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ACI CTCI practice questions

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Question 1Concrete Construction Inspection

Before placing concrete, the forms and reinforcement should be inspected primarily to confirm that they are free of what condition that would prevent proper bonding or embedment?

  1. Form release agent
  2. Vapor barriers
  3. Construction joints
  4. Standing water, ice, and loose debris Correct answer.

Explanation

Concrete placed against standing water or ice becomes diluted at the interface and cannot develop a proper bond, and debris blocks paste from contacting forms and steel. Release agent is intentional and vapor barriers are part of the design, so they are not defects. The pre-placement inspection confirms clean, sound contact surfaces.

Question 2Concrete Construction Inspection

A slump test is being performed per ASTM C143. At what point should the slump be measured after the cone is lifted?

  1. After the concrete has fully stabilized, measured to the nearest 1/4 in. Correct answer.
  2. Immediately as the cone clears the concrete
  3. After 5 minutes of settling time
  4. Only after tapping the concrete with a mallet

Explanation

The slump is measured after the concrete comes to rest following removal of the cone, recorded to the nearest 1/4 in. Measuring while the mass is still moving gives a false reading. Tapping or waiting arbitrary times is not part of the procedure.

Question 3Concrete Construction Inspection

For a standard 6 by 12 in. concrete cylinder, the specimen is filled and rodded in layers. How many layers and strokes per layer are specified?

  1. Two layers, 25 strokes each
  2. Two layers, 50 strokes each
  3. Three layers, 35 strokes each
  4. Three layers, 25 strokes each Correct answer.

Explanation

Standard 6 by 12 in. cylinders are rodded in three approximately equal layers with 25 strokes per layer using the specified tamping rod. This ensures uniform consolidation without overworking. Smaller 4 by 8 in. molds use a different layer/stroke schedule.

Question 4Concrete Construction Inspection

The primary purpose of curing is to maintain what condition in the concrete?

  1. Zero shrinkage strain
  2. A uniform surface color
  3. Adequate moisture and temperature for hydration Correct answer.
  4. A constant compressive stress

Explanation

Curing preserves moisture and favorable temperature so cement continues to hydrate and strength and durability develop. It does not impose stress or guarantee zero shrinkage. Surface appearance is not the objective.

Question 5Concrete Construction Inspection

During concrete placement, the inspector observes the crew allowing concrete to fall freely from a considerable height. This practice should be stopped because it causes what?

  1. Increased air content
  2. Faster set time
  3. Segregation of coarse aggregate from mortar Correct answer.
  4. Reduced form pressure

Explanation

Free fall over a large drop lets heavier aggregate separate from the paste, producing segregation and honeycomb. Concrete should be placed as near its final position as practical using chutes or drop pipes. Air content and setting behavior are not the concern here.

Question 6Concrete Construction Inspection

Which of the following is the standard method of consolidating concrete in heavily reinforced walls?

  1. Surface tamping
  2. Hand rodding only
  3. Internal vibration with a properly sized vibrator Correct answer.
  4. Troweling each lift

Explanation

Internal vibration with a vibrator sized to the section and reinforcement spacing is the standard means of consolidating structural concrete. Hand rodding is inadequate for heavily reinforced sections. Troweling and surface tamping do not consolidate the interior.

Question 7Concrete Construction Inspection

A vibrator should be inserted into a concrete lift and withdrawn how?

  1. Rapidly, to avoid over-vibration
  2. Slowly, at a rate that lets the hole close behind the head Correct answer.
  3. Only after the surface bleeds
  4. At an angle to reach corners

Explanation

Slow withdrawal allows the concrete to flow and close the hole, avoiding voids and ensuring the surrounding mass is consolidated. Rapid withdrawal leaves voids. Waiting for bleed water is not part of the procedure.

Question 8Concrete Construction Inspection

What does the abbreviation w/cm represent in concrete mixture terminology?

