Blended Pastes Research Articles

Physical-chemical performance of coal gasification slag with calcination activation utilized as supplementary cementitious material

The utilization of coal gasification slag to prepare supplementary cementitious materials has garnered considerable interest due to environmental friendliness. In this study, a calcination activation was carried out to enhance the pozzolanic activity of coal gasification slag, and serial sintering temperatures were conducted to activate coal gasification slag in this study. The coal gasification slags were characterized by particle size analyzer, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Furthermore, the pozzolanic activity of coal gasification slag was identified through dilution test and application in blended paste. Results showed that the calcination pretreatment effectively affected the particle size distribution and mineral composition. The setting time and hydration rate were prolonged by incorporating coal gasification slag. It was crucial that the coal gasification slag calcined under 400℃ performed the highest reactivity and its blend presented a 4.75% higher compressive strength than neat cement at 28 d curing. AFt and AFm were mainly generated by pozzolanic reaction, and a denser microstructure that porosity decreased by 26.76% was gained. The achievement of this study proved the feasibility of this treated coal gasification slag in building materials.

Wood ash-based binders for lightweight building materials: Evaluating the influence of hydraulic lime and cement on the setting and mechanical properties of wood ash pastes

The shift from fossil fuels to bioenergy has led to increased wood ash output. Since a large proportion of this waste ends up in landfills, recycling wood ash in construction materials is one of sustainable approaches of managing this by-product. However, the amount of biomass ashes currently recycled in building materials is still limited. This study therefore explored the feasibility of valorising four different types of wood ashes in large quantities in the production of lightweight building materials. Thirty pastes with different levels (80, 90, 95 and 100 wt%) of wood ash and (0, 5, 10 and 20 wt%) of natural hydraulic lime (NHL) or ordinary Portland cement (PC) were developed. Partial replacement of wood ash (WA) by NHL or PC accelerated the setting and improved the mechanical properties of blended pastes. The initial and final setting times decreased with increasing NHL or PC content in the mixes. The strength of the pastes increased with increasing NHL or PC levels and curing time. However, wood bottom ash (WBA) mixes were controversial because their mechanical properties gradually weakened over time. For WA-NHL blends, the 28-day flexural and compressive strength ranged from 0.02 to 1.12 MPa and from 0.05 to 2.59 MPa, respectively. On the other hand, for WA-PC pastes, the flexural and compressive strengths at 28 days varied from 0.07 to 2.72 MPa and from 0.13 to 5.49 MPa, simultaneously. These results prove that wood ash can be used effectively as a main component of binding matrices for lightweight building materials.

Assessment of blended cement containing waste basalt powder: physicomechanical and electrochemical impedance spectroscopy investigations

Basalt powder (BP) is the residue of a plant that crushes basalt stones. This work deals with the effect of waste BP on the properties of cement mortars and the physical properties of hardened mortars. Modified concrete was prepared by partial replacement of BP in amount of 5, 10, 20% by weight of cement. Physico-mechanical properties and corrosion resistance were investigated. Electrochemical impedance spectroscopy (EIS) was used to examine the corrosion behavior of cement pastes with a partial addition of basalt powder in aggressive solutions of 5% NaCl and 5% MgCl2 for up to 270 days. Infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were also performed to investigate the hydration process and microstructure formation of the basalt blended paste. Results indicate that the addition of basalt powder as a partial replacement of cement influences the microstructure of the interfacial transition zone (ITZ), which is denser and stronger than in cement paste without basalt powder. The filler effect of the basalt powder improves the compressive strength of cement paste. Also, comparing BP0 and BP20 in 5% NaCl after 270 days, the partial substitution of cement with BP resulted in a higher compressive strength of 671 and 895 kg/cm2, respectively. The EIS results also showed the highest values of Rp 953 ohms cm2 after 270 days. This high corrosion resistance might indicate the binding by high Al2O3 that reduced the free aggressive chloride ions in the solution.

