Mechanical Properties, Failure Mode, and Microstructure of Soil-Cement Modified with Fly Ash and Polypropylene Fiber

Xue-Lei Duan,Jing-Shuang Zhang

doi:10.1155/2019/9561794

Abstract

In order to investigate the effects of fly ash and polypropylene fiber on mechanical properties, failure mode, and microstructure of soil-cement, the unconfined compression test, splitting tension test, and scanning electron microscopy (SEM) test of soil-cement with different polypropylene fiber contents (0%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% by weight of dry soil) and fly ash contents (0%, 4%, 8%, and 12% by weight of dry soil) were carried out. The compressive and tensile strengths, deformation characteristics, failure mode, and microstructure of soil-cement modified with fly ash and polypropylene fiber were analyzed. The results show that the unconfined compressive strength and splitting tensile strength of soil-cement show a trend of increasing first and then decreasing with the increase of polypropylene fiber and fly ash content. Under the condition of 0.4% polypropylene fiber and 8% fly ash, the unconfined compressive strength and the splitting tensile strength are 4.90 MPa and 0.91 MPa, respectively, which increased by 32.79% and 51.67% as compared with the plain soil-cement, respectively. When 8% fly ash was used in the experiment, the unconfined compressive peak strain and the splitting tensile peak strain of the inclusion of 0.4% polypropylene fiber were 0.0410 and 0.0196, respectively. The corresponding peak strains were increased by 20.94% and 68.97% as compared with non-fiber-stabilized soil-cement, respectively. The stress-strain curve of fly ash soil-cement modified with polypropylene fiber can be divided into compaction phase, linear rise phase, nonlinear rise phase, and failure phase. Polypropylene fiber constrains the lateral deformation of fly ash soil-cement, which improves the peak strain and the failure mode of soil-cement.

Highlights

Soil-cement is a kind of composite material composed of cement, soil, and other components
In order to better describe the influence of polypropylene fiber and fly ash content on the unconfined compressive strength, the strength growth rate η is defined: η σn − σ0 × 100%, σ0 (1)
Under the condition of 0.4% polypropylene fiber inclusion, the maximum of unconfined compressive strength of soil-cement reinforced with 8% fly ash is 4.90 MPa, increasing by 17.22% as compared with that of soil-cement without fly ash inclusion. e effect of fiber on unconfined compressive strength might be due to the following reasons: (i) e root of the fiber is wrapped with the gel material that is the hydration reaction product of the cement, which forms an anchoring effect on the fiber

Summary

Introduction

Soil-cement is a kind of composite material composed of cement, soil, and other components. Park [22] studied the effect of the polyvinyl alcohol fiber on cemented sand and found that 2% polyvinyl alcohol fiber could improve the compressive strength of 2.5 times as compared with non-fiber-stabilized cemented soil In these fibers, polypropylene fiber that can enhance the soil strength and reduce the shrinkage is widely used. E primary objective of this paper is to explore the effects of polypropylene fiber and fly ash content on unconfined compressive strength, splitting tensile strength, deformation characteristics, failure mode, and microstructure of soil-cement. To achieve this purpose, a series of unconfined compression test, splitting tension test, and SEM test were carried out

Experiment Materials and Sample Preparation

Experimental Results

Deformation and Failure Mode

Analysis of SEM Images of Specimens

Conclusions