Paste Mixes Research Articles

Variation of Packing Densities and Liquid Film Thicknesses in Alkali Solution and Water in Natural Pozzolan Calcium Hydroxide Pastes and Mortars

The characteristic properties of concrete depend on the quality of mortar. In order to improve the properties of hardened concrete, the mortar needs to have good performance. The property of mortar is affected by wet packing density, liquid film thickness, type and quality of binder, gradation of fine aggregates, and binder-to-fine-aggregate ratio. The commonly used alkali solutions to produce polymer mortar and concrete are cursed by carbon dioxide emissions. This study used alkali solution and water to investigate the variation of packing densities and film thicknesses on paste and mortar mixes. of natural pozzolan and calcium hydroxide at a ratio of 75P25CH and standard sand. The standard proctor compaction tools and procedures were adopted to attain the maximum values of packing density of 0.937 for mortar mixed with alkali solution, 0.919 for mortar mixed with water, 0.906 for paste mixed with alkali solution, and 0.829 for paste mixed with water. For the case of film thicknesses, the optimum values obtained were 0.548 μm for mortar mixed with alkali solution, 0.248 μm for mortar mixed with water, 0.398 μm for paste mixed with alkali solution, and 0.09 μm mixed with water. The results indicate that alkali solution produced higher packing density and liquid film thickness than water for both paste and mortar, and the packing density and liquid film thickness increase with the increase of the number of compacting blows with 9 blows to 36 blows. The study recommends the establishment of standard compaction effort and procedure.

Effect of Olive Waste Ash as a Partial Replacement of Cement on the Volume Stability of Cement Paste

Over the last decades, concrete has been excessively prone to cracks resulting from shrinkage. These dimensional changes can be affected by the incorporation of supplementary cementitious materials. This work used olive waste ash (OWA), which could substantially tackle this problem and achieve sustainability goals. For this issue, five cement paste mixes were prepared by replacing cement with OWA at different percentages varying from 0 to 20% by weight with a constant increment of 5%. The water-to-cement ratio was 0.45 for all mixes. Compressive strength and flexural strength were investigated at 7, 28, and 90 days. In addition, three shrinkage tests (drying, autogenous, and chemical) and expansion tests were also conducted for each mix and measured during 90 days of curing. The experimental findings indicated that there was a loss in compressive and flexural strength in the existence of OWA. Among all mixes containing OWA, the samples incorporating 10% OWA exhibited maximum strength values. Furthermore, the chemical and autogenous shrinkage decreased with the incorporation of OWA. However, the drying shrinkage decreased at lower levels of substitutions and increased at higher replacement levels. In addition, there was a growth in expansion rates for up to 10% of OWA content, followed by a decrease at higher levels (beyond 10%). Additionally, correlations between these volumetric stability tests were performed. It was shown that a positive linear correlation existed between chemical shrinkage and autogenous and drying shrinkage; however, there was a negative relationship between chemical shrinkage and expansion.

Effect of sodium gluconate addition on setting, hardening, and microstructure behaviour of hybrid alkaline mortar

In this investigation, the influence of adding 2 %, 4 %, 7 %, and 10 % sodium gluconate (SG) on the setting time of hybrid alkaline paste, and hardened and microstructure properties of hybrid alkaline mortar mixes were examined, and the results were compared with a control mix that made without addition of sodium gluconate. The hybrid alkaline paste and mortar mixes were prepared using a fixed proportion of OPC/fly ash (25 %/75 %), NaOH solution molarity of 9 M, and sodium silicate to hydroxide ratio of 1.5. The results of this investigation found that the quick setting and abrupt loss of flowability of the control mix were improved by adding sodium gluconate, however, more promising results were observed at 7 % and 10 % sodium gluconate. The delay in polymerization due to lower availability of calcium ions, and adsorption of carboxyl and hydroxyl groups associated with sodium gluconate on the unreacted particles of binding materials and earlier formed products assisted in prolonging the time required for hardening. Further, the compressive strength declined at a higher dosage of sodium gluconate, however, the mortar mixes made with 2 % and 4 % sodium gluconate exhibited higher compressive strength than the control mix. The peak intensity of albite, nepheline, and C–S–H gel decreased at higher dosages of sodium gluconate, which was supported by a weaker microstructure characterized by more pores, micro-cracks, and partially reacted fly ash particles. Furthermore, the lower bridging oxygen content and greater Si–O–Na/ Si–O–T ratio at higher dosage of sodium gluconate confirms the delayed polymerization process.

