# Novel Processing Methods of Low-Clinker Multi-Component Cementitious Materials--A Review
## 1 Introduction  
Current developments in construction material technologies are associated with a widespread trend to reduce harmful environmental impacts during the production of materials and their use in buildings and structures. The life cycle analysis of materials in construction elements also covers the issues of the durability of materials--by extending the durability and the service life of structures, the desired effect of reducing the consumption of primary mineral resources can be achieved. Due to the massive use of Portland cement (PC) concrete in construction, the issue of the emissivity of PC cement production has become of great importance. With a simple reduction in the Portland clinker content in cement, whose carbon footprint is estimated at 0.98 kg CO\({}_{2}\)/kg clinker (the sum of process, fuel and electricity-related emissions), Gawlicki [1] allows for a substantial reduction in its carbon footprint. Therefore, technologies for the use of cement binders with a highly reduced clinker factor are being developed, using a variety of mineral components or industrial by-products as non-clinker cement constituents [2; 3; 4; 5]. In accordance with the European standard EN 197-5 [6], the family of general-purpose cement has recently been expanded to include CEM II/C-M and CEM VI multi-component cement, allowing for an increased proportion of non-clinker main constituents, 36-50% and 51-65%, respectively. In many countries, the range of applicability of new types of cement has not been established yet, and their use is marginal [7; 8]. [PERSON] et al. [9] and [PERSON] et al. [10] separately suggested more extreme proposals to limit the content of Portland clinker in cement to 20-35% or even 5%. The main challenges preventing the greater use of multi-component cement with a low proportion of Portland clinker are related to detrimental changes in the rheologicalcharacteristics of concrete mix, a considerable decline in the early rate of cement hardening, and occasionally insufficient strength of mature concrete. The vulnerability of concrete to variations in ambient temperature and humidity, plastic shrinkage, the phenomenon of bleeding, and increased pressure of the concrete mix on the formwork are all increased by a delayed setting and very slow early hardening of the cement [1; 2; 3; 4; 5; 11; 12]. Moreover, a too-slow increase in concrete strength during the first day following casting restricts, if not outright prevents, the use of the slip-form construction technique; slows the removal and replacement of formwork at the construction site; extends the curing time; and delays other construction tasks that are carried out on already at least partially hardened concrete. Chemical admixtures are a very effective approach to adjusting the workability of the mix and expediting concrete's hardening when used with conventional cement. However, new multi-component cement formulations require the development of specific admixtures for efficient control of the rheological properties of innovative concrete mixtures and their rate of early hardening [1; 2; 3; 4; 5; 11; 12]. Non-clinker constituents of multi-component cement basically consist of supplementary cementitious materials (SCMs) [13; 14] that need to be selected and processed properly for their optimal efficiency. The SCMs' fineness, level of clinker replacement, water-to-ceentitious-materials ratio, and cement and SCM chemistry (the pozzolanic or hydraulic activity) are only a few of the variables that affect how reactive SCMs are in the cementitious system [13; 14; 15]. By modifying the rheological characteristics for a specific application, SCMs, such as granulated blast furnace slag (GGBFS) [16; 17; 18; 19], Silica Fume (SF) [16; 17; 19; 20], fly ash (FA) [16; 17; 21; 22], bottom ash [21; 23], copper slag [24], volcanic ash (VA) [18], and pulverized fuel ash (PFA) [18], can also increase rheological properties in addition to the mechanical properties and durability of concrete.