Chapter 13
What is the Tension and Compression of Concrete?
0 psi, 2,000 to 22,000+ psi
What is the Tension and Compression of Brick?
0 psi, 250 psi
#8 bar diameter
1 in.
#4 bar diameter
1/2 in.
What is the Tension and Compression of Steel?
22,000 psi
Concrete strength is normally specified at
28 days
Specified maximum slump is usually in the range of
3 to 5 inches
W12 wires spaces at __in. crossed by W5 Wires spaced at __ in.
6, 12
What percent of total concrete volume do coarse and fine aggregates make up
60-80%
What is the Tension and Compression of Wood?
700 psi, 1,100 psi
Affects workability of wet concrete
Aggregate Grading
Strength of concrete is heavily dependent on the quality of the ______
Aggregates
Ingredients added generating bubbles during concrete mixture that create small, distributed voids in the finished concrete
Air-Entraining Cement
This type of cement has a greater resistance to freeze-thaw damage, Improved workability when wet, but reduces concrete strength
Air-Entraining Cement
Solutions for curing concrete in cold weather
Blankets (cover), Temporary Heat
In a simply supported beam, the greatest tension forces occur at the ______ of the beam
Bottom middle
Provide the structural mass of concrete and constitute the majority of the concrete volume
Coarse and Fine Aggregates
Causes hydration to proceeds much slower and risk if freezing
Cold Weather
Temporary structure to hold freshly poured concrete in the desired shape
Concrete Framework
Welded Wire Reinforcing is especially common for _____ reinforcing
Concrete slab
Eliminates voids and air pockets within the concrete pour
Consolidation
Unit of mixture for concrete
Cubic Yard
What is used when the reinforcing may be exposed to salts or sea water
Epoxy Coated Rebar
T or F concrete has a high tensile strength ?
False, no useful tensile strength
Short fibers of glass, steel, or polypropylene are added to the concrete mix
Fibrous Reinforcing
What are the ingredients in concrete?
Fine Aggregate (sand) Coarse Aggregate (gravel) Portland Cement (Calcium Silicates) Water
Oils, waxes or plastic coatings
Form releasing compounds
Distribution of aggregate particle sizes
Grading
In conventional concrete construction, formwork can account for how much of the total concrete construction costs
Half or more
Concrete with too ___ slump may have to much water added
High
Type III
High Early Strength
Type IIIA
High Early Strength, Air Entraining
Type V
High Resistance to sulfate attack
Greater then 6000 psi to roughly 20,000 psi
High-Strength Concrete
What is used to reduce rebar congestion
Higher strength bars
Causes issues such as Premature Drying, and Accelerated Curing
Hot Weather
Concrete is placed into a conical cylinder; the cylinder is removed, and the loss in height of the concrete mass is measured.
How a slump test is performed
The chemical bonding of water and cement
Hydration
Expanded shale,clay,slate,slag Cinders and other volcanic rocks Vermiculate Perlite
Lightweight Aggregates
Used to make lighter-weight concrete
Lightweight Aggregates
Concrete with too ___ slump may be difficult to place
Low
Type IV
Low hear of hydration
A _____ percentage of void space between particles results in a ________ concrete that requires less cement
Lower, Stronger
Greater concentrations of fibers, that also resist longer-term cracking due to drying and thermal stresses
Macrofiber Reinforcing
Relatively low amounts of fibers, to aid concrete in resisting plastic shrinkage
Microfiber Reinforcing
Type IIA
Moderate Resistance to sulfate attack, Air Entraining
Type II Cement
Moderate resistance to sulfate attack
Roughly 60% or less of the weight of ordinary concrete, insulating roof toppings, fill material, density approx. 20-25% of regular concrete
Nonstructural Lightweight Concrete
Up to 6000 psi compressive strength
Normal Strength Concrete
Type IA Cement
Normal, Air entraining
Type I Cement
Normal, General Purpose
Cracking that occurs during early curing
Plastic Shrinkage
This binds the aggregate in concrete
Portland Cement (Calcium Silicates)
Steel strands are tensioned after concrete has been cast and reached adequate strength
Post-tensioning
Applying an initial compressive strength to a concrete member, so as to improve its structural efficiency
Prestressing
High-strength steel strands are stretched tightly and then restrained by the concrete, putting the concrete into initial compression
Prestressing
Its advantages include Increase the load carrying capacity Increase span length Reduce member size
Prestressing
Steel strands are tensioned before concrete is cast
Pretensioning
Hot-rolled steel, deformed with surface ridges so as to better bond with concrete
Rebar
Most common concrete reinforcing material
Rebar
When reinforcing becomes crowded and concrete placement
Rebar Congestion
Who prepares shop drawings that are reviewed by the structural engineer
Reinforcing Fabricator
What is the advantage to WWR
Saves Labor
Excessive vibration, dropping from excessive heights, and moving concrete horizontally have what effect on the concrete
Segregation
Seperation of large aggregate from the finer portions of the mix, must be avoided
Segregation
Provides a rough measure of the workability of concrete while wet
Slump test
What are laid into concrete along lines of tension to provide resistance to pulling forces?
Steel Bars or Wires
Also increases the durability of the concrete surface
Steel Fiber Reinforcing
Structural properties when hardened
Strength, stiffness, durability
Where are concrete reinforcing requirements shown
Structural Drawings
Roughly 80% or less of the weight of ordinary concrete, reduced stricture weight saves cost, lower thermal conductivity increases resistance to building fires, Density approx. 80% of regular concrete
Structural Lightweight Concrete
Ability to resist pulling forces
Tensile Strength
Prevent the vertical bars from buckling outward
Ties
Wrap around the vertical bars
Ties or Spirals
T or F Prestressed members are typically more slender and lighter than comparable conventional reinforced members
True
This type of cement is used for cold weather construction, concrete precast on plants, and accelerated construction schedules
Type III
This type of cement is used for massive structures, such as dams, where heat generated during hydration must be limited to avoid excessive temperatures
Type IV
These types of cement is used for concrete in contact with soils or water with high sulfate concentrations
Types II and Type V
Add to the strength of the column in compression, and resist tensile forces that are introduced from wind of seismic forces, or from connections to beams
Vertical Bars
Is necessary for the chemical hydration of the cement and the hardening of the concrete
Water
_____ is an essential ingredient in concrete, that combines chemically with the cement as the concrete hardens
Water
WWF
Welded Wire Fabric
WWR
Welded Wire Reinforcing
Prefab welded grids of reinforcing bars or wires
Welded Wire Reinforcing or Welded Wire Fabric
Ease of placing, consolidating, & finishing wet concrete
Workability
Solutions for curing concrete in hot weather
ice subsisted for water, early or late placement times
Slump tests are performed on batches of concrete as
they arrive on the site