The aggregate gradation describes the distribution of the particle sizes in a certain sample and determines aggregate quality. Dense Graded Aggregate (DGA) This gradation contains a wide range of different sizes of aggregates. Voids created by larger rocks are filled by smaller rocks and fines.
Alkali-aggregate reaction is the term mainly referred to a reaction which occurs over time in concrete between the highly alkaline cement paste and non-crystalline silicon dioxide, which is found in many common aggregates. This reaction can cause expansion of the altered aggregate, leading to spalling and loss of strength of the concrete.
The total chloride content of aggregate is usually measured to assess whether the aggregate’s contribution to the total chloride content of a concrete mix will be low enough to prevent the early onset of corrosion of any embedded steel reinforcement.
This test helps in determining the percentage of clay lumps and friable particles in aggregate. Clay lumps in aggregate shall be defined as any particles or aggregation of particles which when thoroughly wet can be distorted when squeezed between the thumb and forefinger, or will disintegrate into individual grain sizes when immersed for a short period in water. Friable particles are defined as particles which vary from the basic aggregate particles such, that they may either readily disintegrate under normal handling and mixing pressures, imposed upon them by construction procedures, or break down after being incorporated into the work.
This test helps in determining the size of a granular material. The size distribution is often of critical importance to the way the material performs in use. A sieve analysis can be performed on any type of non-organic or organic granular material including sand, crushed rock, clay, granite, fled-spars, coal and soil, a wide range of manufactured powders, grain and seeds, down to a minimum size depending on the exact method. Being such a simple technique of particle sizing, it is probably the most commonly used to date.
This test helps in determining the compaction percentage of an aggregate when loose compared to the same aggregate compacted in a standard manner. It is useful in assessing an aggregate when placed loosely, for example, as a pipe surround material. Aggregate suitable for use as pipe bedding would display a low compaction fraction, indicating it reaches a state of near full compaction under loose placement.
This test helps in determining the presence of organic compounds aggregated to use in cement mortar or concrete. The test provides a quick, relative measure to determine if further tests of the fine aggregate are necessary before approval for use.
