Download or read book Shrinkage and Shrinkage Cracking Behavior of Cement Systems Containing Ground Limestone Fly Ash and Lightweight Synthetic Particles written by Brooks E. Bucher and published by . This book was released on 2009 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: Low water-to-cement (w/c) ratio concrete with a high paste content experiences significant autogenous shrinkage that may amplify the risk of earlyage cracking in restrained elements. Further, the high cement content of these materials increases the carbon-footprint and environmental impact of these materials due to energy consumption and CO2 emissions associated with cement production. This thesis introduces strategies to produce concrete which reduces or displays similar cracking propensity to traditional cement-based materials, although with a smaller environmental impact. This can be achieved by: 1) replacement of a portion of cement with limestone, 2) fundamentally altering the binder composition by incorporation of alternative binders such as fly ash, or 3) by replacing a portion of the natural aggregate in concrete with synthetic inclusions which reduce the risk of cracking. First, this study evaluates early-age and long-term volume changes in pastes and mortars made with cements interground with limestone; for a variety of curing times and exposure conditions. The results show mortars made using cements interground with up to 10% limestone (by mass replacement of cement) demonstrate similar or less early-age and long-term shrinkage as compared to plain cement systems. Limestone systems showed a similar or reduced risk of early-age cracking. Further studies were performed using fine, intermediate, and coarse limestone particles to examine the effects of limestone particle size and xviii dilution (due to cement replacement by limestone) on the shrinkage and cracking response of pastes and mortars. Finally, the chemical shrinkage and heat of hydration were measured to evaluate whether the presence of limestone alters the rate of reaction in these materials. Second, this study evaluates the shrinkage and cracking behavior of cement-based materials that contain fly ash. Two types of fly ash were examined. The chemical shrinkage of mixtures containing up to 20% fly ash (mass replacement of cement) was measured to quantify the early-age reactivity of fly ash in binders. Autogenous and total bulk shrinkage due to drying was studied from the time of set up to 28 days. The volume change and cracking susceptibility results varied depending upon type of fly ash and replacement amount. Third, this research includes the study of concrete and mortars that contain low stiffness synthetic aggregate inclusions as a method to mitigate early-age cracking. Restrained and plastic shrinkage of concrete and mortar containing lightweight synthetic particles (LSP) as aggregate replacement are studied. The results indicate a reduction in the potential for cracking with increased replacement of LSP. Furthermore the addition of LSP reduces the susceptibility for plastic shrinkage cracking.

Download or read book Effects of Flyash on the Chemical Autogenous Shrinkage Behaviour written by Souptik Sarkar and published by LAP Lambert Academic Publishing. This book was released on 2012 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: For a concrete structure to be serviceable, cracking must be controlled and deflections must not be excessive. It must also not vibrate excessively. Concrete shrinkage plays a major role in each of these aspects of the service load behaviour of concrete structures. Volume change is one of the most detrimental properties of concrete, which affects the long-term strength and durability. The change in volume of concrete commences as soon as the cement and water comes in contact during the mixing process, but these changes in volume are generally not taken into account since their extent is much less than shrinkage due to drying. Even with ideal curing conditions the first day shrinkage resulting from volume fluctuations can significantly reduce the ultimate shrinkage and result in development of cracks. Early age properties of concrete widely influence the long term properties of concrete. This work extensively deals with the parameters of early age concrete and how the same can be controlled by means of fly ash.

Download or read book Creep and Shrinkage Behavior of Fly Ash Based Geopolymer Concrete written by Mudhammad Rashedul Islam and published by . This book was released on 2015 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Reducing Shrinkage Cracking of Structural Concrete Through the Use of Admixtures written by Tarun R. Naik and published by . This book was released on 2006 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 424 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 Properties of Concretes Made with Fly Ash and Cements Containing Limestone written by Rachel J. Detwiler and published by . This book was released on 1996 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Comparison of the Compressive Strength and Shrinkage of Portland Cement fly Ash Concrete With the Chemical Constituents of the Fly Ash written by William Joseph Lnenicka and published by Hassell Street Press. This book was released on 2021-09-09 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work has been selected by scholars as being culturally important and is part of the knowledge base of civilization as we know it. This work is in the public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. To ensure a quality reading experience, this work has been proofread and republished using a format that seamlessly blends the original graphical elements with text in an easy-to-read typeface. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.

