ABSTRACT
Geosynthetic Cementitious Composite Mats (GCCMs) are factory-assembled geosynthetic composites consisting of a cementitious material contained within layers of geosynthetics that becomes hardened when hydrated, and are primarily used to replace conventional concrete for erosion control and weed suppression applications. GCCMs are unique geosynthetic materials as their properties change from flexible to rigid once cured and in service. The cured cementitious layer also provides inherent physical properties to the GCCM including its compressive strength, initial (1st crack) flexural strength and abrasion resistance. Assessing the performance of the cementitious layer within a GCCM typically falls outside the scope of conventional geosynthetic test standards. Similarly, testing of GCCM cementitious materials to conventional concrete standards at optimum water/cement ratios can also be unrealistic of in service GCCM performance, as the water applied in hydration is not controlled and GCCMs often cure in immersed conditions, increasing the water/cement ratio and decreasing the compressive strength of the cementitious layer. If a designer does not understand the test conditions that GCCM manufacturers have used to report their physical properties, there is a risk that they can specify an unsuitable GCCM material for their project. ASTM D8364 ‘Standard Specification for GCCM Materials’ was published in March 2021 and provides assurance to designers of GCCM applications. This paper provides an assessment of ASTM D8364, reviewing the GCCM performance properties listed in the Classifications for GCCMs table and the importance of testing to the specified standards. Particular focus is given to why all GCCMs specimens should be cured by hydration by full immersion to ADTM D8030 and why the compressive strength should be determined to the GCCM specific test methodology in ASTM D8329. By specifying GCCM Classification Types to ASTM D8364, designers can protect themselves from using GCCM test data that may not be representative of in field GCCM performance.
