Cement Minerals Research Articles

Study on the Effect of Condensate-Type and Copolymer-Type Combined Superplasticizers on Hydration of Cement

For the limitation of single-component superplasticizer, condensate-type and copolymer-type combined superplasticizers were prepared. The adsorption of compound superplasticizers on cement paste was tested by Total Organic Carbon (TOC) measurement. Influences of superplasticizers on early hydration process of cement and Organo-mineral phase formation were studied by X-Ray Diffraction Analysis (XRD), Scanning Electron Microscope analysis (SEM) and so on. The results show that owing to the electrostatic repulsion and steric effect cooperative mechanism, condensate-type and copolymer-type combined superplasticizers reduce the superplasticizers adsorption in cement minerals and its hydration products surface, delay the process of hydration of C3A, form Organic-Layered double hydroxides (LDH), increase the early chemical shrinkage and promote the growth of cement early hydration and Ettringite

시멘트계 혼화재로서 POFA의 수화반응 특성에 관한 실험적 연구

시멘트계 혼화재로서 POFA의 수화반응 특성에 관한 실험적 연구

Porosity and tortuosity influence on geophysical properties of an artificially cemented sand

Electrical resistivity, saturated hydraulic permeability and P wave velocity are investigated for an artificially cemented sand. The calibration of some known equations used in geophysical characterization tests relating these properties is done considering the presence of artificial bonds. In this case bonds are the hydrated cemented minerals coating the grains. An extensive set of experimental tests was performed, which data is presented in the paper. Artificially cemented sands were prepared with different cement dosages and different water/cement ratios in weight for each dosage. Bonds distribution in the tests performed was controlled by the water used in grout preparation.Known relationships between the geophysical properties studied and porosity, and between electrical resistivity and P wave velocity or hydraulic conductivity, were adopted and calibrated to identify constants to be used for the sand-cement mixtures. Although the different scales, the values found for these constants were compared with those usually found in natural geological formations tested in similar conditions. The existence of such relationships show that it is possible to detect such materials through in situ data interpretation, however scale effects and log resolution must be considered to define the constants for field data.The results are commented considering the presence of the electrically conductive hydrated cement minerals, and how they affect porosity and tortuosity considered in the calibration of the relationships adopted. It is proposed different tortuosities for electrical current and water flow for the cases when electrical conduction through the electrically charged surfaces is more important than through the free liquid phase in the interconnected pores of the saturated material.

Microanalysis of carbonate cement δ18O in a CO2-storage system seal: Insights into the diagenetic history of the Eau Claire Formation (Upper Cambrian), Illinois Basin

Oxygen isotope (δ18O) zonation in carbonate mineral cements is often employed as a proxy record (typically with millimeter-scale resolution) of changing temperature regimes during different stages of sediment diagenesis. Recent advances in secondary ion mass spectrometry allow for highly precise and accurate determinations of cement δ18O values to be made in situ on a micrometer scale, thus significantly increasing the spatial resolution available to studies of diagenesis in sandstone–shale and carbonate systems. Chemo-isotopically zoned dolomite–ankerite cements within shaly sandstone beds of the predominantly silty–shaly Eau Claire Formation (Cambrian, Illinois Basin) were investigated, revealing the following: with increasing depth of burial (from <0.5 to ∼2 km [<1500 to 6500 ft]), cement δ18O values decrease from a high of approximately 24‰ down to approximately 14‰ (on the Vienna standard mean ocean water [VSMOW] scale, equivalent to −6.5‰ to −16.5‰ on the Vienna Peedee belemnite [VPDB] scale). The observed cross-basin trend is largely consistent with cements having formed in response to progressive sediment burial and heating. Within the context of independent burial and thermal history models for the Illinois Basin, cementation began soon after deposition and continued intermittently into the mid-Permian. However, temperatures in excess of burial model predictions are inferred at the time of latest ankerite cement precipitation, which we propose overlapped in time with conductive heating of the Eau Claire Formation (a closed system) from under- and overlying sandstone aquifers that channeled the flow of hot, Mississippi Valley–type mineralizing brines during the mid-Permian (ca. 270 Ma).

