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Author: Kamal H. Khayat Publisher: ISBN: Category : Bridges Languages : en Pages : 82
Book Description
The project presented in this report aimed to develop an effective methodology to use saturated lightweight sand (LWS) for internal curing to enhance concrete performance and prolong service life of concrete structures. High-performance concrete (HPC) mixtures approved by MoDOT for pavement and bridge deck structures were used for the baseline mixtures. Five different types of saturated LWS employed at various contents were investigated to evaluate the optimum dosage of LWS and maximize its effectiveness on enhancing concrete performance. The content of LWS was varied to ensure the introduction of internal curing water that can secure up to 150% of the water consumed by chemical shrinkage during cement hydration (As per ASTM C1761). Performance improvement from the LWS focused mainly on reducing autogenous and drying shrinkage and the resulting cracking potential without sacrificing durability and cost competence. Proper combinations of internal and external curing were found to enhance shrinkage mitigation. Under 7 days of initial moisture curing, HPC made with the LWS3 resulted in the lowest overall shrinkage. The Bridge-LWS2-150% exhibited the best performance in mitigating autogenous shrinkage where the concrete maintained 160 micro-strain of expansion even after 175 days of age. The lowest drying shrinkage was obtained with the Bridge-LWS3-50% mixture (340 micro-strain) at 175 days subjected to 28 days of moist curing. For the paving HPC, the lowest drying shrinkage at 155 days was obtained with the Paving-LWS3-150% mixture (265 micro-strain) subjected to 28 days of moist curing. Concrete proportioned with the LWS2 expanded shale LWS exhibited the best compressive strength, regardless of the curing regime. In terms of initial moisture curing duration, the application of 7 days of moisture curing resulted in the highest compressive strength compared with other curing conditions. The 56-day compressive strength of HPC designated for bridge deck construction that was made with the LWS1 was up to 10 MPa (1,450 psi) greater than the Bridge-Reference concrete made without any LWS. The Bridge-LWS2-100% and Bridge-LWS1-50% mixtures exhibited the highest 56-day MOE of 42.5 GPa (6,615 ksi) under Standard curing. The Bridge-LWS3-100% mixture cured under Standard conditions had the highest 56-day flexural strength of 5.5 MPa (800 psi). The mixtures made with LWS2 presented the lowest sorptivity, regardless of the curing condition and LWS content. The findings from this comprehensive project provided a basis for: (1) new mixture design methodology and guidelines for using LWS for internal curing for bridge deck and pavement applications; and (2) validation of performance improvement when using internal curing and cost competitiveness in the State of Missouri.
Author: Kamal H. Khayat Publisher: ISBN: Category : Bridges Languages : en Pages : 82
Book Description
The project presented in this report aimed to develop an effective methodology to use saturated lightweight sand (LWS) for internal curing to enhance concrete performance and prolong service life of concrete structures. High-performance concrete (HPC) mixtures approved by MoDOT for pavement and bridge deck structures were used for the baseline mixtures. Five different types of saturated LWS employed at various contents were investigated to evaluate the optimum dosage of LWS and maximize its effectiveness on enhancing concrete performance. The content of LWS was varied to ensure the introduction of internal curing water that can secure up to 150% of the water consumed by chemical shrinkage during cement hydration (As per ASTM C1761). Performance improvement from the LWS focused mainly on reducing autogenous and drying shrinkage and the resulting cracking potential without sacrificing durability and cost competence. Proper combinations of internal and external curing were found to enhance shrinkage mitigation. Under 7 days of initial moisture curing, HPC made with the LWS3 resulted in the lowest overall shrinkage. The Bridge-LWS2-150% exhibited the best performance in mitigating autogenous shrinkage where the concrete maintained 160 micro-strain of expansion even after 175 days of age. The lowest drying shrinkage was obtained with the Bridge-LWS3-50% mixture (340 micro-strain) at 175 days subjected to 28 days of moist curing. For the paving HPC, the lowest drying shrinkage at 155 days was obtained with the Paving-LWS3-150% mixture (265 micro-strain) subjected to 28 days of moist curing. Concrete proportioned with the LWS2 expanded shale LWS exhibited the best compressive strength, regardless of the curing regime. In terms of initial moisture curing duration, the application of 7 days of moisture curing resulted in the highest compressive strength compared with other curing conditions. The 56-day compressive strength of HPC designated for bridge deck construction that was made with the LWS1 was up to 10 MPa (1,450 psi) greater than the Bridge-Reference concrete made without any LWS. The Bridge-LWS2-100% and Bridge-LWS1-50% mixtures exhibited the highest 56-day MOE of 42.5 GPa (6,615 ksi) under Standard curing. The Bridge-LWS3-100% mixture cured under Standard conditions had the highest 56-day flexural strength of 5.5 MPa (800 psi). The mixtures made with LWS2 presented the lowest sorptivity, regardless of the curing condition and LWS content. The findings from this comprehensive project provided a basis for: (1) new mixture design methodology and guidelines for using LWS for internal curing for bridge deck and pavement applications; and (2) validation of performance improvement when using internal curing and cost competitiveness in the State of Missouri.
