Introduction

In modern high-temperature industrial applications, the performance of refractory materials directly impacts production efficiency and equipment longevity. Magnesia dolomite bricks, also known as magnesia-calcium bricks, serve as essential alkaline refractory materials in metallurgy, cement, glass, and other industries. However, these materials face a critical technical challenge: hydration deterioration. Understanding how to improve dolomite brick hydration resistance is crucial for manufacturers, contractors, and facility operators seeking to maximize material performance and service life.

Dolomite refractory bricks, containing free CaO, are prone to hydration and cracking in the air, and are not suitable for long-term storage. This hydration issue not only causes strength reduction and volume expansion but can also lead to structural failure in kilns and furnaces, significantly affecting operational safety. This comprehensive guide explores proven methods to enhance anti-hydration performance in dolomite refractory products, providing technical insights for industry professionals.

Understanding Dolomite Bricks: Composition and Applications

What Are Magnesia Dolomite Bricks?

Magnesia dolomite bricks, commonly referred to as magnesia-calcium bricks or dolomite refractory bricks, are alkaline refractory materials manufactured from dolomite ore (CaMg(CO₃)₂) through high-temperature calcination and forming processes. The primary chemical components include magnesium oxide (MgO) at 40-60% and calcium oxide (CaO) at 30-40%. These bricks belong to the MgO-CaO refractory system, featuring a microstructure composed of periclase (MgO), calcium magnesium olivine (Ca₂MgSiO₄), and related mineral phases.

The economic advantages of dolomite bricks are substantial. With abundant dolomite deposits worldwide, production costs are 30-50% lower than pure magnesia bricks, making them an ideal choice for various industrial applications. Dolomite refractories exhibit excellent resistance to alkaline slag corrosion and maintain high-temperature strength, properties derived from their unique mineral composition and microstructure.

Industrial Applications of Dolomite Refractory Bricks

Metallurgical Industry Applications

The metallurgical sector represents the most significant application area for dolomite bricks. In steel-making converters, these refractories line critical zones including the furnace bottom and slag line. They are widely used in alkaline converters. During converter operations, highly alkaline molten slag creates severe chemical erosion conditions, where dolomite bricks’ superior alkaline slag resistance enables effective protection. In electric arc furnace steelmaking, these materials serve as furnace wall and roof linings, with excellent thermal shock stability accommodating frequent heating and cooling cycles. Additionally, dolomite refractories play vital roles in secondary metallurgy equipment such as ladle furnaces and vacuum degassing units.

Cement Industry Applications

Within cement manufacturing, dolomite bricks primarily line the burning and transition zones of rotary kilns. Dolomite bricks exhibit excellent high-temperature resistance. They can withstand temperatures up to 1800°C (3272°F) or even higher, depending on the specific composition and manufacturing process. Cement clinker calcination requires temperatures of 1400-1500°C, accompanied by alkaline oxide volatilization and condensation cycles. Dolomite bricks not only withstand these severe temperature conditions but also demonstrate strong resistance to alkaline vapor attack. In precalciner kiln systems, these refractories find extensive use in calciners and kiln rear sections.

Non-Ferrous Metal Smelting

Dolomite bricks serve copper, nickel, lead-zinc, and other non-ferrous metal smelting furnace linings. These processes involve complex slag systems and diverse erosion mechanisms, requiring the chemical stability and thermodynamic properties that dolomite refractories provide. In copper converters and nickel flash furnaces, dolomite brick service life reaches 100-200 heats, significantly outperforming alternative refractory types.

Glass Industry Specialized Applications

Certain glass industry applications also employ dolomite bricks. In glass tank furnace regenerators and auxiliary facilities, these refractories offer good high-temperature performance at economical costs. While primary melting zones typically utilize premium materials like fused cast AZS blocks, dolomite bricks in non-critical areas help reduce overall construction expenses.

The Critical Importance of Hydration Resistance

The hydration problem represents the primary technical obstacle limiting widespread dolomite brick adoption. This issue’s severity manifests throughout the material lifecycle from production through storage, transportation, and application.

Storage Phase Hydration Hazards

Dolomite bricks products have poor water resistance, high packaging and storage costs, even built into the rotary kiln. Calcium oxide in dolomite bricks exhibits strong hygroscopic properties. Under ambient temperature and humidity conditions, CaO reacts with atmospheric water vapor to form calcium hydroxide (Ca(OH)₂). This reaction accompanies significant volume expansion—calcium hydroxide’s molar volume exceeds calcium oxide by approximately 44%. Volume expansion generates tremendous internal stresses within brick bodies, causing cracking, powdering, or complete disintegration. Untreated dolomite bricks stored in environments exceeding 60% relative humidity may show obvious hydration signs within 1-2 weeks, manifesting as surface dusting and strength reduction.