Waste glass powder as a high temperature stabilizer in blended oil well cement pastes: Hydration, microstructure and mechanical properties

Recycling waste glass for diversified utilization has received increasing attention in recent years. This work aimed to reuse waste glass powder (GP) as a high temperature stabilizer to replace silica flour (SF) in blended G class oil well cement (GOWC) pastes. Blended pastes containing 40 % and 66.7 % GP were prepared and compared to pure GOWC paste and blended paste containing 40 % SF commonly used in the oil industry. Under simulated field conditions in a steam injection well, these pastes were cured at 50 °C for seven days, followed by three rounds of thermal cycling curing at high temperature and high pressure (HTHP, 300 °C/13 MPa) conditions. The effects of GP on the hydration kinetics, hydration products, microstructure, and mechanical properties of hardened pastes were evaluated. The results demonstrated that the addition of GP or SF reduced the compressive strength of the pastes at 50 °C due to dilution effect. Compared with SF, GP exhibited higher pozzolanic activity, prolonged the induction period, and promoted the formation of more C-(N)-S-H gels with lower Ca/Si ratios, which led to an increase in the gel pores content of the matrix and partially compensated for the loss of compressive strength due to the dilution effect. Additionally, due to the pozzolanic reaction of GP, the content of CH in the matrix decreased and its crystal size became smaller. After three rounds of thermal cycling curing, the incorporation of GP significantly increased the compressive strength of the hardened pastes. The compressive strengths of the hardened pastes with 40 % and 66.7 % GP were 20.33 MPa and 22.25 MPa, respectively, which were 7.62 % and 17.79 % higher than those of the hardened paste containing 40 % SF. In addition, the compressive strengths of hardened pastes containing 40 % and 66.7 % GP after three rounds of thermal cycling curing decreased by 22.49 % and 5.52 %, respectively, compared to the pastes at the low-temperature stage, while that of the pure GOWC pastes decreased by 83.8 %. Characterization analyses indicated that GP could further reduce the Ca/Si ratio of the system, modulate the crystallization of the gels at high temperatures, and generate foshagite or xonotlite phases with high polymerization structure and thermal stability, instead of reinhardbraunsite. These products effectively refined pore structure and enhanced microstructure densification. Furthermore, the precipitation of Na+ ions during hydration did not affect the microstructure of the matrix. This study offers some guidelines for recycling waste glass, conserving raw materials, and producing sustainable blended cement pastes.

Development of sustainable conductive cementitious composite using graphite-coated spent catalyst waste

This study presents an innovative approach to developing sustainable conductive composites by coating graphite onto the surface of spent catalyst waste through nano-surface engineering techniques. The process ensures uniform adsorption of graphite onto the surface of the spent catalyst waste particles, followed by oven treatment and milling. This results in better integrity and effective bonding, leading to the production of graphite-coated spent catalyst waste (G-SCW). Scanning electron microscopy indicates the successful coating of spent catalyst waste with graphite. The research investigates the effect of G-SCW on the cementitious properties of paste and mortar. Incorporating G-SCW results in acceptable workability and setting time, while the compressive strength increases at early and later stages, with up to 20 % G-SCW content. The addition of G-SCW in the mortar significantly reduces the electrical resistivity, resulting in a 63 % reduction in resistivity compared to the reference mix, thereby enhancing the conductivity. Hydration studies confirm the presence of pozzolanic reaction in blended paste, as evidenced by a decrease in calcium hydroxide content. The sustainability assessment indicates a substantial reduction in embodied carbon and possibly producing mortar with lower cement content. These findings suggest great potential for developing sustainable conductive mortar with G-SCW, enabling smart building construction, and supporting sensor networks for structural health monitoring.

