AASHTO M145
Full Name
AASHTO M145 – Standard Specification for Classification of Soils and Soil-Aggregate Mixtures for Highway Construction Purposes
Scope
AASHTO M145 is a standard specification that outlines a system for classifying soils and soil-aggregate mixtures used in highway construction. This classification system is crucial for evaluating the suitability of these materials for various applications within a highway project, such as embankments, subgrades, subbases, and bases.
Key aspects of AASHTO M145:
- Classification criteria: the classification system is based on laboratory tests that determine the particle-size distribution (gradation), liquid limit, and plasticity index of the soil or soil-aggregate mixture.
- Soil groups: the system categorizes soils into seven primary groups (A-1 through A-7), each with potential subgroups. These groups represent a spectrum from coarse-grained soils (e.g., gravels and sands) to fine-grained soils (e.g., silts and clays).
- Group index: within each group, a numerical value called the “group index” is calculated using an empirical formula. The group index provides a more detailed assessment of the soil’s engineering properties and its relative quality for specific highway applications.
- Applications: the classification system and group index information help engineers select appropriate materials for different layers of a highway pavement structure. For instance, well-graded granular materials (e.g., A-1, A-2) are often preferred for base and subbase layers due to their good drainage and load-bearing capacity.
Significance of AASHTO M145:
- Standardized evaluation: the standard practice provides a consistent and objective method for evaluating soil and soil-aggregate materials across different projects and regions.
- Informed decision-making: the classification system and group index data assist engineers in making informed decisions about material selection, pavement design, and construction techniques. This contributes to the overall performance, durability, and longevity of highway infrastructure.
- Quality control: by classifying materials according to AASHTO M145, construction teams can ensure that the materials used in a project meet the specified requirements and quality standards.
AASHTO M145 Accredited Laboratory
Applied Testing & Geosciences, LLC is accredited for performing tests using the AASHTO M145 standard.
Our laboratory offers comprehensive testing services for soils and soil-aggregate mixtures based on AASHTO M145 and other relevant standards. Our experienced technicians conduct precise laboratory tests to determine the classification and group index of your materials, providing you with valuable data for your highway construction projects.
Contact us for more information.
Resources
Keywords
soil; plasticity index; liquid limit; sieve analysis; group index; soil classification; soil groups; aggregate; embankment; subgrade; subbase; base; highway construction; granular material; fine-grained soil; particle size distribution