Calcium Carbonate Crystals Research Articles

Isolation and selection of spore-forming bacilli with potential for self-healing of concrete

The self-healing of concrete through the use of bacteria is an ecological, sustainable, and environmentally friendly method that can replace time-consuming and costly repairs. The aim of this research was to isolate and select spore-forming bacilli with potential for concrete self-healing. Soil samples from the limestone mines of Simbal, Trujillo, La Libertad, Peru were used. These samples were processed to primarily isolate spore-forming bacteria. The self-healing potential of these bacteria was evaluated through their ability to produce the urease enzyme, grow at an alkaline pH, and produce calcium carbonate crystals in a culture medium with urea and CaCl2 at pH 8.0. The produced crystals were visualized with scanning electron microscopy and their calcium content was confirmed through EDS analysis. The isolated bacteria were identified by 16 S rRNA gene amplification by PCR as Bacillus sp and Streptomyces sp. It was observed that Bacillus sp. produces CaCO3 crystals with vaterite morphology, while Streptomyces sp. produces rhombohedral calcite crystals. It is concluded that the isolated bacteria have the potential to be used in concrete self-healing processes.

Ethyl methanesulfonate (EMS) mediated dwarfing mutation provides a basis for CaCO3 accumulation by enhancing photosynthetic performance in Ceratostigma willmottianum Stapf.

Ceratostigma willmottianum Stapf is a unique chalk gland (salt-excreting) plant from China, with a salt gland structure that excretes white crystals of calcium carbonate (CaCO3), which has potential biomineralization and carbon sequestration functions. Due to the narrow distribution of wild germplasm resources, there is a lack of diversity of new varieties to satisfy commercial development and scientific exploration. Therefore, we used ethyl methanesulfonate (EMS) mutagenesis to obtain new dwarf mutant germplasm, and analysed it in terms of morphology, growth, photosynthesis, salt glands, and excretion traits. All four dwarfing mutant strains (DM1, DM2, DM3, and DM4) exhibited extreme dwarfing (62.28%, 62.28%, 74.55% and 61.68% reduction in plant height, respectively), faster growth, increased belowground root biomass, and earlier bud differentiation and flowering. Photosynthetic capacity was enhanced: chlorophyll content, maximum quantum yield of PSII (Fv/Fm), effective quantum yield of PSII (ΦPSII), photochemical quenching coefficient (qP), electron transfer rate (ETR), net photosynthesis (Pn), intercellular CO2 concentration (Ci), stomatal conductance (Gs), and transpiration (Tr), were significantly higher in leaves of DM mutants. The density of salt glands per unit leaf area and average Ca2+ excretion rate of individual salt glands increased significantly (especially in DM2), and CaCO3 accumulation per unit leaf area was 28.57% higher than that of the wild type. Pearson correlation analysis showed that photosynthetic capacity was significantly and positively correlated with CaCO3 excretion. The above study not only provided enriched new germplasm of C. willmottianum, but also important research material for studying the mechanism of CaCO3 excretion by salt glands and carbon sequestration capacity of biomineralization.

Research on the Blocking Mechanism of Stagnant Water and the Prediction of Scaling Trend in Fractured Reservoirs in Keshen Gas Field

In this paper, well Keshen 221 was taken as the research object. The stagnant water–rock static experiment showed that, after 8 weeks of the residual water–rock static reaction, the pore size of the inner profile of the rock slice increased from 5 μm to 90 μm, and calcium carbonate crystals were deposited in the hole. Combined with the microscopic visualization model, it is observed that the reservoir blockage mostly occurs at the pore throat diameter, and the small fracture (30 μm) is blocked first, then the large fracture (50 μm). So, it is inferred that the blockage of the reservoir flow channel is caused by the migration of the crystals precipitated by the interaction between the stagnant water and the reservoir rock. On this basis, the TOUGHREACT reservoir model was further constructed to simulate the scaling of the stagnant water in the reservoir matrix and used to compare the scaling of the fractures with 7% and 30% porosity and the retained water at 0.658 m and 768 m. The pre-results of reservoir scaling show that the scaling is more serious when the fractures occur in the far well zone than when the fractures occur in the well entry zone. At the same location, the deposition of large fractures is six times that of small fractures, and the scaling is more severe in large fractures.

