Development of Locally Produced Natural Pozzolans in Oman:Potential and Perspectives for an eco-efficient composite cementsindustry in Oman

Cement-based materials including concrete are recognized as the most used building materials and the second-largest consumed material on earth. The massive urban and industrial development witnessed during the last decades has led to a large consumption of concrete and its components. This process necessitates an extensive extraction of raw materials and consumption of energy which accompanies by the release of a large amount of greenhouse gases (GHG) to the atmosphere, particularly carbon dioxide (CO2). Ordinary Portland cement (OPC), the main component of all cement-based building materials and the most pollutant, is known to contribute by around 8% to 10% of the anthropogenic emissions of CO2. Reducing the consumption, and hence the production of OPC reduces the concrete`s carbon footprint and its environmental impacts. Meanwhile, plain Portland cement concrete structure lacks durability and suffers severe degradations when exposed to aggressive environment such as chloride, sulphate, or acidic media. The harmful environmental impacts and weak durability of plain cement concrete structures have led to the development and use of pozzolanic materials, as a partial substitute for Portland cement. Therefore, there is an urgent need for the production of low carbon supplementary cementitious and pozzolanic materials (SCPMs) from locally available sources and yet efficient in their properties and yield structural concrete/mortar of high quality. Supplementary cementitious and pozzolanic materials are known not only to provide an added value to concrete/mortar or paste in terms of mechanical and durability performances but also to enhance their sustainability by reducing the environmental impacts of the construction industry. Along with the artificial by-products pozzolans, the utilization of natural cementitious and pozzolanic materials in construction has become a common practice in today`s cement-based materials. For centuries, Sarooj has been used in Oman in various engineering structures and traditional buildings; however, its today`s use is limited to plastering and some restoration of historical buildings. Although the Sultanate of Oman is very rich in various natural mineral resources, the engineered production of natural and artificial pozzolans is lacking and even non-existing except for this traditionally produced pozzolana called Sarooj. Therefore, the aim of this research proposal is first to develop local natural pozzolans produced from soils or natural deposits procured from different sites within the Sultanate and then assess their key engineering and durability properties. The procured raw materials will be evaluated, before and after calcination, applying a series of physical, chemical, and microstructural characterization tests to assess their suitability for use as a pozzolan in cement-based materials. To develop an energy-efficient natural pozzolans, the temperature and duration of calcination will be optimized using the collected data from thermogravimetry and differential thermal analyses on raw materials. The developed pozzolans will be used in the production of concrete, mortar, and paste mixtures as a partial replacement of normal Portland cement. The blended mortar/concrete will be assessed at both fresh and hardened states where the main physical, mechanical, microstructural, and durability properties, as well as insulation performances will be determined. Furthermore, a multi-criteria decision making (MCDM) technique will be used to generate a model that considers all the influencing parameters (type of pozzolans and percentage used, its chemical and mineralogical compositions, and calcination conditions) to enable all performances measures to be evaluated simultaneously for a given blended cement concrete/mortar mix. Some preliminary unpublished results recently obtained indicate a high potential of a reactive material that could be developed and used as a cementitious and/or pozzolanic material in the cement mortar and concrete industry. Overall, by partially replacing Portland cement with locally produced natural cementitious/pozzolanic materials, mortar/concrete`s durability and sustainability of concrete structures and the construction industry can further be enhanced.