Effect of Bambara Groundnut Flour (Vigna subterranea) Inclusion on the Functional, Pasting, Physical and Proximate Properties of Composite Cassava-bambara Flour

This study evaluated the effect of Bambara groundnut flour inclusion on the functional, pasting, physical properties and proximate compositions of composite flour (CF) from cassava and Bambara groundnut. Cassava variety (IITA-TMS-IBA011368) and Bambara groundnut were processed into flour and blended together based on D-Optimal mixture design with an outcome of eight experimental samples using Design Expert Software (Version 12.0). The flour blends were analyzed for functional, pasting, physical properties (color), baking strength and proximate composition. Data obtained were analyzed using analysis of variance and means were separated using Ducan’s Multiple Range Test. Range of results for bulk density, water absorption capacity, swelling index, solubility index and oil absorption capacity of the composite flour are 0.64-0.80g/mL, 0.38-1.37%, 0.77-0.91%, 6.00-8.65, 1.58-2.97, respectively. The peak viscosity, trough, breakdown viscosity, final viscosity, setback viscosity, peak time and pasting temperature ranged from 162.84±2.09 to 426.50±1.83 RVU, 77.96±2.71 to 195.59±8.91 RVU, 84.88±0.63 to 234.75±5.58 RVU, 158.92±4.34 to 293.17±1.34 RVU, 76.88±18.04 to 101.42±5.08 RVU, 4.10±0.03 to 5.93±0.00 min and 75.05±0.05 to 94.78±0.38 oC, respectively. The baking strength characteristics of the flour blends such as moisture, ash, color, wet gluten, zenleny dry protein and wet protein ranged from 11.55 to 12.55%, 0.50 to 1.25%, 88.65 to 90.55, 8.35 to 13.80, -2.35 to 41.25, 4.92 to 13.85% and 4.53 to 11.99 %, respectively. Moisture, ash, fibre, fat, protein and carbohydrate of the composite flour ranged from 7.57 to 11.87%, 0.42 to 2.40 %, 1.78 to 3.00%, 2.81 to 5.62%, 8.42 to 12.68% and 67.61 to75.99%, respectively. Flour lightness, redness and yellowness ranged from 33.22 to 54.10, -2.89 to-1.14, 5.94 to 9.35, respectively. The inclusion of Bambara groundnut flour had a significant effect on the functional (swelling index, water and oil absorption capacity), pasting (peak, trough and final viscosity) and proximate (ash, fat and carbohydrate) properties of the flour blends.

How Competitive Hydration between C 3 A and C 3 S in the Fast Dissolution Stage Affects the Hydration of Low-Heat Portland Cement Blended Pastes

How Competitive Hydration between C ₃ A and C ₃ S in the Fast Dissolution Stage Affects the Hydration of Low-Heat Portland Cement Blended Pastes

Long-Term Effects of External Sulfate Attack on Low-Carbon Cementitious Materials at Early Age

Placed in a sulfate-rich environment, concrete reacts with sulfate ions, influencing the long-term durability of reinforced concrete (RC) structures. This external sulfate attack (ESA) degrades the cement paste through complex and coupled physicochemical mechanisms that can lead to severe mechanical damage. In common practice, RC structures are generally exposed to sulfate at an early age. This early exposition can affect ESA mechanisms that are generally studied on pre-cured specimens. Moreover, current efforts for sustainable concrete construction focus on replacing clinker with supplementary cementitious materials, requiring a 90-day curing period, which contradicts real-life scenarios. Considering all these factors, the objective of this study is to explore ESA effects at an early age on cement-blended paste samples using various low-carbon formulations. The characterization techniques used demonstrated that the reference mix (100% CEM I) exhibits the weakest resistance to sulfate, leading to complete deterioration after 90 weeks of exposure. This is evident through the highest mass gain, expansion, cracking, formation of ettringite and gypsum, and sulfate consumption from the attacking solution. Conversely, the ternary mix, consisting of CEM I, slag, and metakaolin, demonstrates the highest resistance throughout the entire 120 weeks of exposure. All the blended pastes performed well in the sulfate environment despite being exposed at an early age. It can be recommended to substitute clinker with a limited quantity of metakaolin, along with blast furnace slag, as it is the most effective substitute for clinker, outperforming other combinations.

