Concrete Flashcards
Concrete
Aggregate, Cement, Water, and Admixture
Portland Cement
Lime, Silica, Alumina, Gypsum
How long does Cement take to reach full strength?
28 Days
Isolation (expansion) Joint
Provide for lateral movement between slabs. Extend the full depth of the Concrete
Concrete Qualities
Strength, Durability, Stability, Availability, Adaptability, and Low-cost
Properties of Concrete
Constituents, Skills used in placing
Concrete resistance to freeze/thaw and deicing chemicals
Apply admixtures
Concrete resistance to abrasion and wear
Increased if the concrete mix contains well-graded strong aggregate
Methods of Concrete Placement
Cast in Place, Sprayed, Mixed in Place
Process of Hydration
Cement and Water mixture results in hardening
Types of Aggregate for Concrete
Sand, Gravel, Crushed Stone
Selection of Aggregate for Concrete
Resistance to abrasion, Performance, Resistance to effects of freezing/chemicals, Range of Aggregates
Admixtures
Workability, Reduce Moisture, Increase durability, Resistance to Freezing, Accelerate or retard hardening or setting, Increase Flowability
Water Quality for Concrete
Potable Water (Uncontaminated)
2 Styles of Mixing Concrete
Ready-mix and On-site Mixing
Slump Test
Determines Relative Consistency & Reflects changes in the amount of water in the mix
Air Content Test
Determines the air entertainment at the time of use
Cylinder Test
Determines the compressive strength of cured concrete
Site Preparation for Use of Concrete
Granular sub-base over-prepared, and compacted, subgrade
Benefits of Reinforcement
Controls cracking and give greater tensile strength
Purpose of Joints
Minimize damaging effects of expansion and contraction in concrete due to temperature variations and the presence of moisture
Control, or contraction, joints
Designed to restrict the cracking of concrete at predetermined locations. ¼ to ⅓ the thickness of the concrete. At intervals roughly the width of slab
Construction Joint
Provide places where the casting of concrete can be stopped
Joint Fillers
Joints tend to be filled and sealed to keep out moisture and debris
Types of Joint Fillers
Fiber Filler
Wood Dividers
Plastics, rubber, cork, or metal
Joint Sealant
Prevents filler material from bleeding or being squeezed up. Keep out debris. Keep out water
Two of the most common types of concrete finishes
Floating and Troweling
Colored Concrete One Course Method
Mixing pigments when concrete is created
Colored Concrete Two-Course Method
Top or finish surface after laying regular concrete
Dry-shake Method
Sprinkling Special pigments on the surface
Stains and Paints
Typically done on existing concrete
Exposed Aggregate
Resistance to slipping and heavy wear
One-course Aggregate Finish
Fine aggregate added to the concrete mix. Hosing or acid washing and brushing
Surface retardant applied
Two-course Aggregate Finish
Base concrete laid. Concrete topping with aggregate added over base concrete Hosing or acid washing and brushing
Seeding Aggregate Finish
Sprinkling aggregate over a freshly placed concrete base
Special Non-slip finishes
Floats, trowels, brooms, or dry-shaking grains onto the surface. Grains such as Silicon carbide and aluminum oxide
Edging
Prevents chipping
Helps compact and harden
Wet Covering
Covering with moisture-retaining fabric
Keeps concrete wet
Waterproof paper or plastic sheets
Prevents rapid loss of moisture from the concrete
Sprinkling or ponding of water
Effective but expensive
Sand or earth berms to be removed later
Curing compounds
Used in conjunction with coverings. Used to help sustain curing
Temperature Control
Cover with sheets. Use Heaters
Sealers and Glaziers
Prevent or Reduce Moisture Penetration and Chloride Penetration
Sealers and Glaziers
Used to waterproof or bring out the natural color
Restoration and Repair of Concrete
(1) Removal/Cleaning of Damaged Concrete
(2) Concrete or grout is mixed in small amounts
(3) Treat damaged areas
