Modification Of Cement Research Articles

Interfacial porosity model and modification mechanism of broken coal grouting: A theoretical and experimental study

Grouting is the most effective approach for underground broken coal treatment. Traditional cement (TC) has difficulty achieving an ideal grouting anti–seepage and reinforcement effect due to the hydrophobic property of coal. This work developed an interfacial porosity model given Gibbs free energy changes during the droplet spreading on coal surface. And the key factors that affect the interface bonding behaviors were analyzed by means of model calculation. Accordingly, four types of wetting agents were selected to modify the coal hydrophobic property via Fourier Transform Infrared Reflection, pulverized coal settling, and contact angle tests. Results showed that the anionic wetting agent WA–2 exhibited the greatest improvement on the coal wettability, and its addition resulted in a fine promotion effect at 0.5%. Furthermore, grouting simulation experiments on broken coal were conducted to compare the actual grouting effects of the modified and traditional cement. Nuclear Magnetic Resonance results reveal that the porosity of the grouted coal specimens by modified cement (MC) was less than that of TC. Moreover, the quantities of mesopore and macropore were remarkably decreased by 85.76% and 96.69%, respectively. Scanning Electron Microscopy results also presented a superior bonding performance between the MC and the injected coal, which indicates that the surface wettability of coal can be improved by the MC, thereby weakening the coal hydrophobic effect and promoting ion diffusion during the cement hydration process. In effect, resulting in the enhancement of the occlusion force and bonding strength of the grout–coal interface. The finding demonstrates that the wettability modification of cement grout contributes to improving the microstructure of the grout–coal interface, substantially ameliorating the grouting quality and prolonging the stability of broken coal on the macro–level.

Application and modification of bone cement in vertebroplasty: A literature review.

Vertebral compression fractures are more common in the elderly, particularly in postmenopausal women. Most of these people are accompanied by osteoporosis, which can easily lead to spinal deformities and fractures. Once a fracture occurs, the patient would have severe pain response, limited spinal movement, and need to stay in bed for a long time, resulting in a significant decrease in their quality of life. Percutaneous vertebroplasty (PVP) is a minimally invasive spinal surgery that injects bone cement into the diseased vertebrae for therapeutic purposes. It can quickly relieve pain and stabilize the spine. It is widely used in the treatment of vertebral compression fractures and is currently an ideal treatment method. There are many materials of bone cement used in clinical treatment, and each material has unique characteristics. Many scholars would modify the bone cement according to the advantages and disadvantages to make it more suitable for clinical use. In this review, we discuss the clinical application and modification of bone cement.

Performance and Microstructural Evaluation of Asphalt Concrete Produced with Hydrated Lime, Glass Powder and Cement Modifiers

The increasing axle load arising from the growth in vehicular volume reduces the durability of road pavement, hence the need to further strengthen the road pavement. This research focuses on the determination of the performance of asphalt concrete in relation to the microstructural characteristics of the asphaltic concrete produced with hydrated lime, glass powder and ordinary Portland cement as modifiers. Asphalt Concrete (AC) mixes were prepared with Dangote 3X cement (D3C), Lafarge Superset cement (LSC), hydrated lime (HL) and glass powder (GP) in varying proportions of 20, 40, 60, 80 and 100%. The stability and morphology of the asphalt concrete produced were determined using Marshall stability test and scanning electron microscopy respectively. AC containing GP and HL showed maximum stability of 3.61 kN and 4.01 kN respectively. The maximum stability values obtained for the samples containing D3C and LSC as fillers are 4.21 kN and 5.10 kN respectively; these stability values meet the minimum Marshall Design criteria of the Asphalt Institute. The microstructural analysis of the asphalt concrete samples showed that GP has the lowest maximum pore value of 4.39 µm2 in which the inter-particulate spaces in the AC produced with GP are small and the agglomeration of the particles indicated that they are densely packed and are characterized with good strength.