Evaluation of pasting and anti-nutritional properties of wheat-plantain flour blends fortified with velvet bean

Wheat flour is a powder made from the grinding of wheat used for human consumption. It is a flour of choice in confectionary industries due to the component gluten Plantain is a popular dietary staple crop in Nigeria due to its versatility and good nutritional value. It is starchy, the less sweet variety can be used either ripe or unripe, they are very good sources of carbohydrate for more than 50 million people. Velvet bean (Mucuna pruriens), belongs to the Fabaceae family, it is part of various legumes which is not commonly used by people as a result of anti-nutrients. Velvet bean is commonly grown in the tropical and subtropical part of the world. This study therefore investigated effect of inclusion of velvet bean on the pasting and anti-nutritional factors of wheat-plantain flour blends. The procured velvet bean and plantain were thoroughly washed, peeled, dried and converted into flours. Wheat, plantain and Velvet flours composite were prepared in the ratio 240:37.5:22.5, 210:60:30 and 150:105:45 respectively and 100% wheat flour was used as the control. The samples were evaluated for their pasting and anti-nutritional properties. pasting revealed that peak ranged from 1928.50-4972.50 Trough, 1054.00-3563.00, breakdown 692.50-1408.00, final viscosity 2077.00-5789.50, setback 968.00-2226.00, peak time 5.10-5.79 min and pasting temperature 80.79-83.14 0C. Anti-nutritional factors revealed that Tannin ranged from 20.01-219.25, Oxalate 24.56-448.79, trypsin inhibitors 10.31-20.70, Phytate 5.67-6.44 and Saponin 0.00-1.87 mg/100g. Addition of plantain and velvet beans flours significantly (p < .05) improved the final viscosity, peak, trough and the setback of the flour blends. The phytochemical properties of the composites indicated significant (P < .05) oxalate, phenolic, flavonoid and saponin increased which makes them suitable as anti-aging, anti-inflammatory, anti-oxidant, anti-hypertensive agents

Technological, quality and nutritional characteristics of Ramen noodles with wheat flour partially substituted by water chestnut flour

Ramen noodles were prepared by partially supplementing traditional wheat flour with water chestnut flour (WCF) at 30, 40 and 50% levels w/w. The composition, pasting and farinograph indices of flour blends were studied. Noodles were analysed for colour, radical scavenging and functional characteristics. Time for dough development, stability and farinograph quality number declined significantly from 5.250±0.07 to 1.20±0.01 min, 6.45±0.07 to 1.31±0.01 min and 81.50±0.71 to 18.50±0.71, respectively, after replacement. Statistically significant increment in pasting temperature (60.91±0.01 to 72.05±0.07°C), peak viscosity (1094.05±0.07 to 1099.25±0.35 Brabender Unit, BU), breakdown (310.05±0.07 to 376.05±0.07 BU), hot paste (782.05±0.07 to 996.10±0.14 BU) and cold paste viscosities (1548.10±0.14 to 1701.25±0.35 BU) were found with the addition of WCF. Non-traditional ramen exhibited significantly improved fibre, antioxidant potential and mineral content with significant reduction in % fat and caloric count. The colour variation data in ramen noodles were: L* (66.35–57.86); a* (0.24–2.08); and b* (4.03–4.47). Texture hedonic scores varied between 8.38 and 7.57 with chestnut flour level increment. Hardness of Ramen noodles samples ranged between 13.9 and 19.8 N.

