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Concrete Testing


Quiz Questions

1.One of the key requirements for any kind of repair system is to have adequate ___________ between the existing concrete substrate and overlay throughout the service life.
bond strength
concrete material
2. When a repair is performed, the differences _____________ of two materials will affect bond strength and stress distribution.
In the texture
In the properties
3. Which one the following would affect the bond between the two material.
Difference in shrinkage
Elastic modulus
Thermal movement
All of the above
4. Which one of the following would be considered as a three phase composite repair system.
Substrate
Overlay
Bond zone
All of the above
5.Failure modes are either
in tension or in shear
in compression or torsion
6. "Pull off test" is the most popular test due to its
Simplicity and accuracy
Low price and availability
7.

Which one of the followings is the objective of this study and course.

The importance of bond strength in concrete repair projects
Various factors influencing interlayer bond strength at the interface of the concrete repairs
Various test methods to determine the bond strength
Discussions and comparison of test methods
All of the above
8. The old way of thinking was to remove the concrete and replace it in case of damages such as cracks, surface discoloration or imperfections.
True
False
9.Hairline cracks, cracks in sidewalks, holes in concrete walls or even small broken corners do not need large scale maintenance. In these cases simple tools and materials are employed as following:

  1. cleaning the area, using detergent in case the area is oily
  2. widening and enlargement the cracks by hammer or cold chisel (the crack must be wider at the bottom than at the top, this is called undercutting)
  3. Removing all loose material and brushing the area
  4. Moistening the area and waiting for evaporation of surface water
  5. using some resins or adhesive and then grouting a Portland cement mortar (all the patch must be filled once)
  6. smoothing and leveling the surface with trowel
  7. curing for some days
True
False
10.Which one of the following could be cause for concrete damage?
Excess concrete water mix
Faulty design or construction defects
Alkali Silica Reactivity (ASR)
Deterioration through carbonation
Corrosion of reinforcing steel
Deterioration caused by cycle freezing and thawing
Abrasion-erosion damage
Structural overload
All of the above
11.Shotcrete is a process where concrete is projected or "shot" under pressure using a feeder or "gun" onto a surface to form structural shapes including walls, floors, and roofs.
True
False
12.The surface of shotcrete can be concrete, ______, polystyrene, or any other surface that concrete can be projected onto.
Concert
Rock
Steel
All of the above
13.Which one the followings is considered basic type of shotcrete
Dry-mix
Wet-mix
Both of the above
14.

Shotcrete has a wide range of usages; casting new structures, swimming pools, sculpting waterscapes, lining tunnels and ditches, paving slopes and complex shapes such as skateboard parks and earth retaining structures, strengthening and repairing existing structures of all types, providing fireproofing and chemical protection to steel, and construction of tanks, basement walls (underground parking facilities) and any other place that cannot be formed and poured.

True
False
15.Figure 2.3 is:
Drilling a hole in salt mine cave
Shotcrete application in lining of a tunnel
16.After repairing the concrete structure and replacing a new layer, there should be enough strength in both layers since the damaged part of substrate has been already removed and the new layer has been designed and placed according to the requirements of the work. Despite having adequate strength in both layers, the interface is still vulnerable to damages and could be the most sensitive part of the system.
True
False
17.Two layers have different modulus of elasticity, so exposed to the same load each shows different strains. The interface should be
able to bear this difference
Stronger material
18.The bond strength is the adhesion between overlay and substrate which can be ________of the system. Good bond strength is a key factor to have a monolithic system
The weakest link
The strongest link
19.Bond can be expressed by
shear resistance or
tensile resistance
Both of the above
20.In figure 3.1, Test B is
Failure in Substrate
Bond failure
Failure in overlay