the air. The calcium hydroxide is a by product when cement hydrates. It is slightly soluble in water and migrates to the surface through capillary action. The calcium hydroxide remains on the surface, reacts with carbon dioxide, which forms calcium carbonate and water. This conversion, depending on weather conditions, will dissipate over time. Calcium carbonate is the most common type of efflorescence. The presence of efflorescence does not compromise the structural integrity and is not indicative of a flawed product.

Erosion: The process of wearing away soil by water, wind, ice and gravity; also the detachment and movement of soil particles by the same forces.

Exfiltration: The downward movement of water through an open-graded, crushed stone base into the soil beneath.

Failure: The point at which a pavement does not adequately service its intended use. For flexible pavements, rut depth is often a criterion for failure.

False Joints: Grooves on the surface of concrete pavers that appear as full joints between pavers that contribute to the installed joint pattern. False joints can enhance the appearance of the pattern and speed installation compared to placing separate (sub) units. Sometimes called dummy grooves.

Fines: Silt and clay particles in a soil, generally those smaller than the No. 200 or 0.075 mm sieves.

Fineness Modulus: A factor obtained by adding the total percentages by weight of an aggregate sample retained on each of a specified series of sieves, and dividing the sum by 100; in the United States the standard sieve sizes are No. 100 (0.150 mm), No. 50 (0.300 mm), No. 30 (0.600 mm), No. 16 (1.18 mm), No. 8 (2.36 mm) and No. 4 (4.75mm), and 3/8 in. (9.5 mm), 11/2 in. (37.5 mm), 3 in. (75mm), and 6 in. (150 mm).

Finished Grade: The final elevation of a soil, base, or pavement surface which is often indicated on construction drawings. Also Finish Elevation.

Freeze-Thaw Durability Testing: Tests in which pavers are exposed to cycles of freeze and thaw, partially or totally immersed in water, and with or without salt water.

Frost Action: Freezing and thawing of moisture in pavement materials and the resultant effects on them.

Frost Heave: The raising of a pavement surface due to the accumulation and expansion of ice in the underlying soil or rock.

Geogrids: Geogrids are two dimensional or three dimensional. The two dimensional type are flat and have small, square, rectangular or triangular shaped openings. The material is generally placed between the soil and the base to reduce rutting. Three dimensional geogrids are 4 to 8 in. (100 to 200 mm) high and provide stability under loads for cohesionless soils.

Geotextiles: Woven or non-woven fabrics made from plastic fibers used for separation, reinforcement, or drainage between pavement layers.

Gradation: Soil, sand or aggregate base distributed by mass in specified particle-size ranges. Gradation is typically expressed in percent of mass of sample passing a range of sieve sizes. See ASTM C 136.

Grade: (noun) The slope of finished surface of an excavated area, base, or pavement usually expressed in percent; (verb) to finish the surface of same by hand or with mechanized equipment.

Gravel: Rounded or semi-rounded particles of rock that will pass a 3 in. (75 mm) and be retained on a No. 4 (4.75 mm) U.S. standard sieve which naturally occurs in streambeds or riverbanks that have been smoothed by the action of water. A type of soil as defined by the Unified Soil Classification System having particle sizes ranging from the No. 4 (4. 75 mm) sieve size and larger.

Half Stone: A half of a paver.

Hard Edges: A field of pavers that is restrained against a visible edge restraint or curb, thus visually reinforcing the edge of pavement.

Herringbone Pattern: A pattern where joints are no longer than the length of 11/2 pavers. Herringbone patterns can be 45° or 90° depending on the orientation of the joints with respect to the direction of the traffic.

Hotspot: A land use that generates highly contaminated runoff with concentrations higher than those typical to storm water.

Human Scale: Using paver sizes, patterns, colors and textures next to large buildings or open areas with the intent of reducing the user perception of being overwhelmed by the large scale of these spaces.

Impervious Cover: Surfaces that do not allow rainfall to infiltrate into the soil such as pavements, roofs, sidewalks, driveways, etc.

Infiltration Rate: The rate at which water moves through a soil tested in the field. Measured in inches per hour or meters per second. See ASTM D 3385 and 5093 and compare to Permeability.

