Sika SA’s Concrete business unit is venturing into the tunnelling and mining sector. Sika is celebrated worldwide for its innovative and technologically advanced products for the tunnelling and mining sector, and Sika SA will benefit from this longstanding expertise and reliability. Andre Erasmus has recently joined Sika SA as Tunnelling and Mining Manager to grow this market field on behalf of Sika.

Thembelani 2 Shaft – Rustenberg, North West Province, South Africa

Sika commenced the supply of construction products to the Thembalani Mine in August 2011. Thembelani Mine forms part of the Western Limb of the Bushveld Igneous Complex, owned by Anglo Platinum. The mine operates under a mining right covering a total area of 31sq km.

The Thembelani No 2 ventilation shaft project is currently under execution to access the deeper Merensky ore body. The predominant mining layout is conventional scattered breast mining with strike pillars, and the operating depth for the current workings is between 400m and 1000m below surface.

Sika’s following four products are ongoing supplies to the project:

ViscoCrete 3088: This 3rd generation PCE superplasticiser developed by Sika has the advantage of offering very high water reduction - 12-20% WR - as well as keeping the concrete workable for up to two hours. On this mine the concrete is gravity fed down a 1km pipeline, therefore this wet shotcrete mix must remain fluid but still cohesive in nature. The ViscoCrete 3088 helps to create this fluid yet cohesive concrete.

SikaTard 930: This stabilizing agent is able to "put the concrete to sleep"! It is capable of enabling the concrete to remain workable for up to three days if required. The shotcrete contractor needed the concrete to stay workable for six to ten hours. It was important that the concrete never lost workability due to the gravity-fed 1 km pipeline delivery system, and once delivered to the mineshaft, it could be up to three hours before the wet shotcrete was finally sprayed.

Sigunit L 53 AF: This liquid, alkali-free, high performance shotcrete accelerator greatly improves early strength development without a major loss in final strength that is associated with other shotcrete accelerators (such as the older Alkali containing accelerator types). Sigunit L53AF significantly reduces the rebound associated with sprayed shotcrete. On the mine project, the Sigunit L53AF was used for the same reasons listed above for wet shotcrete - immediately accelerating the concrete "out of the deep sleep'' induced by the SikaTard 930. This hydration reaction instantly increases early strength development and reduces the rebound.

Sigunit P 10 AF: This powder, alkali-free, high performance shotcrete accelerator can be used for both dry and wet shotcrete applications. Sigunit P10AF significantly reduces the rebound associated with dry sprayed shotcrete. On the mine the shotcrete was applied using the dry shotcrete application method. The Sigunit P10AF immediately accelerates the hydration reaction, increasing early strength development and reducing the very high rebound associated with the dry shotcrete application method.

One of the challenges on site was the complete conversion from Dry Shotcrete to Wet Shotcrete batching on surface. "Dry Shotcrete" is the process of mixing all the materials (sand, cement, fibres) dry and then feeding it into a shotcrete machine adding water at the spray nozzle before applying the concrete onto the side walls of the tunnels. With "Wet Shotcrete" the concrete is mixed before it is fed into the shotcrete machine.”

Sika is committed to the global chemical industry environmental management systems, Responsible Care, which defines the principles for safety, health and environmental protection. Sika’s Shotcrete requirements ensure that ecology, economy, quality and performance are considered in order to provide the most beneficial solutions for the customer.

Sika’s Experience in Tunnelling for over 100 Years

As early as 1910, when the electrification of the railways began, the importance of tunnel waterproofing was recognised. Today the waterproofing of underground traffic structures is required as a matter of course by specialists. With its quick-setting mortar, Sika not only provided the first lead in the tunnel-waterproofing epoch, but was involved most influentially to the present day in the development of new technologies.

A few of Sika’s international tunnelling and mining references are:

Gotthard Railway Tunnel; - Rail under the Swiss Alps

Hafnerberg Tunnel; - Road tunnel near Zurich, Switzerland

Tunnel Engelberg; - Motorway tunnel near Stuttgart, Germany

Felber Tauern Tunnel - Goods railway tunnel in Austria

Uietilberg Motorway Tunnel - Motorway tunnel around Zurich, Switzerland