scholarly journals Pore Filling Effect of Forced Carbonation Reactions Using Carbon Dioxide Nanobubbles

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4343
Author(s):  
Jihoon Kim ◽  
Ryoma Kitagaki ◽  
Heesup Choi
Keyword(s):  
Carbon Dioxide ◽  
Aqueous Solution ◽  
Surface Modification ◽  
Calcium Carbonate ◽  
Pore Filling ◽  
Concrete Repair ◽  
Mortar Specimen ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Series Of Experiments

Various methods for repairing and modifying concrete surfaces have been proposed and applied to improve the durability of existing concrete structures. Surface modification through forced carbonation is a method of densification that forms calcium carbonate in the pores on the surface of concrete to improve its durability. In this study, to evaluate the applicability of this surface modification method to existing buildings, a series of experiments was conducted in which mortar specimens were repeatedly immersed in a carbon dioxide nanobubble aqueous solution. By evaluating the weight change and absorption rate, it was determined that the higher the water/cement ratio of the mortar specimen, the higher the pore filling effect owing to immersion in the carbon dioxide nanobubble aqueous solution. In addition, the effect of clogged pores generated by the precipitation of calcium carbonate was confirmed, and it was found that the higher the water/cement ratio of the mortar specimen, the higher the pore filling effect due to clogging. We believe that our findings contribute to the development of research and construction practices associated with concrete repair and restoration.

scholarly journals The Influence of Finely Ground Mineral Admixture (FGMA) on Efflorescence

2013 ◽  
Vol 4 (1) ◽  
pp. 50-55 ◽  
Author(s):  
Ong Ming Wei ◽  
Norsuzailina Mohamed Sutan
Keyword(s):  
Calcium Carbonate ◽  
Chemical Analysis ◽  
Mineral Admixture ◽  
Partial Replacement ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Cement Replacement ◽  
Carbonate Formation

Efflorescence phenomenon on concrete is not new and found in the form of white deposits on surfaces of concrete. Incorporation of Finely Ground Mineral Admixture (FGMA) in concrete to prevent occurrence of efflorescence is based on reduction of portlandite, densified microstructure and thus enhanced watertightness. The magnitude of efflorescence in term of percentage of calcium carbonate formation of FGMA modified mortar were evaluated at water-cement ratio of 0.3, 0.4 and 0.5 with 10%, 20%, and 30% of cement replacement by weight. The samples were tested with chemical analysis at 7, 14, 21, 28, 60 and 90 days. The FGMA additions into mortar were comparing with ordinary mortar to evaluate enhanced performance of FGMA modified mortar toward efflorescence. The results of this experiment showed that addition of FGMA into mortar caused less formation of calcium carbonate as partial replacement of cement with certain w/c ratio and percentage of cement replacement.

Preliminary Study on Reaction of Fresh Concrete with Carbon Dioxide

2018 ◽  
Vol 382 ◽  
pp. 230-234
Author(s):  
Ming Ju Lee ◽  
Ming Gin Lee ◽  
Yung Chih Wang ◽  
Yu Min Su ◽  
Jia Lun Deng
Keyword(s):  
Carbon Dioxide ◽  
Compressive Strength ◽  
Fresh Concrete ◽  
Setting Time ◽  
Cement Matrix ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Short Time

In order to let fresh concrete react with carbon dioxide sufficiently, the carbon dioxide was added to mixing concrete. The study used three water cement ratio (0.55, 0.65, 0.75), three CO2 pressures (0.2, 0.4, 0.6 MPa), and two CO2 concentration (50% and 100%) to make concrete samples, and observed the effect of carbon dioxide adsorption in the above parameters. Finally, the compressive strength and carbonation degree of concretes were tested after three curing time (7, 14 and 28 days). The research showed that concrete could be more efficient to absorb carbon dioxide by using this pressure method. The results found that the mixing concrete react with carbon dioxide in a short time, and shorten the initial setting time of concrete. But this method would greatly reduce the workability of concrete after mixing with carbon dioxide and it might be enhanced by water or superplasticizer. The bond of cement matrix might cut down after reacting with carbon dioxide. Based on the above, the compressive strength of concrete which was mixed with carbon dioxide would be impaired. The proposed CO2-mixing method has the capacity to uptake 9.5% carbon dioxide based on water cement ratio and CO2 pressure.

