Cement Cracks Research Articles

Recycled Plastic Fibers for Minimizing Plastic Shrinkage Cracking of Cement Based Mortar

Recycled Plastic Fibers for Minimizing Plastic Shrinkage Cracking of Cement Based Mortar

Potential Leakage Paths along Cement-formation Interfaces in Wellbores; Implications for CO2 Storage

The concept of geological CO2 storage relies on the capability of the storage site to contain the gas within its intended location. Leakage on a large scale will render the capture, transport and injection processes futile. Flow paths enabling stored CO2 to re-enter the atmosphere can either be caused by geological conditions (e.g. failed caprock integrity) or it can be related to failed integrity of wells that penetrate the reservoir. Leakage along wells, which can occur through the cement porosity, through cracks in cement or along the casing-cement or cement- formation interfaces, has been appointed the “weak link” of safe and efficient geological CO2 storage.In the present work, the cement-formation interface has been studied in detail for various well situations in order to enable estimation of flow through this potential leakage pathway. Two rock formation types, Castlegate sandstone and Mancos shale, were cemented without the use of drilling fluids, with water based mud (WBM) at the interface and with oil based mud (OBM) at the interface. The motivation was to study the degree of adherence, or inversely the degree of debonding, of the well cement as a function of varying surface properties of the rock.The cement-formation interfaces were characterized by X-ray micro computed tomography (μ-CT), which enabled three-dimensional (3D) interface visualization and quantification. It was found that the interface porosity, defined as the volume of interface pores divided by the total sample volume, was strongly dependent on the surface properties of the rock. The cement-sandstone interface porosity was 0.06% without mud, 1.11% with WBM and 0.35% with OBM. The cement-shale interface porosity was 0.69% without mud, 0.76% with WBM and 0.13% with OBM. This underlines that fluid choices made already during drilling affect the long-term sealing ability of a well – and thereby the success of a CO2 storage project.

Stochastic Risk and Uncertainty Analysis for Shale Gas Extraction in the Karoo Basin of South Africa

We made use of groundwater flow and mass transport equations to investigate the crucial potential risk of water pollution from hydraulic fracturing especially in the case of the Karoo system in South Africa. This paper shows that the upward migration of fluids will depend on the apertures of the cement cracks and fractures in the rock formation. The greater the apertures, the quicker the movement of the fluid. We presented a novel sampling method, which is the combination of the Monte Carlo and the Latin hypercube sampling. The method was used for uncertainties analysis of the apertures in the groundwater and mass transport equations. The study reveals that, in the case of the Karoo, fracking will only be successful if and only if the upward methane and fracking fluid migration can be controlled, for example, by plugging the entire fracked reservoir with cement.

Can Plate Osteosynthesis of Periprosthethic Femoral Fractures Cause Cement Mantle Failure Around a Stable Hip Stem? A Biomechanical Analysis

Periprosthetic femoral fractures (PFF) are a serious complication after total hip arthroplasty. Plate fixation with screws perforating the cement mantle is a common treatment option. The study objective was to investigate hip stem stability and cement mantle integrity under dynamic loading. A cemented hip stem was implanted in 17 composite femur models. Nine bone models were osteotomised just distal to the stem and fixed with a polyaxial locking plate the other eight constructs served as the control group. All specimens were tested in a bi-axial material testing machine (100000 cycles). There were no statistically significant differences in axial nor in medial (varus) stem migration. No cement cracks were detected in both groups. Plate fixation of a PFF with a stable, cemented prosthesis did not lead to cement mantle failure in this in vitro study.