  1. Water-to-cementitious-materials ratio by mass Correct answer.
  2. Working crack magnitude
  3. Wet cure method
  4. Weight of coarse material

Explanation

w/cm is the mass ratio of water to cementitious materials (cement plus supplementary materials such as fly ash or slag). It is a primary determinant of strength, permeability, and durability. The other terms are unrelated to this ratio.

Question 9Concrete Construction Inspection

A slump test yields a value that exceeds the maximum permitted for the specified class. What is the appropriate inspector action?

  1. Approve the load if the concrete looks workable
  2. Reject the load or require corrective action per the specification Correct answer.
  3. Add water to make it consistent with the class
  4. Add cement at the job site to stiffen the mix

Explanation

Slump outside the specification limit means the load does not conform and should be rejected or handled per the project's procedures. Adding cement or water at the site alters the approved mixture and is not permitted. Visual judgment does not override the specification.

Question 10Concrete Construction Inspection

An inspector takes a set of cylinders. After casting, the specimens must be stored initially in what manner before transport to the laboratory?

  1. In direct sunlight to accelerate curing
  2. In a protected environment at specified temperature, kept moist Correct answer.
  3. In a freezer to halt hydration
  4. Dry, to prevent excess surface water

Explanation

Initial curing requires protection from the elements and maintaining the specimens at the specified temperature while keeping them moist. Sun, freezing, or drying all distort strength results. Proper initial curing ensures the test reflects the concrete as placed.

Question 11Concrete Construction Inspection

The inspector suspects a cylinder broke low because of a testing error rather than low concrete strength. Which observation most likely indicates a testing problem rather than a materials problem?

  1. The specimen was capped with a soft, uneven material Correct answer.
  2. The fracture plane is diagonal across the full height
  3. Fracture pattern shows a clear cone on one end and a relatively flat break on the other
  4. The break is through the coarse aggregate with a uniform appearance

Explanation

Poor or uneven capping introduces stress concentrations and produces misleadingly low strengths. A proper break typically shows the characteristic cone-and-split pattern through the paste and aggregate. Uneven caps or misalignment are testing defects, not concrete defects.

Question 12Concrete Construction Inspection

During hot-weather concreting, the inspector should be most concerned about which combination of effects?

  1. Accelerated set, increased water demand, and greater risk of plastic shrinkage cracking Correct answer.
  2. Reduced water demand and slower evaporation
  3. Retarded set and increased entrained air
  4. Increased strength gain and reduced bleeding

Explanation

High temperature accelerates hydration and evaporation, raising water demand and the risk of plastic shrinkage cracks. These effects must be managed through cooling, scheduling, and curing. The other combinations describe cooler-weather behavior.

Question 13Concrete Construction Inspection

Which action best protects fresh concrete placed in cold weather from early freezing?

  1. Adding extra water to generate heat
  2. Removing insulation immediately after finishing
  3. Leaving the surface exposed to ambient air
  4. Maintaining the concrete temperature above the specified minimum until it gains sufficient strength Correct answer.

Explanation

Fresh concrete must be protected and kept above the specified minimum temperature until it has gained enough strength to resist freeze damage. Extra water lowers strength and increases the risk. Exposed or uninsulated surfaces lose heat rapidly.

Question 14Concrete Construction Inspection

A construction joint is planned in a wall. What is the most important preparation of the existing hardened concrete surface before placing new concrete?

  1. Coat it with a heavy layer of form oil
  2. Clean it and roughen it to promote bond Correct answer.
  3. Wet it and leave standing water
  4. Seal it completely to prevent moisture loss

Explanation

Construction joints require a clean, roughened, and properly prepared surface so the new concrete bonds to the old. Standing water dilutes the interface and oil prevents bond. Sealing defeats the purpose of joining.

Question 15Concrete Construction Inspection

The inspector must verify that reinforcement has the specified concrete cover. What is the primary purpose of adequate cover?

  1. To increase the slump of the concrete
  2. To protect the steel from corrosion and provide fire resistance Correct answer.
  3. To reduce the amount of steel required
  4. To allow easier form stripping

Explanation

Cover protects reinforcement from moisture and chlorides that cause corrosion and provides fire resistance to the member. It does not reduce steel area or affect slump. Easy stripping is unrelated to cover.

Question 16Concrete Construction Inspection

An inspector observes that reinforcing bars are supported on metal chairs but several bars are resting directly on the subgrade. What is the consequence if this is not corrected before placement?

  1. Improved consolidation around the bars
  2. Increased effective depth of the slab
  3. Reduced cover and potential corrosion or bond loss Correct answer.
  4. Higher slump in the concrete

Explanation

Bars on the subgrade lose the specified bottom cover, exposing steel to moisture and reducing bond with concrete. Supports should maintain the design position. Effective depth and slump are not improved by this condition.

Question 17Concrete Construction Inspection

What is the purpose of a slump test on fresh concrete?

  1. To determine air content
  2. To assess consistency and workability Correct answer.
  3. To measure setting time
  4. To measure compressive strength directly

Explanation

The slump test indicates the consistency and workability of fresh concrete. It does not measure strength, air content, or setting time directly. Those properties require other tests.

Question 18Concrete Construction Inspection

For a standard slump test, the cone is filled in layers and each layer is rodded. Which description matches the standard procedure?

  1. Two layers, each rodded 10 times
  2. Three layers, each rodded 50 times
  3. Three layers, each rodded 25 times Correct answer.
  4. One layer, rodded throughout

Explanation

The standard slump cone is filled in three layers, each rodded 25 times with the tamping rod, and the top is struck off. This provides uniform compaction for a representative reading. Other layer/stroke combinations do not match the procedure.

Question 19Concrete Construction Inspection

Which of the following would most likely be classified as a defect requiring correction when observed during a pre-placement inspection?

  1. Formwork with gaps that will allow mortar leakage Correct answer.
  2. Reinforcement tied securely at intersections
  3. Vapor barrier properly lapped and sealed
  4. Formwork coated with an approved release agent

Explanation

Gaps in formwork allow mortar to leak, causing honeycomb and loss of paste, and must be sealed before placement. Release agent, secure tying, and a properly installed vapor barrier are correct conditions. The inspection exists to catch deficiencies like form gaps.

Question 20Concrete Construction Inspection

An inspector notes that a concrete truck has been on site for an extended period and the concrete is being placed beyond the specified time limit after batching. What is the correct action?

  1. Reject the concrete that exceeds the time limit Correct answer.
  2. Add water to restore workability
  3. Allow placement if the slump is acceptable
  4. Add retarder at the job site

Explanation

Concrete placed beyond the specified time after batching may have reduced workability and strength and should be rejected per the specification. Slump alone does not authorize acceptance, and field additions of water or admixtures are not permitted without approval.

Question 21Concrete Construction Inspection

An inspector observes surface bleeding on a freshly placed slab. How should the finishing operation be scheduled relative to the bleed water?

  1. Add water to the surface to keep it workable
  2. Finish immediately while water is present
  3. Finish only after the concrete has fully hardened
  4. Wait until bleed water has dissipated or been removed before finishing Correct answer.

Explanation

Finishing while bleed water is present traps water beneath the surface, raising the w/cm at the top and causing weak, dusty, or cracked surfaces. Finishing should proceed after bleed water dissipates or is removed. Adding water worsens the problem.

Question 22Concrete Construction Inspection

A set of cylinders is to be tested for acceptance. How many specimens typically make up a strength test result, and at what age is the standard acceptance test performed?

  1. Three cylinders tested at 28 days Correct answer.
  2. Two cylinders tested at 7 days
  3. Four cylinders tested at 14 days
  4. One cylinder tested at 28 days

Explanation

A strength test result is generally the average of at least two cylinders, commonly three, tested at 28 days for acceptance. Seven-day tests are used for early information, not final acceptance. A single cylinder is not a valid test result.

