scholarly journals Setting Mechanism of a CDHA Forming α-TCP Cement Modified with Sodium Phytate for Improved Injectability

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2098 ◽  
Author(s):  
Jan Weichhold ◽  
Uwe Gbureck ◽  
Friedlinde Goetz-Neunhoeffer ◽  
Katrin Hurle
Keyword(s):  
Cement Paste ◽  
Weight Ratio ◽  
Octacalcium Phosphate ◽  
Effect Of Temperature ◽  
Sodium Phytate ◽  
Setting Reaction ◽  
Fine Grained ◽  
Setting Mechanism ◽  
Paste Viscosity ◽  
Powder Content

A calcium deficient hydroxyapatite (CDHA) forming cement with a bimodal grain size distribution, composed of α-TCP and fine grained CDHA at a weight ratio of 9:1, was modified by the addition of sodium phytate (IP6) in variable amounts ranging from 0.25 to 2 wt.%, related to the powder content. The injectability of the cement paste was drastically increased by the IP6 addition, independent of the amount of added IP6. Additionally, the cement paste viscosity during the first minutes decreased. These effects could be clearly related to a slightly more negative zeta potential. Furthermore, IP6 was shown to strongly retard the setting reaction, as can be seen both in the calorimetry and X-ray diffraction measurements. In addition, octacalcium phosphate (OCP) was identified as a further setting product. All measurements were performed at 23 °C and 37 °C to assess the effect of temperature on the setting reaction for both clinical handling by the surgeon and the final hardening in the bone defect.

The biology of Cucumaria elongata (Echinodermata: Holothuroidea)

1967 ◽  
Vol 47 (1) ◽  
pp. 129-144 ◽  
Author(s):  
John D. Fish
Keyword(s):  
Feeding Behaviour ◽  
Age Groups ◽  
Weight Ratio ◽  
Dry Weight ◽  
Effect Of Temperature ◽  
Group I ◽  
Group A ◽  
Group B ◽  
Slow Growing

A population of Cucumaria elongata (Düb & Kor.), found in muddy sand off the Northumberland coast, has been sampled from 1961 to 1964. Densities of more than 20 per m were common.Cucumaria is a suspension feeder, and uses its tentacles to trap suspended paniculate matter. In the absence of mucous glands or cilia on the tentacles, suspended matter is held fast in a covering of mucus which is produced by glands in the pharynx and oesophagus. Each time the tentacles are introduced into the pharangeal lumen in the course of feeding, they pick up a fresh complement of mucus.The feeding behaviour is seasonal. During the early part of October the animals stop feeding, and remain dormant until late April/early May of the following year.The results of monthly experiments to determine the oxygen consumption, percentage of total lipid and the volume/dry-weight ratio, have led to the conclusion that during the winter months Cucumaria hibernates.The effect of temperature on the feeding behaviour is discussed.Regular quantitative sampling has shown that Cucumaria is slow growing, and over the area surveyed, four different age-groups were found. These have been designated groups I, A, B and C. Group I was estimated to be 2 years old; group A, 6 six years; group B, 8 years; and group C, 10 years old.Although active sperm and apparently mature eggs were found in specimens collected as far back as 1962, there is no evidence to suggest that any of the age-groups has reproduced.

Effect of temperature on the cavity nucleation rate for fine-grained Zn–22wt.% Al alloy

2008 ◽  
Vol 58 (8) ◽  
pp. 643-646 ◽  
Author(s):  
Tsutomu Tanaka ◽  
Yorinobu Takigawa ◽  
Kenji Higashi
Keyword(s):  
Nucleation Rate ◽  
Effect Of Temperature ◽  
Al Alloy ◽  
Cavity Nucleation ◽  
Fine Grained

scholarly journals Green degumming process of ramie fiber thermal effect and optimization

2019 ◽  
Vol 23 (4) ◽  
pp. 2447-2451 ◽  
Author(s):  
Guoliang Liu ◽  
Dan Tian ◽  
Bangze Zhou ◽  
Yumeng Zhang ◽  
Tao Xu ◽  
...  
Keyword(s):  
Natural Fibers ◽  
Weight Ratio ◽  
Raw Material ◽  
Effect Of Temperature ◽  
Ramie Fiber ◽  
Traditional Treatment ◽  
Sodium Percarbonate ◽  
Ramie Fibers ◽  
Degumming Process ◽  
Environmentally Friendly Process

