Download or read book Evaluation of High Absorptive Materials to Improve Internal Curing of Low Permeability Concrete written by Norbert J. Delatte and published by . This book was released on 2007 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Early age cracking of bridge decks is a national problem, and may substantially reduce service lives and increase maintenance costs. Cracking occurs when the tensile stress exceeds the tensile strength of the concrete. This is a time-dependent phenomenon, since both the stress and strength change at early ages. Moisture loss increases stress (with increasing shrinkage) and impairs strength gain. Internal curing is one method that has been suggested to reduce early age bridge deck cracking, particularly of concretes with low water to cementitious materials (w/cm) ratios. Many state highway agencies have implemented high performance concrete (HPC) for bridge decks. The low permeability of HPC is used to protect reinforcing steel and prevent corrosion. However, if the concrete cracks, then the protection may be greatly diminished. Transverse cracks due to concrete shrinkage allow water and corrosive chemicals to quickly reach the reinforcing steel causing corrosion and shortening the lifespan of the bridge deck. Reducing shrinkage cracking has been the focus of recent research into mitigation strategies. One unintended consequence of the use of high performance concrete may be early-age cracking. Field studies have shown that, in some cases, high performance concrete bridge decks have cracked less than a year after placement. The use of internal curing to reduce autogenous shrinkage was investigated in this study. One method of internal curing was through the use of coarse aggregates with high absorption capacities. Another method discussed is the use of a partial replacement of the fine aggregate with a structural lightweight aggregate with a very high absorption capacity. Bridge deck cracking is also affected by the nominal maximum size coarse aggregate. The effect on shrinkage with increasing size is discussed. ODOT's District 12, located in Northeastern Ohio, found in an investigation of 116 HPC bridge decks placed between 1994 and 2001 that bridges with little or no cracking used coarse aggregate with an absorption> 1 %, while 75 % of bridges with unacceptable cracking used coarse aggregate with absorption 1 %. This report discusses the laboratory investigation of the field results to determine the better ways to prevent bridge deck cracking-- internal curing or paste reduction by using an aggregate blend. The laboratory investigation found that the strongest effect on cracking was due to the replacement of a small maximum size coarse aggregate with an optimized coarse aggregate gradation. Increasing the coarse aggregate absorption level from

