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: cleaning the area, using detergent in case the area is oily 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) Removing all loose material and brushing the area Moistening the area and waiting for evaporation of surface water using some resins or adhesive and then grouting a Portland cement mortar (all the patch must be filled once) smoothing and leveling the surface with trowel 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