GCP Scientists Contribute to Better Understanding of Deep Mining

The build-up thickness of a mix containing TYTRO® RC 430. "It's important to have a mix that is viscous, cohesive and sticky enough for high build-up thickness, which is highly desirable", said GCP scientist Ezgi Yurdakul.

The Eighth International Conference on Deep and High Stress Mining, in Perth, Australia this March, will aim to better understand significant geotechnical and logistical issues of deep and high-stress mining.

Host Australian Centre for Geomechanics has selected GCP Applied Technologies' paper, "Role of chemical admixtures in improving wet-mix shotcrete performance for ground support", as contribution to this more comprehensive understanding of the challenging construction environment.

In the study, GCP scientists tested performance of liquid admixtures against silica fume powder. They conducted field experiments during a major ground support operation where the project was susceptible to an alkali-silica reaction (ASR) risk. The applied admixture—a pozzolonic-based rheology control agent—had to reduce risk of ASR, increase early-age strength, enhance sprayability and pumpability of the shotcrete and meet required later-age strength, toughness and durability.

Results reflected that the customised mix design for the proposed system—25% fly ash and 0.8% rheology control agent admixture—more than met job requirements.

Sprayability vs. Pumpability

Key components of quality shotcrete are pumpability and sprayability, which are typically at odds with each other. Pumpability, which is a mix's stability and mobility under pressure, tends to rate better with high slump. High slump, however, does not bode well for a mix's adhesion (stickiness to the surface) and cohesion (stickiness to itself). In contrast to pumpability, good sprayability excels when the mix is highly viscous, a "sticky mix", with low slump.

To satisfy the conflicting sprayability/pumpability requirements in the shotcrete, GCP has designed TYTRO® RC 430, a rheology control agent, to draw a delicate balance between rheological characteristics. The TYTRO® RC 430 maintains the highest possible fluidity, while providing desired viscosity, cohesiveness and "stickiness".

Download the scientific paper to learn how GCP's rheology control can accelerate early strength for build-up, reduce rebound rate, increase pumpability and maintain high later-age strength of shotcrete…

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