Ceramic Powder Mixture Research Articles

Achieving efficient hardfacing on stainless steel using single SiC powder in laser directed energy deposition

Generally, in a laser hardfacing process, a mixture of ceramic and metal powder is used to clad a hard surface, resulting in enhanced wear characteristics of metal parts. This study proposes an efficient hardfacing process that uses a single and minimal amount of ceramic powder (0.079 g/min in this work). This process, named as Laser Directed Energy Deposition of Minimal Ceramic Powder (LDED-MCP), features that the melt pool is generated inwardly because only the substrate participates in forming the melt pool. Furthermore, due to the minimal powder flow rate used and sparse particle-melt pool collision events, ripple formations leading to the convective melt pool flow and inhomogeneous microstructures would be suppressed. Consequently, the produced layer is nearly flat and free of incompletely melted metallic particles, thus minimizing post-machining. For a 316 L substrate and SiC powder material combination, a crack-free layer about 560 μm thick with an average hardness of about 417 HV was created through process parameter optimization. This layer showed a eutectic structure composed of γ-austenite and chromium carbides, partially melted SiC particles between dendrites, and in-situ synthesized SiC nanoparticles decorating the cell walls. Through this work, near-net-shape hardfacing of stainless steels is realized through LDED-MCP process minimizing powder pre-processing and post surface machining.

Effects of mono and binary recycled aggregates on the rheological properties of geopolymer mortars synthesized with construction and demolition waste-based binders

This study comprehensively investigated the effect of different types of fine construction and demolition waste (CDW)-based aggregates, including recycled concrete aggregate (RCA), recycled ceramic tile aggregate (RTA) and recycled brick aggregate (RBA) on the fresh rheological properties of geopolymer mortars (GPMs) derived from CDW-based aluminosilicate binders. The results were compared to those of silica sand (SSA) and natural sand (NSA) with equivalent particle size distribution. In addition, the binary inclusion of RCA, RTA and RBA with 50% SSA or NSA fine aggregates was also considered in an attempt to reach rheological behavior closer to that of SSA and NSA-based GPMs. All mortars were blended with a CDW-binder composed of a ternary mixture of brick (RBP), ceramic (RTP) and concrete waste (RCP) powders optimized at pre-targeted chemical parameters of SiO2/Al2O3 and Na2O/SiO2 of 5.7 and 0.18, respectively. The geometrical shape parameters and packing densities of RCA, RTA, RBA, SSA and NSA aggregate skeletons and geopolymer mortar systems were also evaluated to examine their relationship with the rheological parameters of static and dynamic yield stresses, apparent and plastic viscosities, shear stresses and strains and thixotropy of GPMs. Although the incorporation of CDW-based aggregates resulted in enhanced rheological parameters, they exhibited shear-thinning or pseudoplastic behavior similar to SSA and NSA-GPMs. Yet the addition of RCA with a lower consumption of suspending fluids and reduced non-colloidal interactions than RBA and RTA resulted in overall rheological properties closer to those of SSA and NSA-GPMs, which further improved when combined with SSA or NSA in binary-aggregate-based GPM systems.

The Effect of Oyster Shell Powder on the High-Temperature-Properties of Slag-Ceramic Powder-Based Geopolymer.

There is a lack of scientific understanding of adding an oyster shell powder (OSP) to geopolymer concrete. The purpose of this study is: (1) to evaluate the high-temperature resistance of the alkali-activated slag ceramic powder (CP) mixture added with OSP at different temperatures, (2) to address the lack of application of environmentally friendly building materials, and (3) to reduce solid waste of OSP pollution and protect the environment. OSP replaces granulated blast furnace slag (GBFS) and CP at 10% and 20% (based on binder), respectively. The mixture was heated to 400.0, 600.0, and 800.0 °C after curing for 180 days. The results of the experiment are summarized as follows: (1) The thermogravimetric (TG) results indicated that the OSP20 samples produced more CASH gels than the control OSP0. (2) As the temperature increased, the compressive strength and ultrasonic pulse velocity (UPV) both decreased. (3) Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results reveal that the mixture undergoes a phase transition at 800.0 °C, and compared with the control OSP0, OSP20 undergoes a different phase transition. (4) The size change and appearance image results indicate that the mixture with added OSP inhibits shrinkage, and calcium carbonate decomposes to produce off-white CaO. To sum up, adding OSP can effectively reduce the damage of high temperatures (800.0 °C) on the properties of alkali-activated binders.