Author: Publisher: ISBN: Category : Concrete Languages : en Pages : 113
Book Description
Internally cured concrete has been rapidly emerging over the last decade as an effective way to improve the performance of concrete. Internal curing (IC) holds promise for producing concrete with an increased resistance to early-age cracking and enhanced durability. It is a simple and effective way to cure concrete.
Author: Kyllastinen Karri Publisher: LAP Lambert Academic Publishing ISBN: 9783659662669 Category : Languages : en Pages : 92
Book Description
Internal curing was used already in the Roman times, for example the famous Pantheon building is done partly with internally cured concrete. The external curing of concrete such as fogging the surface only achieves the surface of the concrete, with internal curing the whole 3-dimensional microstructure of the concrete could be cured. The objective of this thesis was to study the impact of internal curing on compressive strength, tensile/flexural strength and drying shrinkage. The goal was also to determine which grain sizes lightweight aggregates will be the best in internal curing use. In this thesis the internal curing is done with lightweight aggregates. The obtained tests results showed that the best grain size of lightweight aggregates for internal curing are 0-2 mm and 2-4 mm. The usage of these sizes enabled to produce concrete having similar mechanical properties to normal concretes but significantly reduced drying shrinkage.
Author: Kienan Dalesandro Publisher: ISBN: Category : Languages : en Pages :
Book Description
A significant portion of municipal solid waste has traditionally been addressed through recycling; however, the recycling market has become unreliable due to the stringent contamination regulations imposed by Chinas new recycling policy. Solid waste can be addressed through incineration which reduces the volume of the waste. Waste-to-Energy facilities provide an efficient means to carry out the incineration process by generating electricity through steam generation. Although it is not completely waste free, this process leaves a by-product known as municipal solid waste incinerator ash that can be further refined into a lightweight sand material known as reclaimed sands. This work investigates the use of reclaimed sands from the York County Solid Waste Authority in York, PA as a partial replacement for fine aggregates to make internally cured concrete. In internally cured concrete, interior particles release water during the cement hydration process and effectively help the mix cure from the inside out. This leads to a less permeable concrete that increases the freeze-thaw resistance, reduces chloride permeability, and improves the shrinkage resistance of the material. Reclaimed sands are effective internal curing aggregates, since they have a high absorption capacity and the ability to desorb water at a high relative humidity. The testing performed in this work explores the durability of internally cured concrete manufactured with reclaimed sands by assessing the freeze thaw resistance, rapid chloride permeability, and compressive strength of the concrete. As is discussed in later chapters of this work, it was found that reclaimed sands are a suitable replacement for lightweight aggregate in internal curing concrete applications.
