Characteristics Of Cement Research Articles

COMPOSITE MATERIALS BASED ON CEMENT BINDERS MODIFIED WITH SiO2 NANOADDITIVES

Development of nanotechnologies allows to solve a number of problems of construction materials science: increase in strength, durability, abrasion and corrosion resistance that determines operational reliability of building constructions. Generally it is achieved due to nanoparticles that modify the structure and properties of the existing materials or products and are entered into their volume or on a surface layer. It’s theoretically and experimentally proved that the modified water has the bigger activity owing to the change of the ionic composition influencing the рН size and other parameters. As nanoparticles have a high level of surface energy, they show the increased tendency to agglomeration, meanwhile the size of agglomerates can reach several micrometers. In this regard an urgent task is to equally distribute and disaggregate the nanoparticles in the volume of tempering water. The experiments on studying of influence of the nanoparticles of silica distributed in volume of liquid by means of ultrasonic processing on characteristics of cement and sand solution and heavy concrete have been conducted. Nanoadditive influence on density, speed of strength development, final strength under compression of materials on the basis of cement depending on nanoadditive mass percent has been established.

Investigation of Interrelation between Deformation, Composition and Structural Characteristics of Magnesium Oxychloride Cements

The paper studies the process of volume deformation changes in magnesium cement at its hardening in accordance with its composition and structural peculiarities, which result from the roasting parameters of the raw materials. The study has been carried out with the aim of broadening raw materials sources for production of magnesia cements and construction materials through the use waste products of ore-dressing and processing enterprises. The mineralogical and phase composition of magnesium cements, obtained on the basis of magnesite with high content of impurity minerals from the mine dumps, has been studied by the X-ray phase analysis and derivatography. The roasting of the initial raw materials was carried out at various temperature conditions in order to get cements of different activities. The typical content of hydrated phases has been found for the hardened magnesian stone obtained from cements with different activity degrees. The characteristics of volume deformations developed in the magnesian stone have been described in relation to its phase composition. The influence of low- and high-activity crystals and calcium oxide crystals on the soundness and the structural integrity of magnesian stone has been covered.

Utilization of red mud and Pb/Zn smelter waste for the synthesis of a red mud-based cementitious material

A new method in which Pb/Zn smelter waste containing arsenic and heavy metals (arsenic sludge), red mud and lime are utilized to prepare red mud-based cementitious material (RCM) is proposed in this study. XRD, SEM, FTIR and unconfined compressive strength (UCS) tests were employed to assess the physicochemical properties of RCM. In addition, ettringite and iron oxide-containing ettringite were used to study the hydration mechanism of RCM. The results show that the UCS of the RCM (red mud+arsenic sludge+lime) was higher than that of the binder (red mud+arsenic sludge). When the mass ratio of m (binder): m (lime) was 94:6 and then maintained 28days at ambient temperature, the UCS reached 12.05MPa. The red mud has potential cementitious characteristics, and the major source of those characteristics was the aluminium oxide. In the red mud-arsenic sludge-lime system, aluminium oxide was effectively activated by lime and gypsum to form complex hydration products. Some of the aluminium in ettringite was replaced by iron to form calcium sulfoferrite hydrate. The BCR and leaching toxicity results show that the leaching concentration was strongly dependent on the chemical speciation of arsenic and the hydration products. Therefore, the investigated red mud and arsenic sludge can be successfully utilized in cement composites to create a red mud-based cementitious material.

Influence of admixtures on rheological properties and heat of hydration of alkali aluminosilicate cement

The effects of selected admixtures on the set time, rheology, rate of workability loss with time and heat of hydration of an alkali aluminosilicate cement formulated with coal fly ash were investigated. The potential of these admixtures to make these aspects of the fresh alkali aluminosilicate paste behaviour more comparable to those of Portland cement paste were evaluated. Citric acid, borax and phosphoric acid were the admixtures considered in this investigation. They exhibited various degrees of effectiveness in achieving the targeted improvements in the fresh mix characteristics of alkali aluminosilicate cement. All admixtures produced favourable effects on at least one of the properties considered in the investigation. As far as rheology, set time and retention of fresh mix workability over time is concerned, citric acid performed better at the dosages considered in the project, producing qualities comparable to those of Portland cement. Borax and phosphoric acid, however, were more effective in reducing the rate of exothermic heat release and also the total heat released.

