Using natural pozzolana as an improvement of Portland cement to manufacture concrete with environmental properties (Green Concrete)

Introduction. The construction industry is considered as one of the major causes of environmental degradation due to the use of traditional building materials such as cement. As a result, there is an urgent need to develop sustainable alternatives to produce eco-friendly concrete using natural unprocessed materials. While acknowledging the importance of cement in the urbanization of mankind, it should be noted that its widespread use undoubtedly contributes to global warming which threatens the environment worldwide due to carbon dioxide emissions when fossil fuels are used to melt the products used in its manufacture, which are a mixture of clay, water and lime to produce the main binding material i.e. clinker. Materials and methods. The aim of the study is to investigate the possibility of replacing Portland cement with natural pozzolana according to replacement ratios ranging from 10 to 50 %, and to study the effect of this replacement on physical properties, the most important of which are thermal conductivity and mechanical properties represented by the resistance to simple pressure, taking into account the following factors: the use of recycled gravel as an alternative to natural gravel. Results. The results showed that increasing the percentage of cement replacement with pozzolana increases the thermal resistance of concrete, since replacing cement with an equal mass of pozzolana results in a 5 % reduction in thermal conductivity. In addition, recycled aggregates have higher thermal resistance compared to natural aggregates even when 50 % of cement is replaced by ground pozzolan. An increase in resistance of more than 24 % is observed, and a decrease in the simple pressure resistance of the resulting concrete is acceptable if the replacement with pozzolana is less than 50 %. Conclusions. The simple compressive strength values of cubic specimens exceed the minimum limits of international specifications for cement blocks, which allows the manufacture of cement blocks using secondary aggregates with the possibility of replacing cement with ground pozzolana according to different replacement ratios up to 50 %.