The impact of Microbially Induced Calcite Precipitation (MICP) on sand internal erosion resistance: A microfluidic study

Fine particle internal erosion involves the detachment, transport, and deposition of fine particles within soil, significantly impacting agriculture, engineering, and environmental protection. Microbially induced calcite precipitation (MICP) has proven to be an effective method for controlling internal erosion. To optimize MICP protocols for effective erosion control, understanding the microscopic mechanisms by which MICP reduces fine particle erosion is essential but remains unclear. In this study, microfluidic chip experiments were conducted to observe the characteristics of calcium carbonate crystals and fine particles before and after MICP reinforcement and erosion. Through quantitative analysis of the calcium carbonate produced by MICP and eroded fine particles, the effects of bacterial density, concentration of cementation solution, and flow rate on the efficiency of MICP in resisting soil internal erosion were investigated. In addition, three primary mechanisms by which MICP reduces fine particle erosion were identified. Firstly, in situ sand stabilization occurs when calcium carbonate generated by MICP bonds and encapsulates fine particles, forming larger particles that remain stable under erosive flow conditions. Secondly, regional sand stabilization is achieved as MICP-produced calcium carbonate crystals narrow or block the flow channels, preventing extensive migration of fine particles. Lastly, adjacent particle stabilization is facilitated by calcium carbonate crystals, which remain stable during water flow erosion and alter the erosion flow lines, creating zones adjacent to the crystals where fine particle movement is minimized. These findings provide a deeper understanding of the role of MICP in erosion control and can inform the development of more effective erosion mitigation strategies.

Mechanical properties of aeolian sand cemented via microbially induced calcite precipitation (MICP)

The cementation of desert aeolian sand is a key method to control land desertification and dust storms, so an economical, green and durable process to reach the binding between sand grains needs to be searched. The method based on the microbially induced calcite precipitation (MICP) appeared in recent years as a promising process that proved its efficiency. The feasibility of the MICP technique to treat aeolian sand composed by low clay content, fine particles, low water content and characterized by weak permeability was demonstrated in the present paper. The effects of initial dry density, cementation number and curing time on the permeability and strength of MICP-treated aeolian sand were investigated using permeability tests and unconfined compressive strength (UCS) tests. The microstructure of aeolian sand was observed by scanning electron microscopy (SEM) tests and X-ray diffraction (XRD), aiming to reveal the solidification principle of MICP. The tests result indicated that when the initial dry density and the cementation number rose, the hydraulic conductivity of aeolian sand decreased while the mechanical strength given by UCS values improved. When the initial dry density was 1.65 g/cm3, the curing time was 3 h and the cementation number reached 20, the hydraulic conductivity and UCS reached 0.00151 cm/s and 1050.30 kPa, respectively. With increasing curing time, the hydraulic conductivity first decreased, followed by an increase, while the UCS exhibited an up and then a downtrend. Furthermore, the correlation between UCS values and the CaCO3 content reached a high R2 value equal to 0.912, which confirmed that the cementation occurred in sandy material and governed the soil strengthening. Indeed, the calcium carbonate crystals observed by SEM and XRD enhanced the friction between particles when they wrapped around the sand grains surface, while carbonates reduced the soil permeability when filling the pores and sticking the sand particles together. Finally, the theoretical and scientific knowledge brought by the present study should help in managing sand in desert areas.

The failure mechanism of crystallization blockage in tunnel drainage system and preventive measure of scale inhibitor

In recent years, the incidence of crystallization blockages in tunnel drainage systems has become increasingly frequent. This not only poses a serious threat to tunnel operational safety but also significantly escalates maintenance costs. Using a specific tunnel as a case study, this paper offers a preliminary insight into the failure mechanism of the drainage system by examining the characteristics of crystallization blockage issues. Furthermore, from a preventive standpoint, this paper introduces the scale inhibitor and validates its viability through laboratory testing. The findings indicate that the main component of the crystal blockage is CaCO3, which is closely related to the geological and hydrological environment, as well as the design and construction characteristics. Scale inhibitor has a certain anti-crystallization effect, which is mainly achieved by inhibiting the growth process of calcium carbonate crystals, leading to unstable formation. Additionally, within a certain range, the suppression effect of the scale inhibitor will gradually increase with the increase of its concentration.

