Aluminate Hydrate Research Articles

Performance of the one-part geopolymer stabilized soft clay under acids attack

The evolution of globalization and rapid industrialization, coupled with intensive human activities, leads to a significant release of acidic gases and particles (e.g., NOX and SO2) is unavoidable. These emissions eventually result in dry and wet acid depositions due to atmospheric circulation. This infiltration of acidic elements alters the chemical properties of water systems, thereby deteriorating ground stability. The economically developed soft clay areas face considerable threats from these acid environmental attacks. This study focused on employing a ''one-part'' geopolymer (OPG) comprising ground granulated blast furnace slag (GGBFS), fly ash (FA), and solid sodium hydroxide (NH) to stabilize the soft clay. Simultaneously, the deterioration behavior of OPG stabilized soft clay under two different acids (HNO3 and H2SO4) with various pH values (pH of 2, 4, and 6) and varied immersion periods up to 240 days was evaluated including the mass loss, neutralization depth (ND), pH value, and unconfined compressive strength (UCS). Additionally, scanning electron microscopy (SEM) and X-ray energy spectrometry (EDS) characterized the evolution of microstructure and hydrate composition of OPG-stabilized soft clay post varied acid immersion. The results highlighted the superior acid resistance of the stabilized soft clay with an 80:20 GGBFS/FA ratio compared to other ratios. The presence of significant hydration products, such as calcium silicate hydrates (C–S–H), calcium aluminate (aluminosilicate) hydrates (C-A-(S)–H), and sodium aluminosilicate hydrates (N-A-S-H), was observed in the OPG stabilized soft clay. In addition, the contents of Si in the OPG played a significant role in enhancing the acid resistance of the OPG stabilized soft clay. Based on these experimental results, two proposed mechanisms detailed the deterioration and acid resistance of the OPG stabilized soft clay under HNO3 and H2SO4 attack. The findings of this study contribute to advancing scientific comprehension concerning the acid resistance of the OPG stabilized soft clay in ground improvement practices.

Molecular insight into the initial hydration of tricalcium aluminate

Portland cement (PC) is ubiquitously used in construction for centuries, yet the elucidation of its early-age hydration remains a challenge. Understanding the initial hydration progress of tricalcium aluminate (C3A) at molecular scale is thus crucial for tackling this challenge as it exhibits a proclivity for early-stage hydration and plays a pivotal role in structural build-up of cement colloids. Herein, we implement a series of ab-initio calculations to probe the intricate molecular interactions of C3A during its initial hydration process. The C3A surface exhibits remarkable chemical activity in promoting water dissociation, which in turn facilitates the gradual desorption of Ca ions through a metal-proton exchange reaction. The dissolution pathways and free energies of these Ca ions follow the ligand-exchange mechanism with multiple sequential reactions to form the ultimate products where Ca ions adopt fivefold or sixfold coordination. Finally, these Ca complexes reprecipitate on the remaining Al-rich layer through the interface-coupled dissolution-reprecipitation mechanism, demonstrating dynamically stable inner-sphere adsorption states. The above results are helpful in unmasking the early-age hydration of PC and advancing the rational design of cement-based materials through the bottom-up approach.

The Effect of Waste Marble Dust and Corncob Ash on the Engineering and Micro-Structural Properties of Expansive Soil for Use in Road Subgrades

This research investigated the effect of Waste Marble Dust (WMD) and Corncob Ash (CCA) on expansive soil's engineering and microstructural properties. Various laboratory experiments were performed on the natural soil to ascertain its characteristics. The corncobs underwent pre-water treatment for fourteen days to remove excess potassium and increase their silica content, resulting in a rise in the silica level from 0% to 50%. At first, only WMD was added to the soil in increments of 5% to 30% using compaction and California bearing tests. The optimum dosage of 15% WMD addition yielded the best result. CCA was then incorporated by the weight of the soil from 2% to 10% in increments of 2% to the first optimum (15% WMD) to obtain the overall optimum for the study (15% WMD and 8% CCA). Stabilization of the natural soil using both materials led to the modification and solidification of the soil mass, evident by the rise in California bearing ratio values from 1.68% to 15.53% and unconfined compressive strength from 41.33 kN/m2 to 174.68 kN/m2. There was also a decrease in the soil's free swell from 120% to 15% as well as reductions in the liquid limits from 56.23% to 36.01% and in the plasticity index from 29.74% to 8.72%, respectively. The microstructural images showed the formation of cementitious compounds in the form of calcium silicate hydrate and calcium aluminate hydrate gels. The findings indicate that using WMD and CCA as a unit has great potential in enhancing engineering properties, like strength parameters and the swell potential of expansive soils.