DISPLAYS OF UNBEARABLENESS OF STOMATOLOGICAL MATERIALS ARE IN CAVITY OF MOUTH (CLINICAL CASE)

Intolerance of dental materials is a rather problematic issue in modern orthopedic dentistry. Therefore, one of the important points in the diagnosis of individual sensitivity is the collection of an allergic history and the use of specific and non-specific tests. The purpose of this work is to highlight a clinical case of intolerance to dental materials, predict and prevent negative reactions using tests to determine individual sensitivity.
 Object and research methods. Patient P. who was born in 1968, complained of pain, redness and swelling in the area of the gums, itching, burning sensation in the oral cavity. From the anamnesis of patient P., it became known that she was treated in a private dental clinic in Kharkiv in February 2022, where all-cast bridge prostheses with ceramic lining were made and fixed. The patient began to present all the abovementioned complaints already on the fifth day after fixing the bridge-like structures in the oral cavity. But in connection with the beginning of hostilities, she was unable to consult a dentist due to the necessity of evacuation. An objective examination of the oral cavity revealed the following: diffuse hyperemia and swelling of the gums were observed in the area of attachment of the bridge-like structures. During palpation, the gums are sharply painful, when probing they bleed easily.
 Taking into account the fact that patient P. associates the symptoms of this disease with the fixation of bridge-like prostheses and taking into account the clinical picture in the oral cavity, we made a diagnosis of intolerance to dental materials and decided to remove these structures. After that, patient P. consultated with periodontist and allergist. 14 days after final treatment at the periodontist, the patient referred to the orthopedic dental clinic. During objective examination of the oral cavity of the patient P., it was established: the mucous membrane is pale pink without visible pathological changes, there is no hyperemia and swelling of the gums. The patient has no complaints.
 For the further treatment of patient P, it is recommended to make one-piece bridge-like prostheses with ceramic lining. For metal frames, we plan to use cobalt-chromium alloy Co-Cr alloy for ceramic, BeGo, produced in Germany . Therefore, we prepare a cobalt-chromium alloy chip in advance, which we mix with a drop of photopolymer restorative dental adhesive during the test. After that, this mixture is applied around the neck of one of the supporting teeth and polymerized. To evaluate the results of the tissue reaction, we appoint the patient to appear in 72 hours. During an objective examination of the oral cavity, we note that the mucous membrane around the neck of the abutment tooth is pale pink in color, without pathological change.
 We conduct a similar test for individual sensitivity to Duceram Kiss, Degudent ceramic mass, manufactured in Germany, which we plan to use for lining frames. Prepare a mixture of ceramic mass powder and a drop of dental adhesive. After 72 hours, we observe the results of the reaction of tissues adjacent to the neck of the abutment tooth, and we conclude that the test is negative. We plan to fix bridge-like structures on Fuji-1 glass ionomer cement, manufactured in Japan. Therefore, to conduct a study on the compatibility of the fixation material in the oral cavity, we prepare a mixture containing mixed fixation cement and dental adhesive. We observe for three days and conduct an analysis. In this case, the test is also negative. The conducted studies on the compatibility of structural materials and fixation cement give us the reason to recommend them for further prosthetics of patient P. After fixation of metal-ceramic bridge prostheses in the oral cavity, the patient was recommended to be examined by a dentist after 14 days and after one month. Long-term results of the examination of the oral cavity of patient P. confirmed the correct choice of materials for prosthetics and fixation.
 Conclusion. The clinical case of diagnosing the intolerance of dental materials indicates the need to conduct a study of a potential prosthesis carrier for compatibility with structural and fixation materials.

Direct laser melting of Al2O3 ceramic paste for application in ceramic additive manufacturing

We develop the direct laser melting of ceramic paste technology for application in ceramic additive manufacturing (AM). The Al2O3 ceramic paste, which is a homogeneous mixture of DI-water and Al2O3 ceramic powders, was deposited on an Al2O3 substrate using free-forming extrusion (FFE), and subsequently melted by a CO2 laser. To better control the laser melting process, the flow behavior of the laser-melted Al2O3 was investigated by evaluating the microstructure of the laser-melted Al2O3 single tracks. When the laser scanning speed increased from 1 to 3.5 mm/s at a fixed laser power, the permeation of the molten Al2O3 into the surrounding porous paste was reduced, resulting in the improvement of the surface uniformity of the laser-melted Al2O3 tracks. Through optimizing the laser scanning strategy, a fully-dense Al2O3 layer with smooth surface was achieved. The phase composition and density of the laser-melted Al2O3 layers were evaluated to study their properties. The thickness of the dense Al2O3 layer varied from ∼90 μm to ∼120 μm periodically due to the line-by-line scanning of the Gaussian laser beam. In addition, the relationship between the melting thickness and the laser scanning speed was also investigated to further improve the controllability of the laser melting process. This direct laser melting of ceramic paste technology is promising for applications in ceramic AM, such as 3D printing of ceramic components and high-temperature ceramic welding.

Role of Mixing Method and Solid Content on Printability of Alumina Inks for Stereolithography 3D Printing Process

Additive manufacturing of ceramics via stereolithography method is a promising way to fabricate high-resolution ceramic parts with complex geometry, which is hard to obtain with traditional ceramic shaping methods. In order to shape the ceramics with the Digital Light Processing (DLP), a mixture of photocurable resin and ceramic powders, called ink, must be prepared. In this paper, the printability of the Alumina-glass inks, with different solid contents were prepared by two mixing methods, having long and short mixing durations. In order to evaluate the printability of inks, the rheological behavior of suspensions was investigated, and printing parameters such as curing time and layer thickness were changed. The ceramic-resin suspensions were prepared via 24-hour ball-milling and 10,000 rpm mechanical homogenizing. The suspension containing 60 wt% solid content and prepared by mechanical homogenizing showed the best stability with 8% sedimentation within 4 days and the lowest viscosity of 1.37 Pa·s at shear rates of 30 s-1, exhibiting a suitable viscosity for DLP printing. Therefore, a mechanical homogenizer can be a promising and quick method for mixing by providing simultaneously appropriate rheology and printability.

Catalytic Co-Cracking of Used Cooking Oil Methyl Ester and Polystyrene Waste for Gasoline-Rich Biofuel Over Mesoporous Al-MCM-41 Catalyst

Used cooking oil and packaging foam are typical waste materials that are abundantly available as household and fast food restaurant waste with high energy content, thus representing potential feedstock for conversion into an alternative energy source. In this study, catalytic co-cracking was examined at 300°C in atmospheric pressure to generate fuel products with gasoline-like properties from a mixture of used cooking oil biodiesel and polystyrene pyrolysis oil. Mixture of ceramic powder and Al-MCM-41 was used as catalyst in comparison to a pristine mesoporous aluminosilicate material. The product distribution of produced biofuel wes analyzed by gas chromatography – mass spectrometry. Experimental results exhibit that catalytic co-cracking process generated up to 64,6 – 67,2% yield of liquid hydrocarbon. The product distribution and the quality of the resulting biofuel were significantly affected by Si/Al ratio of the catalyst. Pristine Al-MCM-41 with lower Si/Al ratio was more favored for the enrichment of gasoline range fraction (C7–C12) which give 88,98% yield, while Al-MCM-41/ceramic with higher Si/Al ratio only give 32,84% yield of gasoline fraction. Moreover, lower oxygenate compound with better stability of biofuel was also obtained using pristine Al-MCM-41 catalyst. The produced biofuel blend by both catalysts indicated promising physical properties including higher calorific value (53,2 and 52,4 MJ/kg) and higher-octane number (RON 99,8 and 95,5) than commercial gasoline.

Manufacturing of Clayey Bricks by Synergistic Use of Waste Brick and Ceramic Powders as Partial Replacement of Clay

Clay bricks are extensively used as building material worldwide. Natural soil deposits are in constant reduction due to the frequent use of clay to manufacture bricks. About 1600 billion bricks are produced annually by the consumption of millions of tons of natural resources. The prime focus of this study is to assess the feasibility of using a composite mixture of waste brick powder (WBP) and waste ceramic powder (WCP) as a replacement for depleting natural resource “clay” in brick manufacturing. Based upon the previous studies, the replacement levels were kept as (4 + 5)%, (8 + 10)%, and (12 + 15)% of WCP and WBP, respectively. The brick specimens were evaluated in terms of compressive strength, modulus of rupture, density, water absorption, efflorescence, apparent porosity, resistance to chemical attack and sulfate attack, and freeze-thaw resistance. The study reveals that about 27% of clay can be replaced with ceramic waste powder and waste brick powder, which can preserve a massive amount of natural clay without compromising the quality of the bricks.

