A new biopolymeric construction material for soil treatment/improvement is introduced in this study in an effort to develop an environmentally-friendly construction engineering approach to replace the use of conventional materials that have high environmental impact. Thermo-gelation biopolymers dissolve and form a suspension in heated (i.e., 85-90 degrees C) water, and then coagulate (i.e., gelate) upon a decrease of temperature (i.e., below 50 degrees C). Gellan gum and agar gum are typical thermo-gelation biopolymers with potential as soil strengthening construction materials due to their hydrogen bonding characteristics, and were used to treat two types (i.e., clayey and sandy) of soil in different quantities and treatment conditions. The results showed that thermal treatment is an important prerequisite as well as air-drying (i.e., hardening), and produced higher strengthening (up to 12 MPa) and durability in an immersed condition. Moreover, gellan gum is preferable to agar gum for soils with significant fine contents due to the interaction (e.g., hydrogen bonding) between biopolymers and fine particles, which produces firm biopolymer-soil matrices. Consequently, thermo-gelation biopolymers have strong potential application as construction materials for both land (i.e., dry) and waterfront purposes.