Synthesis of pervious fly ash based geopolymer concrete for pH adjustment and nickel removal potential

• Main Author: Tran, Truc-Quynh K.
• Format: text
• Language: English
• Published: Animo Repository 2019
• Subjects: Fly ash; Inorganic polymers; Aggregates (Building materials)—Testing; Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/6399; https://animorepository.dlsu.edu.ph/context/etd_masteral/article/13467/viewcontent/ThesisManuscripts_Tran2_Redacted.pdf
• Institution: De La Salle University

Thermal power plants in the Philippines generate every year millions of tons of coal fly ash and the disposal of such waste has been a burden to the generator. Therefore, the utilization of coal fly ash for various applications has gained the interest of the researchers. In this study, coal fly ash-based geopolymer was explored as an alternative to Portland cement to produce pervious concrete. Geopolymer is an inorganic polymer with a three-dimensional structure that is formed from reacting silica-rich and alumina-rich materials in alkaline liquid. On the other hand, pervious concrete is becoming popular for Low Impact Development (LID) of infrastructure such as urban pavement which can be effective in treating contaminated water by removing the undesirable pollutants. This work explored the use of full factorial design of experiment to evaluate the effect of mix proportion on the permeability, void content, and compressive strength of pervious coal fly ash-based geopolymer concrete. Experimental factors including fly ash/coarse aggregate (FA/CA) ratio, coarse aggregate (CA) size, alkaline liquid/fly ash (AL/FA) ratio, and sodium hydroxide (NaOH) molarity were employed. The results from statistical analysis indicate that the coarse aggregate size has a significant effect on compressive strength, permeability, and void content of pervious geopolymer concrete. The compressive strength ranges from 0.478 – 2.089 MPa whereas the permeability and void content range from 1.665 – 2.390 cm/s and 31.39 – 40.00 %, respectively. The pH adjustment and nickel removal of the selected pervious geopolymer concrete were also evaluated. From an initial pH of 2 of the Ni-contaminated water, the pH increases ranging from 10 – 12 after passing through the pervious geopolymer. Indication suggests precipitation as one possible mechanism of Ni removal with the observed removal efficiency of 87 – 98 %.