Effects of mineral admixtures on the properties of self-compacting concrete

In this study, the effect of using different kinds of fine materials at varying percentage compositions on the properties of self-compacting concrete was investigated. Mixtures containing various combinations of fly ash, ground granulated blast furnace slag and metakaolin and a mixture incorporating only portland cement as the binder material were produced at a constant water-to-binder ratio. For each mixture, to attain a self-compacting concrete, the amount of superplasticizer to be used was determined during the slump flow test. The concretes were also tested for workability and mechanical properties. A total of 11 concrete mixtures were designed having a constant water/binder ratio of 0.32 and total binder content of 550 kg/m3. The control mixture included only a portland cement as the binder while the remaining mixtures incorporated binary and ternary cementitious blends of portland cement. After mixing, the fresh properties of the concretes were tested for slump flow time, L-box height ratio, V-funnel flow time and unit weight. Moreover, on the separated mortar phase of the mixtures, initial and final setting times and viscosity were measured. From each mixture, three cubes were also taken to test the ultrasonic pulse velocity and compressive strength respectively. The performances of mineral admixtures used varied for different tests. When the workability is of concern, the fly ash had the most favorable effect. On the other hand, regarding the strength of concretes metakaolin had the best performance compared to the other mineral admixtures used.