Author: Ali, Hafiz Asad
Title: Use of waste glass in geopolymer based repairing materials
Advisors: Poon, Chi Sun (CEE)
Degree: Ph.D.
Year: 2023
Subject: Glass waste -- Recycling
Recycling (Waste, etc.)
Hong Kong Polytechnic University -- Dissertations
Department: Department of Civil and Environmental Engineering
Pages: xvii, 200 pages : color illustrations
Language: English
Abstract: Recently, the utilization of various municipal solid wastes and agricultural ashes for ordinary Portland cement substitution, partially or wholly, is relatively low and mainly restricted to ground granulated blast furnace slag (GGBS) and pulverized fly ash (PFA). The availability of GGBS and PFA is becoming difficult soon due to severe environmental impacts related to steel manufacturing and coal burning. This motivates researchers to open avenues for alternative raw materials. Waste glass is known as an alkali-siliceous amorphous material and can be used in cement and concrete. However, using such waste needs an efficient and practical procedure to estimate its long-term reactivity.
Thus, in phase I of this research, a wide range of solid wastes, including incinerated bottom ash (IBA), different colored soda-lime glass powders, fluorescent lamp glass powder (FLGP), and PFA, were tested to evaluate their reactivities. It was found that there were moderate correlations between the 180-day relative strengths (RS180day) of standard mortars and the bound water contents or portlandite consumption of the R3 method. Moreover, the mortar strength values of the modified lime reactivity test were adequately correlated with the RS180day of the standard mortars. In comparison, the portlandite consumption values of the Chapelle test had a poor correlation with RS180day. In addition, the studied materials can be classified as lowly-reactive (IBA), moderately-reactive (MGP, BGP, WGP, GGP, BGP, FLGP), and highly-reactive (PFA) SCMs.
Attempt was made to use waste glass powder (WGP) to control efflorescence occurrence in AAS (phase II). The experimental results revealed that incorporating WGP to replace GGBS in alkali-activated WGP/GGBS (AASG) pastes reduced the compressive strengths and prolonged the setting time because of the low reactivity of WGP. Although using WGP as a replacement for GGBS decreased the strength, the incorporation of 75% WGP in AASG reduced the severity of efflorescence effectively. This reduction can be related to the lower Na/Si, Ca/Si ratios, and the higher Si/Al ratio in C-(N)-A-S-H gel phases.
Microbial-induced corrosion of ordinary Portland cement concrete due to its low biogenic acid resistance is a global concern, requiring scientists to develop sustainable alternative binders (phase III). The biogenic acid resistance of alkali-activated WGP/GGBS mortars prepared with the incorporation of various amounts of calcium aluminate cement (CAC) was investigated. The results revealed that incorporating CAC to replace GGBS at 15% in the alkali-activated cement (AAC) mortars improved the resistance to microbial-induced corrosion due to incorporating more Al into the AAC gels.
In phase IV, the optimized content of WGP in preparing alkali-activated repairing materials (phase IV) was found to be about 50% for obtaining a good bond strength of 1.28 MPa, shrinkage of about 1900 ยต strain, and an intact substrate-repairing mortar interfacial zone. This mixture can be classified as a non-structural class R2 repairing mortar as per BS EN 1504 specifications.
Furthermore, AAC mortars initially prepared with waste glass powder (WGP): ground granulated blast furnace slag (GGBS) = 50:50 (by wt.%) as binding materials and glass cullet (GC) as aggregate, was modified by 10% mass replacement of GGBS with different mineral modifiers including incinerated sewage sludge ash (ISSA), calcium aluminate cement (CAC), metakaolin (MK), and MK with zinc ferrite nanoparticles aiming to enhance the properties of resulting mixtures against the biogenic activity. The experimental results indicated that only 50GP40GGBS10CAC improved the strength developments, while incorporating ISSA or MK in AAC mortars reduced the strengths which was attributed to their lower reactivities. Moreover, zinc ferrite nanoparticles (heavy metal ions) prolonged the induction period and impacted the strength negatively. Interestingly, the positive impact of heavy metal ions provided by 50GP40GGBS10ISSA or 50GP40GGBS10MK-1.5 in minimizing the biofilm generation and corrosion-layer depth could not compensate for the negative impact of strength development and alkalis leaching. Besides, the heavy metal release posed a low risk to the environment due to the low leachate concentration (lower than that specified by U.S. EPA), indicating the beneficial encapsulation behavior of AAMs on metals. Regarding the key performance indicators (KPI) which include strength and mass losses, and neutralization and corrosion-layer depths, the biogenic acid resistance of 50GP40GGBS10CAC was superior. This might be related to the Al-rich C-N-A-S-H gel phases and a finer pore structure. Lastly, the specimen 50GP40GGBS10CAC can be suggested as microbial acid resistant material to rehabilitate concrete sewers.
Rights: All rights reserved
Access: open access

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