Analisis pembuatan dan penggunaan koagulan poly aluminium chloride (PAC) pada proses penjernihan air

Background: Poly Aluminum Chloride (PAC) is a complex inorganic compound between hydroxyl (OH) ions and aluminum ions which undergo gradual chlorination. PAC is able to coagulate suspended substances or colloidal dispersions to produce floc that easily settles. Methods: The raw materials used in the manufacture of PAC consist of alumina hydrate Al (OH) 3, hydrochloric acid (HCl), sulfuric acid (H2SO4), and calcium carbonate (CaCO3). The experiments were carried out by reacting Al (OH) 3 as much as 100 grams, HCl as much as 180 ml, and H2SO4 as much as 127.1 grams at 90 ° C and 100 ° C temperature variations with time variations of 30s, 60s, and 90s. The characterization was tested in the form of a jar test and FTIR test. Finding: In the Jar Test, the optimum temperature and time are obtained at 90 ° C and 60s and at 100 ° C and 60s. At the optimum jar test results, the FTIR test was performed. Conclusion: From the test results, this study meets PAC manufacturing standards.

The Effect of Gypsum/Bassanite on the Retardation of Ethylene Diamine Tetra(Methylene Phosphonic Acid) Sodium in Oil Well Cement Slurry

Summary Organophosphonates are commonly used retarders to prolong the thickening time of oilwell cement slurry at medium and high temperatures. In this paper, the impact of calcium sulfate in cement on the retarding effect of ethylene diamine tetra(methylene phosphonic acid) sodium (EDTMPS) was explored. First, the thickening properties of cements from four different factories were studied in detail with varying additions of EDTMPS. The study revealed diverse thickening phenomena, including retarding, accelerating, and increasing the initial consistency of cement slurries. The heat flow of cement hydration was detected, and the mineral changes of cement slurries at the early stage (1–3 hours) were analyzed. Additionally, the effect of EDTMPS on the hydration of tricalcium aluminate (C3A) and gypsum (GP)/bassanite (BS) slurry was investigated through X-ray diffraction (XRD) and ion concentration test. Finally, two clinkers from the same cement factory were mixed with GP/BS of different dosages to study the effect of calcium sulfate type on the thickening properties of cement slurry with EDTMPS. The results revealed that EDTMPS slowed down the dissolution of GP while promoting the dissolution of C3A. The rapid hydration of C3A increased the consistency of cement slurry without the retarding effect of GP. However, EDTMPS promoted the dissolution of BS, which can retard the hydration of C3A. Therefore, EDTMPS is appropriate for cements containing BS.

Macro–micro investigation on stabilization sludge as subgrade filler by the ternary blending of steel slag and fly ash and calcium carbide residue

This study investigates the efficacious utilization of sludge as a subgrade filler through in-situ shallow stabilization, employing cementitious industrial waste materials including steel slag (SS), fly ash (FA), and calcium carbide residue (CCR) as binding agents. The primary emphasis lies in the evaluation of the macro unconfined compression strength of stabilized sludge over a seven-day curing period, facilitated by a quadratic polynomial response surface model to determine the optimal composite stabilizer (WZ01) proportions. Furthermore, an array of meticulous microstructural analyses encompassing X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and energy-dispersive spectroscopy were undertaken to elucidate the development of internal cementitious products and the intrinsic mechanisms underpinning sludge stabilization in tandem with WZ01. The findings ascertain that the optimum WZ01 composition stands at SS: FA: CCR = 32:28:40. Prominent mineralogical constituents within the stabilized sludge encompass amorphous calcium silicate hydrate, calcium aluminate hydrate, and crystalline ettringite. The amelioration in stabilized sludge properties stems from intricate processes involving ion exchange, hydration reactions, and pozzolanic activities. Significantly, the WZ01 curing agent demonstrates heightened cost-effectiveness and environmental merits compared to conventional Portland cement.

Hydration characteristics of steel slag in the presence of diethanol-isopropanolamine

Steel slag (SS) as a supplementary cementitious material has low cementitious activity. Diethanol-isopropanolamine (DEIPA) is an organic admixture that can enhance the cementitious activity of cementitious materials. This work aimed to investigate the hydration characteristics of SS under the complexing of DEIPA. The hydration process of SS, the complexation of DEIPA with metal ions, and the dissolution process of C3A and C3S in the presence of DEIPA were systematically investigated. The results showed that DEIPA enhanced the hydration of aluminate (C3A and C12A7), ferrate (C2F) and silicate phases (C3S and C2S), which formed a large amount of monocarboaluminate, paraalumohydrocalcite and C–S–H gels. In the early stages of hydration, the hydration products were mainly C–S–H gels, monocarboaluminate and paraalumohydrocalcite, and in the later stages of hydration, the hydration products were mainly C–S–H gels, paraalumohydrocalcite. The monocarboaluminate may be transformed to paraalumohydrocalcite at a later stage. This hydration-promoting effect was related to the complexation of DEIPA. DEIPA facilitated the dissolution of mineral phases and the precipitation of complexed metal ions by complexing with metal ions. The stronger complexation of Al3+ by DEIPA made it more solubilizing for C3A. As a result, more aluminum-containing hydration products were formed. The weaker complexation of Ca2+ by DEIPA made it a weaker solubilizing for C3S, which also led to a weaker promotion of silicate hydration by DEIPA. The solubilization of DEIPA to minerals enhanced the cementitious activity of SS, which ultimately led to the increase in the compressive strength of the hardened SS paste at each age.

Ceramic-added lime and cement mortars: A review of applications in building products.

Ceramic-added air lime mortars have been used since ancient times owing to the pozzolanic effect provided by crushed ceramic particles that impart hydraulic properties. This work reviews the historical use, composition, reaction mechanisms, characterization techniques, and performance properties of ceramic-added air lime mortars. The fine ceramic powder composed of silica and alumina phases reacts with calcium hydroxide released during lime hydration to form calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH) via pozzolanic reaction. This provides hydraulicity and reduces setting time compared to pure air lime mortars. The coarser ceramic particles also serve as aggregate and refine the microstructure as filler. The reactivity depends on the ceramic composition, amorphous phase content, particle size distribution, and firing temperature. Optimal proportioning of the fine ceramic powder and coarse ceramic aggregate is necessary to achieve desired properties. Ceramic addition enhances the durability of air lime mortars against weathering while maintaining compatibility with lime-based masonry structures. Key novelties of this review include: (i) in-depth analysis of the influence of ceramic characteristics (mineralogy, particle size, pozzolanicity) and processing on reaction kinetics and phase evolution; (ii) systematic assessment of mechanical, physical and durability properties in comparison to conventional air lime mortars and cement-based grouts; (iii) elucidation of microstructural mechanisms governing performance using advanced characterization techniques; (iv) critical appraisal of test methods and standards for evaluation; and (v) rigorous discussion on potential applications in construction, conservation and repair, with case studies.

Improving the strength of metakaolin-lime based binder

Pozzolanic reaction of low-calcium metakaolin (MK) with calcium hydroxide (CH) at ambient temperature in the presence of water forms a series of hydrated phases such as tetracalcium aluminate hydrate (C4AH13), calcium silicate hydrate (C-S-H) and calcium aluminum silicate hydrate (stratlingite - C2ASH8). Stratlingite is the main crystalline phase and is responsible for the strength of the binder. Tetracalcium aluminate hydrate (C4AH13) is carbonated upon contact with air or converted to hemicarboaluminate and/or monocarboaluminate if the system contains excess carbonate phases (calcite or calcareous aggregates). However, the calcium aluminate hydrates formed after the reaction of MK with lime lose their strength over time due to their instability. Especially in a high humidity environment where there is no carbonation, the presence of both stratlingite and (CH) in the binder creates weak phases called katoite (Ca3Al2(SiO4)(OH)8) and can reduce the mechanical strength and durability. On the other hand, it has been determined that using chemical activators to increase the pozzolanic reactivity is the most feasible method, although it increases the cost of the material. In this study, it is aimed to eliminate the phases that cause katoite formation and improve the performance of the binder by using alkaline hydroxide solution in a mixture of metakaolin and slaked lime, similar to the pore solution caused by hydrated cement. For this aim, the effect of sodium carbonate (N-Na2CO3), quicklime (C-CaO) and calcite (CC-CaCO3) on the (CH-Ca(OH)2) activated metakaolin system is investigated through the experimental campaign. The preparation of the mixtures is done by the novel one-part mixing method.

