ACI CTCI flashcards
ACI CTCI · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Slump test standard
- ASTM C143 procedure measuring concrete consistency by the vertical settlement of a molded cone; reported to the nearest 6 mm (1/4 in.). Not a direct measure of strength.
- Air content pressure method
- ASTM C231 test that determines air content of normal-weight concrete by applying pressure and measuring volume change; unsuitable for lightweight or highly porous aggregate concrete.
- Volumetric air test
- ASTM C173 method that measures air content by agitating concrete to remove air and measuring the volume change; used for lightweight aggregate concrete where pressure method is unreliable.
- Standard cylinder size
- ASTM C31 compressive strength specimens are typically 150 mm diameter by 300 mm high (6 by 12 in.); smaller cylinders require correction factors if used.
- Strength acceptance rule
- ACI 318/301 acceptance: no single test more than 3.5 MPa (500 psi) below f'c, and no average of three consecutive tests below f'c.
- Concrete temperature test
- ASTM C1064: calibrated thermometer inserted at least 75 mm into fresh concrete; temperature recorded to nearest 0.5 °C (1 °F) at the time of sampling.
- Sampling fresh concrete
- ASTM C172 requires a composite sample taken from the middle portion of the discharge, avoiding the first and last portions, then remixed before testing.
- Field cylinder initial cure
- Cylinders are stored in the field at about 16–27 °C (60–80 °F) for 24 ± 8 hours before transport, then moist-cured per ASTM C31 until testing.
- Flexural strength test
- ASTM C78 third-point loading of a beam specimen to determine modulus of rupture; commonly used for pavement acceptance criteria.
- Unit weight and yield
- ASTM C138 measures fresh concrete density; comparing measured to calculated yield detects batching errors or incorrect air content.
- 7 and 28 day tests
- Standard compressive strength tests are typically performed at 7 days for early indication and 28 days for acceptance; a test result is the average of two cylinders.
- Cylinder transport timing
- Specimens must be transported to the laboratory after initial field curing without being subjected to jarring or freezing, and remain moist until tested.
- Formwork removal timing
- Vertical forms may be removed when concrete resists surface damage; supporting formwork requires sufficient strength to carry loads plus construction loads per ACI 301.
- Pre-placement inspection
- Verify forms are tight, clean, and coated; reinforcement size, spacing, cover, and splices are correct; subgrade stable; embedded items and blockouts in place.
- Rebar cover tolerance
- ACI 117 tolerances: for members over 300 mm, cover may vary minus 6 mm and plus 13 mm from specified values; smaller members have tighter tolerances.
- Free fall limit
- Concrete should not free-fall more than about 1.5 m (5 ft) unless a drop pipe or chute is used, to prevent segregation of aggregates from mortar.
- Vibrator use
- Internal vibrators should penetrate the previous lift a few inches and be withdrawn slowly; vibrators must not be used to move concrete laterally in forms.
- Construction joint prep
- Joints must be at planned locations, roughened, cleaned, and moistened; reinforcement must run continuously through the joint; unplanned joints need engineer approval.
- Curing duration rule
- ACI 301/308: cure typically 7 days for Type I cement and 3 days for Type III at mild temperatures; extend in cold weather or when specified.
- Hot weather placement
- Limit concrete temperature at placement (commonly ≤ 35 °C / 95 °F); use fog spray, windbreaks, or evaporation retarders to prevent plastic shrinkage cracking.
- Cold weather protection
- ACI 306 requires protecting concrete from freezing and maintaining adequate temperature until it reaches sufficient strength; protection periods depend on ambient conditions and cement type.
- Consolidation purpose
- Vibration removes entrapped air and ensures concrete fills forms and encases reinforcement; inadequate consolidation causes honeycomb and voids.
- Reinforcement inspection
- Confirm bar size, spacing, cover, lap splice length, and chair/support placement match drawings before placement; deviations require engineer approval.
- Release agent check
- Form release agents must be applied uniformly and not contaminate reinforcement or construction joint surfaces; excess must be removed before placement.
- Slump reporting units
- Slump is recorded to the nearest 6 mm (1/4 in.); a collapsed or sheared slump indicates a nonconforming sample that should be discarded and resampled.
- Test result definition
- A compressive strength test result is the average of two cylinders made from the same sample and tested at the same age; single low cylinders trigger investigation.
- Moist curing requirement
- Standard cured specimens must remain moist at about 23 °C (73 °F) until testing; dry curing lowers measured strength and misrepresents field performance.
- Air content specification
- Air content is specified by exposure class; entrained air improves freeze-thaw durability; field tests verify the target range is maintained during placement.
- Fresh concrete sampling point
- Samples must represent the middle of the discharge; the first and last portions of a truckload are not representative and should not be used for acceptance tests.
- Curing compound use
- Liquid membrane curing compounds must be applied at specified coverage rate; they are not permitted where bond to future concrete or finishes is required.
- Embedded items check
- Before placement, verify anchors, sleeves, blockouts, and waterstops are correctly positioned and secured so they are not displaced during concrete placement.
- Evaporation rate limit
- When evaporation rate exceeds about 1 kg/m²/h (0.2 lb/ft²/h), plastic shrinkage cracking risk is high; use windbreaks, fog, or retarders during placement.