Characterisation of calcined waste clays from kaolinite extraction in alkali-activated GGBFS blends

Metakaolin is a well-studied supplementary cementitious material (SCM) and precursor in alkali-activation. The utilisation of limited kaolinite content clays generated from large-scale industrial activity, denoted as waste clays, in alkali-activation is still largely unexplored. This paper investigates the use of five samples of calcined waste clays from different locations in a kaolinite extraction site as precursors in alkali-activated cements (AACs). Calcined waste clay precursors are blended with ground granulated blast furnace slag (GGBFS) and activated with sodium silicate. The physical and chemical properties of the calcined waste clays are characterised. Both Chapelle and R3 tests for pozzolanic reactivity are examined based on calcined waste clay properties. The R3 test data obtained for sieved particle fractions < 63 µm show marked improvement in the case of C4, elucidating potential calcined waste clay behaviour with prior processing in alkali activated systems. Clay particle size distribution and morphology are identified as key factors to be considered for initial calcination and in mix designs, strongly affecting both the fresh properties and workability of blended pastes. Good workability is highlighted as being crucial for achieving well-behaving calcined waste clay blended binders with resulting dense microstructures and high strength values, comparable with other reported GGBFS systems. Quartz, muscovite, and alkali-feldspar present in the calcined waste clays remain stable throughout alkali-activation. Reaction of the amorphous phase fraction present in the calcined waste clays results in the formation of additional cross-linked gel. A replacement level of up to 20 wt% calcined waste clay is found to exhibit similar compressive strengths to pure GGBFS binders, whilst achieving lower porosity within the bulk. This study provides a methodology for characterising the behaviour of calcined waste clays in alkali-activated systems and a proof of concept in the formulation of novel binders that incorporate waste clays.

Recycling of clay brick powder to improve the microstructure and mechanical properties of oil well cement pastes at high temperature and high pressure conditions

In oil well cementing involving high temperature and high pressure (HTHP), silica sources are usually incorporated into oil well cement to prevent its strength retrogression. This paper aims to use recycled clay brick powder (CBP), a silica-enriched material, as an alternative to the use of silica flour (SF) to inhibit the strength retrogression of the cement pastes after thermal cycling curing at 300 °C/13.0 MPa. Pure pastes (G), blended pastes with 40 wt% SF (40SF) and blended pastes with 40 wt% CBP (40CBP) were prepared to comparative analysis. The results showed that 40CBP and 40SF exhibited lower compressive strength and poorer pore structure than the G samples at 50 °C. However, the incorporation of CBP could effectively improve the compressive strength of the cement at 300 °C/13.0 MPa compared to that of the G paste. Mineralogical analysis indicated that xonotlite phases were the main crystalline phases in 40CBP and 40SF after thermal cycling curing. Compared to reinhardbraunsite in G samples, xonotlite could improve the pore structure and make the microstructure denser. In addition, there are some hibschite phases in 40CBP, which may make its compressive strength slightly lower than 40SF. Nevertheless, the environmental impact and cost analysis showed that the energy intensity and CO2 emissions of 40CBP were significantly lower than those of G and 40SF, and it had great cost advantages. This study is expected to provide some help in the rational recycling of CBP and reducing the CO2 emissions in cement production.

Distribution and dynamics of water in the blended pastes unraveled by thermoporometry and dielectric properties

Water distribution in hardened paste and its dynamics determine many properties related to durability. Moisture distribution was determined by thermoporometry combined with vacuum drying. Dynamics of confined water were measured by broadband dielectric spectroscopy. Water in pores <2.4 nm cannot form tetrahedral ice structure due to geometrical constraints. The volume of unfrozen water (in interlayer and gel pores) decreases after the drying at all relative humidity levels. An evident coarsening of gel pores occurs with drying between 75 % and 55 % RH. 35 % fly ash and slag have limited effects on relaxation processes of silanol hydroxyl groups and interlayer water. However, they slow down the dynamics of water in small gel pores, thereby enhancing interactions between water and the solid interface. This study clarifies the microstructural changes during the drying and reveals the sensitivity of water dynamics to the chemical environment in C-S-H of blended pastes.

