Ultrafine Cement Research Articles

Study on the Dense-Packing Effect and Properties of Multi-Component Cementitious Material

The paper studied the effects of single addition of ultrafine fly ash (UFA) and mixed addition of silica fumeultrafine fly ash (SF-UFA) on powder pressure entity dense packing density, mechanical performance and microstructure structure of composite cement paste. The results show that, the ternary system of mixed addition of SF-UFA can effectively further reduced the compacting voidage and more increased packing density of composite powder, compared with the binary system of single addition of UFA. And when the content of SF is 8%, the compacting voidage is the lowest. Next, in the ternary system of mixed with silica fume, ultrafine fly ash and cement (SF-UFA-C), with the increase of silica fume (SF), the total porosity and pore diameter of hardened cementing paste decreased further compared with binary system, and with 8% content of SF and 17% content of UFA, the total porosity of hardened cement paste is the lowest, decreased by 60% than that of reference sample. At last, mixed addition of SF-UFA can improve the long-term strength of composite cement paste either, the compressive strength of 60 days hydration increased by nearly 9% compared with UFA-C and increased 41% compared with the reference sample.

The usage of ultra-fine cement as an admixture to increase the compressive strength of Portland cement mortars

The High-Strength Cement (HSC) technology is based on modification of Normal Use Portland Cement (NUPC) by complex admixtures, optimization of mixture design and grinding process. The present work shows the results of preparing and using Ultra-Fine Cement (UFC) as a binder material addition with no extra admixtures of different chemical composition to increase the compressive strength of mortars. The aim of this work is to demonstrate how a NUPC can be converted into a sort of HSC; it was observed that the 70–60wt%NUPC+30–40wt%UFC blend satisfies the goal of increasing mortar’s compressive strength.

Abandoned well CO2 leakage mitigation using biologically induced mineralization: current progress and future directions

AbstractMethods of mitigating leakage or re‐plugging abandoned wells before exposure to CO2are of high potential interest to prevent leakage of CO2 injected for geologic carbon sequestration in depleted oil and gas reservoirs where large numbers of abandoned wells are often present. While CO2resistant cements and ultrafine cements are being developed, technologies that can be delivered via low viscosity fluids could have significant advantages including the ability to plug small aperture leaks such as fractures or delamination interfaces. Additionally there is the potential to plug rock formation pore space around the wellbore in particularly problematic situations. We are carrying out research on the use of microbial biofilms capable of inducing the precipitation of crystalline calcium carbonate using the process of ureolysis. This method has the potential to reduce well bore permeability, coat cement to reduce CO2–related corrosion, and lower the risk of unwanted upward CO2 migration. In this spotlight, we highlight research currently underway at the Center for Biofilm Engineering (CBE) at Montana State University (MSU) in the area of ureolytic biomineralization sealing for reducing CO2 leakage risk. This research program combines two novel core testing systems and a 3‐dimensional simulation model to investigate biomineralization under both radial and axial flow conditions and at temperatures and pressures which permit CO2 to exist in the supercritical state.This combination of modelling and experimentation is ultimately aimed at developing and verifying biomineralization sealing technologies and strategies which can successfully be applied at the field scale for carbon capture and geological storage (CCGS) projects. © 2013 Society of Chemical Industry and John Wiley & Sons, Ltd

Dry-grinded ultrafine cements hydration. physicochemical and microstructural characterization

The aim of the present research work was the evaluation of the physicochemical and microstructural properties of two ultrafine cements, produced by dry grinding of a commercial CEM I 42.5N cement. The effect of grinding on particle size distribution was determined by laser scattering analyzer. All cements were tested for initial and final setting times, consistency of standard paste, soundness, flow of normal mortar and compressive strengths after 1, 2, 7 and 28 days. The effect of the fineness on the heat of hydration was also investigated. The hydration products were determined by X-ray diffraction analysis and by Fourier transform infrared spectroscopy, at 1, 2, 7 and 28 days. The microstructure of the hardened cement pastes and their morphological characteristics were examined by scanning electron microscopy. Porosity and pore size distribution were evaluated by mercury intrusion porosimetry. The effects of greater fineness on compressive strengths were evident principally at early ages. After the first 24 hours of hydration, the compressive strength of the finest cements was about 3 times higher (over 48 MPa) than the corresponding of CEM I 42.5N (15.1 MPa).