THE IMPACT OF THE C12A7/CA RATIO AND THE FLUORIDE CaF2 AND AlF3 ON THE PROCESS OF HYDRATION AND HARDENING OF ALUMINA CEMENT

The effect of the ratio CaO.Al2O3/12CaO.7Al2O3, AlF3 and CaF2 on the formation of the structure and phase composition of clinker minerals of aluminate cement during hydration has been studied. It is found that after 24 hours of hydration, the main hydraulic phases in the studied cement stones are CAH10, C2AH8, AH3. It has been shown that the introduction of AlF3 and CaF2 fluorides reduces the liquidus temperature of the systems and increases the rate of CA formation. Scanning electron microscopy has revealed that the process of hydration of calcium aluminates of cement at low temperatures can be considered as simultaneous reactions.

Effects of CO2-absorbed triethanolamine solutions on strength development of cement mortars and the mechanism: Synergism of cement hydration and carbonation

In this study, the impacts of CO2-absorbed triethanolamine solutions (TEA-CO2) on the mechanical property, phase composition and micro-structure of cement mortars were investigated. The results showed that TEA-CO2 addition increased the 1d, 3d, and 28d compressive strength by 47%, 19%, and 4%, respectively, which suggests a synergistic effect of triethanolamine and absorbed CO2 on strength development of cement mortars. The enhancement is due to TEA-CO2 accelerates hydration of aluminate and silicate phases in early age. TEA-CO2 facilitated CaCO3 formation to increase cement hydration degree and modify the pore structures. However, the hydration of silicate phases was delayed slightly by TEA-CO2 at 28d. The above results provide theoretical support for further utilization of CO2 in cementitious materials.

Thermodynamic Simulation of Alkali-activated Processes of Tuff-Based Geopolymer

The quantity of tuff powder is more than that of tuff mechanized sand in the dry process, which belongs to solid waste. In this paper, tuff from Gansu, Yunnan, Jiangxi, Sichuan, and Tibet was selected as the research object, and the composition of tuff in different areas was defined. Temperature and NaOH concentration were used as variables to conduct thermodynamic simulation, so as to explore the influence of both on the products after alkali-activated. The results show that the main products of alkali-activated tuff geopolymer are sodium silicate aluminate hydrate/calcium silicate aluminate hydrate (CNASH), magnesium silicate hydrate (MSH), Gibbsite, Goethite, and Quartz, except in the Jiangxi area. The amount of CNASH increases gradually with the increase of NaOH concentration, while the amount of Quartz decreases gradually with the increase of NaOH concentration. In the range of 20°C to 100°C, temperature has a significant effect on the production of CNASH and Quartz. The production of CNASH increases first and then decreases with the increase of temperature, and reaches the maximum at about 60°C. The production of Quartz increases with increasing temperature. The conclusion of this paper is helpful in understanding the alkali-activated mechanism of tuff powder.

Experimental study of the mechanical and thermal properties of metakaolin based geopolymer stabilized soil during low temperature curing

To address the challenges associated with significant thermal disturbance and carbon emissions resulting from the conventional stabilization of frozen soil using cement, geopolymer material is used to replace cement to stabilize frozen soil. The unconfined compressive strength (UCS) of the geopolymer stabilized soil was investigated in relation to the proportions of metakaolin (MK), calcium carbide slag (CCS), curing temperature, and curing age. Microscopic analysis was conducted to unveil the stabilized mechanism. The UCS, shear strength, thermal conductivity, hydration products and microstructure of geopolymer stabilized soil and cement soil were compared in parallel. A total of 240 experiments were conducted in this study. The outcomes indicate that the optimal content of MK and CCS is 10% and 6% respectively. The UCS of samples with the optimal content after 28d of curing at 20 °C, −2 °C, and − 10 °C are 3.783 MPa, 1.164 MPa, and 0.901 MPa respectively. The primary causes of the rise in UCS of the geopolymer stabilized soil are the production of amorphous calcium silicate hydrate and calcium aluminate hydrate gel as a result of the stimulation of MK based geopolymer with CCS. The UCS of the geopolymer stabilized soil decreases with a decrease in curing temperature. In frozen conditions, the expansion of ice crystals in the soil creates voids and promotes crack growth, leading to a decrease in the efficiency of geopolymerization reactions. After 28d of curing at room temperature and low temperature, the geopolymer stabilized soil with the optimal content exhibits higher UCS, failure strain, shear strength, cohesion, and internal friction angle compared to the cement soil. At all curing temperatures and ages, the geopolymer stabilized soil has a lower thermal conductivity than the cement soil. The geopolymer stabilized soil is less susceptible to low temperature curing than cement soil, demonstrating a larger amount of hydration products and a denser microstructure, according to experimental results from XRD and SEM. The results of this work offer a theoretical foundation for using geopolymer in place of cement to stabilize soils in permafrost regions.

