ASTM D5298 Standard Test Method for Measurement of Soil Potential (Suction) Using Filter Paper (Withdrawn 2025)

ASTM D5298 Introduction

ASTM D5298 is an alternative to the direct suction measure. It entailed weighing a standard filter paper to a constant weight in a restricted setting with a soil sample and calculating suction using the water content of the filter paper. In the unsaturated soil, soil suction, also called matric potential, is used to describe the energy state of water in the soil and plays a central role in the study of unsaturated soil. It determines important processes like the shear strength, permeability, the changes in volume, and uptake by the plants. This method proved particularly handy due to its ease of operation, cheapness, and its extensive versatility in areas where advanced devices were not readily available.

ASTM D5298 Test Method

ASTM D5298 Equipment and Sample Preparation

ASTM D5298 Results and Interpretation

The filter paper method is a quantitative method for measuring soil suction on a large scale (10 kPa to > 100 MPa). The contact method gives lower suction values, and the non-contact method captures higher values. Precise results are influenced by precise calibration curves and balancing the conditions. The pore water pressure is measured and used to characterize the soil-water characteristic curve (SWCC), an important input in unsaturated soil mechanics and finite element modeling of soil behavior. The method is quite variable, though it has been one of the most feasible methods to measure broad suction.

ASTM D5298 Related Test Methods

ASTM D6836 gives test methods to establish the soil-water characteristic curve by applying pressure cells and chilled-mirror hygrometer instruments. The drying method to measure the moisture content of soils, specified in ASTM D3152, is often performed together with suction measurements as a combination useful in describing the soil-water retention behavior.

ASTM D5298 Applications in Industry 

This approach was very common in the geotechnical engineering field in the estimation of slope stability, foundation design, and analysis of unsaturated soils. In its application, it enhanced irrigation schemes and studies in the plant-to-water correlation in agriculture. It also played a role in environmental engineering, including the design and analysis of municipal landfill covers, unsaturated flow modelling, and the transportation of contaminants. The filter paper method remains referenced in soil studies as a relatively inexpensive, available alternative despite its no longer being used.

ASTM D5298 Materials Commonly Tested

The given procedure could be employed in many soils (clays, silts, and sands). It was particularly applicable to fine-grained soils, and suction contributed heavily to both the strength and hydraulic properties. Compacted soil tested through the laboratory and segregated field samples were the most common practices.

ASTM D5298 Common Challenges and Troubleshooting

Precise weighing filter papers, airtight sealing during equilibration, and reduced contamination were the main issues. This may reflect results, as there may be variability in the type of filter paper used, its handling, or the reliability of the calibration. 

ASTM D5298 Safety and Best Practices

Although the method had minimal safety risks, the accuracy required considerable diligence from an operator. It was recommended to carry out calibration checks and duplicate tests to get good results.

Importance of ASTM D5298 Test Method

This method was very important to the development of understanding unsaturated soil mechanics and how soil-water systems behave. It was cheap and straightforward, hence accessible to researchers and engineers all over the world. It is still a milestone in determining soil suction today, contributing to the present-day test methods and geotechnical work.