Transportation Hydration Risks

Transportation phase hydration risks warrant equal concern. Inadequate packaging or exposure to rain and humidity during transit triggers rapid hydration reactions. Multiple documented cases show that even ordinary plastic film packaging, due to poor sealing or film damage, resulted in severe dolomite brick hydration during long-distance shipping, causing total product loss and significant economic damage.

Construction Installation Phase Impacts

Hydration effects during construction and installation occur in multiple ways. First, partially hydrated bricks experience strength reduction, becoming susceptible to damage during handling and installation, increasing waste rates and construction difficulty. Second, post-installation hydration issues prove more insidious yet consequential. Using partially hydrated bricks for kiln construction can cause calcium hydroxide decomposition and dehydration at 400-500°C during furnace drying and heating, generating renewed volume changes and stress concentrations that may induce lining cracks and displacement. Such drying phase damage often necessitates reconstruction, causing schedule delays and cost increases.

Long-Term Service Impacts

Long-term service impacts also require attention. Even when dolomite bricks show no obvious pre-service hydration, during furnace intermittent operation or maintenance periods, inadequate humidity control may permit slow hydration reactions in the lining. This accumulated hydration damage gradually weakens structural integrity, shortening furnace service life and increasing maintenance frequency and costs.

Research data indicates dolomite brick hydration rates closely correlate with environmental temperature and relative humidity. At 20°C and 80% relative humidity, untreated dolomite brick surface CaO conversion reaches 30-40% within 7 days and 60-70% within 28 days. This hydration rate far exceeds other alkaline refractory types, highlighting the urgency and importance of anti-hydration treatment.

Scientific Understanding of Dolomite Brick Hydration Mechanisms

Thermodynamic and Kinetic Foundations of Hydration Reactions

Understanding dolomite brick hydration mechanisms provides the foundation for developing effective anti-hydration technologies. Extensive research demonstrates that MgO-CaO system refractory hydration primarily occurs below 763K (approximately 490℃), where water vapor significantly promotes CaO hydration. This finding indicates that controlling CaO hydration below 763K or at low temperatures represents the key to achieving superior anti-hydration performance in MgO-CaO refractory materials.

From a thermodynamic perspective, CaO hydration (CaO + H₂O → Ca(OH)₂) exhibits large negative free energy change at ambient temperature (ΔG° ≈ -58 kJ/mol), indicating strong spontaneous reaction tendency. Comparatively, while MgO hydration (MgO + H₂O → Mg(OH)₂) is thermodynamically feasible, its reaction rate at ambient temperature proves extremely slow and negligible under practical storage and service conditions. This difference stems from the distinct crystal structures and chemical bond properties of these two oxides.

Kinetic studies reveal hydration reaction process mechanisms. CaO hydration begins at grain surfaces, where water molecules adsorb onto CaO surface active sites, followed by chemical bond breaking and reorganization. Generated Ca(OH)₂ layers cover unreacted CaO surfaces, forming product layers. If Ca(OH)₂ layers remain loose, porous, and discontinuous, water vapor continues diffusing through product layers to internal unreacted CaO, sustaining reactions; if dense continuous product layers form, further hydration becomes hindered and reaction rates significantly decrease. This understanding provides theoretical basis for surface treatment anti-hydration technologies.

Temperature effects on hydration reactions exhibit complex nonlinear characteristics. Within the room temperature to 200°C range, temperature increases accelerate hydration reactions by providing more activation energy while increasing water molecule diffusion rates. However, when temperatures exceed 400°C, Ca(OH)₂ begins decomposing and dehydrating, effectively reversing hydration reactions. This explains why hydration primarily occurs below 763K. During furnace drying processes, controlling heating rates and dwell times at critical temperature intervals holds significant importance for reducing hydration damage.

Humidity represents another critical factor affecting hydration reactions. Relative humidity determines atmospheric water vapor partial pressure, influencing water molecule adsorption rates and concentrations on CaO surfaces. Research shows that when relative humidity remains below 30%, hydration reaction rates prove very slow; when relative humidity exceeds 60%, reaction rates significantly accelerate; at relative humidity approaching 100% or with liquid water presence, reactions become most vigorous. This pattern guides humidity control standards for dolomite brick storage environments.

