Modeling Drying Shrinkage Stress Gradients in Concrete

2004 ◽  
Vol 26 (2) ◽  
pp. 1-8 ◽  
Author(s):  
Zachary C. Grasley ◽  
David A. Lange
Keyword(s):  
Drying Shrinkage ◽  
Shrinkage Stress ◽  
Stress Gradients ◽  
Drying Shrinkage Stress

scholarly journals Evaluation of the Thermal and Shrinkage Stresses in Restrained High-Performance Concrete

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3680 ◽  
Author(s):  
Yang Yang ◽  
Linhao Ma ◽  
Jie Huang ◽  
Chunping Gu ◽  
Zhenjian Xu ◽  
...  
Keyword(s):  
Thermal Stress ◽  
High Performance ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Shrinkage Stress ◽  
Early Age ◽  
Volume Deformation ◽  
Curing Conditions ◽  
Drying Shrinkage Stress

The early age volume deformation is the main course for the cracking of high-performance concrete (HPC). Hence, the shrinkage behavior and the restrained stress development of HPC under different restraints and curing conditions were experimentally studied in this paper. The method to separate the stress components in the total restraint stress was proposed. The total restrained stress was separated into autogenous shrinkage stress, drying shrinkage stress and thermal stress. The results showed that the developments of the free shrinkage (autogenous shrinkage and drying shrinkage) and the restrained stress were accelerated when the drying began; but the age when the drying began did not significantly influence the long-term shrinkage and restrained stress of HPC; the autogenous shrinkage stress continuously contributed to the development of the total restrained stress in HPC; the drying shrinkage stress developed very rapidly soon after the drying began; and the thermal stress was generated when the temperature dropped. The thermal stress was predominant at the early age, but the contributions of the three stresses to the total restrained stress were almost the same at the age of 56 d in this study.

Research of Mechanical Properties of Concretes as Cement-Based Porous Materials

2012 ◽  
Vol 174-177 ◽  
pp. 322-325
Author(s):  
Ling Yun Meng
Keyword(s):  
Mechanical Properties ◽  
Relative Humidity ◽  
Water Pressure ◽  
Drying Shrinkage ◽  
Repulsive Force ◽  
Shrinkage Stress ◽  
Early Age ◽  
Capillary Water ◽  
Drying Shrinkage Stress ◽  
Over Time

Abstract: The concrete as a porous cement-based material is widely used in practice. The analysis of the basic reason why the drying shrinkage stress develops in concrete at early age is made by using the principal of the equilibrium between capillary water repulsive force and molecular attracting force. The model for computing the drying shrinkage stress for nonbinding concrete is presented by relating the capillary water pressure to relative humidity. Based on it ,the model for concrete fully restrained is given. The measurement of the drying shrinkage stress and depth of cracks caused by the drying shrinkage stress is made by using translation symmetric theorem and adopting dog-shaped specimens, and the analysis of changes in depth of cracks over time for two kinds of specimens is made. using the method of comparison ,the comparison of the gradient of the drying shrinkage stress for two kinds of specimens is made ,and it comes to the conclusion that the median drying shrinkage stress in the concrete fully restrained is higher in value by 1MPa compared to the drying shrinkage stress in non-restrained concrete

scholarly journals Experimental Study on the Shrinkage Behavior and Mechanical Properties of AAM Mortar Mixed with CSA Expansive Additive

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3312 ◽  
Author(s):  
Sung Choi ◽  
Gum-Sung Ryu ◽  
Kyeong-Taek Koh ◽  
Gi-Hong An ◽  
Hyeong-Yeol Kim
Keyword(s):  
Modulus Of Elasticity ◽  
Compensation Effect ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Shrinkage Stress ◽  
Calcium Sulfoaluminate ◽  
Total Shrinkage ◽  
Expansive Additive ◽  
Shrinkage Compensation

In this study, a calcium sulfoaluminate-based expansive additive (0%, 2.5%, 5.0%, and 7.5% by the mass of the binder) was added to compensate for the shrinkage of alkali-activated material (AAM) mortar. Modulus of elasticity curves based on the ACI 209 model were derived for the AAM mortar mixed with the additive by measuring the compressive strength and modulus of elasticity. Moreover, autogenous shrinkage and total shrinkage were measured for 150 days, and drying shrinkage was calculated by excluding autogenous shrinkage from total shrinkage. For the autogenous and drying shrinkage of AAM mortar, shrinkage curves by age were obtained by deriving material constants using the exponential function model. Finally, shrinkage stress was calculated using the modulus of elasticity of the AAM mortar and the curves obtained using the shrinkage model. The results showed that the calcium sulfoaluminate-based expansive additive had an excellent compensation effect on the drying shrinkage of AAM mortar, but the effect was observed only at early ages when the modulus of elasticity was low. From a long-term perspective, the shrinkage compensation effect was low when the modulus of elasticity was high, and thus, shrinkage stress could not be reduced.

