Omar Chaalal

The present research investigates the potential of using marble powder waste (MP), a byproduct of limestone, to build self-compacting mortar (SCM), with the goal of creating economic and environmental value by replacing cement with co-products and improving their handling and management. The aim is to improve the sustainability signature of cement-based materials in the construction industry. Five different mortar mix proportions, replacement of cement by MP at dosages of 0%, 10%, 20%, 30%, and 40%, are tested for slump flow, yield stress, viscosity, water absorption, bulk density, porosity, and compressive and flexural strength. The investigation delves into the influence of MP content on the rheological and mechanical properties. The results showed that the increase in marble powder led to an increase in both yield stress and plastic viscosity. Furthermore, the investigation found that a self-compacting mortar with a yield stress of 4.1 Pa at a 40% MP replacement rate and a viscosity of 2.9 Pa.s may achieve a slump flow of 242–351 mm. Furthermore, mortars containing 30% MP had a maximum compressive strength of 39.8 MPa at 28 days, which is a 7.4% increase over the reference mortar. Microstructure study showed that adding 30% MP improves mortar cohesiveness and densification. These findings demonstrate the potential of MP as a beneficial addition in SCM production, providing better performance and structural integrity. However, limitations in terms of specific application scenarios and long-term durability necessitate more exploration. Practical consequences include the potential for creative, sustainable, and cost-effective self-compacting concrete compositions, which will help to progress construction practices and environmental sustainability. Social consequences include the possibility for reduced environmental impact and increased resource efficiency in the construction industry. The results of the study provide an interesting insight into the possibility of using this kind of waste as a replacement for cement, thus reducing the demand for cement and the burden on landfills for disposing of such invasive waste from MP, and reducing the carbon footprint.

Materials recycling presents a compelling economic case for waste disposal sites and the conservation of natural resources. This study delves into the substitution of cement with varying percentages of marble waste (0%, 10%, 20%, 30%, 40% and 50%). The water-to-binder ratio is consistently set at 0.44 for all mixes. Chemical admixtures such as superplasticizers or viscosity agents are frequently added to the mortar to improve its flow and strength. We conducted mini-slump flow and rheometer tests to assess the fresh mixes' rheological properties, as well as tests to measure the compressive and tensile strength of the mixes. The findings indicate that including marble powder enhances the mechanical properties of self-compacting mortar. A substantial 29% enhancement was achieved for a mixture incorporating 30% marble waste. The most favorable rheological properties, including slump flow, yield stress, and superior mechanical performance in compressive and tensile strength, were observed in the mix containing 30% marble powder waste. Furthermore, the investigation showed that the self-compacting mortar with a yield stress of 0.98 MPa at a 50% MW replacement rate and a viscosity of 1.4 Pa.S can achieve a slump flow of 25–31 cm. These findings illustrate marble waste potential as a valuable addition to self-compacting mortar (SCM) manufacturing, delivering improved performance and structural integrity. However, specific application scenarios and long-term endurance restrictions require further investigation. Practical effects include the possibility of developing inventive, sustainable, and economic SCM compositions, which will help to advance construction practices and sustainability. The social ramifications include reducing environmental impact and increasing resource efficiency in the construction industry.

Wastewater can be segregated as greywater and blackwater separately. The greywater generated in malls, restaurants, and university buildings is generally dilute, while it will later become concentrated when it is merged into the main sewage collection line. It would be more economical and environmentally friendly if the greywater is treated locally using a modular wastewater treatment facility that produces treated water amenable for other uses such as irrigation or horticulture. The objective of this article is to study the economic feasibility and design a decentralized plant that produces fresh water from greywater generated at the Abu Dhabi university campus located in the United Arab Emirates. The proposed unit will consist of a compact design of filtration, chemical treatment and disinfection processes that would generate treated wastewater that can be used for horticulture in and around the local campus or can be stored and supplied for irrigation purposes. Several parameters such as total suspended solids, biological oxygen demand, and chemical oxygen demand are measured and monitored throughout the entire process and are regulated by appropriate operations performed for each unit. This study shows that decentralization of greywater treatment is not only economical but also essential for the management of fresh water, which in turn assures environmental sustainability. By using coagulation, flocculation and chlorination with a 30 mg/L alum dosage, 0.6 mg/L of polyacrylamide and 0.12 mg/L of sodium hypochlorite, respectively, greywater is treated to meet the water specification for reusing it for horticulture. Further, a modular plant with an investment of USD 8 M is proved to process 90,000 tons of greywater with a 34% discounted rate of return.

