コンクリート発泡剤: The Definitive Guide to Lightweight Cellular Concrete

A concrete foaming agent is a chemical surfactant that, when diluted with water and aerated through specialized equipment, generates a stable foam. That foam, when blended into a cementitious slurry, creates millions of discrete air voids, yielding a lightweight, cellular 材料 known as foamed concrete. The entire performance of the final product — its density, compressive strength, thermal conductivity, and long-term durability — hinges on the foaming agent’s chemistry, 希釈倍率, and the consistency of the mixing process. No other component in the mix has a greater impact on the bubble structure.

What Is a Concrete Foaming Agent and How Does It Work?

At its core, a concrete foaming agent reduces the surface tension of water, allowing air to be trapped as stable bubbles. The process begins when the agent is mixed with water at a precise ratio — typically between 1:20 そして 1:50 体積で, depending on the product’s concentration and the target foam density. This solution is then fed into a foam generator, where compressed air forces it through a series of constrictions or a packed bed, shearing the liquid into a dense, uniform foam. The foam’s density is measured in grams per liter; a well-prepared foam for structural lightweight concrete falls between 70 g/L and 90 g/L. Lower densities (40 g/L to 60 g/L) produce insulating fills, while higher densities (100 g/L to 150 g/L) are reserved for load-bearing blocks.

The foam is then injected into a separately mixed cement slurry, which already contains cement, 水, and often a superplasticizer or concrete water reducer to maintain workability without excess water. The slurry and foam are blended under controlled shear — too low, and bubbles clump; too high, and they burst. The resulting mix is cast, self-levels, and cures into a hardened matrix of air cells bound by hydrated cement paste. あ コンクリート発泡剤 does not participate in the hydration reaction. It simply creates and stabilizes the air voids until the cement sets.

Key Types of Foaming Agents: 合成 vs. プロテインベース

Industry practice divides 発泡 agents into two dominant chemistries: synthetic surfactants and protein-based hydrolyzates. Each behaves differently, and selecting the wrong type for your application is a direct path to failure.

Synthetic foaming agents are typically blends of alkyl ether sulfates or alpha-olefin sulfonates. They produce a lighter, finer foam with excellent air content — often exceeding 80% 体積で. The foam bubbles are small, generally 0.1 mm to 0.5 mm in diameter, and they yield a smooth, uniform cell structure in the hardened コンクリート. Synthetic agents are the standard for precast blocks, パネル, and floor screeds because they allow precise density control. Their drawback: lower foam stability under high pumping pressures. If your mix requires pumping over 50 メートル, synthetic foams may collapse.

タンパク質ベースの発泡剤 are derived from animal keratin (typically hoof and horn meal) through alkaline hydrolysis. They produce a stiffer, more resilient foam with larger bubbles (0.5 mm to 1.5 mm). This foam resists collapse under mechanical shear and high-pressure pumping, making protein agents the choice for geotechnical fills, tunnel void grouting, and deep foundation applications. The trade-off is a coarser cell structure, which can reduce compressive strength by 10% に 15% at the same density compared to a synthetic system. Experienced engineers specify protein agents only when the environment demands robust foam survival; they never use them for high-finish architectural panels.

Hybrid products exist, but the market splits cleanly. Synthetic for precision, protein for punishment. If your equipment includes a foam generator with a metering pump, calibrate it daily. A variance of ±2 g/L in foam density can shift final concrete density by 20 kg/m3.

Main Applications of Foamed Concrete

Foamed concrete produced with a concrete foaming agent serves four primary markets, each with distinct formulation constraints.

Void filling and geotechnical use accounts for roughly 40% of global consumption. Contractors pour foamed concrete into abandoned pipelines, old sewer lines, mine voids, and behind retaining walls. Density targets are 300 kg/m3 から 600 kg/m3. Compressive strength is secondary to flowability and low settlement. Protein-based agents dominate here because the foam must survive pumping distances of 100 meters or more.

Thermal insulation applications — roof screeds, floor underlays, and wall cavity fills — require densities between 400 kg/m3 と 800 kg/m3. Thermal conductivity at these densities ranges from 0.10 W/mK to 0.25 W/mK. Synthetic agents are preferred because they produce finer cells, which trap more air and reduce heat transfer. あ 50 mm layer of 500 kg/m³ foamed concrete delivers the same R-value as 100 mm of expanded polystyrene, but with none of the combustibility concerns.

Precast blocks and panels demand consistent density from batch to batch. Manufacturers target dry densities of 600 kg/m3 から 1200 kg/m3. Synthetic foaming agents, combined with a superplasticizer and early strength agent, allow demoulding within 12 hours in warm climates. The blocks require no autoclaving. A standard block plant can convert to foamed concrete production for less than $50,000 in equipment upgrades.

Sound absorption is a growing application. Open-cell foamed concrete, achieved by reducing the foaming agent dosage and increasing the water-to-cement ratio, absorbs up to 0.7 NRC (noise reduction coefficient) at mid-frequencies. This is competitive with mineral wool but with far greater structural integrity.

