Investigation of Using Calcined Coal Gangue as the Co-Blended Precursor in the Alkali-Activated Metakaolin.

The feasibility and performance of using calcined coal gangue (CCG) to substitute metakaolin (MK) as the precursor to prepare alkali-activated materials (AAMs) were thoroughly evaluated by conducting combined experiments of flowability test, mechanical measurement, calorimetry and microstructure analysis, etc. It was found that the increased substitution ratio of CCG to MK can increase the flowability of the prepared paste by up to 28.1% and decrease its viscosity by up to 55.8%. In addition, a prolonged setting time of up to 31.8% was found with the increased substitution amount of CCG to MK, which can be attributed to the low reactivity of CCG compared to that of MK. Lastly, even though the presence of CCG can lead to a decrease in the early compressive strength of the hardened paste, a highly recovered long-term mechanical property can be found due to the continuous reaction of CCG. All of these results prove the feasibility of using CCG as one co-blended precursor with MK to prepare alkali-activated materials.

Influence of Admixture Source on Fresh Properties of Self-Consolidating Concrete.

The study presented herein was intended to (1) compare the optimum (minimum) dosage requirements of four different sources of polycarboxylate-based high-range water-reducing admixtures (HRWRAs) and viscosity-modifying admixtures (VMAs) in attaining slump flows of 508 mm, 635 mm, and 711 mm, and a visual stability index (VSI) of 0 (highly stable concrete) or 1 (stable concrete), and (2) assess the flowability/viscosity, stability, passing ability, and filling ability of the resulting self-consolidating concretes. The test results showed that the optimum dosage requirements to obtain a uniform slump flow and visual stability index varied among the four selected admixture sources. The required dosage amount for HRWRAs was highest for the polycarboxylate-ester (PCE) type and lowest for the polycarboxylate-acid (PCA) type. Acceptable flowability plastic viscosity dynamic and static stability, passing ability, and filling ability of self-consolidating concrete can be achieved with the proper dosing of the four studied admixture sources.

Investigation of an Increased Particle Size Distribution of Ti-6Al-4V Powders Used for Laser-Based Powder Bed Fusion of Metals.

This study investigates the potential benefits of integrating coarser particle size distributions (PSDs) of 45-106 µm into laser-based powder bed fusion of metals (PBF-LB/M), aiming to reduce costs while maintaining quality standards. Despite the considerable advantages of PBF-LB/M for producing intricate geometries with high precision, the high cost of metal powders remains a barrier to its widespread adoption. By exploring the use of coarser PSDs, particularly from electron beam-based powder bed fusion of metals (PBF-EB/M), significant cost-saving opportunities are identified. Through a comprehensive powder characterization, process analysis, and mechanical property evaluation, this study demonstrates that PBF-LB/M can effectively utilize coarser powders while achieving comparable mechanical properties as those produced with a 20-53 µm PSD. Adaptations to the process parameters enable the successful processing of coarser powders, maintaining high relative density components with minimal porosity. Additionally, market surveys reveal substantial cost differentials between PBF-LB/M and PBF-EB/M powders, indicating a 40% cost reduction potential for the feedstock material by integrating coarser PSDs into PBF-LB/M. Overall, this study provides valuable insights into the economic and technical feasibility of printing with coarser powders in PBF-LB/M, offering promising avenues for cost reduction without compromising quality, thus enhancing competitiveness and the adoption of the technology in manufacturing applications.

Gamma radiation-induced grafting of poly(butyl acrylate) onto ethylene vinyl acetate copolymer for improved crude oil flowability.

Ethylene vinyl acetate (EVA) copolymers are widely employed as pour point depressants to enhance the flow properties of crude oil. However, EVA copolymers have limitations that necessitate their development. This work investigated the modification of EVA via gamma radiation-induced grafting of butyl acrylate (BuA) monomers and the evaluation of grafted EVA as a pour point depressant for crude oil. The successful grafting of poly(butyl acrylate) p(BuA) onto EVA was verified through grafting parameters, FTIR spectroscopy, and 1H NMR spectroscopy. Treating crude oil with 3000 ppm of (EVA)0kGy, (EVA)50kGy, and (1EVA:3BuA)50kGy yielded substantial reductions in pour point of 24, 21, and 21 °C, respectively. Also, rheological characterization demonstrated improving evidenced by a viscosity reduction of 76.20%, 67.70%, and 71.94% at 25 °C, and 83.16%, 74.98%, and 81.53% at 12 °C. At low dosages of 1000 ppm, the EVA-g-p(BuA) exhibited superior pour point reductions compared to unmodified EVA, highlighting the benefit of incorporating p(BuA) side chains. The grafted EVA copolymers with p(BuA) side chains showed excellent potential as crude oil flow improvers by promoting more effective adsorption and co-crystallization with paraffin wax molecules.