Question 23Concrete Construction Inspection

Cylinders from a placement break below the specified strength at 28 days. Before concluding the in-place concrete is deficient, the inspector should first consider which factor?

  1. The color of the concrete surface
  2. The brand of the cement used
  3. The number of trucks delivered
  4. Whether the specimens were properly sampled, cured, and tested Correct answer.

Explanation

Low breaks can result from sampling, initial curing, capping, or testing errors, so these must be evaluated before judging the structure. Surface color, cement brand, and truck count do not determine cylinder validity. If specimens are valid, further investigation of the in-place concrete is warranted.

Question 24Concrete Construction Inspection

The specification requires a minimum concrete temperature at placement. During cold weather, the inspector measures the temperature of the concrete in the form. Which measurement location and method are appropriate?

  1. Within the concrete mass, using a suitable thermometer left in place long enough to register Correct answer.
  2. On the outside of the form
  3. After the concrete has hardened
  4. At the surface of the fresh concrete with an infrared gun only

Explanation

Concrete temperature should be measured within the mass using a thermometer that is left in place long enough to reach equilibrium, because surface readings are not representative. Infrared surface readings and form-surface readings do not reflect the interior. Measuring after hardening is too late to control placement.

Question 25Concrete Construction Inspection

An inspector is evaluating whether a proposed curing method is adequate for a structural slab. Which consideration is most directly relevant to the adequacy of the method?

  1. Whether it maintains moisture and temperature for the specified curing period Correct answer.
  2. Whether it allows earlier form removal
  3. Whether it reduces the number of workers needed
  4. Whether it improves the surface color

Explanation

Curing adequacy depends on maintaining moisture and temperature for the required duration so hydration continues. Surface color, labor, and form-removal timing are not measures of curing effectiveness. The method must keep the concrete from drying prematurely.

Question 26Concrete Construction Inspection

Before any concrete is placed against a form, the inspector should verify that the form surfaces have been treated with a release agent primarily to do what?

  1. Seal the form joints against grout loss
  2. Accelerate the initial set of the concrete
  3. Prevent the hardened concrete from bonding to the formwork Correct answer.
  4. Increase the compressive strength of the concrete at the surface

Explanation

A form release agent creates a barrier so the hardened concrete does not adhere to the form, allowing clean stripping and protecting the surface finish. It does not act as a joint sealant, a set accelerator, or a strength modifier.

Question 27Concrete Construction Inspection

An inspector observes that the specified concrete cover over reinforcement in a slab-on-grade is being achieved by resting the bar mat on the vapor retarder without supports. What is the correct inspection action?

  1. Require the bars to be raised and supported on chairs or bar supports at the specified elevation Correct answer.
  2. Require only the top layer to be supported, since the bottom layer is in compression
  3. Accept the placement because the vapor retarder provides continuous support
  4. Accept the placement if the bars are tied together at intersections

Explanation

Reinforcement must be held at the position shown on the drawings by suitable bar supports so that the specified cover is maintained on all faces. Resting bars on the vapor retarder leaves them at the wrong elevation and provides no controlled cover. Tying does not establish elevation.

Question 28Concrete Construction Inspection

Which document governs the acceptance criteria the inspector applies when evaluating a completed concrete placement?

  1. The contractor's internal quality manual
  2. The project specifications and referenced standards Correct answer.
  3. The concrete supplier's batch ticket only
  4. The inspector's prior experience on similar projects

Explanation

Inspection acceptance is measured against the project specifications and the standards they reference, which define tolerances, test methods, and acceptance limits. Other documents may be informative but do not establish the contractual acceptance criteria.

Question 29Concrete Construction Inspection

During placement, the inspector notes that concrete is being dropped from a considerable height into a deep form. What is the primary concern with this practice?

  1. Premature setting of the cement paste
  2. Increased form pressure beyond design values
  3. Reduction of the concrete's air content to zero
  4. Segregation of coarse aggregate from the mortar Correct answer.

