Development of a sustainable anti-washout soil-fly ash-slag-based geopolymer grout for offshore scour protection

¹ Shenzhen Research Institute of Shandong University, Shenzhen 518057, China
² School of Qilu Transportation, Shandong University, Jinan 250002, China
³ Xinjiang Research Institute of Shandong University, Changji 831100, China

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

This study aims to develop an anti-washout geopolymer grout using dredged river sediments (DRS), fly ash (FA), and ground granulated blast-furnace slag (GGBS) to mitigate scour around offshore structure foundations. The anti-washout soil-FA-GGBS (AWSFG) grout consisted of 70% DRS and 30% FA-GGBS (1:1), activated with sodium silicate solution and NaOH, and modified with 0.1% polyacrylamide (PAM) to improve washout resistance. The grout was prepared at a 1, 1.2, and 1.4 modulus value and 6%, 8%, and 10% Na2O content. The performance of AWSFG grout was evaluated for fluidity, setting time, turbidity (anti-dispersion test), washout resistance, and unconfined compressive strength (UCS) at 3 days and 28 days curing periods. The AWSFG grout produces a fluidity in the range of 123-155 mm, exhibits a turbidity value between 16-62 NTU, minimum initial and final setting time of 105 and 227 minutes, washout resistance (97.84%-99.66%), and UCS values between 1.87 and 9.52 MPa. The results showed that the performance of AWSFG grout depends upon the modulus and Na2O content. The sample M1.2N10 demonstrates optimum performance considering all parameters. Microstructural analysis revealed that the co-existence of ettringite, NASH, CASH, and CSH gel strengthens AWSFG grout. The properties of the AWSFG confirm its effectiveness as a robust anti-scouring grout.