Local Cement Research Articles

Efficiency of local cement reinforcing antibacterial implants in surgical treatment of long bones chronic osteomyelitis

To present the results of treatment of long bones chronic osteomyelitis using local cement reinforcing antibacterial implant. The implant is made intraoperatively using polymethylmethacrylate. It was used in main group (n=30), while conventional treatment was applied in comparison group (n=30). Better early and remote outcomes were shown in main group including more effective and earlier suppression of infectious process, more than 2-fold decrease of recurrent infection incidence, minimization of risk of pathological fracture due to internal reinforcement, early recovery of extremity's function, creation of favorable conditions for bone structures restoration, substitution of post-resection bone defect and following organotypic reorganization of bone tissue.

Energy efficiency improvement potentials for the cement industry in Ethiopia

The cement sector is one of the fast growing economic sectors in Ethiopia. In 2010, it consumed 7 PJ of primary energy. We evaluate the potential for energy savings and CO2 emission reductions. We start by benchmarking the energy performance of 8 operating plants in 2010, and 12 plants under construction. The benchmarking shows that the energy intensity of local cement facilities is high, when compared to the international best practice, indicating a significant potential for energy efficiency improvement. The average electricity intensity and fuel intensity of the operating plants is 34% and 36% higher. For plants under construction, electricity use is 36% and fuel use 27% higher. We identified 26 energy efficiency measures. By constructing energy conservation supply curves, the energy-efficiency improvement potential is assessed. For the 8 operating plants in 2010, the cost-effective energy savings equal 11 GWh electricity and 1.2 PJ fuel, resulting in 0.1 Mt CO2 emissions reduction. For the 20 cement plants expected to be in operation by 2020, the cost-effective energy saving potentials is 159 GWh for electricity and 7.2 PJ for fuel, reducing CO2 emissions by about 0.6 Mt. We discuss key barriers and recommendations to realize energy savings.

Significant cost-push factors in owner-built incremental housing construction in Tanzania

The owner-built incremental housing approach is highly prevalent in developing countries although its economic rationale is questionable. This study uses descriptive statistics and regression analysis to examine the flexibility of owner-built housing construction cost in response to different cost-push factors based on survey data on 43 main and 20 outbuilding projects implemented in Dar es Salaam Tanzania between 1990 and 2013. It has been observed that factor cost-flexibility of incremental construction is significantly enhanced through longer construction periods, the use of local cement and drainage system materials and larger built space. This flexibility is explained by the owner-builders’ ability to internalize these cost-push factors over time which is reflected through lower annual construction costs facing owner-builders even at times of shortage in services and material supply, cost underestimation or high interest rate. These observations suggest that longer construction periods not only offer the cost-spread advantage but also allow a more thorough search for appropriate plot location, cheaper sources of materials, more affordable design and an appropriate match between changing life cycle housing needs and household income. Therefore, the incremental owner-built approach has lower annual construction costs not only because of the cost-spread effect of a longer construction period but also as a result of owner-builders’ cost-saving choices made in terms of utilization of certain local materials, purchasing plots in less challenging environments, preferring single-storey over two-storey houses and avoiding complex house design.

Subsurface seepage dynamics and flow types in a Messinian paleoseep system (Maiella Mts., Central Italy)

Abstract The subsurface feeder complexes of mud volcanoes and seepage systems potentially provide valuable information on the evolution of seepage dynamics. Ancient seepage systems in outcrops allow for the observation of expulsion features, which are otherwise commonly beyond seismic resolution. In the Maiella hydrocarbon seep area, the evolution of fluid migration through the sedimentary column during the Messinian Salinity Crisis generated distinctive seep-plumbing features, geological responses, and geochemical signatures in the “Brecciated Limestones” unit. The fluid migration pathways evolved from funnel-shaped feeder channels (Flow-mobilized Sediments) into hydrofractured microbial carbonate buildups (Limestone Buildups), and finally into blow-out micropipes in the host sediment (Patchy Limestones), as overpressure dissipated through the plumbing system. The Flow-mobilized Sediments (δ13C down to − 24.5‰ PDB-1) correspond to the highest flow rates in the whole area, whereas the Patchy Limestones (δ13C down to − 39.3‰ PDB-1) correspond to the slowest flow rates within the intrusive zone. The Limestone Buildups show different degrees of hydrofracturing that reflect different flow rates (δ13C down to − 27.5‰ PDB-1). The fluid transport mechanisms evolved from focused venting through neoformed feeder channels, where sediments elutriated from depths were carried out (the sediment-prone response to fluid migration), to high-rate seepage triggering high hydrofracturation in the microbial buildups. While the hydrocarbon-rich fluids contemporaneously triggered authigenic precipitation (the mineral-prone response to fluid migration), progressive upward and lateral flow deceleration resulted in gradually weaker hydrofracturing of the microbial buildups and finally only local cementation in the form of carbonate patches within the host sediments.

