Ingredients and Proportions:
Dry Ingredients: The main components of gunite mix are Portland cement, sand, and sometimes additional aggregates or admixtures. The specific proportions of these ingredients may vary depending on the project's requirements and mix design.
Mix Design: A mix design is created based on the project's specifications, including the desired compressive strength, workability, and other performance criteria. The mix design specifies the proportions of each ingredient to achieve the desired concrete properties.
Mixing Process:
Batching: The dry ingredients are accurately batched and measured according to the mix design. This typically occurs at a concrete batch plant or a designated mixing area on the construction site.
Transport: Once the dry ingredients are batched, they are transported to the construction site in bulk containers, such as silos or bulk bags. These containers protect the dry mix from moisture and environmental factors.
Mixing at the Site: At the construction site, the dry mix is typically transferred to a holding hopper or container on the gunite machine.
Addition of Water: Water is added to the dry mix just before it enters the gunite machine. The addition of water is carefully controlled to achieve the desired mix consistency and workability. The water and dry mix are usually combined in the hopper or feed system of the gunite machine.
Gunite Application:
Spraying: Once the dry mix is combined with water and reaches the gunite machine, it is pneumatically conveyed through a hose and nozzle. Compressed air is used to propel the wet mix onto the target surface at high velocity. The nozzle operator controls the application thickness and pattern.
Application and Shaping: As the wet mix is sprayed onto the surface, workers use hand tools or shaping equipment to mold and shape the gunite to conform to the desired structural or architectural specifications.
Curing: After application, the gunite is cured to develop its strength and durability. Proper curing methods, such as moisture curing or curing compounds, are used to prevent the loss of water from the material.
It's essential to follow the mix design and batching procedures precisely to ensure that the gunite mix meets the project's requirements for strength and workability. The controlled addition of water just before application is a critical step in the process, as it allows for the adjustment of the mix's consistency and ensures that it adheres well to the target surface. Additionally, safety measures should be in place during the application process, as gunite application involves the use of high-pressure equipment.