Effect of in situ CO2 mixing of cement paste on the leachability of hexavalent chromium (Cr(VI))

In situ CO2 mixing technology is a potential technology for permanently sequestering CO2 during concrete manufacturing processes. Although it has been approved as a promising carbon capture and utilisation (CCU) method, its effect on the leachability of heavy metals from cementitious compounds has not yet been studied. This study focuses on the effect of in situ CO2 mixing of cement paste on the leaching of hexavalent chromium (Cr(VI)). The tank leaching test of the CO2 mixing cement specimen resulted in a Cr(VI) cumulative leaching of 0.614 mg/m2 in 28 d, which is ten times lower than that of the control mixing specimens. The results in thermogravimetric analysis indicated that a relatively significant amount of CrO42− is immobilised as CaCrO4 during the CO2-mixing, and a higher Cr–O extension is observed in the Fourier transform infrared spectra. Furthermore, a portion of the monocarboaluminate is inferred from microstructural analyses to incorporate CrO42− ions. These results demonstrate that in situ CO2 mixing is beneficial not only in reducing CO2 emissions, but also in controlling the leaching of toxic substances.

Optimizing binders with maximum using of industrial waste to develop low carbon ultra-high performance concrete

Optimizing binders by using industrial waste and then adjusting microstructure has potential to develop low production cost and low carbon emission ultra-high performance concrete (UHPC) to meet different practical engineering requirements. This study first investigates the influence of silica fume, cenosphere and fly ash on paste mixing time, flowability, flexural and compressive strength of UHPC by using three-factor and four-level orthogonal test. Moreover, the effect of fly ash and slag content were further discussed, and the modification mechanisms of binders were revealed by analyzing pore structure, interface and characteristics of hydration products. The results show that silica fume and cenosphere are the most sensitive factors affecting paste mixing time and flowability of UHPC, respectively. The sensitivity of binders on compressive and flexural strength of UHPC can be ranked according to silica fume > fly ash > cenosphere and cenosphere > fly ash > silica fume, respectively. The binders’ composition for low-carbon UHPC with compressive strength grade of 120 MPa is that cement: cenosphere: silica fume: fly ash equals to 1:0.33:0.33:0.56, and the total amount of fly ash reaches 40%. Meanwhile, the 28d compressive/flexural strength decreases and the flowability increases with the increase of fly ash content, resulting from pore volume with size of 5–50 nm and Ca/Si ratio on the interface between steel fiber and matrix increase. The flowability of UHPC with slag is reduced and the cumulative pore volume with size of 50 nm–5 um pores is increased due to the influence of slag morphology, but the porosity and interfacial Ca/Si ratio is reduced because of the high pozzolanic activity of slag, leading to similar compressive and flexural strength with that of UHPC with fly ash.

Creep and fracture of UHSC — A microindentation study

Creep and fracture behaviour of normal strength concrete was investigated by various researchers whereas, research on creep and fracture of Ultra-High-Strength Concrete (UHSC), i.e., concrete with 28-day compressive strength greater than 100MPa is scanty. Also, a detailed investigation of the creep–fracture interaction of UHSC has not been conducted.This study aims at examining creep and fracture of UHSC cement paste mixes (w/b = 0.20) with varying levels of silica fume (SF) replacement (0%, 20%, and 40%) at different ages (3d, 7d, 28d, 90d) using microindentation technique. Two different holding durations, namely 5 s and 180 s, were considered in the indentation test. The findings revealed a noteworthy variation in estimated fracture toughness (Kc) between the two dwelling periods. Longer sustained loading times (180s) indicated a decrease in fracture toughness for all ages considered, suggesting progressive internal cracking during creep phase. Attempt has been made to investigate the interaction effect.