Carbon Dioxide Conversion and Use as Admixture for Calcined Clay Blended Pastes

Carbon Dioxide Conversion and Use as Admixture for Calcined Clay Blended Pastes

Enhanced mortar strength and resistance to seawater degradation in the presence of calcined coal-series kaolin

The hydration process of blended mortars and its resistance to seawater degradation in the presence of calcined coal-series kaolin (CCK) was investigated in this study. The TG tests were used to quantify the effect of calcination temperature on the chemical-bound water content of the blended pastes while the XRD tests were applied to analyze the main crystalline hydration phases of the blended pastes, which were further quantified using the Rietveld-XRD refinement. In addition, microcalorimetric tests were used to characterize the degree of hydration. The hydration process of the blended mortars was further investigated in detail via combining SEM and pozzolanic activity tests. Based on this, the resistance to seawater degradation of the blended mortars with added CCK were verified via the expansion and strength loss tests, and the mechanism was analyzed via the electric flux and the total Cl− content tests. The optimal percentage of CCK (12%) was determined via a linear weighted sum method. The CCK obtained at 800 °C had the highest pozzolanic activity, promoting hydration reactions to form new gels (C-S-H, C-A-H and C-A-S-H) at active nucleation sites in mortars. These further enhanced both the flexural and compressive strengths (the compressive strength reached ∼53.7 MPa) of the blended mortars. However, CCK reduced the generation of Mg(OH)2, AFt and Friedel’s salt, decreasing seawater degradation to the mortars. Therefore, this study provides a new strategy to prepare high-strength mortar with high resistance to seawater degradation.

Promoting the dissolution of slag in blended cement via adding polyaluminum sulfate and controlling the inner spatial zonation

In this study, polyaluminum sulfate (PAS) is added into slag blended cement pastes to controll the inner zonation of the hydrotalcite-like phase. Nano-structure of inner hydration product region of slag after adding PAS is studied using TEM. Mean reaction degree of slag in the blended pastes was calculated using the deconvolution of 29Si NMR results. Adding PAS causes a hydrotalcite-like phase zonation with a loosen nanostructure in the inner region of slag, facilitating ion diffusion and the continuous growth of hydration products. Thus, promoted hydration degree of slag, enhanced compressive strength and refined pore structure are obtained by adding PAS in the blended pastes. Adding PAS by 2% promotes dissolution of slag particles and increases the mean reaction degree of slag in the blended pastes at 14, 28 and 56 d. Adding PAS by 2% decreases the porosity of blended pastes to 12.63%, thus increasing the compressive strength up to 20% at 28d.

Recycled mineral admixtures based on recycled clay brick

The utilization of construction demolition waste as recycled mineral admixtures can simultaneously reduce cement consumption and the environmental impact on the construction industry. Thus, recycled mineral admixtures based on recycled clay brick powder (CBP) were prepared and circulating fluidized bed combustion (CFBC) fly ash was introduced as the activity compensation and sulfate excitation component. The effects of the hydration of recycled mineral admixtures on the mechanical performance and drying shrinkage of mortar were investigated. The results indicated that the incorporation of CFBC fly ash into the blended cement paste accelerated the hydration of C3S and shortened the induction period. The fly ash also promoted the secondary hydration of C3A and the conversion of ettringite to the monosulfate phase. The CBP consumed portlandite to form a calcium–silicate–hydrate gel at a later age, whereas CFBC fly ash promoted the pozzolanic reaction to occur earlier. The incorporation of the CBP and CFBC fly ash increased the porosity and pore volume of the blended paste.

