Download or read book Effect of High Curing Temperatures on the Strength Durability and Potential of Delayed Ettringite Formation in Mass Concrete Structures written by Lucy Acquaye and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 3. Concrete mixes containing 18% fly ash and 50% slag and cured at the elevated temperatures resulted in much lower permeability. The low permeability of the blends delayed the onset of ettringite formation as well as the amount formed when compared to the plain cement mixes. This was particularly evident in the slag mixes.

Download or read book Optical Phenomenology and Applications written by Masoud Ghandehari and published by Springer. This book was released on 2018-05-26 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is an introduction to techniques and applications of optical methods for materials Characterization in civil and environmental engineering. Emphasizing chemical sensing and diagnostics, it is written for students and researchers studying the physical and chemical processes in manmade or natural materials. Optical Phenomenology and Applications - Health Monitoring for Infrastructure Materials and the Environment, describes the utility of optical-sensing technologies in applications that include monitoring of transport processes and reaction chemistries in materials of the infrastructure and the subsurface environment. Many of the applications reviewed will address long standing issues in infrastructure health monitoring such as the alkali silica reaction, the role of pH in materials degradation, and the remote and inset characterization of the subsurface environment. The remarkable growth in photonics has contributed immensely to transforming bench-top optical instruments to compact field deployable systems. This has also contributed to optical sensors for environmental sensing and infrastructure health monitoring. Application of optical waveguides and full field imaging for civil and environmental engineering application is introduced and chemical and physical recognition strategies are presented; this is followed by range of filed deployable applications. Emphasizing system robustness, and long-term durability, examples covered include in-situ monitoring of transport phenomena, imaging degradation chemistries, and remote sensing of the subsurface ground water.

Download or read book Delayed Ettringite Formation DEF in Structural Lightweight Aggregate Concrete written by M. Rønne and published by . This book was released on 1999 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results confirm that the self-desiccation of normal density (ND) high strength concrete may prevent delayed ettringite formation (DEF). However, when using lightweight aggregate (LWA), the initial water content of the LWA grains seems to be sufficient to give some DEF. The results also confirm that the critical temperature, provided that the moisture content is sufficiently high, is in the range of 65 to 70°C for ND concrete with Norwegian cements. The critical temperature for LWA concrete seems to be somewhat higher; above 70°C. The LWA expansion due to DEF seems to be somewhat lower than the expansion of ND concrete, provided they have the same binder and paste quality. The volume increase coincides with an extensive compressive strength reduction. The reported results confirm that addition of silica fume (5%) in combination with the investigated cements, seems to prevent or eliminate the DEF.

Download or read book The Effect of Secondary Ettringite Formation on the Durability of Concrete written by Robert L. Day and published by Portland Cement Association. This book was released on 1992 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: The report comprises a review and analysis of the available literature pertaining to the causes, effects and prevention of secondary (delayed) ettringite in concrete . Over 300 publications have been examined . Case studies of damage in concrete possibly caused by secondary ettringite formation are examined first. Fundamental research on secondary ettringite formation, its chemistry, and deposition mechanisms is then reviewed. Key investigations on the topic are analyzed in detail. Next, the potential importance of (a) method of heat-curing and (b) the chemistry of cement is outlined. In the final chapter, a rapid test for evaluation of potential secondary ettringite susceptibility (the "Duggan" test) is evaluated. The analysis indicates that there appears to be a potential for a secondary ettringite formation problem in North America; it is highly probable that secondary ettringite formation can lead to significant deterioration of heat-treated concrete. However, it is unlikely that secondary ettringite formation is, or will be, the sole mechanism responsible for premature deterioration. The critical factors that determine extent of damage due to secondary ettringite formation are (a) duration of delay period before heating the concrete; (b) severity of the heating and/or cooling regime ; and (c) the SO3/A1203 ratio of the cement. There is no evidence that nonheat-treated concrete is susceptible to this phenomenon. Further research and improvements to the Duggan test may result in the development of a useful standard test method to assess the long-term dimensional stability and durability of concrete.