Explanation

Free-falling concrete over a large height allows heavy aggregate to separate from the mortar, causing segregation and honeycomb. Placement should use drop chutes or tremies to keep the free fall within accepted limits.

Question 30Concrete Construction Inspection

Which of the following best describes the purpose of a pre-placement inspection meeting between the inspector and the contractor?

  1. To determine the number of test cylinders required by the code
  2. To confirm that forms, reinforcement, and embedded items are ready and to resolve issues before concrete arrives Correct answer.
  3. To establish the concrete mixture proportions for the project
  4. To set the price of concrete for the placement

Explanation

A pre-placement meeting coordinates readiness so that deficiencies in formwork, reinforcement, and embeddings are corrected before the pour begins. Mixture design, testing frequency, and pricing are established elsewhere.

Question 31Concrete Construction Inspection

An inspector finds that expansion joint filler material has been installed with gaps between adjacent pieces. Why should this be corrected before concrete placement?

  1. The gap will cause the concrete to cure unevenly
  2. Incompressible material can enter the gaps and prevent the joint from closing Correct answer.
  3. The filler will absorb mix water and lower the w/cm ratio
  4. The gap reduces the required concrete cover to reinforcement

Explanation

Joint filler must form a continuous, tight barrier; otherwise concrete or debris can fill the gap and block the intended movement, defeating the joint. Continuity of the filler is essential to the joint's function.

Question 32Concrete Construction Inspection

What is the primary function of dowels placed across a contraction joint in a pavement?

  1. To bond the two slabs rigidly into a single structural unit
  2. To anchor the joint filler in place
  3. To transfer load between adjacent slabs while allowing longitudinal movement Correct answer.
  4. To resist the tensile stress from shrinkage in the slab

Explanation

Dowel bars transfer vertical load across a joint while permitting the slabs to move relative to one another, reducing faulting and cracking. They are not intended to rigidly bond the slabs together.

Question 33Concrete Construction Inspection

Which condition indicates that a curing compound has been applied at an adequate coverage rate?

  1. The compound pools in low spots and runs off high spots
  2. A uniform, continuous film covers the concrete surface Correct answer.
  3. The surface appears dry and chalky immediately after spraying
  4. The surface remains glossy and wet for hours after application

Explanation

Curing compound must form a uniform, continuous membrane to limit moisture loss. Patchy, dry, or heavily pooled application indicates uneven coverage that leaves areas unprotected.

Question 34Concrete Construction Inspection

An inspector notices that a wall form has deflected noticeably under the pressure of freshly placed concrete. What is the most appropriate immediate action?

  1. Continue placement but reduce the slump of subsequent loads
  2. Continue placement and evaluate the wall after stripping
  3. Stop placement and require the form to be braced or corrected before continuing Correct answer.
  4. Continue placement and note the deflection in the daily report

Explanation

Formwork must remain within the specified tolerances during placement; excessive deflection indicates inadequate bracing and can produce out-of-tolerance or defective concrete. Placement should be halted and the form corrected before work resumes.

Question 35Concrete Construction Inspection

An inspector observes that reinforcing bars have been bent in the field at a radius tighter than the standard bend diameter. Why is this a concern?

  1. Tight bends prevent the bar from being tied to the mat
  2. Tight bends can crack or overstress the bar and reduce its capacity Correct answer.
  3. Tight bends increase the bar's yield strength beyond specification
  4. Tight bends reduce the concrete cover over the bar

Explanation

Standard bend diameters exist to limit the strain on the outside of the bend and avoid cracking or fracture of the bar. Field bending tighter than the required diameter can damage the bar and compromise its structural contribution.

Question 36Concrete Construction Inspection

During inspection of a beam, the inspector finds that the stirrups are spaced farther apart than shown on the drawings. What is the correct interpretation?

  1. The spacing can be increased if a higher-strength concrete is used
  2. The spacing is acceptable if the longitudinal steel is in place
  3. The placement is nonconforming and must be corrected to the specified spacing Correct answer.
  4. The spacing is acceptable because stirrups are secondary reinforcement

Explanation

Stirrup spacing is a design requirement that controls shear capacity and confinement; deviation from the drawings is a nonconformance. The spacing must be corrected unless a change is approved by the designer.