Historical trends and sources of TSP in a Sonoran desert city: Can the North America Monsoon enhance dust emissions?

In this work, the trends of total suspended particulate matter (TSP) were analyzed during a period of 12 years (2000–2012) on the basis of meteorological parameters. The results of historical trends of TSP show that post-monsoon dust emission seems to be connected to rainfall distribution in the urban environment. Particulate matter is dominated by plagioclase, quartz, calcite, and montmorillonite phases with barium sulfate, and particles enriched in Cu, Fe, and Ce. Elemental composition and principal component analysis allow the identification of two major sources for metals incorporated in geogenic dust: cement, and traffic. Geochemical analysis of non-mobile trace elements show a similar signature as local cement brands in TSP filters, but it remains unknown if such a signature is related to cement production, erosion of buildings, or construction activities. La–Ce geochemical tracers show that geogenic dust is an important media of transportation for traffic, and cement-related contaminants.This work highlights the importance of monsoon season precipitation in dust generation in arid urban environments, and it could contribute to regional studies including the southwestern US regarding the dust emission processes and transport of pollutants across the trans-boundary.

Konfrontasi Malaysia Indonesia (Malay Version)

Cement is used as the primary sealant in oil and gas wells throughout the world and is manufactured to meet specific chemical and physical standards set up by the American Petroleum Institute (API). As a result, oil companies purchase cement manufactured according to specification of API for its oil well cementing. These special classes of cements are called Oil Well Cements (OWCs). In oil well cementing, less error is tolerated in the performance of the cement used as compared to conventional cementing work. This has resulted in more attention being placed on the usage of high grade API special class of cements as against any ordinary type of cement. However, there are some cementing operations that Construction Grade Cements (CGCs) have been used without resulting in any cementing challenges. This paper presents the progressions in experimental investigations and field applications of CGCs in oil well cementing. The experimental investigations on the physical properties such as thickening time and rheological properties revealed that local cements in its natural state lack sufficient technical properties for oil well cementing. However, with the right addition of oil well additives, local cements have proven to have the required technical properties for oil well cementing. Countries like Vietnam and Thailand have demonstrated the field applications potentials of CGC. Comparing the cost of CGCs and OWCs (imported), it is realised that more savings are made when CGCs are used in cementing operations.

Comparative Study of Local Cements with Imported Class G Cement at Different Temperatures for Oil Well Cementing Operations in Ghana

The purpose of this research is to determine the suitability of local cements as an alternative to imported class G cement at different temperatures using oil well cement additives. Laboratory investigations on both local and imported cements to determine physical properties such as thickening time, fluid loss, compressive strength, free fluid and rheology were conducted at bottom hole circulating temperature of 27°C (80°F) and 66°C (150°F). The results indicated that locally manufactured cements are compatible with oil well cement additives at 80°F and 150°F and can be used as an alternative to imported class G cement in oil and gas well cementing operations. However, premature gelations of test results were phenomenal at 66°C (150°F) for the entire locally manufactured cements especially sample CEM B. Therefore, for local cements to be used effectively for cementing high temperature operations, stringent quality control during their manufacturing process is imperative.

相位校正器粘接局部应力控制技术

相位校正器粘接局部应力控制技术

Effect of Preparation Taper, Height and Marginal Design Under Varying Occlusal Loading Conditions on Cement Lute Stress: A Three Dimensional Finite Element Analysis.

