This paper presents an efficient application for red mud, i.e., recycling red mud as a mineral additive in the development of ultra-high performance concrete (UHPC). Specifically, the modified Andreasen & Andersen particle packing model has been carried out to obtain a densely compacted UHPC matrix. After that, red mud is used to replace cement to reduce both the landfilling of red mud and the environmental burden of UHPC. Then, the fresh and hardened behavior of UHPC with and without red mud has been evaluated. It has been found that the addition of red mud enhanced early-age (7 d) durability due to the accelerated hydration process, while reduced the workability and the mechanical properties of UHPC. The degraded workability may affect the application in the building with complex shapes, but it can still be applied in general construction. An ultra-high strength (>150 MPa) of UHPC including 40% red mud can be generated after high-temperature curing, although the addition of red mud reduces the compressive strength. Besides, it is noteworthy that significantly shortened setting time can be obtained when replacing cement by red mud, providing ideas for the application in the UHPC rapid-repairing process. The pore structure analysis reveals a coarsening of micro-pore structure with an increase of red mud content. Finally, a low-energy consumption, as well as low radiation risk further promotes the environmental protection application of red mud based UHPC.

Sustainable use of red mud in ultra-high performance concrete (UHPC): Design and performance evaluation

Effect of elevated temperatures on mechanical properties of lightweight geopolymer concrete

The corrosion inhibition investigation of aerial extract of Cnicus Benedictus , a weed referring to the Asteraceae family has been evaluated on the mild steel corrosion in 0.5 M HCl with the employment of the weight-loss method, potentiodynamic polarization measurements (PDP) and electrochemical impedance spectroscopy (EIS) techniques. This investigation demonstrated Cnicus Benedictus extract (CBE) as a green and sustainable mild steel corrosion inhibitor in 0.5 M HCl media exhibiting an inhibition efficacy of 92.45% at 1000 ppm. With the increased concentration of CBE, the value of i corr and corrosion rate (C R ) decreased significantly from 7.4114 to 0.97438, revealing the protective effect of CBE on mild steel. The deposition of a highly defensive coating on the mild steel surface was demonstrated by the contact angle measurements. Additionally, the increase in the K ads values indicated a stronger interaction between the inhibitor molecules and metal surface. Furthermore, density functional theory (DFT) and Monte Carlo simulations have been utilized to validate the significant inhibition characteristic attained by the experimental study and to suggest an adsorption mechanism. 

Computational and Experimental studies on the corrosion inhibition performance of an aerial extract of Cnicus Benedictus weed on the acidic corrosion of mild steel

Pathways towards sustainable concrete

Cracking is one of the major deteriorating causes of concrete, which allows the entrance of chemicals and can lead to the loss of physico-mechanical and durability properties of concrete structures. To protect, repair, and rehabilitate concrete structures, the application of different surface coating agents and sealants, binding agents, as well as adhesives has been commonly practiced. Although such techniques have mostly been applicable, due to their inherent mechanism difference, major challenges such as delamination and lack of cost effectiveness have resulted in searching for alternative methods of crack sealing or self-healing. One of the novel self-healing mechanisms is using bacterial induced calcite precipitation in concrete mixtures to heal concrete cracks. In this technique, bacterial mineralization (biomineralization) is performed through decomposing urea and calcium to produce calcium carbonate (CaCO 3 ), which can fill cracks. To review the mechanisms ruling this precipitation, this article aims to present an in-depth analysis of biomineralization, CaCO 3 precipitation, physico-mechanical, durability and microstructural properties of bacterial concrete. To do this, over 70 research articles have been reviewed and their data including the types and dosage of bacteria, mixture proportions, as well as the result of mechanical and durability tests are gathered, provided and analyzed. Based on this review, it is found that the biomineralization is mostly dependent on factors such as the applying method and consistent preservation of the living bacteria. In addition, the environmental impact of bacterial concrete is found to be directly linked with the urea content in the concrete mixture. • A review of bacteria-based calcium carbonate precipitation for self-healing of concrete is presented. • In bacterial concrete , alkaliphiles bacteria is mostly used due to their high resistance to alkalinity. • Bacterial concrete has an enhanced mechano-durability properties due to high compaction and reduced defects. • The environmental impact of bio-concrete is directly linked with the amount of urea used. 

A systematic review of bacteria-based self-healing concrete: Biomineralization, mechanical, and durability properties

The current work investigates the sustainable use of red mud (RM) as a supplementary cementitious material in concrete. The large amount of RM produced by the alumina industry creates disposal problems, as RM pollutes the surrounding environment and leads to ecological imbalance. To develop suitable uses for RM, concrete in which some of the cement was replaced with RM was experimentally investigated. The RM content, strength, and curing age of the concrete were considered as the parameters in this work, and the mechanical properties and durability of the RM-based concrete were tested to investigate its performance. The results indicated that the RM-based concrete had superior properties. Concrete in which 10% of the cement was replaced with RM exhibited high strength and durability compared to a 100% cement-based concrete control. To examine the micro-level behavior of the RM concrete, the microstructure was studied using X-ray diffraction and scanning electron microscopy.

Red mud as an additive in concrete: comprehensive characterization

Performance studies on rate of self healing in bio concrete

Received: 23 January 2019 Accepted: 6 April 2019 Red mud is a highly alkaline solid waste produced from the alumina refinery plants. Every year more than 300 million tons of red mud is producing throughout world. Disposal of a large quantity of red mud is very expensive and it creates contamination of neighbor lands, air and water bodies. Using red mud as a sustainable cementitious material in concrete is highly appreciable, because concrete is a second largest using material after water. Moreover, reduce the negative effect on environment due to red mud disposal as well as cement industries. The present paper conducted a critical review on bayer process of red mud, physical and chemical properties of red mud. And also workability, mechanical, durability and microstructure characterization of red mud when used in concrete as sustainable cementitious material. In the red mud iron oxide and alumina oxide are presented abundantly. Red mud accelerates the heat of hydration in concrete and it leads to strength enhancement in early ages. Increases the quantity of red mud in concrete reduces the workability but increases the strength of concrete. However, the chemical composition of red mud and its particle size helps to improve the durability property of concrete. Red mud offers more capable to arrest the chloride ions and other ions diffusion into concrete. Red mud minimizes the micro cracks and voids present in concrete by its particles size as well as bonding nature with other materials up to certain dosage of red mud used in concrete.

/pdf/a-state-of-the-art-on-red-mud-as-a-substitutional-31itvho08q.pdf

Chava Venkatesh

Papers

Red mud as an additive in concrete: comprehensive characterization

Performance studies on rate of self healing in bio concrete

A State of the Art on Red Mud as a Substitutional Cementitious Material

Comparison of mechanical and durability properties of treated and untreated red mud concrete

Comprehensive microbiological studies on screening bacteria for self-healing concrete