Title:
Comparative Evaluation of Fiber Shotcrete
Author(s):
V. Ramakrishnan
Publication:
Concrete International
Volume:
3
Issue:
1
Appears on pages(s):
59-69
Keywords:
compression tests; deformed reinforce-flent;
fibers; flexural tests; impact resistance;
modulus of elasticity; shotcrete; tests.
DOI:
Date:
1/1/1981
Abstract:
This report presents a comparative evaluation of the performance characteristics of fiber shotcretes with four types of steel fibers. The fibers used were two types of collated fibers with deformed ends, straight fibers, and cut steel tire cord. Three different fiber concentrations were used at 0.6, l.& and 1.3 percent. The dry-process sanded mix shotcrete with an assumed water-cement ratio of 0.46 and 5 percent entrapped air was used in this investigation. Using a well-established shotcreting company and quality equipment, and a nozzle operator with 18 years of shotcreting experience, 36 test panels were made with 1% in. (38 mm) and 3 in. (76 mm) thicknesses. Test panels were shot in a raised vertical position against rigid plywood forms with open bottoms. Saw and core samples were made from the test panels and the following tests were conducted: (1) cube compression test including unit weight; (2) flexural est including load-deflection curves; (3) impact test; (4) shrinkage measurements; and (5) pulse velocity and dynamic modulus of elasticity tests. One- major finding is that collated fibers with hooked ends could be effectively used in shotcreting and that they perform well. Excellent distribution of fibers was noted from the x-ray photos. All of the fiber shotcretes showed a tremendous ability to absorb impact loading; the hooked fibers showing a far superior ability than the straight fibers. The static flexural test shows that an excellent end anchorage is established in the case of the hooked fibers resulting in a high ductility of the shotcrete. For the three fiber concentrations used, only a slight improvement was recorded in the properties of the hardened shotcretes.