ACI Aggregate Level 2 key terms

A test that shakes a dried aggregate sample through a stack of sieves with progressively smaller openings to determine how much material is retained on each sieve and to calculate the gradation.

The distribution of particle sizes in an aggregate sample, expressed as the percentage of material passing each sieve in a specified series and compared against a required size range.

The portion of a sample, by mass, that passes through a given sieve opening, usually calculated from the cumulative mass retained and reported to the nearest whole percent for most sieves.

The total percentage of the original sample mass held on a given sieve plus all larger sieves above it, calculated by dividing cumulative retained mass by total dry mass.

The percentage of the total dry sample mass that stays on one individual sieve, found by dividing the mass retained on that sieve by the total sample mass and multiplying by 100.

The smallest sieve opening through which the entire aggregate sample would pass if a one-sieve allowance is applied, meaning up to about 10 percent of the sample may be coarser.

The smallest sieve opening through which all particles in a sample pass, determined from sieve analysis and used to select test sample masses and specimen sizes.

A single number describing the coarseness of a fine aggregate, computed as the sum of cumulative percent retained on a standard sieve series divided by 100.

Aggregate particles passing the 4.75 mm (No. 4) sieve and predominantly retained on the 75 micrometer (No. 200) sieve, typically natural sand or crushed stone screenings used in concrete and asphalt.

Aggregate particles predominantly retained on the 4.75 mm (No. 4) sieve, including gravel, crushed stone, or slag used as the structural skeleton of concrete and base layers.

The mass of an aggregate sample after drying at a specified temperature until constant mass is reached, used as the reference basis for most test calculations.

A condition where repeated drying and weighing at the specified interval produce a mass change no greater than the amount allowed by the test method, indicating free moisture has been removed.

The mass of water present in an aggregate expressed as a percentage of the oven-dry mass, determined by weighing before and after drying.

The increase in mass of an aggregate after soaking in water, expressed as a percentage of its oven-dry mass, reflecting the pore space that fills with water.

The ratio of the oven-dry mass of an aggregate to the mass of water displaced by the aggregate including its permeable pores, used in volumetric mix calculations.

The ratio of the saturated surface-dry mass of an aggregate to the mass of water displaced by the aggregate, accounting for water held in permeable pores.

The ratio of the oven-dry mass of an aggregate to the mass of water displaced by the solid particles only, excluding permeable pore space.

A condition in which an aggregate's permeable pores are full of water but no free moisture remains on the particle surface, reached by towel-drying and checked with a cone test.

A test in which an aggregate sample and steel spheres tumble inside a rotating drum to measure resistance to degradation, reported as the percentage of material lost.

A durability test in which aggregate is repeatedly soaked in saturated sodium sulfate solution and oven-dried, and the resulting mass loss indicates resistance to weathering.

A test that measures the relative proportion of clay-like fines to clean sand in fine aggregate by settling a sample in a graduated cylinder with flocculating solution.

Soft or clayey pieces in aggregate that break down when wet-sieved, measured as a percentage of the sample mass and limited because they weaken concrete and base material.

Aggregate particles whose length or width exceeds a specified multiple of their thickness, counted with a proportional caliper and reported as a percentage because such shapes reduce performance.

Particles in aggregate that float in a heavy liquid of specified specific gravity, separated and reported as a percentage because they indicate coal, wood, or other low-density material.

Any substance in aggregate that harms the performance of concrete, asphalt, or base courses, such as organic matter, clay, coal, or soft fragments, typically limited by specification.

The process of dividing a large field sample into smaller representative portions using a mechanical splitter or quartering so each test receives a specimen of suitable mass.

A device with a series of chutes that divides a free-flowing aggregate sample into two or more portions of nearly equal mass, used to obtain representative test specimens.

The minimum quantity of aggregate required for a given test, set by the test method based on the nominal maximum size so results are representative of the material.

A laboratory test that compacts aggregate base material in a mold at controlled moisture and energy to determine the relationship between moisture content and dry unit weight.

The highest dry unit weight a soil or aggregate base can achieve at a given compaction energy, taken from the peak of the compaction curve.

The moisture content at which a soil or aggregate base reaches its maximum dry density for a given compaction effort, corresponding to the peak of the compaction curve.

A plot of dry unit weight versus moisture content from a laboratory compaction test, forming a curve whose peak defines maximum dry density and optimum moisture content.

The field dry unit weight expressed as a percentage of the laboratory maximum dry density, used to judge whether a compacted base layer meets specification.

An in-place measurement of the compacted base's unit weight and moisture, often by the sand cone or nuclear gauge method, compared against laboratory reference values.

A field test that determines in-place dry density by measuring the volume of a test hole using calibrated sand of known density and the mass of material removed.

A penetration test that compares the resistance of a compacted aggregate base specimen to that of a standard crushed stone, used to design pavement thickness.

A laboratory measure of an aggregate base's stiffness under repeated axial loading, representing recoverable strain and used in mechanistic pavement design.

A graded crushed stone or gravel layer placed beneath pavements to spread loads, provide drainage, and resist deformation, specified by gradation and physical quality requirements.

The moisture content at which a fine-grained soil or binder fraction changes from plastic to liquid behavior, determined with the Casagrande cup or fall cone device.

The moisture content at which a fine-grained material stops behaving plastically and begins to crumble when rolled into a thread of specified diameter.

The numerical difference between the liquid limit and plastic limit, indicating the range of moisture over which a material remains plastic.