Rheological behavior and early-age reaction kinetics of Portland cement-sulphoaluminate cement blend pastes containing superplasticizer and cellulose ether

The combination of Portland cement (PC) and sulphoaluminate cement (CSA) has the potential to improve the mechanized construction efficiency of cement-based materials, but its rheological behavior still needs to be considered to deeper understand the evolution of workability. Therefore, the blend pastes with different PC-CSA ratio were prepared. To achieve good initial workability, cellulose ether and superplasticizer were added. The shear stress – shear strain rate data of each paste at different resting time was obtained by a rheometer. Herschel-Bulkley (H-B) model was used to imitate the rheological data, and the evolution curve of yield stress with resting time of each sample was achieved. It was found that sample with higher CSA content showed a faster increase in yield stress over time. Furthermore, isothermal calorimetry was conducted to reveal the reaction kinetics of the rheological evolution of the fresh pastes referring to Johnson-Mehl-Avrami-Kolmogorov model. The results showed that CSA accelerated the nucleation and crystallization process of ettringite (AFt), which is contributed to the yield stress. Meanwhile, a novel technique, 1H low-field nuclear magnetic resonance (NMR), was firstly applied to character the early-age reaction process of PC-CSA blend system by monitoring the evaporative water content changes in the pastes. The result was that the relative content of evaporated water in the paste with higher CSA content decreased faster, which is also beneficial for the yield stress. These methods for evaluating reaction kinetics effectively validated the rheological behavior of the slurry, and established a correlation with the rheological parameter, which had not been identified in previous studies.

Effects of construction waste powder on micro–macro properties of green high-strength cement paste with low water-to-binder ratio

The replacement of cement with ground construction waste powder is considered a sustainable strategy for the production of high-strength cement-based materials. This study investigated the influences of construction waste powder types and replacements on the micro–macro characterizations of green high-strength cement paste with low water-to-binder (w/b) ratio. The results highlighted that paste with 0.2 w/b ratio contained abundant hydration products and un-hydrated cement, and construction waste powder exerted good nucleation sites and filling effects in paste. The mix of construction waste powder did not change the hydration product types but reduced calcium hydroxide content in paste. Mixing appropriate ground brick powder up to 50% declined paste drying shrinkage, but the paste drying shrinkage continuously increased as ground paste/mortar/concrete powder content increases. The maximum drying shrinkage of paste with 50% ground brick powder and 50% ground concrete powder was 3.3% lower and 32.4% higher than the plain paste. When ground brick powder content was below 50% or ground paste/mortar/concrete powder content was below 30%, construction waste powder blended paste had similar or better compressive strength than plain paste, but incorporating 70% construction waste powder reduced the paste compressive strength. When construction waste powder content was identical, ground brick powder blended paste had higher compressive strength than paste containing ground paste/mortar/concrete powder. Incorporating appropriate dosage of ground brick powder reduced the transport properties and total porosity of paste, whereas the transport properties and total porosity both increased with ground paste/mortar/concrete powder incorporation. Optimizing construction waste powder types and contents can prepare green paste owning high-strength and low transport properties.

The impact of coal gasification slag powder on fluidity, rheology and viscoelasticity properties of fresh cement paste

Coal gasification slag (GS) is a potential pozzolanic industrial waste discharged during coal gasification. The study aimed to investigate the effect of finely ground GS powder on the fluidity, rheology and viscoelasticity properties of cement paste, which is essential for utilizing GS as a supplementary cementitious material for building materials. The research revealed that the morphology, physical filling effect, and particle size distribution of GS powder played a vital role in the workability of cement. The particle size distribution of the GS-cement system followed the Rosin-Rammler distribution model, and the width of the particle size distribution negatively correlated with paste fluidity. The rheological characteristics of blended paste transitioned from Bingham to modified Bingham fluid with increased GS powder content, showing shear thinning. Plastic viscosity can predict the fluidity and thixotropy of the paste. GS powder at 10% content broadened the particle size distribution, improved fluidity and rheological properties, with minimal effect on viscoelastic characteristics. With increased GS powder content, plastic viscosity, yield stress, and thixotropy of blended paste increased continuously, resulting in a slow transition from viscosity to elastic solid. Extending mechanical grinding time improved the fineness and activity of GS powder, optimized the particle size distribution, and reduced water demand, minimizing negative effects.