Download or read book Models and Validation of Mechanisms and Mitigation of Early Age Shrinkage Cracking in Cement Stabilized Bases written by Stephanus Johannes Hofmeyr Louw and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation considers the effects of microcracking and improved mix design procedures on drying shrinkage cracks in full depth reclaimed pavement layers stabilized with cement (FDR-PC). The hypotheses for this dissertation are: •Microcracking can mitigate the effects of drying shrinkage cracking by inducing a network of hairline cracks to relieve the restraint stress to minimize drying shrinkage crack widths. •Improved mix design and laboratory characterization methods can increase the effective fatigue life of a full depth reclaimed layer stabilized with portland cement (FDR-PC) by accepting the presence of drying shrinkage cracks in the layer, and focusing the mix design to minimize the effects of these cracks. These hypotheses were developed from forensic investigation results of drying shrinkage cracking and fatigue cracking of the FDR-PC test track at the University of California Pavement Research Center (UCPRC), and previous research on accelerated pavement testing of cement stabilized based layers. The research approach to investigate these hypotheses consisted of: •A literature review that provided an initial basis for the work. •Extensive field investigations that were used to develop an updated proposed understating of how cement stabilized layers fail. •The evaluation of microcracking on a controlled experimental test road and its effects on reflective drying shrinkage cracks. •Laboratory testing to simulate microcracking.•Theoretical simulation of microcracking using the field and laboratory inputs. The research was based on the observation that cement stabilized layers do not fail uniformly along the pavement and that the rate of failure is dependent on the crack widths. Cement stabilized layers are often cracked from drying shrinkage creating a series of large blocks in the road. Cement stabilized layers have a range of expected effective fatigue lives along the pavement: the shortest around the widest cracks, and the longest where the slabs are intact. Through the research in this dissertation, it was shown that microcracking reduces the resistance to shrinkage cracking of the FDR-PC at the time of microcracking and forces the development of additional drying shrinkage cracks. This distributes the total drying shrinkage strain over more cracks and minimizes the accumulation of shrinkage strain at each drying shrinkage crack, reducing crack widths. In support of the first hypothesis, microcracking can increase the effective fatigue life of a cement stabilized layer by changing the condition of the base from a few wide reflective drying shrinkage cracks to a layer with many narrow drying shrinkage cracks with stress concentrations that are too small to reflect through the surface layer. By reducing the widths of the wide cracks where failure is first expected, the expected effective fatigue life of the cement stabilized layer can also be increased through improved load transfer efficiency (LTE) and aggregate interlock to reduce the stresses and strains adjacent to the cracks at the bottom of the cement stabilized layer. The interior of the slab where no cracks are present, will have the longest fatigue life, but this is not the critical area where the pavement fails . The hypothesis that microcracking mitigates drying shrinkage cracks by creating a network of hairline cracks to relieve stresses that would otherwise create a few wide cracks was amended during the course of this research. Field observations and microcracking simulations have shown that microcracking reduces the strength and effective layer thickness, leading to the development of additional shrinkage cracks and resulting in overall reduced crack widths. The influence of mix design on the stiffness of FDR-PC with microcracking was also investigated to evaluate the second hypothesis. The FDR-PC with microcracking recovered to stiffness levels greater than that of the unmicrocracked field and laboratory experiments in the lower strength mix design. The increased stiffness recovery observed after microcracking was attributed to secondary cementation as free water is mobilized through the induced microcracks to promote recementation and to hydrate previously unhydrated cement. The research has shown that increasing the water to cement for cementation ratio (w/cc), by reducing the cement content, can improve the ability of the FDR-PC to recover stiffness after microcracking. The initial consumption of stabilizer (ICS) test was considered to determine the minimum cement content to ensure durability. By using the minimum required cement content that satisfies both the strength and durability requirements, the long-term stiffness levels of the FDR-PC exceeded the stiffness levels without microcracking. This provides a two-fold benefit of reduced crack widths due to the lower strength of the material, and increased stiffness, and thus fatigue life, for the same material. This supported the second hypothesis for this research. Microcracking is a shrinkage crack control method that can mitigate large shrinkage cracks, but it needs to be considered together with the mix design to maximize the benefits microcracking can provide. The recommended microcracking effort to maximize long term stiffness and minimize crack widths developed from the results of this study is: during the period from 48 to 56 hours after compaction, microcrack the surface by applying a load per width of roller of 2.8 to 4.3 kN/cm using a 10- to 12-ton vibratory steel drum roller at maximum vibration amplitude travelling from 3 to 4.5 km/hr (2 to 3 mph). The study also recommended using the maximum of either the cement content that satisfies both the minimum seven-day design strength and the ICS plus 1 percent cement content. This research contributes extensive knowledge to the current understanding of cement stabilized layers. Cement stabilized layers still crack with microcracking, but through improved mix designs, pavement design, construction and microcracking, cement stabilized layers can last longer, and deteriorate more uniformly.