To assess the effect of preparation taper, height and margin design under different loading conditions on cement lute stress. A 3-D FE model of an upper second premolar and molar was developed from CT scan of human skull using software programmes (MIMICS, Hypermesh and ANSYS). 10° and 30° taper, 3 and 5 mm preparation height and shoulder and chamfer finish lines were used. Type 1 Glass ionomer cement with 24μm lute width was taken and the model was loaded under 100N horizontal point load, vertical point load distributed axial load. The maximum shear stress and Von Mises stress within the cement lute were recorded. The maximum shear stresses ranged from 1.70 to 3.93 MPa (horizontal point loading), 0.66 to 3.04 MPa (vertical point loading), 0.38 to 0.87 MPa (distributed loading). The maximum Von Mises stresses ranged from 3.39 to 10.62 MPa (horizontal point loading), 1.93 to 8.58 MPa (vertical point loading) and 1.49 to 3.57 MPa (distributed loading). The combination of 10° taper and 5mm height had the lowest stress field while the combination of 30° taper and 5mm height had the highest stress field. Distributed axial loading shows least stress, better stress homogenization and gives a favorable prognosis for the fixed prostheses. Smaller preparation taper of 10° is biomechanically more acceptable than a 30° taper. It is desirable to decrease taper as height increases. The chamfer margin design is associated with greater local cement stresses toward the margins that could place the cement at greater risk for microfracture and failure.

The Success of the Backward Integration Policy in the Nigerian Cement Sector

The consumption of cement in Nigeria has increased to 18.5 million metric tonnes per annum (MMTPA) due to rapid urbanization and industrialization. Despite the huge demand for cement in Nigeria, domestic production was unable to meet the demand; hence the country relied on importation of cement to meet domestic construction needs. In 2002, the government adopted and implemented the backward integration policy (BIP), which requires cement import licenses be allocated only to importers who show proof of building factories for local cement manufacturing in Nigeria. Incentives under the policy include waiver of VAT and custom duty for importation of cement production equipment. The aim of this paper is to access the effect of the policy on the cement sector in Nigeria ten years after implementation. Following the implementation of the BIP, all the moribund existing government owned cement plants were privatized, while the private sector installed additional production and bagging capacities. Results showed that before BIP, Nigeria had an installed capacity of 4.03 MMTPA, but producing only 2 MMTPA. But 10 years after the implementation of the BIP, the country now produces 28 MMTPA with a total installed production capacity of 45 MMTPA and bagging capacity of 27.7 MMTPA, while additional 14 cement production plants of various capacities are under construction. Now that Nigeria has become self-sufficient in cement production, with domestic production exceeding the country’s need, additional policies that would address the new challenges of the cement sector particularly cement glut is required.

Application of k 0-based internal mono-standard PGNAA for compositional characterization of cement samples

The k 0-based internal mono-standard prompt gamma-ray neutron activation analysis (IM-PGNAA) method was used for compositional analysis of a cement standard provided by the International Atomic Energy Agency as a part of inter-laboratory comparison exercise. The PGNAA was also applied to a local cement sample for comparison purpose. The concentration ratios of elements with respect Ca were determined using the internal mono-standard method. The concentration ratios were then converted to the absolute concentrations by determining concentration of Ca in the cement using relative method. Concentrations of 11 elements were determined in both sample and standard of cement. The results of cement standard are found to be in good agreement with the certified values. The uncertainties on the elemental concentrations were in the range of 5–10 %.

Destruction of concentrated chlorofluorocarbons in India demonstrates an effective option to simultaneously curb climate change and ozone depletion