Download or read book Role of Heat Curing in Concrete Durability written by Stephen Okurut Ekolu and published by . This book was released on 2004 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phase One investigation was conducted to determine the effect of high-temperature curing on the physical properties of concrete. Portland cement pastes of 0.35 and 0.45 water-cement ratios, and ternary cement (5% silica fume, 25% slag) concretes of 0.35 water-cementitious ratio were cured at 23, 65, 80, and 95°C. The properties examined were the compressive strength, chloride permeability, bulk diffusion, salt scaling, rebar corrosion, pore structure, and microstructure. Results showed that there were drastic changes in concrete properties as the curing temperatures increased above 65°C. This has been termed the 'critical temperature effect'. Salt scaling of concretes was highly sensitive to elevated curing temperatures but the w/c was found to be more influential. Most adverse effects of heat curing were significantly mitigated by using ternary cement concrete except in the case of compressive strength.--Phase Two investigation examined the influence of other deterioration processes on the potential for DEF. The effects of lithium admixtures, alkali-silica reaction and freeze-thaw microcracks, and chloride ingress were investigated using concretes of 0.45 w/c and mortars of o.47 w/c heat cured at 95°C. Studies included X-ray diffraction and differential thermal analysis. It was found that the use of lithium admixture in cementitious systems controls DEF. Also, externally applied chlorides have a pessimum effect on expansion due to DEF. This deviates from the commonly held view that chlorides mitigate sulphate attack in concretes. A mechanism describing the pessimum effect of chlorides on DEF expansion has been proposed.

Download or read book Construction Materials and Structures written by S.O. Ekolu and published by IOS Press. This book was released on 2014-12-05 with total page 1562 pages. Available in PDF, EPUB and Kindle. Book excerpt: The two volumes of these Proceedings contain about 200 conference papers and 10 keynote papers presented at the First International Conference on Construction Materials and Structures, held in Johannesburg, South Africa from 24 to 26 November 2014. It includes sections on Materials and characterization; Durability of construction materials; Structural implications, performance, service life; Sustainability, waste utilization, the environment; and Building science and construction.

Download or read book Role of Heat Curing in Concrete Durability microform Effects of Lithium Salts and Chloride Ingress on Delayed Ettringite Formation written by Stephen Okurut Ekolu and published by Library and Archives Canada = Bibliothèque et Archives Canada. This book was released on 2004 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phase One investigation was conducted to determine the effect of high-temperature curing on the physical properties of concrete. Portland cement pastes of 0.35 and 0.45 water-cement ratios, and ternary cement (5% silica fume, 25% slag) concretes of 0.35 water-cementitious ratio were cured at 23, 65, 80, and 95°C. The properties examined were the compressive strength, chloride permeability, bulk diffusion, salt scaling, rebar corrosion, pore structure, and microstructure. Results showed that there were drastic changes in concrete properties as the curing temperatures increased above 65°C. This has been termed the 'critical temperature effect'. Salt scaling of concretes was highly sensitive to elevated curing temperatures but the w/c was found to be more influential. Most adverse effects of heat curing were significantly mitigated by using ternary cement concrete except in the case of compressive strength.--Phase Two investigation examined the influence of other deterioration processes on the potential for DEF. The effects of lithium admixtures, alkali-silica reaction and freeze-thaw microcracks, and chloride ingress were investigated using concretes of 0.45 w/c and mortars of o.47 w/c heat cured at 95°C. Studies included X-ray diffraction and differential thermal analysis. It was found that the use of lithium admixture in cementitious systems controls DEF. Also, externally applied chlorides have a pessimum effect on expansion due to DEF. This deviates from the commonly held view that chlorides mitigate sulphate attack in concretes. A mechanism describing the pessimum effect of chlorides on DEF expansion has been proposed.

Download or read book The Effects of Liquid Nitrogen on Concrete Properties written by Maria C. G. Juenger and published by . This book was released on 2008 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book PRO 35 International RILEM Workshop on International Sulfate Attack and Delayed Ettringite Formation written by Karen Scrivener and published by RILEM Publications. This book was released on 2004 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Emerging Trends in Civil Engineering written by K. Ganesh Babu and published by Springer Nature. This book was released on 2020-01-11 with total page 393 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book comprises select papers from the International Conference on Emerging Trends in Civil Engineering (ICETCE 2018). Latest research findings in different branches of civil engineering such as structural engineering, construction materials, geotechnical engineering, water resources engineering, environmental engineering, and transportation infrastructure are covered in this book. The book also gives an overview of emerging topics like smart materials and structures, green building technologies, and intelligent transportation system. The contents of this book will be beneficial for students, academicians, industrialists and researchers working in the field of civil engineering.

