The Experts below are selected from a list of 3786 Experts worldwide ranked by ideXlab platform
Luisa Duraes - One of the best experts on this subject based on the ideXlab platform.
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effect of supplementary cementitious materials on Autogenous Shrinkage of ultra high performance concrete
Construction and Building Materials, 2016Co-Authors: Ehsan Ghafari, Seyedali Ghahari, H Costa, Eduardo Julio, Antonio Portugal, Luisa DuraesAbstract:Abstract Ultra-high performance concrete (UHPC) not only presents ultra-high compressive strength but also exhibits ultra-high durability, due to its extremely dense structure and consequently highly reduced porosity. However, high dosages of silica fume (SF), typically adopted in UHPC, also lead to high Autogenous Shrinkage. This phenomenon, occurring at early ages, induces high internal stresses that, in turn, cause microcracking and increase permeability and, therefore, reduce the durability of concrete structures. The experimental study was conducted aiming to replace SF by another fine supplementary cementitious materials (SCMs), such as fly ash (FA) or ground granulated blast furnace slag (GGBS), in order to reduce the amount of Autogenous Shrinkage. The adopted approach involved partial or total replacement of SF by SCMs. Results indicate that the amount of fine pores in UHPC is a predominant factor that can highly affect the Autogenous Shrinkage. A strong correlation between the natural logarithm of Autogenous Shrinkage and the total porosity of UHPC mixtures was established. It was found that reducing the amount of fine pores in specimens containing FA or GGBS leads to a reduction of the Autogenous Shrinkage.
Geert De Schutter - One of the best experts on this subject based on the ideXlab platform.
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Autogenous Shrinkage of low water binder ratio cement pastes with supplementary cementitious materials
Fourth International Conference on Sustainable Construction Materials and Technologies (SCMT4), 2016Co-Authors: Yang Lyu, Haoliang Huang, Geert De SchutterAbstract:High-performance cementitious materials are sensitive to early age cracking, mainly due to the large magnitude of Autogenous Shrinkage, which is closely related to the internal relative humidity (RH) decrease and capillary pressure induced by self-desiccation in the cement matrix. However, there is debate about the determination of time-zero, the time at which Autogenous Shrinkage begins to develop, which causes great difficulty in comparing the results provided in the exiting researches. This study presents an accurate determination of time-zero based on the relationship between the internal RH and Autogenous Shrinkage of cementitious materials. According to the time-zero, the effect of replacements of cement by supplementary cementitious materials on the Autogenous Shrinkage was investigated for the early age cement pastes with low water/binder ratio. The Autogenous Shrinkage was conducted according to the standard method ASTM C1698. Internal RH was performed on the sealed cement pastes at very early age by conventional method of hygrometer. Setting time was determined by the Vicat needle apparatus according to the standard method ASTM C191. The results could potentially explain the mechanism of Autogenous Shrinkage at early age in mixtures with supplementary cementitious materials.
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Experimental evaluation of mitigation of Autogenous Shrinkage by means of a vertical dilatometer for concrete
International RILEM Conference on Volume Changes of Hardening Concrete: Testing and Mitigation, 2006Co-Authors: Bart Craeye, Geert De SchutterAbstract:High performance concrete, with low w/b-factors, can suffer from early age cracking due to Autogenous Shrinkage. This can lead to a relevant reduction of the service life of concrete structures. In order to study Autogenous Shrinkage of hardening concrete, a new dilatometer has been developed. Within this newly developed dilatometer, the fresh concrete is cast into a vertical Teflon tube. After compaction on a vibrating table, the concrete sample is placed into the measuring frame, inside a climate room. Linear vertical Shrinkage measurements can start immediately after casting, by means of LVDT-transducers. Temperature measurements are realized in parallel, in order to take into account the effect of the heat of hydration on the Autogenous Shrinkage results. With this dilatometer, the mitigation of Autogenous Shrinkage by means of saturated light- weight aggregate particles and super absorbing polymers has been studied experimentally. The application of theoretical formulas, predicting the required content of internal curing water in order to compensate for the Autogenous Shrinkage has been evaluated. The application of saturated light-weight aggregates and super absorbing polymers proves to be a good technique in order to reduce Autogenous Shrinkage.
Shingo Miyazawa - One of the best experts on this subject based on the ideXlab platform.
