**4.1 SCMs in UHPC concrete**

Silica fume and quartz flour are used in proprietary UHPC mixes to increase mix strength and durability. Current proprietary mixes, commercially available in the US and EU markets, have a high content of SCMs. In addition to their strength and durability advantages, SCMs partially reduce the cement consumption and hence reduce the carbon footprint [15–17]. Mix design and SCM content in major proprietary mixes are shown in **Table 4**.

The compressive strength of proprietary UHPC mixes ranges from 160 to 200 MPa. The strength is significantly increased due to the incorporation of SCMs and steel fibers. Steel fibers result in improved tensile capacity and higher values for the modulus of elasticity (MOE) and modulus of rupture (MOR). Detailed mechanical properties of proprietary UHPC mixes are shown in **Table 5**.

The high strength of girders produced using UHPC and HPC concrete mixes enables design engineers to fabricate shallow girders with a very high span-to-depth ratio. A comparison of sections with similar capacity produced by different materials including proprietary UHPC mixes is shown in **Figure 7** [29].


#### **Table 4.**

*Proprietary UHPC mix designs in global construction markets [18–20].*