Benefits Over Traditional Lightweight Methods

Foamed concrete competes directly with lightweight aggregate concretes — those using expanded clay, パーライト, or pumice. The numbers tell the story. A cubic meter of foamed concrete at 800 kg/m³ costs roughly 30% less than the equivalent lightweight aggregate mix because no expensive aggregates are purchased or transported. The material is self-leveling, eliminating vibration labor. And because it is monolithic, there are no aggregate segregation zones that create weak planes.

Fire resistance is another clear advantage. あ 100 mm slab of 800 kg/m³ foamed concrete achieves a 4-hour fire rating without additional coating. Expanded clay concrete at the same weight requires 120 mm of thickness to reach 3 時間. The air cells act as thermal barriers, preventing heat conduction.

Dead load reduction is the primary driver in high-rise construction. Replacing a standard 24 MPa structural concrete slab (2400 kg/m3) with a 1200 kg/m³ foamed concrete slab reduces the building weight by 50%. Foundations can be downsized. In a 20-story building, that saves $150,000 に $300,000 in foundation steel alone.

Critical Factors Affecting Foam Quality

Three variables determine foam quality: 希釈倍率, foam density, and stability over time. Ignore any one, and the entire pour is at risk.

Dilution ratio must follow the manufacturer’s specification exactly. If a product calls for 1 part agent to 40 部品の水, using 1:30 produces a thicker bubble film that resists collapse but also increases final concrete density by 30 に 50 kg/m3. Too lean (1:50), and the foam drains water, creating large coalesced voids. Measure volumes with graduated cylinders. 目に入らないでください.

Foam density is measured by collecting a fixed volume of foam (通常 1 liter) from the generator and weighing it. A stable synthetic foam at 80 g/L should not change density by more than ±5 g/L over 10 minutes when left undisturbed. If it does, the agent or generator is failing. Protein foams are more tolerant, but they should be tested after 20 minutes of standing.

Stability over time is checked by the drainage test. Place 500 mL of foam on a coarse sieve (2 mm mesh) and measure the liquid that drains in 30 分. Acceptable drainage for a synthetic foam is less than 50 mL. For protein foam, less than 30 mL. If drainage exceeds these limits, the foam will collapse in the mixer before the cement sets.

How to Properly Mix Foaming Agent with Cement Slurry

Mixing sequence is non-negotiable. 初め, prepare the cement slurry in a conventional mixer — typically a forced-action pan mixer or a truck mixer. Use special cement or ordinary Portland cement, but note that high-alkali cements (above 0.6% Na₂O equivalent) can destabilize synthetic foams. Add a concrete defoamer only if you are having persistent bubble collapse; otherwise, avoid it.

2番, generate the foam separately in a dedicated foam generator. The foam stream must be kept at a consistent pressure — usually 4 に 6 bar at the generator outlet. Connect the foam hose directly to the mixing chamber or the truck mixer chute.

三番目, blend foam into slurry for exactly 60 に 90 seconds at low speed. Overmixing collapses cells. Undermixing leaves foam pockets. The final mix should appear uniform, with no streaks of unmixed slurry or visible foam clumps. For precast work, target a flow spread of 180 mm to 220 mm on a flow table. For void fills, a spread of 250 mm to 300 mm is acceptable.

4番目, cast immediately. Foamed concrete does not remain stable beyond 20 minutes after mixing. If the mixer truck sits idle for longer, the foam degrades and density rises. Pour in a continuous stream. Stop-and-go casting produces cold joints and density gradients.

Common Challenges and Their Mitigations

Foam collapse is the most frequent failure. The root cause is usually an incompatible foaming agent with the cement chemistry. Test a small batch before every large pour. Mix 1 liter of slurry with 0.5 liters of foam and observe. If bubbles disappear within 5 分, change the agent or add a stabilizer like hydroxypropyl methyl cellulose at 0.05% セメントの重量で.

Water absorption in foamed concrete is 10% に 25% 体積で, に比べ 4% に 6% for normal concrete. This is inherent to the air-void structure. Mitigate by using a water-repellent admixture or a silane-based sealer. For exterior applications, always apply a breathable coating. Never use foamed concrete in direct contact with chloride-bearing soils unless a waterproof membrane is installed.

Strength reduction is linear with density. For every 100 kg/m³ decrease in dry density, compressive strength drops approximately 1 MPa to 1.5 MPa. To recover strength without increasing density, add silica fume (5% に 10% セメントの重量で) or amorphous nano-modifiers. These fill the inter-bubble spaces without closing the air cells. Alternatively, incorporate alkali-resistant glass fibers at 0.5% に 1% by volume to improve tensile capacity and crack resistance.

Compatibility with Cement Types and Additives

Not all cements behave identically. Rapid-hardening cements (CEM I 52.5R) generate heat quickly, which can destabilize synthetic foams. Use them only with protein-based agents or reduce the retarder dosage. Blended cements with fly ash (CEM II/B-V) are ideal. The fly ash acts as a foam stabilizer because its spherical particles distribute shear uniformly during mixing.

