AAC 5.1 Determination of drying shrinkage of AAC

1994 ◽  
pp. 349-355
Keyword(s):  
Drying Shrinkage

scholarly journals The effect of fibers on the loss of water by evaporation and shrinkage of concrete

2015 ◽  
Vol 8 (1) ◽  
pp. 8-13 ◽  
Author(s):  
N. M. P. Pillar ◽  
W. L. Repette
Keyword(s):  
Mechanical Damage ◽  
Drying Shrinkage ◽  
Fiber Reinforced Concrete ◽  
Plastic State ◽  
Limited Effect ◽  
Plastic Shrinkage ◽  
Loss Of Weight ◽  
Threshold Strength ◽  
Compressive Tests

Shrinkage is one of the least desirable attributes in concrete. Large areas of exposed concrete surfaces , such as in shotcrete tunnel linings, where it is practically impossible to make a moist cure, are highly susceptible to plastic shrinkage at early ages. The autogenous and drying shrinkage can lead to states of greater than threshold strength, causing fracture, mechanical damage and lack of durability of concrete structures. The addition of fibers can greatly reduce plastic shrinkage, but has limited effect in mitigating autogenous and drying shrinkage. To evaluate the performance of polypropylene and steel fibers to understand their effect on shrinkage of concrete, a study was carried out to relate the loss of water from the paste and the shrinkage during the first 28 days of age, and compare it with a control mix without fiber. The loss of water was obtained by the weight loss of the specimens at different ages, since the only component that could contribute for the loss of weight was the water lost by the paste of the concrete. And the paste itself is the only source of shrinkage. Uniaxial compressive tests from very early ages enabled the determination of time when plastic shrinkage ended. It was observed that the control concrete mix lost three times more water and developed plastic and drying shrinkage 60 % higher than the fiber reinforced concrete mixes. It was possible to demonstrate that the reduced loss of water caused by the incorporation of fibers is related to the mitigation of plastic shrinkage. It was observed that the fibers are effective to restrain the movement of water through the cement paste in the plastic state, however such effect is limited after concrete starts the hardening state.

Analysis of Concrete Early-Age Shrinkage Based on the Theory of Humidity Diffusion

2011 ◽  
Vol 462-463 ◽  
pp. 183-187 ◽  
Author(s):  
Yun Feng Li ◽  
Rong Qiang Du ◽  
Fan Ying Kong
Keyword(s):  
Cement Content ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Analytical Models ◽  
Early Age ◽  
Free Shrinkage ◽  
Shrinkage Cracking ◽  
Binder Ratio ◽  
Water Binder Ratio

The early-age shrinkage cracking of concrete plays an important role to the accelerated deterioration and shortening the service life of concrete structures. Modern concretes are more sensitive to cracking immediately after setting, which is due to material characteristics (lower water/binder ratio and higher cement content) and external environmental fluctuations (humidity and temperature change). Determination of concrete free shrinkage is the basis of shrinkage cracking research. Analytical models of the autogenous shrinkage and drying shrinkage are established in this paper. The calculated results agree well with the experimental results.

scholarly journals STANDARDISASI EKSTRAK ETANOL 96% BULU BABI Echinometra mathaei DARI PERAIRAN BANGKALAN

2021 ◽  
Vol 2 (1) ◽  
pp. 21
Author(s):  
Angelica Kresnamurti ◽  
Farizah Izazi ◽  
Dwi Kurniawati
Keyword(s):  
Sea Urchin ◽  
Heavy Metal Contamination ◽  
Sea Urchins ◽  
Medicinal Preparation ◽  
Drying Shrinkage ◽  
Ethanol Extract ◽  
Chemical Content ◽  
Echinometra Mathaei

Echinometra mathaei sea urchins are known to contain chemical compounds that can be used to overcome health problems, one of which has antioxidant activity. Some previous studies have explained the benefits of sea urchins but to ensure the quality assurance of sea urchins extracts, efforts should be made to determine the quality standards of sea urchins extract. This study aims to standardize specific parameters and non-specific parameters on Echinometra mathaei sea urchins extract to ensure the quality of 96% ethanol extract. Samples were obtained from Rongkang Beach, Kwanyar District, Bangkalan District, Madura which were then extracted using maceration method with 96% ethanol solvent. The results of the study for specific parameters showed that organoleptically and macroscopically the extracts were thick, blackish brown in color and characteristic of sea urchins; levels of dissolved compounds in ethanol of 78.37%; levels of dissolved compounds in water of 93.09%; and chemical content tests showed that the extract contained steroid compounds, tannins, flavonoids, saponins, alkaloids and terpenoids. Determination of non-specific parameters showed that Echinometra mathaei sea urchin extract had a drying shrinkage of 3.03%; specific gravity of 0.8411 g/mL; water content of 5.32%; Pb heavy metal contamination was 7.28 mg/kg, Cd was <0.0024 mg/kg, Hg was <0.0002 mg / kg, Mg was 347.83 mg / kg; microbial contamination of <10 colonies / mL; and yeast mold contamination of <10 colonies/mL. The conclusion is Echinometra mathaei sea urchin extract has the potential to be developed into a medicinal preparation. Key word: Echinometra mathaei, Specific standardize parameters, non-specific standardize parameters, Extract thanol 96%.

scholarly journals Penentuan Kadar Senyawa Aktif Cyanocobalamine Menggunakan Metode Spektrofotometri UV-VIS

2020 ◽  
Vol 1 (1) ◽  
pp. 32
Author(s):  
Risma Sari ◽  
Aisyah Salma Billa
Keyword(s):  
Vitamin B12 ◽  
Spectrophotometric Method ◽  
Active Compound ◽  
Drying Shrinkage ◽  
Average Level ◽  
Hot Plate ◽  
Water Solvent ◽  
Test Parameters

Cyanocobalmine is vitamin B12 which is widely used to treat or prevent deficiency (deficiency of vitamins) in various types of preparations. Cyanocobalmine in the 5th edition of Indonesian Pharmacopoeia literature can determine by UV-Vis Spectrophotometric method with water solvent. The purpose of this testing was to determine whether the levels of the active compound Cyanocobalamine from the 3 test parameters. In the description test where the sample tested is the same as the Cyanocobalamine specification, namely, crystal powder is dark red. Hot plate was used to determine drying shrinkage. Shrink drying was 2.25% - 2.75% from the ≤ 12% requirement. The determination of the levels of the active compound of Cyanocobalamine fulfills the requirements, namely 96% - 102.0%. The results of the assay showed that the average level of Cyanocobalamine from 4 samples was 96.02%, which met the standards set by the Pharmacopeia. Indonesia Edition V as a requirement for determining the levels of the active compound Cyanocobalamine.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

International determination of the total motion of the pole

1961 ◽  
Vol 13 ◽  
pp. 29-41
Author(s):  
Wm. Markowitz
Keyword(s):  
Secular Motion ◽  
The Future

A symposium on the future of the International Latitude Service (I. L. S.) is to be held in Helsinki in July 1960. My report for the symposium consists of two parts. Part I, denoded (Mk I) was published [1] earlier in 1960 under the title “Latitude and Longitude, and the Secular Motion of the Pole”. Part II is the present paper, denoded (Mk II).

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