Some mechanical properties of normal and recycled aggregate concretes

This paper describes an experimental study conducted to investigate the properties of concretes produced with recycled aggregates and normal aggregates for two different concrete classes (C20/25, C30/37). Tests of compressive strength, splitting tensile strength, ultrasonic pulse velocity, rebound hammer, wet and dry density and freeze-thaw resistance were conducted on specimens of the concretes. Moreover slump test was conducted on fresh concrete. The results showed that the slump of recycled aggregate concrete (RAC) was less than that of normal aggregate concrete (NAC). For class C20/25, the average compressive strength, rebound hammer and density of the RAC were 26%, 17% and 16.6% less, respectively, than those of NAC. The splitting tensile strength of RAC was 3.5% greater that of NAC. Moreover for C30/37 the average compressive strength, splitting tensile strength, rebound hammer and density of the RAC were 32.5%, 12%, 21% and30% less, respectively, than those of NAC. For class C20/25 and class C30/37 the ultrasonic pulse velocity of RAC was 17% and 18% smaller than that of NAC, respectively. RAC for C20/25 lost 2.5% more weight than NAC in freeze-thaw resistance tests and RAC for C30/37 lost 29% more weight than NAC in this test.