Mechanical activation of cement in stirred media mill

Abstract Stirred media mill is one of the most energy-efficient types of grinding equipment for wet ultrafine grinding. Nevertheless, in a dry mode several problems arise, such as aggregation, agglomeration, sticking on the liners and the grinding media. The present paper deals with experiments carried out on the ultrafine cement grinding in dry mode at various grinding conditions in a stirred media mill to study the mechanochemical effect and the energy efficiency of the mill. Furthermore, comparative grinding experiments were carried out in a ball mill aimed at, first of all, studying the effect of the two grinding modes on the crystal structure of cement. It was found, based on the experimental results, that there is a mechanochemical effect on crystal structure of cement, mostly in the stirred media mill, as it was revealed by X-ray diffraction. Regarding the comparison of the ball mill and the stirred media mill, more energy-effective grinding was achieved in the latter. In addition, the experimental results from the stirred media mill made it possible to determine the effect of the rotor circumferential speed on the mechanical activation of cement.

Influence of colloidal nanosilica on ultrafine cement hydration: Physicochemical and microstructural characterization

The influence of colloidal nanosilica addition on an ultrafine cement have been studied in terms of physicomechanical and microstructure properties. Primarily, experiments were carried out to produce an ultrafine cement (UF) with a Blaine specific surface area greater than 10.500cm2/g. Nanosilica was added in amounts of 2% and 4% on UF cement basis. All cements were tested for initial and final setting times, consistency of standard paste, flow of normal mortar and compressive strengths after 1, 2, 7 and 28days. The hydration products were determined by X-ray diffraction analysis and by Fourier transform infrared spectroscopy, at 1, 2, 7 and 28days. The microstructure of the hardened cement pastes and their morphological characteristics were examined by scanning electron microscopy, whereas porosity and pore size distribution were evaluated by mercury intrusion porosimetry.

Development of Grouting Method of Fine Sand with Ultrafine Cement Grout

Development of Grouting Method of Fine Sand with Ultrafine Cement Grout

Effect of Naphthalene Based Superplasticizers on Performance of Ultrafine White Cement

The compressive strength of ultrafine white cement samples at three ages: 3, 7 and 28 days and micro appearance of hydrates were tested. The influence of the usage of superplasticizers on the compressive strength of ultrafine white cement paste and hydrates were investigated. The results indicated that the 28d compressive strength of ultrafine white cement with 3% naphthalene based superplasticizers added was 92.9 MPa, 22.9% of that of pure ultrafine white cements (75.6 MPa). The addition of superplasticizers was beneficial to the density of white cement paste. A large number of hydrates (AFt, C-H-S, and so on) were generated in the capillary pores, which would improve the structure of capillary pores of hardened cement paste, increase the density and strength.

High-Energy Ball Mill Parameters Used to Obtain Ultra-Fine Portland Cement at Laboratory Level

This paper describes how one of the most significant characteristics of ultra-fine cement (UFC) is its high fineness (maximum particle size below 787 μin. [20 μm]). This kind of cement is obtained once ordinary portland cement (OPC) is ground in common grinding devices. The main disadvantages of this type of processing are the amount of time spent in milling processing and the high production costs. Some novel grinding devices, such as high-energy ball mills (HEBMs), have been used as an alternative to the fine and ultra-fine grinding process, especially in the advanced materials processing research field. The aim of this article was to study the different milling parameters (time, ballpowder ratio [b/p], and milling speed) used in OPC dry-milling processing in order to determine the most suitable combination of these parameters to obtain UFC at the laboratory level. This combination was determined after the characterization of the processed cement powder. The carried-out characterization techniques used were chemical composition, crystallographic phase quantification, change of temperature during the hydration process, and scanning electron microscopy (SEM) images for the morphology of the milled cement. The optimal combination of parameters produced an UFC with a maximum particle size below 590 μin. (15 μm) and a Blaine specific surface area (BSSA) of over 9000 cm2/g.