New Perspectives on Zirconia Composites as Biomaterials

Zirconia–alumina composites couple the high toughness of zirconia with the peculiar properties of alumina, i.e., hardness, wear, and chemical resistance, so they are considered promising materials for orthopedic and dental implants. The design of high performance zirconia composites needs to consider different aspects, such as the type and amount of stabilizer and the sintering process, that affect the mechanics of toughening and, hence, the mechanical properties. In this study, several stabilizers (Y2O3, CuO, Ta2O5, and CeO2) were tested together with different sintering processes to analyze the in situ toughening mechanism induced by the tetragonal–monoclinic (t–m) transformation of zirconia. One of the most important outcomes is the comprehension of the opposite effect played by the grain size and the tetragonality of the zirconia lattice on mechanical properties, such as fracture toughness and bending strength. These results allow for the design of materials with customized properties and open new perspectives for the development of high-performance zirconia composites for orthopedic implants with high hydrothermal resistance. Moreover, a near-net shape forming process based on the additive manufacturing technology of digital light processing (DLP) was also studied to produce ceramic dental implants with a new type of resin–ceramic powder mixture. This represents a new frontier in the development of zirconia composites thanks to the possibility to obtain a customized component with limited consumption of material and reduced machining costs.

Investigation of the Properties of Heat-Protective Coatings to Improve the Performance of Products

The heat-loaded part of the combustion chamber of a liquid rocket engine are Considered. The proposed coating has several layers: an internal metal coating that contacts the part or substrate, and an external coating made of a mixture of ceramic granules and metal powder. At the same time, to obtain the initial surface for coating with the required surface layer roughness, it is proposed to use the method of sand blasting. The article analyzes possible mechanisms of material formation for "base-coating" transition zones, as well as the influence of their chemical composition on the adhesive strength of layers.. The choice of brand and combination of materials used for coating is justified. Technological modes that have been tested in production conditions when applying heat-resistant coatings to parts of modern rocket engines are proposed. The influence of technological parameters of the initial surface preparation process and the geometry of the resulting micro-relief of the substrate on the adhesion characteristics of a multilayer coating made of heat-protective materials operating in the high-temperature zone of the combustion chamber of liquid rocket engines is revealed.

Avgia Church (Batumi, Georgia)

The church discussed in the paper is situated in Avgia, on the outskirts of Batumi. It is an early Christian period hall-type church with northern and southern wings. The ground plan of the whole structure resembles the well-known layout of the croixlibre. The whole building is 23.85 m long and 19.0 m wide – including the arms. It has a projecting semi-circular apse whose radius is 6.05 m. The main space of the church is divided into three parts. It consists of a transverse hall, which may have operated as a narthex, a hall, and an altar apse. The floor of the structure was covered with pinkish lime mortar, a mixture of small pebbles and ceramic powder. The only central entrance to the church was located on the west side. The northern annex had an entrance in the north-western corner, and the southern one – in the south-eastern corner. The church seems to have been built of rubble stone. The construction style, layout, and archaeological evidence from the site narrow down its chronology to the 5th and 6th centuries AD.

Monte Carlo Simulation of the Cold Spray Process of Mixtures of Metal and Ceramic Powders

During cold spraying of ceramic and metal mixtures, there is an interaction between the ceramic and metal particles during the spray process; as a result, under certain conditions, a non-monotonic dependence of deposition efficiency on the content of ceramic particles in the initial powder mixture is observed. In the present work, a numerical Monte Carlo model is put forward for the first time to simulate such behavior of deposition efficiency. The calculation results were compared with the available experimental data. It is shown that, with a proper choice of the values of involved model parameters, one can invent an adequate quantitative description of both the behavior of the deposition efficiency of the mixture and the behavior of the ceramic content of the coating. Additionally, the effects of particle size, particle size distribution, and deposition efficiency of pure metal powder are discussed.

