The concrete in which more than one fiber types are used as
secondary reinforcement is called hybrid fiber reinforced
concrete.
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Glass fibres do not rust like steel reinforment can and they
meld togeter like fiber glass dose, they (if mixed properly, for at
least 10 mins beforehand) are more consistent throughout the mix
too. Allow one bag of XT fibres (cost about £6 each) per cubic
meter of concrete. Regards Colin