ACI Aggregate Level 1 key terms

A method of shrinking a bulk field sample to a test-sized portion by mixing it, piling it into a flattened cone, dividing the pile into four equal quarters, and keeping two opposite quarters. The process is repeated until the desired mass remains.

A device with a series of chutes that divides a falling aggregate stream into two or more representative portions of nearly equal mass. It reduces sample size without the operator bias possible in hand quartering.

A portion of aggregate whose properties reflect the average character of the entire lot, with all size fractions and components present in their true proportions. Sampling and reduction procedures must preserve this quality.

The large initial quantity of aggregate collected from a stockpile, bin, or truck that is reduced by splitting or quartering into smaller test portions. Its mass must be enough to supply all required tests.

The reduced portion of aggregate, prepared from a bulk sample, that is actually used in a single laboratory test. It must meet the minimum mass required by the test method for the largest particle size present.

Collecting aggregate from a stockpile using a sampling thief or by taking portions from several locations and depths, avoiding the coarse segregated edges and the fine material at the base. Multiple increments are combined into one bulk sample.

A single small portion of aggregate taken at one location or time as part of a sampling plan. Several increments are combined to form the bulk sample so that natural variability is captured.

Selecting sampling locations or times by a chance method so that every part of the lot has an equal opportunity to be included. It avoids conscious or unconscious bias toward convenient or visually typical material.

The separation of coarse and fine particles within a mass of aggregate during handling or stockpiling, often leaving coarse particles at the edges and fines in the center. It can make a sample unrepresentative if not countered by proper sampling.

The mass of water present in an aggregate sample expressed as a percentage of either the oven-dry mass or the as-received total mass, depending on the convention used. It is determined by drying and comparing masses before and after.

The mass of an aggregate sample after drying at a specified temperature, typically 110 ± 5 °C, until it reaches constant mass. It is the reference basis for moisture content and many specific gravity calculations.

A condition reached when successive weighings of a drying sample, taken at intervals of at least one hour of continued drying, differ by no more than a specified small amount. It confirms that free moisture has been removed.

The state in which the permeable pores of aggregate particles are full of water but no free water remains on the particle surfaces. It is reached by soaking and then surface-drying, and it is the basis for absorption and bulk specific gravity tests.

The mass of aggregate that fills a unit volume of a container, including both particles and the voids between them. It is used to convert mass to volume and to check batching quantities.

The percentage of the total volume of an aggregate mass that is occupied by spaces between particles rather than by solid material. It is computed from bulk density and bulk specific gravity and affects paste demand in concrete.

A bulk density determination in which each of three equal layers of aggregate is compacted with a specified number of blows from a tamping rod before the container is struck off and weighed. It represents a compacted field condition.

A bulk density determination in which aggregate is poured into the measuring container without compaction, filling it to overflowing before strike-off. It represents the least compacted condition of the material.

The ratio of the oven-dry mass of an aggregate to the mass of water displaced by the particle volume including its permeable pores. It reflects the overall density of the particles as they exist in a batch.

The ratio of the mass of a saturated surface-dry aggregate to the mass of water displaced by its total particle volume including permeable pores. It is used in mixture proportioning calculations involving saturated aggregates.

The ratio of the oven-dry mass of an aggregate to the mass of water displaced by the solid material only, excluding permeable pore space. It is always higher than the bulk values for the same material.

The increase in mass of an aggregate after soaking in water, expressed as a percentage of its oven-dry mass. It indicates the amount of water the permeable pores can take up and must be accounted for in batching.

The distribution of particle sizes in an aggregate, described by the masses passing or retained on a series of sieves. It controls workability, density, and the amount of paste or binder needed in a mixture.

A test in which a dried, weighed aggregate sample is shaken through a nested stack of sieves and the mass retained on each sieve is recorded. Results are reported as percentages passing or retained for each size.

The cumulative percentage of a sample's mass that is finer than a given sieve size. It is calculated from the masses retained on that sieve and all coarser sieves and is the usual way gradation is reported.

A single number obtained by adding the cumulative percentages retained on a specified series of sieves and dividing the sum by 100. It gives a rough index of the coarseness of fine aggregate.

The smallest standard sieve opening through which the entire sample is required to pass, which may be one size larger than the largest sieve on which any material is retained. It governs minimum sample masses and test selection.

The smallest sieve opening through which all of an aggregate sample passes. It differs from nominal maximum size when a small percentage of particles is retained on that sieve.

A stack of standard sieves arranged from coarsest at the top to finest at the bottom, with a pan beneath. The sample is placed in the top sieve and the stack is shaken or vibrated to separate the particles.

Periodic checking of test sieves for damaged openings, loose cloth, and wear, often by visual inspection and measurement of openings with a calibrated gauge. Sieves that fail are removed from service to protect gradation accuracy.

The documented comparison of a measuring instrument or device against a reference standard of known accuracy to establish its correction or confirm its performance. Balances, sieves, and molds all require it at prescribed intervals.

A check, often simpler than full calibration, confirming that equipment still meets specified tolerances, such as a daily balance check with a known mass. It provides evidence that the device remains fit for use.

A material or device of known and stable value, traceable to a recognized authority, used to calibrate or verify test equipment. Examples include certified masses and certified sieve-opening gauges.

The resistance of aggregate to volume change and disintegration when subjected to repeated cycles of wetting and drying or freezing and thawing. It is assessed by tests such as sodium or magnesium sulfate immersion.

A durability test in which aggregate is alternately soaked in a saturated sodium or magnesium sulfate solution and oven-dried for a set number of cycles. The resulting mass loss indicates susceptibility to weathering.

The ability of aggregate to withstand repeated freezing and thawing of absorbed water without cracking or scaling. It is evaluated by cycling saturated samples and measuring mass loss or degradation.

The percentage of mass lost by an aggregate sample when tumbled in a rotating steel drum with a specified charge of steel spheres. It indicates resistance to abrasion and impact and is used in acceptance criteria.

The specified limits and test requirements, such as gradation bands, soundness loss, or abrasion loss, that a material must meet to be approved for a given use. Results are compared against these limits in acceptance decisions.

The determination that test results for a material fall within every applicable limit of the governing specification. Nonconforming results typically trigger retesting or rejection of the lot.

A documented record of who collected, transported, handled, and stored a sample at each step, with dates and signatures. It preserves the traceability of results to the original lot.

The permanent written or electronic documentation of sample identity, test method, equipment used, raw data, calculations, and results. Records must be legible, retained for the required period, and traceable to the test.

The degree to which test results are accurate, precise, complete, and traceable, supported by proper calibration, trained operators, and documented procedures. Poor data quality undermines acceptance decisions and specification compliance.

The clothing and gear worn to protect the laboratory worker, such as safety glasses, dust masks, gloves, and steel-toed boots. It is required when handling aggregates, drying ovens, and chemical solutions.

The practices that protect workers from hazards such as silica dust, hot ovens, heavy sample containers, and corrosive sulfate solutions. They include ventilation, safe lifting, and proper labeling and storage of chemicals.