Increasing Bending Stiffness of Antibiotic-impregnated Cement-covered Rod Constructs: A Biomechanical Study

Introduction: The use of antibiotic-impregnated cement-covered rods (ACR) has been reported for the treatment of posttraumatic osteomyelitis and infection. Early reports of ACRs described using a 3-mm guidewire as the central core of the rod; however, certain clinical scenarios may require a more rigid construct. We describe the principals and technique of using a thicker metal core to increase stiffness of the ACR. A 40-Fr chest tube was filled with polymethyl methacrylate (PMMA) cement. Metal central rods (3 and 5.8 mm) were inserted before the cement cured. Bending stiffness was measured and compared with a conventional intramedullary nail. Increasing the core diameter of ACR constructs resulted in increased bending stiffness, but the ACR remained significantly weaker than conventional nails. Given the elution characteristics of antibiotic cement, and the relatively short duration of use of these rods, the relative decrease in volume of cement is unlikely to influence antibacterial effectiveness of the ACR. Purpose: The use of ACRs has been reported for the treatment of posttraumatic osteomyelitis and infection. Early reports of antibiotic rods described using a 3-mm guidewire as the central core of the rod; however, certain clinical scenarios may require a more rigid construct. The purpose of this study was to examine the use of a thicker metal core to increase stiffness of the ACR construct. Methods: A 40-Fr chest tube was filled with PMMA cement and metal central rods were inserted before the cement cured. Central cores utilized were a 3-mm intramedullary guidewire and a 5.8-mm fully threaded ring external fixator strut. Bending stiffness was then measured along multiple lengths of each specimen and compared with the bending stiffness of the bare metal inserts (without cement) and a conventional intramedullary nail (10.5-mm titanium). Results: The mean bending stiffness was 4.96±0.67 N m2 for the 5.8-mm-core cement rod and 3.07±0.28 N m2 for the 3-mm-core cement rod (P=0.0039). The bending stiffness for the 3-mm guidewire, 5.8-mm rod, and the intramedullary nail alone were 0.87, 3.1, and 31.7 N m2, respectively. Conclusions: Increasing core diameter of ACR constructs will predictably increase their bending stiffness; however, ACRs will remain significantly weaker than conventional intramedullary nails. Given the elution characteristics of antibiotic cement, and the relatively short duration of use of these rods, the relative decrease in volume of cement is unlikely to influence the antibacterial effectiveness of the ACR.

Chemical Composition and Physical Characteristics of Rice Husk Ash Blended Cement

Applications of agricultural by-product as substitute for non-renewable material in cement production are desirable in stimulating socio-economic development. In this study, Rice Husk Ash (RHA) blended cement was produced by replacing 5%, 7%, 11.25%, 15%, 20.25% and 25% by weight of Ordinary Portland Cement (OPC) clinker with RHA. The cement without RHA serves as the control. The chemical compositions of RHA, OPC-clinker and the blended cements were determined using X-ray fluorescence analyzer. The physical characteristics of RHA blended cements that were considered are fineness, soundness, consistency, initial and final setting times and compressive strength at 2, 7, 28, 56 and 90 curing ages. The results showed that RHA is a suitable material for use as a pozzolan as it satisfied the minimum requirement by having the sum of SiO2, Al2O3 and Fe2O3 of more than 70%. Incorporation of RHA led to an increase in the composition of SiO2 and reduction in that of CaO. An increase in RHA content showed a decrease in compressive strength at early ages and slightly increase at a later age (90 days). The blended cement produced with lower levels of RHA replacement conforms to standard specifications specified in BS EN 197-1:2000, NIS 439:2000 and ASTM C 150-02. The minimum Strength Activated Index (SAI) of 75% at the age of 28 days of curing as specified by ASTM C 618 was satisfied by RHA replacement of up to 15%. It was concluded that blended cement with the maximum of 15% RHA content is suitable for use for structural purposes.

