Moisture control of the bunker sand is more than just drainage. Moisture control is the ability to freely drain rain events and to be able to keep moisture in the bunker sand in dry conditions.
Avondale Golf Club in Sydney, Australia. Moisture applied through Capillary Concrete™ on steep faces in dry conditions.
10 min after start cycle.
The ability to move water against the force of gravity – Capillary Action!
Above, you can see the result of moisture being fed to the Capillary Concrete™ and how it has started to moisturize this steep bunker face. The Capillary Concrete™ system utilizes capillary action to moisturise the bunker sand from below. This is done through the special Capillary Concrete™ technology with polymers that create microscopic connections in the actual binding agent of the Capillary Concrete™.
Capillary Concrete™ testing shows how moisture moves in a dry sample (left) placed in moisture, to being saturated after 3 days (middle) and the sand sticking to the vertical face (right). The sand stays on the Capillary Concrete™ due to the capillary connection of moisture between the liner and the sand. This is the Patent P Capillary Concrete™ system.
What is capillary breach / connection?
Capillary breach occurs when the pore sizes of two materials do not match, and moisture will then not be able to move against gravity, upwards in the profile. Capillary breach is used in a USGA – green to stop irrigation from exiting into the drainage system until the profile is filled up. Water will not move from a small hole to a large hole until gravity is strong enough to pull it down.
In a green, capillary breach is a good thing if there is 300 mm of sand. In bunkers, we want to avoid a capillary breach as it only results in sand shifting and sliding down the face of the bunker. It results in sand having different moisture levels within each bunker which result in different playing conditions and higher maintenance costs.
Capillary Concrete™ contains large pores that freely drain water by force of gravity, but not too large in order to avoid migration of sand particles into the drainage system. If the large pores are too big, the sand will eventually clog the drainage system.
When does migration occur in bunker sands? – If you let the bunker sand dry out, which can easily happen if the liner is not capillary connected to the soil, sand will migrate down through the drainage system even if the pore sizes match a USGA- greens requirement. This is because dry sand more easily can penetrate and move, and dry bunker sand gets shifted around and worked in to the drainage system.
Moist sand stays in place and does not migrate if the pore sizes are kept within the requirements.
The key is to make sure the sand stays moist at all times, to avoid capillary breach
Take a look at the Legendary Superintendent Jacques Leonard testing Capillary Concrete™.