| 요약2 |
It is generally used crushed sand as alternative fine aggregate for concrete, but its qualities are different from every manufactures, in case of its poor distribution of particles, it is impossible to only use and difficult to quality control for concrete. In this study, for the solution of previous problems, it is tried to positive use the crushed sand that is satisfied KS criteria exception fineness modulus for concrete. The use method of crushed and results of experiment are as follows. (1) Now that FM of crushed sand is high, it is that coarse particles substitute gravel and fine particles substitute sand on the 5mm size(no. 4 sieve). Since the substitute ratio of crushed sand increase, fluidity of fresh concrete is similar or a little decreased to standard mixture, with increase ratio of fine aggregate of concrete mixture. (2) In early age, compressive strength does not varied according to the substitute ratio of crushed sand, but 91 days compressive strength used 80% crushed sand is showd highly. (3) Elastic modulus of concrete is similar to compressive strength, it is inverse proportioned to W/B and decreased to the substitute ratio of crushed sand. (4) The change of length is proportioned to amount of binder, and it decreased according to increase of the substitute ratio, it is judged that the amount of water is decreased that effect to shrinkage and expansion of concrete by fine particles of crushed sand. Therefore, by way of using mixed fine aggregate which is qualities satisfied KS criteria exception for fineness modulus, it is that improve distribution of particle and reduce amount of fine particles for positive use of crushed sand. So the crushed sand is expected economical alternative aggregate and it is appraised to minimized reduction of strength and fluidity of concrete with the method of increase to ratio of fine aggregate for concrete mixture. |