# An Insight into the Chemistry of Cement--A Review
## 6 Future Perspective in the Use of Recycled (Waste) Materials in Cementitious Matrices  
The use of recycled (waste) materials in the construction sector can achieve significant benefits in terms of both environmental preservation (i.e., saving natural resources, reducing the amount of greenhouse gas emissions and energy consumption) and processing costs. Quite recently, several studies report the use of waste materials as a substitute counterpart for the aggregate fraction in the preparations of concrete and mortar, trying to either maintain or (better) improve the final mechanical properties. The use of materials deriving from the demolition of structures (i.e., construction and demolition waste, CDW) is one of the major studied waste substrates that attract the interests of scientific literature. For example, [PERSON] et al. [91] proposed to examine and compare CDW generation in all EU member states in correlation with their respective national construction businesses, gross domestic product, and capital, together with an assessment of the policy framework and CDW recovery performance of each member state against the recovery target of the waste framework directive. The results show that Austria, Germany, the Netherlands, Belgium, and France are the highest CDW producers, whereas Croatia, Slovenia, Slovakia, Poland, Portugal, and Spain were the lowest ones. [PERSON] et al. [92], instead, evaluated the role played by raw materials for wood-plastic composites (WPC)to achieve the CDW recovery target in Finland. Specifically, the objective of this analysis was to assess the environmental impacts of WPC production using specific CDW fractions (i.e., wood, plastic, gypsum board, and mineral wool) as raw materials, and to compare these impacts with the traditional situation in which these CDW fractions are treated by conventional methods. The results indicate that, compared with the traditional situation, the environmental impacts of CDW management can be reduced when CDW fractions are used in WPC production. Moreover, [PERSON] et al. [93] evaluated the economic implications of traditional demolition and selective demolition, analyzing a case study in Portugal. Several scenarios are considered, based on possible waste management options, some of which favor selective demolition over a conventional one. By considering the Italian situation, [PERSON] et al. [94] applied life-cycle assessment (LCA) methodology to assess the environmental performance of construction and demolition materials in the current context of the management of the Lombardy region, identifying critical aspects related to the management system of non-hazardous CDW and possible actions for improvement (e.g., increment and refinement of the quality of the recycled aggregate). Moving away from Europe, [PERSON] et al. [95] analyzed a case study in Brazil where CDW was used to produce new building materials, replacing the natural aggregate fraction to produce novel (sustainable) bricks showing superior average compression strength than standard bricks. This finding shows that it is possible to produce low-cost bricks with excellent physical properties using CDW as an aggregate and lime/cement as an additive. [PERSON] et al. [96] conducted a study regarding the use of recycled CDW aggregate to create asphalt mixtures for urban roads. Numerous tests were conducted to evaluate the susceptibility of the asphalt concrete samples to moisture damage and plastic deformation (typical for this specific application). The results indicate that it is possible to use CDW aggregates (up to 20%) to pave urban roads. In a recent study by [PERSON] et al. [97], the technological, economic, and environmental aspects related to operational CDW recycling facilities that produce medium- to high-quality recycled concrete aggregates have been reported (for details please refers to [97]). Interestingly, [PERSON] et al. [98] evaluate the impact of two alternatives for CDW management, namely: either recycling or disposal.