Role of silicate-rich and silicate-less industrial solid wastes in the physicomechanical properties and durability of low quality metakaolin-blended cement.

Although calcined clay-blended cement offers higher performance and durability compared to neat Portland cement (PC), its extensive use of natural clay leads to the depletion of natural non-renewable resources. To address this concern, this study focuses on the utilization of supplementary cementitious materials-based waste products as a substitute for PC. The blended cement was optimized with a low replacement level of 10 wt.% calcined Fanja clay (FNJ) as a low-grade metakaolin (MK) and 90 wt.% PC. Various types of industrial solid wastes (ISWs) were incorporated into the PC-FNJ blend in place of PC. The ISWs utilized included silicate-rich wastes, such as silica fume (SF) and glass waste (GW) powder, as well as silicate-less waste, such as marble dust (MD). The results revealed that incorporating 10 wt.% SF into the PC-FNJ mixture resulted in a considerable decrease in the flow rate while improving its early mechanical strength. GW, as another silicate waste, also enhanced early mechanical properties but not as much as SF. However, the composite of PC-FNJ-GW exhibited higher workability than the neat PC, PC-FNJ, and PC-FNJ-SF. The mixtures of PC-FNJ-MD demonstrated the same trend. Embedding SF into PC-FNJ-GW and PC-FNJ-MD substantially decreased both their flowability and mechanical properties. Nonetheless, all composites containing ISWs showed higher flexural strength, higher resistivity to chloride diffusivity, and higher or comparable acid and salt resistivity.

Comprehensive investigation of recycled PVC powder.

This study constitutes a comprehensive investigation centred on comprehending the behaviour and characteristics of recycled polyvinyl chloride (PVC) powders. The overarching objective is to successfully conclude the initial research phase, during which PVC-coated fabric offcuts undergo a transformation into PVC powder while achieving complete separation from polyethylene terephthalate fibres. The study entails a qualitative description of the morphology of PVC powder particles, employing an optical microscope to distinguish the diverse shapes exhibited by these particles. The optical microscope observations of PVC powder reveal a distinct array of non-spherical particles characterized by flat, elongated shapes. These high-magnification images unveil the intricate morphological features of the particles, highlighting their irregular shapes. Subsequently, a quantitative analysis of PVC particle size distribution is performed, comparing results from optical microscopy with those obtained through mechanical sieving. The qualitative and quantitative findings obtained provide robust evidence supporting the correlation and confirm that most particles are smaller than 600 µm (93.6%) using an optical microscope and the sieving process (96.39%). The greatest fraction (83.44%) is in the size range between 200 and 600 µm. Assessing flowability, another significant aspect in the evaluation of powders, provides insights into its behaviour and interparticle interactions. The flowability results indicate a Compressibility Index of approximately 26.84%, which suggests poor flowability. This means that the powder is likely to encounter difficulties in flowing freely. This finding is in line with the Hausner ratio, which measures 1.37. This investigation of recycled PVC powder will offer insights into the potential applications and processing considerations of this powder. More concretely, the use of recycled PVC powder shows promise as a viable alternative to conventional PVC resin in plastisol formulations, offering the potential to maintain the properties of the final PVC product without adverse effects.

Free-Flowing Polymer-Bonded Powder Composition of Hexahydro-1,3,5-trinitro-1,3,5-triazine Using Solvent-Slurry Coating.