Download or read book Shrinkage and Creep of Concrete Containing 50 Lignite Fly Ash at High Temperatures written by KW. Nasser and published by . This book was released on 1987 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper investigates the influence of high temperature on the shrinkage and creep of unsealed and sealed concrete containing 50% Saskatchewan lignite fly ash and 50% Type I portland cement. Concrete was tested at six different temperatures between 70 and 450°F (21 and 232°C) and under three stress levels of 750, 1200, and 1500 psi (5.2, 8.3, and 10.3 MPa). The tests were made on 3 by 9-in. (75 by 225mm) concrete cylinders, and shrinkage and creep were measured for a maximum period of 112 days.

Download or read book Creep and shrinkage properties in concrete containing fly ash written by Mohand L. Sennour and published by . This book was released on 1989 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book PRO 23 International RILEM Conference on Early Age Cracking in Cementitious Systems EAC 01 written by Arnon Bentur and published by RILEM Publications. This book was released on 2002 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Shrinkage and Fatigue Properties of Concrete Containing High Volumes of Fly Ash written by Congli Ye and published by . This book was released on 1993 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Early age Shrinkage of Alkali activated Class F Fly Ash and Portland Cement for Long term Oil Well Zonal Isolation Control written by Raul Olvera and published by . This book was released on 2018 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volumetric changes due to shrinkage occur during the hydration/polymerization process of ordinary portland cement (OPC) and alkali-activated Class F fly ash systems. If not accounted for in the design of structures, especially those at elevated temperature and pressure conditions, shrinkage can develop internal stresses, which could generate micro-cracking. Specifically in oil and gas wells, shrinkage can compromise the hydraulic annular and result in loss of zonal isolation. This thesis compares the early-age shrinkage behavior of Class H OPC, sodium hydroxide-activated Class F fly ash (geopolymer), and geopolymer-hybrid (geopolymers incorporating drilling mud) slurries with up to 20% (by volume) synthetic based mud (SBM) contamination cured at different temperatures and pressure conditions. A study into the effectiveness of zinc- and aluminum-based expansive agents for shrinkage mitigation is also presented. Shrinkage was recorded for specimens cured at temperatures between 23 - 80°C and up to 2000 psi confining pressure. The results from testing indicate that A) temperature plays a major role in the shrinkage development of OPC and geopolymer slurries; B) pressure significantly increases OPC slurry shrinkage, but only minimally for geopolymers; C) addition of SBM increases shrinkage for OPC and geopolymer slurries; D) expansive agents can potentially counteract shrinkage in both OPC and geopolymer slurries. In addition, issues with shrinkage measurement at elevated temperature and pressure with current ASTM and API shrinkage tests are presented, along with a novel shrinkage measurement method avoiding these issues

Download or read book Shrinkage and Durability of Concrete Containing Fly Ash mixed Plastic Aggregates written by Joshua Aron Weingram and published by . This book was released on 2003 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Influence of Synthetic Fibers on Plastic Shrinkage of Self consolidating Concrete written by Rafael J. Semidey and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The addition of #89 pea gravel enhanced the grading uniformity of the aggregate, helped increased the workability of the mix, and reduced aggregate segregation and bleeding. Using a fine-aggregate-to-total-aggregate ratio of 0.50 produced the SCC mix with the best qualities. The water-cement ratio that offered a mix with good workability, no segregation, no bleeding, and an acceptable spread for the Slump and J-Ring Test was 0.36. All tested fibers proved to reduce plastic shrinkage cracking significantly. Fiber length and volume fraction showed to have an effect on plastic shrinkage cracking behavior. As fiber length and volume fraction were increased, the total crack area was reduced.

Download or read book Prediction of Autogenous Shrinkage in Fly Ash Blended Cement Systems written by Zhangli Hu and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mots-clés de l'autrice: Autogenous shrinkage ; Fly-ash-blended cement ; Self-desiccation ; Basic creep ; Microstructure evolution ; Poromechanical method ; Numerical modeling.

Download or read book ACI Materials Journal written by and published by . This book was released on 1996 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt: