Brittleness Of High Strength Concrete And Measures Studied Of Reducing The Brittleness And Increasing The Toughness Of Concrete

With the developing of concrete technology, the strength of concrete has been increasing; With the ascending of building and the increasing of span of construction, The higher ability of buildings to resist dynamic load is needed; With the application of high strength concrete, even super high strength concrete, the brittleness of concrete is becoming even serious. So the studies of reducing the brittleness and increasing the toughness have important fact sense.The author refers to lots of literature about the fracture performance of concrete and summarizes the reason why concrete is brittle. The conclusions are that the type of chemic key in concrete easily arise the brittle fracture of concrete, and the linear and plane inherent vice is easy to lead concrete to brittle fracture, and concrete, especially high strength and super high strength concrete, is sensitive to nick and is poor to relax the stress concentration. Aiming at the season above, the author think the approach to reduce the brittleness and increase the toughness of concrete is that: first, shortening strength difference between "three portion" , in order to avoid fracture ahead of time from one portion; secondly, making the best of dispelling the linear and plane inherent vice, in order to lessen the chance of arousing stress concentration at few vice; thirdly, slowing the proceeding of unsteadily extending of crack, this is the key; finally, increasing the point in concrete to consume energy can advance the ability of resisting dynamic load of concrete.The author successfully makes the high-fluidity and high compressive strength concrete with 90 MPa of 28 days age by adopting universal construction techniques and using common raw and processed materials. Basing on the concrete, the author investigates the fracture performance of fiber concrete and rubber powder concrete. The test results show: Polypropylene-fiber not only keeps the good construction performance, but also can reduce the brittleness and increase the toughness of concrete. Although steel-fiber has better effect on the toughness of concrete, it has disadvantageous effect on the construction performance of concrete. The rubber crushed by machine is mixed to the concrete. The rubber powder has some good impact on the toughness of concrete, especially can restrain the cracking of concrete before hardening. When dynamic load is impacted on concrete, the rubber powder can absorb plentiful kinetic energy and improve the ability of resisting dynamic load.