CaO원 활성슬러지를 혼입한 시멘트 경화체 및 모르타르의 특성

CaO원 산업부산물은 CaO, SO3 및 Al2O3 등으로 구성되어 있어 CaO 화합물의 원료로 사용되고 있다. 이러한 CaO원 산업부산물을 레미콘 회수수에 적용할 경우 슬러지수의 pH를 높여주어 콘크리트 분말원료의 수화 반응을 촉진 하여 콘크리트 조직을 치밀하게 하여 성능향상이 가능할 것이다. 본 연구에서는 레미콘 회수수에 CaO원 산업부산물 중 하나인 탈황석고를 혼입하여 제조된 활성슬러지의 효과를 확인하기 위하여 시멘트 경화체 및 모르타르의 특성을 분석하였다. 그 결과 시멘트 경화체의 경우 응결시간 단축 및 높은 안정성을 나타내었으며, 기기분석을 통해 수화반응이 촉진되었음을 확인할 수 있었다. 또한 활성슬러지 제조를 위하여 CaO원으로서 사용된 탈황석고는 단위수량을 조절할 경우 작업성을 확보할 수 있을 뿐만 아니라 적절하게 혼입 될 경우 시멘트 사용량이 줄더라도 높은 강도 발현을 나타내는 것을 확인할 수 있었다.

Comparative study on open air burnt low- and high-carbon rice husk ash as partial cement replacement in cement block production

This study analyzes the feasibility of using high-carbon content rice husk ash waste generated from open air burning of rice husk, as secondary raw materials in the manufacture of cement blocks. Solid masonry blocks having the size of 215mm × 105mm × 65mm, were cast with the mix proportion of 1:5 cement and sand. Blocks were manufactured with two types of rice husk ash (RHA); low-carbon content RHA and high-carbon content RHA. Cement blocks, at four different RHA replacement levels of 5%, 10%, 15% and 20% were prepared for low and high-carbon RHA as partial cement replacement. Testing was included for workability (water/binder ratio and setting time), strength (compressive, flexural bending and splitting tensile) and durability (water absorption, sorption, acid attack resistance and alkaline attack resistance). Results from this test results indicate that the workability, mechanical and durability characteristics of low-carbon RHA cement blocks slightly better than that of high-carbon RHA cement blocks. However, both RHA replacement cement blocks satisfy the limit recommended by standards. Even, high-carbon RHA replacement cement block does not vastly improve the strength or durability properties, the economic and environmental benefits encourage to use high-carbon RHA in cement block production.

Influence of tank bottom surface on growth and welfare of Senegalese sole (Solea senegalensis)

Tank bottom surface is an important question to take into account in flatfish aquaculture considering the intimate contact that the fish have with it. The most usual materials in aquaculture tank surfaces are inert materials such as epoxy resins or plastics with null porosity, and cement that presents a high alkalinity, roughness and porosity. To improve the cement characteristics, silica fume admixture is usually added in construction industry. The aim of this study was to evaluate the effect of three types of tank bottom surfaces on growth and welfare over a Solea senegalensis population. Moreover, the degree of fin erosion, the appearance of skin lesions and malpigmentation patterns were also monitored. The bottom surfaces tested were plain cement (CE), the same plain cement blended with silica fume (10%) (SF) and epoxy coated surface (EP). Specific growth rate for each bottom surface were compared. The Image Processing Activity Index (IPAI) was used to evaluate the Senegalese sole welfare. Higher SGR and lower IPAI values were obtained in the surface of cement with silica fume, suggesting a higher welfare. The use of plain cement affected negatively the performance of fish, probably due to the high pH and alkalinity of the water in direct contact with fish skin. The null porosity of EP seems to be related to the main cause of higher activity level of fish kept on it outcoming in lower growth. Silica fume that is frequently use to improve the mechanical characteristics of plain cement, also provides benefits in terms of fish welfare.