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INFLUENCE OF CONSTITUENTS AND COMPOSITION ON Autogenous Shrinkage OF CEMENTITIOUS MATERIALS
Magazine of Concrete Research, 1997Co-Authors: E. Tazawa, Shingo MiyazawaAbstract:Effects of cement type, water to binder ratio and volume concentration of aggregate on Autogenous Shrinkage of cement based materials were experimentally investigated. A large amount of Autogenous Shrinkage was observed in cement paste and concrete with low water to binder ratio. Autogenous Shrinkage increased with increasing C3A content of cement. It was also increased by using blast furnace slag with higher fineness. The effect of volunre concentration of aggregate could be estimated by an existing composite law. Some vpes of admixtures were effective in reducing Autogenous Shrinkage.
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Influence of cement and admixture on Autogenous Shrinkage of cement paste
Cement and Concrete Research, 1995Co-Authors: Ei-ichi Tazawa, Shingo MiyazawaAbstract:Abstract It has recently been proved that Autogenous Shrinkage is considerably large for highstrength concrete. In this study influences of cement, chemical admixture, mineral admixture and water-cement ratio on Autogenous Shrinkage of cement paste were experimentally studied. It was proved that Autogenous Shrinkage could be estimated form mineral composition of cement. Some admixtures which were able to reduce Autogenous Shrinkage were found.
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Experimental study on mechanism of Autogenous Shrinkage of concrete
Cement and Concrete Research, 1995Co-Authors: Ei-ichi Tazawa, Shingo MiyazawaAbstract:It was proved that Autogenous Shrinkage of high-strength concrete could be almost the same as drying Shrinkage. For cement paste with low water-cement ratio, Shrinkage was observed even in water. Existing composite low evaluated well the restraining effect of aggregate on Autogenous Shrinkage. Moisture movement caused by capillary condensation was thought to be the cause of flexural strength reduction for sealed specimens.
Gyuyong Kim - One of the best experts on this subject based on the ideXlab platform.
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analysis of hydration heat and Autogenous Shrinkage of high strength mass concrete
Magazine of Concrete Research, 2011Co-Authors: Gyuyong Kim, Euibae Lee, Jeongsoo Nam, Kyungmo KooAbstract:The early-age properties and relationships between hydration heat and Autogenous Shrinkage in high-strength mass concrete of different mixture proportions are investigated through analysis of the history curves of hydration heat and Autogenous Shrinkage. The hydration temperature and hydration heating velocity (HHV) of the concrete were found to increase with increases in specimen size and decrease when the concrete contained a retarder, fly ash (FA) and ground granulated blast-furnace slag (GGBS). Even in samples of the same mixture proportion, Autogenous Shrinkage was noted to become greater as the inner temperature increased. The Autogenous Shrinkage of high-strength mass concrete containing FA and GGBS was lower than that of ordinary Portland cement high-strength mass concrete. The Autogenous shrinking velocity of concrete increased as the size of the specimen increased and decreased when the concrete contained a retarder, FA and GGBS. Finally, a close correlation was found between the hydration tempe...
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Properties of Autogenous Shrinkage in High-Strength Mass Concrete According to Hydration Heat Velocity
Advanced Materials Research, 2011Co-Authors: Kyungmo Koo, Gyuyong Kim, Hiroyuki Miyauchi, Yeon Woo KangAbstract:The early-age properties and relationships between hydration heat and Autogenous Shrinkage in high-strength mass concrete are investigated through analysis of the history curves of hydration heat and Autogenous Shrinkage. To reduce the hydration heat velocity, micro encapsulated retarder (MR) that could retard cement reaction was applied. In the result of research, the hydration temperature and hydration heat velocity of high-strength mass concrete can be decreased with the reduction of size specimen and use of the retarder. A close relationship could be found between the hydration temperature and Autogenous Shrinkage; the higher the hydration heat velocity, the higher the Autogenous Shrinkage velocity and the greater the ultimate Autogenous Shrinkage.