Microbes: A Remedy for Micro Cracks of Concrete

Crack formation is a very common phenomenon in concrete structures, which allows the entry of water and different type of chemicals into the concrete through the cracks and decreases their durability, strength and, which also affect the reinforcement when it comes in contact with water, CO2 and other chemicals. For repairing the cracks developed in the concrete, it requires regular maintenance and special type of treatment which will be very expansive. To overcome this problem autonomous self-healing mechanism is introduced in the concrete cracks which helps to repair the cracks by producing calcium carbonate crystals that fills the micro cracks and pores in the concrete. During the present investigation Bacillus megaterium is identified for alkaline environment based on their survival.

Sand improvement by microbial-induced carbonate precipitation with casein micelles

This study explores the incorporation of casein micelles to improve the conventional microbial-induced carbonate precipitation technique used for soil improvement. With a single application of the proposed biocementing agent containing casein micelles, a mixed slurry of natural sand solidified to self-sustaining strength within 48 h at 37°C was obtained. The stress–strain curves of the biocemented specimens obtained from a consolidated drained triaxial compression test exhibited sharp peaks at less than 1% strain. Under effective confining pressures of 30, 50 and 100 kPa, the peak deviatoric stress registered 415, 479 and 536 kPa, respectively – representing 1·8–4·1 times the maximum strength of the original sand. Vaterite calcium carbonate crystals formed by the biocementing agent ensured bridging between sand particles, resulting in the improved cohesion. The cohesion-derived residual strength tended to increase at the critical state in biocemented sand under the lowest confining stress. The localised shear band formed by the crystals may control the movement of sand particles, resulting in a change in volumetric strain behaviour. The formation of casein micelles induced the nucleation and growth of spherical crystals, acting as a casein-mediated vaterite. This formation likely contributed to the improved cohesion of sand observed in this study.

Temperature- and alkali-resistant induced domestication of Bacillus pasteurii in drilling fluid and its borehole wall enhancement properties

The microbial induced calcium carbonate precipitation (MICP) technology provides a new approach to solve borehole destabilization in broken formations; however, the high-temperature and alkaline environments inhibit the growth of microorganisms, which in turn affects the performance of their wall enhancement performance. In this study, a pH and temperature-coupled induced domestication method was applied to Bacillus pasteurii, and its wall enhancement performance was evaluated. Post domestication, Bacillus pasteurii exhibited high growth activity at pH 10.3 and temperature 45 °C. In a sodium carboxymethyl cellulose (CMC) drilling fluid environment, bacterial concentration reached 1.373 with urease activity at 1.98 after 24 h, and in a xanthan gum (XG) environment, the figures were 0.931 and 1.76, respectively—significantly higher than those before domestication. The Bacillus pasteurii-CMC system exhibited enhanced performance with the unconfined compressive strength of the specimen up to 1.232 MPa, permeability coefficient as low as 0.024, and calcium carbonate production up to 24.685 g. The crushed specimen portions remained lumpy with even calcium carbonate distribution. In contrast, the Bacillus pasteurii-XG system exhibited the highest unconfined compressive strength of 0.561 MPa, lowest permeability coefficient of 0.081, and the greatest calcium carbonate production of 16.03 g, with an externally cemented shell but internally loose structure and uneven calcium carbonate distribution, resulting in weaker mechanical properties. The Bacillus pasteurii induced predominantly vaterite calcium carbonate crystals in the CMC drilling fluid. In the XG drilling fluid, the crystals were mainly calcite. Both types effectively cemented the broken particles, improving formation strength and reducing permeability. However, under the same conditions, the Bacillus pasteurii-CMC system demonstrated a more pronounced enhancement effect.

Damage and Recovery Behavior of Low-Replacement-Rate Fly Ash Concrete after Different High-Temperature Exposures.

This study focuses on investigating the strength recovery of fire-damaged fly ash concrete (FAC) with a low substitution rate of 10% through post-fire curing. The chemical and microstructural changes were analyzed using X-ray diffraction (XRD), derivative thermogravimetry (DTG), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and nitrogen adsorption. The findings indicate that the incorporation of fly ash slightly enhanced the strength after exposure to 400 °C; this was attributed to improved pozzolanic reactions, which were not observed at higher temperatures of 600 °C and 800 °C. Moreover, a positive effect on the recovery of compressive strength was observed due to the pozzolanic reaction. However, due to the relatively low fly ash content, depletion occurred at a later age, resulting in the inability to inhibit microstructural damage caused by the production of portlandite, thereby weakening the compressive strength. Interestingly, fly ash influenced the morphology of calcium carbonate and calcium silicate hydrate crystals, which is potentially ascribed to the role of high aluminum content acting as a crystallization-guiding agent.

Converting ocean nacre into bone mineral matrix composite for bone regeneration- in vitro and in vivo studies

Nacre of Pinctada maxima is a natural biomineralized matrix, appeared 7 million years before hominins. In this study, we converted nacre into a self-setting particle bound with multiple calcium orthophosphates that reassemble mammals’ bone mineral matrices for induction of bone regeneration. The nacre-based calcium orthophosphates composite (NCOC) exhibited a compression strength of 10 MPa, which is superior to human trabecular bone. In vitro bioactivity tests revealed the formation of apatite with nano-porous flake-like crystals on the composite surface that mimic HA structure of a human bone matrix. NCOC demonstrated efficient attachment and proliferation of osteoblast cells, promoting osteogenic differentiation by increasing expressions of RUNX2 and OPN. In vivo studies using rabbit back fascia demonstrated that NCOC displays better bone healing and biocompatibility than conventional bone substitute apatite in critical bone defect models. The degradation of calcium carbonate crystal in vivo does not compromise structural integrity of NCOC. Overall, our data showed that NCOC produced through self-setting reactions, presents advantages such as accelerated biodegradation and osteostimulative properties, making it a promising bone substitute for effective bone regeneration.

Characterization of mechanical behavior and cementing mechanism of high-strength composites using biomimetic chemically induced calcium carbonate precipitation method

Biomimetic mineralized mortar (BMM) represents a novel green cementitious material, increasingly recognized for its environmental sustainability. In this study, four typical amino acids including acidic amino acids (aspartic acid, glutamic acid), neutral amino acid (threonine), and basic amino acid (arginine), are employed as crystal modifiers to develop the high-strength BMM (HBMM) based on the biomimetic chemically induced calcium carbonate precipitation (BCICP) method. The mechanical properties and failure morphology of HBMM were evaluated through unconfined compressive strength (UCS) test. The microstructure characteristics of HBMM were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and contact angle test. The results show that amino acid-modified calcium carbonate precipitation can effectively cement loose sand particles and significantly improve the strength of the HBMM. The failure modes of HBMM observed include local failure, vertical splitting failure, shear failure, and splitting-shear mixed failure. Notably, aspartic acid and glutamic acid can induce the formation of vaterite-phase calcium carbonate crystals, while threonine and arginine facilitate the formation of aragonite-phase calcium carbonate crystals. The hydrogen bonding between modified calcium carbonate crystals and silanol groups on the silica surface ensures a tight adhesion of the precipitate to sand surfaces, filling gaps and cementing particles. This study elucidates that using amino acids as modifiers in the BCICP method can significantly enhance the strength of HBMM and influence its microstructure, offering valuable insights for its potential practical applications.

Two decades of research trends in microbial-induced carbonate precipitation for heavy metal removal: a bibliometric review and literature review.

Amidst the increasing significance of innovative solutions for bioremediation of heavy metal removal, this paper offers a thorough bibliometric analysis of microbial-induced carbonate precipitation (MICP) for heavy metal removal, as a promising technology to tackle this urgent environmental issue. This study focused on articles published from 1999 to 2022 in the Scopus database. It assesses trends, participation, and key players within the MICP for heavy metal sequestration. Among the 930 identified articles, 74 countries participated in the field, with China being the most productive. Varenyam Achal, the Chinese Academy of Sciences, and Chemosphere are leaders in the research landscape. Using VOSviewer and R-Studio, keyword hotspots like "MICP", "urease", and "heavy metals" underscore the interdisciplinary nature of MICP research and its focus on addressing a wide array of environmental and soil-related challenges. VOSviewer emphasises essential terms like "calcium carbonate crystal", while R-Studio highlights ongoing themes such as "soil" and "organic" aspects. These analyses further showcase the interdisciplinary nature of MICP research, addressing a wide range of environmental challenges and indicating evolving trends in the field. This review also discusses the literature concerning the potential of MICP to immobilise contaminants, the evolution of the research outcome in the last two decades, MICP treatment techniques for heavy metal removal, and critical challenges when scaling from laboratory to field. Readers will find this analysis beneficial in gaining valuable insights into the evolving field and providing a solid foundation for future research and practical implementation.

