Influences of Fibers on Expansive Shotcrete Mixture Consisting of Calcium Sulfoaluminate, Portland Cement, and Calcium Sulfate Open Access
- Other title
calcium sulfoaluminate cement (CSA)
calcium sulfate (CS)
- Type of item
- Degree grantor
University of Alberta
- Author or creator
- Supervisor and department
Liu, Wei V. (Mining Engineering)
- Examining committee member and department
Li, Yong (Structural Engineering)
Pourrahimian, Yashar (Mining Engineering)
Liu, Wei V. (Mining Engineering)
Department of Civil and Environmental Engineering
- Date accepted
- Graduation date
Master of Science
- Degree level
Shotcrete is often used by the mining industry as rock support, tunnel lining, and concrete repair. However, cracking within shotcrete is common, which delays production schedules and increases maintenance costs. To reduce cracking, expansive shotcrete mixtures are often used. While several commercial expansive cements / shotcrete mixtures are available, the ingredients of these products are usually confidential. To optimize the effects and usages of expansive shotcrete mixture, mixture with known compositions should be studied. Possible expansive shotcrete mixtures can be developed by combining calcium sulfoaluminate cement (CSA), ordinary Portland cement (OPC), and calcium sulfate (CS) in the binder. Furthermore, fibers can be added to the mixture to restrain expansion and impede cracking. The objective of this thesis is to identify expansive shotcrete mixtures consisting of CSA, OPC, and CS, and study the effects of nylon fiber, glass fiber, and steel fiber on the identified mixture so that better crack resistance can be achieved. In this study, parameters such as density, water absorption, volume of permeable voids, unconfined compressive strength (UCS), splitting tensile strength (STS), and volume change of the mixtures were determined at different time periods (i.e., the mechanical strengths on the 28th day, and the volume changes on the 1st, 7th, 14th, 21st, and 28th days). Five expansive shotcrete mixtures, along with five strength-enhanced mixtures, that contained CSA, OPC, and CS in the binder were identified. The expansive mixture showing enhanced UCS (mixture with 40%CSA+20%OPC+40%CS) was selected for fiber additions in this study. Results have presented that the addition of fibers improved mixture durability, in the form of decreased water absorption and reduced permeable pore space content. Moreover, the expansion of the CSA-OPC-CS mixture was controlled by fiber reinforcement. Glass fiber restrained up to 50% of the expansion, while nylon fiber restrained up to 43% and steel fiber restrained up to 28% of the expansion. The results showed that STS was improved by 57% with glass fiber addition, 43% with steel fiber addition, and 38% with nylon fiber addition. The UCS also increased at a percentage of 31% after steel fiber addition, 26% after nylon fiber addition, and 16% after glass fiber addition. Based on the results, it is concluded that fiber additions to expansive shotcrete mixtures improve durability and mechanical strengths, while controlling expansion. The results in this thesis provide alternative options of expansive and strength-enhanced shotcrete mixtures consisting of CSA, OPC, CS, and fibers. These options could better mitigate the cracking in shotcrete, thereby reducing the costs on repair and replacement.
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
- Citation for previous publication
H. Yu, L. Wu, W.V. Liu, and Y. Pourrahimian. (2017). Developing Expansive Shotcrete Mixtures from Calcium Sulfoaluminate, Portland Cement, and Calcium Sulfate. CIM 2017 Convention in Montreal, Canada.H. Yu, L. Wu, W.V. Liu, and Y. Pourrahimian. (2017) Influence of fibers on expansive shotcrete mixtures consisting of calcium sulfoaluminate, Portland cement, and calcium sulfate. Submitted to Journal of Rock Mechanics and Geotechnical Engineering (under review).
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