ACI Aggregate Level 2 flashcards
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33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Fineness modulus
- Sum of cumulative percent retained on the 4.75, 2.36, 1.18, 0.600, 0.300, and 0.150 mm sieves divided by 100. Higher values indicate coarser aggregate.
- Nominal maximum size
- The smallest sieve opening through which 100 percent of the aggregate sample passes. It is one sieve size larger than the maximum size for most specifications.
- Bulk specific gravity
- Ratio of oven-dry mass to the volume of aggregate including permeable pores, expressed as A/(B−C) where A is dry mass, B is SSD mass, and C is submerged mass.
- Apparent specific gravity
- Ratio of oven-dry mass to the volume excluding permeable pores. It is higher than bulk specific gravity and uses A/(A−C) in the standard formula.
- Absorption
- Mass of water absorbed into permeable pores divided by oven-dry mass, times 100. Computed as (SSD mass − oven-dry mass) / oven-dry mass × 100.
- Los Angeles abrasion loss
- Percent mass lost during 500 revolutions in the LA abrasion machine. Calculated as (initial mass − retained mass) / initial mass × 100.
- Sodium sulfate soundness
- Percent mass loss after repeated immersion and drying cycles in sodium sulfate solution. Calculated as (initial mass − final mass) / initial mass × 100.
- Flat and elongated particles
- Particles whose length exceeds a set ratio of thickness, measured with a proportional caliper at 3:1 or 5:1. Reported as mass percent of the sample.
- Clay lumps and friable particles
- Percent of material that breaks down when wet sieved, computed as mass of retained lumps divided by total dry sample mass times 100.
- Percent passing formula
- Cumulative percent retained on a sieve divided by total dry mass times 100 gives percent retained. Percent passing equals 100 minus that cumulative percent retained.
- Maximum size definition
- The smallest sieve through which the entire sample passes, allowing up to 100 percent passing the next larger sieve. It is one size larger than nominal maximum size.
- Organic impurities test
- Colorimetric comparison of a sodium hydroxide solution above the aggregate against a standard color solution. Darker color indicates possible organic contamination.
- Moisture content of aggregate
- Mass of water divided by oven-dry mass, times 100. Computed as (wet mass − dry mass) / dry mass × 100.
- Bulk SSD specific gravity
- Ratio of saturated-surface-dry mass to the volume including permeable pores. Uses B/(B−C) where B is SSD mass and C is submerged mass.
- Sieve analysis purpose
- Determines particle size distribution by mass retained on each sieve. Results are plotted as percent passing versus sieve opening on a semi-log scale.
- Aggregate crushing value
- Percent fines produced by a standard compressive load on a confined aggregate sample. Calculated as mass passing the test sieve divided by initial mass times 100.
- Proctor dry unit weight
- Mass of moist soil divided by mold volume, then divided by (1 + moisture content as decimal). The peak of the curve is maximum dry unit weight.
- Optimum moisture content
- Moisture content at which the compaction curve reaches maximum dry unit weight. It is read from the peak of the moisture-density curve.
- Relative compaction
- Field dry unit weight divided by laboratory maximum dry unit weight, times 100. Base acceptance is typically 95 to 100 percent of maximum.
- California Bearing Ratio
- Test load divided by standard load at the same penetration, times 100. Standard loads are 1000 psi at 0.1 in and 1500 psi at 0.2 in.
- Plasticity index
- Liquid limit minus plastic limit. It indicates the range of moisture over which the material remains plastic; near-zero PI means non-plastic base.
- Liquid limit test
- Moisture content at which a soil closes a standard groove under a specified number of blows or cone penetration. Reported as the liquid limit.
- Sand equivalent value
- Sand reading divided by clay reading, times 100. Higher values indicate cleaner aggregate with fewer plastic fines in the base material.
- Sand cone test
- Field density method using a calibrated sand to measure the volume of an excavated hole. Dry density is computed from recovered soil mass and moisture.
- Nuclear gauge density
- Field device that measures wet density and moisture by radiation attenuation. Readings are corrected and converted to dry density for compaction acceptance.
- Compaction curve shape
- Plastic fines widen the curve and lower maximum dry unit weight. Clean granular base gives a sharper curve with higher maximum dry unit weight.
- Base gradation check
- Compares percent passing each control sieve to the specification band limits. Material outside the band is rejected or requires adjustment.
- Zero air voids curve
- Theoretical line of saturation plotted with the compaction curve. Points plotting on or right of it indicate saturation or measurement error.
- Moisture content for compaction
- Water mass divided by dry soil mass, times 100. Dry density requires dividing wet density by (1 + moisture content as decimal).
- Field density correction
- Measured wet density is converted to dry density using oven-dry moisture content. Compaction percent compares dry density to laboratory maximum dry density.
- Liquid limit one-point method
- Estimates liquid limit from a single blow count using a correction factor chart. It is used when the multipoint test is impractical.
- Plastic limit test
- Moisture content at which a soil thread crumbles at 3 mm diameter. Plastic limit is used with liquid limit to compute plasticity index.
- Base course acceptance
- Requires gradation within the band, plasticity index within limits, and relative compaction at or above the specified percentage of maximum dry density.