ICC Reinforced Concrete SI flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Purpose of concrete inspection

To observe materials, placement, and workmanship and judge whether the work conforms to the plans and specifications. It supplements, but does not replace, the contractor's own quality control program.

Minimum clear bar spacing

For parallel bars in a layer, clear spacing must be at least the larger of one bar diameter, 1.33 times the maximum coarse aggregate size, or 25 mm.

Cover measurement

Cover is the clear distance from the concrete surface to the outermost reinforcement. Measure to the bar or stirrup closest to the surface, not to an inner bar.

Formwork pre-pour check

Verify line, grade, dimensions, tight joints, release agent, ties, and shores. Forms must be clean and free of debris and standing water before placement begins.

Cold-weather placement

Concrete should be placed at a temperature specified for the project, commonly at least 10 °C, and protected until it reaches specified strength. Never place on frozen subgrade.

Hot-weather concrete limits

Concrete temperature as placed is commonly limited to about 35 °C. Cooling ingredients, set retarders, and immediate curing reduce plastic shrinkage cracking and rapid moisture loss.

Slump test (ASTM C143)

Measures consistency of fresh concrete. A collapsed or sheared slump is invalid and the sample must be retested. Slump is not a measure of strength or durability.

Air content by pressure method

ASTM C231 measures entrained air in fresh concrete. Freeze-thaw exposure typically requires about 5–7 percent air with 20 mm aggregate, adjusted for the exposure class.

Water-cementitious materials ratio

The ratio of water to cementitious material by mass. Lower w/cm increases strength and reduces permeability; it is the primary control on concrete quality.

Cylinder curing per ASTM C31

Standard-cured cylinders are moist cured at controlled temperature and represent the mix. Field-cured cylinders are stored near the structure and represent in-place strength.

Strength test sampling frequency

Take a test set at least once per day of placement, once per 110 m³ or fraction, and once per 460 m² of slab or wall. Each set consists of two cylinders.

Consolidation with vibrator

Insert the vibrator vertically at regular spacing and hold until air bubbles cease, then withdraw slowly. Never use vibration to move concrete laterally in the form.

Curing duration

Maintain moisture and temperature for the specified period, commonly 7 days for Type I cement and 3 days for high-early-strength cement, unless the specification states otherwise.

Construction joint preparation

Planned joints must be cleaned, roughened, and often fitted with shear keys or dowels. Unplanned cold joints from interruptions are defects and should be reported.

Free fall limit

Concrete should be placed near its final position; free fall is commonly limited to about 1.5 m to prevent segregation. Use chutes or drop pipes for deeper placements.

Bar number to diameter

For metric deformed bars, the bar number times 3 gives nominal diameter in mm. No. 20 is 20 mm diameter; No. 25 is 25 mm diameter.

Bar number to area

For metric deformed bars, the bar number times 100 gives nominal area in mm². No. 20 has about 300 mm²; No. 25 has about 500 mm².

Common bar grade

Grade 420 MPa (formerly Grade 60) is the common deformed bar grade. Grade 550 MPa (Grade 80) is used where higher strength is specified.

Class A and Class B splices

Tension lap splices are Class A (1.0 times development length) or Class B (1.3 times development length). The class depends on the fraction of steel spliced and the stress level.

Minimum development length

Tension development length depends on bar size, cover, spacing, transverse reinforcement, and concrete strength. It is never less than 300 mm.

Standard 90-degree hook

A standard 90° hook has a minimum extension of 12 bar diameters beyond the bend. Hook geometry and bend diameter vary with bar size.

Mechanical and welded splices

Mechanical splices must be qualified by test. Welded splices require a qualified welding procedure and welder, and are not permitted for all bar grades.

Post-tensioning

Strands in ducts are stressed after the concrete hardens and the force is transferred through anchorages. Ducts are grouted after stressing to protect the steel.

Pretensioning

Strands are stressed before concrete is placed and force is transferred to the concrete by bond when the strands are released. Used mainly in precast members.

Stressing force verification

Tendon force is checked by both elongation and gauge pressure; the two must agree within a specified tolerance, commonly about 5 percent. Discrepancies are investigated before grouting.

Duct grouting

Post-tensioning ducts are grouted promptly after stressing with an approved grout. Vents at high points ensure complete filling; incomplete grouting is a corrosion risk.

Bar schedule on drawings

The bar schedule lists bar marks, sizes, shapes, lengths, and quantities. The inspector checks field placement and splices against the approved placing drawings.

Cover for exposed members

Cast-in-place beams and columns exposed to earth or weather commonly require at least 40 mm cover. Verify the exact value against the project specification and exposure class.

Two-layer bar arrangement

When bars are placed in two or more layers, bars in the upper layer are placed directly above those in the lower layer, with the required clear spacing maintained.

Strength acceptance criteria

The average of three consecutive strength tests must equal or exceed the specified strength, and no single test may fall below a specified lower threshold. Failing results trigger investigation.

Core testing after failure

When cylinder tests fail, the engineer may require cores per ASTM C42 from representative locations. Core results are evaluated against specified acceptance criteria.

Governing code documents

ACI 318 covers structural design and detailing; ACI 301 covers construction specifications; ACI 302 covers slabs on grade. Project specifications govern where they conflict with general references.