Effect of dressings of basic slag on the lime status of soils

1926 ◽  
Vol 16 (2) ◽  
pp. 196-204 ◽  
Author(s):  
Rice Williams
Keyword(s):  
Carbon Dioxide ◽  
Aqueous Solution ◽  
Calcium Carbonate ◽  
Unsaturated Soils ◽  
Degree Of Saturation ◽  
Low Grade ◽  
Basic Slag ◽  
Exchangeable Calcium ◽  
Laboratory Conditions ◽  
Experimental Plots

(1) The addition of basic slag to moist base-unsaturated soils, under laboratory conditions, causes an increase in their content of exchangeable calcium, degree of saturation, pH, and the amount of calcium soluble in an aqueous solution of carbon dioxide.(2) Slag seems to be almost as effective as calcium carbonate or lime in increasing the exchangeable calcium and the degree of saturation of soils, but its action on pH is not so marked.(3) The effect of dressings of slag on the lime status of soils from experimental plots is still evident after eight years.(4) The exchangeable calcium of samples of soil taken from the same fields after an interval of six years shows a considerable fall due to leaching.(5) It is suggested that the addition of low grade basic slag to unsaturated soils may tend to maintain or improve their lime status and will, to some extent, compensate for the loss of calcium due to drainage and crops.

Experimental Study on Application Properties of Macroporous Ecological Concrete without Sand

2011 ◽  
Vol 250-253 ◽  
pp. 901-905
Author(s):  
Zhen Xian Xing ◽  
Yi Xing
Keyword(s):  
Experimental Study ◽  
Erosion Resistance ◽  
Necessary Conditions ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Coarse Aggregates ◽  
Effect Of Water ◽  
Resistance Property ◽  
Mix Proportion ◽  
Series Of Experiments

This paper suggests that deposition paste area is one of those leading control indicators of mix proportion design for the macroporous ecological concrete without sand. By analyzing the effect of water-cement ratio, amount of cement, and type of coarse aggregates on application properties of concrete, it puts forward that when carrying out the mix proportion design of the concrete, setting the water-cement ratio as 0.4 can help the macroporous ecological concrete without sand acquire satisfying application properties. Based on this idea, experiments to the later period strengths and the erosion resistance property of concretes are tried out. Finally, the result of this series of experiments shows that the macroporous ecological concrete without sand possesses necessary conditions for plants to survive and grow up.

scholarly journals Preparation of Magnesium Phosphate Cement and Application in Concrete Repair

2018 ◽  
Vol 142 ◽  
pp. 02007 ◽  
Author(s):  
Sainan Xing ◽  
Chengyou Wu
Keyword(s):  
Magnesium Oxide ◽  
Calcination Temperature ◽  
Bonding Strength ◽  
Potassium Phosphate ◽  
Magnesium Phosphate ◽  
Dihydrogen Phosphate ◽  
Concrete Repair ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Potassium Magnesium

Potassium magnesium phosphate cement (MKPC) was prepared by using magnesium oxide (MgO) and potassium dihydrogen phosphate (KH2PO4, KDP). The effects of different calcination temperature, water-cement ratio and ratio on the operation of magnesium phosphate cement were studied. The effects of different water - cement ratio and ratio on the bonding strength of potassium magnesium phosphate cement and the application of potassium phosphate and magnesium cement in concrete repair and reinforcement were determined by experiments such as bending resistance, splitting, compression and bearing capacity. The experimental results show that the calcination temperature is 1100 °C, the calcination time is 1h, the settling time of magnesium oxide is 39min, and the compressive strength of one day reaches 53MPa. The water - cement ratio with the best bonding strength is 0.2, the mass ratio is 2:1.To meet the rapid repair of the construction requirements, is expected to be applied to the actual repair works.