A number of coating techniques have been used to improve the processability of high explosives. These techniques are typically used for developing compositions, such as boosters and fillers. The most typically used technique is the "solvent-slurry coating". Several compositions of polymer-bonded explosives have been industrialized using this technique. The NUPC-6 polymer-bonded powder composition of hexahydro-1,3,5-trinitro-1,3,5-triazine is optimized using the solvent-slurry coating. It involved multiple processes, i.e., preparing a slurry of high explosives in an aqueous phase, dissolving the modified polymer binder in an organic solvent, maintaining both the solvent and slurry at controlled temperatures, introducing polymer binder solution and ingredients in the slurry, distilling the solvent, mixing contents homogeneously, filtering the polymer-coated hexahydro-1,3,5-trinitro-1,3,5-triazine composition, and drying in a vacuum oven. The phlegmatizing and hydrophobic agents enhance flowability and hydrophobicity. The mass flow rate, bulk density, tapped density, compressibility index, and Hausner ratio are determined to evaluate its flowability during filling operations. The results show that the composition is flowable using a filling funnel, with a 150 mm upper diameter, 25 mm flow diameter, and 136 mm total funnel height. The raw polymer binder was modified using diisooctylsebacate and SAE-10 oil. The additives in the composition enhance its flowability, and it might be used in underwater applications.

Experimental Study and Application of Controlled Low-Strength Materials in Trench Backfilling in Suqian City, China.

When backfilling narrow spaces, controlled low-strength materials (CLSM) can be used to achieve an effective backfilling effect. The pipeline engineering in Yahnghe Avenue of Suqian, China, provides a favorable on-site condition for the use of CLSM. However, no guidance exists for the determination of the material mixture ratio of CLSM for this geological condition. Laboratory tests were performed to investigate the basic physical parameters of excavated soil and the optimal mixture ratio of CLSM. Results indicate that the sand and silt account for 29.76% and 57.23% of the weight of excavated soil, respectively. As the water content increases (from 40% to 50%), the flowability of the CLSM approximately shows a linear increase (slumps values from 154.3 mm to 269.75 mm for 9% cement content), while its compressive strength shows a linear decreasing trend (from 875.3 KPa to 468.3 KPa after curing for 28 days); as the cement content increases (from 6% to 12%), the flowability approximately shows a linear decreasing trend (from 238.8 mm to 178.5 mm for 45% water content), while the compressive strength shows a linear increasing trend (from 391.6 KPa to 987.6 KPa after curing for 28 days). By establishing the relationship between compressive strength/flowability and the water-cement ratio, the optimal material ratio is determined to be 9% cement content and 40-43% water content. The engineering application results indicate that the use of CLSM can achieve efficient and high-quality backfilling effects for pipeline trenches. The findings of this research may provide a reference for the application of CLSM in fields with similar geological conditions.

Quantitative Analysis of the Physical Properties of Ti6Al4V Powders Used in a Powder Bed Fusion Based on 3D X-ray Computed Tomography Images.

The physical properties of Ti6Al4V powder affect the spreadability of the powder and uniformity of the powder bed, which had a great impact on the performance of built parts made by powder bed fusion technology. Micro-computed tomography is a well-established technique used to analyze the non-destructivity of the objects' interior. Ti6Al4V powders were scanned with micro-CT to show the internal and external information of all the particles. The morphology, particle size distribution, hollow particle ratio, density, inclusion, and specific surface area of the powder samples were quantitatively characterized, and the relationship of flowability with these physical properties was analyzed in this work. The research results of this article showed that micro-CT is an effective way to characterize these items, and can be developed as a standard method of powder physical properties in the future.

Impact of dry coating lactose as a brittle excipient on multi-component blend processability.

Previous work demonstrated the benefits of dry coating fine-grade microcrystalline cellulose (MCC) for enabling direct compression (DC), a favored tablet manufacturing method, due to enhanced flowability while retaining good compactability of placebo and binary blends of cohesive APIs. Here, fine brittle excipients, Pharmatose 450 (P450, 19 µm) and Pharmatose 350 (P350, 29 µm), having both poor flowability and compactability are dry coated with silica A200 or R972P to assess DC capability of multi-component cohesive API (coarse acetaminophen, 22 µm, and ibuprofen50, 47 µm) blends. Dry coated P450 and P350 not only attained excellent flowability and high bulk density but also heightened tensile strength hence processability, which contrasts with reported reduction for dry coated ductile MCC. Although hydrophobic R972P imparted better flowability, hydrophilic A200 better enhanced tensile strength, hence selected for dry coating P450 in multi-component blends that included fine Avicel PH-105. For coarse acetaminophen blends, substantial bulk density and flowability increase without any detrimental effect on tensile strength were observed; a lesser amount of dry coated P450 was better. Increased flowability, bulk density, and tensile strength, hence enhanced processability by reaching DC capability, were observed for 60 wt% ibuprofen50, using only 18 wt% of the dry coated P450, i.e. 0.18 wt% silica in the blend.