The influence of milling asphalt rates from wearing surface to the flexural strength applied to a recycled layer with Portland cement

The reclaimed asphalt pavement (RAP) on the added cement recycled base can influence on resulted material behavior; because as the RAP tax increases the recycled mixture stiffness and resistance reduces. The RAP acts as a black aggregate or as asphalt lumps on the resulted material depending on the main asphalt cement (AC) characteristics. This suggests that the AC rheological properties from the milling wearing surface can affect the behavior of the cement recycled base. According to a technical bibliography review this issue is rare and not so researched. It is not known until today the level of influence of the AC content and RAP tax on the cement recycled pavement on the structural performance. The authors developed a lab experience according two RAP samples, one with conventional AC and the other with rubber AC, to evaluate the flexural strength. In this case the mixture was stabilized with 3% in cement weight. To realize this study there were molded prismatic samples, 10×10cm×40cm dimensions, to be submitted to dynamic essays, of flexural strength. These prismatic samples, composed by 30%, 50% and 70% of RAP in weight in relation to the base material, behave as beams, under the specific essays. The particle size distribution of each studied RAP samples is offered in this work and also the AC tax and the physical properties, as the asphalt penetration test, melting point and elastic recovering. The resulted data can bring new alternatives to the building process in regions with tropical soils.

Waste-containing clinkers: Valorization of alternative mineral sources from pulp and paper mills

Abstract Waste streams generated from pulp and paper mills show high potential to be used as alternatives raw materials for production of clinker. In this context, this work aims to evaluate the use of such materials to obtain hydraulic binders, which are referred to as Ecoclinkers and Ecocements. Lime mud, wastewater treatment process sludge and biomass ashes were characterized, and five formulations (F1–F5) were developed by applying the Bogue equations. These compositions were processed at three different clinkering temperatures (1350, 1440 and 1455 °C). The formulated Ecoclinkers and a reference hydraulic binder were characterized by X-ray diffractometry to identify the crystalline phases, which were subsequently quantified by the Rietveld method. The results showed that crystalline phase characteristics of clinkers and cements, and compression strengths of ∼20 MPa after 28 days curing time were obtained, confirming the potential use of the investigated waste as alternative materials for production of clinker.

Investigation of the Effect of Cemented Fractures on Fracturing Network Propagation in Model Block with Discrete Orthogonal Fractures

Researchers have recently realized that the natural fractures in shale reservoirs are often cemented or sealed with various minerals. However, the influence of cement characteristics of natural fracture on fracturing network propagation is still not well understood. In this work, laboratory-scaled experiments are proposed to prepare model blocks with discrete orthogonal fractures network with different strength of natural fracture, in order to reveal the influence of cemented natural fractures on the interactions between hydraulic fractures and natural fractures. A series of true triaxial hydraulic fracturing experiments were conducted to investigate the mechanism of hydraulic fracture initiation and propagation in model blocks with natural fractures of different cement strength. The results present different responses of interactions between hydraulic and natural fractures, which can be reflected on the pump pressure profiles and block failure morphology. For model blocks with fluctuated pump pressure curves, the communication degree of hydraulic and natural fractures is good, which is confirmed by a proposed new index of “P-SRV.” The most significant finding is that too high and too low strength properties of cemented natural fracture are adverse to generate complex fracturing network. This work can help us better understand how cemented natural fractures affect the fracturing network propagation subsurface and give us reference to develop more accurate hydraulic fracturing models.

