Preparations of Lake Sediment Geopolymers Using the Alkaline Activation and Their Mechanical Properties

Abstract Lake sediments are chemical precipitates rich in silicon and aluminum and cannot be directly used because of poor mechanical properties. The alkali activation of silicon and aluminum-containing raw materials is a new type of inorganic cementitious strategy for geopolymers that can exhibit an excellent performance and lower carbon emissions with respect to ordinary cement. In this work, we employed the alkali activation to prepare a novel geopolymer from lake sediments in order to solve the problem of lake sediment disposals. To this end, raw materials were obtained using different alkaline activators for unconfined compressive strengths. In particular, the effects of water to solid ratio, dosage of alkaline activator, dosage of silica fume, and fly ash on alkali activation of lake sediments were investigated using the orthogonal experiments. The results showed that plant ash helped solidify the lake sediment but also led to cracks. Sodium silicate was the most appropriate alkaline activator for the lake sediments. Among all the factors, water-solid ratio showed the greatest influence on the strength of the prepared geopolymer, whereas fly ash content had the least influence. The lower the water-cement ratio, the higher the geopolymer strength, whereas the lower the fly ash content, the higher the geopolymer strength.