Fluidity evaluation of fiber reinforced-self compacting concrete based on buoyancy law

An experimental testing program was undertaken to evaluate the applicability of using the principles of Archimedes' law for buoyancy to assess the fluidity of self compacting concrete (SCC) as well as fiber reinforced self compacting concrete mixes (FR-SCC). A cone instrument with different apex angle values (20, 30, 40 and 45°) was implemented. One type of steel fibers (SF), three types of polypropylene fibers (PP1, PP2 and PP3) as well as one type of glass fibers (GF) with different fiber volume fractions and aspect ratios were conducted. Fourteen FR-SCC mixes in addition to a control mix were examined. A new terminology called fluidity index (FI) was proposed and evaluated based on the displaced volume rate according to the buoyancy law through performing cone penetration test. Parallel with the penetration test, traditional flow ability and segregation resistance tests were performed.

The results indicated that the proposed method is effective in evaluating the fluidity of FR-SCC mixes in terms of FI. FI values between 0.8 and 1.0 indicate SCC mixes whereas, FI lower than 0.8 indicate fresh concrete with fluidity not satisfying requirements of SCC. The proposed method can be performed either at laboratory or at field with and without sampling. Moreover, it can be directly adapted to the cast concrete in structural members provided that there is no obstruction for penetration. The direct proportion between FI and the slump flow test results indicated its viability to evaluate the fluidity of both FR-SCC and SCC mixtures.