Interlock: Frictional forces between paving units that prevent them from rotating, or moving horizontally or vertically in relation to each other; also defined as the inability of a concrete paver to move independently of its neighbors. The friction forces enable load transfer among the paving units. The three kinds of load transfer are vertical interlock, horizontal interlock and rotational interlock.
--Vertical interlock is achieved by shear transfer of loads to surrounding units through sand in the joints.
--Horizontal interlock is primarily achieved through the use of laying patterns that disperse forces from braking and accelerating vehicles. The most effective laying patterns for maintaining horizontal interlock are herringbone patterns.
--Rotational interlock is maintained by the pavers being of sufficient thickness, placed closely together, and being restrained by a stationary edge such as a curb.

Interlocking Concrete Pavement: A system of paving consisting of discrete, hand-sized paving units with either rectangular or dentated shapes manufactured from concrete. Either type of shape is placed in an interlocking pattern, compacted into coarse bedding sand, the joints filled with sand and compacted again to start interlock. The paving units and bedding sand are placed over an unbound or bound aggregate layer. Also called concrete block pavement.

Joint: The space between concrete paving units typically filled with sand.

Joint Filling Sand: Sand used to fill spaces between concrete pavers.

Joint Sand Gap: The vertical distance between the bottom of the chamfer on a paver and the top of the sand in the joint.

Joint Sand Stabilizer: Liquid penetrating or dry mix applied or materials that provide early stabilization of joint sand, reduces its permeability, sand loss and helps prevent weeds. See Dry Mix Joint Sand Stabilizer and Liquid Penetrating Joint Sand Stabilizer.

Joint Sand: Sand swept into the openings between the pavers.

Joint or Joint Spacing: The distance between the sides of the pavers not including the spacers that is typically filled with joint sand.

Laying Pattern: The sequence of placing pavers where the installed units create a repetitive geometry. Laying patterns may be selected for their visual or structural benefits.

Lean Concrete: Concrete of low-cement content used as a structural base material or as flowable fill in utility trenches.

Life-cycle Cost Analysis: A method of calculating all costs anticipated over the life of the pavement including construction costs. Discounted cash-flow methods are generally used, typically with calculation of present worth and annualized cost. Factors that influence the results include the initial costs, assumptions about maintenance and periodic rehabilitation, pavement user and delay costs, salvage value, inflation, discount rate, and the analysis period. A sensitivity analysis is often performed to determine which variables have the most influence on costs.

Lift: A layer of spread or compacted soil fill or aggregate. The compacted soil depth achieved by compaction equipment.

Moisture Content: The percentage by weight of water contained in the pore space of soil, sand or base, with respect to the weight of the solid material.

Mortar: A mixture of cement paste and fine aggregate (sand).

Mortar Sand: Sand used in mortar that typically conforms to ASTM C 144 or CSA A179.

Mosaics: Pavers used as pictorial maps, murals, or geometric patterns as a landmark, to emphasize an area, or suggest movement.

Multi-Colored Paver (Color Blend): A paver with two or more colors. The appearance is usually variegated.

Optimum Moisture Content: The water content at which a soil can be compacted to a maximum dry unit weight by a given compactive effort.

Organic Impurities: Peat, roots, topsoil or decomposing materials in soil, sand or aggregate.

Organic Soil: Spongy, compressible soils usually consisting of peat humus or vegetative matter that have undesirable construction characteristics

Pavement Performance: The trend of serviceability under repetitive loads.

Pavement Rehabilitation: Work undertaken to extend the service life of an existing pavement. This includes placement of additional surfacing material and/or other work necessary to return an existing roadway to a condition of structural or functional adequacy. This could include the complete removal and replacement of the pavement structure.

Pavement Structure: A combination of subbase, base course, and surface course placed on a subgrade to support traffic loads and distribute it to the roadbed.

Paver Extractor: A tool used to grab a paver and remove it from the laying pattern.

Paving Slab (or Flag): A paving unit with a surface area over 100 in.2 (0.065 m2) and with maximum length and width dimensions of 48 in. by 48 in. (1.2 m x 1.2 m). Its overall length to thickness ratio is greater than 4. Paving slabs do not rely on interlock as the principal means of load distribution.

