• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.11a
• /
• pp.417-420
• /
• 2003

Concrete with low water to binder ratio (W/B) is prone to large autogenous shrinkage. Early age cracking of concrete would be caused by tensile stress induced by large autogenous shrinkage under restrained condition. Therefore, it is necessary to measure autogenous shrinkage to control the early age cracking of concrete. An objective of this study is to investigate the effects of W/B and blast furnace slag (BFS) on autogenous shrinkage of concrete. Autogenous shrinkage of concrete with various W/B ranging from 0.42 to 0.27 and BFS contents of 0, 30 and 50% were measured. Test results show that the autogenous shrinkage of concrete increases as the W/B decreases, and all BFS concretes showed larger autogenous shrinkage than OPC concretes with the same W/B. Moreover, the higher BFS content, the larger autogenous shrinkage.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.915-918
• /
• 2008

Hydration heat and autogenous shrinkage are generated essentially by the same hydration. Many researchers have studied the close relationship between hydration temperature and autogenous shrinkage but hardly any research has been undertaken to explain the specific numerical relation. In this study, early age properties of hydration heat and autogenous shrinkage of specimen whose section size was changed were analyzed, and relationship between hydration heat and autogenous shrinkage was investigated. In the results of the study, inner temperature and autogenous shrinkage increased as the section size increased. And rise and rise ratio of hydration temperature and autogenous shrinkage in hydration heating section and autogenous shrinking section are increased too. Temperature rise and autogenous shrinkage rise increased respectively, as hydration heating velocity and autogenous shrinking velocity increased. And autogenous shrinkage rise and autogenous shrinking velocity increased as hydration heating velocity increased.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.10 no.3
• /
• pp.97-105
• /
• 2006

The autogenous shrinkage of high-performance concrete is important in that it can lead the early cracks in concrete structures. The purpose of the present study is to explore the autogenous shrinkage of high-performance concrete with admixture and to derive a realistic equation to estimate the autogenous shrinkage model of that. For this purpose, comprehensive experimental program has been set up to observe the autogenous shrinkage for various test series. Major test variables were the type and contents of admixture and water-cement ratio is fixed with 30%. The autogenous shrinkage of HPC with fly ash slightly decreased than that of OPC concrete, but the use of blast furnace slag increased the autogenous shrinkage. Also, the autogenous shrinkage of HPC is found to decrease with increasing shrinkage reduction agent and expansive additive. A prediction equation to estimate the autogenous shrinkage of HPC with admixture was derived and proposed in this study. The proposed equation show reasonably good correlation with test data on autogenous shrinkage of HPC with mineral and chemical admixture.

• Journal of the Korea Concrete Institute
• /
• v.17 no.5 s.89
• /
• pp.853-856
• /
• 2005

A low water/cement ratio leads to autogenous shrinkage of cement paste at an early age. This autogenous shrinkage is related to the change of relative humidity in the pore structure that is formed during the hydration process. The relationship between autogenous shrinkage and relative humidity change are relatively well defined today, but the effects of temperature on autogenous shrinkage, relative humidity, and pore structures have been studied less systematically. This study focused on correlating alterations of these properties of cement paste hydrated at constant temperatures of 20, 40, and $60^{\circ}C$. The test results clearly indicate that increasing curing temperature resulted in increased porosity, particularly for pores between 5 to 50 nm as measured by MIP, and increased autogenous shrinkages, as a consequence of a reduction of relative humidity at early ages.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.95-100
• /
• 2003

The shrinkage of high strength/high performance concrete is very important property for the good working of a structure since it very often generates early age cracking due to thermal and autogenous shrinkage. Autogenous shrinkage occurs as a result of internal moisture depletion due to hydration and temperature-induced effects. The level of autogenous shrinkage occurring due to hydration also depends on temperature history at very early age. It is necessary that effect of temperature on autogenous shrinkage is investigated since the stress generated due to autogenous shrinkage is quantified. In this study, Effect of hydration heat evolution on autogenous shrinkage of high strength concretes with W/C=25-40% was investigated.