Detecting the Influence of Additives on Asphalt Concrete Durability

Modification of asphalt cement with additives is a sustainable issue. An attempt was made in the present assessment to detect the influence of modification of the asphalt binder by 2 % silica fumes and 4 % fly ash additives on the durability in terms of fatigue life of asphalt concrete mixture under short-term and long-term ageing processes and moisture damage. Asphalt concrete slab samples of wearing course was prepared and compacted by roller. The beam specimens of 400 mm length and 50 mm height and 63 mm width were extracted from the slab samples. The beam specimens had practiced the four-point repeated flexural bending beam test. The fatigue life was monitored as the number of load repetitions to reach the failure under three constant micro strain levels of (250, 400, and 750). The reduction in fatigue life after long-term ageing for control, silica fumes modified, and fly ash modified mixtures was (74.7, 38.4, and 60) %, (66.2, 52.4, and 64.3) %, (63.9, 63.1, and 57.5) % under 250, 400, and 750 microstrain levels respectively. However, the reduction in fatigue life after practicing moisture damage for control, silica fumes modified, and fly ash modified mixtures was (71.2, 59.6, and 37.2) %, (37.1, 64.9, and 11.2) %, (71, 84.8, and 32.2) % under (250, 400, and 750) microstrain levels respectively. It was concluded that Fly ash exhibit lower susceptibility to long-term ageing process as compared to other mixtures, while silica fumes exhibit lower susceptibility to moisture damage as compared to other mixtures.

Evaluation of the physical and rheology properties of rubberized asphalt cement

Asphalt cement is a viscoelastic substance that operates like an elastic solid at low service temperatures or under rapid loading. Whenever loaded slowly or at high temperatures, it behaves like a viscous liquid. This classic duality necessitates enhancing the efficiency of an asphalt binder to decrease stress cracking at cold temperatures (fatigue) and plastic deformation at hot temperatures (rutting). The use of polymer-modified asphalt binder is one solution for satisfying today's pavement performance standards. The purpose of this study was to determine the impact of asphalt cement modifiers on the physical and rheological properties of asphalt cement. This study used asphalt cement with a penetration grade of 40-50, modified with styrene-butadiene rubber (SBR) at four different levels of modification, specifically 0%, 2%, 4%, and 6% by weight of asphalt cement. Depending on Rotational viscosity and dynamic shear rheometer, and the traditional test. The mixes modified with SBR polymer showed enhanced physical and rheology characteristics, with decreased penetration and ductility and increased viscosity and softening point, as well as a lower rutting factor, indicating an increase in rutting resistance, according to the experimental data. The performance grade for original asphalt cement was 64-16, and for SBR at 2% additive, the original PG was improved to PG70-16. Adding 4% additive to asphalt cement improved the performance grade to PG76-16, and using 6% increased the performance grade to PG82-16.

Modification of Calcium Aluminate Cement with Phosphate for Incorporation of Strontium Chloride

Modification of Calcium Aluminate Cement with Phosphate for Incorporation of Strontium Chloride

Transformation kinetics of potassium and magnesium modified high-performance brushite cement to carbonated apatite in blood-mimicked condition

As a starting cement material, brushite is beneficial due to its short setting time and fast resorbability, and is metastable, allowing in vivo and in vitro transformation into a more stable calcium phosphate (CaP) phase. The challenges for a successful application of brushite include tissue inflammation from its acidic nature, and poor mechanical strength from weakly compacted crystals. Thus, in this study, it is aimed to avoid these drawbacks through a chemical modification of brushite cement. To circumvent tissue inflammation, brushite was modified with 5% of K+ or Mg2+ to induce the transformation into a more stable phase like hydroxyapatite (HAp). Surface transformation in a Tas-stimulated body fluid (Tas-SBF) solution occurred faster for K+-modified cements (1 week, to HAp and β-TCP) than for unmodified brushite (2 weeks, to HAp), and Mg2+-modified brushite (2 weeks, to HAp and β-TCP). Bulk transformation depended on the penetration of the Tas-SBF solution. Thus, Mg2+-substituted cement exhibited the most apatitic structure (26 wt%) due to the highest porosity. To improve the mechanical properties of brushite, setting retardants (acid pyrophosphate, citric acid) and an excess amount of β-TCP as a filler material were included in the cement’s composition. Diametral tensile strength (DTS) was the highest for unsubstituted cements (4.96 ± 1.04 MPa), slightly lower for K+-enriched cement (4.01 ± 0.71 MPa), and lowest for Mg2+-doped cements (1.34 ± 0.23 MPa). This study shows that it is possible to induce the transformation of brushite cement into a more biocompatible bone-like cement and simultaneously achieve enhanced mechanical properties through compositional modification of the cement.

Impact of Styrene-Butadiene-Styrene (SBS) content on asphalt Binder’s fatigue resistance at various aging levels using Viscoelastic Continuum Damage and fracture mechanics

The use Styrene-Butadiene-Styrene (SBS) modification of asphalt cement is considered as one of the effective ways to improve pavement performance. The increase in stiffness and the improved elastic response of the asphalt cement provide pavements with better rutting and fatigue resistance. On the other hand, cracking resistance in asphalt cement has proven to be a difficult property to evaluate. Several methods have been proposed, and one such method is the high strain Linear Amplitude Sweep (LAS) test using the dynamic shear rheometer, which has shown a good ability to evaluate cracking resistance in asphalt cement. The aim of this research is to examine the ability of different binder characterization techniques to distinguish the level of polymer modification in asphalt cements, as well as their ability to characterize fatigue resistance at different aging levels. Testing with the LAS has shown that the cycles to failure calculated using the Viscoelastic Continuum Damage Model correlate well with the concentration of SBS. The LAS can also be analyzed using fracture mechanics (Pure LAS) and this approach has also shown some correlation with SBS concentrations. The Pure LAS analysis has been shown to improve upon the characterization of different levels of laboratory aging. Finally, fatigue resistance of asphalt concrete specimens prepared with different levels of the SBS modification was studied using Four-Point Bending Beam test. A strong correlation was found between the results of asphalt cement LAS tests and fatigue testing of asphalt concrete mixtures. Both forms of analysis indicate that the LAS approach may provide good feedback when evaluating the role that SBS plays in improving the cracking resistance of asphalt cement. These are important developments for the characterization of cracking resistance in the asphalt binder which can lead to improved material selection for pavements.

Effect of Ultrafine Additives on the Morphology of Cement Hydration Products

The present research is focused on the investigation of the influence of ultrafine additives on the structure formation of hardened cement paste and the establishment of the mechanisms of the morphological transformations, which determine the properties of hydrated products. In the course of the research, the modification of ordinary Portland cement was performed by the suspension of multi-walled carbon nanotubes (MWCNTs), carbon black (CB) paste, and silica fume (SF). Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD) analysis, thermal analysis, and Fourier-transform infrared (FTIR) spectroscopy were used to study cement hydration products. The morphology of hardened cement paste depends on the chemical reactivity of additives, their geometry, and their genesis. The action mechanism of the inert carbon-based additives and pozzolanic silica fume were considered. The cement hydration products formed in the process of modification by both types of ultrafine additives are described. In the case of the modification of cement paste by inert MWCNTs and CB paste, the formation of cement hydration products on their surface without strong adhesion was observed, whereas in the case of the addition of SF separately and together with MWCNTs, the strong adhesion of additives and cement hydration products was noted.

Pressed Magnesia Composites with Improved Weather Resistance Properties

The results of studies aimed at increasing the resistance to weathering of building products based on magnesia cement are presented. This goal was achieved by the use of mine burnt rock as a modifying additive and the use of molding sands compaction pressing method. The influence of the modifier on the compressive strength change of compressed composites in dried and water-saturated state, the softening and air resistance coefficients, as well as the linear deformations of the control samples after a specified number of alternating wetting and drying cycles, was investigated. The physical and mechanical characteristics of the control samples were determined according to the standard and generally accepted methods. The formation of a complex combined structure of modified magnesian composites, containing coagulation, condensation and crystallization phases with a clear predominance of the first, has been confirmed by the physicochemical analysis methods. It is shown that modification of magnesian cement with burnt rock purposefully changes the processes of structure formation and causes an increase in water and air resistance of pressed composites based on it. The proposed method for modifying pressed magnesia products prevents loosening of their structure under alternating stresses, reduces linear deformations and, as a result, slows down fatigue failure. The involvement of a secondary resource in the composition of molding sands as an active mineral additive leads to a decrease in the cost of products and allows the method of their production to be attributed to the best available technologies. The developed compositions of pressed magnesia composites are recommended for the production of small-piece products used in building envelopes, as well as for flooring in the rooms with more than 60% humidity.

Modification of high-volume fly ash cement with metakaolin for its utilization in cemented paste backfill: The effects of metakaolin content and particle size

High-volume fly ash (FA) cement presented a slow setting and lower early compressive strength, restricting the utilization in cemented paste backfill (CPB). The present work investigated the feasibility of using metakaolin with various particle sizes and content to modify the properties of FA cement. Reaction kinetics, rheological properties, setting time, compressive strength, hydration products, and the CPB samples' microstructure were thoroughly studied. The results showed that 5 wt% of super-fine metakaolin (SMK) could strongly promote the binder hydration, leading to the formation of a more compact matrix with higher early compressive strength. The 3 d-compressive strength of the CPB samples was increased by around 216% after replaced by 5 wt% of SMK. Besides, the binder doped with 5 wt% SMK showed better environmental and cost performance.

Research on Grouting Materials for Underground Construction Projects

The engineering practice shows that the application of grouting technology to treat underground engineering has strong applicability and is one of the most commonly used technical means at present. Based on the underground engineering, this paper introduces the research achievements of grouting materials in recent years, including cement-based grouting materials, mixed grouting materials, anti-scouring grouting materials, and ultra-fine cement grouting materials. Current demand of grouting materials in underground engineering, there exists large dosage of cement, high content, high cost, serious environmental pollution problems, such as looking for alternatives or mixed with other raw materials for preparation of cementation material become the development trend, compared with the cement grouting material, chemical grouting material with higher performance, but in smaller projects within the scope of application. How to reduce the production cost of chemical grouting materials, simplify the production process, overcome the existing toxicity, reduce environmental pollution and improve the durability of solidified body has become the bottleneck of its popularization and application. Some achievements have been made in the modification of cement or chemical materials by nanometer components, but there is still a long way to go before the large-scale application of grouting engineering.

Hydration Modification of Cement in the Presence of Diethanol-Isopropanolamine

In this investigation, calorimetry, quantitative X-ray diffraction analysis and the scanning electron microscopy were applied to explore the mechanism of hydration modification of cement with diethanol-isopropanolamine (DEIPA). It showed that the addition of DEIPA favoured the strength development on 3 and 28 days, but was undesirable for the 1d strength. The reason for this was that the dissolution of intermediate phase being promoted by DEIPA participated in the aluminate reaction interrupting the normal hydration of C3S. Appropriate adjustment on SO3 content in the cement was able to slow down the rate of aluminate reaction allowing C3S to react in a right fashion, which gave an optimum strength enhancement at early ages. The addition of DEIPA also impacted the formation of hydrates. Significant differences can be recognized in quantities, chemical compositions and the morphologies of hydrates in blank sample and the DEIPA-dosing ones. With the help of SO3 adjustment in cement with DEIPA, a great number of hydro-sulfoaluminates precipitated at the early stage of hydration to decrease the porosity of hardened cement pastes, which contributed to the strength gain of cement.

A novel sealing material and a bag-grouting sealing method for underground CBM drainage in China

Coalbed methane (CBM) is not only a hazard to underground coal mines and atmospheric environment, but also an unconventional natural gas. The effect of underground CBM drainage is influenced markedly by borehole sealing quality. This research focused on a novel sealing material and a bag-grouting sealing method for CBM drainage. First, based on leakages of underground CBM drainage borehole, a material with dual expansion sources (DE) was proposed. Then, the expansion ratios (by rubber bag method) and the expansion pressures (under small swelling) of a modified cement (MC) and the DE were tested. Next, a bag-grouting sealing method, characterized by a bag-grouting sealing device, was proposed. Slurry can be grouted into the bag-grouting sealing device continuously, then the borehole can be sealed tightly. Finally, engineering test was performed at No.2 coal mine in Huangling mining area. Laboratory test results show that the DE expands fast at initial hydration stage, then continues to expand slowly. Especially, the expansion ratios of the DE are more than 60%, however, the MC tends to shrink after initial expansion. Besides, the expansion pressures of the DE are above 1.3 MPa, which are much greater than those of the MC. Engineering test results show that the effect of the DE and the bag-grouting sealing method is preferable to that of the MC and the traditional “two sealing and one grouting” method. The average methane concentration of the boreholes, sealed by the bag-grouting sealing method with the DE as sealing material, is 40% within 90 days. Besides, the concentration does not decrease drastically.

When the Modifications Made to the Foggara Disturb the Environment

This paper examines, for the first time, the consequences of modifications to the Foggara system on the environment. During our work and research missions carried out in the oases of Touat, Gourara and Tidikelt during the last 20 years (period 2000–2020), we have observed new practices operated by land owners on the Foggara, namely changes introduced in different parts of the Foggara with the aim of improving the flow of the Foggara. Two materials, PVC and Cement, were introduced in the oases of Touat, Gourara and Tidikelt. The earthen Souagui were replaced by PVC and PEHD pipes and the earthen Madjens were changed to cement Madjens. These modifications turned out to be dramatic for the aesthetics and hydraulics of the Foggara. Such interferences may cause the disappearance of this ancestral heritage, and will have negative repercussions on tourism in the region. Keywords: Cement modification; Environment; Foggara; Oasis; PVC pipe.

