TEST UNITS – AN OVERVIEW
Aggregates must be clean, hard, dense, durable and frost-resistant, must have stable moisture content and particle size when delivered to the concrete mixing plant, and must not contain iron pyrite, iron oxides, mica, slate, coal or other organic, laminar, soft or porous materials containing vitreous aggregate granules or granules with large voids or other substances that may affect the quality of the concrete, attack the reinforcement or reduce adhesion. In cases of doubt or uncertainty, the effects of substances suspected of being harmful should be determined through testing.
Tests are carried out in accordance with BS, BS EN or ASTM standards. The type of guideline to follow during testing can be selected based on the specification. The following test is most common in the construction industry.
- Sorting fine aggregate.
- Classification of coarse aggregate
- Organic impurities (fine aggregates)
- Total Reduction Value (ACV)
- Overall Impact Value (AIV)
- Scalability Index
- Chloride content
- Sulfate content
- Potential alkali-silica reactivity
- Abrasion resistance
- Elongation Index
- Specific gravity, water absorption
- 10% fine amount
- Moisture content
- solidity
- Point Load Test
- Surface structure and weather resistance
- Loose bulk density
- Classification of coarse raw materials (ABC)
- Harmful materials
- Los Angeles Abrasion Value
- Classification of filter materials
- Breakdown of tensile strength of rock cores
TESTING THE ADDED VALUE OF THE CRUSHER
The aggregate rupture value is an indicator of the rupture resistance of aggregates under increased pressure loads. It is tested in accordance with BS 812:110, 1990. The test considers aggregates that pass through the 14 mm test sieve and remain on the 10 mm sieve. The acceptable range is between 17 and 41.
TESTING THE FLAKINESS INDEX
The coarse aggregate flake index is determined in accordance with the guidelines set out in BS 812 Part 1. Aggregate particles are classified as fluffy if they are less than 0.6 of the average sieve size in thickness. The index is calculated by separating the fluffy particles and expressing their mass as a percentage of the mass of the tested sample. The test is not applicable to material that passes or remains on a 6.3mm BS test screen. The maximum allowable proportion of flaky particles in the mixture is 30%. If this limit is exceeded, the mixture is considered unsuitable for construction purposes. Floc index = (mass of flocculated particles/mass of sample) x 100