Understanding the role of different phases in γ-C2S based carbonatable clinkers

Accelerated carbonation of carbonatable clinkers into building products is an effective way of CO2 utilization. However, due to insufficient understanding on the phase characteristics of carbonatable clinkers, there is still a lack of guidance on the selection and design of carbonatable clinkers. In this study, three γ-C2S based carbonatable clinkers were designed and synthesized, covering the carbonation active phase, the unavoidable C2AS and amorphous glass phases when using industrial feedstocks. The differences in the carbonation activity, mechanical properties and microstructure were compared. Results show that the uncarbonated phases have a significant impact on the mechanical properties of carbonated matrix. The presence of unreacted γ-C2S with self-pulverization induced cleavage planes and the amorphous glass phase with poor binding to the adjacent calcium carbonate crystals leads to reduced compressive strength. The carbonation reactivity of γ-C2S formed in composite system is significantly higher than that of pure γ-C2S. Benefiting from the higher degree of carbonation, carbonatable clinkers only need to contain >40 wt% of γ-C2S to obtain comparable compressive strength as the pure γ-C2S system.

Mechanical properties and ductility improvement mechanisms of fiber-reinforced biomimetic mineralized composites using sea sand

Biomimetic mineralized composites (BMC) is an emerging green cementing material. However, the application of BMC is limited by brittle failure. This study proposes novel fiber-reinforced biomimetic mineralized composites (FRBMC) with excellent ductility based on the coupling method of fiber reinforcement and biomimetic chemically induced calcium carbonate precipitation (BCICP). Three typical fibers, including polymer fibers (polypropylene fiber, PF), mineral fibers (basalt fiber, BF), and plant fibers (coir fiber, CF), were used to explore the feasibility of application in FRBMC. Accordingly, mechanical properties, pore structures, and microscopic characteristics were assessed through unconfined compressive strength (UCS) test, mercury intrusion porosimetry (MIP) tests, and scanning electron microscopy (SEM). The results show that fiber induces a transition from brittle to ductile failure modes in BMC. PF exhibits the most notable enhancement in residual strength and peak strain, while BF leads to the highest compressive strength. CF can effectively enhance energy absorption after reaching peak stress. Moreover, FRBMC with CF contains a higher quantity of minute pores, while BF can reduce the porosity of FRBMC. The calcium carbonate crystals effectively cement fibers and sand particles, enhancing the ductility of FRBMC through forming various cementing structures. This study investigates the synergistic effect of BCICP and fiber reinforcement, providing valuable guidance for potential practical applications of FRBMC.

Observation of Transient Prenucleation Species of Calcium Carbonate by DNP-Enhanced NMR.

Knowledge of the mechanism by which polymorphic inorganic species, such as carbonates, are formed is crucial to understand and guide the selective crystallization of end products. Recently it has been shown that a key step in the crystallization of calcium carbonate is the formation of intermediate species known as prenucleation clusters. However, the observation of these prenucleation clusters in solution is exceedingly challenging because of their short lifetime and low concentrations. Here, using dissolution DNP-enhanced NMR spectroscopy, we observe signals from prenucleation species of calcium carbonate from which the kinetics of formation and conversion are determined.