Superplasticizers (concrete water reducer) are essential. 彼らなしでは, the water demand to achieve workability would collapse the foam. Use a polycarboxylate ether-based superplasticizer at 0.5% に 1.5% セメントの重量で. Avoid naphthalene-based products; they are incompatible with many synthetic foaming agents.

Redispersible polymer powder そして hydroxyethyl cellulose are common additions for improving adhesion and water retention in thin screeds and wall coatings. Add them only after the foam is incorporated — never before. Premixing polymer with the slurry can entrain unwanted air and cause the foam generator to deliver erratic densities.

Basic Production Process and Equipment

A complete foamed concrete production line consists of four components: a cement silo and screw conveyor, a continuous slurry mixer (or pan mixer), a foam generator with a metering pump, and a delivery pump or hose system. The foam generator is the critical piece. It must be capable of delivering foam at a steady rate of 50 L/min to 300 L/min with density variation under 5%. Calibrate it every morning before production.

The mixing sequence is by volume, not by weight, for the foam component. Measure the foam output by collecting it in a 10-liter bucket for 30 seconds. Multiply by 2 to get L/min. Adjust the air pressure valve until the desired density is achieved. Then calculate the slurry volume needed. A typical recipe for 800 kg/m³ foamed concrete: 450 kg cement, 200 L water, 1.2 L superplasticizer, そして 0.8 m³ of foam at 80 g/L. The foam volume is roughly 60% of the total mix volume.

Curing conditions matter. Foamed concrete must be kept moist for 7 日. Bare air exposure at low humidity causes surface crusting, which traps moisture beneath and leads to delamination. Mist spray the surface every 4 hours for the first 48 時間. For blocks, wrap in plastic sheeting.

Safety Considerations and Storage Guidelines

Concrete foaming agents are mild irritants. Wear gloves and safety glasses when handling concentrates. Protein-based agents have a distinct ammonia odor during mixing. Ventilate the area. The concentrates are not classified as hazardous for transport but should be stored between 5°C and 30°C. 凍結すると界面活性剤の構造が破壊される. Above 40°C, bacterial growth can occur in protein-based liquids. Discard any product that develops a foul smell or visible sediment.

Shelf life is typically 12 months for synthetic agents, 6 months for protein-based. Rotate stock. Never mix old and new concentrates of different brands. Compatibility testing is mandatory if you change suppliers.

Comparison with Alternative Lightweight Methods

Expanded clay and perlite concretes are denser — typically 1000 kg/m3 から 1600 kg/m³ — and have higher thermal conductivity. They also require multiple aggregate sizes and precise grading curves. Foamed concrete wins on simplicity: two components (cement slurry and foam) produce any density from 300 に 1600 kg/m3. The single material cost difference is 25% に 40% lower.

Autoclaved aerated concrete (AAC) is a different process entirely. It uses aluminum powder to generate hydrogen gas, requires an autoclave at 12 bar pressure, and produces blocks with compressive strengths of 3 に 6 MPa. Foamed concrete for blocks achieves 2 に 5 MPa at the same density, but without the capital cost of an autoclave. For small to medium plants, foamed concrete is more economical.

Industry Standards and Testing Methods

Acceptance of foamed concrete depends on two metrics: dry density and compressive strength. Dry density is measured by oven-drying a 100 mm cube at 105°C to constant weight. The standard deviation across three samples should not exceed ±25 kg/m³. Compressive strength is tested on 100 mm cubes after 28 日, following ASTM C495 or EN 1354. The rate of loading is 1.0 MPa/sec. Samples must be capped with sulfur mortar or ground flat. あ 10% variation in strength within the same batch is normal; more than 15% indicates a mixing problem.

Thermal conductivity is tested on 300 mm x 300 mm slabs at 23°C using EN 12667. For fire resistance, test to EN 1365-2 or ASTM E119. Always request a technical datasheet from the foaming agent supplier that lists optimum dilution, foam density range, and compatibility with high-alkali cements.

The Bottom Line on Concrete Foaming Agents

Choose the right foaming agent for your specific application. Synthetic for fine-cell, high-strength blocks and insulation. Protein for pumping-heavy geotechnical fills. Calibrate your foam generator daily. Test foam stability before every pour. Control your water-to-cement ratio tightly. And never compromise on mixing time. A good agent will produce a density spread of less than ±15 kg/m³ across the entire pour. A poor one will cost you rework or structural failure.

トゥルナノ supplies a complete range of concrete foaming agents, synthetic and protein-based, with batch-tested dilution curves and technical support for your first 10 pours. We also stock compatible additives: 減水剤, early strength agents, nano-modifiers, and concrete defoamers. If you need a custom formulation for extreme densities or aggressive pumping distances, our lab can formulate a bespoke blend. Request a sample kit by visiting our website. Include your target density, cement type, and project volume. We will send the matched product with a calibrated dosing chart. Do not leave your foam to chance. Build better. Build lighter. Build with TRUNNANO.

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