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86問 • 3ヶ月前

Sabrina Mikhaela Canindo

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The behavior of concrete pavement that is expose to loading and environmental effect entirely depends upon the:

Quality of Concrete, Underlying Sub-Grade, Base Course

strong in resisting compression load acting on it, but considerably weak in resisting tensile stress.

Concrete

expand and contract due to temperature changes. It expands when wet and contracts when dried.

Concrete

is very likely due to the effect of daily and seasonal temperature and moisture differences between the top and bottom of slab.

Curl Tendency

With reinforcement, cracks on the slab will be confined to a weekend plain joints spaced at __ meters distance.

4.5 to 6

With simply reinforced slab, cracks will only appear at weakened plane joints spaced at __ meters interval.

12 to 20

is supported by foundation that deflects when loaded but recover when the load is removed, assuming that the foundation materials are elastic or like a dense liquid.

Pavement Slab

is due to stress brought about by 1 rad, moisture and temperature.

Deterioration of Concrete Pavement

Distress of concrete is generally grouped into the following categories:

Distortion, Cracking, Disintegration

is a vertical displacement of concrete slab at the joint of the cracks.

Distortion

is due to failure or weakness of concrete joints.

Distortion

is the result of pumping tremendous force or load that developed under the pavement.

Faulting

Causes of faulting:

Loss of Slab Support, Erosion of Sub Base

can take many forms in concrete pavement that could be the result from; applied load, temperature or moisture changes.

Cracking

The most common type of cracks:

Corner Cracks, Transverse Cracks

associated with excessive corner deflection.

Corner Cracks

associated with mixture or temperature stress, or poor construction methods.

Transverse Cracks

appears in the form of durability cracking, scaling or spalling, as the result of mix design or construction related problems.

Disintegration

result from freeze-thaw action.

Durability Cracking

a network of shallow fine hairline cracks which extend through the upper surface of the concrete.

Scaling

is the result from deicing salts, improper construction, freeze-thaw cycle, or steel reinforcement too closed to the surface.

Scaling

is the breaking or chipping of the joint edges.

Spalling

is the result from excessive stresses at joint, weak concrete, poorly designed or constructed joints

Spalling

create slab curling, flexure stresses and overall lengthening and shortening of the slabs.

Changes in Temperature and Moisture Content

is due to temperature drop or dying that create tensile stresses.

Tendency of the Slab to Shorten

is due to temperature rise or increased in moisture that creates compression stresses.

Tendency to Lengthen

provide space allowance for the lengthening of slab due to expansion.

Expansion Joints

are provided between adjacent traffic lanes.

Longitudinal Joints

is considered as hinges to provide edge support, but allows rotation between the slabs.

Longitudinal Joints

If concrete pouring will be interrupted for quite some time that cold joint will be inevitable, the practice is to provide a _.

Construction Joint

should be cleaned and sealed to prevent infiltration of water to the sub-grade and to keep dirt out of the joints.

Construction Joints and Cracks

is specified in the design to prevent the widening of cracks produced by shrinkage or thermal contraction.

Steel reinforcement for concrete pavement joints

are mounted in one layer along the mid-depth of the slab.

Reinforcing Steel Bars

The formula used in designing this reinforcement for concrete slab joint is

As = LfW/2S

are also used as reinforcements for concrete pavement made from cold drawn steel wired.

Wielded Fabrics

Minimum allowed tensile strength

80,000 psi

Yield Strength

70,000 psi

Reinforcing bars of billet, rail or axle steel yield strength among the from

40,000 to 75,000 psi

defined as the layer of material that lies immediately below the concrete pavement.

Sub-Base

the ejection of water and sub-grade soil through the joints and cracks along the edges of the concrete pavement.

Pumping

A substance added in mixing to change the characteristic of concrete mixture.

Admixture

the entrapment of air in the concrete mixture in the form of evenly distributed small bubbles.

Air Entrainment

It is used to increase the concrete resistance to surface scaling caused by increase the concrete resistance to surface scaling caused by deicing with calcium or sodium chloride.

Air Entrainment

The effectiveness of air entrainment is to increase the concrete durability that is influenced by:

Percentage of air present in the mixture. , Grading of aggregates. , Size and distribution of air bubbles.

The strength and other desirable properties of concrete mixture varies depending upon the _.

Cement and Water Ratio

A non-air-entrained concrete with a water cement ratio by weight of __ gallons of water per bag of cement may have a compressive strength of about __ in 28 days.

5, 5,300 psi

A mixture of concrete with __ gallons of water per bag of cement has developed strength of __ only for 28 days.

7, 3.700 psi

is dependent on the water-cement ratio that should be properly controlled to obtain the richness of the paste.

Durability

AASHTO Guide specification for highway construction established the max. water cement ratio at __ gallons per bag of cement on normal conditions and __ gallons per bag of cement fir severe atmospheric conditions.

