Civil Engineering

the contractual arrangement under which a firm supplies construction management services to an owner.

includes such activities as specification development, process control, product acceptance, laboratory and technician certification, training, and communication.

primarily concerned with the process control function.

the process of moving soil or rock from one location to another and processing it so that it meets construction requirements of location, elevation, density, moisture content, and so on.

the ability of a soil to support the weight of vehicles under repeated traffic.

a measure of the difficulty in excavating and loading soil.

the bucket volume contained within the bucket when following the outline of the bucket sides.

the bucket capacity when the load is struck off flush with the bucket sides.

assumes a level of material flush with the lowest edge of the bucket.

the maximum volume that can be placed in the bucket without spillage based on a specified angle of repose for the material in the bucket.

a very versatile machine that has the longest reach for digging and dumping of any member of the crane shovel family.

primarily used for lifting, lowering, and transporting loads. They move loads horizontally by swinging or traveling.

represents that component of vehicle weight which acts parallel to an inclined surface.

primarily due to tire flexing and penetration of the travel surface.

represents those components of cycle time other than travel time.

represents the travel time required for a unit to haul material to the unloading site and return.

the process of giving natural soils enough abrasive resistance and shear strength to accommodate traffic or design loads.

the process of increasing the density of a soil by mechanically forcing the soil particles closer together, thereby expelling air from the void spaces in the soil.

involves dropping a heavy weight from a crane onto the ground surface to achieve soil densification.

the process of densifying cohesionless soils by inserting a vibratory probe into the soil.

placing additional weight on the soil surface to densify cohesive soils.

the improvement of the engineering properties of a soil by use of physical or chemical admixtures.

the process of bringing earthwork to the desired shape and elevation (or grade).

involves smoothing slopes, shaping ditches, and bringing the earthwork to the elevation required by the plans and specification.

the process of cutting down high spots and filling in low spots of each roadway layer.

the process of bringing each roadway layer to its final grade.

may be considered in four phases

produced by mixing portland cement, aggregate, and water. The construction operations involved in the production of concrete include batching, mixing, transporting, placing, consolidating, finishing, and curing.

usually weighs from 140 to 160 lb/cu ft (2243–2563 kg/m3), depending on the mix design and type of aggregate used.

concrete that may weigh from 15 to 90 lb/cu ft (240–1442 kg/m3) and have a 28-day compressive strength from about 100 to 1000 lb/sq in. (690–6895 kPa).

concrete used in a structure such as a dam in which the weight of the concrete provides most of the strength of the structure.

concrete made with heavy aggregates such as barite, magnetite, and steel punching; it is used primarily for nuclear radiation shielding.

concrete having a slump of 1 in. (2.5 cm) or less.

a measure of concrete consistency obtained by placing concrete into a test cone following a standard test procedure (ASTM C143) and measuring the decrease in height (slump) of the sample when the cone is removed.

concrete that is suitable for high temperature applications such as boilers and furnaces.

concrete that has been cast into the desired shape prior to placement in a structure.

concrete that will be exposed to view and therefore utilizes special shapes, designs, or surface finishes to achieve the desired architectural effect.

a general-purpose cement, suitable for all normal applications.

provides better resistance to alkali attack and produces less heat of hydration than does Type I cement.

provides 190% of Type I strength after 1 day of curing. It also produces about 150% of the heat of hydration of normal cement during the first 7 days.

produces only 40–60% of the heat produced by Type I cement during the first 7 days. However, its strength is only 55% of that of normal cement after 7 days.

provides maximum resistance to alkali attack.

used in concrete to reduce the cost of the mix and to reduce shrinkage.

required in the concrete mix for several purposes. Principal among these is to provide the moisture required for hydration of the cement to take place.

the chemical reaction between cement and water which produces hardened cement. The heat that is produced by this reaction is referred to as heat of hydration.

normally used range from about 0.40 to 0.70 by weight.

has significantly increased resistance to freezing and thawing as well as to scaling caused using deicing chemicals.

increase the slump or workability of a concrete mix. Thus, with a water-reducing agent the amount of water in the mix may be reduced without changing the concrete’s consistency.

slow the rate of hardening of concrete.

act in the opposite manner to retarders. That is, they decrease setting time and increase the early strength of concrete.

used to reduce the heat of hydration, increase the workability, and reduce the segregation of a mix.

increase the workability of a mix.

the process of proportioning cement, water, aggregates, and additives prior to mixing concrete.

are truck-mounted concrete mixers capable of mixing and transporting concrete. The product they deliver is referred to as ready-mixed concrete.

consists of gravel, crushed stone, or another suitable material larger than ¼ in. (6.4 mm) in diameter.

are materials other than portland cement, aggregates, and water that are added to concrete either immediately before or during its mixing to alter the properties of the concrete in a variety of ways.

For example, they can be used to:

Improve workability

Reduce separation of coarse and fine aggregates due to settling out of the heavier coarse aggregate

Entrain air

Accelerate or retard setting and hardening

permit a lower water content, improve workability, and increase the efficiency of the portland cement in a mix, which lowers a concrete's cost relative to its performance.

are mostly used in concrete that is to be pumped. They produce a mix that flows easily, with no increase in its water content.

admixtures that have a retarding effect on the set of portland cement overcome the accelerating effect that temperature has on setting during hot weather and in large masses of concrete, and delay the early stiffening of concrete placed under difficult conditions.

increase the rate of early strength development in concrete.