Question 37Concrete Construction Inspection

An inspector is reviewing a method statement for placing concrete in a deep beam with congested reinforcement. Which approach best reduces the risk of voids?

  1. Place in layers and consolidate each layer with a properly sized vibrator Correct answer.
  2. Place the full depth in one continuous drop from the top
  3. Reduce the water content to stiffen the mixture
  4. Increase the coarse aggregate size to improve flow

Explanation

Layered placement with systematic consolidation allows entrapped air to escape and concrete to fill around congestion. A single deep drop and stiffer mixtures increase the likelihood of honeycomb.

Question 38Concrete Construction Inspection

What should the inspector verify about embedded items such as conduits and sleeves before concrete placement?

  1. That they are removed before the concrete sets
  2. That they are made of the same material as the reinforcement
  3. That they are filled with concrete to prevent crushing
  4. That they are securely fastened, correctly located, and do not compromise required cover Correct answer.

Explanation

Embedded items must be fixed in the correct position and must not reduce the cover or section in a way that affects durability or strength. Loose or misplaced embeddings displace during placement.

Question 39Concrete Construction Inspection

An inspector observes that a construction joint in a slab has been formed but the surface of the previously placed concrete was not roughened. What is the likely consequence?

  1. Increased shrinkage cracking in the new concrete
  2. Reduced bond across the joint, creating a weak plane Correct answer.
  3. Higher form pressure during the next placement
  4. Increased bleeding at the joint face

Explanation

Construction joints rely on a clean, roughened, and moistened surface to develop bond between old and new concrete. A smooth untreated surface acts as a weak interface that can open or slip.

Question 40Concrete Construction Inspection

An inspector sees that the concrete delivered has a lower slump than the approved mixture design and the contractor wants to add water at the truck. What is the appropriate response?

  1. Permit the addition if the slump is brought within the specified range
  2. Do not permit water addition beyond the limits established for the approved mixture Correct answer.
  3. Permit the addition if the truck has been on site for less than 30 minutes
  4. Permit the addition only if a retarder is also added

Explanation

Water may only be added within the limits set for the approved mixture and with the inspector's knowledge; uncontrolled water addition raises the w/cm ratio and lowers strength and durability. Bringing slump into range by adding water alone is not acceptable.

Question 41Concrete Construction Inspection

During a placement, the inspector notes that the concrete temperature is being measured at the point of discharge. Why is this location appropriate?

  1. It reflects the temperature of the concrete as placed in the work Correct answer.
  2. It measures the temperature of the mixing water
  3. It is the only location where a thermometer can be inserted
  4. It measures the ambient air temperature affecting the concrete

Explanation

Placement temperature is the temperature of the concrete when it is deposited in the forms, so measuring at discharge reflects the condition being accepted. It is not a measure of air or mixing water temperature.

Question 42Concrete Construction Inspection

An inspector observes that the top surface of a freshly placed slab is being finished while bleed water is still visible. What is the most likely result?

  1. A reduction in the slab's drying shrinkage
  2. Improved bond between the slab and the base
  3. An increase in the slab's compressive strength
  4. A weak, dusty surface layer prone to scaling Correct answer.

Explanation

Finishing while bleed water is present works water into the surface, raising the local w/cm ratio and producing a weak, dusty layer that can scale or craze. Finishing should be delayed until bleed water has evaporated or been removed.

Question 43Concrete Construction Inspection

Which observation during a pre-placement check of reinforcement should be reported as a nonconformance?

  1. Bars cleaned of loose mill scale before placement
  2. Chairs spaced closely under the top mat
  3. Tie wire ends bent away from exposed surfaces
  4. Lap lengths that are shorter than those shown on the drawings Correct answer.

Explanation

Lap length is a design requirement that develops the bar force; a short lap reduces capacity and is a nonconformance. The other observations describe correct practice.

