Performance Of Cement Based Materials In Aggressive Aqueous Environments

Concrete and cement-based materials must operate in increasingly aggressive aqueous environments, which may be either natural or industrial. These materials may suffer degradation in which ion addition and/or ion exchange reactions occur, leading to a breakdown of the matrix microstructure and consequent weakening. Sometimes this degradation can be extremely rapid and serious such as in acidic environments, while in other cases degradation occurs over long periods. Consequences of material failure are usually severe – adversely affecting the health and well-being of human communities and disturbing ecological balances. There are also large direct costs of maintaining and replacing deteriorated infrastructure and indirect costs from loss of production during maintenance work, which place a great burden on society. The focus of this book is on addressing issues concerning performance of cement-based materials in aggressive aqueous environments , by way of this State-of-the-Art Report. The book represents the work of many well-known and respected authors who contributed chapters or parts of chapters. Four main themes were addressed: I. Nature and kinetics of degradation and deterioration mechanisms of cement-based materials in aggressive aqueous environments, II. Modelling of deterioration in such environments, III. Test methods to assess performance of cement-based materials in such environments, and which can be used to characterise and rate relative performance and inform long term predictions, IV. Engineering implications and consequences of deterioration in aggressive aqueous environments, and engineering approaches to the problem.

This thesis studies the effects of superplasticizers, polyacrylate latexes and asphalt emulsions, which differ in molecular/particle size from nanometers to microns, on the rheological properties of fresh cement pastes (FCPs), as well as the action mechanisms involved. It systematically investigates the rheological properties and microstructure of cement-based materials, and elucidates the adsorption behaviors of polycarboxylate polymers with different functional groups and their effects on cement hydration. Moreover, it reveals how the working mechanism of naphthalene sulfonate formaldehyde (NSF) differs from that of polycarboxylate ether-based (PCE) superplasticizers. Lastly, it develops a conceptual microstructure model and two rheological equations. These findings lend theoretical support to the development of new chemical admixtures and new, higher-performance, cement-based composites.

This volume gathers contributions from the final workshop of the RILEM TC-251-SRT "Sulfate Resistance Testing" on External Sulfate Attack (TESA 2018), held on May 24-25, 2018 at IETcc-CSIC, Madrid, Spain. One of the Technical Committee’s main events, it addressed various aspects of external sulfate attack in concrete structures and test methods. The workshop promoted technical discussions and debates on ideas on these topics, with a focus on evaluating the resistance of concrete exposed to ESA. It also provided a forum for participants from around the globe to share their experiences and research on concrete structures affected by external sulfate attack and on test methods. The book discusses the latest advances in research related to ESA and new developments in test methods, and features real-world case studies of concrete structures affected by external sulfate attack in various countries. It also presents new studies linking field cases and lab tests, including 12 contributions on 3 main themes: mechanisms of alteration in external sulfate attack; field aspects of external sulfate attack; and testing to evaluate the resistance of concrete to external sulfate attack.

Photoactive nanomaterials have been receiving increasing attention due to their potential application in the light-driven degradation of water and gas-phase pollutants. However, to exploit the great potential of photoactive materials and access their properties requires fine-tuning of their size/shape-dependent chemical–physical properties, and on the ability to integrate them in photoreactors or to deposit them onto large surfaces. Therefore, the synthetic approach as well as post-synthesis manipulation could strongly affect the final photocatalytic properties of the nanomaterial. The aim of the present Special Issue is to report on the most recent progress towards the application of photoactive nanomaterials and nanomaterial-based coatings in pollutant degradation, paying particular attention to cases close to real application: scalable synthetic approaches to nanocatalysts, preparation of nanocatalyst-based coatings, degradation of real pollutants and bacterial inactivation, and application in building materials.