Evaluating the mechanical properties of thin asphalt overlay incorporating reed ash

Thin Asphalt Overlay (TAO) is a preservation maintenance technique that has been shown to overcome shortcomings in the functional properties of surface pavement layers. Although TAO is not a structural layer, its application sustains the pavement’s structural strength and increases its lifespan, which is a valuable effect for the paving industry. Due to recent realisation of the limits of natural resources and the high cost of raw materials, the paving industry has also developed a secondary target of incorporating waste materials as an alternative to conventional raw materials, both to reduce environmental pollution and minimise costs, in such applications. This study focuses on evaluating the effect of using reed ash (RA) in this manner on the mechanical properties of TAO. The control TAO mixture was densely graded, with a 9.5 mm nominal maximum aggregate size (NMAS) utilising a 40/50 asphalt binder grade. Three percentages of RA were incorporated, 6%, 12% and 18%, to produce modified asphalt binder. To verify the effect of this material on cracking behaviours, resistance to permanent deformation of TAO, indirect tensile strength, creep compliance, and wheel track tests were carried out on both control and modified asphalt mixtures. The results showed a significant enhancement in the performance of TAO modified with 6% RA as compared to the control mixture, although the very high dosage of 18% reduced the performance of the relevant TAO mixtures. This study thus indicates that using this waste material can offer an alternative solution for asphalt cement modification, increasing sustainability, if dosages are carefully controlled.

Chemical composition of barium hydrosilicates for cement modification

Chemical composition of barium hydrosilicates for cement modification

Material Characterization and Balanced Design of Asphalt–Rubber Binders

AbstractCurrent specifications for asphalt–rubber (AR) binders is designate the degree of rubberized modification of the asphalt cement at a specific temperature. It is necessary to investigate the...

Investigating the impact of zeolite on reducing the effects of changes in runoff acidity and the moisture sensitivity of asphalt mixtures

Most studies evaluating the performance of asphalt mixtures against moisture damage use distilled water or drinking water to create wet conditions. However, the main part of the moisture entering the asphalt layers in the pavement is the rainfall runoff that contains dust, soot, and other pollutants absorbed by the pavement surface, which affect the acidity of rainfall runoff. Accordingly, the impacts of water acidity and Zeolite as an environmental pollutant absorbent, as well as a pH moderator of the water entering the asphalt layers, were investigated on the moisture sensitivity of different asphalt mixtures with mechanical and surface free energy (SFE) tests. The results of the mechanical methods revealed that the change in the runoff acidity increases the moisture damage potential of asphalt mixtures. Asphalt cement modification with Zeolite reduced the drop in the tensile strength ratio (TSR) as a result of changing the pH. The application of Zeolite increased the base component of SFE and reduced the acid component of the asphalt cement. The use of Zeolite caused the formation of amorphous chains in the asphalt cement structure, which increased the nonpolar component of SFE. The polar SFE component of the asphalt cement was slightly improved with the incorporation of Zeolite. The utilization of Zeolite increased the free energy of cohesion, thereby increasing the resistance of the asphalt cement film to cohesive failure. In addition, the debonding energy calculations indicated a decrease in this component due to asphalt cement modification. The results of both mechanical and thermodynamic methods illustrated that asphalt cement modification with Zeolite has a positive effect on decreasing the debonding energy and, thus, reducing moisture damage.

Influence of coir fiber reinforcement on shear strength parameters of cement modified marginal soil mixed with fly ash

In the context of paucity for suitable granular soils at various work sites, it has become inevitable for the use of marginal soils (low quality soils) and has been being used for different types of constructions. With the advent of reinforcing soil, a wide variety of materials such as geosynthetics are used for reinforcement. Apart from geosynthetics, coir fiber is also been used for soil strength improvement for their engineering practice. Coir fiber is randomly distributed in soil mass for the purpose of reinforcement. Fly ash has been used at several work sites due to its abundant availability as a waste material. The effective use of Fly ash has an advantage over saving and preserving natural resources, leading in the reduction in cost of the project. Apart from various other techniques of soil modification such as chemical stabilization, lime stabilization etc; the cement modification has got prominence. In the present study, the marginal soil is treated with 3% cement that could able to make it non–plastic. An attempt was made to investigate the effectiveness of coir fiber as reinforcement for locally available cement modified marginal soil and mixed with Fly ash. The intention of the work is to study the effectiveness of coir fiber as a randomly distributed reinforcement on shear strength and strength characteristics of cement modified marginal soil mixed with Fly ash. A series of laboratory tests such as direct shear and unconfined compressive strength tests were conducted using marginal soil. The shear strength of this marginal soil reinforced with 2% coir and mixed with 10% Fly ash was 1.5 to 2 times the shear strength of plain marginal soil. Hence, the experimental study provides an approximate solution for enhancement of shear strength of marginal soil, that marginal soil could be used in construction of reinforced soil structures.