Compressive behaviours, splitting properties, and workability of lightweight cement concrete: The role of fibres

Conventional concretes require high binder dosages and high density to develop satisfactory mechanical properties. By substituting natural aggregates with fly ash cenospheres (FACs), high-strength concretes with significantly reduced density can be obtained. This paper reports an extensive investigation into the effects of incorporating fibres into lightweight cement concretes (LCCs) prepared with FACs, and demonstrates how different fibres impact the fresh and hardened properties of LCCs. The mechanisms underlying the resulting changes in mechanical properties and density were studied by X-ray diffraction, mercury intrusion porosimetry, and scanning electron microscopy. The results showed that the incorporation of fibres effectively reduced the brittleness of LCC without altering its composition. Compared with smooth steel (SS) and polypropylene (PP) fibre, end-hooked steel (ES) fibre exhibited a better improvements to the mechanical properties of LCC. The addition of 1 vol% ES fibre increased the splitting strength by approximately 138% and compressive strength by approximately 20%, with density increased by less than 5%. Determining an optimum fibre type and content to achieve a balance between fresh properties, mechanical properties, and microstructure is therefore critical for improving the performance of LCC. Although all of the LCCs had similar mineralogical compositions, LCCs reinforced with PP fibres had higher porosity, lower bonding strength, and looser microstructures than those reinforced with steel fibres owing to the fundamental properties of PP, which explains the poorer mechanical properties of the PP fibre-reinforced LCCs. This study provides an optimized approach for designing and producing LCC.