Ramie is a kind of natural fibers, it requires degumming process before it can be used as a raw material for various applications. The traditional treatment uses alkali, which is not an environmentally friendly process. In this paper, ramie fibers are degummed using sodium percarbonate, which causes no any negative environmental problems, and its decomposition, hydrogen peroxide, is a clear liquid, it can be used as an oxidizer, bleaching agent and antiseptics for surface treatment of ramie fibers. Effect of temperature and concentration of sodium percarbonate on the degumming process are studied theoretically and verified experimentally. Finally an optimal degumming process is suggested for maximal weight ratio of degummed ramie fiber to raw bast.

scholarly journals INFLUENCE OF THE TYPE OF WATER ACTIVATION ON THE CONTACT ZONE BETWEEN THE FILLER AND THE CEMENT STONE

2021 ◽  
pp. 16-25
Author(s):  
Alexandra Shyshkina ◽  
Alexandеr Shyshkin
Keyword(s):  
Cement Paste ◽  
Chemical Activation ◽  
High Rate ◽  
Cement Stone ◽  
Normal Density ◽  
Alkaline Water ◽  
Fine Grained ◽  
Low Concentrations ◽  
Water Activation ◽  
The Many

Among the many ways to improve the preparation of concrete mix is to modify the properties of cement systems by mechanical, physical, chemical and combined effects. One of the directions of activation of the concrete mixture is the activation of its components, namely: electromagnetic, electrochemical and physics-chemical activation of mixing water. The most accessible and technological of them is the physics-chemical activation of water and aqueous solutions by certain organic substances used in ultra-low concentrations, followed by their use as a mixing fluid for building mixtures. The purpose of the study was to perform a comparative assessment of the effect of electromagnetic, electrochemical and physicochemical activation of water on the properties of cement paste and fine-grained concrete. To achieve this goal, the degree of influence ofelectromagnetic, electrochemical and physicochemical activation of water on the contraction and hardening time of cement paste, as well as the degree of influence of electromagnetic, electrochemical and physicochemical activation of water on compressive strength of fine concrete. It is established that the type of activation of kneading water affects the hardening time of the cement paste and the normal density. The shortest hardening times are set for cement paste, which is obtained on electrochemically activated alkaline water, and the longest with the use of physics-chemical activation. At the same time, the highest strength at the lowest contraction has concrete, which is obtained on physics-chemical activated water. This concrete has the highest rate of strength. Concretes obtained on «alkaline» water, after its electro-chemical activation, have a high rate of strength formation and its value, but high contraction, which leads to cracking of concrete.

Observations on brucite formation and the role of brucite in Iowa highway concrete deterioration

2002 ◽  
Vol 8 (2) ◽  
pp. 137-145 ◽  
Author(s):  
Hyomin Lee ◽  
Robert D. Cody ◽  
Anita M. Cody ◽  
Paul G. Spry
Keyword(s):  
Cement Paste ◽  
Direct Evidence ◽  
Crystal Surface ◽  
Conclusive Evidence ◽  
Coarse Grained ◽  
Fine Grained ◽  
Coarse Aggregates ◽  
Concrete Deterioration ◽  
Direct Precipitation

Abstract Iowa highway concretes containing reactive dolomite, (CaMg) 2 CO 3 , aggregate, composed of fine-grained, microporous dolomite, sometimes have service lives of less than 10 years. This premature deterioration may, in part, be caused by expansive forces created by newly formed minerals such as brucite, Mg (OH) 2 , in the cement paste as a result of dedolomitization of reactive dolomite coarse aggregate. Although calcite is the most abundant secondary mineral in cements of poorly-performing concretes, the present study found no evidence that it was expansionary. Brucite is common but less abundant than calcite and occurred chiefly in and near the margins of reactive dolomite in both the aggregate and cement paste of poorly-performing concretes. Most brucite occurs in partially dedolomitized rims around dolomite coarse aggregates. This type of brucite is widely disseminated through the rims, consists of extremely small (<1 m) microcrystalline masses, and was produced by direct precipitation from pore solutions. Smaller amounts of brucite occur in the cement paste. This type is relatively coarse-grained (10 mu m-20 mu m) and most was formed primarily by crystal surface mediated (topochemical) reactions between magnesium-rich pore solutions and portlandite, Ca(OH) 2 . Numerous microcracks are present in cement paste but are not spatially associated with brucite locations. There is no direct evidence for cracking caused by brucite but this is not conclusive evidence against brucite-induced expansion. Brucite is widely disseminated so that expansion at innumerable micro-locations may cause general concrete expansion which should be relieved by cracking at weaker locations in the concretes.

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