scholarly journals The Function of the Calciferous Glands of Earthworms

1936 ◽  
Vol 13 (3) ◽  
pp. 279-297
Author(s):  
JAMES D. ROBERTSON
Keyword(s):  
Carbon Dioxide ◽  
Calcium Carbonate ◽  
Lumbricus Terrestris ◽  
Ion Concentration ◽  
Isolated Cells ◽  
Hydrogen Ion Concentration ◽  
Feeding Experiments ◽  
Series Of Experiments ◽  
The Common ◽  
Metabolic Carbon

1. In the Lumbricidae the secretion of the calciferous glands consists mainly of calcium carbonate, the percentage of carbonate in the calcite concretions being 95-97 per cent. 2. Feeding experiments indicate that the calcium of the secretion can be derived from the common inorganic salts such as the carbonate, sulphate, phosphate, oxalate, chloride, and nitrate, and also from pear leaves. 3. Measurements of the hydrogen-ion concentration of the gut, soil, and castings of specimens of Lumbricus terrestris show that the tendency of the cast to be more neutral than the soil is due to the secretions of the gut as a whole, and not to the secretion of the calciferous glands. 4. The optimum pH's of two of the main intestinal enzymes have been measured. Amylase has an optimum at pH 6·8-7·0, and lipase at pH 6·4-6·6 and 7·3-7·7 depending on the substrate. 5. The amount of carbon dioxide bound as carbonate by the glands was measured in a series of experiments with earthworms kept in different calcium salts. The percentage of carbon dioxide excreted as carbonate never exceeded 10 per cent, of the total metabolic carbon dioxide. 6. Absorption of iron saccharate injected into worms took place occasionally, in groups of adjacent cells in the intestine and in isolated cells in the calciferous glands. 7. The true function of the calciferous glands is excretion, calcium carbonate being passed into the gut as crystals of calcite which are chemically inactive in the gut.

Atom Condensed Fukui Function for Condensed Phases and Biological Systems and Its Application to Enzymatic Fixation of Carbon Dioxide

2019 ◽  
Author(s):  
Javier Oller ◽  
David A. Sáez ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Carbon Dioxide ◽  
Aqueous Solution ◽  
Molecular System ◽  
Chemical Reactivity ◽  
Nucleophilic Attack ◽  
Stable Conformation ◽  
Fukui Functions ◽  
Reactivity Descriptors ◽  
Dynamics Simulations ◽  
Fixation Of Carbon Dioxide

<div><div><div><p>Local reactivity descriptors such as atom condensed Fukui functions are promising computational tools to study chemical reactivity at specific sites within a molecule. Their applications have been mainly focused on isolated molecules in their most stable conformation without considering the effects of the surroundings. Here, we propose to combine QM/MM Born-Oppenheimer molecular dynamics simulations to obtain the microstates (configurations) of a molecular system using different representations of the molecular environment and calculate Boltzmann weighted atom condensed local reac- tivity descriptors based on conceptual DFT. Our approach takes the conformational fluctuations of the molecular system and the polarization of its electron density by the environment into account allowing us to analyze the effect of changes in the molecular environment on reactivity. In this contribution, we apply the method mentioned above to the catalytic fixation of carbon dioxide by crotonyl-CoA carboxylase/reductase and study if the enzyme alters the reactivity of its substrate compared to an aqueous solution. Our main result is that the protein en- vironment activates the substrate by the elimination of solute-solvent hydrogen bonds from aqueous solution in the two elementary steps of the reaction mechanism: the nucleophilic attack of a hydride anion from NADPH on the α, β unsaturated thioester and the electrophilic attack of carbon dioxide on the formed enolate species.</p></div></div></div>

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