Arizona CR-9 Concrete Practice Exam

Free Arizona CR-9 Concrete Practice Sample Questions & Answers

Question 1. Reinforcing Steel Placement

During preparation for a reinforced concrete footing, the reinforcing bars are positioned directly against the soil rather than being supported at the required elevation. What is the primary concern with this installation?

A. The concrete will become too fluid during placement.

B. The reinforcement may not have adequate concrete cover.

C. The concrete will cure too quickly.

D. The footing will automatically require additional expansion joints.

Correct Answer. B

Explanation:
Reinforcing steel must be positioned so that the finished concrete provides the required cover around the reinforcement. When reinforcing bars are placed directly against soil, they may end up too close to the exposed surface of the concrete. Insufficient cover can reduce protection of the steel from moisture and environmental exposure and may affect the intended structural performance of the reinforced concrete member. Reinforcement should be supported using appropriate chairs, supports, or other approved methods so it remains in its specified position during concrete placement. Simply placing reinforcing steel on the ground and pouring concrete over it does not ensure that the required cover will be maintained.

Question 2. Concrete Placement

A crew is placing concrete for a slab. The concrete begins to stiffen before the entire placement area has been completed. A worker suggests adding water directly to the concrete truck to make the mixture easier to place. What should be considered before doing so?

A. Adding water can change the designed water-cement ratio and affect concrete properties.

B. Adding unlimited water is acceptable as long as the concrete remains gray.

C. Water should always be added whenever concrete becomes difficult to finish.

D. Adding water increases concrete strength after curing.

Correct Answer. A

Explanation:
Adding water to concrete can change the mixture’s designed water-cement ratio and may negatively affect important properties such as strength, durability, shrinkage, and finishing characteristics. Concrete should be produced and placed according to the specified mixture requirements rather than having uncontrolled water added at the jobsite. If adjustments are permitted, they should be made in accordance with the applicable specifications and established procedures. A concrete crew should also consider whether delays, placement conditions, temperature, or other factors are affecting workability. Making an uncontrolled water addition simply because the concrete has become harder to place can compromise the intended performance of the finished concrete.

Question 3. Concrete Curing

A contractor completes placement of a large concrete slab and wants to minimize premature moisture loss during the early curing period. Which practice best addresses this concern?

A. Allow the surface to dry immediately after finishing.

B. Protect the concrete from excessive moisture loss using an appropriate curing method.

C. Remove all coverings immediately after finishing.

D. Increase the amount of reinforcing steel after the concrete has hardened.

Correct Answer. B

Explanation:
Proper curing helps concrete develop its intended properties by maintaining suitable moisture and temperature conditions during the early stages after placement. Excessive moisture loss from freshly placed concrete can contribute to surface drying, shrinkage, cracking, and reduced performance. Appropriate curing methods may include water curing, curing compounds, or other methods permitted by the project specifications and applicable requirements. The selected method should be compatible with the concrete surface, subsequent construction activities, and project requirements. Simply allowing a newly finished slab to dry without protection does not provide the controlled conditions needed for proper curing and can negatively affect the quality of the finished concrete.

Question 4. Concrete Formwork

A concrete wall is scheduled for placement, and the contractor notices that one section of the formwork is not adequately supported. What should happen before concrete is placed?

A. Place the concrete quickly so the forms have less time to move.

B. Add concrete until the forms become stable.

C. Correct and adequately support the formwork before placement begins.

D. Remove the reinforcement to reduce pressure on the forms.

Correct Answer. C

Explanation:
Formwork must be properly designed, assembled, aligned, supported, and capable of resisting the pressures generated during concrete placement. Fresh concrete exerts significant lateral pressure on vertical forms, particularly when placement is rapid or the concrete remains highly fluid. If a section of formwork is inadequately supported, placing concrete before correcting the problem can result in movement, bulging, leakage, dimensional problems, or even form failure. The appropriate approach is to stop and correct the deficient support before placement. Reinforcing steel does not substitute for properly designed formwork, and increasing the speed of placement does not make an unstable form safer.

Question 5. Concrete Construction Joint

A slab placement must stop before the planned area is completed because of an unexpected equipment problem. The crew cannot resume placement until later. What is an important consideration when dealing with the resulting interruption?

A. The interruption has no effect because all concrete placements automatically bond together.

B. The location and treatment of the resulting construction joint should be addressed according to the project requirements.

C. The unfinished concrete should always be covered with loose soil.

D. The reinforcement should be removed from the slab.

Correct Answer. B

Explanation:
An unplanned interruption in concrete placement can create a construction joint, and the joint must be handled appropriately to maintain the intended performance of the concrete element. Its location, preparation, reinforcement continuity, surface condition, and method of resuming placement should follow the applicable drawings, specifications, and construction requirements. A construction joint should not simply be treated as an ordinary stopping point without considering its effect on the completed structure. Depending on the application, the existing concrete surface may require appropriate preparation before new concrete is placed. Proper planning and treatment of construction joints help maintain structural and serviceability requirements.

