structural plastic fibres for reducing reinforcement in concrete 3

Fiber in concrete is a material enhancement, not a reinforcement. The only gain you get with respect to reducing reinforcement is that the properties of the concrete can become better with fiber addition, though for structural applications, I would look to steel fiber, not polypropylene fiber.

The way it works is that when you add fiber, you increase the strength properties of concrete and provide more resistance to bending and shear. The amount and type of fiber will dictate the actual properties. In that context, you might reduce your computed reinforcement slightly because of the increase in concrete strength properties, but there is not a one-for-one replacement scheme substituting fiber for rebar.

Hey guys, bit of an update for you. Have found a fibre type that claims to give significant increases in the fleural strength of concrete. Have checked the test results and they seem vaild (from a NAMAS (UK) accredited laboratory). We've put these figures into our design calcs for simple units that are subjected to low or no tensile forces (small retaining walls, tunnel segments etc..) and they seem to work in theory. Also have some data on increased shear resistance form some tests done in Germany although to I am dubious about the level of shear resistance they are claiming....
Anyway, I need some help from the guys in the USA - have various results from different manufacturers to ASTM C1018 where toughness indicies are calculated. Is there a set size of section / loading area for these tests, as the graphs only show load against mid-span deflection, therefore if sections sizes vary there is no way for me to compare results.

Thanks - all comments much appreciated!

Scott....the "preferred" standard specimen size for C1018 is 4x4x14 (inches). Most labs have 6x6x20 beam molds so those are more often used in the commercial realm. Either is acceptable under C1018. The test is done using a simple beam in third-point loading.

Request that the supplier provide you with materials testing that goes beyond the toughness index. Get the actual compressive and flexural strength test results if you can.