**2. Special concrete mix development**

The complexity of construction projects, and the need to buildings structures with increased heights, bridges with longer spans, and infrastructure projects with minimized maintenance necessitates the development of concrete mixes with superior characteristics, higher durability, and minimal need for maintenance. Thus, concrete mixes with increased rheology and high flowing ability, high early and final strength are required. In addition, increased concrete durability is desired to minimize the need for regular maintenance and reduce the project life cycle cost. Special types of concrete mixes are displayed in the following section.

#### **2.1 Ultra-high-performance concrete**

Ultra-high-performance concrete (UHPC), known in the European market as reactive powder concrete, is a new class of concrete developed in the 1990s. UHPC concrete are currently used in high-rise building construction in the United States, and in specific transportation, and defense applications. UHPC mixes are characterized by self-consolidation concrete (SCC) workability, fast setting, high early strength, and final compression capacity that reaches 250 MPa [1, 2]. UHPC is characterized by improved long-term performance, low voids, higher alkali-silica resistivity due to the incorporation of SCMs, and post-cracking stiffness due to the placement of random steel fibers within the mix [3, 4]. The aforementioned characteristics represent a combination of the advantages of high-performance, self-consolidation, and fiber reinforcement inclusion, as shown in **Figure 1**.

#### **2.2 High-strength concrete**

The term high-performance concrete (HPC) is used to describe concrete produced with selected high-quality mix constituents, optimized mix design, and low *Application of Supplementary Cementitious Materials in Precast Concrete Industry DOI: http://dx.doi.org/10.5772/intechopen.100249*

**Figure 1.** *Composition of UHPFRC [2].*

water-to-powder (W/CM) ratio. According to the American Concrete Institute (ACI), HPC is defined as "concrete meeting special combination of characteristics and uniformity requirements," which cannot be achieved using conventional constituents, and regular mixing and curing procedures [5]. The mix composition of HPC depends mainly on the replacement of a significant amount of Portland cement and incorporating SCMs up to 40% by weight.