Question 6. Slab Subgrade Preparation

Before placing a concrete slab-on-grade, a contractor discovers that portions of the prepared subgrade are soft and unstable. What is the most appropriate response?

A. Place additional concrete over the soft areas without correction.

B. Identify and correct the unsuitable subgrade before concrete placement.

C. Add water to the concrete to compensate for subgrade movement.

D. Reduce the slab thickness over the unstable areas.

Correct Answer. B

Explanation:
A slab-on-grade depends on suitable and properly prepared supporting material. Soft or unstable areas can result in differential support, settlement, cracking, and other problems after the concrete has been placed. The contractor should identify the cause and correct the deficient areas in accordance with the project requirements before placing concrete. Depending on the conditions, corrective work may involve removing unsuitable material, replacing it with appropriate material, and properly preparing and compacting the supporting layer. Simply placing additional concrete over a weak area does not correct the underlying support problem. Proper subgrade preparation is an important part of producing a durable slab.

Question 7. Concrete Consolidation

During placement of a heavily reinforced concrete member, workers notice voids forming around the reinforcement because the concrete is not fully consolidating. Which method is generally used to help eliminate entrapped air and ensure the concrete properly surrounds the reinforcement?

A. Mechanical vibration or another approved consolidation method

B. Adding dry cement to the surface

C. Removing the reinforcing steel during placement

D. Spraying the concrete surface with water

Correct Answer. A

Explanation:
Concrete must be properly consolidated so that it fills the forms and surrounds reinforcing steel without leaving significant voids or honeycombing. Mechanical vibration is commonly used to consolidate concrete, particularly in reinforced members and areas where reinforcement or form geometry makes placement difficult. The vibrator should be used properly and in accordance with the applicable placement procedures because improper vibration can also create problems. Adding dry cement to the surface or spraying water onto the concrete does not consolidate concrete within the form. Reinforcement should remain in its specified position throughout placement, while the concrete is worked into the required areas using appropriate placement and consolidation techniques.

Question 8. Concrete Finishing

A crew is finishing an exterior concrete slab, but water has accumulated on the surface shortly after placement. A worker proposes finishing the slab immediately to force the water back into the concrete. What is the primary concern with this approach?

A. Premature finishing while bleed water is present can adversely affect the surface.

B. Finishing concrete is never permitted on exterior slabs.

C. Bleed water always increases concrete strength.

D. Finishing immediately eliminates the need for curing.

Correct Answer. A

Explanation:
Concrete finishing operations should be performed at the appropriate stage of the placement process. Working the surface while bleed water is present can disturb the surface layer and may contribute to undesirable conditions such as reduced durability, scaling, dusting, or other surface defects. The crew should follow the applicable finishing procedure and allow the concrete to reach the appropriate stage before performing the operation. Finishing practices also need to be coordinated with the specified surface texture and project requirements. Proper finishing does not eliminate the need for curing. Curing remains an important step in protecting the concrete and supporting the development of its intended properties.

Question 9. Concrete Temperature

A contractor schedules a concrete placement during unusually hot weather. The project team is concerned that high temperatures may affect the concrete before and during placement. Which issue deserves particular attention?

A. Increased evaporation and accelerated setting can affect workability and finishing.

B. Hot weather automatically eliminates the need for curing.

C. High temperatures guarantee higher concrete strength.

D. Concrete should always be mixed with unlimited additional water in hot weather.

Correct Answer. A

Explanation:
Hot weather can create challenging concrete placement conditions because elevated temperatures, low humidity, and wind can increase evaporation from fresh concrete. Concrete may also lose workability more rapidly and experience accelerated setting, reducing the available time for transportation, placement, consolidation, and finishing. Contractors should plan placements carefully and follow the project’s approved procedures for hot-weather concrete. Appropriate measures may involve controlling concrete temperature, scheduling placement during more favorable conditions, protecting materials, and managing curing and moisture loss. Simply adding uncontrolled water is not an appropriate universal solution because it can alter the mixture proportions and affect the finished concrete’s strength and durability.

Question 10. Concrete Quantity Calculation

A rectangular slab is 30 feet long, 20 feet wide, and 4 inches thick. Ignoring waste, approximately how many cubic yards of concrete are required?

A. 5.93 cubic yards

B. 6.17 cubic yards

C. 7.41 cubic yards

D. 8.33 cubic yards

Correct Answer. C

Explanation:
First convert the slab thickness from inches to feet. Four inches equals 4 ÷ 12, or approximately 0.333 feet. The slab volume is therefore 30 feet × 20 feet × 0.333 feet, which equals approximately 200 cubic feet. Because concrete is commonly ordered in cubic yards, divide the cubic-foot volume by 27, the number of cubic feet in one cubic yard. The calculation is approximately 200 ÷ 27 = 7.41 cubic yards. In an actual project, additional concrete would normally be considered for waste, irregularities, and placement conditions.