Author: Weijin Zhao Publisher: ISBN: Category : Civil engineering Languages : en Pages : 188
Book Description
Curing has been considered as an essential process for cementitious materials. Proper curing enables the cement to hydrate developing its potential strength and improving its durability. Inadequate curing can lead to the plastic shrinkage cracking and stress due to drying or temperature changes. Using external water or placing a curing compound on the surface of the concrete to reduce water loss due to evaporation are traditional ways of curing concrete. These methods may not cure the entire concrete and may require longer curing time. Methods have been proposed to help increase curing efficiency such as providing internal curing in concrete. Internal curing is often referred to as curing concrete from the inside by using pre-wetted porous lightweight aggregate (LWA) to provide additional curing water throughout the concrete mixture. This thesis focuses on a novel lightweight aggregate, Spherical Porous Reactive Aggregate (SPoRA), which is produced from waste coal combustion bottom ash and its potential use for internal curing in cementitious system. The production of SPoRA is first introduced in this study, which is converting bottom ash to porous lightweight aggregate using sintering process. Physical properties of SPoRA such as specific gravity and vacuum absorption were determined and analyzed. The LWA used for internal curing should supply a sufficient volume of water to counteract the effect of self-desiccation. Therefore, the water absorption property test was conducted to determine if SPoRA could absorb sufficient water. Once mixing the SPoRA with cement, the desorption property of releasing water for internal curing is also significant as SPoRA should be able to release water over time to properly cure concrete internally. The loss of water from SPoRA can be described through a desorption isotherm that was determined using sorption analyzer in this study. Finally, the physical properties, absorption and desorption behavior of SPoRA are compared to two traditional types of lightweight aggregate (i.e., Expanded Shale, Clay, and Slate) and one foamed glass (produced from waste glass) available in the market.
Author: Peter C. Taylor Publisher: CRC Press ISBN: 0415779529 Category : Technology & Engineering Languages : en Pages : 220
Book Description
Curing is one of those activities that every civil engineer and construction worker has heard of, but in reality does not worry about much. In practice, curing is often low on the list of priorities on the construction site, particularly when budgets and timelines are under pressure. Yet the increasing demands being placed on concrete mixtures also mean that they are less forgiving than in the past. Therefore, any activity that will help improve hydration and so performance, while reducing the risk of cracking, is becoming more important. Curing Concrete explains exactly why curing is so important and shows you how to best do it. The book covers: The fundamentals behind hydration How curing affects the properties of concrete, improving its long-term performance What curing technologies and techniques you can use for different applications How to effectively specify, provide, and measure curing in a project The author also gives numerous examples of how curing—or a lack of it—has affected concrete performance in real-world situations. These include examples from hot and cold climates, as well as examples related to high-performance concrete, performance parameters, and specifications and testing. Written for construction professionals who want to ensure the quality and longevity of their concrete structures, this book demonstrates that curing is well worth the effort and cost.
Author: Mohamed Sameer Afifi Publisher: ISBN: Category : Concrete Languages : en Pages : 218
Book Description
Abstract: Concrete curing is of paramount importance in order for concrete to meet performance requirements. Conventionally, curing has been conducted by means of water sparkling, wet burlap or a curing compound. For performance and environmental reasons, internal curing has been gaining increased attention. However, more data is needed for the effectiveness of this curing technique when used in various concrete mixtures. This investigation addresses potential utilization of internal curing in high performance concrete (HPC). Internal curing was introduced by means of three aggregates: perlite, pumice and recycled aggregates; all of which were incorporated into HPC mixtures. Conventional mixtures were prepared and were thoroughly cured either by water or by a curing compound or left non-cured. Fresh concrete and Hardened concrete properties were assessed including slump, unit weight, compressive and flexural strength, and durability tests as shrinkage assessment, rapid chloride permeability test (RCPT) and abrasion resistance. Experimental work is backed up with a simplified feasibility analysis with case study, incorporating initial and future costs to better judge potential of this technique. The outcome of this study uncovers that the addition of pre-wetted lightweight aggregates can prompt an enhancement in concrete workability and durability accompanied by a reduced shrinkage. Compressive and flexural strengths decreased with the increased replacement dosages, however several dosages were tested to reach a figure of optimum replacement. Results of this study reveal the potential of this technology in saving fresh water as well as the costs saved in maintenance and rehabilitation works.
Author: Kamal H. Khayat
Author: Kamal H. Khayat
Author: Dalia Youssef
Author: 
Author: John Schlitter
Author: Ole Mejlhede Jensen
Author: Kyllastinen Karri
Author: Kienan Dalesandro
Author: Weijin Zhao
Author: Peter C. Taylor
Author: Mohamed Sameer Afifi