Methacrylate-based polyhedral oligomeric silsesquioxane (POSS) is one of the new composites used as a dental resin. Both monofunctional methacryl isobutyl POSS (MIPOSS) and multifunctional methacryl POSS (MAPOSS) are reported to be possible resins that possess the desired properties for using them as dental resins. Our group’s previous comparative study on these two resins showed that the MAPOSS composite has superior mechanical properties compared with the MIPOSS composite. In this article, molecular dynamic simulations (MD simulations) are performed to study the water sorption in these two composites. Water sorption in dental composites can have several effects on the material properties, performance, and longevity of dental restorations. Water sorption in MAPOSS and MIPOSS composites is analyzed by studying the hydrogen bonding, cluster analysis, density projection calculations, and diffusion coefficient calculation of water molecules within the resin matrix. MD simulations results are further used to understand the interaction of water molecules with the resin matrix comprehensively, which governs the composite’s mechanical properties. The water sorption study showed that the MAPOSS composite has less water sorption capacity than the MIPOSS composite. The practical significance of this study is to find properties that affect dental restoration and longevity, which can help in the design of better materials for dental applications.

This article focuses on designing and analyzing a new method for mixing in process vessels. We propose using an air bubble curtain to accomplish the desired mixing. The air bubble curtain used in this study is made of an empty pipe with several holes through which air is pumped, which in turn produces a swarm of bubbles that causes pseudo-turbulent mixing in the tank filled with a liquid solution. A uniform distribution of bubbles within the tank was assured by maintaining a see-saw movement of the air bubble curtain. Mixing inside the tank was quantified by measuring the salt concentration in a laboratory model tank (30 cm × 30 cm × 30 cm) and a pilot-scale tank (200 cm × 100 cm × 100 cm). The optimal flow rates of air and the mixing time in both tanks that can achieve complete mixing were obtained from the experimental results. The proposed air bubble curtain can be of potential use in wastewater treatment, biotechnology, and aquaculture where turbulent mixing is required with minimum energy dissipation per unit mass.

Phosphogypsum releases have a detrimental effect on flora and fauna and also cause economic loss due to the loss of sulfur. This study contributes to solving this problem using a process that consists of the valorization of this byproduct. A new sustainable method that consists of using sulfuric acid is proposed to process the Algerian phosphogypsum to recover the sulfur, which is imported in huge quantities until today. The experiments carried out in this investigation have enabled us to recover sulfur in the form of SO₂ using appropriate additives such as silica, alumina, clay, and charcoal as reducing agents. These additives accelerate the desulfurization process and decrease the decomposition temperature of calcium sulfate. As a result, these additives allow the reduction of energy used and simultaneously increase the concentration of SO₂. X-ray diffraction shows that thermochemical decomposition is not complete and that the sulfur present in the residue exists in the form of CaSO₄ and CaS at 1150 °C. After calcination of phosphogypsum, the analysis of the residues obtained shows that they have a chemical composition almost identical in terms of quality to that of clinker, which can further be used in the cement production.

Fulfilling worldwide energy demand in the 21st century is the most challenging problem. New kinds of energy sources along with the new technological breakthroughs to maintain enough oil and gas supply are needed to meet the tremendous rise in world’s energy demand. Recent dramatic fall in oil prices has accentuated the problem. Now, the challenge is to fill out the increasing gap between energy demand and supply with more cost effective techniques. Recently, Abu Dhabi University has filed a patent application (US-Patent Application No 15/342,664) reporting the invention of Dr. Omar Chaalal that fulfills practically all criteria discussed above. In this paper, a ‘green’ alternative to chemical flooding is proposed. The new technology proposed uses two types of plant extracts that increases the total oil recovery to 96% of initial oil in place (IOIP) during the tertiary recovery mode. While water flood recovered around 50% of the IOIP, 0.5% wt of the natural plant extract recovered 77% in the secondary recovery mode. The additives were extracted from two plants available in the United Arab Emirates (Product A and Product B). These natural extracts proved to be very effective in formations containing water with a salinity range of 70,000 to 180,000ppm with temperature going up to 100 °C.