Chapter 13

Question 1

What is modern concrete made with?

Answer 1

Portland Cement, Mixed aggregate, fine sand and water.

Question 2

How long does it take for concrete to cure?

Answer 2

28 days

Question 3

How is cement made ?

Answer 3

a process where materials are extracted from the earth, and blended into a fine powder. Then the materials are placed into a rotating kiln that makes clinker, so as the ingredients travel down a slope as it rotates, gypsum is added to adjust the cement’s settling rate where it is then separate by air, sent through a dust collector then placed in storage until it needs to be used.

Question 4

What are the Cement types?

Answer 4

Type I, Type II and V, Type III, Type IV, Type IA, IIA, IIIA

Question 5

Type I

Answer 5

General Purpose

Question 6

Type II and V

Answer 6

For concrete in contact with soils or water with high sulfate concentrations

Question 7

Type III

Answer 7

For cold weather construction, concrete precast in plants, accelerated construction schedules

Question 8

Type IV

Answer 8

For massive structures like dams, where the heat generated during hydrate must be limited to avoid excessive temp

Question 9

Type IA, IIA, IIIA

Answer 9

Air-Entrained cause microscopic air bubbles, which increase freeze-thaw resistance and improve workability.

Question 10

What is a slump test?

Answer 10

, where the water cement ratio is used to determine the workability of concrete. They fill a cone, with concrete, then remove the form to measure the slump distance.

Question 11

Testing Cylinder

Answer 11

They are used to test the strength of concrete, the cylinder is filled with concrete and cured on site, then it is taken to a lab for compression testing.

Question 12

What is the influence of concrete strength and moisture?

Answer 12

The strength of the concrete is primarily dependent of the amount of cement in the mix. It is extremely important that concrete is formulated with the right quantity of water for each situation to ensure workability, but also not enough to affect the properties of the material.

Question 13

What are reinforcing bars?

Answer 13

: They are used to hold the concrete in position until the concrete has completely cured.

Question 14

Welded Wire Fabric

Answer 14

are used to reinforce slabs on grade and precast elements. In gridded wires spaced 2-12 inches apart and specified in wire gauge and spacing. It does not support heavy loading.

Question 15

Lapped/Wedged connections:

Answer 15

Used to connect new bars to old ones

Question 16

Cadwelds

Answer 16

Super strong weld

Question 17

Grouted Sleeve Connector

Answer 17

Used for joining components

Question 18

Threaded Sleeve Connector

Answer 18

Where both bars are threaded and screwed into the sleeve

Question 19

Clamping Sleeve

Answer 19

Align compression bars in a column

Question 20

Coupler

Answer 20

The are used for splicing bare at the face on concrete or beam

Question 21

Long Bridge Pier

Answer 21

Requires reinforced splicing, fabricated on the ground and threaded in place

Question 22

How does beam reinforcement work?

Answer 22

Simple concrete beams reinforcing includes heavy bottom bars, lighter top bars and U-shaped shear stirrups.

Question 23

How do beams counteract compressive stresses and tensile stresses?

Answer 23

Rectangular setups are used to protect against corrosion and embedment

Question 24

Formwork?

Answer 24

During the curing stages, the formwork helps to retain the necessary water or hydration in the concrete and also has a direct relation to the quality of the concrete finish surface. When complete the formwork must clearly separate. They are treated with a form release compound that presents adhesion of concrete to the form. They can come in different forms like wood, metal or plastic.

Question 25

Pre-Stressing Concrete

Answer 25

Reinforced concrete members become part of the member in compression and part of the member in tension. If the initial tension, prestress in the steel were enough the secondary concrete would never be subject to tension and no cracking would occur

Question 26

Advantages of Pre-stressing Concrete?

Answer 26

an increase in load carrying capacity, span length and relation of the member size

Question 27

What happens when a beam is prestressed?

Answer 27

the concrete compresses, but under loading the beam becomes flatter and no cracking happens. It is usually done before concrete placement.

Question 28

What is post-tensioning?

Answer 28

Where cables a posttensioned prior to concrete placement and curing. The net effect is that abutments aren’t needed because the member itself provides the abutting force needed to tension the steel