Abstract
There has been a growing interest in polymer applied for soil reinforcement in recent years. However, there little attention has been paid to the effects of polymer on soil cracking behavior, and cracks significantly change soil strength and hydraulic properties and alter reinforcement effectiveness. This study investigated the desiccation cracking behavior of polyurethane (PU) and polyacrylamide (PAM) admixed clayey soils with different polymer concentrations by performing desiccation cracking tests. Scanning electron microscope (SEM) observation was also carried out to obtain the internal structure of these soils. The results show that PU and PAM addition both prolonged the initial evaporation stage, accelerated later evaporation processes, and the effects were related to polymer concentration. Final cracks morphology analyses show that PAM addition slightly reduced the cracking and crushing degree and kept the soil relatively intact, while PU addition slightly enhanced the cracking and crushing degree of soil. In addition, PU and PAM addition both increased the width and length of cracks. The scanning electron microscopy (SEM) analyses show that the effects of polymer on soil evaporation and cracking could be concluded as: (1) storing water in voids, (2) influencing water immigration channel, (3) providing space for soil shrinkage, and (4) enhancing the connection between aggregates, which did not fully come into play because of the existence of hydrogel form. These achievements provide a certain basis for the research of desiccation cracking behavior of polymer treated soil and make significant sense for the safe and effective running of related projects.
Highlights
Polymer has gained increasing attention for soil reinforcement in recent years [1,2,3] because of its excellent characteristics in terms of efficient performance, better sustainability, providing a clean and healthy environment, and ease of operation [4,5,6]
This study investigated the desiccation cracking behavior of two different commonly used polymers admixed with clayey soils
Three different stages of evaporation process could be identified according to the evaporation rate: (1) the constant rate stage, (2) the deceleration rate stage and (3) the residual stage, which was consistent with the results reported by Zhang et al [41] and Tang et al [42]
Summary
Polymer has gained increasing attention for soil reinforcement (i.e., improving soil poor performances such as cohesion and ductility) in recent years [1,2,3] because of its excellent characteristics in terms of efficient performance, better sustainability, providing a clean and healthy environment, and ease of operation [4,5,6]. Many researchers have studied the behaviors of polymer treated soil in the laboratory and concluded that polymer treatment can effectively enhance soil mechanical properties in terms of compressive strength, shear strength, and tensile strength as well as ductility [9,10,11,12], improving soil hydraulic properties in terms of water hold ability, Polymers 2020, 12, 2398; doi:10.3390/polym12102398 www.mdpi.com/journal/polymers. Further examination shows that previous studies mostly investigate the effects of polymer on the mechanical and hydraulic performances of soil. There are few studies on the behavior of desiccation cracking of polymer treated soil [18]
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