Microstructural Influences on Hydration Behavior

Dolomite brick microstructural characteristics significantly influence hydration behavior. Porosity ranks as one of the most important structural parameters. High porosity means greater specific surface area and more water vapor transport channels, facilitating hydration reaction occurrence and progression. Research indicates that increasing porosity from 15% to 25% may elevate hydration rates 2-3 times. Therefore, optimizing firing processes to reduce porosity represents a fundamental approach to improving anti-hydration performance.

Pore size distribution and connectivity prove equally important. Open pores provide direct channels for water vapor penetration into brick interiors, while closed pores relatively isolate hydration reactions. High pore connectivity allows hydration not only at surfaces but deep penetration into interiors, causing more extensive damage. Electron microscopy observation and mercury intrusion testing reveal that hydration primarily proceeds along medium and large pores ranging from 0.1-10 micrometers in diameter.

Grain size and distribution also affect hydration behavior. Fine CaO grains possess greater specific surface area and higher surface energy, more readily undergoing hydration reactions. Conversely, coarse grains with smaller surface areas exhibit relatively slower hydration rates. However, if CaO exists as free phases widely distributed throughout the matrix, regardless of grain size, it poses hydration risks. Therefore, controlling raw material ratios and firing processes to promote CaO existence as solid solutions or composite mineral phases represents an important strategy for enhancing anti-hydration performance.

Sintering Methods for Enhancing Hydration Resistance

Sintering methods improve dolomite brick anti-hydration performance by modifying firing processes or adding specific substances during firing to fundamentally improve material microstructure and chemical composition. These methods offer advantages of lasting, stable effects independent of external protection, suitable for long-term storage and service.

Activated Sintering Techniques

Activated sintering methods include two primary technical approaches: two-step calcination and hydration-recalcination processes.

Two-Step Calcination Method

The two-step calcination method’s basic principle involves two heat treatments at different temperatures and atmospheres to optimize material phase composition and microstructure. First-step calcination typically occurs at lower temperatures (1400-1600℃), decomposing dolomite into MgO and CaO mixtures without complete sintering, maintaining relatively high reactivity. Second-step calcination proceeds at higher temperatures (1700-1900℃), promoting solid-state reactions between MgO and CaO, generating stable composite mineral phases such as calcium magnesium olivine (Ca₂MgSiO₄) or calcium-magnesium periclase solid solutions (Ca,Mg)O. These composite phases exhibit superior chemical stability compared to free CaO, significantly reducing hydration tendencies.

The key to two-step calcination lies in precisely controlling both calcination stages’ temperatures, durations, and atmospheres. If first-step calcination temperature proves too high or duration excessive, raw materials may over-sinter, reducing second-step reaction efficiency; if second-step calcination conditions prove insufficient, stable composite phase formation remains incomplete. Practice demonstrates that optimized two-step calcination processes can improve dolomite brick anti-hydration performance by 50-80%, extending storage periods in 70% relative humidity environments from original 2-3 weeks to 2-3 months.

Hydration-Recalcination Method

The hydration-recalcination method represents a specialized activated sintering technique. This approach first subjects dolomite brick green bodies or fired bricks to controlled moderate hydration treatment, converting surface or shallow layer CaO to Ca(OH)₂, followed by high-temperature refiring. During refiring, Ca(OH)₂ decomposes and dehydrates, regenerating CaO, but this newly formed CaO exhibits finer grain size and more uniform dispersion, more readily reacting with surrounding MgO or silicate phases to form stable composite phases. Simultaneously, hydration-dehydration cycling-induced volume changes introduce microcracks within materials that heal through sintering and phase reactions during refiring, ultimately achieving denser microstructures.

The hydration-recalcination method’s advantage lies in improving material homogeneity and eliminating large particle free CaO presence. However, this method demands extremely high process control, requiring precise management of hydration degree, uniformity, and refiring temperature regimes. Inadequate control may cause brick cracking or performance deterioration. Currently, this method primarily finds laboratory research application, with industrial implementation requiring further process optimization and equipment improvements.