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Analysis of the Relation between Hydration Heat and Autogenous Shrinkage of Concrete at Early Ages
2009Co-Authors: Euibae Lee, Kyungmo Koo, Gyuyong Kim, H J LeeAbstract:This paper presents an analysis method for histories of hydration heat and Autogenous Shrinkage at early ages is suggested in this study. The early age properties and the relation between hydration heat and Autogenous Shrinkage of high-strength concrete were investigated. In the results, most Autogenous Shrinkage of high-strength concrete occurred in a few days after casting. The shape of Autogenous Shrinkage history corresponded well to the shape of hydration temperature history at early ages. There was a close relation between hydration heat and Autogenous Shrinkage at early ages, especially between hydration heating velocity (HHV) and Autogenous shrinking velocity (ASV). And it is noted that HHV can affect the ultimate Autogenous Shrinkage.
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Hydration Heat and Autogenous Shrinkage of High-Strength Mass Concrete
Journal of Asian Architecture and Building Engineering, 2009Co-Authors: Gyuyong Kim, Euibae Lee, Kyungmo KooAbstract:In this study, to evaluate Autogenous Shrinkage of high-strength mass concrete with specimen size and hydration delay effects, the thermal deformation was calculated using thermal expansion coefficient (TEC) corrected by the maturity method, and was subtracted from measured total deformation. And the properties and relations of hydration heat and Autogenous Shrinkage at early ages were numerically analyzed. In test and analysis results, hydration temperature is affected by specimen conditions such as size and admixture, and change of hydration temperature could affect Autogenous Shrinkage; the higher hydration temperature and the greater Autogenous Shrinkage. There is a close relationship between hydration temperature and Autogenous Shrinkage at early ages, especially between HHV (hydration heating velocity) and ASV (Autogenous shrinking velocity); the higher HHV, the higher ASV and the greater ultimate Autogenous Shrinkage. The points where hydration temperature and Autogenous Shrinkage start to increase rapidly are due to the consumption of gypsum in the cement hydration process, and are strongly related to the setting time.
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Autogenous Shrinkage of concrete containing granulated blast-furnace slag
Cement and Concrete Research, 2006Co-Authors: Kyuri Lee, Hyun-yeul Lee, Sun-jung Lee, Gyuyong KimAbstract:Abstract This paper presents the experimental results and prediction model for the Autogenous Shrinkage of concrete made with various water-to-cementitious materials ratios ( w / cm) ranging from 0.27 to 0.42 and granulated blast-furnace slag (BFS) in the range of 0% to 50% by mass of the total cementitious materials. Test results showed that BFS concrete exhibited greater Autogenous Shrinkage than ordinary concrete with no BFS with the same w / cm, and that the higher the BFS content, the greater the Autogenous Shrinkage. At the same content of BFS, the increasing rate of Autogenous Shrinkage is affected by the w / cm; the lower the w / cm, the smaller the increasing rate of Autogenous Shrinkage. Based on the test results, a prediction model for Autogenous Shrinkage was proposed. In particular, an effective Autogenous Shrinkage that is a realistic Shrinkage strain responsible for stress development was introduced in the model. It was determined by taking into account the characteristics of ultrasonic pulse velocity evolution in concrete. This prediction method for Autogenous Shrinkage may be effectively used to estimate the stress induced by Autogenous Shrinkage.
Will Hansen - One of the best experts on this subject based on the ideXlab platform.
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Aggregate and slag cement effects on Autogenous Shrinkage in cementitious materials
Construction and Building Materials, 2016Co-Authors: Zhichao Liu, Will HansenAbstract:Abstract This study investigates the susceptibility of cementitious materials to internal moisture condition by the Autogenous deformation measurement in the 0.35 water-binder (w/b) ratio systems (paste, mortar and concrete). Autogenous Shrinkage is obtained by separating the thermal effects from the measured total deformation using the maturity concept and the coefficient of thermal deformation (CTD). Three factors affecting the Autogenous Shrinkage are presented, that is the aggregate content, the partial replacement of portland cement with slag cement and of normal weight fine aggregate with lightweight aggregate (LWA). Autogenous Shrinkage is clearly reduced by an increasing aggregate content and this effect is predicted by an improved Pickett’s model using a time-dependent aggregate restraining factor. A binary cementitious system of portland cement and slag cement increases the Autogenous Shrinkage in the long term. Contribution of slag cement can be characterized by the difference in Autogenous Shrinkage between the binary system and the control system scaled down by the replacement ratio. The negative effect of slag cement can be neutralized by the incorporation of LWA as a partial sand replacement.