Improvement of the setting properties of mineral trioxide aggregate cements using cellulose nanofibrils.

Cellulose nanofibrils (CNFs) exhibit excellent mechanical properties and are used to reinforce various composites. The effects of incorporating CNFs into commercial mineral trioxide aggregate (MTA) cements (NEX MTA (NEX) and ProRoot® MTA (PR)) on the underwater setting properties, compressive strength, and flowability were estimated in this study. NEX mixed without CNFs disintegrated after water immersion. NEX mixed with CNF-suspended solutions showed good setting properties under water immersion and a similar compressive strength, which was kept in air (100% relative humidity). PR did not degrade after water immersion, regardless of the presence of CNFs, and no significant difference in the compressive strength caused by CNFs incorporation was detected. The relative flowability of the NEX mixture decreased with increasing CNFs content up to 1.0 w/v%. The application of CNF-incorporated MTA in various dental cases is promising because CNFs prevent the water-immersion-dependent collapse of some MTA cements immediately after mixing.

Geopolymer Materials for Extrusion-Based 3D-Printing: A Review.

This paper examines how extrusion-based 3D-printing technology is evolving, utilising geopolymers (GPs) as sustainable inorganic aluminosilicate materials. Particularly, the current state of 3D-printing geopolymers is critically examined in this study from the perspectives of the production process, printability need, mix design, early-age material features, and sustainability, with an emphasis on the effects of various elements including the examination of the fresh and hardened properties of 3D-printed geopolymers, depending on the matrix composition, reinforcement type, curing process, and printing configuration. The differences and potential of two-part and one-part geopolymers are also analysed. The applications of advanced printable geopolymer materials and products are highlighted, along with some specific examples. The primary issues, outlooks, and paths for future efforts necessary to advance this technology are identified.

Powder properties of carbon-based solid acid catalyst for designing cellulose hydrolysis reactor with stirring apparatus.

The powder properties of a carbon-based solid acid catalyst, an amorphous carbon material bearing SO3H, COOH and OH groups, were investigated for the hydrolysis of cellulose. The Carr flowability and floodability indices, the angle of internal friction (adherence), and the particle size distribution and shape for the powder catalyst were determined. The need to develop a special reactor with a stirring apparatus for the hydrolysis of cellulose was determined based on the Carr flowability index. Insight into the interaction or adherence between the catalyst and crystalline cellulose during the hydrolysis process was gained by measuring the internal friction angle. The optimum moisture content in the catalyst to achieve the maximum adherence was investigated.

Preparation and properties of the fine ground strontium-based endodontic cements.

In this study, fine powders of tristrontium aluminate (S3A) and distrontium cerate (S2Ce) cement were prepared using a dry grinding process, and their mechanical and ion dissolution properties were estimated. Fine cements showed the particles about 10 µm in diameter or smaller with sharp particle size distribution curves. The setting reaction of the fine cements was rapid; therefore, a 0.1% w/v of citric acid solution was used as the retarder. The compressive strengths of the fine cements were improved compared to those of the coarse cements at both 1 and 28 days after mixing at a water/powder ratio (W/P) of 0.4. The dissolution of Sr and Al ions from fine S3A cement was enhanced. However, the relative flowability decreases with fine grinding. Further studies on flowability, handling property are required. Additionally, the biological effects of endodontic cement should be studied both in vitro and in vivo.

Flowability and Strength Characteristics of Binary Cementitious Systems Containing Silica Fume, Fly Ash, Metakaolin, and Glass Cullet Powder.

The present study examines the effects of supplementary cementitious materials (SCMs) on the flowability and strength development of binary mixes. This study was primarily motivated by the need to bridge the knowledge gap regarding paste and mortar mixes containing binary cement from a variety of performance perspectives. This study examined the flowability and strength development of binary mixes in their pastes and mortars when they contain various doses of silica fume (SF), fly ash (FA), metakaolin (MK), and glass cullet powder (GP) compared with the control mix. While the presence of SF and MK reduced workability because of the nature of their particles, the addition of FA and GP improved it to a certain extent because of the spherical and glassy nature of their particles, respectively. In addition, GP was used to compare its performance against SF, MK, and FA as an alternative cementitious material. In this study, the GP performed comparably to the other SCMs investigated and was found to be satisfactory. An investigation of the rheological properties, heat of hydration, thermal analysis, and pore systems of these mixes was conducted. Compared to the control mix, the presence of 5% GP improved the rheological properties and reduced the heat of hydration by 10%. The reduced workability in SF and MK mixes resulted in a lower content of pore water, while GP and FA incorporation enhanced it, owing to improved workability. The pore area is related to the pore water, which is directly related to improved workability. According to the following order, SF > MK > GP > FA, the strength was highest for mixes containing SF and MK, whereas, with GP and FA, there was a gradual reduction in the strength proportional to replacement level and improved workability. SF, GP, and FA can be identified as performance enhancers when formulating ternary and quaternary cementitious systems for low-carbon cement.

Performance of the Cement Grouting Material and Optimization of the Mix Proportion for the Free Section of the Prestressed Anchor Bar.

Increasing the water-cement ratio and water-reducer dosage of cement slurry enhances its fluidity. However, a high water-cement ratio diminishes the beneficial effects of water reducers on fluidity. The stone content of the slurry decreases as the water-reducer dosage increases. Additionally, the water-cement ratio significantly affects stone content. However, when the water-cement ratio exceeds a threshold value, stone content decreases. Furthermore, the threshold value of the water-cement ratio decreases with increasing water-reducer dosage. Without the addition of the water reducer, as the water-cement ratio increases the overall integrity of the grout stone decreases. The addition of the water reducer alters the surface pore distribution, wherein "uniform small pores" change to "localized large pores." Based on the multi-objective optimization of Matlab, the recommended optimal mix composition for a slow-setting cement slurry is a water-cement ratio of 0.25 and water-reducer dosage of 1.5%. With the use of this optimized mix composition, the stone content and compressive strength increase by 7.8% and 145.6%, respectively, compared to those obtained using the recommended mix ratio in the specifications. Additionally, all relevant performance parameters meet the requirements specified by previous standards.

Investigation of the Effects of Polyurethane-Modified Polycarboxylate at Ambient Temperature on the Characteristics of Cement with Supplementary Cementitious Materials.

Via radical polymerization, three polyurethane-modified polycarboxylate molecules of various comb topologies were synthesized. This study investigated the effects of varying types and concentrations of supplementary cementitious materials (SCMs) on the surface tension, flowability, and zeta potential of cement. An elevation in the molar ratio between isoamyl alcohol polyoxyethylene (TPEG) and acrylic acid (AA) from 1:1 to 5:1 reduced the surface tension of the polycarboxylate molecule from 47.70 mN/m to 35.53 mN/m and increased flowability from 280 mm to 310 mm, as the results indicated. An increase in the SCM and polycarboxylate dosage proportionally decreased liquid-phase surface tension and increased flowability. A decrease in the water-to-cement (w/c) ratio from 0.5 to 0.3 corresponded to an observed increase in the zeta potential of cement pastes. However, a rise in the quantity of polycarboxylate and SCMs corresponded to a decrease in the zeta potential at a w/c ratio of 0.3.

Study on application and environmental effect of phosphogypsum-fly ash-red mud composite cemented paste backfill.