Download or read book Alkali Aggregate Reaction in Concrete written by Ian Sims and published by CRC Press. This book was released on 2017-08-01 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt: Alkali-Aggregate Reaction in Concrete: A World Review is unique in providing authoritative and up to date expert information on the causes and effects of Alkali-Aggregate Reaction (AAR) in concrete structures worldwide. In 1992 a first edition entitled The Alkali-Silica Reaction in Concrete, edited by Professor Narayan Swamy, was published in a first attempt to cover this concrete problem from a global perspective, but the coverage was incomplete. This completely new edition offers a fully updated and more universal coverage of the world situation concerning AAR and includes a wealth of new evidence and research information that has accumulated in the intervening years. Although there are various textbooks offering readers sections that deal with AAR deterioration and damage to concrete, no other single book brings together the views of recognised international experts in the field, and the wealth of scattered research information that is available. It provides a ‘state of the art’ review and deals authoritatively with the mechanisms of AAR, its diagnosis and how to treat concrete affected by AAR. It is illustrated by numerous actual examples from around the world, and comprises specialist contributions provided by senior engineers and scientists from many parts of the world. The book is divided into two distinct but complementary parts. The first five chapters deal with the most recent findings concerning the mechanisms involved in the reaction, methods concerning its diagnosis, testing and evaluation, together with an appraisal of current methods used in its avoidance and in the remediation of affected concrete structures. The second part is divided into eleven chapters covering each region of the world in turn. These chapters have been written by experts with specialist knowledge of AAR in the countries involved and include an authoritative appraisal of the problem and its solution as it affects concrete structures in the region. Such an authoritative compilation of information on AAR has not been attempted previously on this scale and this work is therefore an essential source for practising and research civil engineers, consultant engineers and materials scientists, as well as aggregate and cement producers, designers and concrete suppliers, especially regarding projects outside their own region.

Download or read book Delayed Ettringite Formation in Portland Cement Products written by Yan Fu and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The thesis presents the results of an extensive research program on the deterioration of Portland cement concrete due to delayed ettringite formation (DEF). The study focuses on three aspects: (i) the mechanisms of DEF; (ii) a test method to determine the DEF potential of a given cement; (iii) some preventive measures to reduce the deterioration of portland cement products due to DEF. The research work indicates that C-S-H gel will adsorb sulfate fast at high temperature resulting in quick depletion of the gypsum phase in the portland cement-water system. Sulphate absorbed at high temperature is desorbed more slowly than that adsorbed at normal temperatures. Slower release of sulfate from an internal sulfate source may be a critical condition for DEF in high temperature cured Portland cement paste. Nucleation of a crystal requires less surface energy in a crack than in the cement paste matrix. Sulfate ions, after release from the C-S-H gel, will diffuse into the nearest microcrack and react with the Al-bearing materials in the crack to nucleate and crystallize ettringite. Growth of ettringite crystals opens the crack and damages the cement products. A test method to determine the expansion potential, due to delayed ettringite formation (DEF), of portland cements initially moist-cured at high temperatures was developed. Expansion of cement mortars made with eight different portland cements was investigated. Different test parameters, such as, curing temperature, type of sand, sand/cement ratio, specimen size and pre-treatment, were studied to select the optimal test conditions and procedures. Expansion/time criteria to evaluate the DEF potential of a given cement from the results of this test method are discussed. Siliceous materials can be used in portland cement products to reduce or eliminate deterioration due to DEF. Different siliceous materials have different characteristics relevant to the reduction of the deleterious expansion. The granulated blast-furnace slag, ggbs, and Class F fly ash are more effective in reducing the DEF expansion than Class C fly ash, silica fume and natural zeolite. The expansion of the mortar containing a siliceous material appears to be much delayed. Therefore long-term expansion should be considered in the selection of a siliceous material for use in a DEF-suspect cement. Microcracks play an important role in the expansion due to DEF. Control of microcracks using wollastonite micro-fibres should reduce the expansion of a DEF-suspect cement mortar.

Download or read book Effect of Initial Curing Temperatures on the Compressive Strength and Durability of Concrete written by and published by . This book was released on 1952 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Duration of Moist Curing on Concrete Made with Blended Cements Or Pozzolans written by William O. Tynes and published by . This book was released on 1969 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Duration of Moist Curing on the Relative Durability of Concrete in Freezing and Thawing written by U.S. Army Engineer Waterways Experiment Station and published by . This book was released on 1962 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Influence of Fly Ash and Early age Curing Temperature on the Durability and Strength of High Performance Concrete written by Christopher Michael Evans and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Early-stage curing temperature has a significant effect on high performance concrete durability and strength. Concrete cures at high temperatures when poured in large volumes due to the autogeneous heat generated by the hydration reactions of cementitious materials. The addition of supplementary cementing materials to concrete reduces the heat of hydration and extends the service life in structures by improving both long term durability and strength. This thesis investigates the effects of early-age curing temperature on the durability and strength of silica fume and fly ash modified concretes. Accelerated test methods were used to measure chloride diffusion in concretes produced with silica fume cement (T10SF) and various levels and types of fly ash replacement. The concrete mix determined to be the most durable with respect to chloride diffusion had 56% of the Type 10SF cement replaced with a moderate-level calcium content fly ash. The use of the Rapid Chloride Permeability Test, (ASTM C 1202, AASHTO T 277) has been widely criticised. Despite a limited data set, good correlation was shown in the results of this research between a two-chamber accelerated chloride migration cell test, and the RCPT.

Download or read book Ettringite written by Bernard Erlin and published by . This book was released on 1999 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: