Expansive Mortar

Expansive mortar, also known as expansive cement or non-explosive demolition agent, is a powdered material that, when mixed with water, undergoes an expansive reaction.

Definition:

Expansive mortar, also known as expansive cement or non-explosive demolition agent, is a powdered material that, when mixed with water, undergoes an expansive reaction. It generates controlled pressure and expansive forces, resulting in the cracking and splitting of rock, concrete, or other solid materials. Expansive mortar is commonly used in tunneling and underground structures for rock excavation, controlled demolition, and breaking of hard materials.

Uses/benefits:

Rock excavation: Expansive mortar is widely used in tunneling and underground construction for rock excavation. It is an alternative method to traditional mechanical drilling and blasting techniques. The expansive forces created by the mortar help break and fracture the rock, facilitating excavation.
Controlled demolition: Expansive mortar is employed in controlled demolition applications, particularly for removing concrete structures or rock formations. It allows for precise and controlled breaking of the material, minimizing vibration, noise, and dust generation.
Non-explosive nature: Unlike traditional explosives, expansive mortar is non-explosive and does not produce shockwaves or fly rock during the cracking process. This makes it a safer and more environmentally friendly option, especially in sensitive areas or urban environments.
Minimal damage to surrounding structures: Expansive mortar exerts pressure primarily in the desired direction, minimizing the risk of damage to nearby structures or sensitive elements during rock excavation or demolition activities.
Easy application: Expansive mortar is easy to mix and apply. It can be prepared on-site by mixing with water and poured into pre-drilled holes or placed in strategic locations for controlled cracking and breaking.
Reduced noise and vibration: The controlled cracking process achieved with expansive mortar results in reduced noise and vibration compared to traditional drilling and blasting methods. This is particularly advantageous in urban areas where noise and vibration restrictions may apply.

Specifications:

Expansive force: The expansive force generated by the mortar is an important specification. It determines the cracking capability and the size of the rock or concrete sections that can be effectively broken. The seven days expansion is in the range of 0.04% -0.10 %.
Setting time: The setting time of the expansive mortar refers to the time it takes for the material to expand and crack the rock or concrete. Different types of expansive mortars have varying setting times, allowing for flexibility in project scheduling. Setting time for expansive cement is to be around 75 min.
Temperature resistance: The performance of expansive mortar under different temperature conditions is a consideration. Some types of expansive mortars are formulated to withstand high temperatures, allowing for their use in challenging environments.
Compatibility: Expansive mortar should be compatible with the materials being fractured, such as rock or concrete. Compatibility ensures effective cracking and breaking without causing excessive damage or compromising the structural integrity of surrounding elements.

Types:

Calcium-based expansive mortar: This type of expansive mortar is composed of calcium oxide (lime) and an expanding agent such as aluminum powder. It is widely used for rock excavation and controlled demolition in tunneling and underground structures.
Magnesium-based expansive mortar: Magnesium-based mortars offer similar cracking capabilities to calcium-based mortars but with the added advantage of being less affected by temperature variations. They are suitable for use in both hot and cold environments.
Silicate-based expansive mortar: Silicate-based mortars utilize alkali silicates as the main ingredient. They provide excellent crack formation in concrete structures and are often used in controlled demolition or renovation projects.

Expansive mortar offers an efficient and controlled method for rock excavation and controlled demolition in tunneling and underground structures. Its use provides benefits such as safety, reduced environmental impact, and precise cracking capabilities. By selecting the appropriate type and considering specific specifications, expansive mortar can be tailored to meet the requirements of different projects.