Phase formation and hydration of alumina cements on the basis of cobalt‐molybdenum‐containing waste

AbstractThe subject of the research is features of synthesis of alumina cements on the basis of compositions of system CaO – CoO – Al2O3 – MoO3 with use of cobalt‐molybdenum‐containing waste for reception of refractory materials with a complex of the set properties. The processes of phase formation in raw mixtures have been investigated. X‐ray phase studies of clinkers fired at different temperatures and holding times proved that as a result of the interaction of the raw materials of the mixture in the material synthesizes a mixture of hydraulically active calcium mono‐ and di‐aluminate and refractory cobalt spinel, which provides the resulting complex high strength, accelerated curing time, fire resistance. The absence of phases corresponding to molybdenum compounds is explained by the fact that they are part of hydraulically active aluminates as limited solid solutions, deforming the crystal lattice and increasing hydraulic activity. Thus, it was found that the high strength of cement is due to the presence of calcium hydroaluminates such as C2AH8, aluminum hydroxide, as well as unhydrated grains of calcium aluminates, which will contribute to further long‐term strength. It is this coexistence of phases in both the crystalline and colloidal states provide high strength cement stone.

Influence of the availability of calcium hydroxide, sulphates, and alkalis on hydration of supplementary cementitious materials

The hydration of siliceous fly ash (FA), slag (S) and metakaolin (MK) with calcium hydroxide (CH) was studied at 27 °C to isolate the roles of CH, alkali and sulphate. The influence on rate of hydration was studied along with phase assemblage and strength development. While the FA was the most slowly reacting SCM, it was also the least influenced by the addition of alkalis and sulphates. For MK and S, not only the rate of hydration is influenced, but the phases formed are also affected by the amount of alkalis and sulphates. The addition of sulphates delays the hydration of alumina in S and MK. In more reactive SCMs such as MK, the availability of CH can be a limiting factor in the reaction of the SCM. The results show that to achieve maximum possible hydration and contribution to strength by SCMs, an optimisation of the alkali and sulphate content is required.

Development of CO2-integrated 3D printing concrete

3D printing concrete (3DPC) technology is a promising technique for construction due to its advantages such as no formwork is needed, fast production, automation, and high architectural freedom. However, the layer-by-layer extrusion method has stricter requirements on the rheological properties of concrete. One of challenges of this technology is how to improve the rheological properties of concrete to satisfy the conflicting requirements during pumping and after extrusion. This study proposed to use CO2 as accelerator and rheology modifier by injecting CO2 during secondary mixing to improve the rheological and mechanical properties of 3DPC. The influences of the secondary CO2 mixing on the properties of poured concrete and 3DPC were investigated. After using the secondary CO2 mixing, the setting time and workability of concrete were reduced, which contributed to the significantly improved buildability of 3DPC. This was because CO2 accelerated the hydration of tricalcium aluminate (C3A) and tricalcium silicate (C3S) during the secondary mixing. After that, they were continuously accelerated by the calcium carbonate formed during CO2 mixing. Also, the compressive strength of poured concrete was enhanced by the secondary CO2 mixing because it reduced the volume of larger pores (>200 nm) and promoted the formation of calcium silicate hydrates (C-S-H), which simultaneously slightly increased the drying shrinkage. In addition, after using the secondary CO2 mixing, the compressive strength and interlayer bond strength of 3DPC was enhanced.

A simple and efficient hydratable alumina gel‐casting method for the fabrication of high‐porosity mullite ceramics

AbstractIn this study, we have developed a method for the preparation of porous alumina‐containing ceramics by inorganic gel‐casting of hydratable alumina system. The gelation behavior of hydratable alumina in water and the high‐temperature phase evolution of alumina gels were clarified. In addition, extremely high‐porosity mullite ceramics were prepared using the hydratable alumina gel‐casting method combined with carbon fibers as the pore‐forming agent method. The as‐prepared mullite ceramics have a pore size of less than 10 μm, controllable high porosity of 90.6%–78.1%, a lightweight of 0.30–0.70 g cm−3, high compression strength of 1.41 ± 0.21–16.30 ± 0.20 MPa, low dielectric constants at 30 GHz of 1.34–1.79, the dielectric loss tangent of less than 3 × 10−3, and low thermal conductivities of 0.083–0.305 W/(m K). Lightweight, high strength, excellent dielectric properties, and outstanding thermal insulation indicate the potential of porous mullite ceramics for use in radar radomes or windows.

