Study of Effective Experimental Approaches to Improve Hempcrete's Compressive Strength
Open Access
- Author:
- Asghari Bareh Kheil, Nima
- Graduate Program:
- Architectural Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- April 29, 2024
- Committee Members:
- Ali M Memari, Thesis Advisor/Co-Advisor
Corey Gracie-Griffin, Committee Member
James Freihaut, Program Head/Chair
Esther Adhiambo Obonyo, Committee Member
Hojae Yi, Committee Member - Keywords:
- hempcrete
sustainable material
magnesium oxide
fly ash
metakaolin
nano-silica
compaction
mechanical properties.
nano silica
mechanical properties - Abstract:
- This research explores the enhancement of hempcrete's compressive strength to establish it as a viable, sustainable alternative to traditional concrete in the construction industry. Hempcrete, a composite material made from hemp hurds, water, and lime-based binders, offers a promising solution to reduce the environmental impact of construction activities. However, its low compressive strength compared to conventional concrete hinders its widespread application in load-bearing structures. The primary objective of this study was to investigate various strategies to improve the compressive strength of hempcrete, including the use of alternative binders like magnesium oxide (MgO), the incorporation of additives such as metakaolin, fly ash, and nanosilica, and the optimization of mixture proportions. The research also examined the impact of sand as a fine aggregate on the mechanical properties of hempcrete. The experimental program involved preparation and testing of three distinct mixture designs, each comprising different combinations of binders, hemp hurds, water, and additives. Mixture Design 1 focused on hydrated lime as the primary binder, while Mixture Design 2 explored the use of MgO. Mixture Design 3 built upon the findings of the first two designs, incorporating sand as an additional component to enhance compressive strength. Hempcrete specimens were prepared in 2x2 inch cubes, following a standardized mixing, molding, and curing process. The specimens were cured for 7 days under controlled conditions of 100% relative humidity and 23°C temperature. Compressive strength tests were conducted using an MTS testing apparatus, adhering to ASTM C-109 guidelines. The results demonstrated a significant improvement in the compressive strength of hempcrete, with values ranging from 58 psi to 655 psi, depending on the mixture design. The use of MgO as a binder, coupled with the incorporation of additives and sand, led to the most substantial enhancements in compressive strength. Notably, specimen 2LS60 from Mixture Design 3, containing 45% MgO, 5% hemp, 60% sand, and 4% nanosilica, achieved the highest compressive strength of 655 psi, representing a 2,126% increase compared to the original hempcrete specimen without additives or sand (29 psi). The analysis of the results revealed that increasing the binder content, particularly MgO, and reducing the hemp hurd content contributed to improved compressive strength. The synergistic effects of pozzolanic additives, such as metakaolin and fly ash, and the inclusion of sand as a fine aggregate further enhanced the mechanical properties of hempcrete. In conclusion, this study successfully demonstrated the potential for significantly enhancing the compressive strength of hempcrete through the optimization of mixture proportions, the use of alternative binders, and the incorporation of additives and sand. The findings pave the way for the development of high-performance hempcrete mixtures suitable for load-bearing applications in the construction industry. By achieving compressive strength values comparable to conventional concrete, this research contributes to the growing body of knowledge on sustainable construction materials and supports the adoption of hempcrete as an eco-friendly alternative to traditional concrete.