A Guide to Concrete Grades: What You Need to Know

# Introduction

Concrete is the “skeleton” of a building, and choosing the right grade is essential to the safety and service life of the entire project. When faced with grades such as C15, C25, C30, and so on, do you find it difficult to understand which one to choose? This article explains the basics of concrete grades based on the Chinese concrete classification standards.

---

# Disclaimer

This article only introduces concrete grades under China’s GB national standards. Concrete grade definitions, test specimens, and measurement systems vary significantly across Europe, the United States, Southeast Asia, and other countries. Please do not directly equate Chinese C grades with concrete grades used in your local market. When selecting our concrete release agents, please provide your actual concrete mix, slump, and component type so that we can recommend a suitable dilution ratio.

---

# 1. Basics of Concrete Grades Under China’s GB Standards

# 1.1 How Are Concrete Grades Defined Under China’s GB Standards?

China’s national standard GB 50010 uses 150 mm cubic concrete specimens, tested after 28 days of standard curing, with the characteristic compressive strength based on a 95% guarantee rate, measured in MPa.

The designation is written as C + a number. For example, C30 means that the 28-day compressive strength of the cubic specimen is ≥30 MPa.

The higher the number, the higher the concrete strength. However, not every project requires the highest strength grade. Selecting the appropriate grade is essential for balancing structural performance and cost efficiency.

---

# 1.2 Overview of Common Concrete Grades in China

Strength Grade	Common Applications	Key Characteristics
C10–C15	Foundation blinding layers, road base layers, floors	Low strength, mainly used for non-load-bearing leveling
C20–C25	Multi-story residential buildings, office buildings and other conventional structures	Most commonly used grade, offering good cost performance
C30–C35	High-rise buildings, long-span bridges	Medium-to-high strength, currently a mainstream grade
C40–C50	Large bridges, heavy-duty industrial buildings, high-rise buildings, critical structural components	High strength, used for important structures
C55–C80	Super high-rise core structures, special structures	Very high strength, requiring specialized construction processes

---

# 1.3 Key Differences Between Chinese and Overseas Concrete Grades — Test Specimens Are Different

• China: 150 mm cubic concrete specimens
• Europe EN: Cylindrical specimens, φ150 × 300 mm, with grades written as C25/30 (the first number represents cylinder strength, while the second represents cube strength)
• United States ACI: Cylindrical specimens, measured in PSI, rather than using a simple C + number designation

For the same concrete mix: cube strength ≈ cylinder strength × 1.25; cylinder strength ≈ cube strength × 0.8.

For example, China’s C30 concrete has a cube strength of 30 MPa, corresponding to an approximate cylinder strength of 24 MPa. It is therefore not equivalent to European C30.

Do not directly equate the numbers: Chinese C40 ≠ European C40.

---

# 2. Concrete Classification Goes Beyond “C” Grades

In addition to conventional concrete, various types of functional concrete are used to meet the requirements of specific projects.

# 2.1 Impermeable Concrete (P Grade)

Grades: P6, P8, P10 (the higher the number, the higher the impermeability level)

Applications: Basements, water tanks, underground passages, and other structures exposed to water.

---

# 2.2 Freeze-Resistant Concrete (F Grade)

Grades: F50, F100, F150 (the number represents the number of freeze-thaw cycles the concrete can withstand)

Applications: Exposed structures in cold northern regions, such as balconies, canopies, and outdoor steps.

---

# 2.3 Pumped Concrete

Good flowability allows concrete to be transported through pipelines to high-rise construction sites.

Key indicator: Slump, measured in mm, which indicates the flowability of fresh concrete.

---

# 2.4 Self-Compacting Concrete

Self-compacting concrete does not require vibration and relies on its own flowability to fill complex formwork and spaces between reinforcement bars.

Applications: Structures with dense reinforcement or areas where conventional vibration is difficult.

---

# 3. How to Choose the Appropriate Concrete Grade

# 3.1 Follow the Design Requirements — Do Not Choose a Higher Grade Without Reason

Strictly follow the concrete grade specified in the design drawings. If C30 meets the project requirements, there is generally no need to use C40, which may result in unnecessary costs and an increased risk of cracking.

---

# 3.2 Consider Environmental Conditions and Project Requirements

• Underground structures: Pay particular attention to the impermeability grade.
• Above-ground structures: Consider freeze-thaw resistance where applicable.
• Special environments: Communicate with the technical team in advance.

---

# 3.3 Proper Curing Is Essential for Achieving the Required Strength

“Three parts pouring, seven parts curing.” Special attention should be paid to thermal insulation and curing measures during winter construction.

---

# 4. How Do Different Concrete Grades Affect the Selection of Release Agents for Precast Concrete Components?

Many overseas customers discussing release agents for pipe piles, concrete segments, composite slabs, and other precast components often mention grades such as C30, C40, and C50. However, we need to emphasize again that Chinese GB concrete grades cannot be directly equated with concrete grades used in Europe, the United States, Southeast Asia, or other local markets. Before production, the differences between concrete grading systems in different countries must be clearly understood.

In addition, to achieve the best possible demolding performance, we do not recommend a release agent or dilution ratio based solely on the concrete strength grade. Based on our experience with numerous applications, we have found that in addition to the concrete grade, we also need to understand the component type (pipe piles, concrete segments, stairs, precast beams, composite slabs, etc.), production process (centrifugal casting or vibration), slump, admixture system, ambient temperature and climate conditions, and even the operator’s application method can be important factors when selecting the appropriate release agent.

---

# 5. Practical Recommendations for Overseas Customers

• Do not directly compare your local concrete grade with China’s C grades or use a simple conversion to select a release agent.
• Provide us with your actual concrete mix, slump, component type, and production process.
• Based on your actual production conditions, we will recommend a suitable product and dilution ratio.

---

# Conclusion

Understanding concrete grades is an important starting point when selecting release agents for precast concrete components. However, the release agent type and dilution ratio should not be determined solely by concrete grades such as C30, C40, or C50. For overseas customers in particular, China’s GB standards differ from the concrete grading, test specimen, and measurement systems used in different countries, so the grades should not simply be equated or directly converted.

In actual release agent selection, it is more important to consider the concrete mix, slump, component type, production process, admixture system, ambient temperature, and application method. For different precast products such as pipe piles, concrete segments, precast beams, and composite slabs, we recommend determining the appropriate release agent and dilution ratio through actual production conditions and testing. This helps ensure reliable demolding and good concrete surface quality while reducing the overall cost of release agent use.