Characterization of Deleterious Expansive Reactions in Fagilde Dam

A monitoring system has been detecting progressive displacements in Fagilde dam, completed in 1984. Site inspection revealed the existence of random cracking, surface discoloration, and superficial dissolution of cement in the spillway surfaces and in the upstream face of the dam. The macroscopic signs of deterioration, which could be due to different mechanisms, showed an uneven distribution in the exposed surfaces of the structure. Crushed limestone and alluvial siliceous sand were used as aggregates. Alkali–aggregate reaction was considered to be the likely cause of concrete distress. In order to investigate the causes of cracking and of the movements registered in the wall, drill core sampling was performed and the concrete investigated for the occurrence of expansive reactions. Concrete petrography was complemented by other tests in order to assess the probable evolution of the reactions in the structure in the near future. Residual expansion tests, soluble alkalis evaluation, and unconfined compression tests were carried out. Alkali–aggregate reactions and internal sulfate reaction were considered to be the main causes of damage in the concrete. In this study, microscopy showed to be an essential tool in the identification of the main causes of deterioration.

Crack Length Estimation from the Damage Modelisation around a Cavityi in the Orthopedic Cement of the Total Hip Prosthesis

In orthopedic surgery and particularly in the total hip arthroplasty, the stem fixation is performed in general using a surgical cement which consists essentially of polymer (PMMA). Fracture of cement and prosthesis loosening appears after a high-stress level. This phenomenon origin is due to the presence of micro-cavities in the PMMA volume. The focus of our study is the modeling using the finite-element method of the cement damage around these cavities, the cavities' sizes and shapes effect on the damage risk, and the crack length estimation due to this damage. A small Fortran schedule was incorporated with the Abaqus code to calculate the damage zone. Results show that the presence of a cavity in the cement increases the damage parameter. The damage appears when the cavity is located in cement on the loading axis. If the cavity changes its shape from circular to elliptical, the size of the damage zone increases. One can predict the initiation of a crack in cement with a maximal length of 70μm.Keywords: total hip prosthesis, crack, bone cement, biomechanics, damage.

Characterization of Three Antifungal Calcite-Forming Bacteria, Arthrobacter nicotianae KNUC2100, Bacillus thuringiensis KNUC2103, and Stenotrophomonas maltophilia KNUC2106, Derived from the Korean Islands, Dokdo and Their Application on Mortar

Crack remediation on the surface of cement mortar using microbiological calcium carbonate (CaCO3) precipitation (MICP) has been investigated as a microbial sealing agent on construction materials. However, MICP research has never acknowledged the antifungal properties of calcite-forming bacteria (CFB). Since fungal colonization on concrete surfaces can trigger biodeterioration processes, fungi on concrete buildings have to be prevented. Therefore, to develop a microbial sealing agent that has antifungal properties to remediate cement cracks without deteriorative fungal colonization, we introduced an antifungal CFB isolated from oceanic islands (Dokdo islands, territory of South Korea, located at the edge of the East Sea in Korea.). The isolation of CFB was done using B4 or urea-CaCl2 media. Furthermore, antifungal assays were done using the pairing culture and disk diffusion methods. Five isolated CFB showed CaCO3 precipitation and antifungal activities against deteriorative fungal strains. Subsequently, five candidate bacteria were identified using 16S rDNA sequence analysis. Crack remediation, fungi growth inhibition, and water permeability reduction of antifungal CFB-treated cement surfaces were tested. All antifungal CFB showed crack remediation abilities, but only three strains (KNUC2100, 2103, and 2106) reduced the water permeability. Furthermore, these three strains showed fungi growth inhibition. This paper is the first application research of CFB that have antifungal activity, for an eco-friendly improvement of construction materials.