Modified gach technique vs critical point drying: Shrinkage analysis for SEM

1987 ◽  
Vol 45 ◽  
pp. 954-955
Author(s):  
B. Thompson ◽  
N. Sculov ◽  
R.E. Crang
Keyword(s):  
Critical Point ◽  
Calf Serum ◽  
Drying Shrinkage ◽  
Specimen Preparation ◽  
Cell Shrinkage ◽  
Whole Cells ◽  
Critical Point Drying ◽  
Prepared Material ◽  
Inverted Microscope ◽  
Phosphate Buffered Saline

The use of co-polymerized glutaraldehyde-carbohydrazide (GACH) was proposed for specimen preparation in scanning electron microscopy (SEM) as a means of avoiding dehydration in organic solvents, and to provide dimensionally stable biological specimens through a process of air-drying. It has been assumed that shrinkage of specimens prepared by the GACH technique should be less than that of conventionally-prepared material by critical point drying (CPD). In a previous study, Bell has reported significant shrinkage of whole cells for SEM. This report compares cell shrinkage in GACH and CPD preparations.Fibroblasts from newborn rats were grown on collagen-coated glass cover-slips (with alpha numeric grids etched onto the surface of the coverslips) in Eagle's minimum essential medium + 10% fetal calf serum for 7 d. (3). Using an inverted microscope with phase-contrast optics, micrographs were taken of the cultures in their live state and 1 h. after fixation with 2.5% glutaraldehyde in Dulbecco's phosphate buffered saline (Figs. 1 and 3).

Environmental microscopy of capillary stress-induced strain behavior in ambient-pressure aerogels

1996 ◽  
Vol 54 ◽  
pp. 850-851
Author(s):  
Sudeep M. Rao ◽  
Joshua Samuel ◽  
Sai S. Prakash ◽  
C. Jeffrey Brinker
Keyword(s):  
Silica Aerogel ◽  
Ambient Pressure ◽  
Drying Shrinkage ◽  
Pore Filling ◽  
Silica Network ◽  
Strain Behavior ◽  
Partially Saturated ◽  
Capillary Stress ◽  
Wetting Liquid ◽  
Aerogel Films

Ambient pressure silica aerogel thin films have recently been prepared by exploiting reversible drying shrinkage caused by derivatization of the internal gel surface. Aerogels have porosities of upto 99.9% and due to the small size of the pores (few nanometers), large capillary stresses are produced in gels that are partially saturated with a wetting liquid. As a result of these capillary stresses, the flexible silica network undergoes strain which has been observed using environmental microscopy. This technique allows variation of the equilibrium vapor pressure and temperature, and a simultaneous monitoring of the deformation of the unconstrained film thickness. We have observed >600% deformation during the pore-filling and pore-emptying cycles. In this presentation, we discuss the unique stress-strain behavior of these films.Ref.: Sai S. Prakash, C. Jeffrey Brinker, Alan J. Hurd & Sudeep M. Rao, "Silica aerogel films prepared at ambient pressure by using surface derivatization to induce reversible drying shrinkage", Nature. Vol. 374, 30 March, 1995, 439-443.

Standardization and bacteria inhibitory test of purified extract of mahogany (Swietenia mahagoni (L.) Jacq) seeds and leaves

2019 ◽  
Vol 10 (3) ◽  
pp. 2132-2138
Author(s):  
Virsa Handayani ◽  
Rezki Amriati Syarif ◽  
Ahmad Najib ◽  
Aktsar Roskiana Ahmad ◽  
Abdullah Mahmud ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Heavy Metal ◽  
Bitter Taste ◽  
Drying Shrinkage ◽  
Ash Content ◽  
Water Soluble ◽  
Lead Contamination ◽  
Specific Parameter ◽  
Chemical Content ◽  
Swietenia Mahagoni

Mahogany (Swietenia mahagoni (L.) Jacq) is one of the plants that is often used by the community as traditional medicine. One of them is antifungal, antibacterial, antidiabetic, and eczema. This study aims to obtain standardized extracts from mahogany seeds and leaves. Standardization of purified extract of mahogany has been carried out according to the monographs of extract standardization guidelines, which include testing of specific and non-specific parameters. The results of the specific parameter testing showed that the purified extract of mahogany seeds is a thick extract, brown to reddish, smells distinctive and has a bitter taste. While the purified extract of mahogany leaves is a thick extract, greenish-brown in color, distinctive smell and has a bitter taste. The chemical content of purified extract of mahogany seeds and leaves showed the presence of flavonoids, alkaloids, terpenoids and saponins. Water-soluble essence levels in mahogany seeds and leaves was 14.84% and 10.28%. While the ethanol-soluble essence levels in mahogany seeds and leaves were 15.38% and 12.43%. Testing of non-specific parameters on mahogany seeds and leaves showed the results of drying shrinkage levels of 0.22% and 8.84%, moisture content of 2.60% and 4.04%, total ash content of 1.71% and 1.93%, levels acidic insoluble ash 0.38% and 0.32%, Total Plate Number (ALT) of mahogany seed bacteria 1x102 colonies/g, Number of mahogany mold seeds 4x10 colonies/g, heavy metal lead contamination and cadmium in mahogany seeds 0.0607µg/g and<0.003µg/g. The inhibitory diameter of each concentration of seeds against Escherichia coli, 3%, 5%, 7%, and 9%, is 12,67; 13,67; 17,67; and 19,67 mm, respectively. The inhibitory diameter of each concentration of leaves against Escherichia coli, 3%, 5%, 7%, and 9%, is 10,27; 10,90; 13,46; and 15,68 mm, respectively.

Drying Shrinkage on Payday

2018 ◽  
Vol 56 (4) ◽  
pp. 354-354
Author(s):  
T. Hasegawa
Keyword(s):  
Drying Shrinkage
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