Additive Sintering Methods

Additive sintering methods involve incorporating specific additives into dolomite brick formulations that undergo physicochemical interactions with matrix components during firing, improving material phase composition and microstructure to enhance anti-hydration performance. Based on additive action mechanisms, these can be categorized as follows:

Liquid Phase Forming Additives

Liquid phase forming additives primarily include Al₂O₃, Fe₂O₃, SiO₂ and other oxides, plus nitrides, boron carbide, metallic boron, metallic aluminum and other non-oxides and metals. These additives react with CaO and MgO during firing, generating low-melting-point liquid phases. Liquid phase presence promotes material migration and redistribution, accelerating sintering processes, achieving denser microstructures at lower temperatures while reducing porosity. Simultaneously, liquid phases cooling and solidifying form glassy phases or low-melting-point mineral phases filling intergranular spaces, sealing pore channels and obstructing water vapor inward diffusion.

Al₂O₃ ranks among the most commonly used liquid phase forming additives. Adding 3-8% Al₂O₃ to dolomite bricks generates composite phases including calcium aluminum anorthite (CaAl₂Si₂O₈), calcium aluminum olivine (Ca₂Al₂SiO₇), and minor calcium aluminate liquid phases during firing. These phase formations not only reduce free CaO content but also improve matrix density. Research indicates that adding appropriate Al₂O₃ quantities increases dolomite brick bulk density by 5-10%, reduces apparent porosity by 3-5%, improves ambient temperature compressive strength by 20-30%, and significantly enhances anti-hydration performance.

Fe₂O₃ addition quantities typically remain controlled at 1-3%. Iron oxides react with CaO during firing to generate low-melting-point calcium ferrite phases (CaFe₂O₄, Ca₂Fe₂O₅), forming liquid phases at 1300-1500℃ temperature ranges that promote sintering. However, excessive Fe₂O₃ additions may reduce material high-temperature performance and slag corrosion resistance. In practice, Fe₂O₃ typically combines with Al₂O₃ for synergistic effects.

SiO₂ as an additive requires cautious application. While SiO₂ can react with CaO and MgO to generate calcium magnesium olivine, forsterite and other silicate phases beneficial for reducing free CaO content, SiO₂ additions lower material alkalinity, potentially affecting alkaline slag resistance. Therefore, SiO₂ addition quantities typically remain below 2%, or pre-synthesized silicate minerals serve as raw materials rather than direct SiO₂ additions.

Solid Solution Forming Additives

Solid solution forming additives include CeO₂, ZrO₂, Y₂O₃, Cr₂O₃ and other oxides. These oxides possess crystal structures similar to CaO or MgO, enabling entry into periclase or lime lattices during firing to form solid solutions. Solid solution formation effectively “locks in” CaO, preventing free state existence, thereby reducing hydration tendencies. Simultaneously, solid solution formation improves intergranular bonding, enhancing material overall strength and stability.

ZrO₂ ranks among the most effective solid solution forming additives. Research demonstrates that adding 2-5% ZrO₂ to dolomite bricks significantly improves anti-hydration performance. ZrO₂-CaO solid solutions exhibit very high stability, resisting decomposition under hydration conditions. However, ZrO₂’s high cost limits large-scale application in ordinary dolomite bricks, primarily serving premium products or critical applications.

CeO₂ and Y₂O₃ are rare earth oxides also possessing solid solution forming capabilities. These rare earth oxide additions typically range from 0.5-2%, improving material high-temperature performance and thermal shock resistance while enhancing anti-hydration performance. High rare earth oxide costs represent the primary application-limiting factor.

Surface Treatment Methods for Hydration Resistance

Surface treatment methods involve forming protective water-barrier layers on fired dolomite brick surfaces, isolating water vapor contact with internal CaO to prevent hydration reactions. These methods offer advantages of simple processes, low costs, and quick effects, suitable for implementation during production, storage, and transportation phases.

Organic Coating Treatments

Organic coating technologies utilize various organic solvents or compounds to form hydrophobic films on brick surfaces, preventing moisture penetration.

Paraffin Wax Treatment (Wax Dipping)

Paraffin wax treatment currently represents the most widely applied and mature organic coating technology. Paraffin wax consists of long-chain hydrocarbon solid waxy substances with melting points typically at 50-70℃, exhibiting excellent hydrophobic properties and good chemical stability. Standard wax dipping process procedures include:

First, heat paraffin wax to liquid state, controlling temperature at 80-100℃. Excessively low temperatures increase paraffin viscosity, hindering penetration; excessively high temperatures may cause paraffin decomposition or adversely affect treatment by overheating brick surfaces. Simultaneously, preheat dolomite bricks to 60-100℃. Preheating purposes include removing adsorbed surface moisture while providing brick temperature that facilitates liquid paraffin wax infiltration into surface pores when bricks contact it.