Download or read book Moisture Transport in Cement Based Materials written by Javier Eduardo Castro and published by . This book was released on 2011 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: The durability of concrete subjected to aggressive environments depends largely on the transport properties of the concrete. These transport properties are influenced by the volume of pores as well as the connectivity of the pore network. Three main mechanisms can be used to describe transport in cementitious systems: permeability, diffusion and absorption. Permeability is the measure of the flow of water under a pressure gradient. Diffusion is the movement of ions due to a concentration gradient. Absorption can be described as the ability to take in water by means of capillary suction. It is important to note that absorption occurs on a much faster time scale than diffusion. A large fraction of concrete in service is only partly saturated and the initial ingress of fluid is influenced, at least in part, by capillary absorption. As such, fluid (water) absorption has been used as an important factor for quantifying the durability of cementitious systems and it is being increasingly used by specifiers and in forensic studies to provide a parameter that can describe an aspect of concrete durability. For this reason the water absorption test is the focus of the first part of this thesis. The influence of preconditioning and initial moisture content was assessed as it relates to the water absorption test measurements. The results confirm that the test is considerably affected by the relative humidity of the samples before starting the test, which if not properly accounted for can lead to a misunderstanding of the actual absorption behavior. It was also observed that the conditioning procedure described in ASTM C1585 is not able to eliminate the "moisture history" of the samples. As such modifications to the standard test procedure are suggested. Further, the absorption behavior was investigated when salts were present in the samples or as a part of the absorbing fluid. Tests were performed on concrete using different aqueous solutions containing deicing salts. The rate of fluid absorption was generally lower for aqueous solutions containing deicing salts than it was for water (with the exception of low concentrations of NaCl). The change in the rate of aqueous fluid absorption was proportional to the square root of the ratio of surface tension and viscosity of the absorbed fluid. Experimental data indicates that concretes that had previously been exposed to deicing solutions can also exhibit reduced rate of absorption, even if water is the fluid being absorbed. The second part of this thesis is focused on the internal curing for concrete and its effect on the transport properties. The increased propensity for shrinkage cracking in low waterto- cement ratio (w/c) concrete has inspired the development of new technologies that can reduce the risk of early-age cracking. One of these is internal curing. Internal curing uses pre-wetted lightweight aggregate (LWA) to supply "curing water" to low w/c paste as it hydrates. Significant research has been performed to determine the effects of internal curing on shrinkage and stress development; however, relatively little detailed information exists about the effects of internal curing on fluid transport properties such as water absorption. In order to determine the mixture proportions for internally cured concretes information about the water absorption and water desorption properties of the lightweight aggregate is needed. Unfortunately, these properties are not easy to obtain accurately. This work studies the absorption and desorption properties of commercially available expanded shale, clay and slate lightweight aggregates. This research determines these properties so that they can be efficiently used in proportioning concrete for internal curing. Further, it was shown that by normalizing the results general trends on material behavior can be obtained that are quite useful in proportioning the mixtures. After characterizing the properties of the aggregates to be used for internal curing, this research examines the absorption of water into low w/c mortar specimens made with prewetted lightweight aggregates. These results indicate that the inclusion of LWA can reduce the water absorption of mortar specimens. This observation was reinforced with electrical conductivity measurements that exhibited similar reductions. In addition, this work analyzes the potential use of internal curing in concrete systems with w/c higher than normally used (w/c of 0.30, 0.36, 0.42 and 0.45) to increase the durability of the concrete. Test results show that internal curing can be useful to improve the durability of concretes prepared with this wider range of w/c. The benefits of using internal curing on the transport properties can be explained by an increase in the hydration of the cement. This was assessed using isothermal calorimeter, internal relative humidity, scanning electron microscopy and an atomic force microscopy. Further, in addition to reducing the porosity, the increased hydration appears to reduce the tortuosity by preferentially hydrating the interfacial regions around the lightweight aggregate.

Download or read book Application of Super Absorbent Polymers SAP in Concrete Construction written by Viktor Mechtcherine and published by Springer Science & Business Media. This book was released on 2012-01-03 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the state-of-the-art report prepared by the RILEM TC “Application of Super Absorbent Polymers (SAP) in concrete construction”. It gives a comprehensive overview of the properties of SAP, specific water absorption and desorption behaviour of SAP in fresh and hardening concrete, effects of the SAP addition on rheological properties of fresh concrete, changes of cement paste microstructure and mechanical properties of concrete. Furthermore, the key advantages of using SAP are described in detail: the ability of this material to act as an internal curing agent to mitigate autogenous shrinkage of high-performance concrete, the possibility to use SAP as an alternative to air-entrainment agents in order to increase the frost resistance of concrete, and finally, the benefit of steering the rheology of fresh cement-based materials. The final chapter describes the first existing and numerous prospective applications for this new concrete additive.

Download or read book Concrete Permeability and Durability Performance written by Roberto J. Torrent and published by CRC Press. This book was released on 2021-12-22 with total page 536 pages. Available in PDF, EPUB and Kindle. Book excerpt: Durability and service life design of concrete constructions have considerable socio-economic and environmental consequences, in which the permeability of concrete to aggressive intruders plays a vital role. Concrete Permeability and Durability Performance provides deep insight into the permeability of concrete, moving from theory to practice, and presents over 20 real cases, such as Tokyo’s Museum of Western Art, Port of Miami Tunnel and Hong Kong-Zhuhai-Macao sea-link, including field tests in the Antarctic and Atacama Desert. It stresses the importance of site testing for a realistic durability assessment and details the "Torrent Method" for non-destructive measurement of air-permeability. It also delivers answers for some vexing questions: Should the coefficient of permeability be expressed in m2 or m/s? How to get a "mean" pore radius of concrete from gas-permeability tests? Why should permeability preferably be measured on site? How can service life of reinforced concrete structures be predicted by site testing of gas-permeability and cover thickness? Practitioners will find stimulating examples on how to predict the coming service life of new structures and the remaining life of existing structures, based on site testing of air-permeability and cover thickness. Researchers will value theoretical principles, testing methods, as well as how test results reflect the influence of concrete mix composition and processing.

