Properties of GFRC
The following properties are essential in the performance of any GFRC material: tensile and flexural strengths, modulus of elasticity, compressive strength, impact resistance, shear strength, shrinkage and moisture movement, fire endurance, acoustical properties, thermal conductivity, permeability and moisture absorption.
There is no specific standard for each of these properties; their values depend on the particular need of the project. Each manufacturer or designer must test the composites used to establish the physical properties for the design. These values will depend on different factors like mix design, quality of materials used, manufacturing process and type of curing among others.
There are several factors affecting the physical properties of the GFRC. These factors include the following: fiber content, porosity, water-cement ratio, composite density, sand content, fiber orientation and length, and type of cure. Understanding these factors and their corresponding effects on the properties is essential in the design of GFRC materials.
Fiber length, fiber content and orientation affect tensile strength, flexural strength and impact strength. Basically higher fiber length and fiber content result to higher ultimate tensile, flexural and impact strengths. The fiber orientation also affects the performance of the GFRC material. Most GFRC have random two-dimensional fiber orientation. This factor can be regulated while spraying the GFRC. The fiber orientation determines the fiber resistance to loads.
Density and porosity are affected by the degree of compaction of GFRC. Composite density also affects the flexural strength and tensile strength. The modulus of elasticity also varies directly with the composite density. Lower composite density results to lower ultimate strengths. This is because at lower densities, air trapped in the GFRC reduces the bond between the fiber material and concrete. Thus, proper compaction is necessary to ensure that GFRC has high ultimate strengths.
The type of curing process performed on the GFRC manufacturing also affects the properties of GFRC. Adequate curing is necessary for the hydration of the cement, resulting to a good bond between the fiber and the cement matrix. This improves the fiber and matrix-dependent properties of GFRC like ultimate strengths.