A natural cement analogue study to understand the long-term behaviour of cements in nuclear waste repositories: Maqarin (Jordan)

The geological storage of nuclear waste includes multibarrier engineered systems where a large amount of cement-based material is used. Predicting the long term behaviour of cement is approached by reactive transport modelling, where some of the boundary conditions can be defined through studying natural cement analogues (e.g. at the Maqarin natural analogue site). At Maqarin, pyrometamorphism of clay biomicrites and siliceous chalks, caused by the in-situ combustion of organic matter, produced various clinker minerals. The interaction of infiltrating groundwater with these clinker phases resulted in a portlandite-buffered hyperalkaline leachate plume, which migrated into the adjacent biomicrite host rock, resulting in the precipitation of hydrated cement minerals.In this study, rock samples with different degrees of interaction with the hyperalkaline plume were investigated by various methods (mostly SEM-EDS). The observations have identified a paragenetic sequence of hydrous cement minerals, and reveal how the fractures and porosity in the biomicrite have become sequentially filled. In the alkaline disturbed zone, C-A-S-H (an unstoichiometric gel of Ca, Al, Si and OH) is observed to fill the pores of the biomicrite wallrock, as a consequence of reaction with a high pH Ca-rich fluid circulating in fractures. Porosity profiles indicate that in some cases the pores of the rock adjacent to the fractures became tightly sealed, whereas in the veins some porosity is preserved. Later pulses of sulphate-rich groundwater precipitated ettringite and occasionally thaumasite in the veins, whereas downstream in the lower pH distal regions of the hyperalkaline plume, zeolite was precipitated.Comparing our observations with the reactive transport modelling results reveals two major discrepancies: firstly, the models predict that ettringite is precipitated before C-A-S-H, whereas the C-A-S-H is observed as the earlier phase in Maqarin; and, secondly, the models predict that ettringite acts as the principal pore-filling phase in contrast to the C-A-S-H observed in the natural system. These discrepancies are related to the fact that our data were not available at the time the modelling studies were performed. However, all models succeeded in reproducing the porosity reduction observed at the fracture–rock interface in the natural analogue system.

Numerical and Experimental Analysis of Horizontal Stress Changes and Soil Collapse During Chemical Dissolution in a Modified Oedometer Cell

The purpose of this paper is to investigate the horizontal stress evolution and soil collapse during the cement dissolution process using a combination of experimental and numerical methods. The experimental procedure was carried out using a modified oedometer cell with horizontal stress measurements and synthetic samples in order to simulate simultaneous cement dissolution, stress changes and sample deformation. The samples were loaded at a constant vertical stress and exposed to a reactive fluid which dissolved the cementation of the artificial soil. During the dissolution process, sample volume decreased and horizontal stress changes were observed. Initially the horizontal stress decreased due to grain mass loss and then increased due to solid matrix rearrangement. Numerical simulation of these coupled chemical and mechanical processes was performed using a general purpose finite element code capable of performing numerical analysis of engineering problems. The constitutive model adopted to reproduce the soil behavior is an extension of the Barcelona Basic Model for unsaturated soils including the cement mineral concentration as state variable. Some new features were incorporated to the original elasto-plastic model in order to represent the results observed in the experiments. In this paper a good agreement between experimental and numerical results was achieved.

A note on cement in asteroids

Cement mineral tobermorite was formed in hydrothermal experiments on alternation of calcium–aluminum-rich inclusions (CAIs) in carbonaceous chondrite meteorites. Unidentified bands at 14 µm were measured for CAIs and the matrix of the Allende meteorite sample, as well as for Hektor and Agamemnon asteroids. The presence of cement nanoparticles may explain the feature at 14 µm.

Preliminary study of improving reservoir quality of tight gas sands in the near wellbore region by microwave heating

The formation damages, such as water blocking and clay swelling, in tight gas reservoir have been recognized as severe problems impairing gas production. To remedy these damages, formation heat treatment (FHT) was taken as one of the effective measures by some researchers. In this paper, the effects of microwave heating on the petrophysical properties of sandstone samples has been investigated. A modified commercial microwave oven was used to heat the core plugs and aluminum tubes were used to accommodate tight sandstone samples in order to confine them and reduce their contact with air. After microwave heating, any alterations in the porosity, permeability, texture, structure, mineralogy, and pore size distribution of tight sandstones were investigated by a series of lab experiments.By subjecting tight sandstone samples to microwave, the surface temperature of sandstone can be elevated to approximately 400 °C or more. The intense heat is effective in changing the structure, texture and mineralogy of the sandstone. The shrinkage or decomposition of minerals, which are shown by XRD analysis, and generation of micro-fractures created more spaces in the samples. By employing Automated Permeameter, porosity and permeability are found increased after heating. Nuclear Magnetic Resonance (NMR) and CT numbers of all samples after microwave heating indicate the increase of porosity as well. Moreover, the NMR T2 distribution reveals the smaller pores diminished, so the incremental porosity of short NMR T2 decreased. Micro-fractures generated between grains or in grains due to decomposition of some cement minerals and clay shrinkage, so the amplitude of long NMR T2 increased. The fractures are visible both in X-ray CT images and in Scanning Electronic Microscopy (SEM) images. By comparing with NMR T2 distribution data, it is found that the presence of micro-fractures accounts for the increased population of pores with T2 larger than 10 ms.The numerical simulation of microwave heating in the borehole indicates that the microwave heating is effective to raise the temperature of reservoir rock to approximately 900 °C within 1 day and to remove the water within a distance of 25 cm from the borehole wall. The efficiency of microwave heating can be further improved by optimizing the downhole microwave device.

Preparation of belite cement from stockpiled high-carbon fly ash using granule-hydrothermal synthesis method

Belite cement was prepared from lime and long-term stockpiled high-carbon fly ash by granule-hydrothermal synthesis at 97°C followed by calcination at 800–1000°C. The effects of the lime/fly ash ratio, dosage of Na2O and calcination temperature on the phase compositions of the synthesized precursors and clinkers, and the properties of the cements were investigated. Belite cements with the flexural and compressive strengths at 28-day higher then 6.1MPa and 32.8MPa, respectively, were prepared. The results show that the quartz and mullite in the fly ash basically do not take part in the reactions. Adding 0.5–1.5% Na2O promotes the hydrothermal reaction and formation of C–S–H and finally increases the formation of belite. α′L-C2S and C12A7 are the main cementitious minerals in the clinker calcined at 800°C, while β-C2S and gehlenite present when the calcination temperature reached 900°C or higher. Replacing ordinary portland cement partly for the belite cement might reduce the water requirement and increase the strengths.

Multiple dolomitization and later hydrothermal alteration on the Upper Cambrian-Lower Ordovician carbonates in the northern Tarim Basin, China

Thick Upper Cambrian-Lower Ordovician carbonates were deposited on a shallow marine platform in the northern Tarim Basin, which were extensively dolomitized, particularly for the Upper Cambrian carbonates. The resulting dolomite rocks are predominantly composed of matrix dolomites with minor cement dolomites. Based on petrographic textures, matrix dolomites consist of very finely to finely crystalline, nonplanar-a to planar-s dolomite (Md1), finely to medium crystalline, planar-e(s) dolomite (Md2), and finely to coarsely crystalline, nonplanar-a dolomite (Md3). Minor cement dolomites include finely to medium crystalline, planar-s(e) dolomite (Cd1) and coarsely crystalline, nonplanar saddle dolomite (Cd2), which partially or completely fill dissolution vugs and fractures; these cements postdate matrix dolomites but predate later quartz and calcite infills. Origins of matrix and cement dolomites and other diagenetic minerals are interpreted on the basis of petrography, isotopic geochemistry (O, C and Sr), and fluid inclusion microthermometry. Md1 dolomite was initially mediated by microbes and subsequently precipitated from slightly modified brines (e.g., evaporated seawater) in near-surface to very shallow burial settings, whereas Md2 dolomite was formed from connate seawater in association with burial dissolution and localized Mg concentration (or cannibalization) in shallow burial conditions. Md3 dolomite, however, was likely the result of intense recrystallization (or neomorphism) upon previously-formed dolomites (e.g., Md1 or Md2 dolomite) as the host carbonates were deeply buried, and influenced by later hydrothermal fluids. Subsequent cement dolomite and quartz crystals precipitated from higher-temperature, hydrothermal fluids, which were contributed more or less by the extensive Permian large igneous province (LIP) activity in Tarim Basin as evidenced by less radiogenic Sr in the cement and parts of matrix dolomites. This extensive abnormal hydrothermal activity could also have resulted in recrystallization (or neomorphism) on the previous matrix dolomites. Faults/fractures likely acted as important conduit networks which could have channeled the hydrothermal fluids from depths. However, the basin uplift triggered by the Late Hercynian Orogeny from the Late Permian would have facilitated downward infiltration of meteoric water and dilution of hydrothermal fluids, resulting in precipitation of later calcites in which lighter C and more radiogenic Sr components demonstrate such a switch of fluid properties. This study provides a useful analogue to understand the complicated dolomitizing processes and later hydrothermal alteration intimately related to the Permian LIP activity within Tarim Basin and elsewhere.

Strength, Permeability and Carbonation properties of Concrete containing Kota Stone Slurry

Concrete and stone, both are the most commonly used building materials. Rapid development in infrastructure sector has boosted the demand of both, resulting in many environmental concerns. Energy consumption and CO2 emission associated with the production of concrete and cement is a big concern. On the other side, there is a huge solid waste associated with the stone industry which has manifold environmental and financial concerns. For sustainable development, there is a need to utilize the stone waste as a partial replacement of cement (mineral admixture) in concrete so that so that the two problems simultaneously get solved. Kota stone slurry (KSS), which is abundantly available in area of Kota, Rajasthan was used as a partial replacement of the cement in this study. The objective of the present study is to determine strength and durability parameters of the concrete containing Kota stone slurry. The experimental program consists of preparing concrete mixes with two water binder ratios: 0.40 and 0.50 with varying Kota stone slurry percentage as 0, 5, 10, 15, 20 and 25% partially replaced with cement. Compressive and flexural strength test, pull-off test were performed to evaluate strength and DIN 1048 water permeability test, carbonation test and abrasion test were performed to check the durability of concrete mixes. The results indicate that with the increase in Kota stone slurry content, the compressive and flexural strength decreased. There is a marginal decrease in permeability also but the mixes containing Kota stone slurry displayed better resistance to abrasion indicating their suitability as good floor and pavement material. The properties of concrete with Kota stone slurry indicates that it can serve as an alternating material in low cost rural pavements.

Performance study of low environmental impact mortars based on mineral additions and cement resistant to sulfate (CRS)

Performance study of low environmental impact mortars based on mineral additions and cement resistant to sulfate (CRS)

Numerical Approach towards Aging Management of Concrete Structures: Material Strength Evaluation in a Massive Concrete Structure under One-Sided Heating

For the purpose of performance evaluation of an existing reinforced concrete member, a computational simulation model to predict the spatial and temporal changes of physical properties of concrete in the member, named the “Computational Cement-Based Material Model (CCBM)”, was proposed. This proposed simulation model includes models of rate of hydration of cement minerals, phase composition, and resultant hygro-thermo-mechanical properties of cement paste (i.e., compressive strength, Young’s modulus, Poisson’s ratio, thermal expansion coefficient, autogenous shrinkage, drying shrinkage, heat capacity, heat transfer coefficient, water vapor sorption isotherms, and water transfer coefficient). Furthermore, the model for compressive strength of concrete considered the variation in cement paste strength due to its colloidal features as well as micro-defects produced around aggregate due to differences in volume between aggregates and mortar upon heating and drying. The concrete properties of spatial distribution and temporal changes were evaluated by coupling these models with heat and water transport. Validation of these models was achieved by using existing experimental data. Using this CCBM, a thick concrete wall made with moderate Portland cement with a water-to-cement ratio of 0.55 under one-sided heating was simulated and potential problems that can arise during an integrity evaluation were discussed. If the required compressive strength, which was assessed within 91 days of placement, remains unchanged, an additional hydration process can build an adequate strength margin to overcome the risk of strength reduction due to heat and drying. However, in the case that the required strength is increased due to a re-evaluated risk, such as the magnitude of an earthquake, performance evaluation is not trivial as the core sample taken from the side where the execution of sampling is possible could exhibit a greater strength than the average strength of the target concrete member. Therefore, numerical evaluation might aid in this kind of situation.

