Improvement of Calcium Aluminate Cement Containing Blast Furnace Slag at 50°C and 315°C

During the thermal recovery of heavy oil thermal recovery wells, improving the mechanical properties and integrity of the cement ring is of great significance for the safe and efficient exploitation of heavy oil resources. This paper studies the relative properties of calcium aluminate cement and three kinds of slags under the conditions of 50°C × 1.01 MPa and 315°C × 20.7 MPa. CAC-slag composite material performance was evaluated using the cement paste compressive strength and permeability tests to study the physical properties of CAC with blast furnace slag. X-ray diffraction analysis, scanning electron microscopy (SEM), and thermal analysis (DSC/TG) were carried out to investigate the mineralogical composition of CAC with blast furnace slag. Results show that adding blast furnace slag did not affect the performance of cement slurry. Moreover, C2ASH8 curing occurred at low temperature, the microstructure of CAC paste was compact, and the permeability resistance was improved, thus improving the low-temperature properties of neat CAC. When cured at a high temperature, the CAC paste was mainly hydrated with C3ASH4 and AlO(OH), which had a well-developed crystal structure. Adding blast furnace slag can improve the CAC resistance to high temperature.

Effect of basalt and polypropylene fibers on crumb rubber mortar with Portland cement and calcium aluminate cement binders: Strength and artificial neural network prediction model

This paper aims to study the influence of basalt fiber (BF) and polypropylene fiber (PPF) in crumb rubber (CR) mortar made of two different types of cement, including ordinary Portland cement (OPC) and calcium aluminate cement (CAC). CR was used to partially (5%, 10%, 15%, and 20% by volume) replace the fine aggregate in OPC and CAC mortars. BF and PPF were added (0.1%, 0.3%, and 0.5% by total volume) in the CR mortars. The consistency, density, compressive, and flexural strength of cement mortars were investigated. The use of CAC cement slightly increased the consistency; however, the results showed that the CR replacement and the addition of both fiber types tend to reduce the consistency in OPC and CAC mortars. Significant reduction in the density of fiber-added CR mortar was found with increasing CR content, whereas the influence of both PPF and BF was minimal. The fiber-added CR mortar made of both binder and fiber types in general exhibited a reducing trend in the 28 days compressive strength when increasing CR and fiber contents. Nevertheless, an enhancement in the compressive strength of CAC mortar with 20% CR was found with the addition of 0.1% of both fibers. The use of CR and addition of the fibers generally decreased the flexural strength of mortar made of both binder types; however, the addition of 0.3% BF in mortars containing 15–20% CR positively affected the flexural performance. Finally, the artificial neural network (ANN) approach demonstrated the ability to predict the compressive strength of fiber-added CR mortars. The model showed a considerably insignificant mean square error (MSE) of 1.4–1.5 and high plot regression (R) results of 0.97–0.98.

Evaluation of Calcium Aluminate Slags and Pig Irons Produced from the Smelting-Reduction of Diasporic Bauxite

This work evaluates the characteristics of calcium aluminate slag and pig iron samples obtained from the smelting of calcined and reduced diasporic bauxite ore. The study is conducted in the Pedersen process framework, which is a method to produce alumina from low-grade resources. Parameters such as the effect of crucible type, lime addition, and atmospheric conditions are studied considering the characteristics of the product pig irons and calcium aluminate slags for further uses. The behavior of the bauxite and distribution of the species between slag and metal was assessed based on the applied analytical techniques and thermodynamic calculations. Iron was reduced and separated from the slags in the presence of carbon (graphite crucible) for both the reduced and calcined bauxite. Si and Ti were mainly concentrated in the slags. Iron was separated from the slag in the absence of carbon (alumina crucible) for the H2-reduced bauxite. The results show that slags with increased lime additions are composed mainly of 5CaO.Al2O3 and CaO.Al2O3, that are considered highly leachable compounds. An optimum CaO/Al2O3 mass ratio of 1.12 was suggested. The presence of O2 and/or OH- in the furnace atmosphere will result in the formation of 12CaO.7Al2O3.

Development of a Calcium Aluminate Cement from steelmaking slag by altering its mineralogical compositions

Strict environmental norms and raising concern to recycle solid wastes generated during ironmaking and steelmaking processes has been the key driving force in developing various technologies. The present study describes a calcium-aluminate clinker prepared from steel ladle slag by modifying its mineral compositions. The slag paste prepared by mixing with water exhibited flash setting behaviour due to the presence of C12A7 and C3A phases. In contrast, the slag clinker, developed by sintering a mixture of pre-determined quantity of slag and Al2O3 at 1400°C for 2h and 4h, contained CA, CA2, Gehlenite and ‘Q’ phases. Hydration of slag clinker contained stable C3AH6, AH3 and stratlingite with preferential growth of calcium-aluminate hydrate prisms along c-axis that provided a well-defined raceme like morphology with interlinked structure. It improved the setting time and crushing strength of the clinkers after 6h and 24h curing at room temperature. Additionally, presence of ‘Q’ phase with lamellar prismatic crystals also helped in enhancing the strength. The developed clinker also exhibited superior crushing strength as compared to commercially available calcium aluminate cement of medium purity. The slag, used as a source of CaO could replace CaCO3 completely and thus contributed to reduction in CO2 emission during clinker making process.