Abstract The Montreal Protocol aims to protect the stratospheric ozone layer by phasing out production of substances that contribute to ozone depletion, currently covering over 200 individual substances. As most of these compounds are synthetic greenhouse gases, there is an opportunity to curb both ozone depletion and climate change simultaneously by requiring Parties of both the Montreal and the Kyoto Protocol to destroy their existing stocks of concentrated chlorofluorocarbons (CFCs). Many emerging countries still possess stocks which need to be destroyed in an environmentally sound manner but costs may be prohibitive. The UNEP Technology and Economic Assessment Panel identified in 2002 eleven destruction technologies which meet the criteria for environmentally sound destruction of chlorofluorocarbons. Cement kilns were among these, but no study has been reported in scientific literature assessing its destruction performance under real developing country conditions up to now. In contrast to incinerators and other treatment techniques, high temperature cement kilns are already in place in virtually every country and can, if found technical feasible, be retrofitted and adapted cost-efficiently to destroy chemicals like CFCs. India has the second largest cement industry in the world and several hazardous waste categories have been tested successfully in recent years. The objective of this study was to carry out the first full scale demonstration involving high feeding rates of concentrated CFC-gases in a local cement kiln and to assess its feasibility and destruction performance. The test in Madhya Pradesh demonstrated that the kiln was able to destroy several concentrated CFC-gases effectively in an irreversible and environmental sound manner without causing increased releases of HCl, HF or PCDD/PCDF. The destruction and removal efficiency was >99.9999% and the overall environmental performance in compliance with Indian regulation and international best practice. The test also revealed that cement kilns have a much higher disposal capacity than previously anticipated and that such undertaking can contribute significantly to reduce the release of both ODS and greenhouse gases; the destruction of 16.3 tonnes of CFCs done in this demonstration is equivalent to saving the release of 131,265 tonnes of CO2 to the atmosphere.

Experimental and Theoretical Study of Minimum Fluidization Velocity and Void Fraction of a Limestone Based CO2 Sorbent

Abstract Calcium looping is a promising technology for CO2 capture as it may reduce considerably the energy penalty represented by the capture system. The CO2 capture efficiency will strongly depend on the reactor configuration, solids residence time and thermal operation. As these parameters are also interdependent, the impact on the process can be better understood by process modelling and flow modelling. Use of model results can be very valuable in the design of the process. Properties such as minimum fluidization velocity and void fraction related to limestone particles are important parameters for process simulations as well as for simulations of flow behaviour in the reactor. Limestone (calcite) with a high content of CaCO3 can be a good sorbent material as it is readily available at low cost. Limestone from a local cement plant was used in this study. The material which had been pre-crushed in a mill at the plant was classified into four different size classes: 120-150 μm, 150-180 μm, 180-300 μm and 300-500 μm. A lab-scale fluidized bed made in plexi-glass, with a diameter of 146 mm and a uniform air distribution, was used to determine the properties of the sorbent. Four separate experiments were run for each group of particles. The minimum fluidization velocity and the related void fraction were then determined. Multiphase flow simulations were then carried out, using the computational fluid dynamics (CFD) software BARRACUDA®. The simulation results compared reasonably well with the experimental results.

Adsorption of Fluoride on the Raw and Modified Cement Clay

AbsctractAdsorption of fluoride (F) on the raw and modified local cement clay was investigated by batch method. Modified clays were prepared through calcination, using the Na and Mg saturated (C‐Na, C‐Mg) clay at 500 and 850°C (C‐500, C‐850) and calcination of Mg incorporated clay at 500°C (C‐Mg‐500). The equilibration time was attained in 5 h. Adsorption of F increased with increasing adsorbent dose. Decrease of the initial F concentration resulted in an increasing amount of F adsorption. F adsorption isotherms fitted well with both Freundlich and Langmuir models. Low F adsorption was obtained on the raw, incorporated or calcined clays. However maximum F adsorption was found for C‐Mg‐500, with Kf and Q0 values of 0.27 and 1.69, respectively. This work indicated that the calcination of incorporated clay with Mg increased the F adsorption significantly, due to increased and stabilized positive sites.

Properties of Crumb Rubber Mixed in Local Thailand Soil Cement Brick Composites

This work presents a study on the investigation of recycled waste tyre (crumb rubber) as aggregate in the combination of local soil-cement brick. The purpose is to develop a lightweight brick with low thermal conductivity that can produce as low cost materials in local area of Thailand. The different amount of crumb rubber particles at 0, 10, 15, 20, 25, 30 and 40% were replaced to local Ratchaburi soil by weight and then mixed with a constant of Portland cement content at 10%. The mechanical properties were studied and indicated that a significant reduction in sample unit weight, there by resulting in a reduction of compressive strength and flexural strength. The results show that the presence of air voids and crumb rubber particles in the matrix can increase the water absorption but decrease the thermal conductivity. However, according to ASTM indicates that this hybrid material can be used as non-load bearing concrete masonry units (2.45 MPa) and is also suitable for construction as low cost and low energy consumption house in Thailand.