New insights into early-stage time-dependent dielectric characteristics coupled with frequency dependency and hydration-driven reaction of hydraulic cement pastes: Experiments and statistical modelling

In the field of cement and concrete materials engineering, a comprehensive understanding of dielectric properties is crucial for optimising hydraulic cement paste mix designs. This study examines the relationships among the dielectric constant (ε’), loss tangent (tan δ), frequency, hydration time, water content and admixture dosage in different compositions of hydraulic cement paste. A consistent pattern can be observed across the frequency spectrum, where dielectric constants decrease as frequency increases. This aligns with the expected behaviour of cementitious materials. The most notable finding is the inversely proportional relationship between the loss tangent and frequency. As the frequency increases, the loss tangent consistently decreases, indicating improved energy retention and reduced dissipation. This characteristic is of significant value for various applications, including sustainable infrastructure and smart materials. Furthermore, the interactions among hydration time, water content and admixture dosage present an opportunity for dynamic optimisation within the cement paste matrix. These factors collectively impact dielectric properties, providing insights into the potential for tailored material performance and durability, especially in applications where dielectric properties are critical, such as sensing applications and structural health monitoring of concrete structures. This study emphasises the importance of customising cementitious compositions for specific applications in cement and concrete materials engineering. It achieves this through a detailed comparative analysis of different compositions, each representing varying water content and admixture dosage levels. This approach has the potential to significantly transform the field by enabling engineers to create hydraulic cement pastes with customised dielectric properties that meet the specific requirements of construction, infrastructure and other related applications.

Optimizing mix proportions of blended cement composites through rheological and strength relations: A numerical modelling approach with curve fitting

The research presented is part of a larger project focusing on finding the optimum mix design for cement pastes using ternary blended binder containing cement, Calcium metasilicate (CMS), and colloidal nano-SiO2. Water absorption and sorptivity tests were also conducted to ascertain the porosity of the paste mixes. Compressive and flexural strength were used for the mechanical properties of different mixes, and rheology was conducted to find the flow characteristics of paste mixes. The numerical modeling employed involves regression analysis and curve fitting to find the significant factors affecting the properties of cement composites. The experimental data were subjected to analysis of variance (ANOVA) to determine the essential factors and their interactions. The results for strength parameters for high-volume replacement suggests that the optimum replacement levels for nano-SiO2 were 3% in both w/b ratios. The rheological parameter states that microfibres of CMS and nano-SiO2, increased the viscosity and decreasing the yield stress. The FESEM micrographs show the sequestration of CO2 and calcite formation due to high-volume CMS.

Data-driven budget allocation of retail media by ad product, funnel metric, and brand size

Sellers on online marketplaces such as Amazon.com use a variety of retail and retail media advertising services to improve their brand performance, including awareness, consideration, and revenue. But how can they measure their progress and drive these metrics? For 122,000 brands, we measure Amazon shoppers’ brand awareness, consideration, and purchases and test how they change with ad and retail actions. Furthermore, we compare these brands’ past media mix with the recommended allocation based on the model’s coefficients. We find that new product launches and upper-funnel retail media advertising are particularly effective for small brands. Medium-sized and large brands benefit most from lower-funnel advertising. For the funnel stages, all three metrics benefit from the number of new reviews, % discount, negative keywords, and geo-reach campaigns. These results are robust across different product categories, but we find notable differences in how upper- and middle-funnel ad products succeed in driving sales.

