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.

Processing of Waste from Enrichment with the Production of Cement Clinker and the Extraction of Zinc

This paper presents studies on the processing of enrichment tailings as a component of a raw mixture in order to obtain cement clinker, with simultaneous distillation of zinc. Thermodynamic studies were carried out in the temperature range of 600–1600 °C using the software application “HSC Chemistry 6” developed by the metallurgical company Outokumpu (Finland). As a result of the conducted studies, we found that zinc contributes to the intensification of mineral formation of cement clinker. In particular, it was found that the formation of belite is possible in the temperature range from 990.7 to 1500 °C with Gibbs energy values of −0.01 and −323.8 kJ (which is better than the standard process by −11.4 kJ), respectively; the formation of alite is possible in the temperature range from 982.9 to 1500 °C with Gibbs energy values of −0.05 and −402.1 kJ (better than the standard process by −11.4 kJ), respectively; the formation of tricalcium aluminate is thermodynamically possible in the temperature range from 600 °C at ΔGTo = −893.8 kJ to 1500 °C at ΔGTo = −1899.3 kJ (better than the standard process by −1570.1 kJ), respectively; and the formation of four calcium aluminoferrite is possible in the temperature range from 600 °C at ΔGTo = −898.9 kJ to 1500 °C at ΔGTo = −1959.3 kJ (better than the standard process by −1570.2 kJ), respectively, with simultaneous distillation of zinc into a gaseous state for its further capture.

PERICLASE-SPINEL REFRACTORY MODIFIED ТІО2

Over the past decades, the development and improvement of refractory materials for lining high-temperature zones of rotary kilns continues. The main requirements for refractory products for lining rotary kilns for cement clinker roasting are: high density and ultimate compressive strength, low porosity and gas permeability, increased abrasion resistance, low thermal conductivity, high corrosion resistance and the ability to form a protective layer.Today, the main goal of modern researchers is to create a heat-resistant refractory with a flexible structure that ensures its integrity at high temperatures and mechanical loads, which have the ability to form a protective coating layer. In this work, a technological approach has been tested for introducing a vibro-milled modifier (briquette based on a high-alumina component and a titanium-containing additive) into the composition of the raw charge for periclase-spinel refractory in the form of a pre-synthesized product containing crystalline phases of the Al2O3 – TiO2 – FeO system. The basis for the production of periclase-spinel refractories modified with TiO2 is the four-component system MgO – Al2O3 – FeO – TiO2, on the basis of thermodynamic calculations of which the content of individual components of the charge was selected and the operational characteristics were predicted. The interrelation of physical and mechanical properties with the content of individual components in the initial charge warehouses is shown, and the directions of solid-phase processes with their participation are noted. The features of the microstructure of the sample material are noted in relation to the formation of an optimal set of properties. It is shown that the nature of the organization of micropores is favorable for increasing the thermal stability of the material, which complements the phase adaptation mechanism also with the structural effect of damping mechanical stresses during thermal cycling.

The Effect of Gel-Type Contributions in Lime-Sand Bricks, Alkali-Activated Slags and CEMI/CEMIII Pastes: Implications for Next Generation Concretes

Lime-sand bricks of different ages were investigated using IR-spectroscopy, thermogravimetry, and X-ray diffraction/scattering. After subtraction of the dominant quartz contribution (80%), the IR spectra show the absorption peaks of the hydrothermally formed binder phases. The spectra also show the alteration of the binder during ageing under atmospheric conditions by the influence of CO2 forming carbonate and a condensed SiO2-gel (secondary gel). The alteration could also be proven in X-ray pattern, obtaining a separation between crystalline CSH and amorphous contributions in the freshly produced lime-sand brick, too. Here, the formation of CSHamorph could be understood as a precursor state (primary gel) to the crystallization of CSH phases. X-ray patterns of aged bodies of alkali-silicate solution activated slags (AAS), CEM-I/CEM-III pastes, and CEM-I concrete indicate that in all cases a similar amorphous CSH-type phase (CSHamorph) was formed, which is responsible for the hardening properties as the glue. The main X-ray peak of CSHamorph obtained using CuKα-radiation with a usual diffractometer is observed between 24° and 35° 2 Theta with maximum at about 29° 2 Theta, whereas it appears much more broadly distributed between 15° and 35° 2 Theta with maximum between 26° and 28° 2 Theta for a geopolymer body prepared using the reaction of alkali-silicate solution and metakaolin (AAMK). This is due to the network formed by siloxo and sialate units in the case of AAMK, given that any crystallization can be ruled out. The origin of increasing mechanical strength during the ageing of AAS mortars must be due to further crosslinking of the preformed siloxo chains. Thermal treatment up to 800 °C leads to a complete loss of any mechanical strength of the CEM pastes due to the destruction of crystalline CSH-phases, whereas geopolymer bodies maintain their strength. Implications for next generation concrete include that cement clinker could be completely replaced by using a using alkali silcate solution technology for gel formation.

Application of calorimetry and other thermal methods in the studies of granulated blast furnace slag from the old storage yards as supplementary cementitious material

The calorimetric and DTA/TG measurements were applied in testing the effect of granulated blast furnace slag originated from the storage yards of different age, added as a supplementary cementing material to the Portland cement clinker. The studies were performed with aim to evaluate the kinetics of cement hydration and the modification of hydrated paste composition in the presence of additive. The material after 20-year storage, the crushed slag after approximately 2-years storage and the new slag from the current production in the metallurgical plant were used. The slag percentage was 5 ÷ 50%. The addition of granulated blast furnace slag stored for a long time affects the standard properties of cement reducing the compressive strength at longer maturing and with the percentage of additive. This is related mainly to the reduction in the vitreous component. However, at the additive content up to 50% the binder complying with the requirements of the relevant European standards for common cements could be produced. Basing on the results of TG measurements the role of calcium carbonate, being the product resulting from the slag weathering process, acting as a grindability and setting/hardening modifying agent, was highlighted.

Quantitative Analysis of Portland Cement Clinker with Rietveld Refinement: Implications of the Amorphous Matter

Six ordinary Portland cement (OPC) clinkers and one white cement clinker were analyzed with the Rietveld method, using ZnO internal standard (IC), to determine the presence of amorphous matter (AM). All clinkers contain abundant AM and have lower silicate phase contents when compared with the same clinkers analyzed without IC, whereas the abundances of the aluminate and ferrate phases were not affected by AM. The white cement clinker had the highest AM content. Determination of AM is important for complete characterization of the OPC clinker and might contribute to a better understanding of the mechanical properties of the clinker.

Alkali-Active Sand Slate Powder for Use as Mineral Admixture in Mass Hydraulic Concrete: Technical and Economic Analysis

This work has launched a comprehensive investigation on the macro performance and micro structure of mass concrete produced with alkali-active sand slate powder (ASSP) for use as the mineral admixture and a thorough analysis on its technical and economic effects is also conducted. Results indicated ternary blend with hybrid of 5–8 wt.% silica fume (SF) and 15–20 wt.% ASSP has the optimal compressive and flexural strength. ASSP particle participates in hydration, accelerates hydration of cement clinker within 8.5 hours, and reduces the autogenous strain of pastes by 164 × 10−6 in case of dosage less than 25% by mass. Improvement in the mechanical and deformation properties of concrete produced with the hybrid of SF and ASSP is attributed to better particles gradation, compactness enhancement, and transformation in products of hydration. On the whole, it provides another new approach for use of alkali-active rock after second processing as mineral admixture in hydraulic concrete in terms of good performance and economic effects.