Improvement of Method to Evaluate Particle Size and Penetrability of Ultrafine Cement Grout

Improvement of Method to Evaluate Particle Size and Penetrability of Ultrafine Cement Grout

Mixture Screening Design to Choose Formulations for Functionally Graded Fiber Cements

This work employing the screening strategy to examine thirteen mix proportions of six-component fiber cement formulations composed of ordinary Portland cement, ultra-fine cement, limestone filler, silica fume, cellulose and polyvinyl alcohol fibers. The vacuum de-watering technique was applied in the production of fiber cement specimens cured for 10 days and submitted to four-point bending tests. The mechanical properties such as limit of proportionality (LOP), modulus of elasticity (MOE), modulus of rupture (MOR) and specific energy (SE) were evaluated and these properties were correlated with the raw material fractions resulting in mixture rules. Results indicate that screening can be a promising methodology with which to generate coherent fiber cement mixture rules, optimize formulations in terms of costs and performance and even facilitate the choosing of formulations for functionally graded fiber cements.

Gas storage in unlined caverns - Norwegian experience over 25 years

Petroleum gas has been stored successfully in unlined caverns in Norway for more than 25 years. Air cushion surge chambers with compressed air have been in use since 30 years ago. The main containment principles are hydrodynamic control of the groundwater and permeability control of the rock mass. The groundwater level often needs to be secured by water infiltration through 'curtains' of drill holes from the surface or designated galleries. Permeability reduction by systematic pre-excavation grouting may be necessary to limit water ingress during operation. Propane/butane and ammonia are stored both at natural rock temperatures at high pressures and chilled at lower pressure. The storage caverns are all unlined. Rock support by rock bolting and sprayed concrete is performed for stabilisation only. Experience shows that with the right combination of methods, it is possible to obtain safe operation without leakage, or with acceptable leakage in case of compressed air storage. Some storage facilities did not achieve the wanted tightness at first, but remedial measures rectified the situation. The principles are applicable in a range of rock formations, and provide significant advantages compared to surface storage (See Table 1). Experience confirms that: thorough geotechnical investigations are necessary; the rock cover must be sufficient to avoid hydraulic splitting; the groundwater level should be maintained during construction by water infiltration; water infiltration is an effective measure to maintain the groundwater level if used after pre-grouting; systematic pre-grouting with micro- and ultra-fine cements at high pressure is necessary if strict requirements to tightness shall be met; grouting of concrete plugs needs special attention; chilled storage has been successful down to -42 degrees C; it is important to have the water seepage under tight control and to follow proven cooling procedures to avoid leakage through the rock mass or around concrete plugs. Although a combination of methods may be needed for each plant, the hydrodynamic control applies primarily to pressurised storage, whereas permeability control is needed for chilled storage. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.

Hydraulicity of wet-milling ultra-fine grouting cement

The physical and mechanical properties of wet-milling ultra-fine grouting cement were studied, and its microstructure was observed through modern instrumentation analysis such as scanning electronic microscopy (SEM), X-ray diffraction and Hg-intrusion micromeritics. The experimental results indicate that wet-milling ultra-fine cement possesses high rheological properties and groutability. It can be filled densely in cracks of rock and hydrate fully, which may endow hydrated cement with high mechanical strength. Main hydration products of wet-milling ultra-fine cement are poorly crystalline C-S-H(I), acicular AFt and plank-shape Ca(OH)2. The dense crystal-network structure can be formed in the rock gaps filled with cement paste, but some weak regions exist owing to Ca(OH)2. The features of micro-pore structure of hydrated wet-milling ultra-fine cement are few big harmful pores, abundant harmless micro pores and little most possible pore radius.

Effect of the addition of ultrafine cement and short fiber reinforcement on shrinkage, rheological and mechanical properties of Portland cement pastes

Abstract The packing density of a powder can be improved by adding a fine powder to a coarse one. This conventional technique, frequently used in ceramic production, also can be applied to optimise the properties of cementitious binders, especially for the production of high performance concrete. In this paper the effect of mixing ultrafine cement and normal grain sized Portland cement is studied. The rheological properties of the fresh paste are influenced positively. An important dispersing effect is observed, decreasing yield value and plastic viscosity. This permits mixing of very low w/c-ratio cement pastes with low porosity and high strengths, applying conventional mixing procedures. Due to the low amount of water, that is available in the narrow pores, the hydration of the cement is not complete. At the same time, permeability is strongly reduced, leading to a lack of water with ongoing hydration. Self-desiccation especially at early age is the consequence. Shrinkage and as a consequence crack formation may be observed. In a special experimental setup early shrinkage (from nearly time zero after mixing) was monitored continuously. Fresh pastes of different mix proportions were put in a cone and the length change was measured by a laser system. Additionally, the shrinkage of hardened pastes was measured until 90 days by conventional technique. The influence of different surrounding climates was studied. Such dense materials generally are very brittle. The use of fibers increases the ductility significantly and leads to a further improvement of the shrinkage and strength properties. The excellent rheological properties of the cement matrix containing ultrafine cement also allows a conventional mixing of composites with a high fiber content. The effect of different amount and type (PP, carbon) of fibers on the shrinkage at very early age and the influence of different curing conditions at early age on the mechanical properties was studied.

