Preparation of a Novel Cement from Red Mud and Limestone

Red mud (RM) is an industrial waste obtained from the Bayer process which is usually discharged into marine or disposed into a landfill causing pollution for the surrounding water, air, and soils. Thus, disposal of RM is an environmental concern, and it should be recycled effectively. Because RM consists of iron- and aluminum-rich phases, it is possible to be processed into cementitious material and utilized for construction purposes. This research fabricated a type of cement from the mixture of RM and limestone. The mixture was sintered at temperature of 1180 °C to obtain the clinker of the novel hydraulic cement with C2S, C3A, and C4AF minerals. In which, C2S, C3A, and C4AF are respectively belite, alite, and tetra-calcium aluminoferrite compounds that are characteristic hydraulic minerals of Portland cement clinker. The specifications of this cement were tested and evaluated in this study such as chemical and mineralogical compositions, fineness, specific surface area, mechanical strength after 3, 7, and 28 days.

The Influencing Factors for Volume Stability of Ladle Slag

The purpose of this study was to investigate the mechanism causing the unsoundness of ladle slag. Calcination temperature may have an impact on the level of reactivity of f-CaO. When CaO was produced at a higher temperature, the reactivity of CaO was lower. For example, dead burnt CaO (DCaO) was produced at higher temperatures than light burnt CaO (LCaO); therefore, DCaO had less reactivity than LCaO. In a hydration test, DCaO (1500 °C) showed 62 times lower reactivity than LCaO (900 °C), which meant that DCaO would result in the delay of hydration of CaO easily. Additionally, DCaO would cause unsoundness more easily than LCaO when adding the same number of cementitious materials. For this reason, using ASTM C114-18 (Standard Test Methods for Chemical Analysis of Hydraulic Cement) to quantify DCaO content may underestimate DCaO content by up to 20%. Conversely, this method was more suitable for f-CaO since it had high reactivity. Moreover, this study demonstrated that ladle slag would cause unsoundness when added into the cementitious material because it was produced from a higher temperature process (over 1500 °C), which generates the DCaO. Therefore, when reusing ladle slag, the problem of low reactivity of DCaO should be considered.

Clinical Efficacy of Polycaprolactone β-Calcium Triphosphate Composite for Osteoconduction in Rabbit Bone Defect Model

The combination of β-tricalcium phosphate (β-TCP) with polycaprolactone (PCL) has been considered a promising strategy for designing scaffolds for bone grafting. This study incorporated PCL with commercially available β-TCP (OsteoceraTM) to fabricate an injectable bone substitute and evaluate the effect of PCL on compressive strength and setting time of the hydraulic cement. The mechanical testing was compliant with the ASTM D695 and ASTM C191-13 standards. Results showed that PCL-TCP composite presented a well-defined architecture with uniform pore distribution and a significant increase in compressive strength compared with β-TCP alone. Eighteen rabbits, each with two surgically created bone defects, were treated using the PCL-TCP composites. The composite materials were resorbed and replaced by newly formed bone tissue. Both PCL-TCP and β-TCP demonstrated equivalent clinical effects on osteoconduction property in terms of the percentage of newly formed bone area measured by histomorphometric analysis. PCL-TCP was proven to be as effective as the commercially available β-TCP scaffold (OsteoceraTM).

Characterization of Coconut Shell Ash and Eggshell Powder as Supplementary Cementitious Materials in Roller Compacted Concrete Industrial Access Pavements and Parking Facilities

The cost of cement used in concrete works is on the increase and unaffordable, yet the need for hydraulic cement concrete and other cement concrete based infrastructures keeps growing with increasing population, thus the need to find alternative binding materials that can be used solely or in partial replacement of cement. The use of waste materials with pozzolanic properties in concrete production is a becoming a worldwide practice. The assessment of the pozzolanic activity of cement replacement materials is becoming increasingly important because of the need for more sustainable cementing products. In this study, a mixture of coconut shell ash and eggshell powder is used as partial replacement of hydraulic cement in ranges of 0%, 5%, 10%, 15%, and 20%. The concrete specimens were prepared at 1: 3: 2.5 mix ratio of cementitious material, fine aggregate and coarse aggregate. The mix ratio satisfied the minimum cement content of 148.32kg/m3 (250Ib/yd3) and the minimum cementitious material content of 267 kg/m3 (450Ib/yd3) for roller compacted concrete pavement. The compressive strength, splitting tensile strength and flexural strength tests were carried out to assess the strength characteristics of ternary concrete mixture containing coconut shell ash and eggshell powder and the feasibility of using coconut shell ash and eggshell powder as partial replacement of cement in industrial plant access concrete roads and parking lots. The results indicate that a mixture of coconut shell ash and eggshell powder can be used up to 20% by weight for replacement of cement in roller compacted industrial plant access concrete roads and parking lots.

Research on Fire Resistance Potency of Ferro-Geopolymer Concrete

Fire is also one of the most significant possible threats to most buildings and structures. As structural materials deteriorate due to exposure to high temperatures, the building can collapse. As a result, the use of fire safety materials to mitigate thermal damage to structural members is important. Ferrocement is a cementitious composite substance made of hydraulic cement mortar and tightly spaced layers of continuous and relatively small sized wire mesh. Mortar is an excellent insulator, and reinforcing wire mesh can minimise surface spalling more effectively than plain concrete. Similarly, geopolymer mortar has good fire resistance due to its ceramic-like properties. The performance of ferrocement factor in this study is made of geopolymer and its fire resistance is investigated.