Apparent Opening Size (AOS) Tester
Apparent Opening Size Testers for Geotextiles | ASTM D4751
Geotextile filtration performance depends on the size of the openings within the fabric. The QualiGTX™ Apparent Opening Size (AOS) Tester evaluates this property by passing graded glass beads through a geotextile under dry sieving conditions. The resulting O95 value represents the approximate largest soil particle that can pass through the fabric, giving engineers a basis for assessing its ability to retain soil while maintaining water flow.
Specified in ASTM D4751, this test provides essential data for selecting geotextiles used in filtration and separation systems. Highway construction projects, geotextile manufacturers, and independent testing laboratories use these measurements to verify material characteristics, assess product consistency, and determine suitability for specific soil conditions.
To accommodate different testing workloads and laboratory setups, Qualitest offers three models in the QualiGTX™ AOS Tester series. All configurations follow the same dry sieving procedure for single-layer geotextiles and related products. The available models differ in their operating systems, number of specimens handled per batch, and overall equipment footprint, allowing laboratories to select a configuration that matches their testing requirements.
Applications
Accurate apparent opening size measurements help determine whether a geotextile provides the required balance between soil retention and water passage. These results are important when selecting filtration, separation, and stabilization materials for construction and environmental projects.
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Highway and Airfield Construction: Evaluates whether separation geotextiles prevent fine subgrade particles from migrating into the granular base layer under traffic loads, helping maintain the separation between pavement foundation materials.
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Geotextile Manufacturing Quality Control: Checks finished fabric rolls against their specified O95 values, allowing manufacturers to verify that production materials meet the pore-size requirements stated in product data sheets.
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Drainage and Filter Design: Provides the apparent opening size measurements engineers need to compare with soil d85 values when selecting geotextiles for drainage and filtration applications.
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Dams, Canals, and Levees: Assesses geotextile filter materials used behind riprap, beneath revetment structures, and around toe drainage systems, where soil retention and water movement must work together.
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Erosion and Sediment Control: Determines whether silt fences, scour protection aprons, and slope stabilization fabrics have suitable opening sizes before they are installed at construction and erosion-control sites.
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Landfill and Containment Systems: Verifies pore-size characteristics of filtration and cushioning geotextiles used in leachate collection systems and landfill cover assemblies.
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Independent Testing Laboratories: Supports routine apparent opening size testing for material specifications, regulatory requirements, and certification programs.
Apparent Opening Size Tester Range
The QualiGTX™ AOS series includes three models designed for different laboratory workloads, from periodic material verification to high-volume incoming quality inspections. All configurations feature a 200 mm sieve column, a 400 mm stack height, and a 0.37 kW drive, providing a consistent testing arrangement across the product range.
| Model | Control | Capacity and Accessories | Size and Weight | Best Suited To |
|---|---|---|---|---|
| QualiGTX™ AOS T | Color touchscreen | 5 specimens per cycle; 5 pressing rings and a graded glass bead set included; low-noise drive | 700 × 620 × 1360 mm, 160 kg | Designed for laboratories handling regular incoming material inspections, with guided touchscreen operation for consistent results across operators. Its low-noise drive also makes it suitable for shared laboratory spaces where quieter equipment operation is preferred. |
| QualiGTX™ AOS M | Manual controls | 5 specimens per cycle; 5 pressing rings, 5 stainless steel sieve pans, and a graded glass bead set included | 770 × 650 × 1060 mm, 80 kg | Suited to laboratories processing five specimens per batch that need separate bead collection for each sample and individual weighing after testing. Manual controls provide straightforward operation without the complexity of a programmable interface. |
| QualiGTX™ AOS DSM | Motorized shaker | Standard sieve column configuration | 750 × 480 × 850 mm, 70 kg | Designed for laboratories with restricted bench or floor space, particularly where AOS testing is performed periodically as part of a broader geosynthetic testing program. Its compact, lightweight construction provides a practical solution without requiring dedicated space for frequent testing. |
How to Choose the Right Apparent Opening Size Tester
Selecting the appropriate AOS tester depends on specimen throughput, operating preferences, available laboratory space, and testing frequency.
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For high-volume testing and multiple operators: The QualiGTX™ AOS T features touchscreen operation, helping maintain consistent testing procedures across different operators and work shifts.
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For batches of five specimens with straightforward operation: The QualiGTX™ AOS M combines manual controls with stainless steel collection pans. These pans keep the glass beads from each specimen separate, allowing individual weighing after testing.
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For laboratories with limited floor space: The QualiGTX™ AOS DSM offers the most compact and lightweight configuration in the series, weighing just 70 kg.
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For shared laboratory and sample preparation areas: The QualiGTX™ AOS T uses a low-noise drive to minimize the tapping sounds commonly associated with conventional sieve shakers.
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For occasional testing and material verification: The QualiGTX™ AOS DSM provides the required testing method in a compact configuration, with the lowest equipment footprint and cost of ownership in the range.
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Before placing an order: Verify electrical compatibility with your laboratory's power supply. All three models are specified for 380 V operation.
Why Choose Qualitest for Your Apparent Opening Size Tester
Qualitest North America provides testing and measurement equipment for manufacturers, quality control departments, and independent laboratories, supported by responsive technical assistance and calibration services.
The QualiGTX™ Apparent Opening Size Tester series is designed to deliver dependable measurements in accordance with established testing procedures. With three configurations available, Qualitest helps laboratories select equipment that matches their specimen requirements, applicable standards, and testing workloads.
From choosing the appropriate model to installation and ongoing technical assistance, our team provides support throughout the equipment ownership process.
Request a Quote
Whether you need an AOS tester for periodic geotextile verification or continuous incoming material inspection, Qualitest can help identify the right configuration for your laboratory. Share your geotextile types, expected monthly testing volume, and available installation space so our team can recommend a suitable model.
Contact the Qualitest team for pricing information and current lead times.
