Concrete Flashcards
Admixture
A substance other than cement, water and aggregates included in a concret mixture for the purpose of altering one or more properties of the concrete.
Aggregate
Inert particles, such as sand, gravel, crushed stone or expanded minerals in concrete or plaster mixtures.
Particales occupy about 70% tp 75% of total volume of concrete.
Air-Entraining Agents
Agents that form tiny, disperes bubbles in concrete.
- Increase workability & durability
- Improves resistance to freezing and thawing cycles
- Reduce segregation
Chair
Metal wire devices places on concrete formwork to hold the rebars above the bottom of the form at the proper distance.
Concrete
A material combination of cement, fine and course aggregates and water mixed in the proper portions and allowed to cure.
Concrete Architectural Finishes
Finishes where concrete will be exposed and appearance is a consideration
- Form Liner
- Scrubbed
- Acid Wash
- Water Jet
Concrete Rubbed Finishes
- Smooth
- Grout Cleaned
Concrete Slab Finishes
- Float finish (sandpaper like textures)
- Light steel trowel finish
- Hard steel troweled finish (very smooth surface)
- Broom finish
- Superflat floor finish (level)
Concrete Tooled & Sandblasted Finishes
Tooled finishes produces by mechanically modifying concrete surface:
- Brushed Hammering
- Grinding
- Applied
- Sandblasted Finsihes
Construction Joint
A joint that occures wherever there are two sucessive pours of concrete.
Beacause a construction joint creates a plane of weakness, it should be located at points of minimal shear.
Control Joint
An intentinoal, linear discontinuity in a structure or component, designed to form a plane of weakness where cracking can occur in response to various forces so as to minimize or elimiate cracking elsewhere.
Design Strength
The compressive strength of concrete after it has cured and hardened for 28 days.
Expansion Joints
A surface divider joint that provides space for the surface to expand.
Fly Ash
A waste material obtained from coal-fired power plants.
Used in concret to:
- increase strength
- decrease permeability
- reduce temparature rise
- increase sulfate resistance
- improve workability
- decrease total amount of cement needed
Flying Forms
Large fabricated sections of framework that are removed, once the concrete has cured, to be reused in forming an identical section above.
Form Ties
Metal wires or rods used to hold opposite sides of the form together and also to prevent their collapse.
Formwork
A system of boards, ties and bracing required to construct the mold in which wet concrete is placed.
Economy: One of the biggest expenses for C.I.P. concrete. To reduce cost the forms should be reusable as much as possible.
Hydration
The chenical hardening of concrete
A process of combining chemicall with water to form molecules or crystals that include hydroxide radicals or water or crystallization.
Isolation Joints
Allows two adjecent sections to move independenlt of one another, but are not as complex as expansion joints.
Often to separate columns from slabs and slabs from foundation.
Laitance
A chalky surface deposit of low-strength concrete.
Caused by too much water in the concrete mixture resulting in water bleeding to the top.
Must be removed to bond with additional layer of concrete.
Plasticizers
Reduce the amount of water need in concrete while maintinging the necessary consistency for correct placement compaction.
Benefits:
- Makes it possible to mix higher-strength concrete
Portland Cement
The binding agent in concrete.
Made from:
- Lime
- silica
- iron oxide
- alumina
Reinforcing Bars
(rebar)
Steel to reinforce contrete to increase tensile strength.
Diameters are in 1/8” increments.
Common grades:
- grade 40
- grade 60
Segregation
Separation of the constituents of wet concrete caused by excessive handeling or vibration.
Slip Forming
A special form where it moves as the concrete cures. This type of forming is used to form continuous surfaces such as tunnels and high-rise building cores.
Type I Cement
Standard Cement or Normal Cement
Used for most general construction where the other types are not needed.
Type II Cement
Modified cement
Used in places where a modest amount of sulfate resistance is needed and where the heat of hydration needs to be controlled.
- Dams
- Other massive structures
Type III Cement
High-early-strength cement
Used where a quick set is needed. Has a higher heat of hydration, suitable for cold-weather concreting.
Type IV Cement
Low-heat cement
Used in massive structures to minimize cracking. Very slow setting.
Type V Cement
Sulfate-resisting cement
Used for structures that will be exposed to water or soil with a high alkaline content.
Concrete Sealers
- Coating sealer types
- Penetrating sealer types
Precast Concrete
Concrete cast and cured in a postion other than its final position in the structure
