Effect of Substitution of Natural Calcareous and Clay Materials with Cement in Low-Carbon Concretes

Population growth, extensive use of non-renewable resources, increased production of wastes and greenhouse gases has caused serious damages to the environment. This population growth has also increased the construction rate, such that the construction industry is one of the major sources of environmental pollution in the world. To respond to the growing demand for cement production and achieve the objectives of sustainable development and environment, materials with cement-like properties that can completely or partially substitute cement should be introduced and examined. This study investigated some pozzolanic materials with cement-like properties. Since the production and use of these materials do less adversely affect the environment, they are regarded as natural materials. The pozzolanic materials under consideration in this study were bentonite, kaolin, and lime. This study investigated the combination of these materials with different types of clay to achieve acceptable results applicable in the construction industry. The results from compressive strength tests showed that the use of bentonite and kaolin in the concrete mixture reduced the required amount of sand as compared to the similar reference specimen. This mixture has a compressive strength of approximately 17 MPa versus 17.13 MPa for the reference specimen (S7). Based on the results, employing washed sand in specimens with a lower amount of cement did not result in an appropriate strength due to the lack of adequate adhesive materials in the mixture. Simultaneous use of lime and bentonite And kaolin fails to produce the minimum desirable structural strength. The use of CaO with an optimal amount of water and cement can produce better results.