Download or read book Concrete Repair Rehabilitation and Retrofitting IV written by Frank Dehn and published by CRC Press. This book was released on 2015-09-17 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Fourth International Conference on Concrete Repair, Rehabilitation and Retrofitting (ICCRRR 2015) was held 5-7 October 2015 in Leipzig, Germany. This conference is a collaborative venture by researchers from the South African Research Programme in Concrete Materials (based at the Universities of Cape Town and The Witwatersrand) and the Material

Download or read book Autogenous Shrinkage of Concrete written by Ei-ichi Tazawa and published by CRC Press. This book was released on 1999-01-28 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book forms the proceedings of a workshop held in Hiroshima in June 1998 and derive from the work of a Technical Committee of the Japan Concrete Institute. Topics include test and prediction methods, the science of autogenous shrinkage, strain and stress, and consequent design concerns.

Download or read book Objective Question Bank in Chemistry written by B.K. Sharma and published by Krishna Prakashan Media. This book was released on 1997 with total page 1700 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design and Control of Concrete Mixtures written by Steven H. Kosmatka and published by . This book was released on 1988 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: Portland Cement Association reference, dealing with fundamentals, cold weather concreting, curing, admixtures, aggregates, mixing, and much more.

Download or read book Handbook of Low Carbon Concrete written by Ali Nazari and published by Butterworth-Heinemann. This book was released on 2016-09-30 with total page 443 pages. Available in PDF, EPUB and Kindle. Book excerpt: Handbook of Low Carbon Concrete brings together the latest breakthroughs in the design, production, and application of low carbon concrete. In this handbook, the editors and contributors have paid extra attention to the emissions generated by coarse aggregates, emissions due to fine aggregates, and emissions due to cement, fly ash, GGBFS, and admixtures. In addition, the book provides expert coverage on emissions due to concrete batching, transport and placement, and emissions generated by typical commercially produced concretes. Includes the tools and methods for reducing the emissions of greenhouse gases Explores technologies, such as carbon capture, storage, and substitute cements Provides essential data that helps determine the unique factors involved in designing large, new green cement plants

Download or read book Nonconventional Concrete Technologies written by Committee on Nonconventional Concrete Technologies for Renewal of the Highway Infrastructure and published by National Academies Press. This book was released on 1997-04-08 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nonconventional Concrete Technologies: Renewal of the Highway Infrastructure identifies research and development opportunities in innovative, nonconventional materials and processes that have the potential to accelerate the construction process, improve the durability of highway pavement and bridges, and enhance the serviceability and longevity of new construction under adverse conditions.

Download or read book Self Healing Cementitious Materials written by Ghasan Fahim Huseien and published by CRC Press. This book was released on 2022-05-03 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: Climate change is anticipated to have a major impact on concrete structures through increasing rates of deterioration and the impact of extreme weather events. The repair of any damage will be highly labor-intensive and expensive. Self-healing cementitious materials can enable the construction industry to mitigate these effects and move toward greater sustainability, safety, and increased cost savings and efficiency. This book: Examines concrete structures based on various materials with self-repair capability and their implications for future use in sustainable projects. Discusses advantages and design strategies of self-healing concretes. Covers several effective and detailed self-repair methods, with comparative analysis of the advantages and disadvantages of each method. Examines the use of various materials, including polymers and nanomaterials. Reviews factors affecting performance, properties, and applications. Delves into future directions and opportunities. Written for researchers, advanced students, and industry professionals, Self-Healing Cementitious Materials: Technologies, Evaluation Methods, and Applications offers a detailed view of an important emerging technology in materials science, civil engineering, and related fields.