Effect of Latex Film Distributions on Flexibility of Redispersible Polymer Powders Modified Cement Mortar Evaluated by SEM

Effect of latex film distributions on flexibility of redispersible polymer powders modified cement mortar were evaluated by scanning electron microscopy (SEM). Latex film distributions such as forming interpenetrated networks embedded in cement pastes, covering cement hydrates locally, bonding cement hydrates together, bridging aggregates were all beneficial for the improvement of flexibility of cement mortar. Latex film distributions such as remaining single particles in cement mortar, completing film formation unsuccessfully, film formation on surfaces of aggregates, bonding cement minerals to surfaces of aggregates may contribute little to the improvement of flexibility of cement mortar.

A novel kind of concrete superplasticizer based on lignite graft copolymers

A novel superplasticizer was synthesized by grafting 2-acrylamido-2-tert.butyl sulfonic acid (ATBS) and acrylic acid (AA) monomers onto a lignite backbone using free radical copolymerization technique. Different molar ratios of ATBS:acrylic acid were tested to investigate the influence of the acrylic acid content on the dispersing performance of the graft copolymer. The synthesized polymers were characterized relative to their molecular properties and their dispersing performance in cement. It was found that especially the graft copolymer with an ATBS:acrylic acid molar ratio of 1:0.15 exhibits high dispersing force, long slump retention, high sulfate tolerance and only minor cement retardation. The polymer is more effective than industrial grade BNS. Successful grafting of the monomers was confirmed by size exclusion chromatography and measurement of the adsorbed layer thicknesses.

Investigating flow properties of partially cemented fractures in Travis Peak Formation using image‐based pore‐scale modeling

AbstractNatural fractures can provide preferred flow pathways in otherwise low‐permeability reservoirs. In deep subsurface reservoirs including tight oil and gas reservoirs, as well as in hydrothermal systems, fractures are frequently lined or completely filled with mineral cement that reduces or occludes fracture porosity and permeability. Fracture cement linings potentially reduce flow connectivity between the fracture and host rock and increase fracture wall roughness, which constricts flow. We combined image‐based fracture space characterization, mercury injection capillary pressure and permeability experiments, and numerical simulations to evaluate the influence of fracture‐lining cement on single‐phase and multiphase flows along a natural fracture from the Travis Peak Formation, a tight gas reservoir sandstone in East Texas. Using X‐ray computed microtomographic image analysis, we characterized fracture geometry and the connectivity and geometric tortuosity of the fracture pore space. Combining level set method‐based progressive quasistatic and lattice Boltzmann simulations, we assessed the capillary‐dominated displacement properties and the (relative) permeability of a cement‐lined fracture. Published empirical correlations between aperture and permeability for barren fractures provide permeability estimates that vary among each other, and differ from our results, vary by several orders of magnitude. Compared to barren fractures, cement increases the geometric tortuosity, aperture variation of the pore space, and capillary pressure while reducing the single‐phase permeability by up to 2 orders of magnitude. For multiphase displacement, relative permeability and fluid entrapment geometry resemble those of porous media and differ from those characteristic of barren fractures.

Textural and paleo-fluid flow control on diagenesis in the Paleoproterozoic Franceville Basin, South Eastern, Gabon

The Paleoproterozoic (∼2.15Ga) Franceville Basin, South Eastern Gabon, is a continental sedimentary basin that host unmetamorphosed sediments. This study involve detailed mineralogy, sedimentology, and petrography of the basal sedimentary units of FA and lower FB (FB1) Formations, from the basin margin to centre in relation to mineral paragenesis and fluid flow. The FA Formation conglomerate, sandstone, and mudstone consists lithofacies of mixed fluvial and fluvio-deltaic transitional origin, while the overlying FB1 Formation includes alternating organic rich black shale and sandstone of marine deposit.The medium- to coarse grained fluvio-deltaic quartz arenite in upper part of FA Formation is characterized by pervasive authigenic quartz cementation that reduced the porosity and permeability in the early stage of burial history. This provides a resistant framework for subsequent diagenetic modification and also inhibits fluid flow during burial diagenesis. In contrast, the clay and unstable detrital grains rich fluvial arkosic to sub-arkosic sandstones that escaped early quartz cementation show considerable pressure solution at grain contacts. These arkosics were less porous and permeable when deposited but transformed to diagenetic aquifers as a result of dissolution of detrital grains during diagenesis and subsequent precipitation of authigenic mineral cements in the resulting secondary porosities.From the proximal to distal basin and within sample suites, there is no considerable chemical variation in the petrographic distinct generations of the precipitated illite and chlorite suggesting their precipitation from a near equilibrium homogenous pore-fluid. The predominance of 1Mt illite polytype in most lithologies reflects precipitation of the clay minerals and probably other cements in an environment with high fluid/rock ratio. Dolomite, anhydrite, barite, and Fe-oxides are the main crystallized authigenic minerals aside illite and Fe-rich chlorite clay minerals. The mineralogical assemblages and textural occurrences of the rocks suggest that diagenesis and fluid flow in the FA Formation in the Franceville Basin are mainly controlled by depositional facies.