Well integrity assessment for CO2 injection

PurposeIn the carbon dioxide capture and storage (CCS) project, the integrity of CO2 injection wells plays a vital role in the long‐term safety of CO2 storage. The authors aim to practically investigate possible CO2 leakage of a CO2 injection well section during the injection operation and shut‐in by the thermomechanical FEM simulation. The application of numerical simulation to the CO2 injection well deep underground is the first step that will help in the quantitative evaluation of the mechanical risks.Design/methodology/approachThe injection of CO2 at a temperature different from those of the well and the surrounding geological formation is likely to cause different thermal deformations of constitutive well materials. This could lead to cement cracking and microannuli openings at the interfaces of different materials such as casing/cement and cement/rock. In this paper, the possibility and order of magnitude of cement cracking and microannuli creation in the cross section of the well are assessed from a numerical case study within a classical thermomechanical finite element model framework.FindingsThe possibility of compressive failure and tensile cracking in the cement of the studied wells due to CO2 injection is small unless a large casing eccentricity or an initial defect in the cement is present. Some microannuli openings are generated at interfaces cement/casing and/or cement/rock during the CO2 injection because of different thermal shrinkage of each material. However, the width is not important enough to cause significant CO2 leakage under the studied conditions. The use of “flexible” cement especially developed for oil well applications could mitigate the risk of cement cracking during CO2 injection.Originality/valueNumerous experimental studies on the chemical deterioration of the cement under severe conditions have been carried out. On the other hand, only a few investigations have focused on the mechanical behavior under thermal/pressure changes related to CO2 injection. In this paper, the quantitative analysis to investigate cement cracking and microannuli formation is achieved to help in the identification of possible mechanical defects to cause CO2 leakage. In addition, the discussion about the risk of the possible casing eccentricity and the application of flexible cement in the oil and gas field to CO2 injection well could be practically useful.

Addressing Infrastructure Durability and Sustainability by Self Healing Mechanisms - Recent Advances in Self Healing Concrete and Asphalt

Infrastructures cover a very broad spectrum of different materials. This paper focuses on civil engineering structures, concrete and asphalt in particular. The public demand for such infrastructures is high level of service and performance, high durability and minimum negative ecological impact. New emerging self healing materials science provides solutions to the problem. An overview is given of new developments obtained in research on self healing of cracks in cement based materials and asphalt concrete. At Delft University various projects are running to study self healing mechanisms. The first project that is discussed is Bacterial Concrete, in which bacteria are mixed in concrete, that can precipitate calcite in a crack and with that make concrete structures water tight and enhance durability. In a second project hybrid fibre reinforced cementitious materials are studied that can mechanically repair cracks when they occur. The last project described in this paper is on the ravelling of porous asphalt concrete and how to heal this damage by incorporating embedded microcapsules or steel fibres. The state of the art results in all projects show that self healing is not just a miracle, but materials can be designed for it.

Cellulose Fiber Reinforced Concrete Fracture Mechanisms and Damage Detection Using Acoustic Emission

ASTM C78 standard tests for flexural strength of concrete were conducted on cellulose fiber reinforced concrete (CFRC) specimens using varying percentages of ultimate load. During testing, Acoustic Emission (AE) signals were recorded while after testing, a scanning electron microscope (SEM) was used to visually observe surface features. SEM results appear to illustrate three important stages of the fracture process: cement cracking, fiber-cement debonding, and fiber breakage/pullout. AE results were used to bound ranges for a relationship between AE amplitude and CFRC fracture mechanisms.

Numerical analysis of the crack growth path in the cement mantle of the reconstructed acetabulum

In this study, we use the finite element method to analyze the propagation's path of the crack in the orthopedic cement of the total hip replacement. In fact, a small python statement was incorporated with the Abaqus software to do in loop the following operations: extracting the crack propagation direction from the previous study using the maximal circumferential stresses criterion, drawing the new path, meshing and calculating again (stresses and fracture parameters). The loop is broken when the user's desired crack length is reached (number of propagations) or the value of the mode I stress intensity factor is negative. Results show that the crack propagation's path can be influenced by human body posture. The existing of a cavity in the vicinity of the crack can change its propagation path or can absolutely attract it enough to meet it. Crack can propagate in the outward direction (toward the acetabulum bone) and cannot propagate in the opposite direction, the mode I stress intensity factor increases with the crack length and that of mode II vanishes.

Imaging Wellbore Cement Degradation by Carbon Dioxide under Geologic Sequestration Conditions Using X-ray Computed Microtomography

X-ray microtomography (XMT), a nondestructive three-dimensional imaging technique, was applied to demonstrate its capability to visualize the mineralogical alteration and microstructure changes in hydrated Portland cement exposed to carbon dioxide under geologic sequestration conditions. Steel coupons and basalt fragments were added to the cement paste in order to simulate cement-steel and cement-rock interfaces. XMT image analysis showed the changes of material density and porosity in the degradation front (density: 1.98 g/cm(3), porosity: 40%) and the carbonated zone (density: 2.27 g/cm(3), porosity: 23%) after reaction with CO(2)-saturated water for 5 months compared to unaltered cement (density: 2.15 g/cm(3), porosity: 30%). Three-dimensional XMT imaging was capable of displaying spatially heterogeneous alteration in cement pores, calcium carbonate precipitation in cement cracks, and preferential cement alteration along the cement-steel and cement-rock interfaces. This result also indicates that the interface between cement and host rock or steel casing is likely more vulnerable to a CO(2) attack than the cement matrix in a wellbore environment. It is shown here that XMT imaging can potentially provide a new insight into the physical and chemical degradation of wellbore cement by CO(2) leakage.

Structural Design and Sensitivity Analysis of Semi-Rigid Pavement of a Motorway

This paper presents application of mechanistic-empirical methods in design of semi-rigid pavement for a section of a motorway in Poland. The stage construction was assumed. Three fatigue criteria were applied in the design. For asphalt fatigue cracking and subgrade soil the criteria from the Asphalt Institute (USA) were applied. For fatigue cracking of cement stabilized bases the Dempsey (USA) and De Beer (South Africa) criteria were applied. Software BISAR was used. Additional study was carried out to find the sensitivity of design thickness of asphalt layer related to several design factors. The most significant factors were (a) load transfer through shrinkage and reflective cracks, (b) high summer temperature which causes decrease of asphalt layers stiffness and increase of tensile stresses in cement stabilized bases, and (c) the effect of overloaded vehicles.

Application of Antifungal CFB to Increase the Durability of Cement Mortar

Antifungal cement mortar or microbiological calcium carbonate precipitation on cement surface has been investigated as functional concrete research. However, these research concepts have never been fused with each other. In this study, we introduced the antifungal calciteforming bacteria (CFB) Bacillus aryabhattai KNUC205, isolated from an urban tunnel (Daegu, South Korea). The major fungal deteriogens in urban tunnel, Cladosporium sphaerospermum KNUC253, was used as a sensitive fungal strain. B. aryabhattai KNUC205 showed CaCO3 precipitation on B4 medium. Cracked cement mortar pastes were made and neutralized by modified methods. Subsequently, the mixture of B. aryabhattai KNUC205, conidiospore of C. sphaerospermum KNUC253, and B4 agar was applied to cement cracks and incubated at 18 degrees C for 16 days. B. aryabhattai KNUC205 showed fungal growth inhibition against C. sphaerospermum. Furthermore, B. aryabhattai KNUC205 showed crack remediation ability and water permeability reduction of cement mortar pastes. Taken together, these results suggest that the CaCO3 precipitation and antifungal properties of B. aryabhattai KNUC205 could be used as an effective sealing or coating material that can also prevent deteriorative fungal growth. This study is the first application and evaluation research that incorporates calcite formation with antifungal capabilities of microorganisms for an environment-friendly and more effective protection of cement materials. In this research, the conception of microbial construction materials was expanded.