Paver Splitter: A hand operated machine, sometimes hydraulically assisted, for cutting concrete pavers; also called a guillotine splitter.

Peak Discharge Rate: The maximum instantaneous flow from a detention or retention pond, open-graded base, pavement surface, storm sewer, stream or river; usually related to a specific storm event.

Performance: The total number of vehicle or ESAL applications withstood by a pavement before it reaches failure, rehabilitation, or a lower level of serviceability.

Performance Period: The period of time that an initially constructed or rehabilitated pavement structure will last (perform) before reaching its terminal serviceability. This is also referred to as the design period or life, expressed in years. Twenty to forty years is normally used in North America.

Permeability: Measured in the laboratory, the rate of water movement through a soil column under saturated conditions, usually expressed as k in calculations per specific ASTM or AASHTO tests, and typically expressed in inches per hour or meters per second. See ASTM D 2434. Compare to Infiltration.

Permeable Interlocking Concrete Pavement: Concrete pavers with wide joints (5 mm to 10 mm) or a pattern that creates openings in which rainfall and runoff can infiltrate. The openings are typically filled with aggregate and occasionally with topsoil and grass. The pavers are typically placed on an open-graded aggregate base which filters, stores, infiltrates, and/or drains runoff.

Pervious or Permeable Surfaces/Cover: Surfaces that allow the infiltration of rainfall such as vegetated areas.

Plan Ratio: The overall length of a paver divided by its width. Compare to Aspect Ratio.

Plate Compactor: Also known as a plate vibrator, which is used to compact pavers into bedding sand in order to promote interlock among the individual units.

Porosity: The volume of voids in an open-graded base divided by the total volume of the base.

Pozzolanic Materials: Fly ash, pozzolan, silica fume, or blast furnace slag used as substitutes for cement. They are generally used in the concrete mix to increase density and durability of concrete pavers.

Prepared Roadbed: In-place roadbed soils compacted or stabilized according to provisions of applicable specifications.

Progressive Stiffening: The tendency of pavements to stiffen over time. Interlocking concrete pavement stiffens as it receives increasing traffic loads thereby offering increased structural contribution structure; also referred to as "lockup".

Pumping: The ejection of saturated bedding and joint sand, through joints or cracks or along edges of pavers when a load is applied.

Reflecting: Using pavers to mirror geometric patterns, shapes, colors or textures in the surrounding site.

Retention Pond: A body of water that collects runoff and stays full permanently. Runoff flowing into the body of water that exceeds its storage capacity is released into a storm sewer or watercourse.

Running Bond Course: A paver course or two where the paver lengths abut against the edge restraint. Also known as a "sailor course".

Running or Stretcher Bond: A laying pattern with continuous joint lines in one direction and four pavers are staggered from one row to the next.

Rutting: Permanent deformation from repetitive traffic loading that exceeds the ability of the pavement structure to maintain its original profile.

Sand: Granular material passing the 3/8 in. (5 mm) and retained on the No. 200 (0.075 mm) sieve, made from the natural erosion of rocks, and consisting of subangular or rounded particles. Sands made by crushing of coarse aggregates are called manufactured sands.

Sand Spreaders: Broomed attachments to motorized equipment used to efficiently spread joint sand across the surface of segmental concrete pavements.

Screed Board or Strike Board: A rigid, straight piece of wood or metal used to level bedding sand to proper grade by pulling across guides or rails set on the base course or edge restraints.

Screed Guides or Bars: Grade strips such as pipe that will guide the screed in producing the desired elevation of the bedding sand.

Screenings: A residual product not suitable for bedding sand. It is a by-product from the crushing of rock, boulders, cobble, gravel, blast-furnace slag or concrete. Most of the aggregate passes the No. 4 (4.75 mm) sieve; typically limestone or granite.

Sealer: A material usually applied as a liquid to waterproof, enhance color, and in some cases reduce abrasion of interlocking concrete pavements.

Sediment: Soils transported and deposited by water, wind, ice or gravity.

Segmental Pavement: A pavement whose surface consists of discrete units typically made of concrete, clay, or stone.

Shrinkage: The reduction in volume in soil when moisture content is reduced.

