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Due to climate change, some areas in the world witnessed higher levels of heavy rain than the capacity of the wastewater system of the streets. Therefore, water tankers are used for the dewatering process to take the extra rainwater from the streets to keep a smooth flow of vehicles and to use the water in agriculture and industry. Water is taken to a water treatment plant. Performing the dewatering process as fast as possible, especially in crowded streets, was ignored by researchers. In this study, at first, the problem was solved using two mixed integer programming (MIP) models. A new variant of identical parallel machine scheduling with job splitting is proposed for the first time, where one or at most two tankers can work at the same flood location at the same time. This is performed in the second model. However, the first model considers dividing the dewatering processes into two phases, where the first one, which is more urgent, is to reduce the amount of floodwater. The second one is for dewatering the rest of the water. Then two genetic algorithms (GAs) were used to solve faster the two MIP models, which are NP-hard problems. At first, the MIP and GA models were applied to small-sized problems. Then GA was used for large practical data sets. Results showed that for small problems, MIP and GA gave optimal solutions in a reasonable number of iterations, while for larger problems, good solutions were obtained in a reasonable number of iterations.

The development of alternative binders as a replacement for Portland cement can be one of the means to meet both the growing demand and sustainability of cement in the construction industry. Alkali-activated materials (AAMs) are increasingly attracting attention as a promising sustainable alternative to Portland cement-based materials. However, the manufacturing process of alkaline activators is energy-intensive that leads to an increase in the overall embodied energy and greenhouse gas emissions of AAM systems. Waste-derived activators have been promoted as an effective way not only to reduce the greenhouse gas emissions but also to reprocess wastes into valuable activators that can substitute the conventional alkali-silicate activators. To advance the understanding of the performance of AAMs and the synthesis of waste-derived activators, the present research focuses on three aspects: (a) fundamental differences in rheological properties between AAM and cement systems, (b) systematic synthesis and characterisation of rice husk ash (RHA) derived sodium silicates (SSs), and (c) the effect of RHA derived SSs on the rheology, structural build-up and durability of AAMs compared to commercially available SS. An alternative SS solution was synthesised by mixing RHA with NaOH solution. The influence of different parameters, including the processing duration (1 to 5 h of stirring) and temperature (60 to 100 °C), on the dissolution efficiency of silica from RHA was examined. The results showed that the extraction of silica from RHA was effective using the hydrothermal process (heating and stirring). The proper selection of the raw RHA and the extraction conditions allow for maximising the yield of silica, where most of the amorphous silica in RHA was dissolved within 1 h at 80 °C. The silicate species in the activator is a determinant component that affects the overall performance of AAMs. First, a test program was designed to understand the distinctive rheological and temporal viscoelastic behaviour of AAMs compared to cement pastes. After that, the effect of RHA-derived SSs on the structural build-up of AAM pastes was investigated. The results revealed that the high viscous activator increased the plastic viscosity of AAM pastes by 4 – 8 times higher than that of cement paste and drastically decreased the yield stress due to viscous effects and weak inter-particle interactions. Temporal changes in viscoelasticity showed that the negligible colloidal interactions between particles in AAM paste made the system non-percolated until the initial setting. This behaviour was very different from the well-percolated network that forms in cement paste a few minutes after mixing. In AAMs activated with RHA SSs, filtered and unfiltered solutions were used from the optimised process (1 h at 80 °C) to study the evolution of the viscoelasticity, ultrasonic pulse waves, infrared spectra, and flowability. The overall structural build-up of AAM paste activated using RHA SS was very comparable to the one activated using commercially available SS. This suggests the formation of identical reaction products and the minor effect of the nature of the silicate species in the activator. In terms of flowability, the residues in the unfiltered RHA SS increased the yield stress and reduced the flowability of the paste. Finally, the ability of AAMs made of RHA SSs to resist aggressive media was evaluated using various tests, including water absorption, sorptivity, acid attack, sulphate attack, rapid chloride-ions penetration, chloride migration and chloride diffusion. The durability performance was comparable between the AAMs activated by the filtered RHA and commercial SSs. On the other hand, the unfiltered RHA SS showed some adverse effects on some durability properties. For instance, the residues in the unfiltered RHA SS resulted in a slight increase in the expansion caused by sulphate attacks. However, these residues had insignificant impacts on the compressive strength when using identical SiO2/Na2O and Na2O/binder ratios in the mix design. It is believed that the results of this research will provide an advanced understanding of the early-age evolution of the AAM paste from the fresh condition to the initial setting. In addition, better insights were described on the effect of various processing parameters on the availability and structure of silicate species during the preparation of RHA SSs. Moreover, this research proved that the use of unfiltered RHA SS containing undissolved particles is still practically viable, but special attention should be paid to flowability and some durability properties.