Ceramics-Silikáty 69, (1) 9 - 18 (2025) |
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FLY ASH-BASED GEOPOLYMER MORTARS USING SEAWATER AND SEA SAND |
Truc Thai Thanh 1,2, Minh Huynh Ngoc 1,2, Minh Do Quang 1,2 |
1 Department of Silicate Materials, Faculty of Materials Technology, Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam
2 Vietnam National University Ho Chi Minh City, Linh Trung Ward, Thu Duc City, Ho Chi Minh City, Vietnam
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Keywords: 35‰ salinity Seawater, Alkaline activator solution, Hydrothermal treatment, Drying treatment, Phillipsite-Na. |
Geopolymers are a commonly researched binder material due to their properties equivalent to Portland cement (PC). Unlike PC, the geopolymer can be used in seawater environments without the risk of sulfate and chloride attacks. Due to the scarcity of river sand and freshwater sources, it is necessary to use sea sand and seawater in construction, especially in coastal areas and islands. In this study, seawater with a salinity of 35‰ (representing the highest seawater salinity in Vietnam) and sea sand were used to produce fly ash-based geopolymer mortars with the NaOH concentration of the alkaline activator solution (AAS) ranging from 4 M to 12 M. The fly ash (FA) used was sourced from the Duyen Hai 1 thermal power plant, the natural sea sand was collected from the coast of Vung Tau in southern Vietnam. The mortar specimens were cured under different conditions, including drying and hydrothermal treatment at a pressure of about 9 atmospheres for 16 hours. The experimental results showed that the hydrothermal treatment significantly enhanced the compressive strength of the geopolymer material and detected to the formation of phillipsite-Na crystals, commonly observed in hydrothermal-treated geopolymer materials. The FTIR and SEM analyses also identified the characteristic bonds and microstructure of the geopolymer in the samples. The 28-day compressive strength of the 12 M hydrothermal-treated sample reached up to 49.6 MPa, demonstrating the potential of a fly ash-based geopolymer mortar using seawater and sea sand. Additionally, it is noteworthy that the setting time of geopolymer mortars lasts up to 60 hours. |
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doi: 10.13168/cs.2024.0061 |
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