METHOD TO ANALYZE THE FATIGUE CRACKS IN ACRYLIC BONE CEMENT

Acrylic bone cement is a poly(methyl methacrylate)-based material that ensures short-term stability of orthopedic implants after surgery. Its long-term performance can be affected by many factors (e.g., composition, cement mixing and delivery method, temperature, humidity). Furthermore, patient activities produce a spectrum of cyclic loads that generate microdamage within the acrylic bone cement mantle. Therefore, pre-clinical studies on fatigue damage of acrylic bone cements are essential for predicting the long-term stability of cemented implants. There are several methods for analyzing damage of acrylic bone cement. However, they present a number of limitations. The aim of this study was to validate the use of a high-resolution scanner to analyze the presence of microcracks in acrylic bone cement. The proposed method met predetermined criteria to overcome limitations of previous methods, ensuring approximate spatial resolution of 5 microns, reduction of image acquisition time, and reduction of artifacts due to operator and/or environment during image acquisition. Additionally, the described method was applied to three types of acrylic bone cement specimens that previously were subjected to a fatigue test. The presented method enables the accurate assessment of fatigue damage induced during cycling loading, including quantification of the number, length, type and position of cement cracks.

Clay Nanotube/Poly(methyl methacrylate) Bone Cement Composites with Sustained Antibiotic Release

AbstractOrthopedic‐grade PMMA bone cement, admixed with prophylactic antibiotics, is widely used in hip and knee replacement surgery. There is a critical need to improve its structural integrity and to control antibiotic release. In this study, clay nanotubes are loaded with the antibiotic gentamicin sulfate and the cement is doped with 5–8 wt% nanotubes. The halloysite nanotubes isolate the drug from the cement monomers and serve as nanocontainers for sustained release of the antibiotic. Gentamicin‐loaded clay nanotubes admixed in PMMA cement provide sustained release up to 300–400 h and with enhanced release at cement cracks. The PMMA/halloysite/gentamicin composite tensile strength does not deteriorate as compared with pure cement and its adhesion to bone is significantly increased.magnified image

C-S-H纳米尺度结构模型研究与收缩机理研究进展

作为硬化水泥浆体的主要成分，对C-S-H的纳米尺度结构进行模型化研究将是水泥基材料的组成设计和性能预测重要途径。本文综述了几种经典的用于解释其行为特征的C-S-H抽象模型以及建立在电子显微形貌基础上的模型，描述了C-S-H和水之间的相互作用和水泥基材料收缩的机理。梳理了Jennings学派模型的发展过程和各模型的特点，以及这些模型对水泥浆体收缩机理的解释以及相关的数学物理模型。介绍了建立在纳米尺度C-S-H形貌特征基础上的UIUC模型。C-S-H的纳米结构模型必须和其纳米尺度的形貌特征契合，通过多种研究方法形成C-S-H在纳米尺度结构的共性、本质的特征并在此基础上形成可以解释其宏观性能的模型，将对研究和解决水泥基材料的收缩和开裂具有重要的意义。 As the main component of harden cement paste, the modeling study on the nano scale microstructure of C-S-H is one of the key approach to the composite design and performance prediction of cement based materials. In this paper some classical abstract model of C-S-H and the model based on the electronic microscopy morphology are introduced, the interaction of C-S-H and water is described to interpret the mechanism of the shrinkage of cement based materials. The development of the models of Jennings school and the characters of those models, the interpretation of the shrinkage mechanism of cement with those models and mathematics-physics models of shrinkage are also reviewed. A UIUC model base on the nano morphology of C-S-H is introduced. A good nano scale model of C-S-H must be corres-pond to the morphology of C-S-H, so to find the comprehensive and intrinsical characters of C-S-H morphology and build a model that can interpret the macroscopical performances is very significant to study the shrinkage and cracking of cement based materials.

The dog as a preclinical model to evaluate interface morphology and micro-motion in cemented total knee replacement

This study investigated cemented fixation of the tibial component from a canine total knee replacement preclinical model. The objective was to determine the local morphology at the material interfaces (implant, cement, bone) and the local relative micro- motion due to functional loading following in vivo service. Five skeletally mature research dogs underwent unilateral total knee replacement using a cemented implant system with a polyethylene (PE) monobloc tibial component. Use of the implanted limb was assessed by pressure-sensitive walkway analysis. At 60 weeks post-surgery, the animals were euthanatized and the tibia sectioned en bloc in the sagittal plane to create medial and lateral specimens. High resolution imaging was used to quantify the morphology under the tray and along the keel. Specimens were loaded to 50% body weight and micro- motions at the PE-cement and cement-bone interfaces were quantified. There was significantly (p = 0.002) more cement-bone apposition and interdigitation along the central keel compared to the regions under the tray. Cavitary defects were associated with the perimeters of the implant (60 ± 25%). Interdigitation fraction was negatively correlated with cavitary defect fraction, cement crack fraction, and total micro-motion. Achieving good interdigitation of cement into subchondral bone beneath the tibial tray is associated with improved interface morphology and reduced micro-motion; features that could result in a reduced incidence of aseptic loosening. Multiple drill holes distributed over the cut tibial surface and adequate pressurization of the cement into the subchondral bone should improve fixation and reduce interface micromotion and cavitary defects.

Direct evidence of “damage accumulation” in cement mantles surrounding femoral hip stems retrieved at autopsy: Cement damage correlates with duration of use and BMI

The “damage accumulation” phenomenon has not been quantitatively demonstrated in clinical cement mantles surrounding femoral hip stems. We stained transverse sections of 11 postmortem retrieved femoral hip components fixed with cement using fluorescent dye-penetrant and quantified cement damage, voids, and cement–bone interface gaps in epifluorescence and white light micrographs. Crack density (Cr.Dn), crack length-density (Cr.Ln.Dn), porosity, and cement–bone interface gap fraction (c/b-gap%) were calculated, normalized by mantle area. Multiple regression tests showed that cement damage (Cr.Ln.Dn. & Cr.Dn.) was significantly positively correlated (r2=0.98, p<0.001) with “duration of use” and body mass index (“BMI”) but not cement mantle “porosity”. There were significant interactions: “duration of use”⁎“BMI” was strongly predictive (p<0.005) of Cr.Dn.; and “duration of use”⁎“porosity” was predictive (p=0.04) of Cr.Ln.Dn. Stem related cracks accounted for approximately one fifth of Cr.Dn and one third of Cr.Ln.Dn. The mean c/b-gap% was 13.8% but it did not correlate (r2=0.01, p=0.8) with duration of use. We concluded that duration-dependent fatigue damage accumulation occurred during in vivo use. BMI strongly influenced cement crack length and the rate of new crack formation over time. Voids did not increase the rate of crack initiation but appeared to have promoted crack growth over time. Although not progressive, substantial bone resorption at the cement–bone interface appeared to be common.

Calculation Stress Intensity Factor for Asphalt Pavement Basing on Weight Function Theory

Under the continuing action of temperature stress and load vehicle, the crack in cement stabilized aggregate base can easily reflect up into the asphalt surface layer, affecting driving condition and then affecting the fatigue life of pavement. On the basis of fracture mechanics, taking center crack loaded with uniform tensile stress as study state, methods were derived to calculate the stress intensity factor (abbreviated in the following “SIF”) of the crack at the bottom of asphalt layer using weight function theory and method of Petroski and Achenbach. Through the comparison of different SIFs under different conditions, factors affecting the SIFs such as crack length, load conditions, modulus ratio between base and surface layer and different jointed conditions were studied. To facilitate comparison, taking completely smooth and completely continuous as study boundary conditions. According to calculation results, factors mentioned above all influence the SIF values of the crack at the bottom of asphalt layer greatly, among which jointed condition between base and surface layer has the most important influence. The SIF values of the completely smooth interface is several times that of the completely continuous interface. We can take measures to improve the jointed condition between the asphalt surface layer and the cement stabilized aggregate base thus can reduce reflection crack effectively.