Performance of self-consolidating concrete made with various admixture combinations: Fid-Bau Portal

Performance of self-consolidating concrete made with various admixture combinations

Hwang, S.D. / Mayen-Rena, D. / Bonneau, O. / Khayat, K.H.

Recently, self-consolidating concrete (SCC) has been used in repair applications, including bridge abutments, bridge girders, and parapet walls. Well-prepared SCC mixtures can flow readily among closely spaced obstacles without blockage and can encapsulate the reinforcement and develop proper strength and durability. The acceptance of such concrete has been driven by its cost-effectiveness in repair that often presents difficulties of access to placement and consolidation. Other advantages of such concrete include its ability to secure high quality finish and reduce cracking potential compared to standard repair materials typically used in partial-depth repair. Given the increase in admixture combinations used to control the rheology of SCC, an experimental investigation was carried out to evaluate the effect of high-range water reducer (HRWR) and viscosity-modifying admixture (VMA) combinations on key workability properties affecting flow characteristics and stability of SCC. The investigated mixtures were prepared with two basic mixture proportions with water-to-binder ratios (W/Bs) 0.35 and 0.42. The latter set of mixtures was proportioned with VMA to enhance stability, while the mixtures with the 0.35 w/cm were proportioned without any VMA. Four polycarboxylate HRWRs of various molecular weights and one polynaphthalene sulfonate HRWR were used. Four types of air-entraining agents and VMAs were also used to secure adequate air-void stability and proper resistance to segregation. The findings indicate that SCC mixtures made with W/B of 0.42 is the highest limit of W/B to secure an adequate stability of fresh concrete for repair applications. For a given slump flow (660 +/- 20 mm) and air volume (6.5 +/- 1.5 %), the increase in HRWR dosage can indeed decrease the V-funnel flow time and increase the filling capacity. On the other hand, the higher fluidity of the concrete resulting from the greater HRWR content can reduce the yield stress and the resistance to surface settlement, or static stability.