Journal of Environmental Treatment Techniques 2021, Volume 9, Issue 1, Pages: 268-274 268 Design and Analysis a Low-Cost Cementitious Waterproofing Mixture Based on the Solution of a Mathematical Model 3 Mohamed Bassam Hamami , * 2 , Feras Al Adday 1 Fatima Alsaleh 1, 3 Department of Transportation Engineering, Faculty of Civil Engineering, University of Aleppo. 2 Middle East University, Amman, Jordan 3 Mathematics Department, Faculty of Science, University of Aleppo Received: 16/09/2020 Accepted: 13/11/2020 Published: 20/03/2021 Abstract Most of the investigation results of engineering studies depend on the principle of trial and error in decision-making, which requires a lot of time and effort and does not guarantee to reach the optimum solution. Whereas, mathematical models provide mathematically proven optimum solutions to problems. This research aims to exploit the huge quantities of fine recycled aggregates (FRA) from the destroyed buildings and infrastructure of the city of Aleppo to design a cement-based waterproofing concrete mixes, by developing a mathematical model. The optimum proportions of the materials included in the composition of cement-based waterproofing concrete mixes have been founded by this model which is derived and solved by a simulated annealing method. Experimental results showed the efficiency and accuracy of the proposed model in determining the optimal quantities of the mixture content with a minimum cost according to the required engineering conditions. Keywords: Fine Recycled Aggregates, Cement-Based Waterproofing Mixture, Linear and Nonlinear Constrains, Simulated Annealing Method 1 Introduction 1 Concrete buildings are usually exposed to different environmental and climatic conditions that may negatively affect their efficiency. Moisture resulting from the exposure of buildings to water is one of the most important problems that affect not only structural damage but also affect the health of the residents of these buildings [1]. The moisture leaking into the building causes damage to the internal and external cladding elements, it also has another destructive role on reinforced concrete elements upon constant exposure to moisture, as it leads to the migration of salts from the concrete, affecting the properties of the concrete. Not limited to this only, but may extend to the reinforcement steel and lead to rust and weaken its sections [2]. Therefore, waterproofing is the first step to solving this problem to preserve the structural elements and increase the service life of the facility. Waterproofing can be defined as the process by which surfaces of building elements and joints are treated to prevent water from leaking into or through them in the event of hydrostatic pressure [3]. While waterproof materials are generally known as materials that are often in the form of one or more layers or membranes that are implemented on surfaces or ceilings to prevent water from seeping into the structural elements with or without hydrostatic pressure, as for moisture insulation materials they are materials in the form of layers or strips placed within walls to reduce water leakage without hydrostatic pressure, and to be executed directly Corresponding author: Feras Al Adday, Faculty of Engineering, Middle East University, Amman, Jordan, falkhalil@meu.edu.jo above the natural ground level or above the ceiling level [4]. The waterproofing is divided according to the method of its implementation into two main types, namely positive insulation, in which the source of moisture is isolated so that it prevents its access to the structural element, thus preserving its properties. As for negative insulation, which is done if the leaked water has entered the element to reduce moisture damage to the cladding and inner medium of the structural element, this type is not resorted to except in very special cases [5]. The waterproofing materials are divided into two main parts: the films are either bituminous or polyvinyl chloride (PVC) films or polyethylene (PE) films of different types of HDPE, LDPE, LLDPE, and VLDPE. These materials vary greatly according to their chemical composition, these are divided into waterproofing materials with a water-based, polymeric-based, bituminous-based, cement-basis, and other. These materials are called liquid waterproofing coatings. Or in the form of a mixture of two components, one in the form of a cement-base and the other in the form of a polymeric-basis [6, 7]. Cement-based waterproofing mixes are the most common type due to their ease of use and relatively cheapness as well as its homogeneity with the concrete elements covered by [8, 9]. Liquid waterproofing coatings it can be formed from only one compound, which is a solid (powder) mixed with water to produce a coating, or two compounds, one of them is solid and the other is a liquid, which produces the waterproofing J. Environ. Treat. Tech. ISSN: 2309-1185 Journal web link: http://www.jett.dormaj.com https://doi.org/10.47277/JETT/9(1)274