Next, immerse preheated bricks into liquid paraffin wax baths for 5-15 minutes. Immersion duration depends on brick porosity and desired protection depth. During immersion, liquid paraffin penetrates surface pores through capillary action while forming films on surfaces. To ensure uniform coating, bricks may require turning or agitating several times during immersion.

After immersion, remove bricks from wax baths and allow cooling in air. During cooling, paraffin within pores solidifies while surface films harden. Completely cooled bricks develop approximately 10 micrometer-thick paraffin protective films. This film effectively seals brick surfaces while blocking water vapor intrusion channels. Some manufacturers apply multiple wax dipping treatments to achieve thicker, more uniform protective layers.

Paraffin wax treatment offers multiple advantages. First, treatment processes prove simple and feasible, requiring no complex equipment, suitable for various production scales. Second, paraffin wax costs remain low as petroleum refining byproducts, not significantly increasing product costs. Third, paraffin wax exhibits good hydrophobic performance, effectively preventing water vapor erosion, extending dolomite brick storage periods to 1-3 months. Fourth, during kiln construction after packaging removal, paraffin films temporarily protect bricks during short-term handling and installation.

However, paraffin wax treatment also presents certain limitations. First, protective film mechanical strength remains relatively low, susceptible to damage during handling and transportation, reducing protective effectiveness. Second, during furnace heating, paraffin combustion generates smoke that may temporarily affect working environments. Third, paraffin protective effects prove time-limited, long-term storage still requiring supplementary waterproof packaging protection.

Other Organic Treatment Agents

Beyond paraffin wax, various other organic materials serve for dolomite brick surface protection, including:

Fatty alcohols and fatty acids: These substances possess good hydrophobic properties, forming thin protective films on brick surfaces. Compared to paraffin wax, fatty alcohols and acids exhibit lower viscosities, more easily penetrating finer pores, but protective durability generally proves inferior to paraffin wax.

Resin coatings: Various synthetic resins such as epoxy resins, polyurethane resins, acrylic resins, etc., can formulate coatings applied to dolomite brick surfaces. Resin coatings offer superior mechanical strength and durability compared to paraffin wax, but costs prove higher, primarily used for high-end products or special application scenarios.

Organosilicon compounds: Organosilicon waterproofing agents exhibit excellent hydrophobic properties and high-temperature stability. These compounds undergo chemical reactions with brick surface hydroxyl groups, forming covalent bonds that provide lasting waterproof effects. Organosilicon treatment typically involves diluting organosilicon compounds with organic solvents, then brushing or spraying onto brick surfaces. After solvent evaporation, organosilicon compounds react with surfaces to form hydrophobic layers. This method offers excellent protective effects but relatively high costs.

Organic acid-organic salt complexes: Certain organic acids (such as stearic acid, oleic acid) and their salts can form protective layers on dolomite brick surfaces. These substances react with surface calcium compounds to generate water-insoluble organic calcium salts covering surfaces. This method proves simple and low-cost but protective effects and durability remain limited.

It should be noted that while asphalt and coal tar represent traditional organic coating materials with good hydrophobic properties and low costs, they generate substantial volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) during application and curing, harmful to environments and human health. During furnace heating, asphalt combustion produces dense smoke and irritating odors, polluting working environments. Due to these drawbacks, many modern enterprises have discontinued asphalt and coal tar applications.

Inorganic Coating Treatments

Inorganic coating treatments involve using inorganic substances to form protective layers on dolomite brick surfaces. Compared to organic coatings, inorganic coatings generally exhibit superior high-temperature stability and do not generate harmful gases during furnace heating, offering environmental advantages.

Vapor Phase Coating

Vapor phase coating primarily involves reacting brick surfaces with carbon dioxide gas to form thin calcium carbonate films. The reaction equation: CaO + CO₂ → CaCO₃. This calcium carbonate film possesses certain densities that can block water vapor infiltration, slowing hydration reactions.

Vapor phase coating implementation involves placing dolomite bricks in carbon dioxide atmospheres under controlled temperature and humidity conditions for specified durations. CO₂ reacts with surface free CaO to generate CaCO₃ films. This method’s advantage lies in simple processes without additional chemical reagents, with generated CaCO₃ proving chemically stable and harmless to environments.