6, 5½

The objective in _ is to use more aggregates and as a little cement as possible, while maintaining the workability necessary for a successful pouring and consolidation.

Concrete Mixture

is the old traditional and most widely used method in determining the consistency of concrete.

Slump Test

a metal cylinder 15 cm diameter and 12 cm high with hemisphere bottom shaped weighing 14 kg.

Kelly Ball Method

a graduated handle rising from the top of the ball passes through a metal frame that is 30 cm apart. The ball is placed on the surface of the fresh concrete. Its penetration is measure by comparing its position with that of the frame.

Kelly Ball Method

Newly placed concrete pavement needs _.

Curing

The shortest period of curing for normal concrete is _ according to AASHTO recommendation.

5 Days

is categorized under item __ of DPWH standard specifications, which provides that: “This item shall consist of Portland cement Concrete pavement with or without reinforcement, constructed on the prepared base in accordance with the plans and specifications. “

Concrete Pavement, 311

shall conform to the applicable requirements of Item 0-700, hydraulic cement.

Portland Cement

to be used in concrete mixing or curing or other designated applications should be clean and free from oil, salt, acid, alkali, grass or other substances injurious to the finished product.

Water

The specifications state that: dowels and tie bars to be used in concrete pavement shall conform to the requirements of AASHTO M-31 or M-42 except that rail steel shall not be used for tie bars to be bended and re-straightened during construction.

Reinforcing Steel

shall be deformed bars.

Tie Bars

shall be plain round bars delivered to the site with one half of each dowel length painted with one coat of approved lead or tar paint.

Dowels

shall be metal of approved design to cover 50mm plus or minus 5mm of the dowels, with a closed end, with a suitable stop to hold the end of the sleeve at least 25mm from the end of the dowel.

Sleeves of Dowels

shall be of such design that they do not collapse during construction.

Sleeve

should be mixed asphalt and mineral or rubber filler.

Joint Fillers

should be waterproof with raised floor from the ground to protect the cement from rain or dampness.

Storage of Cement and Aggregate

ACI

American Concrete Institution

in general, the DPWH specifications provides that: “The contractor shall be responsible for the quality control of all materials during the handling, blending, mixing and placement operations

Quality Control of Concrete

The person performing the batching of mixing operation, capable of accurately conducting aggregate surface moisture determinations and establishing correct scale weight for concrete materials.

Concrete Butcher

The person responsible for concrete production control and sampling and testing for quality control proficient in concrete technology having a sound knowledge of the specifications as they relate to concrete production.

Concrete Technician

After the base or sub-grade have been placed and compacted to the required density, the areas that will support the paving machine and the grade on which the pavement is to be constructed should be trimmed to the proper elevation by means of a properly designed machine extending the work at least 60 cm beyond each edge of the proposed concrete pavement.

Preparation of Grade

The foundation under the forms should be hard and true to grade, so that the form when set will be firmly in contact with its whole length at the specified grade.

Base Support

form shall be set sufficiently advance from the point where the concrete is being placed.

Grading and Alignment

should be checked and corrections be made immediately before the placing of concrete.

Grading and Alignment

No concrete should be mixed, placed or finished, when natural light is insufficient, unless an adequate and approved artificial lighting system is operated.

Limitation of Mixing

are constructed according to the type, dimensions and at the locations as indicated on plans or special provisions.

Concrete Joints

Concrete Pavement Joints are classified into:

Longitudinal Joint, Transverse Joint, Transverse Contraction Joint, Longitudinal Contraction Joint, Load Transfer Device

Classification of Transverse Contraction Joint:

Transverse Strip Contraction Joint, Formed Groove, Sawed Contraction Joint

is installing as parting strip to be left in place as specified.

Transverse Strip Contraction Joint

is installed by depressing an approved tool or device into the plastic concrete.

Formed Groove

is made by sawing groove in the surface of the pavement.

Sawed Contraction Joint

is provided along the longitudinal centerline of the pavement either by tongue and groove concrete or by steel dowels.

Load Transfer Device

Forms for concrete pavement should remain in place undisturbed within 24 hours after pouring.

Removal of Forms

are used in removing forms, pulling out nails and pins but care should be exercised not to break the pavement edges.

Crowbars

Concrete pavement and its appurtenances should be protected against public traffic, and traffic caused by the workers.

Protection of Pavement

includes the posting of watchmen to direct traffic and the posting and maintenance of warning signs, lights, pavement bridges or crossovers, etc.

Protection of Pavement

workable concrete having a slump of between __ if not vibrated, or between __ if vibrated and flexural strength of not less than __ when tested by the third-point method or __ when tested by the mid-point method or a compressive strength of __ when tested at fourteen days.

40 and 70 mm (11/2" to 3"), 10 to 40 mm, 3.8 Mpa (550 psi), 4.5 Mpa (650 psi) , 24.1 Mpa (3,500 psi)

Weekly Test 1

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Weekly Test 1