Investigating volume stability Performance of paste with Phragmites Australis (PA) Fibers

Environmental sustainability is a critical concern in the construction industry due to its substantial energy consumption and carbon dioxide emissions. This study addresses the sustainability of building materials by exploring the volume stability of cementitious system by adding natural fibers, specifically those derived from the Phragmites Australis (PA) plant. Natural fibers exhibit high strength and stiffness, making them suitable for structural applications. In this experimental study, four paste mixes were prepared, incorporating varying percentages (0%, 0.5%, 1%, and 2%) of PA fibers. Testing included drying shrinkage, autogenous shrinkage, and expansion. Results showed a notable reduction in paste shrinkage, with percentages of 12.7%, 19%, and 29% observed at 7 days with the addition of 0.5%, 1%, and 2% PA fibers, respectively, at an elevated temperature of 45°C. These findings suggest the potential for PA fibers to mitigate shrinkage in building materials, thus contributing to the overall environmental sustainability of construction practices.

Data Mining Approach Using Cluster Analysis and Decision Trees for Optimizing Electrode Paste Quality in Lithium-Ion Battery Production

Lithium-ion batteries are crucial for the energy transition, especially for emission reduction in the automotive sector and energy storage solutions. Therefore, an efficient, sustainable, and economic battery cell production is needed. To ensure optimal cell quality and enable quality control, the highly complex inter-dependencies in the battery cell production must be understood and the potential for improvement must be discovered. In the context of complex processes and data structures, data mining techniques have been established in the industry. Here, a data mining approach consisting of a Cluster Analysis and Decision Trees is applied to a data set obtained by measuring process and quality data during the electrode paste mixing process. The aim is to analyse the influence of manufacturing parameters on selected quality characteristics (i.e. viscosity and particle size distribution of the electrode paste).The Cluster Analysis is used to create classes of similar quality characteristics. Decision trees map the dependencies between the formed clusters and process parameters. The results show that the density-based clustering algorithms achieve the best clustering outcomes for product quality. Based on the feature importance of different Decision Trees, the most important process parameters that affect the quality classes are determined. This approach is transferable to other process steps and offers the capability to analyse a series of process steps and the final product quality.

Class-C fly ash from coal as a partial substitute in cement-based paste and mortar design mix – A case in the Philippines

An indirect way to minimize greenhouse emissions from the cement industry is partially substituting cement with coal fly ash (CFA). Despite CFA being widely studied, the quality, performance, and water requirements, when used in formulating paste and mortar, vary depending on the source. This study assessed CFA from a power plant in the Philippines as a partial substitute for cement. Paste and mortar mixture were designed to have varying CFA-to-binder ratios (CBR) and water-to-binder ratios (WBR). The effect of CBR and WBR on the consistency and workability of fresh paste and mortars were modeled, adopting multivariate non-linear regression to objectively assess the individual and interactive effects. Properties (compressive strength, density, and voids) of hardened mortar formulated with different CBRs but having normal consistency/workability were determined and assessed. Models generated could be used to estimate the WBR required for formulations to achieve normal consistency/workability. The water requirement for mortar formulation to have normal workability may be predicted based on the WBR for paste formulated to have normal consistency. Increased cement replacement with CFA improved the compressive strength, with replacement up to 20 wt% resulting in better performance than pure cement.

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.

Development of high-volume steel slag as cementitious material by ethylenediamine tetraacetic acid induced accelerated carbonation

Steel slag, a by-product of primary steel production, is produced in large quantities and is primarily used as landfill or aggregate. Due to its high reactivity with CO2, steel slag can form calcium carbonate at room temperature and pressure, making it an ideal material for CO2 capture in the development of sustainable construction materials. Due to the transport properties of CO2 and carbonation kinetics, carbonation of steel slag is frequently carried out using pure gas under high pressure. In this study, ethylenediamine tetraacetic acid (EDTA)-induced accelerated carbonation was used to produce cement paste mixes consisting of up to 100% steel slag powder. Combination of cement and EDTA with steel slag proved to be effective in accelerating the carbonation reaction. EDTA increased the leaching of Ca from the steel slag, thereby enhancing the carbonation reaction, which was more obvious in longer durations (up to 28 days). The optimum cement paste mix (80% steel slag and 20% cement, with 0.1 mol/L EDTA solution) achieved maximum compressive strength of 14 MPa and CO2 uptake of 8.7% after 28 days of accelerated carbonation. Results demonstrated that the use of high-volume steel slag as a cementitious material has great potential in non-structural building applications.

