Wet-mix shotcrete and dry-mix shotcrete are two different methods of applying shotcrete, which is a type of concrete that is sprayed onto a surface using compressed air. The main differences between the two methods lie in the preparation of the concrete mix and the equipment used.

　　Wet-Mix Shotcrete

　　- Mix Preparation: In wet-mix shotcrete, the concrete mix is prepared with all the ingredients (cement, aggregates, water, and additives) thoroughly mixed together before being pumped to the nozzle.

　　- Equipment: Wet-mix shotcrete requires a wet-mix shotcrete machine, which pumps the pre-mixed concrete to the nozzle.

　　- Advantages:

　　- Lower dust emissions compared to dry-mix shotcrete.

　　- More consistent mix quality, leading to higher strength and durability.

　　- Less rebound, which means less waste of materials.

　　- Disadvantages:

　　- More complex equipment, which may require more maintenance.

　　- Higher initial cost due to the need for a more sophisticated pumping system.

　　Dry-Mix Shotcrete

　　- Mix Preparation: In dry-mix shotcrete, the dry ingredients (cement, aggregates, and additives) are mixed together and then conveyed to the nozzle, where water is added at the last moment.

　　- Equipment: Dry-mix shotcrete uses a dry-mix shotcrete machine, which blows the dry mix to the nozzle, where water is injected.

　　- Advantages:

　　- Simpler equipment, which is easier to operate and maintain.

　　- Greater flexibility in terms of mix design and application.

　　- Can be used in more remote locations where access to water is limited.

　　- Disadvantages:

　　- Higher dust emissions, which can be a health hazard.

　　- More difficult to control the mix quality, leading to potential variations in strength and durability.

　　- Higher rebound, which results in more waste of materials.

　　In summary, the choice between wet-mix and dry-mix shotcrete depends on the specific requirements of the project, including the desired quality of the finished product, the environmental conditions, and the available resources. Wet-mix shotcrete is generally preferred for projects where high strength and durability are required, while dry-mix shotcrete may be more suitable for projects where simplicity and flexibility are more important.