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Mechanisms of Biogenic Acid Degradat...

Gevaudan, Juan Pablo.

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Mechanisms of Biogenic Acid Degradation of Low-Calcium Alkali-Activated Cements.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Mechanisms of Biogenic Acid Degradation of Low-Calcium Alkali-Activated Cements./
Author:	Gevaudan, Juan Pablo.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2019,
Description:	154 p.
Notes:	Source: Dissertations Abstracts International, Volume: 81-04, Section: B.
Contained By:	Dissertations Abstracts International81-04B.
Subject:	Architectural engineering. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=22592250
ISBN:	9781088375679

Mechanisms of Biogenic Acid Degradation of Low-Calcium Alkali-Activated Cements.
Gevaudan, Juan Pablo.

Mechanisms of Biogenic Acid Degradation of Low-Calcium Alkali-Activated Cements. - Ann Arbor : ProQuest Dissertations & Theses, 2019 - 154 p.

Source: Dissertations Abstracts International, Volume: 81-04, Section: B.

Thesis (Ph.D.)--University of Colorado at Boulder, 2019.

This item must not be sold to any third party vendors.

Alkali-activated cements (AACs) are alternative cements with the potential to counter durability concerns associated with the use of ordinary portland cement (OPC), as further discussed in Chapter I. As a result of their superior durability, AACs have been proposed as material solutions to microbial-induced concrete corrosion-a pervasive durability challenge concerning the acid degradation of wastewater infrastructure, as explained in Chapter II. The main objective of this dissertation was to investigate the effect of supplementary ions (i.e., Cu, Co, Si, Mg, Fe) on the mechanisms of acid degradation (i.e., dealumination) and relevant material properties of low-calcium AACs. Chapter III investigates the acid degradation of low-calcium AAC materials supplemented with heavy metals (i.e., Cu, Co), known for their anti-microbial properties. Results from this work demonstrate that heavy metals improve the acid resistance of AACs and explicitly elucidate the role of hydronium ions (H3O+), which penetrate past the visually observable corrosion layer and induce cationic exchange, resulting in electrophilic degradation of the Si-O-Al bonds with concomitant beneficial cationic dissolution of minerals. In Chapter IV, the effect of processing conditions on material porosity was correlated to short-term mineralogical stability of low-calcium AACs. Results indicate that sodium content dictates the short-term mineralogical stability and, hence, microstructural formation of certain aluminosilicate zeolitic minerals. These can either decrease (faujasite formation) or increase (zeolite A formation) permeable porosity, substantiating the importance of favorable versus non-favorable zeolite formation. Secondly, Chapter V investigates the effect of an iron-rich mineral admixture (i.e., hematite) on the acid resistance of low-calcium AACs. Results indicate that iron-rich mineral admixtures improve AAC acid resistance by increasing micro-sized porosity, while also inducing increases to Fe:Al ratios, which are correlated with compressive strength and microstructure (Si-O-Al) preservation. Thirdly, to contrast with hematite, a mineral-rich in heavy metal (i.e., Fe), Chapter VI investigates the effect of a light metal, magnesium-rich mineral admixture (i.e., brucite). Results indicate that addition of brucite improves the acid resistance of low-calcium AACs by increasing the pH buffering capacity of the material. Moreover, observed Mg:Al ratio increases after exposure indicates a spatial-temporal cation re-arrangement, which preserves the micro- and nano-scale porosity.

ISBN: 9781088375679Subjects--Topical Terms:

3174102
Architectural engineering.
Subjects--Index Terms:

Acid degradation

Mechanisms of Biogenic Acid Degradation of Low-Calcium Alkali-Activated Cements.
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500 $a Source: Dissertations Abstracts International, Volume: 81-04, Section: B.
500 $a Advisor: Srubar, Wil V., III.
502 $a Thesis (Ph.D.)--University of Colorado at Boulder, 2019.
506 $a This item must not be sold to any third party vendors.
520 $a Alkali-activated cements (AACs) are alternative cements with the potential to counter durability concerns associated with the use of ordinary portland cement (OPC), as further discussed in Chapter I. As a result of their superior durability, AACs have been proposed as material solutions to microbial-induced concrete corrosion-a pervasive durability challenge concerning the acid degradation of wastewater infrastructure, as explained in Chapter II. The main objective of this dissertation was to investigate the effect of supplementary ions (i.e., Cu, Co, Si, Mg, Fe) on the mechanisms of acid degradation (i.e., dealumination) and relevant material properties of low-calcium AACs. Chapter III investigates the acid degradation of low-calcium AAC materials supplemented with heavy metals (i.e., Cu, Co), known for their anti-microbial properties. Results from this work demonstrate that heavy metals improve the acid resistance of AACs and explicitly elucidate the role of hydronium ions (H3O+), which penetrate past the visually observable corrosion layer and induce cationic exchange, resulting in electrophilic degradation of the Si-O-Al bonds with concomitant beneficial cationic dissolution of minerals. In Chapter IV, the effect of processing conditions on material porosity was correlated to short-term mineralogical stability of low-calcium AACs. Results indicate that sodium content dictates the short-term mineralogical stability and, hence, microstructural formation of certain aluminosilicate zeolitic minerals. These can either decrease (faujasite formation) or increase (zeolite A formation) permeable porosity, substantiating the importance of favorable versus non-favorable zeolite formation. Secondly, Chapter V investigates the effect of an iron-rich mineral admixture (i.e., hematite) on the acid resistance of low-calcium AACs. Results indicate that iron-rich mineral admixtures improve AAC acid resistance by increasing micro-sized porosity, while also inducing increases to Fe:Al ratios, which are correlated with compressive strength and microstructure (Si-O-Al) preservation. Thirdly, to contrast with hematite, a mineral-rich in heavy metal (i.e., Fe), Chapter VI investigates the effect of a light metal, magnesium-rich mineral admixture (i.e., brucite). Results indicate that addition of brucite improves the acid resistance of low-calcium AACs by increasing the pH buffering capacity of the material. Moreover, observed Mg:Al ratio increases after exposure indicates a spatial-temporal cation re-arrangement, which preserves the micro- and nano-scale porosity.
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653 $a Cations
653 $a Geopolymers
653 $a Mineral adxmixtures
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710 2 $a University of Colorado at Boulder. $b Civil, Environmental, and Architectural Engineering. $3 3350108
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