Numerical Simulation of Torque Variation During Paste Mixing and Kneading

In the production process of aluminum electrolytic carbon anode, the kneading process is to fully mix asphalt and powder to obtain the best paste, because the kneading process is completed in a high-temperature kneading machine, there is no suitable automatic real-time judgment method for the uniformity of paste. Real-time online monitoring based on the viscoelastic change of paste during kneading is a potential method to judge the uniformity of paste. In this paper, the Discrete Element Method numerical simulation is used to study the variation law of stirring torque in the mixing and kneading wet mixing process, mainly examining the effect of viscosity on stirring torque. The results showed that the mixing and kneading torque varied periodically and the total torque of the stirrer was positively correlated with the viscosity.

The potential for palaeoseismic and palaeoclimatic reconstructions from Lake Tennyson, North Canterbury, New Zealand

ABSTRACT Lake Tennyson’s basin and sedimentary record were assessed for multiple branches of paleoenvironmental research. A geophysical investigation of the lake depositional setting was supported by physical and chemical analysis of multiple sediment cores. The basin reaches 60 m depth and several subaerial landforms identified were likely deposited from seismic activity. Deformed sediments and turbidites in gravity cores are attributed to one or more large (pre)historic earthquakes, and episodic grain size changes in sediment cores are related to either seismic and/or climatic/meteorological processes. A hummocky slump deposit located on the western lake bed margin is linked to widespread sediment deformation that was likely caused by movement of the Awatere Fault. Radiocarbon dating constrains the most recent major deformation event between the late thirteenth century CE and mid-twentieth Century. Folded turbidites in the stratigraphy suggest multiple sedimentary deformation episodes occurred during the last millennium. Micro-XRF elemental signatures suggest proxies of past water column mixing (windiness proxy) can be reconstructed via identification of changing redox conditions. Records from Lake Tennyson show potential for several palaeoenvironmental research applications, and combining them with basin morphostratigraphy and land-based palaeoclimate and palaeoseismic evidence can enhance understanding of environmental change in the northern South Island.

Hybrid effect of GNPs, GOs, and CNTs on the flexural and compressive strengths of cement paste

This paper presents the individual and synergic effects of Graphene Nanoplatelets (GNPs), Graphene Oxides (GOs) and Carbon Nanotubes (CNTs) on the flexural and compressive strengths of cement paste. Mixes containing several nanoparticle types and weight fractions were prepared with Polycarboxylate ether (PCE) surfactant and tested after 90 days of curing. After that, the microstructure of the failed samples was studied using a Scanning Electron Microscope (SEM). Response Surface Methodologies (RSM) techniques were then employed to determine the strength functions' response to the nanofilaments' types and weight fractions. Finally, a cost analysis was done to evaluate the mixes' performance in-terms of strength and cost. Test results showed that the flexural strength of cement paste could be enhanced by 57.33% when using 0.04 wt % GOs. The results also showed that mixes containing 0.08 wt % GOs and 0.12 wt % CNTs improved the flexural strength by 47.03 and 44.38%, respectively when compared with the control cement paste mix. In-terms of compressive strength, mixes containing 0.04 wt % GNPs attained the highest compressive strength improvement of 15.7% when compared with the control mix. In hybrid mixes containing more than one nanoparticle type, the best synergistic action was generated between 50% CNTs and 50% GOs at a total dosage of 0.04% wt, where the compressive strength increased by 20.2%. The microstructural analysis showed good dispersion qualities and nanoparticles embedment within cement hydration products. On the other hand, RSM analysis showed that the maximum compressive and flexural strength functions' responses are obtained at the lowest nanofilaments’ weight fraction of 0.04 wt %. The desirability analysis confirmed that the compressive and flexural strengths of cement paste could be improved by 7 and 53%, respectively, using the predicted formulas. Finally, the cost analysis showed that GO-modified cement pastes are considerably more expensive than other mixes, yielding the lowest economic index.

