Final answer:
Engineered cementitious composites (ECC) are true to not contain gravel. Instead, ECC comprises fine aggregates and fly ash that improve its flexibility and durability, outperforming traditional concrete in terms of tensile strength and crack resistance.
Step-by-step explanation:
The statement that engineered cementitious composites (ECC) do not contain gravel is true. ECC is a type of high-performance fiber-reinforced cementitious composite that is specifically designed to exhibit enhanced flexural performance and strain-hardening behavior. Unlike traditional concrete, which is a mixture of cement, sand, gravel, and water, ECC has a microstructure that is optimized to control crack width and improve durability.
Instead of gravel, ECC typically contains fine aggregates and a high volume of fly ash, which is an industrial byproduct from coal combustion. Fly ash acts not only as a replacement for cement, thus reducing the carbon footprint of the material, but also enhances the mechanical properties and durability of ECC. This makes ECC an ideal choice for projects requiring materials with improved tensile strength, ductility, and resistance to cracking.
Unlike traditional concrete, ECC does not rely on aggregates like gravel or fly ash. Instead, it achieves its superior properties through the addition of fibers, such as steel or synthetic fibers, which improve crack resistance and energy absorption.
Therefore, ECC does not contain fly ash, but rather incorporates cement, fine sand, and fibers to enhance its mechanical properties.