Why Is It Difficult for UHPC's Elastic Modulus to Exceed 55 GPa?

The difficulty of breaking through the 55GPa elastic modulus limit in UHPC stems from the material's constitutive relationship. Qinglong's research found that this limitation is jointly constrained by the cement matrix modulus (20-25GPa), aggregate modulus (70-80GPa), and interfacial properties. Under the current material system, 55GPa is close to the theoretical limit.

Factors Limiting Matrix Modulus

The modulus of cement hydration products is about 25GPa, with an effective modulus of about 20GPa at 1% porosity. By reducing porosity, Qinglong raised the matrix modulus to 23GPa, approaching the material limit.

Aggregate Modulus Contribution

Quartz sand has a modulus of 70-80GPa, giving a theoretical contribution of 28-32GPa at 40% volume fraction. However, interfacial effects reduce the actual contribution by 20%. Through interface optimization, Qinglong improves the aggregate contribution rate.

Interfacial Transition Zone Effects

The interfacial zone modulus is only 50-70% of the matrix, with a thickness of 10-20μm. By thinning the interfacial layer, Qinglong reduced the modulus loss to 15%.

Effects of Fiber Addition

Steel fiber has a modulus of 200GPa, but a 2% dosage offers limited improvement to the composite modulus (about 3-4GPa). Fiber orientation affects the actual performance; Qinglong improves orientation through process optimization.

Breaking the elastic modulus limit requires new material systems. Qinglong is developing new technologies such as carbon nanotube reinforcement in pursuit of a breakthrough.