Important properties of an ultrafine cement — Part I

Experiments were carried out to eliminate strength retrogression and unusually fast setting characteristics of an ultrafine cement with a Blaine surface area >7000 cm 2/g. A solid retarder, a solid HRWRA, and a superfine fly ash were incorporated in the ultrafine cement to improve its properties. The changes in the important physical, chemical, and other associated properties that result from such additions are reported.

Microstructural development in an ultrafine cement — Part II

Improvements in setting characteristics and strength development were achieved in an ultrafine cement with a specific surface area >7000 cm 2/g by adding small dosages of a solid retarder and a solid HRWRA. Incorporation of 20% superfine fly ash resulted in lower heat generation and better flowability. The microstructural development of these mixes was studied using SEM/EDXA. Calcium hydroxide formation as a function of hydration age was quantified by XRD and TGA. Their paste porosity at 28 days was also measured.

Ultra-fine cements for special applications

Recent development in the application of ultra-fine cement and particle-size distribution-controlled cement are described, focusing on the Japanese experience. They are modified by mixing other fine blending components, organic materials, and admixtures. Their uses are diversified not only in soil and rock grouting, and filling and selling of crack in concrete, but also in peat soil hardening, materials of cement for high performance concrete, and adhesives for bonding insulators with metal fillings.

Ultra-fine cements for special applications

Ultra-fine cements produced on the basis of Portland cement are much finer than ordinary cement and have a steep grading curve. They are specially suited for rock and soil injection but nowadays also for filling and sealing of cracks in concrete.

Alkali Activated Slag And Portland/Slag Ultrafine Cement

AbstractUltrafine Alkali Activated Slag (AAS) and Portland/Slag (P/S) cements have been commercially available in the United States for 2 and 5 years, respectively. Ultrafine cements have been the subject of research at Northwestern University for 6 years.Particle size of the ultrafine slag cement is characterized by 98% passing at 7 microns and a D50 at 3 microns in contrast to the ultrafine portland/slag cement which has 98% passing at 10 microns and a D50 at 4 microns.The chemical composition of the slag used in these cements is 35% SiO2, 16% Al2O3, and 43% CaO. The composition of the portland/slag cement, which is a 25/75 blend, is therefore between the bulk composition of portland cement and the slag.Both of the ultrafine cements permeate fine sands when formulated at high water-to-cement ratios. Viscosity plays an important part in the permeation mechanism, and both cements exhibit viscosities below 10 cps at water-to-cement ratios of 2. This low viscosity is obtained through the use of superplasticizing with naphthalene sulfonate and acrylic acid polymers.Applications of the ultrafine cements include dam grout curtain rehabilitation, consolidation grouting, and nuclear and hazardous waste containment. One hundred and twenty metric tonnes of the portland/slag cement have been used for hazardous waste containment at Niagara Falls, New York.

Properties of High-Strength Concrete

Abstract This paper presents data related to the development of high-strength concrete with special emphasis on the development of high early strength. Both these objectives were achieved by using an ultrafine portland cement with a specific surface of about 750 m2/kg or a high early strength portland cement with about 75% tricalcium silicate content. Experimental data are then reported on strength and elasticity properties, stress-strain behavior, heat of hydration, shrinkage, and creep of these concretes. The results show that using an ultrafine cement, concrete with adequate workability and one-day strengths of 60 to 80 N/mm2 and 35 to 40 N/mm2 can be obtained with granite aggregates and lightweight aggregates, respectively. With high early strength cement and lightweight aggregates, strengths of 10 to 25 N/mm2 in 12 h, and 25 to 45 N/mm2 in 1 day were achieved.