Because concrete is unable to maintain a particular shape before it sets, it must be placed in a form or mold. In building construction, this form or mold is called formwork.

are made by building a large section of form, as described earlier for centering, and supporting the entire section on deep steel trusses.

is a method of continuously moving a form for vertical structures, such as elevator or stair shafts, upward on jacks as new concrete is placed on top of the old.

are rubber or vinyl inserts designed to be placed in concrete joints to prevent water from penetrating the joint.

are often necessary to separate concrete sections and prevent the bonding of one concrete section with another, or to separate a concrete section from another material or structural part so that one can move independently of the other.

is one that is readily molded and yet will change its form only slowly if the mold is removed.

Concrete is handled and transported by:

•        • Chutes

•        • Push buggies

•        • Buckets handled by cranes

•        • Pumping through a pipeline

•        • Pneumatically forcing through a hose (shotcrete)

is either delivered to the site by truck or, in small projects, mixed at the site and moved to its placement location by:

•        • Dumping directly from a truck's chute.

•        • Buggy.

•        • Dumping from a truck's chute into a large bucket, which is then lifted by crane and deposited in its proper location.

•        • Dumping from a truck into a concrete pump which delivers the mix to its final location through a hose. Pumps are capable of delivering concrete over long distances and up many floors.

is pneumatically placed concrete, used primarily for swimming pools and other in-ground and aboveground free-form structures and for repairing damaged concrete.

Concrete should be compacted by a method appropriate to the material and its location to:

•        • Eliminate stone pockets and large air bubbles

•        • Consolidate each layer with that previously placed

•        • Completely embed reinforcing and fixtures

•        • Bring just enough fine material to the faces and top surfaces to produce the desired finish

it should be compacted and worked into place by spading or puddling.

it proceeds through several steps in a defined order. These steps are screeding, leveling, edging, jointing, floating, troweling, and broom finishing or other surface texturing.

shortly after placement, the dry materials used in making quality concrete tend to settle to the bottom and displace the mixing water to the surface, which is called bleeding.

the surface of newly placed concrete is struck off (screeded) by moving a straightedge back and forth with a sawlike motion across the top of the forms and screeds.

it is the bringing of a concrete surface to true grade with enough mortar to produce the desired finish.

it rounds off the formed edge of a slab to prevent chipping or damage.

immediately following or during edging, premolded inserts are placed in concrete slabs to control cracking in the concrete as a result of shrinkage, except when joints will be later sawed.

It may be done when the water sheen has disappeared and the concrete will support the weight of the finisher.

The purpose of floating is to:

•        • Embed large aggregate just beneath the surface

•        • Remove slight imperfections, humps, and voids to produce a level or plane surface

•        • Consolidate mortar at the surface in preparation for other finishing operations

•        • Open the surface to permit excess moisture to escape

the process of finishing concrete slabs that are to be left exposed or to receive thin finishes, such as resilient flooring, carpet, tile, or paint.

a method of roughening a smooth, steel-troweled concrete surface to produce a nonslip surface by brushing or brooming it.

the breaking away of the hardened concrete surface of a slab to a depth of about 1/6 to 3/16 in. (1.6 to 4.8 mm), usually occurring at an early age of the slab.

the occurrence of numerous fine hair cracks in the surface of a newly hardened slab due to surface shrinkage.

the appearance of a powdery material on the surface of a newly hardened concrete slab.

asphalt often based on a polymer-modified asphalt (PMA), available and demonstrating high resistance to rutting and cracking as well as to petroleum fuels.

a liquid mixture created when petroleum distillates are mixed with asphalt cement, which is liquid at room temperature.

a mixture of asphalt dispersed in water by means of emulsifying agents.

the temperature at which a liquid produces sufficient vapor to ignite in the presence of air and an open flame.

a machine capable of spreading, consolidating, and finishing a concrete slab without the use of conventional forms.

a thin coating of light bituminous material applied to a previously paved surface to act as a bonding agent.

a substance applied to an unpaved surface to reduce the amount of dust produced by vehicular traffic and wind.

a light application of a slow-setting asphalt emulsion diluted by one to three parts of water.

a mixture of slow-setting asphalt emulsion, fine aggregate, mineral filler, and water.

a light application of a medium-viscosity liquid asphalt covered with fine aggregates.

alternate applications of asphalt and aggregate used for aggregate surface treatments.

a construction method that involves spraying on a layer of asphalt and covering it with a layer of aggregate approximately one stone in depth.

the process of demolishing old pavement, recrushing the pavement material, and reusing it in new asphalt or concrete mixes.

the part of a structure that supports the weight of the structure and its applied loads.

the simplest and most common type of building foundation, including individual footings, combined footings, and mat foundations.

a heavily reinforced concrete slab extending under the entire structure, used to spread the structure’s load over a large area.

a type of mat foundation in which the weight of the soil excavated approximately equals the weight of the structure being erected.

the process of improving soils in place.

a column driven into the soil to support a structure by transferring building loads to a deeper and stronger layer of soil or rock.