Phase development in cement hydrate systems

Much progress has been made in understanding the physicomechanical properties of blended cement pastes of various formulations. However, unanswered questions abound, particularly as it concerns the long term chemistry of mineral distribution as clinker is diluted with progressively more supplementar...

Full description

Bibliographic Details
Main Author: Okoronkwo, Monday Uchenna
Published: University of Aberdeen 2014
Subjects:
540
Online Access:http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633279
id ndltd-bl.uk-oai-ethos.bl.uk-633279
record_format oai_dc
spelling ndltd-bl.uk-oai-ethos.bl.uk-6332792016-08-04T04:18:32ZPhase development in cement hydrate systemsOkoronkwo, Monday Uchenna2014Much progress has been made in understanding the physicomechanical properties of blended cement pastes of various formulations. However, unanswered questions abound, particularly as it concerns the long term chemistry of mineral distribution as clinker is diluted with progressively more supplementary cementitious materials (SCM's) and as a greater fraction of blending agent reacts with cement with time. This Thesis describes progress towards elucidating the mineralogical evolution mainly by isothermal equilibrium of known compositions. The evolution of mineralogy of two major systems: the calcium-alumina-silica-water (CASH) system and sodium-calcium-alumina-silica-water (NCASH) systems were studied at 20 – 85 °C, using ~70 compositions. Phase assemblage models have been developed for the systems, demonstrating the mode of occurrence and coexistence of phases with respect to temperature and composition. The coexistence of gels, one based on calcium silicate hydrate (C-S-H), the other based on aluminosilicate hydrate (A-S-H), and crystalline phases such as hydrogarnet solid solution, strätlingite and gismondine-Ca in the CASH system at 20 – 85°C, are illustrated. Transformation of gels to their corresponding crystalline phases has been predicted. Similarly, models are presented showing the mode of occurrence and coexistence of portlandite, alumina hydrate, silica, tobermorite, strätlingite, hydrogarnet solid solution, gismondine- type zeolite (Na,Ca)P solid solution, zeolite A, zeolite X, sodalite, etc., at temperatures 20 – 85 °C for the NCASH system. The stability and properties of the various crystalline CASH phases such as, hydrogarnet solid solution, strätlingite and gismondine, in relation to other phases relevant to cement hydration – such as C-S-H, AFts, AFms, gypsum and calcite – are characterized. The impact of sulfate, carbonate, alkali and solid solution on phase stability in systems relevant to aluminosilicate substituted cement paste are investigated. Concerns on long-term evolution of pH and its consequences to the passivation of cement-steel composite are discussed.540University of Aberdeenhttp://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633279http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=215261Electronic Thesis or Dissertation
collection NDLTD
sources NDLTD
topic 540
spellingShingle 540
Okoronkwo, Monday Uchenna
Phase development in cement hydrate systems
description Much progress has been made in understanding the physicomechanical properties of blended cement pastes of various formulations. However, unanswered questions abound, particularly as it concerns the long term chemistry of mineral distribution as clinker is diluted with progressively more supplementary cementitious materials (SCM's) and as a greater fraction of blending agent reacts with cement with time. This Thesis describes progress towards elucidating the mineralogical evolution mainly by isothermal equilibrium of known compositions. The evolution of mineralogy of two major systems: the calcium-alumina-silica-water (CASH) system and sodium-calcium-alumina-silica-water (NCASH) systems were studied at 20 – 85 °C, using ~70 compositions. Phase assemblage models have been developed for the systems, demonstrating the mode of occurrence and coexistence of phases with respect to temperature and composition. The coexistence of gels, one based on calcium silicate hydrate (C-S-H), the other based on aluminosilicate hydrate (A-S-H), and crystalline phases such as hydrogarnet solid solution, strätlingite and gismondine-Ca in the CASH system at 20 – 85°C, are illustrated. Transformation of gels to their corresponding crystalline phases has been predicted. Similarly, models are presented showing the mode of occurrence and coexistence of portlandite, alumina hydrate, silica, tobermorite, strätlingite, hydrogarnet solid solution, gismondine- type zeolite (Na,Ca)P solid solution, zeolite A, zeolite X, sodalite, etc., at temperatures 20 – 85 °C for the NCASH system. The stability and properties of the various crystalline CASH phases such as, hydrogarnet solid solution, strätlingite and gismondine, in relation to other phases relevant to cement hydration – such as C-S-H, AFts, AFms, gypsum and calcite – are characterized. The impact of sulfate, carbonate, alkali and solid solution on phase stability in systems relevant to aluminosilicate substituted cement paste are investigated. Concerns on long-term evolution of pH and its consequences to the passivation of cement-steel composite are discussed.
author Okoronkwo, Monday Uchenna
author_facet Okoronkwo, Monday Uchenna
author_sort Okoronkwo, Monday Uchenna
title Phase development in cement hydrate systems
title_short Phase development in cement hydrate systems
title_full Phase development in cement hydrate systems
title_fullStr Phase development in cement hydrate systems
title_full_unstemmed Phase development in cement hydrate systems
title_sort phase development in cement hydrate systems
publisher University of Aberdeen
publishDate 2014
url http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633279
work_keys_str_mv AT okoronkwomondayuchenna phasedevelopmentincementhydratesystems
_version_ 1718373428966195200