DURABILITY OF CLAYEY SOIL STABILIZED WITH CALCIUM SULFOALUMINATE CEMENT AND POLYPROPYLENE FIBER UNDER EXTREME ENVIRONMENT

Author

Saroj Dhakal, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2022

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Kolay, Prabir

Abstract

Calcium Sulfo-Aluminate (CSA) Cement is gaining interest among scholars, consultants, engineers, and environmentalists as a prospective replacement of Ordinary Portland Cement (OPC) across many construction industries. The main reason is the production of CSA cement generates a lower carbon footprint as compared to OPC cement production. Other benefits of CSA cement include quick bonding & strength development, and less shrinkage. Many studies are available and ongoing on the advantages and limitations of CSA cement in concrete. However, there are only a few studies available on its application in soil stabilization. Therefore, the efficiency of CSA cement for soil stabilization is a topic of discussion in the geotechnical sector. In this research, a locally sourced clayey soil is stabilized using different percentages of CSA cement and polypropylene fiber, and its effectiveness is observed and calculated in terms of durability and strength as per American Society of Testing and Materials (ASTM) guidelines. The soil samples for this research were stabilized with three different percentages of CSA cement, which includes 5.0%, 7.5%, and 10.0%, along with two different percentages of fiber, i.e., 0.5% and 1.0%. Soil without CSA cement and polypropylene fiber was also studied as a baseline.Extreme environments including freezing temperature, humidity, intense heat, and wetness have a detrimental effect on stabilized soil and those effect must be controlled for all construction. The effect of CSA cement with fiber was studied in this research under such environmental impacts using ASTM standard tests, i.e., 12 cycles of the Freezing-Thawing test and 12 cycles of the Wetting-Drying test. Twelve cycles of freezing-thawing tests imitate alternate temperature variations in very cold weather with alternate -200C to -250C and room temperature ranging from 200C to 250C with high relative humidity. On the other hand, twelve cycles of wetting-drying tests simulate alternate weather in very hot weather with frequent heavy rainfall. The findings of this research are evaluated in terms of percentage of soil loss, change in moisture content and volume, and loss of Unconfined Compressive Strength (UCS) of samples that survived 12 cycles of durability test according to the Portland Cement Association's (PCA) durability criteria. Moisture content and bulk unit weight were calculated after each stage in the Freezing-Thawing durability cycles. Soil loss was calculated after each cycle in Wetting–Drying durability test. Samples prepared with 10.0% of cement with 1.0% of fiber were able to survive all durability cycles of Wetting-Drying with soil-loss percentage criteria. On the other hand, samples prepared with 10.0% cement with 0.5% as well as 1.0% fiber were able to survive all durability cycles of Freezing-Thawing as well as soil-loss percentage criteria. These survived samples were tested for their UCS value to study the change in their strength before and after stabilization as well as after surviving all durability cycles. The result of the stabilized soil demonstrates significant improvement of strength even after surviving both cyclic durability test. This research found that development of ecofriendly CSA cement with propylene fiber is a promising alternative to OPC cement for durable clayey soil stabilization in very harsh environmental conditions.