Impact Value of Aggregate procedure, Limits

Determination of Impact Value of Aggregate

What is the impact value of aggregate?

The effect cost of a combination enables us to evaluate its suitability to be used in production, as aggregates with higher impact values are taken into consideration as much less durable and more liable to cracking beneath sudden masses, which may additionally affect the first-class of production. and Also, may affect sturdiness. Lower impact values indicate better overall quality and stability.

The aggregate impact value used in?

The acceptable aggregate impact value for a specific construction project varies depending on regional standards and the type of construction. For example, in some regions, for road construction, an aggregate impact value below 30% is often considered suitable. However, for certain specialized applications, like high-strength concrete, lower values may be required, often below 15%. It’s crucial to refer to local construction codes, standards, or project specifications to determine the precise range of acceptable aggregate impact values for a given project.

impact value of aggregate satisfactory for road surfacing 

The perfect range for the effect price of aggregates used in street surfacing can vary depending on a vicinity’s precise requirements and regulations. In many instances, the appropriate variety falls within the limits of 20% to 30% However, it’s important to consult the relevant industry standards, such as BS 812: Part 112, or  ASTM C131, the acceptable range for the impact value of aggregates used in road surfacing typically falls within the limits of 30% as the maximum allowable value. The standards specific to your region, to determine the exact acceptable range for aggregate impact values in road surfacing applications.


The effect value of aggregate is a critical parameter that determines the energy and sturdiness of concrete structures. It presents data about the capacity of aggregates to withstand unexpected shocks or effect masses. This test is enormous for assessing the high-quality and suitability of aggregates in construction packages, ensuring the protection and sturdiness of infrastructure.


The experiment follows the requirements set via ASTM C131 and BS 812: Part 112.


The experiment pursues to decide the effect cost of aggregates, especially coarse aggregates, with the use of the Aggregate Impact Testing Machine. It specializes in evaluating the resistance of aggregates to surprising shocks and effects.


This experiment ambitions to evaluate the best and suitability of coarse aggregates by way of figuring out their impact value. The impact cost suggests the mixture’s potential to face up to effect masses, thereby helping in the selection of suitable aggregates for production functions.


  • To determine the impact value of the given coarse aggregate sample.
  • To compare the obtained impact value with the specified limits to evaluate the aggregate quality.
  • To make recommendations based on the impact value for selecting suitable aggregates in construction.


  • Aggregate Impact Testing Machine: Consisting of a circular base with vertical publications and a hammer of thirteen.Five to 14 kg mass.
  • Cylindrical metallic degree with an inner diameter of 75 mm and a height of fifty mm.
  • Tamping rod: Made of metal, with a diameter of 10 mm and duration of 230 mm.
  • Sieves: 12.5 mm, 10 mm, and a couple of.36 mm.
  • Balance: Capable of weighing up to one kg with an accuracy of one gram.


A standard amount of impact under controlled conditions determines the impact value of the aggregate by subjecting the aggregate sample to it. The tamping rod fills and compacts the aggregate in the cylindrical measure. The testing machine then places the measure, with the aggregate in it. An impact load is exerted by releasing a hammer from a known height to strike the aggregate. The impact value is calculated as the resulting percentage of fines generated.



  • Collect the aggregate pattern passing via a 12.5 mm sieve and retained on a 10 mm sieve.
  • Oven-dry the sample to constant weight at a temperature of 110°C.
  • Weigh the dried sample and vicinity it within the cylindrical measure, filling it in 3 layers, and tamping each layer 25 instances using the tamping rod.
  • Scrape off excess aggregate above the level of the measure using a straight edge.
  • Place the measure containing the compacted aggregate in the testing machine and level it.
  • Release the hammer from a height of 380 mm above the aggregate, striking the upper surface.
  • Sieve the combination through a 2.36 mm sieve, and weigh the fines passing through.
  • Calculate the share of fines generated because the impact price the use of the formula: Impact Value = (Weight of Fines/Weight of Sample) × 100


Impact Value = (Weight of Fines/Weight of Sample) × 100

Limits for impact value of aggregates

The specified limits for the impact value of aggregates vary depending on the type of application and the relevant standards. As an illustration, according to ASTM C131, the maximum allowable impact value for a base course aggregate utilized in highway construction stands at 50%. In a parallel manner, BS 812: Part 112 dictates that the maximum allowable impact value for a 20 mm aggregate employed in road surfacing is 25%.

The limits for impact value vary depending on the type of aggregate and its intended use. Here are some commonly used limits as per ASTM C131 and BS 812: Part 112:

  1. For base course and wearing course aggregates
    • Maximum impact value: 30%
    • Minimum impact value for heavy-duty concrete pavements: 20%
  2. For bituminous macadam and bituminous concrete:
    • Maximum impact value: 35%

Minimum Limit: The impact value should not exceed a specified minimum limit, typically around 15% to 20%. This ensures that the aggregates have sufficient strength and resistance to sudden shocks or impacts.

Maximum Limit: The impact value should not exceed a certain maximum limit, usually ranging from 30% to 45%. Exceeding this limit indicates that the aggregates are weak and prone to breakage or fragmentation under impact loads.


We evaluated to determine the impact value of the aggregate sample. Furthermore, by conducting a meticulous comparison of this value with the specified limits as defined in relevant standards, we can effectively and definitively establish whether the aggregate quality aligns with the acceptance criteria or not. Additionally, it’s vital to emphasize that this assessment plays a central role in ensuring that our materials consistently adhere to the set criteria of industry regulations. With the determined impact value, we can provide well-informed recommendations for the selection and utilization of aggregates in construction projects, guaranteeing the desired strength and durability of concrete structures.


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