Effect of diethanolisopropanolamine and ethyldiisopropylamine on hydration and strength development of cement-fly ash-limestone ternary blend

Effect of diethanolisopropanolamine (DEIPA) and ethyldiisopropylamine (EDIPA) at dosages of 0.02 % and 0.05 % on hydration and strength development of cement-fly ash-limestone ternary blend is investigated. Results indicate that both dosages of DEIPA or EDIPA promote the chemical effect of limestone and the hydration of aluminates from cement and fly ash to form carboaluminates due to their complexation effect, especially 0.05 % of EDIPA. For silicates hydration, 0.02 % of DEIPA or EDIPA accelerate it with more C–S–H gel formation while 0.05 % of DEIPA or EDIPA retard it due to the excessive aluminates hydration and carboaluminates formation at 3 d. However, both dosages of DEIPA and EDIPA promote silicates hydration at 28 d. Besides, DEIPA or EDIPA at both dosages can refine the pore structure with decreased porosity due to the promoted hydration of aluminates and/or silicates and formation of hydration products, although DEIPA and EDIPA exhibit air entraining effect to cause larger pores (>1000 nm). As a result, 0.02 % of DEIPA or EDIPA increase compressive strength of the blend mortar at both 3 and 28 d while 0.05 % of DEIPA or EDIPA slightly decrease it at 3 d but increase it at 28 d. It can be concluded that DEIPA contributes to higher early strength while EDIPA contributes to higher later strength of the ternary blend at both dosages.

Electro-cementation of calcareous sand using colloidal silica (CS) nanoparticles and alumina powder

The research investigates the effectiveness of a ground improvement technique that involves the electro-cementation of an onshore calcareous sand containing 95.3% calcium carbonate through a series of laboratory experiments. Colloidal silica (CS) nanoparticles and alumina powder were introduced as pozzolanic materials in the sand, and a direct current (DC) was passed through the sand-silica-alumina mix inside an electrokinetic (EK) cell. The method resulted in the electro-cementation of the calcareous sand through the formation of calcium silicate hydrates (C–S–Hs) and calcium aluminate hydrates (C–A–Hs) as products of the pozzolanic reactions between Ca(OH)2, SiO2 and Al2O3 after electrolysis occurred. Iron-rich cements were also formed by the degradation of anodes. These newly formed compounds changed the nature of the treated soil from a granular material into a rock. Results show that the compressive strength of the resulting rock formation is significantly improved. The treatment can be considered as an artificial lithification process through which the nature of the treated soil was changed from a granular material into a rock formation. The electro-cementation achieved by the treatment was further assessed by spectroscopic analyses including FE-SEM, EDX and XRD, which confirmed the formation of cementing agents within the structure of the treated sand. Potential applications of the technique include caissons, highway construction projects, dune fixation and erosion control, in addition to liquefaction mitigation due to electrolysis of pore water and plugging the pores with cementitious materials.

Corrosion mechanism of reactive MgO‐bonded Cr2O3‐bearing castables in CaO–Al2O3–Fe2O3–SiO2‐based steel‐making slag

AbstractTo assess the feasibility of the reactive MgO (RM) binder in preparing Cr2O3‐bearing castables, the degradation behavior of RM‐bonded Cr2O3‐bearing castables in CaO–Al2O3–Fe2O3–SiO2‐based steel‐making slag was investigated at 1600°C via refractory cup testing. The corrosion resistance and infiltration resistance of RM‐bonded castables were compared with hydratable alumina (HA)‐bonded and calcium aluminate cement (CAC)‐bonded castables with respect to the differences in phase composition and microstructure. Al2O3 grains in RM‐bonded castable were preferentially attacked by the slag compared with Mg(Al, Cr)2O4 spinel‐based matrix. The formation of spinel‐based and CaO·6Al2O3‐based solid solutions with volume expansion from slag/castable interactions suppressed slag infiltration into RM‐bonded castable matrix. Both experimental observations and thermodynamic calculations indicated that the in situ formed Mg(Al, Cr)2O4 spinel in RM‐bonded castables was the predominant reason leading to the superior slag corrosion resistance and infiltration resistance compared with HA‐bonded and CAC‐bonded Cr2O3‐bearing castables.