Mechanisms of Phase Transformation and Creating Mechanical Strength in a Sustainable Calcium Carbonate Cement

Calcium carbonate cements have been synthesized by mixing amorphous calcium carbonate and vaterite powders with water to unravel the mechanisms of creating mechanical strength during the setting reaction. In-situ XRD was used to monitor the transformation of ACC and vaterite phases into calcite. Unlike this transformation of crystals suspended in a stirred solution, the transformation in the cement is controlled by vaterite dissolution. The supersaturation within the cement paste, Ω, depends not only on the bulk free energy difference of the phases, ΔG, but also on the grain size evolution. Among the strengthening mechanisms, an initial geometric reorganization of CaCO3 particles has been identified by rheological measurements; followed by the formation of an interconnected network of calcite crystals that increases in strength as the crystals grow and form bridges among them. All compositions yield microporous calcite structures with diverse transformation history, crystal bridging efficiency, and hence final mechanical properties.

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Mechanisms of Phase Transformation and Creating Mechanical Strength in a Sustainable Calcium Carbonate Cement

10.20944/preprints201810.0526.v2 ◽

2020 ◽

Author(s):

Jesús Rodríguez-Sánchez ◽

Teresa Liberto ◽

Catherine Barentin ◽

Dag Kristian Dysthe

Keyword(s):

Phase Transformation ◽

Calcium Carbonate ◽

Mechanical Strength ◽

Cement Paste ◽

Volume Fraction ◽

Solid Volume Fraction ◽

Fractal Model ◽

Amorphous Calcium Carbonate ◽

Carbonate Cement ◽

In Situ Xrd

Calcium carbonate cements have been synthesized by mixing amorphous calcium carbonate and vaterite powders with water to form a cement paste and study how mechanical strength is created during the setting reaction. In-situ XRD was used to monitor the transformation of ACC and vaterite phases into calcite and a rotational rheometer was used to monitor the strength evolution. There are two characteristic time scales of the strengthening of the cement paste. The short timescale of the order 1 hour is controlled by smoothening of the vaterite grains, allowing closer and therefore adhesive contacts between the grains. The long timescale of the order 10-50 hours is controlled by the phase transformation of vaterite into calcite. This transformation is, unlike in previous studies using stirred reactors, found to be mainly controlled by diffusion in the liquid phase. The evolution of shear strength with solid volume fraction is best explained by a fractal model of the paste structure.

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Mechanisms of Phase Transformation and Creating Mechanical Strength in a Sustainable Calcium Carbonate Cement

Materials ◽

10.3390/ma13163582 ◽

2020 ◽

Vol 13 (16) ◽

pp. 3582

Author(s):

Jesús Rodríguez-Sánchez ◽

Teresa Liberto ◽

Catherine Barentin ◽

Dag Kristian Dysthe

Keyword(s):

Phase Transformation ◽

Calcium Carbonate ◽

Mechanical Strength ◽

Cement Paste ◽

Volume Fraction ◽

Solid Volume Fraction ◽

Fractal Model ◽

Amorphous Calcium Carbonate ◽

Carbonate Cement ◽

Carbonate Cements

Calcium carbonate cements have been synthesized by mixing amorphous calcium carbonate and vaterite powders with water to form a cement paste and study how mechanical strength is created during the setting reaction. In-situ X-ray diffraction (XRD) was used to monitor the transformation of amorphous calcium carbonate (ACC) and vaterite phases into calcite and a rotational rheometer was used to monitor the strength evolution. There are two characteristic timescales of the strengthening of the cement paste. The short timescale of the order 1 h is controlled by smoothening of the vaterite grains, allowing closer and therefore adhesive contacts between the grains. The long timescale of the order 10–50 h is controlled by the phase transformation of vaterite into calcite. This transformation is, unlike in previous studies using stirred reactors, found to be mainly controlled by diffusion in the liquid phase. The evolution of shear strength with solid volume fraction is best explained by a fractal model of the paste structure.

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Microstructure and Relative Humidity Effects on Long-Term Indentation Creep Properties of Calcium Carbonate Cement

10.20944/preprints201810.0671.v1 ◽

2018 ◽

Cited By ~ 2

Author(s):

Jesús Rodríguez-Sánchez ◽

Qing Zhang ◽

Dag Kristian Dysthe

Keyword(s):

Elastic Modulus ◽

Calcium Carbonate ◽

Relative Humidity ◽

Indentation Creep ◽

Amorphous Calcium Carbonate ◽

Creep Properties ◽

Carbonate Cement ◽

Creep Modulus ◽

Term Creep

This paper addresses the effect of both microstructure and relative humidity on the long-term creep properties of sustainable calcium carbonate (CaCO3) cements. Those can be prepared by mixing amorphous calcium carbonate and vaterite with water. A larger starting amount of vaterite, XV, within the mixture design gives a higher elasticity and resistance to the specimens due to the larger overall bridging area within the newly formed calcite crystals. Regarding creep properties for a given relative humidity, the amplitude of creep strain decreases with XV, and makes the relation between the elastic modulus, E, and hardness, H, of the samples to be linear with the contact creep modulus, C. On the other hand, for a given composition, the amplitude of creep increases with the relative humidity, making the contact creep modulus, Ci, to rise exponentially with the elastic modulus, E, and hardness, H, of the specimens. The most probable creep mechanisms for this kind of cement seem to be a combination of microcraking in the early stages and dissolution and reprecipitation of calcite in the long-term (also known as pressure solution theory). The presence of water in pores with increasing relative humidity might enhance the local dissolution of calcite, and hence the creep amplitude.