Download or read book Concrete Mixture Proportioning written by Francois de Larrard and published by CRC Press. This book was released on 1999-03-04 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt: The design of concrete mixes is becoming increasingly complex, with the addition of new materials in the compounds, such as organic admixtures, fibres and supplementary cementitious materials. Moreover, the list of properties which concretes are required to possess for certain applications has increased, and interest is developing in rheology, durability, deformability and whole-life behaviour. This book presents a number of simple models for the understanding of a concrete system, and provides the techniques for developing more sophisticated models for the practical design of concrete mixes.

Download or read book Advances in Construction and Demolition Waste Recycling written by F Pacheco Torgal and published by Woodhead Publishing. This book was released on 2020-02-10 with total page 594 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Construction and Demolition Waste Recycling: Management, Processing and Environmental Assessment is divided over three parts. Part One focuses on the management of construction and demolition waste, including estimation of quantities and the use of BIM and GIS tools. Part Two reviews the processing of recycled aggregates, along with the performance of concrete mixtures using different types of recycled aggregates. Part Three looks at the environmental assessment of non-hazardous waste. This book will be a standard reference for civil engineers, structural engineers, architects and academic researchers working in the field of construction and demolition waste. Summarizes key recent research in recycling and reusing concrete and demolition waste to reduce environmental impacts Considers techniques for managing construction and demolition waste, including waste management plans, ways of estimating levels of waste, and the types and optimal location of waste recycling plants Reviews key steps in handling construction and demolition waste

Download or read book Cementitious Materials written by Herbert Pöllmann and published by Walter de Gruyter GmbH & Co KG. This book was released on 2017-12-18 with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aside from water the materials which are used by mankind in highest quantities arecementitious materials and concrete. This book shows how the quality of the technical product depends on mineral phases and their reactions during the hydration and strengthening process. Additives and admixtures infl uence the course of hydration and the properties. Options of reducing the CO2-production in cementitious materials are presented and numerous examples of unhydrous and hydrous phases and their formation conditions are discussed. This editorial work consists of four parts including cement composition and hydration, Special cement and binder mineral phases, Cementitious and binder materials, and Measurement and properties. Every part contains different contributions and covers a broad range within the area. Contents Part I: Cement composition and hydration Diffraction and crystallography applied to anhydrous cements Diffraction and crystallography applied to hydrating cements Synthesis of highly reactive pure cement phases Thermodynamic modelling of cement hydration: Portland cements – blended cements – calcium sulfoaluminate cements Part II: Special cement and binder mineral phases Role of hydrotalcite-type layered double hydroxides in delayed pozzolanic reactions and their bearing on mortar dating Setting control of CAC by substituted acetic acids and crystal structures of their calcium salts Crystallography and crystal chemistry of AFm phases related to cement chemistry Part III: Cementitious and binder materials Chemistry, design and application of hybrid alkali activated binders Binding materials based on calcium sulphates Magnesia building material (Sorel cement) – from basics to application New CO2-reduced cementitious systems Composition and properties of ternary binders Part IV: Measurement and properties Characterization of microstructural properties of Portland cements by analytical scanning electron microscopy Correlating XRD data with technological properties No cement production without refractories

Download or read book High Strength Concrete written by Michael A. Caldarone and published by CRC Press. This book was released on 2014-04-21 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: This practical book from a highly experienced author presents clearly the means and methods for designing, producing and using high-strength concrete. High-strength concrete offers many benefits. Higher compressive strengths allow for a reduction in the cross-sectional dimensions of columns and walls in buildings. Its greater stiffness allows for increasing building heights while controlling sway and occupant comfort. Civil structures such as bridges have benefited from greater span lengths, shallower beam sections, wider girder spacing, and extended service life. Illustrated with real life examples, through documented case histories, High-Strength Concrete will be a valuable resource for contractors, producers, inspection agencies, as well as engineers and researchers.

Download or read book Guide for Modeling and Calculating Shrinkage and Creep in Hardened Concrete written by and published by . This book was released on 2008-01-01 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book ACI Materials Journal written by and published by . This book was released on 2008 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: