Pathway Material Technical Data

Quality Control 101: What Is a Sieve Analysis and Why Does It Matter?

When selecting aggregate for commercial use, there are a number of tests the product goes through to evaluate its suitability for a certain application. Among these tests is a sieve analysis. A sieve analysis helps companies to evaluate aggregate for use as a quality product in pathway mixes, architectural and decorative precast concrete, epoxy resin applications, epoxy overlay, and much more. We’ve put together a quick summary that highlights the significance of sieve analysis and why it matters to the aggregate industry.   

Evaluating Aggregates for Their Intended Uses

The practice of sieve analysis is especially important for the performance of aggregates in their intended uses. Each of these uses will require a specific size or gradation of aggregate, including the percentage of material allowed for each sieve size in the gradation. This can be critical for the strength of the material, compaction of the aggregate, and the visual aesthetic and surface area of the stone.In other words, the process of sieve analysis assists with the gradation of aggregates.

What Is Gradation in Sieve Analysis?

The gradation of aggregates is the distribution of aggregate particles, by size, within a given sample. The purpose of gradation in this capacity is to enable compatibility of the aggregate with product control requirements, designs, and verification specifications.

Gradation via sieve analysis works particularly well for aggregates because of the shapes of the stones and particles. Material that is not somewhat spherical—say, closer to cylindrical—may not lend to successful sieve analysis.

Sieve Analysis: Step by Step

The procedure of sieve analysis starts with the stacking of sieves, or screens, from the largest to the smallest size. Typically, the mesh of these sizes can range from 1 inch or 25.4 mm to what’s known as the “No. 400” or .037 mm of an opening.

Then, the bulk aggregate is placed carefully on the top sieve and the material is screened through the various sieves and subsequently become separated by size. Aggregates that couldn’t pass through a ⅜” sieve screen, for example, will stay in that sieve while the others pass through until they’re caught in the proper sieve. However, simply dumping your aggregate through sieves is not enough for accurate parsing – that’s what sifters are for.  

Sifting Methods

Depending on your machinery, sifting can be a relatively painless and time-saving process. Mechanical sieve shakers will shake the stacked sieves, causing each stone and particle to fall to its coinciding sieve screen. Note that there are different methods for sifting, common methods include:

  • Horizontal sifting: where the sieves are sifted in a horizontal motion
  • Throw-action: a sieve method whereby vertical force combined with circular motions is applied
  • Air jet: uses a vacuum or other means of creating an air stream to transport and separate finer particles
  • Tap: circular, horizontal motions with frequent tapping  
  • Wet: uses water to support the sieving process, but is a far less common practice than the traditional dry methods  

Once sifted, each sized aggregate is weighed and noted as a percentage of the overall sample—that is, the percent of aggregate retained per sieve is noted as well as the percentage passed through that size (known as the passing aggregate). These details are then recorded, and the quality aggregate is sent for distribution where it will then await its new home. 

An Example: How to Read a Sieve Analysis

In general, specialty crushed stone products must have consistent sizes and fall within acceptable tolerances. For a real-life example of the sieve test as it relates to Kafka’s quality control, we’ll unpack the sieve tests as they pertain to our stabilized pathway mix.

Kafka Granite’s Stabilized Pathway Mix must adhere to specifications as outlined by the binder manufacturer, Organic-Lock.  With the gradation specification, there is an acceptable range and distribution of particle sizes that is to exist within the stone sample. While each sample and sieve will vary slightly, it’s vital that the samples for stabilized pathway mix fall within this range because a success ensures one of two things: the pathway mix is consistently well-graded, and it will compact properly.

Let’s take a closer look at the gradation specification for Stabilized Pathway Mix and how it works. First we must understand what U.S. Mesh sizing is. U.S. Mesh Sizing is defined as the number of openings per one square inch of a screen. Therefore, the larger the number, the smaller the screen size. The example below shows each sieve size translated to metric sizing, but you can also use a helpful screen size / sieve conversion chart

The first pass calls for 80-100% passing the #4 mesh screen. In other words, 80-100% of stone particles must fall through a #4 mesh screen. Then, 65-90% of the stone particles should pass through an #8 mesh screen. You can see the rest of the required pass percentages in the below table. Once you reach the bottom of the chart, you’ll see that 5-15% of the stone particles should fall through the #200 mesh screen, which is an extremely fine, dust-like material.. If this were a “clean” or “chip” aggregate, there would not be such fine material included in the mix. 

Sieve Sieve Size (mm) Percent Passing
4 4.75 80%-100%
8 2.36 65%-90%
16 1.18 40%-65%
30 0.6 25%-55%
50 0.3 15%-35%
100 0.15 10%-20%
200 0.075 5%-15%

 

It is important that the pathway mix meets the gradation requirement above; it is vital for the product’s functionality. In order for the binder to work properly, the surface to compact, and rain water to drain, the gradation must be consistent and within the defined tolerances.

This is, of course, just one of many sieve analyses we run at Kafka to check a product’s gradation, and only one of many tests used to analyze quality. Contact us to request a sieve analysis or other product information.

High Friction Surfacing

The Benefits of High-Friction Surfacing

Every four years, the ASCE Committee on America’s Infrastructure issues a report card grading the country’s many categories of infrastructure. In 2013, we received an overall grade of D+. In 2017, the country received the same grade—but the transit sector actually suffered, dropping from an individual grade of D to D-. Today, more than ever, America’s roadways need help. Businesses like Kafka Granite are developing solutions to issues like slippery bridges and deteriorating highways.

Whether you’re a Department of Transportation decision-maker or a contractor sourcing materials for a roadway project, you’ve probably come across high-friction surfacing treatments. High-friction surfacing is used to improve traction on bridge decks, entrance/exit ramps, curves, overpasses, and more. But it doesn’t just improve driving conditions—it also saves lives. Let’s take a closer look at the advantages of this treatment.

6 Advantages of High-Friction Surfacing

1. Increased Traction

High-friction surfacing consists of a layer of two-part epoxy topped with a hard, fractured aggregate. The most significant benefit of this roadway treatment is the increased traction it offers when applied to roadways, bridge decks, and other high-crash locations. With proper surface preparation, non-skid surfacing epoxy overlays can be used to improve driving conditions on pre-existing roadways and new installations alike.

2. Safer Driving

That increased traction helps vehicles stay on the road, which is essential when winter weather, low temperatures, and even simple rainstorms create slippery driving conditions. Bridge decks, in particular, are prone to ice, as cold temperatures from below cause these areas to freeze faster than the rest of the roadway. Ultimately, high-friction surfacing allows tires to better grip a hardscape, which helps cars, trucks, and other moving vehicles navigate potentially dangerous conditions and high-risk areas of the road.

3. More Efficient Deicing

In addition to improving driving conditions upon installation, non-slip aggregates like Kafka Granite’s also help to improve the condition of the road itself. The aggregate in high-friction surfacing traps road salt, resulting in a quicker, more effective deicing process. This is particularly useful in areas of the country that experience extreme winter weather, such as the Midwest.

4. Durability

High-friction surfacing is better able to withstand the day-to-day forces of heavy traffic, the freeze/thaw cycle, and other weathering forces that would otherwise cause significant deterioration in a roadway. This is all thanks to the extremely hard non-slip aggregates used in this kind of surface treatment.

5. Cost Savings

High-friction surfacing may require an initial investment, but it more than makes up for this cost when you consider the lifecycle of the installation and the mounting costs of America’s many deficient roadways. These treatments can last for approximately 10 years, saving motorists and the government significant funds over that period. Additionally, after the aggregate has set, the excess material can be collected and reused in another project, ensuring that you get the most out of your investment.

6. Quick Installation

Halting or altering the flow of traffic is a major concern for DOT projects. A huge amount of work goes into simply setting up a project site with appropriate signage, lighting, lowered speed limits, and more. Ultimately, the faster a project can be completed, the better. High-friction surfacing fits neatly into this mindset, as treatments can often be installed over the course of a few hours.

Surface preparation is essential to a successful installation, however. First, the pre-existing hardscape must be cleaned and inspected for damage like cracks and breakage. Once any damage has been repaired, the area may also need to be scarified with a grinder to facilitate the adhesion of the epoxy.

Non-Slip Aggregates for High-Friction Surfacing

A consistent, high-quality aggregate is crucial for a lasting high-friction surfacing treatment. Kafka Granite has supplied aggregate for these projects across the United States. We offer a selection of extremely hard aggregates that will hold up under heavy traffic, intense freeze/thaw cycles, snowplow usage, and more. We’ve worked with a number of state DOT offices and are fully prepared to supply aggregate that meets your specifications.

Our quartz, granite, and recycled materials are available in over 40 colors, meaning that we can match any aesthetic and even allow you to distinguish sections of the road for bike paths, crosswalks, pedestrian walkways, and other demarkation projects. Our non-slip aggregates are also ideal for use in more decorative epoxy overlay streetscapes.

Installing High-Friction Surfacing? Partner with Kafka Granite!

Kafka Granite is dedicated to doing our part in making America’s roadways safer and more efficient. We’re extremely proud to have provided high-quality aggregate for high-friction surfacing projects across the nation.

If you’re looking for a non-skid aggregate that can be customized to your project needs and Department of Transportation requirements, contact Kafka Granite today. Our knowledgeable sales team will be happy to help you source the perfect aggregate and get to work improving your roadways and streetscapes.