Influence of water-repellent admixtures on the properties of cements

Influence of organic fatty acid and composition on its basis on the physical and mechanical properties of the cement is investigated. Fatty acids are used in the building industry as water-repellent admixtures. The effectiveness has those admixtures that form on the surface of the cement not solid, but "mesh" protective layer that easily destroyed using traditional method of cement production of concrete and mortar mixes, providing access of water to hydrophilic surface of cement grains.The effect of oleic acid on the physical and mechanical properties is investigated for a trade cement, clinker and Portland cement on its basis, slag and Portland slag cement on its basis. It is found that oleic acid gives hydrophobic properties for trade cement and Portland cement while slowing down the process of its thickening and gives small hydrophobic properties for blast furnace slag slowing down the thickening of Portland slag cement.It is researched an influence of hydrophobic compositions based on oleic acid and investigated admixture with food processing waste vegetable oil on physical and mechanical properties of Portland cement and Portland slag cement. It is found that hydrophobic composition effectively hydrophobize the clinker and slag surfaces under certain optimal concentrations without reducing strength of cements.Hydrophobic composition may be used as a water-repellent admixture for cement and active mineral admixtures to increase the longevity of materials and prevent clumping.

Time-Dependent Strength and Mineralogy of Lime-GGBS Treated Naturally Occurring Acid Sulfate Soils

AbstractThis study investigates the effect of time-dependent mineralogical changes on the unconfined compressive strength (UCS) behavior of lime–ground granulated blast furnace slag (GGBS) treated naturally occurring acid sulfate soils (ASS) containing various proportions of pyrite. Pyrite (0, 2, 4% by weight), GGBS (5, 10, 15, 20% by weight), a fixed lime content of 15% by weight and curing periods up to 365 days were investigated. Mineralogical control on the strength of treated ASS samples was investigated using UCS analyses, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Quantitative phase analysis using XRD data and the Rietveld method was carried out to quantify mineralogical changes. Results show a decrease of UCS values after 180 days curing for ASS containing 4% by weight additional pyrite and treated with 20% by weight GGBS. XRD and SEM analyses suggest that a decline in the abundance of cementitious mineral phases coincides with possible formation of thaumasite-ettringite and ...

Balloon-Assisted Osteoplasty of Periacetabular Tumors following Percutaneous Cryoablation

PurposeTo describe the feasibility, safety, and effectiveness of a technique using vertebral augmentation balloons to promote delivery of cement into periacetabular tumors after cryoablation for fracture prevention. Materials and MethodsA retrospective review was performed of seven consecutive patients (six men and one woman; mean age, 64 y ± 8) with unilateral periacetabular tumors (mean size, 4.2 cm ± 1.4) treated with cryoablation and balloon-assisted osteoplasty for fracture prevention. Cortical defects were seen in six (86%) tumors, and additional pathologic fractures occurred in five (71%) tumors before treatment. The cohort included six (86%) Harrington class I defects and one (14%) class II defect. Procedures were performed with computed tomography fluoroscopic guidance and general anesthesia. Vertebral augmentation balloons (mean, 2; range, 1–4) were inflated within the ablation cavity immediately before or during cement injection. ResultsAll procedures were technically successful. Median percentage tumor fill was 63% (range, 17%–96%). Minor cement leakage occurred in two (29%) patients with no symptomatic or intraarticular extravasation. A new nondisplaced fracture occurred in one patient and was conservatively managed. No major complications occurred. Local tumor progression occurred in one (20%) of five patients with imaging follow-up. ConclusionsBalloon-assisted osteoplasty after cryoablation of periacetabular tumors appears feasible, safe, and effective for fracture prevention. This technique directs cement instillation into ablation defects with a high degree of filling and minimal leakage.