In this article, we will explore expansive cement, a unique type of cement that exhibits a tendency to increase in volume to a much greater extent than Portland cement paste when mixed with water and allowed to set. The resulting cement mortar or concrete displays an expansion that can compensate for any shrinkage losses.
One of the key features of expansive cement is its ability to expand after setting, allowing it to effectively fill gaps and cracks that would otherwise compromise the structural integrity of concrete. This type of cement is manufactured using a combination of materials, such as calcium sulfate and anhydrous tetracalcium trialuminate sulfate, that produce the expansive properties.
There are several types of expansive cement available, each with different characteristics and applications. Some of the most common types include Type K, Type M, and Type S. Type K is used for massive concrete structures, while Type M is suitable for bridge decks and pavements. Type S, on the other hand, is ideal for precast concrete elements.
Expansive cement finds a variety of uses in construction, including in the production of precast concrete elements, bridge decks, pavements, and other types of structures that require high-strength and durability. This type of cement is also useful in repairing cracks and joints in concrete, as well as in creating watertight seals in concrete structures.
In summary, expansive cement is a unique type of cement that exhibits significant expansion after setting, making it ideal for filling gaps and cracks in concrete structures. It is manufactured using a combination of materials and comes in different types, each with specific characteristics and applications. Expansive cement finds widespread use in the construction industry for creating durable, high-strength structures that can withstand the stresses of everyday use.
Manufacture of Expansive Cement
The manufacturing process of expansive cement is similar to that of Portland cement, but the raw materials used for forming clinkers differ. In the production of this type of cement, limestone and clay are initially heated together at a temperature of approximately 2,600 degrees Fahrenheit, resulting in the formation of clinkers. In the following batch, a mixture of limestone, calcium sulphate, and bauxite is heated together at around 2,300 degrees Fahrenheit, which produces sulfoaluminate clinkers.
After the formation of both clinkers, they are ground together to create expansive cement. When this cement is mixed or exposed to water, the sulfoaluminate clinkers inside the cement expand in volume. The expansion of the sulfoaluminate is what gives this type of cement its unique properties.
Expansive cement is frequently used in construction where there is a requirement for reduced shrinkage or low permeability. The use of expansive cement can also help to prevent cracking in concrete structures.
Fig 1: Use of expansive cement mortar in grouting of anchor bolts.
Physical properties of Expansive Cement
Table 1: Properties of expansive cement
| Properties | Value |
| Setting Time | 75 min |
| Air Conctent | 12 % |
| 7 Days expansion | |
| Min | 0.04 % |
| Max | 0.10 % |
| Compressive Strength | |
| 7 Days | 14.7 Mpa |
| 28 Days | 24.5 MPa |
Types of Expansive Cement
Expansive cement is a type of cement that expands slightly during the setting process. This expansion is caused by the use of expansive compounds that are added to the cement mixture. Depending on the type of expansive compound used, expansive cement can be divided into three different types.
The first type of expansive cement is based on calcium sulfate. This type of cement is known as calcium sulfate-expansive cement, or simply CSE cement. CSE cement is commonly used in construction projects where the prevention of cracking is important. It is particularly useful in applications where concrete is poured into confined spaces and where shrinkage during setting could lead to cracking.
The second type of expansive cement is based on calcium aluminate. This type of cement is known as calcium aluminate-expansive cement, or CAE cement. CAE cement is commonly used in construction projects where high early strength is required, such as in precast concrete products. It is also used in applications where the prevention of cracking is important, such as in bridge decks and other infrastructure projects.
The third type of expansive cement is based on calcium sulfoaluminate. This type of cement is known as calcium sulfoaluminate-expansive cement, or CSA cement. CSA cement is commonly used in construction projects where rapid setting is required, such as in road repairs and other infrastructure projects. It is also used in applications where high early strength is required, such as in precast concrete products.
1. K Type expansive cement
Expansive cement is produced using a combination of raw materials that include Portland cement, anhydrous tetracalcium trialuminate sulfate (C4A3S), calcium sulfate (CaSO4), and lime (CaO). The process involves grinding these materials to form a specialized type of cement. The resulting cement has unique properties that make it ideal for certain construction applications.
Portland cement is a key ingredient in the production of expansive cement. It provides the basic binding agent that holds the other ingredients together. Anhydrous tetracalcium trialuminate sulfate (C4A3S) is another important component that contributes to the strength and durability of the final product. Calcium sulfate (CaSO4) and lime (CaO) are also added to the mixture to enhance the properties of the cement.
The grinding process plays a critical role in the production of expansive cement. The raw materials are ground to a fine powder, and the resulting mixture is then subjected to a controlled heating and cooling process. This process is designed to activate the chemical reactions between the different components and ensure that the cement has the desired properties.
Overall, expansive cement is a specialized type of cement that is produced using a unique combination of raw materials and a carefully controlled manufacturing process. The resulting product has a range of desirable properties that make it ideal for specific construction applications.
2. M Type expansive cement
Portland cement clinkers undergo a grinding process with calcium sulfate. This process involves reducing the clinkers into smaller particles, which are then mixed with calcium sulfate to produce Portland cement. The grinding process is a crucial step in the production of Portland cement, as it ensures that the clinkers are finely ground to achieve the desired consistency and quality. Calcium sulfate, also known as gypsum, is added to the clinkers to regulate the setting time of the cement and prevent the formation of flash setting, which can occur when the cement sets too quickly. Overall, the grinding process with calcium sulfate is an essential part of the manufacturing process of Portland cement, allowing for the production of high-quality cement that can be used in a wide range of construction applications.
3. S Type expansive cement
This paragraph describes a specific type of expansive cement that has a higher content of tricalcium aluminate (C3A) than regular Portland cement. Additionally, this type of cement contains more calcium sulfate than what is typically found in Portland cement. The increased levels of these compounds contribute to the expansion properties of the cement.
Uses of Expansive Cement
This type of cement is ideal for large floor slabs that require a continuous surface without joints. It is also highly effective for filling holes in foundations and producing self-stressed concrete that is stronger than traditional Portland cement concrete. Additionally, pre-stressed concrete components for bridges and buildings can be constructed using this material. It is commonly used in the construction of water retaining structures and for repairing damaged concrete surfaces. Another application of this cement is in the grouting of anchor bolts.