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Pressure-driven fusion of amorphous particles into integrated monoliths

Science ◽

10.1126/science.abg1915 ◽

2021 ◽

Vol 372 (6549) ◽

pp. 1466-1470

Author(s):

Zhao Mu ◽

Kangren Kong ◽

Kai Jiang ◽

Hongliang Dong ◽

Xurong Xu ◽

...

Keyword(s):

Calcium Carbonate ◽

Mechanical Strength ◽

Applied Pressure ◽

Bound Water ◽

External Pressure ◽

Temperature Sensitive ◽

Mass Transportation ◽

Amorphous Calcium Carbonate ◽

Amorphous Particles ◽

Biological Organisms

Biological organisms can use amorphous precursors to produce inorganic skeletons with continuous structures through complete particle fusion. Synthesizing monoliths is much more difficult because sintering techniques can destroy continuity and limit mechanical strength. We manufactured inorganic monoliths of amorphous calcium carbonate by the fusion of particles while regulating structurally bound water and external pressure. Our monoliths are transparent, owing to their structural continuity, with a mechanical strength approaching that of single-crystal calcite. Dynamic water channels within the amorphous bulk are synergistically controlled by water content and applied pressure and promote mass transportation for particle fusion. Our strategy provides an alternative to traditional sintering methods that should be attractive for constructing monoliths of temperature-sensitive biominerals and biomaterials.

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Inferred relationship of some uranium deposits and calcium carbonate cement in southern Black Hills, South Dakota

10.3133/b1046a ◽

1956 ◽

Keyword(s):

Calcium Carbonate ◽

South Dakota ◽

Black Hills ◽

Uranium Deposits ◽

Carbonate Cement ◽

Relationship Of

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Pure hydroxyapatite synthesis originating from amorphous calcium carbonate

Scientific Reports ◽

10.1038/s41598-021-91064-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Michika Sawada ◽

Kandi Sridhar ◽

Yasuharu Kanda ◽

Shinya Yamanaka

Keyword(s):

Calcium Carbonate ◽

Calcium Phosphate ◽

Room Temperature ◽

Molar Ratio ◽

Final Phase ◽

Amorphous Calcium Carbonate ◽

Phosphate Compound ◽

Synthesis Strategy ◽

Phosphorylation Reaction ◽

Subsequent Calcination

AbstractWe report a synthesis strategy for pure hydroxyapatite (HAp) using an amorphous calcium carbonate (ACC) colloid as the starting source. Room-temperature phosphorylation and subsequent calcination produce pure HAp via intermediate amorphous calcium phosphate (ACP). The pre-calcined sample undergoes a competitive transformation from ACC to ACP and crystalline calcium carbonate. The water content, ACC concentration, Ca/P molar ratio, and pH during the phosphorylation reaction play crucial roles in the final phase of the crystalline phosphate compound. Pure HAp is formed after ACP is transformed from ACC at a low concentration (1 wt%) of ACC colloid (1.71 < Ca/P < 1.88), whereas Ca/P = 1.51 leads to pure β-tricalcium phosphate. The ACP phases are precursors for calcium phosphate compounds and may determine the final crystalline phase.

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The role of bacterial urease activity on the uniformity of carbonate precipitation profiles of bio-treated coarse sand specimens

Scientific Reports ◽

10.1038/s41598-021-85712-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Charalampos Konstantinou ◽

Yuze Wang ◽

Giovanna Biscontin ◽

Kenichi Soga

Keyword(s):

Calcium Carbonate ◽

Calcium Chloride ◽

Urease Activity ◽

Coarse Sand ◽

Carbonate Precipitation ◽

Population Densities ◽

Carbonate Cements ◽

Microbially Induced Carbonate Precipitation

AbstractProtocols for microbially induced carbonate precipitation (MICP) have been extensively studied in the literature to optimise the process with regard to the amount of injected chemicals, the ratio of urea to calcium chloride, the method of injection and injection intervals, and the population of the bacteria, usually using fine- to medium-grained poorly graded sands. This study assesses the effect of varying urease activities, which have not been studied systematically, and population densities of the bacteria on the uniformity of cementation in very coarse sands (considered poor candidates for treatment). A procedure for producing bacteria with the desired urease activities was developed and qPCR tests were conducted to measure the counts of the RNA of the Ure-C genes. Sand biocementaton experiments followed, showing that slower rates of MICP reactions promote more effective and uniform cementation. Lowering urease activity, in particular, results in progressively more uniformly cemented samples and it is proven to be effective enough when its value is less than 10 mmol/L/h. The work presented highlights the importance of urease activity in controlling the quality and quantity of calcium carbonate cements.

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