• Journal of the Korea Institute of Building Construction
• /
• v.11 no.6
• /
• pp.538-546
• /
• 2011

This paper is to experimentally investigate the strength and autogenous shrinkage of high strength mortar with the 20 % of water?binder ratio(W/B). In this study, the water substituting liquid(WSL) was used including gasoline, light oil, lamp oil, edible oil, HFE, ethanol, methanol and acetone in order to explore changes in strength and autogenous shrinkage depending on WSL type and replacement. For fresh properties, the replacement of WSL did not affect the fluidity of mortar mixtures considerably, except for ethanol and methanol. However, the replacement of WSL resulted in a slight decrease in flexural and compressive strength. For autogenous shrinkage, the replacement of WSL led to reduce autogenous shrinkage, and especially, the replacement of edible oil led to reduce autogenous shrinkage significantly due to saponification between edible oil and cement.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.101-106
• /
• 2003

This study is to capture autogenous shrinkage in reinforced concrete. The experiment was carried out on total 13 beams. The experiment parameters are a method of curing and reinforcement ratio. Autogenous shrinkage in reinforced concrete beam was experimentally measured. Also, the distribution of autogenous shrinkage and self stress on cross section in reinforced concrete beams were calculated. The experimental results showed that autogenous shrinkage of high strength concrete were significantly higher than that of nomal strength concrete.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.10a
• /
• pp.385-390
• /
• 2002

Autogenous shrinkage of concrete has been defined as decrease in volume due to hydration cement, not due to other causes such as evaporation, temperature change and external load and so on. For ordinary concretes, autogenous shrinkage is so little compared to the other deformations that it has been dignored. It has recently been proved, however, that autogenous shrinkage considerably increase with decrease in water to cement ratio. And it has been reported that cracking can be caused by autogenous shrinkage, when high- strength concretes were used. In this study, we propose an analytical system to represent autogenous shrinkage in cement paste in order to control crack due to autogenous shrinkage. The system is composed with the hydration model and pore structure model. Contrary to the usual assumption of uniform properties in the hydration progress, the hydration model to refine Tomosawa's represents the situation that inner and outer products are made in cement paste. The pore structure model is based upon the physical phenomenon of ion diffusion in cement paste and chemical phenomenon of hydration in cement particle. The proposed model can predict the pore volume ratio and the pore structure in cement paste under variable environmental conditions satisfactorily The autogenous shrinkage prdiction system with regard to pore structure development and hydration at early ages for different mix-proportions shows a reasonable agreement with the experimental data.

• Archives of Plastic Surgery
• /
• v.38 no.3
• /
• pp.222-227
• /
• 2011

Purpose: Autogenous particulate bone grafting is a type of autogenous bone graft that consists of small particles of cortical and cancellous bone. Autogenous particulate bone grafting has been used for calvarial bone defect after calvarial defect of craniosynostosis and prevention of temporal depression after fronto-orbital advancement. The results were followed up and studied for effectiveness of autogenous calvarial particulate bone grafting. Methods: Cranial vault remodeling and fronto-orbital advancement was performed for six craniosynostosis patient from August 2005 to October 2007. Autogenous particulate bone grafting was harvested from endocortex of separated cranial vault and if insufficient, from extocortex of occipital region using Hudson brace & D'Errico craniotomy bit and was grafted on the calvarial bone defect of cranial vault and temporal hollow. Fibrin glues were added to the harvested particulated bone for adherence and shaping of paticles. Results: Autogenous particulate bone grafting was followed-up at least longer than I year. The calvarial bony defects following primary cranial remodeling were successfully covered and postoperative temporal depressions after fronto-orbital advancement were also well prevented by grafted particulated bone. Conclusion: Autogenous calvarial particulate bone graft can be harvested in infants and young children with minimal donor site morbidity. It effectively heals cranial defects in children and during fronto-orbital advancement reduces the prevalence of osseous defects independent of patient age. It's easy and effective method of reconstruction of calvarial defect.

• Structural Engineering and Mechanics
• /
• v.49 no.6
• /
• pp.763-773
• /
• 2014

The recently developed Ultra High Performance Concrete (UHPC) displays outstanding compressive strength and ductility but is also subjected to very large autogenous shrinkage. In addition, the use of forms and reinforcement to confine this autogenous shrinkage increases the risk of shrinkage cracking. Accordingly, this study adopts a combination of shrinkage reducing admixture and expansive admixture as a solution to reduce the shrinkage of UHPC and estimates its appropriateness by evaluating the compressive and flexural strengths as well as the autogenous shrinkage according to the age. Moreover, the coefficient of thermal expansion known to experience sudden variations at early age is measured in order to evaluate exactly the autogenous shrinkage and the thermal expansion is compensated considering these measurements. The experimental results show that the compressive and flexural strengths decreased slightly at early age when mixing 7.5% of expansive admixture and 1% of shrinkage reducing admixture but that this decrease becomes insignificant after 7 days. The use of expansive admixture tended to premature the setting of UHPC and the start of sudden increase of autogenous shrinkage. Finally, the combined use of shrinkage reducing admixture and expansive admixture appeared to reduce effectively the autogenous shrinkage by about 47% at 15 days.