The role of the attrition milling on the grain size and distribution of the carbon nanotubes in YSZ powders

The aim of present work was the examination of the role of the high efficient attrition milling on the structure and grain size of ZrO2 – 8mol.% Y2O3 (YSZ) and on the distribution of multiwall carbon nanotubes (MWCNTs) in these powder mixtures. The microstructure of YSZ/MWCNTs powder mixtures with 1, 5, 10wt.% MWCNTs was investigated. Detailed study confirmed the YSZ grain size decrease and simultaneously the non-destructive homogenization of MWCNTs in the ceramic powder mixtures. The best homogenization degree was achieved in the case of YSZ/1wt.% MWCNT powder. Raman scattering measurements were performed to investigate the atomic bonding and structural integrity of carbon nanotubes. The presence of the G and D bands in each samples at ∼1590 and ∼1355cm−1 confirmed the unaffected structural integrity of MWCNTs after the milling process. In addition to Raman measurements the high resolution transmission electron microscopy (HRTEM) studies have shown that the structure of MWCNTs remains intact after milling.

Application of zirconia surface coating to improve fracture resistance and stress distribution of zirconia ceramic restorations

Zirconia ceramic restoration (ZCR) has a higher fracture incidence rate than metal ceramic restoration. Different surface treatments were used to improve fracture performance of ZCR such as grit blasting (GB) by aluminium oxide powder. This type of surface treatment generate residual stresses on veneering ceramic causing crack initiation and ending with a fracture. In order to overcome the stress generated by GB, zirconia surface coating is used as a surface treatment to improve fracture resistance and to accommodate stresses along the ZCR layers. Fifty zirconia ceramic crowns were fabricated and divided according to the type of surface treatment into three groups; the first group is (ZG), involving 20 cores were coated with a mixture of partially-sintered zirconia powder (PZP) and glaze ceramic powder; the second group is (ZL), including of 20 cores were coated with PZP and liner ceramic paste. The third group is grit blasting (GB), preparing of 10 fully sintered cores at 1350 °C which then abraded by 50 µm aluminium oxide powder. The groups ZG and ZL were further subdivided into ZG26, ZG47, ZL26 and ZL47 based on two PZP sizes (47 and 26 µm). Each treated core was veneered with the veneering ceramic layer. Fracture resistance (FR) was measured by the universal testing machine. Finite element analysis (FEA) was used to simulate the stress distributions on the coated and non-coated zirconia crown models. The ZG47 group had higher FR (647.92 ± 97.33 N) and a significant difference (P < 0.00) compared to GB and other coated groups. The FEA exhibited lower and evenly distributed stresses of the zirconia glaze model than the zirconia liner and the non-coated models. The ZG47 coating considered as an alternative method to GB treatment which increases the FR which significantly improved the clinical performance of the ZCR.

Influence of compacting times and pressures on rheological properties of alumina and quartz ceramic powder mixtures

In this research the compacting and rheological properties of alumina and quartz powder mixtures were examined depending on forming pressures and times. On the basis of the achieved relative compaction curves as function of forming pressure and time the authors could successfully describe the changes of rheological behavior and rheological model of these powder mixtures. With increasing the compression pressure of the alumina and quartz powder mixtures considerable changes of rheological properties could be observed.In this work the authors have shown how the compacting deformations of cylindrical specimens are depending on compaction pressures and times. On the basis of their research the authors could successfully illustrate also how the rheological behaviors and models of alumina-quartz ceramic powder mixtures are changing in the compacting die cavities at low values of forming pressures.

Effect of chromium additive on sintering and oxidation behavior of HfB2-SiC ceramics

The effect of chromium admixture on the processes in the HfB2-SiC ceramic powder system during its pressureless sintering at 1600 °C was studied. It was shown that an increase in chromium content from 0% to 15.5% in the HfB2-SiC ceramic powder mixture leads to a continuous increase in its relative density up to 90%. A transient liquid phase Cr-Si-C-B is formed at 1600 °C, and it promotes intense sintering of HfB2 and SiC powders. The oxidation resistance of HfB2-SiC-Cr ceramics was studied in static air at 1000–1500 °C. It was shown that the oxidation resistance is greatly improved due to a decrease in the porosity of the sintered ceramic system because of chromium additive. The presence of chromium oxide in the formed surface glassy layer can also lead to the increase in the oxidation resistance. These results suggest that chromium can be considered as a promising sintering additive for HfB2-SiC and similar systems.

