30 Questions
In reinforced concrete designs, what is the Poisson effect?
A phenomenon that must be accounted for in arch dams, tunnels, and some statically indeterminate structures
How does the Poisson's ratio relate to spiral reinforcing in columns?
It is utilized to take advantage of concrete's properties in columns
Why is it necessary to use more water than required for cement hydration in concrete mixtures?
To achieve the desired workability for placing concrete
What happens to the excess mixing water used in concrete after curing?
It evaporates, leading to shrinkage and cracking
Which type of structures require consideration of the Poisson effect in their analysis and design?
Arch dams and tunnels
What is the main purpose of the paste consisting of cement and water in concrete mixtures?
To bond the aggregate materials together
What are dead loads in a structure?
Loads of constant magnitude that remain in one position
Which of the following is NOT considered a dead load in a reinforced concrete building?
Furniture
How are estimated weights of structure parts used in the design process?
For use in structural analysis and design
Why is it important to have reasonable estimates of structure weights during design?
To ensure the safety and stability of the structure
How can an experienced designer estimate weights of most structures accurately?
By referring to similar structures or civil engineering handbooks
What role do tables in civil engineering handbooks play in estimating structure weights?
To provide approximate weights for common building materials
What is the purpose of chemically modifying the surface characteristics of fibers used in concrete?
To increase bonding with the cement paste
What aspect of fibers is crucial for determining the improvement in concrete toughness?
Length
Which ASTM standard is used for determining the toughness of fiber-reinforced concrete?
ASTM C101820
How do fibers contribute to the toughness of concrete when a crack opens up in a member?
Provide resistance to crack opening
What effect do fibers have on the fatigue life of beams in concrete structures?
Increase fatigue life
Why does the use of fibers significantly increase costs in construction projects?
Because fibers are expensive materials
What is the purpose of retarding admixtures in concrete?
To slow down the setting of concrete
Why are superplasticizers used in concrete?
To reduce water content while increasing slumps
In which situations are retarding admixtures particularly useful?
During large pours with significant temperature increases
According to Section 3.6.3 of the ACI Code, when should calcium chloride not be added to concretes?
In concretes cast against stay-in-place galvanized steel forms
What type of admixture is made from organic sulfonates?
Superplasticizers
Why do some concrete truck drivers keep sacks of sugar on hand?
To throw into the concrete in case of traffic jams or delays
What is the main reason why concretes with the highest percentage of cement-water paste have the highest creep?
The cement-water paste does the creeping
How does the addition of reinforcing to compression areas of concrete affect creep?
Greatly reduces creep
Why do large concrete members experience proportionately less creep compared to smaller thin members?
Smaller distance for water to escape
What percentage of the compressive strength of concrete is the typical tensile strength range?
8% to 15%
Why do cracks in concrete have little effect when the material is under compression loads?
Cracks close and allow compression transfer
How does the presence of reinforcing steel in concrete affect tensile loads?
Reduces tensile strength
Test your knowledge about the creep behavior in concrete, focusing on the factors affecting creep and how reinforcement can help reduce it. Understand the significance of cement-water paste percentage, aggregate choice, and the role of steel reinforcement.
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