Why Biphasic? Assessment of the Effect on Cell Proliferation and Expression

IntroductionTricalcium silicate (TCS)–based materials are used in endodontics because they are hydraulic and interact with blood, tissue fluids, and phosphate-based root canal irrigants, resulting in biomineralization. Newer-generation materials are biphasic; calcium phosphate is added to the TCS; thus, the material has 2 cementitious phases. The effect of this addition is not known; thus, the aim of this study was to characterize biphasic cements and assess cellular proliferation and expression. MethodsTCS cement mixed with calcium phosphate monobasic or hydroxyapatite in 1:1 proportion was prepared. The powders and the mixed cements soaked in Hank’s balanced salt solution for 28 days were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy, and X-ray diffraction analysis. Ion leaching was investigated using inductively coupled plasma mass spectroscopy. Cellular interaction with material leachate was investigated by exposing human primary osteoblasts to the leachate from the cements. Cell growth and proliferation were determined using methyltetrazolium assay and SEM. ResultsThe addition of a calcium phosphate phase to tricalcium silicate changed the material hydration with a reduction in pH and calcium ion release in the leachate when calcium phosphate monobasic was added. No crystalline calcium hydroxide was formed for both biphasic materials. The biphasic cements exhibited a reduction in cell growth and proliferation. SEM of the materials showed heavy carbonation of the material surface caused by processing for microscopy. ConclusionsThe addition of a second cementitious phase results in modification of the hydration characteristics of TCS cement with deterioration of material and biocompatibility properties.

Effects of aluminate rich slag on compressive strength, drying shrinkage and microstructure of blast furnace slag cement

Aluminate rich steel slag (ARS) is a by-product of the steelmaking process. ARS contains high contents of Al2O3 and CaO and is mainly composed of C12A7 and C3A. This work investigated the effects of ARS and gypsum on the mechanical and chemical properties of blast furnace slag cement. The compressive strength, drying shrinkage, hydration and microstructure characteristics of blast furnace slag cement were investigated based on the addition of different percentages of ARS and gypsum.The results showed that a quaternary binder of OPC-GGBFS-ARS-Gypsum has a beneficial effect on the compressive strength and drying shrinkage. The ettringite formed in the OPC-GGBFS-Gypsum binder were like sharp needles while the ettringite formed in the OPC-GGBFS-ARS-Gypsum binder were like thick needles. Because of such ettringite formation differences, the compressive strength and drying shrinkage of the quaternary binder was better than that of the ternary binder.

Experimental studies on cement stabilized masonry blocks prepared from brick powder, fine recycled concrete aggregate and pozzolanic materials

This experimental work deals with the assessment of strength and water absorption characteristics of cement stabilized masonry block (CSMB) units made with brick powder (BP) and fine recycled concrete aggregate (FRCA) along with pozzolanic materials such as silica fume (SF), fly ash (FA) and ground granulated blast furnace slag (GGBS) as partial replacement for cement. The basic tests such as, dry density, 28 days wet compressive strength, water absorption and rate of moisture absorption are performed on CSMB units of size 190×90×90mm. The correction factors that are available in the literature, with respect to fired clay bricks and compressed earth blocks, so as to account for the confinement of specimens by platen restraints at the ends are used to assess the uniaxial strength of CSMB units. The corrected average values of wet compressive strength of CSMB units at 28 days are found to meet the minimum requirement of 3.5MPa. The percentage of water absorption is found to be higher, but, still within permissible limit of 18% by weight. The average dry density is also found to meet the minimum requirement of 1750kg/m3. The rate of moisture absorption with time is found to follow an exponential trend.

A constitutive material model for a commercial PMMA bone cement using a combination of nano-indentation test and finite element analysis

To obtain accurate mechanical properties of an orthopedic Polymethylmethacrylate (PMMA-based) bone cement, nanomechanical testing was performed. Due to visoelastic characteristics of this polymer-like bone cement, the mechanical properties cannot be identified using conventional indentation methods. A well-known two-layer viscoplasticity model was selected and simulated in a finite element solver. A complete analogical study between the results of the finite element simulation and the experimental data was made to reach the best optimized parameters for the selected model. It is shown that the proposed model can be used to obtain the constitutive material relationship for polymeric materials.