Develop High-Strength Concrete of C60 with Local Raw Material

High-effect concrete of C60 was made up by local cement of po42.5 and polycarboxy late super plasticizer through activity of the slag powder and the fly ash. Orthogonal test researches show that C60 adding higher activity index can be made, and it was characteristics of low cost, materials convenience and fine durableness.

APLICATION OF LOCAL CEMENT FOR CEMENTING OIL WELLS IN THE SOUTH EASTERN REGION OF THE PANNONIAN BASIN

<p>Wells conditions are different in wide range of temperature and depth. Cement slurries in such conditions have to remain pumpable and after setting to stay homogenous in production well life. For cementing operations in wide range of temperature and pressure and to accommodate cement slurries for individual well requirements more than 50 additives are now used for various API classes of cement. Laboratory in NIS – National oil company of Serbia, provides cement analysis of dry cement, tests on cement slurries and cement stone in compliance with methods prescribed by API standard, whereby quality and type of equipment fully meet the requirements. Adaptation of the local cement to the well conditions had already been done by these additives and by numerous tests of pure cement and cement mixtures we developed a palette of typical cement mixtures for cementing oil wells in the south eastern region of the Pannonian basin.</p>

Reactivity of Granulated Blast Furnace Slag

Abstract The Algerian iron and steel complex of El Hadjar, near the city of Annaba, produces a granulated blast furnace slag (GBFS) mainly used by the local cement factories as an addition to clinker of up to 30 % as maximum content, for manufacturing a compound CEM II type cement (Algerian Standard). With the aim, on the one hand, of limiting the use of high clinker content in Algerian cement plants and replacing it with other constituents such as granulated blast furnace slag and, on the other hand, to use this slag as an addition to local concrete, we have attempted to characterize it according to its degree of reactivity. The use of chemical activity indexes and caustic soda tests lead to disappointing results that are contradicted by the results obtained on mortar within the scope of the standard determination of a hydraulic efficient index. The results obtained indicated that the classification of El Hadjer slag strongly depends on its degree of fineness; it also has weak short-term activity, denoting a slower kinetics of reaction compared to classical slag. These results permit us to recommend a minimal Blaine of 3500 cm2/g for this slag. A more intensive use of this slag in cement and concrete is undoubtedly possible, but this must be demonstrated by conducting tests on mortar and validating by a study on concrete.

Assessment of radioactivity and the associated hazards in local cement types used in Tamilnadu, India

Activity concentration of 232Th, 226Ra and 40K in local cement types has been measured using NaI (Tl) gamma spectrometry. The radium equivalent activity (Raeq) of the samples was calculated and compared with similar data reported in the literature. The comparison has revealed that Raeq values obtained fall far below the criterion limit specified for building materials. The potential radiological hazard of the different samples was estimated using different approaches: representative level index and annual dose limit (dose due to gamma radiation inside the room and inhalation of radon). The estimated representative level index for all the samples is less than unity (the upper limit) indicating that the associated gamma radiation level is low. The annual dose limit falls within 0.167mSv to 0.603mSv, which is an order of magnitude below the criterion limit specified for building materials in the literature.

Analysis of the contribution of imported and locally manufactured cement to the growth of gross domestic product (GDP) of Nigeria (1986 2011)

This study attempted to examine the trends of supply and consumption of cement in Nigeria with a view to assessing the prospects of the shift of emphasis from cement import to local cement production and its effect on the economy. Data were generated through the secondary sources and Ordinary Least Squares (OLS) used to fit the models. The adequacy of the fitted models was tested using Augmented Dickey Fuller tool. The study noted that Nigeria is abundantly endowed with the basic inputs into cement manufactured with the exception of gypsum which occurs in thin-vein layers. The study revealed that the demand for cement in Nigeria is derived from the demand for residential and non-residential construction and that residential housing is by far the largest segment of cement consumption. The study also revealed that both locally manufactured cement and imported cement contributed positively to the Gross Domestic Product. This study has suggested the strategies and measures that Nigeria needs to put in place so as to become self sufficient and exporter of cement. The backward integration policy of Government will be a veritable tool for harnessing comparative strength in the production of cement in order to stimulate growth in the industry. This, however, depends on Government being able to address the issues of policy inconsistency, high energy cost, high cost of electricity and detrimental approach to deregulation. Key words: Cement supply and consumption, imported cement, local cement, Nigerian economy, backward integration policy.