Search

ABSTRACT Hydrogel has been widely used in medical studies due to their unique integration of solid and liquid properties. There is limited studies of using hydrogel in construction materials. The [...]

ABSTRACT Microbial induced calcite precipitation (MICP) can bond sand particles together to improve the mechanical properties of sandy soil. This environmental-friendly technique has potential applications on construction materials such as [...]

This study aimed to use hydrogel to stabilize expansive clayey soil. The effect of sodium alginate content on mechanical behaviors, swelling, and durability of hydrogel-impregnated clayey soil were investigated through unconfined compression tests, consolidated and undrained triaxial tests, free swelling tests, and durability tests. The tests results indicated that the sodium alginate added in the clay soil had a positive effect on the residual strength of the soil samples. The Ca-alginate hydrogel produced in the soil samples improved their ductility significantly. The swelling deformation of clay soil decreased along with higher sodium alginate content. The results showed that the swelling deformation decreased from 0.8 mm to 0.5 mm when 0.4% sodium alginate was added in the clay soil which was nearly 37.5% reduction. The connection between clay soil particles was improved by the gelation connection provided by hydrogel the friction of soil was also enhanced a lot. For wet–dry and freeze–thaw cycles, 60% and 80% of the original unconfined compression strength of hydrogel-impregnated clay remained after 12 cycles. It can be concluded that the Ca-alginate hydrogel has a good durability performance against wet–dry and freeze–thaw cycles.

The use of biopolymers to tackle geotechnical problems is an essential step toward the development of sustainable geotechnical systems. The strength and erosion resistance of biopolymer-treated Hot Coffee soil sampled from the bridge site in Jackson, Mississippi were examined in this research. The optimum biopolymer concentration and moisture content were tested for Agar Gum, Xanthan Gum, and Guar Gum treatment of Hot Coffee soil, respectively. The mechanical behavior and erosion resistance of biopolymer-treated soil samples were evaluated through the unconfined compressive strength test, splitting tensile test, triaxial test, and pocket erodometer test. The results indicated that all three biopolymers improved Hot Coffee soil strength, but Guar Gum improved soil unconfined compressive and tensile strength greatly. The addition of 1% Guar Gum can improve the unconfined compression stress (UCS) and split the tensile strength of Hot Coffee soil to roughly 4,000 kPa and 600 kPa, respectively. At the same time, the cohesion of Hot Coffee soil treated with biopolymer was enhanced. The cohesion of the soil treated with 1.5% Xanthan Gum increased from 0 to 41.5 kPa. In addition, the erosion resistance of biopolymer-treated soil was also increased. With a 1.5% Xanthan Gum addition, the erosion resistance level of Hot Coffee soil reduced from very high erodibility to medium erodibility. Therefore, biopolymers have great potential for bridge scour mitigation.

As a new environmentally friendly and sustainable technique for soil improvement, microbial-induced calcite precipitation (MICP) has been studied widely. A suitable sample preparation mold is the first step to prepare MICP treatment. The purpose of this study is to develop a rigid full-contact mold to prepare larger biobeam specimens for MICP treatments with an immersing method. Four different molds were developed, including a plastic beam rigid mold without a cover, a full-contact flexible mold, a rigid full-contact mold with geotextiles, and a rigid full-contact mold with filter paper. Beam-shaped specimens with different dimensions were treated with the four molds in the MICP process. A four-point bending test and a split tensile strength test were conducted to evaluate the flexural behavior of MICP-treated specimens from the four sample preparation molds. The results indicated that an MICP-treated sample prepared by the rigid full-contact mold with geotextiles can form the best beam shape and the most uniform calcite precipitation inside the sample. Additionally, the biobeam made by the rigid full-contact mold with geotextiles achieved the best mechanical properties. The flexural strength of the biobeam made by the rigid full-contact mold was 1,125 kPa at a failure flexural strain of 1.5 %, and the split tensile strength was 368 kPa with a failure tensile strain of 1.8 %.