Mechanical and Durability Analysis of Fly Ash Based Geopolymer with Various Compositions for Rigid Pavement Applications

Abstract

Ordinary Portland cement (OPC) is a conventional material used to construct rigid pavement that emits large amounts of carbon dioxide (CO2) during its manufacturing process, which is bad for the environment. It is also claimed that OPC is susceptible to acid attack, which increases the maintenance cost of rigid pavement. Therefore, a fly ash based geopolymer is proposed as a material for rigid pavement application as it releases lesser amounts of CO2 during the synthesis process and has higher acid resistance compared to OPC. This current study optimizes the formulation to produce fly ash based geopolymer with the highest compressive strength. In addition, the durability of fly ash based geopolymer concrete and OPC concrete in an acidic environment is also determined and compared. The results show that the optimum value of sodium hydroxide concentration, the ratio of sodium silicate to sodium hydroxide, and the ratio of solid-to-liquid for fly ash based geopolymer are 10 M, 2.0, and 2.5, respectively, with a maximum compressive strength of 47 MPa. The results also highlight that the durability of fly ash based geopolymer is higher than that of OPC concrete, indicating that fly ash based geopolymer is a better material for rigid pavement applications, with a percentage of compressive strength loss of 7.38% to 21.94% for OPC concrete. This current study contributes to the field of knowledge by providing a reference for future development of fly ash based geopolymer for rigid pavement applications.

Influence of Fe2O3, MgO and Molarity of NaOH Solution on the Mechanical Properties of Fly Ash-Based Geopolymers

“…The increase in mechanical strength, with the increase in molarity of the NaOH solution used in the preparation of the alkaline activator, could be attributed, in addition to the maturation in time and the completion of the geopolymer reactions, to the contribution of Na+ ions and OH- groups provided by the alkaline activator. Thus, in accordance with the literature, with references on the main steps of the geopolymerization mechanism, it is appreciated that both Na+ ions and hydroxyl groups play an important role in the dissolution and hydrolysis processes, breaking the bonds existing in the Si and Al source raw materials, contributing to produce Si-O-Al bonds, bonds known as geopolymer precursors [ 51 ]. More specifically, Na+ ions contribute to the balancing of negative charges produced by Si-O-Al formation, while OH ions play an essential role in the hydrolysis process of the geopolymer, producing the geopolymerization reaction and the formation of the aluminosilicate network with stable, stronger bonds, which ultimately lead to better mechanical strength of the material.…”

Preparation and Application of Polyaluminum Ferric Sulfate from Red Mud: Behaviors of Leaching, Polymerizing, and Coagulation

“…The red mud dump can produce strong alkaline leachate, which can also harm people and animals near the dump . Therefore, many researchers have used red mud, fly ash, and coal gangue to prepare geopolymers and roadbed materials and achieved some good application results. , However, it is worth noting that the red mud contains many available chemical components such as aluminum, iron, and scandium, in which the content of aluminum and iron accounts for 40–60% of the total amount. , Efficient recovery of aluminum and iron from red mud is an important way for its comprehensive utilization of “reduction, recycling, and harmlessness”. At present, the extraction of aluminum and iron from red mud mainly involves magnetization roasting-magnetic separation for the recovery of iron and alkali roasting-alkali leaching for the recovery of aluminum.…”

“… 2 Therefore, many researchers have used red mud, fly ash, and coal gangue to prepare geopolymers and roadbed materials and achieved some good application results. 3 , 4 However, it is worth noting that the red mud contains many available chemical components such as aluminum, iron, and scandium, in which the content of aluminum and iron accounts for 40–60% of the total amount. 5 , 6 Efficient recovery of aluminum and iron from red mud is an important way for its comprehensive utilization of “reduction, recycling, and harmlessness”.…”

The Influence of Fly Ash Contents on Mechanical Properties and Energy Response of Concrete at a High Strain Rate

“…If fy ash was discarded directly into the natural environment, it would cause signifcant pollution to the environment. However, fy ash as a concrete preparation material could change the performance of traditional concrete [4,5] on the one hand, and it could also reduce the manufacturing cost of concrete and reduce environmental pollution [6][7][8] on the other hand. Terefore, it was of great engineering signifcance to study the mechanical properties and energy response characteristics of fy ash concrete under the high strain rate for the application of fy ash concrete in the environment with rock burst.…”