Mechanical Properties of Recycled Aggregate Concretes Containing Silica Fume and Steel Fibres

Abstract

In this study, the impact of steel fibres and Silica Fume (SF) on the mechanical properties of recycled aggregate concretes made of two different types of Recycled Coarse Aggregates (RCA) sourced from both low- and high-strength concretes were evaluated through conducting 60 compressive strength tests. The RCAs were used as replacement levels of 50% and 100% of Natural Coarse Aggregates (NCA). Hook-end steel fibres and SF were also used in the mixtures at the optimised replacement levels of 1% and 8%, respectively. The results showed that the addition of both types of RCA adversely affected the compressive strength of concrete. However, the incorporation of SF led to compressive strength development in both types of concretes. The most significant improvement in terms of comparable concrete strength and peak strain with ordinary concrete at 28 days was observed in the case of using a combination of steel fibres and SF in both recycled aggregate concretes, especially with RCA sourced from high strength concrete. Although using SF slightly increased the elastic modulus of both recycled aggregate concretes, a substantial improvement in strength was observed due to the reinforcement with steel fibre and the coexistence of steel fibre and SF. Moreover, existing models to predict the elastic modulus of both non-fibrous and fibrous concretes are found to underestimate the elastic modulus values. The incorporation of SF changed the compressive stress-strain curves for both types of RCA. The addition of steel fibre and SF remarkably improved the post-peak ductility of recycled aggregates concretes of both types, with the most significant improvement observed in the case of RCA sourced from a low-strength parent concrete. The existing model to estimate the compressive stress-strain curve for steel fibre-reinforced concrete with natural aggregates was found to reasonably predict the compressive stress-strain behaviour for steel fibres-reinforced concrete with recycled aggregate.

Effects of the Concrete Strength and FRP Reinforcement Type on the Non-Linear Behavior of Concrete Deep Beams

“…As per Figures 7b, 8b and 9b, under the main diagonal cracking load, the concrete components' maximum tensile stress, including different heights, appeared to be between the interior support plate and the loading plates, in the range of 5.06-5.44 MPa. The tensile strength of concrete could be considered as about 10% of compressive strength [62,63], which was equal to 5.4 MPa, near to the same range obtained in this study, as mentioned earlier. Therefore, it can be inferred that the diagonal crack was propagated between the interior support plate and one of the loading plates, where the maximum tensile stress raised in the concrete components, similar to that observed in the plots of the tensile damage variable (DAMAGET) (Figure 6a,e,h).…”

Properties of Lime-Cement Concrete Containing Various Amounts of Waste Tire Powder under Different Ground Moisture Conditions

“…In some previous research studies, it was reported that the water quality can also affect the mechanical properties of concrete and cementitious materials [ 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ]. Therefore, in the current investigation, distilled water was used for the characterization tests.…”

Evaluation of the Performance of a Composite Profile at Elevated Temperatures Using Finite Element and Hybrid Artificial Intelligence Techniques

“…Nevertheless, the composite beams demonstrated brittle behaviour when channels were embedded in unconfined plain concrete. In contrast, when the channels were embedded in high-strength concrete (HSC) [6], the behaviour of the composite beam was ductile [7][8][9][10]. In addition, extended channel shear connectors represent better flexibility compared to lower channels.…”