On the mechanical characteristics of a self-setting calcium phosphate cement

ObjectiveTo perform a mechanical characterization of a self-setting calcium phosphate cement in function of the immersion time in Ringer solution. Materials and methodsSpecimens of self-setting calcium phosphate cement were prepared from pure α-TCP powder. The residual strains developed during hardening stage were monitored using an embedded fiber Bragg grating sensor. Additionally, the evolution of the elastic modulus was obtained for the same time period by conducting low-load indentation tests. Micro-computed tomography as well as microscope-assisted inspections were employed to evaluate the porosity in the specimens. Moreover, diametral compression tests were conducted in wet and dried specimens to characterize the material strength. ResultsThe volume of the estimated porosity and absorbed fluid mass, during the first few minutes of the material's exposure in a wet environment, coincide. The immersion in Ringer solution lead to a noticeable increase in the moduli values. The critical value of stresses obtained from the diametral compression tests were combined with the data from uniaxial compression tests, to suggest a Mohr-Coulomb failure criterion. ConclusionsThis study presents different techniques to characterize a self-setting calcium phosphate cement and provides experimental data on porosity, mechanical properties and failure. The investigated material possessed an open porosity at its dried state with negligible residual strains and its Young's modulus, obtained from micro-indentation tests, increased with hardening time. The failure loci may be described by a Mohr-Coulomb criterion, characteristic of soil and rock materials.

Preparation and Characteristics of Light Foam Cement

This present paper took ordinary Portland cement as main raw materials to prepare foam cement with properties, such as lightweight, high strength, and heat preservation, by the method of chemical foaming. The authors discussed the effects on the properties by key factors like water/cement ratio, foaming agents, foam stabilizers, accelerator and fibers of foam cement objects. Taken all the results show that in the condition that water/cement ratio of 0.48, foaming agents, foam stabilizers, accelerators and polypropylene fibers were adopted accounting for the quality of cement of 4.8%, 0.6%, 0.25% and 0.4% respectively, the characteristics of prepared formed cement samples could conform to the requirement of standard of JC/T266 formed cement.

Shrinkage characteristics of cement stabilized rammed earth

Among the most commonly studied properties of building materials, their strength and physical properties should be mentioned. There is, however, one more feature that exist at the border of these two areas and not taking it into account during the design process of a given building can lead to negative results. This is the susceptibility of the material to the phenomenon of shrinkage. The purpose of the research was to get to know the phenomenon of shrinkage of cement stabilized rammed earth in the context of its composition and changing environmental conditions, by examining such factors as: aggregate content, water/binding materials ratio, relative humidity of the environment RH [%]. For the purpose of the research four groups of samples were made that differed in mixture composition and curing conditions. Based on the results obtained, it was found that the shrinkage of rammed earth is larger than commonly used mineral composites. In addition, it is very sensitive to changes in composition, so it is recommended to continue research on composition optimization, taking into account not only strength and durability but also the phenomenon of shrinkage.

Fracturing and calcite cementation controlling fluid flow in the shallow-water carbonates of the Jandaíra Formation, Brazil

The shallow-marine carbonate rocks of the Jandaíra Formation have been subject to significant permeability variations through time due to various events of fracturing and calcite cementation. As a consequence, the Jandaíra Formation accommodated fluid flow only during specific moments in time. We reconstructed these episodes of fluid flow based on isotope characterizations and microscope characteristics of calcite veins and host rock cements. The Jandaíra Formation, which belongs to the post-rift sequence of the Potiguar Basin in northeast Brazil, was deposited from the Turonian onward until a marine regression exposed it in the Campanian. Due to the subaerial exposure, meteoric waters flushed out marine connate waters, leading to an event of early diagenesis and full cementation of the Jandaíra Formation. Fluid flow through the resulting impermeable carbonate formation appears to be closely related to fracturing. Fracturing in the Late Cretaceous induced a drastic increase in permeability, giving rise to extensive fluid circulation. Host rock dissolution associated to the circulating fluids led to calcite vein cementation within the fracture network, causing it to regain an impermeable and sealing character. In the research area, fluid flow occurred during early burial of the Jandaíra Formation at estimated depths of 400–900 m. This study documents the first application of fluid inclusion isotope analysis on vein precipitates, which allowed full isotopic characterization of the paleo-fluids responsible for calcite vein cementation. The fluid inclusion isotope data indicate that upwelling of groundwater from the underlying Açu sandstones provided the fluids to the fracture network. In Miocene times, renewed tectonic compression of a lower intensity created a secondary fracture network in the Jandaíra Formation. The density of this fracture network, however, was too low to induce a new episode of fluid circulation. As a result, this tectonic event is associated with the development of barren extensional fractures.