Sintering of Nanocrystalline Multicomponent Zinc Oxide Varistor Powders Prepared by Ball Milling

Nanocrystalline ZnO–V2O5–MnO2–Nb2O5 varistor ceramic powder mixtures modified by different amount of Er2O3 addition (0-2 mol.%) have been prepared by high energy ball milling. Densification, microstructure and electrical characteristics of the ball milled precursor powders during isochronal sintering at 950 to 1250°C for 1 h as well as isothermal sintering for 0.25 to 2h at 1100°C have been investigated. Densification process is found to diminish slightly while growth of ZnO grain is reduced markedly with increasing Er2O3 addition due to the formation of Er-rich spinel phases at grain boundaries and triple points that restrict the grain boundary migration. It has been demonstrated that ultrafine grained multicomponent ZnO varistor ceramics can be achieved by simple conventional sintering via judicial selection of sintering time (≤ 1h) and temperature (≤ 1100°C) and amount of rare-earth oxide (Er2O3) addition (1.0 mol.%). ZnO varistor with 0.5 mol.% Er2O3 sintered at 1100°C for 0.5h exhibits best varistor property with breakdown field of 3880 Vcm-1.

Effect of new zirconia surface coatings on the surface properties and bonding strength of veneering zirconia substrate

Zirconia ceramic dental restorations showed a low bond strength to veneering ceramic because of there is no inherent glass content along with a nonpolar covalent bond in its matrix. Two zirconia coatings by airbrush spraying were used as a new surface treatment on zirconia substrate to create surface roughness and improved bond strength to the veneering ceramic. Unsintered yttria stabilized zirconia (YSZ) powder was partially sintered at 1100°C to produce powders with two particle sizes; A=26.0±0.3μm and B=47.0±0.5μm. Unsintered YSZ blocks were sectioned into 50 discs of 25mm in diameter and 2.5mm in thickness. The discs were divided according to the surface treatments into three groups; ten sintered YSZ discs were blasted by airborne particle abrasion (APA) with 50μm aluminium oxide particles as control group; twenty unsintered YSZ discs were coated with a mixture of glaze ceramic and YSZ powders (M1), and twenty unsintered YSZ discs were coated with a mixture of ceramic liner and YSZ powders (M2). Based on the sizes of the YSZ powders, the coated groups subdivided into M1A, M1B, M2A and M2B. The surface area roughness (Sa), surface morphology, elemental composition, phase transition and shear bond strength test (SBS) were assessed. The collected data were analysed with one-way ANOVA and Tukey HSD test at (P<0.05). The Sa results revealed significant differences among all groups (P<0.000). The coated groups showed higher Sa and SBS values with a significant difference than APA. The M1B group exhibited higher values of Sa (10.33μm) and SBS (37.54MPa) with significant differences among the other tested groups. The zirconia specimens treated with new coatings significantly improved the shear bond strength to the veneering ceramic.

Porous lead zirconate titanate ceramics with optimized acoustic properties for high-frequency ultrasonic transducer applications

Acoustic properties of porous PZT ceramics intended to be used as backing in high-frequency transducer applications are investigated using a novel method where an electroded piezoelectric thick film is deposited on the backing under test. Two backings with pore sizes 1.5 μm and 10 μm were obtained by sintering a mixture of ceramic powder and an organic template, their porosity was evaluated by scanning electron microscopy at 15%, leading to a density around 6.5 g/cm3. The electroacoustic impulse responses of these devices were measured considering the backing as a propagation medium, the initial thickness of which was chosen small enough to allow back-wall echoes to be detected and large enough to be able to separate the signals in time domain. Then the thickness of the backing was reduced (from around 2 mm to less than 1 mm) and the measurements were repeated. Acoustic properties were then deduced: attenuation coefficients reaching 4 dB/mm/MHz and group velocities around 3400 m/s were obtained, leading to an acoustic impedance around 22 MRa. Such combination of high attenuation and moderate acoustical impedance make these materials an interesting solution for high-resolution ultrasonic imaging transducers.

Replacement of Fine Aggregate by Mixture of Ceramic and Surkhi Powder in Concrete

Replacement of Fine Aggregate by Mixture of Ceramic and Surkhi Powder in Concrete