Phosphogypsum (PG) cementitious paste backfill (CPB) was prepared by using PG and fly ash (FA) as the main raw materials, red mud (RM) as the alkaline activator, Portland cement (OPC) as the binder, and silica fume (SF) as the additive, and its properties were investigated to achieve the objective of "treating harm with waste." The results showed that the addition of OPC facilitated the flowability of the slurry, while the addition of RM and SF had the opposite effect. The slurry presented ideal flowability when the water/binder ratio was 0.2 and the superplasticizer (SP) content was 0.7%. The mechanical properties and water resistance were improved significantly with increasing OPC, RM, and SF doping. The strength of the CPB material exceeded 22 MPa after curing at room temperature for 28 days, which met the mine filling requirements. Changes in the ion concentrations of the solution were first monitored during immersion. The dissolution rules of Ca2+ and SO42- at different immersion ages confirmed that RM promoted the continuous hydration of CPB, which was the key to improve water resistance. Microstructural analysis showed that the main hydration products were AFt and C-S-H, which played an important role in the strength development of the material. The leaching results demonstrated that the metal ion content satisfied the requirements of the III categories of Chinese environmental standards (GB/T 14848-2017), indicating that the technology is a reliable and environmentally friendly technology for PG, FA, and RM recovery that can simultaneously support safe mining.

Properties of Self-Compacting Concrete Produced with Optimized Volumes of Calcined Clay and Rice Husk Ash-Emphasis on Rheology, Flowability Retention and Durability.

The durability of concrete requires a dense microstructure which can be achieved by using self-compacting concrete (SCC). Both calcined clay (CC) and rice husk ash (RHA) are promising supplementary cementitious materials (SCMs) that can partially replace cement, but their use in SCC is critical due to their higher water demand (WD) and specific surface area (SSA) compared to cement. The effect of partial substitution of cement at 20 vol-% with binary and ternary blends of CC and RHA on flowability retention and durability of SCC was investigated. The empirical method of SCC design was adopted considering the physical properties of both CC and RHA. The deformability of the SCC was evaluated using the slump flow and J-ring tests. The T500 time and the V-funnel test were used to assess the viscosity of the SCC. The flowability retention was monitored by the plunger method, and flow resistance was determined based on the rheological measurements of SCC. The evolution of the hydrate phases of the binder in SCC was determined by thermogravimetric analysis, while the durability was evaluated by a rapid chloride migration test. Cement partial replacement with 20 vol-% CC has no significant effect on fresh SCC, flowability retention, compressive strength and durability properties. On the other hand, 20 vol-% RHA requires a higher dosage of SP to achieve self-compactability and increase the viscosity of SCC. Its flowability retention is only up to 30 min after mixing and exhibited higher flow resistance. It consumes more calcium hydroxide (CH) and improves the compressive strength and chloride resistance of SCC. The ternary blending with CC and RHA yielded better fresh SCC properties compared to the binary blend with RHA, while an improved chloride penetration resistance could be achieved compared to the binary CC blend.

Selection of Silica Type and Amount for Flowability Enhancements via Dry Coating: Contact Mechanics Based Predictive Approach.

PURPOSE: To investigate the effect of dry coating the amount and type of silica on powder flowability enhancement using a comprehensive set of 19 pharmaceutical powders having different sizes, surface roughness, morphology, and aspect ratios, as well as assess flow predictability via Bond number estimated using a mechanistic multi-asperity particle contact model. METHOD: Particle size, shape, density, surface energy and area, SEM-based morphology, and FFC were assessed for all powders. Hydrophobic (R972P) or hydrophilic (A200) nano-silica were dry coated for each powder at 25%, 50%, and 100% surface area coverage (SAC). Flow predictability was assessed via particle size and Bond number. RESULTS: Nearly maximal flow enhancement, one or more flow category, was observed for all powders at 50% SAC of either type of silica, equivalent to 1 wt% or less for both the hydrophobic R972P or hydrophilic A200, while R972P generally performed slightly better. Silica amount as SAC better helped understand the relative performance. The power-law relation between FFC and Bond number was observed. CONCLUSION: Significant flow enhancements were achieved at 50% SAC, validating previous models. Most uncoated very cohesive powders improved by two flow categories, attaining easy flow. Flowability could not be predicted for both the uncoated and dry coated powders via particle size alone. Prediction was significantly better using Bond number computed via the mechanistic multi-asperity particle contact model accounting for the particle size, surface energy, roughness, and the amount and type of silica. The widely accepted 200 nm surface roughness was not valid for most pharmaceutical powders.