Question 44Concrete Construction Inspection

An inspector finds that the concrete in a formed wall shows honeycombing after form removal. Which factor is most directly indicated by honeycombing?

  1. Inadequate consolidation or mortar loss during placement Correct answer.
  2. Insufficient form release agent
  3. Excessive curing time after placement
  4. An overly high ambient humidity during curing

Explanation

Honeycombing appears where mortar has not filled the spaces between coarse aggregate, typically from inadequate vibration or grout leakage. It is a placement and consolidation issue rather than a curing issue.

Question 45Concrete Construction Inspection

An inspector is asked to verify that a proposed curing method will be adequate for a structural slab in dry, windy conditions. Which factor is most important in the evaluation?

  1. The color of the curing material applied
  2. The method's ability to retain moisture in the concrete for the required curing period Correct answer.
  3. The speed with which the curing material can be removed
  4. The cost of the curing method relative to alternatives

Explanation

Curing adequacy is judged by how well the method maintains moisture and temperature in the concrete for the specified duration, especially under drying conditions. Color, cost, and removal speed are secondary.

Question 46Concrete Construction Inspection

During inspection of a footing, the inspector observes standing water in the excavation at the time of placement. What is the appropriate action?

  1. Permit placement and note the condition in the report
  2. Permit placement if the concrete is placed through the water
  3. Permit placement if the concrete slump is increased
  4. Require the water to be removed before concrete is placed Correct answer.

Explanation

Concrete should not be placed in standing water unless a specifically approved method is used, because water dilutes the mixture and washes cement. Removing the water before placement protects the concrete's quality.

Question 47Concrete Construction Inspection

An inspector is evaluating a proposed repair for a spalled area on a wall. Which condition must the repair method satisfy?

  1. It must use the same mixture as the original concrete
  2. It must restore the section and provide durable bond with the existing concrete Correct answer.
  3. It must be applied within one hour of mixing
  4. It must match the color of the surrounding concrete exactly

Explanation

A repair must restore structural section and develop a durable bond to the substrate, using a method and material suited to the condition. Color matching and using the original mixture are not the governing criteria.

Question 48Concrete Construction Inspection

An inspector observes that a concrete placement is proceeding in layers that have begun to set before the next layer is placed. What is the principal concern?

  1. The concrete temperature will rise above the specified limit
  2. The form pressure will exceed design values
  3. The air content will increase in the upper layer
  4. A cold joint may form, reducing continuity between layers Correct answer.

Explanation

If a layer sets before the next is placed, the layers do not integrate and a cold joint forms, creating a plane of weakness. Placement should be sequenced so successive layers are placed while the previous layer is still plastic.

Question 49Concrete Construction Inspection

An inspector notes that a contractor intends to strip the side forms from a wall early to reuse them, while the concrete is still gaining strength. Which condition governs whether early stripping is acceptable?

  1. The forms must have been in place for a fixed minimum of 24 hours
  2. The concrete must have gained sufficient strength to resist damage from stripping and subsequent loads Correct answer.
  3. The concrete must have reached its 28-day design strength
  4. The ambient temperature must be above 10 degrees Celsius

Explanation

Formwork may be removed when the concrete can safely carry the loads and resist damage from stripping, which depends on the actual strength achieved rather than a fixed time. Reaching full 28-day strength is not required for side forms.

Question 50Concrete Construction Inspection

An inspector finds that the specified number of bar supports has been reduced in a heavily loaded elevated slab to speed placement. What is the most significant risk?

  1. The formwork may fail under the weight of the concrete
  2. The slab may develop excessive bleeding at the surface
  3. The concrete may cure too rapidly at the top surface
  4. The top reinforcement may deflect downward during placement, reducing the effective depth Correct answer.

Explanation

Insufficient bar supports allow workers and equipment to push the top mat down, reducing the effective depth and the slab's flexural capacity. Bar support spacing is a structural control, not a convenience.