Calcium carbonate crystallization process analysis on a heat transfer surface

This paper explores the growth process of calcium carbonate crystallization fouling on a heat surface using finite element methods to solve physical equations such as momentum, energy, and concentration diffusion, incorporating the impact of bulk crystallization on the concentration of scaling ions. The simulation uses deformation geometry, moving grids, and automatic re-meshing methods to study the dynamic growth of fouling layers and the spatiotemporal changes in fluid velocity, temperature, and concentration field-related parameters caused by it. Results indicate that the deposition interface temperature increases along the flow direction under constant heat flux conditions, leading to an increase in deposition rate. When the interface temperature exceeds 340 K, the fouling deposition rate becomes highly sensitive to temperature changes. The fouling thickness also increases along the flow direction, causing the heat transfer surface near the outlet to face a more severe heat transfer deterioration caused by scaling. Under constant temperature conditions, the deposition rate increases rapidly near the inlet and varies less along the flow direction. When the wall temperature remains constant, scaling is more likely to occur at the fluid inlet as the fluid temperature increases. This model also examines the effects of changes in the porosity of the fouling layer and ion interactions in composite salt solutions on the growth characteristics of the fouling layer.

Biomimetic Synthesis of Calcium Carbonate in Bile in the presence of Amino Acids

Thermodynamic and experimental modeling of calcium carbonate crystallization in a model solution of human bile has been carried out. The process of calcium carbonate (calcite and vaterite) crystallization from solutions containing bile has been studied. It is shown that differences in the phase and group composition of the samples arise depending on the synthesis parameters. It has been established that in the presence of 1 wt. % bile, calcite is formed, and an increase in the concentration of bile in the initial solution from 5 to 100 wt. % contributes to the crystallization of vaterite. It is shown that the mass of the solid phase increases with an increase in the concentration of bile in the initial solution. The dissolution of the synthesized samples was performed in 0.9 wt. % NaCl solution and 0.05 M EDTA solution. It was found that the presence of bile components in the composition of solid samples reduces the rate of their dissolutions.

Crystallization of Calcium Carbonate and Calcium Phosphate Phases in Silica Hydrogel: Morphological and Compositional Characterization

The present study showcases a series of crystallization experiments using a specially designed double diffusion system to grow crystals belonging to the calcium carbonate–phosphate system. The experimental U-shaped device comprised two vertical solution containers, separated by a horizontal column of silica hydrogel. Each container was filled with 0.5 M CaCl2 and 0.5 M Na2CO3 solutions, which diffused through the gel column over time. Na3PO4 solutions, with 50 and 500 ppm concentrations, were incorporated into the gel in different experiments, resulting in a homogeneous distribution of phosphate concentrations within the diffusion column. After 15- and 30-day incubation periods post-nucleation, the crystals formed in different sections of the gel were carefully extracted and studied with scanning electron microscopy and electron microprobe. Additionally, Raman spectra were collected from the samples using a confocal Raman microscope, providing further insights into their molecular composition and structural properties. The obtained results show that under the induced experimental conditions (i) phosphate incorporates into calcite’s structure, and (ii) the growth of calcium phosphates in the presence of carbonate ions involves the sequential, heterogeneous nucleation of CO3-bearing OCP/HAP-like phases, with Raman spectral characteristics very similar to those of bioapatites.

A new inhibitor of quaternary copolymer against calcium carbonate scaling in high-temperature geothermal fluids

An effective quaternary copolymer inhibitor against calcium carbonate scaling in 120 °C geothermal fluids, with an inhibition ratio of over 95 %, was synthesized through aqueous free radical polymerization of itaconic acid (IA), acrylic acid (AA), hydroxy ethyl methacrylate (HEMA), and sodium allylsulfonate (SAS). The synthesis process involved using ammonium persulfate as an initiator and tert-butanol as the molecular weight regulator. A four-factor, three-level orthogonal experiment was conducted to optimize the synthesis process, resulting in a monomer ratio of m(IA):m(AA) = 1:7, 15 % initiator concentration, a reaction temperature of 90 °C, and a reaction time of 2.5 h. Fourier transform infrared spectroscopy (FT-IR) analysis revealed the presence of carboxyl, sulfonic acid, hydroxyl, and ester groups in the copolymer, while thermogravimetric analysis (TGA) confirmed its thermal stability. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) examinations of calcium carbonate crystals indicated that the copolymer scale inhibitor caused significant damage to the surface morphology and crystal structure. This scaling inhibitor is useful for efficient geothermal energy utilization.