Silt: Soil finer than 0.02 mm and coarser than 0.002 mm (0.5 mm and 0.005 mm in some cases).

Skid Resistance: A measure of the frictional characteristics of a surface with respect to tires.

Slip Resistance: Resistance against pedestrian slipping; defined as the ratio of a minimum tangential force necessary to initiate sliding of a pedestrian's shoe or related device over a surface. Non-mobility impaired persons require minimum coefficient of friction values ranging from 0.2-0.3. Wheelchair users require friction values ranging from 0.5-0.7. Crutch users and those with artificial limbs require values from 0.7 to 1.0. Clean concrete pavers generally have values exceeding 0.7.

Soft Edges: A field of pavers with no visible edge restraint that meets grass or other vegetation, thus giving a soft appearance to the edge.

Soil Separation Fabric: A layer of fabric typically placed between the subgrade and the base to reduce rutting, also called a geotextile.

Soil Stabilization: Chemical or mechanical treatment designed to increase or maintain the stability of a mass of soil or otherwise to improve its engineering properties. Lime, fly ash or cement are typical chemical stabilization materials. Geotextiles and geogrids are typical mechanical materials for soil stabilization.

Soldier Course: A paver course where widths abut against the edge restraint.

Solid Color Paver: A paver with one color created by adding iron oxide, metal oxide, or other mixed metal oxide pigment to the concrete mix.

Spacer Bars, Spacers or Nibs: Small protrusions on each side of the paver (typically 1.5 to 2 mm) that maintain a minimum space so sand can fill into the joints. Spacer bars help prevent edge chipping and spalling. Some spacer bars stop short of the top surface, and are known as "blind spacers". They cannot be seen once the pavers have been installed.

Spall: A fragment, usually in the shape of a flake, detached from the edge or surface of a paver by a blow or sudden force, the action of weather, or pressure from adjacent pavers.

Stabilized Base: An aggregate base with cement, asphalt or other material added to increase its structural capacity. The soil subgrade can be stabilized with cement, lime, fly ash or other materials.

Stack Bond: A laying pattern in which the joints in both directions are continuous.

Standing Screed: Aluminum screed with handles allowing one person to pull it across bedding sand while standing (compared to kneeling while screeding).

Sub-base: The layer or layers of specified or selected material of designed thickness placed on a subgrade to support a base course. Aggregate sub-bases are typically made of stone pieces larger than that in bases.

Subgrade: The soil upon which the pavement structure and shoulders are constructed.

Sustainable Development: Development (including pavement) that meets the needs of the present without compromising the ability of future generations to meet their own needs.

Tactile Pavers: A paver detectable by sight impaired persons due to change in color or texture from surrounding surfaces. Changes in texture are achieved with detectable warnings.

Tensile Strength: Maximum unit stress which a paver is capable of resisting under axial tensile loading, based on the cross-sectional area of the specimen before loading.

Textured or Architectural Finish: Paver surfaces altered by the manufacturing mold or mechanical means, such as shot blasting, bush hammering, tumbling, grinding, polishing, flame treating, or washing. The purpose of such treatments is often to simulate the appearance of stone.

Topsoil: Surface soil, usually containing organic matter.

Water-Cement Ratio: The weight of water divided by the weight of cement in a concrete mixture. Concrete pavers typically have a water-cement ratio of 0.27 to 0.33, lower than ordinary concrete, which contributes to strength and durability.

The Reference Library

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Below are some of the most commonly requested documents, brochures and information. Let us know if you have a special request!

Product Brochures

We are continually updating our brochures, listed below. So contact us or check back often to see the latest!

Cuesta Brochure

Edging Brochure

Patio Stones Brochure

Paving Stones Brochure

Quarry Stone Brochure

Pyzique Brochure 1

Pyzique Brochure 2

Solar Ballast Block Brochure

Quantity Estimate

Each project has unique characteristics or challenges. Using your measurements, we will provide an estimate of product quantity necessary for your project. Call us at 303-833-4144 or contact us online with your request.

Installation Tips

We can recommend various Landscape Professionals or, if you are the 'Do-It-Yourself' type, we provide these helpful installation instructions.

~ more install tips coming soon