However, vapor phase coating effectiveness remains limited. Generated CaCO₃ films typically prove very thin (several to tens of micrometers), providing limited long-term protection. Additionally, CaCO₃ decomposes at temperatures exceeding 800℃, reverting to CaO and CO₂, meaning this method only provides temporary protection during storage and transportation, ineffective during high-temperature service.

Liquid Phase Coating Solutions

Liquid phase coating involves applying various inorganic solution treatments to dolomite brick surfaces. These solutions react with surface free CaO to generate sparingly soluble or insoluble compounds coating surfaces, preventing water contact with internal CaO. Commonly used solutions include:

Phosphoric acid and phosphate solutions: Phosphoric acid (H₃PO₄), sodium phosphate (Na₃PO₄), aluminum dihydrogen phosphate (Al(H₂PO₄)₃), etc., react with surface CaO to generate calcium phosphate compounds. These phosphate compounds exhibit low water solubility, forming protective layers on surfaces. Phosphate treatment typically involves brushing or immersing brick surfaces in phosphate solutions, followed by drying. This method offers good protective effects with relatively low costs, widely applied industrially.

Sodium silicate solutions: Sodium silicate (Na₂SiO₃, water glass) reacts with CaO to generate calcium silicate compounds, similarly possessing low water solubility. Sodium silicate treatments require controlling solution concentrations and pH values to ensure appropriate reaction rates and product layer qualities.

Oxalic acid solutions: Oxalic acid (H₂C₂O₄) reacts with CaO to generate calcium oxalate (CaC₂O₄). Calcium oxalate exhibits extremely low water solubility, providing good protective effects. However, oxalic acid possesses certain toxicities, requiring safe handling precautions during application.

Liquid phase coating solution advantages include simple operation, low costs, and significant hydration resistance improvements. However, solution treatment depths typically remain limited to surface shallow layers (several millimeters), with long-term effectiveness dependent on coating layer integrity and density. During handling and transportation, coating layer damage may reduce protective effects.

Construction and Installation Recommendations

During kiln or furnace construction and installation phases, following measures help prevent dolomite brick hydration damage:

Pre-Installation Inspection: Thoroughly inspect bricks before installation for hydration signs (surface dusting, cracking, strength reduction, etc.). Reject hydrated bricks, preventing compromised structural integrity.

Rapid Installation: Minimize brick atmospheric exposure time after package opening. Plan installation sequences and schedules rationally, opening only immediately needed brick quantities. Temporarily unused bricks should remain in original packaging or receive provisional waterproof covering.

Environmental Control: Maintain reasonably dry construction site environments, avoiding rainy day installations. If unavoidable, implement temporary sheltering measures preventing direct brick moisture exposure.

Proper Drying Procedures: After kiln construction completion, implement appropriate drying and heating procedures. Control heating rates particularly carefully in 400-500℃ temperature ranges where calcium hydroxide decomposes, avoiding excessive stress generation. Gradual heating allows sufficient moisture evaporation and residual hydration product decomposition, preventing structural damage.

Frequently Asked Questions (FAQ)

Q1: What causes dolomite bricks to hydrate?

A1: Dolomite brick hydration primarily results from free calcium oxide (CaO) in brick compositions reacting with atmospheric water vapor or moisture. This chemical reaction (CaO + H₂O → Ca(OH)₂) is thermodynamically favorable at ambient temperatures and generates significant volume expansion (approximately 44% molar volume increase), causing internal stresses that lead to cracking, powdering, or complete brick disintegration.

Q2: How long can untreated dolomite bricks be stored?

A2: Untreated dolomite bricks prove unsuitable for long-term storage. In environments exceeding 60% relative humidity, obvious hydration signs may appear within 1-2 weeks. At 20℃ and 80% relative humidity, surface CaO conversion rates can reach 30-40% within 7 days and 60-70% within 28 days. Therefore, untreated bricks require immediate use after production or proper protective treatment application.

Q3: Which anti-hydration method proves most effective?

A3: No single “most effective” method exists; optimal approaches depend on specific application requirements and economic considerations. For long-term storage (over 6 months), aluminum foil vacuum packaging combined with surface treatments proves most reliable. For typical industrial applications (1-3 month storage), paraffin wax treatment with proper waterproof packaging provides good cost-performance balance. For permanent performance improvement, additive sintering methods incorporating ZrO₂ or Al₂O₃ offer superior results though at higher costs.