Preparation of Heavyweight Ultra-high Performance Concrete Using Barite Sand and Titanium-rich Heavy Slag Sand

Abstract

The heavyweight ultra-high performance concrete (HUHPC) was prepared with barite sand partially replaced by titanium-rich heavy slag sand (THS) at replacement proportion of 0%, 30%, 50%, 70% and 100% in this work. The results show that THS incorporation can effectively improve the mechanical properties and reduce the volume shrinkage of HUHPC. The HUHPC with 50% THS replacement reaches an apparent density of 2 890 kg/m³ (for fresh HUHPC), 28 d compressive strength of 129 MPa, 28 d flexural strength of 23 MPa, 28 d flexural toughness of 28.4, 56 d volume shrinkage of 359×10⁻⁴ and, as expected, excellent durability. Microstructural investigation demonstrates that the internal curing of pre-wetted THS promotes the hydration of the surrounding cement paste thereby strengthening the interfacial transition zone, resulting in the “hard shell” formation around aggregate to “protect” the aggregate. Additionally, the “pin structure” significantly improves the cement paste-aggregate interfacial connection. The combination of “hard shell protection” and “pin structure” remarkably improve the mechanical properties of HUHPC produced with porous THS aggregate.

Keywords

heavyweight ultra-high performance concrete / titanium-rich heavy slag sand / mechanical properties / durability / internal curing