β-CaSiO3 and colloidal n-SiO2 based blended cement composites- their properties, regression analysis and micro-characterization studies

This paper examines the effect on mechanical properties such as compressive strength, flexural strength, and dynamic modulus of elasticity (DYE) of different proportions of wollastonite (β-CaSiO3) and colloidal nano-silica (n-SiO2) partially replacing cement. Durability indicators (water absorption, sorptivity and sulphate treatment test) were also examined to ascertain the quality of hardened paste mixes with respect to the control mix. The regression models were found for mechanical properties using different parameters from the results obtained, and statistical relations were established and validated. Regression analysis shows the significance of every parameter considered and model for the prediction of mechanical strengths. Finally, the results were substantiated by the microstructural characterization by FESEM. β-CaSiO3 and colloidal n-SiO2 replaced cement by 15%, and 1.5%-6% with an offset of 1.5%, respectively at low (0.25), medium (0.40) and high (0.55) water/binder (w/b) ratio. FESEM micrographs showed dense Calcium-silicate-hydrate (CSH) gel and stratlingite (CASH) was formed by blended cement paste mixes containing β-CaSiO3 and n-SiO2. n-SiO2 at 3% and CaSiO3 at 15% replacements of cement (NS3 mix) was the optimum replacement level for the cement paste mix. Analysed regression model suggests that the models and parameters were found significant and can also be used for prediction (based on R2 values and p-value).

ポリマーセメントペーストを用いたシート防水密着構法に関する研究（その１）：ポリマーセメントペーストの調合が接着性および水密性に及ぼす影響

In this paper, two experiments were conducted to clarify the influence of polymer cement paste mix proportion on in-plane permeability resistance, adhesiveness and watertightness. The followings are concluded from the test results. If the quality of the underlying concrete is poor, fracture at the interface between substrate and hardened paste is likely to occur. If the paste is a softer mix proportion, adhesive failure and moisture migration are more likely to occur due to the formation of a fragile layer, presumably caused by bleeding. These problems can be improved by mixing a standard amount of polymer in this waterproofing system.

Fabrication of Flexible All-Solid-State Asymmetric Supercapacitor Device via Full Recycling of Heated Tobacco Waste Assisted by PLA Gelation Template Method.

In this study, a flexible all-solid-state asymmetric supercapacitor (FASC) device has been successfully fabricated via full recycling of heated tobacco waste (HTW). Tobacco leaves and cellulose acetate tubes have been successfully carbonized (HTW-C) and mixed with metal oxides (MnO2 and Fe3O4) to obtain highly active materials for supercapacitors. Moreover, poly(lactic acid) (PLA) filters have been successfully dissolved in an organic solvent and mixed with the as-prepared active materials using a simple paste mixing method. In addition, flexible MnO2- and Fe3O4-mixed HTW-C/PLA electrodes (C-MnO2/PLA and C-Fe3O4/PLA) have been successfully fabricated using the drop-casting method. The as-synthesized flexible C-MnO2/PLA and C-Fe3O4/PLA electrodes have exhibited excellent electrical conductivity of 378 and 660 μS cm-1, and high specific capacitance of 34.8 and 47.9 mF cm-2 at 1 mA cm-2, respectively. A practical FASC device (C-MnO2/PLA//C-Fe3O4/PLA) has been assembled by employing the C-MnO2/PLA as the positive electrode and C-Fe3O4/PLA as the negative electrode. The as-prepared FASC device showed a remarkable capacitance of 5.80 mF cm-2 at 1 mA cm-2. Additionally, the FASC device manifests stable electrochemical performance under harsh bending conditions, verifying the superb flexibility and sustainability of the device. To the best of our knowledge, this is the first study to report complete recycling of heated tobacco waste to prepare the practical FASC devices. With excellent electrochemical performance, the experiments described in this study successfully demonstrate the possibility of recycling new types of biomass in the future.