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  • Scott Allen

Understanding the Concept: What Does 95% Compaction Mean?

Introduction We always get the question here at AllRock, “So what does 95% compaction actually mean”. It seems there is a lot of confusion around percentage compaction, proctors and nuclear density gauges, so we’ve written this blog post to help shed some light on the topic!

The term 'compaction' is often used in construction, civil engineering, and soil science. It refers to the process of increasing the density of a material by reducing the air gaps between its particles. This is usually achieved through pressure application or vibration. Compaction is crucial in construction projects as it enhances the strength and stability of structures. One term that often comes up in this context is '95% compaction'. But what does 95% compaction mean? This blog post will delve into this concept and explain its significance in construction projects.


Active quarry producing construction aggregates
Active quarry producing construction aggregates

Understanding Compaction Testing Before we delve into what 95% compaction means, it's crucial to understand compaction testing. This process involves determining the optimal moisture content that would allow a soil type to reach maximum dry density. The test results are crucial for construction projects as they help engineers determine how much compaction is needed for a particular type of soil. Compaction testing typically involves two methods: Standard Proctor Test (SPT) and Modified Proctor Test (MPT). The SPT is generally used for lighter compactions like pavements and highways, while MPT is used for heavier compactions like dams and embankments. The Meaning of 95% Compaction Now, let's get back to our main question - what does 95% compaction mean? In simple terms, when we say a soil sample has achieved 95% compaction, it means that the compacted soil has reached 95% of its maximum possible dry density as determined by a Proctor test. Proctor testing is a test performed in the laboratory that compares the density of a soil sample to various moisture contents. At the end of the test you get a point where the soil yields its optimum moisture content, and a maximum dry density. In other words, if a Proctor test determines that the maximum dry density of a particular soil type is 120 pounds per cubic foot (PCF), achieving 95% compaction would mean compacting that soil until it reaches a density of 114 PCF (i.e., 95% of 120 PCF).

AllRock completes proctor’s and other soil testing in London, Ottawa, Toronto and Newfoundland and Labrador laboratories. Check out AllRock’s soil testing services here https://www.allrockconsulting.com/soil-testing. The Significance of Achieving 95% Compaction Achieving high levels of compaction is essential in construction projects because it significantly increases the strength and stability of structures. When you compact soil to about 95%, you minimize its tendency to settle under load or change volume with moisture content variations. Therefore, achieving at least 95% compaction ensures that your structure will have a solid foundation capable of withstanding various loads without undergoing significant settlement or deformation. However, it's important to note that while achieving high levels of compaction is desirable, over-compacting can be counterproductive. Over-compacting can lead to an increase in water retention capacity which could potentially weaken the structure over time due to increased water pressure. Wherever your project is, soil testing in Ottawa, London or Toronto is very important to the longevity of the infrastructure above it. How Is The Percentage Of Compaction Determined? To determine whether you've achieved your desired level of compaction (e.g., 95%), you need to conduct field density tests on your compacted soils. These tests involve extracting samples from different depths within your compacted soils and determining their densities using methods such nuclear gauge method or sand cone method. Whether you are completing soil compaction testing in Toronto, London or Ottawa the nuclear gauge method is generally the preferred method in Canada.

We also wrote a post on Geotechnical Engineering that can provide further relevant information on soil testing, check it out here! https://www.allrockconsulting.com/post/the-foundation-for-your-project-s-success, By comparing these field densities with your maximum dry densities obtained from your Proctor tests, you can calculate your percentage compactions.



Uncompacted soil & aggregate in a parking lot
Uncompacted soil & aggregate in a parking lot

Conclusion In conclusion, understanding what 'compacting at least up to 95%' means plays an essential role in ensuring successful construction projects. It helps engineers ensure they're providing stable foundations for their structures while avoiding potential problems associated with over-compacting or under-compacting their soils. Remember always to conduct thorough compaction testing before starting any construction project - this will not only ensure structural stability but also save you from potential costly repairs down the line due to poor foundation performance.

Check out AllRock’s other geotechnical services here https://www.allrockconsulting.com/geotechnical-engineering

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