Addition Of nano-CaCO3 Research Articles

Influence of additive nano calcium carbonate (CaCO3) on SAE 10W-30 engine oil: A study on thermophysical, rheological and performance

Researchers have used nanomaterials as additives in base oil to improve its specifications, especially to minimize wear and friction during its applications. In this study, calcium carbonate (CaCO3) nanoparticles were selected as an additive to serve as a protective layer between components and anti-wear properties. In this study, calcium carbonate (CaCO3) nanoparticles were selected as an additive to serve as a protective layer between components and anti-wear properties. Nano lubricant samples were prepared using mass variations of CaCO3 and SAE 10W-30 base oil with concentrations of 0.05, 0.1, 0.15, and 0.2%, then homogenized. The nanolubricant samples obtained were analyzed for thermophysical, rheological properties and lubricant performance with the addition of nano CaCO3 in improving the wear resistance of FC25 cast iron. The results of thermophysical and rheological properties analysis suggest that the nanolubricant has better tribological properties compared to base lubricants. The highest values of thermal conductivity, density, and viscosity (40 oC) are 0.139 W/m.K, 812.203 kg/m3, and 106 mPa.s (40 oC). Meanwhile, the highest CoF, disc mass loss, and surface roughness of nanolubricant are 0.0706, 0.0037 grams, and 0.50 µm, respectively. These results indicate that the greatest wear-reducing agent is from the nanolubricant with the addition of CaCO3 nanopowder additives at 0.1 wt% concentration. These results are expected to give significant insights into the advancement of nano technology-based lubricants in the future.

Innovative use of wet carbon conversion in alkali-activated slag: Improved microstructures and mechanical characteristics

Nano-calcium carbonate (nano-CaCO3) has garnered significant attention due to its remarkable efficacy in enhancing the properties and microstructure of concrete. In this study, the wet carbon conversion method was used to synthesize solid nano-CaCO3 from CO2, which was then added to AAS. Subsequently, the compressive strength and resistivity of the AAS mortar were assessed, and the AAS paste underwent microscopic characterization using experimental methods, including X-ray diffraction (XRD) and Fourier-transformed infrared (FTIR), and scanning electron microscope (SEM) et.al. The effects of the nano-CaCO3 on the microstructure, mechanical characteristics, and durability of the AAS were determined. The microscopic analysis results clearly demonstrate that the nano-CaCO3 prepared using this method exerts significant physical and chemical effects, leading to a notable improvement in the compactness of the AAS microstructure. Moreover, the experimental findings provide further confirmation that the addition of nano-CaCO3 results in a substantial enhancement of both the compressive strength and resistivity of AAS mortar, particularly in the early stages. Specifically, the inclusion of 6% nano-calcium carbonate led to a remarkable 29.8% increase in compressive strength at 1 curing day. Furthermore, the analysis of carbon dioxide emissions from AAS reveals that incorporating nano-CaCO3 effectively reduces the carbon footprint associated with AAS. This implies that adopting this approach not only enhances the performance of AAS but also contributes to a reduction in the environmental impact, thus actively promoting sustainable construction and engineering projects.

Rate-sensitive pullout resistance of smooth-steel fibers embedded in ultra-high-performance concrete containing nanoparticles

Single-fiber pullout tests for smooth-steel fibers embedded in ultra-high-performance concrete (UHPC) containing nanoparticles (NPs) were conducted at various pullout speeds (0.0167–500 mm/s). Three types of NPs, namely, nano-CaCO3, nano-SiO2, and nano-CNT, were added to UHPC at dosages between 1 and 3 wt % of cement. The addition of NPs to UHPC notably increased the rate sensitivity of fiber pullout resistance. Among the NPs, the addition of nano-CaCO3 (3 wt %) produced the highest rate sensitivities for the dynamic increase factors (DIFs) of both τeq (1.95) and τpeak (2.06), whereas UHPC without NPs obtained the lowest rate sensitivity of τeq (DIF = 1.18), and UHPC containing 3 wt % nano-CNT had the lowest rate sensitivity of τpeak (DIF = 1.62). Nanoindentation, scanning electron microscopy, and energy-dispersive X-ray spectroscopy tests revealed that the higher amount of C–S–H at the fiber–matrix zone produced higher pullout resistance and rate sensitivity.

Conversion of CO2 and Its Utilization in the Preparation of Cement-Slag-CaCO3 Ternary Blends

A reduction in CO2 emissions is necessary in the concrete industry. This study proposes a CO2 conversion technique by which CO2 gas is converted into solid nano CaCO3 and used to replace the partial binder of cement-slag blends in ratios of 2%, 4%, and 6%. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy analyses confirmed the formation of hemicarboaluminate (Hc) and monocarboaluminate (Mc) due to the chemical reaction between nano CaCO3 and the Al2O3 phase in the binder. XRD analysis revealed that at 28 days, the addition of nano CaCO3 can inhibit the transformation of ettringite (AFt) to monosulfate (AFm). As the contents of nano CaCO3 increased, the hydration heat, strength, ultrasonic pulse velocity (UPV), electrical resistivity, and combined water content increased. The degree of increment of the electrical resistivity was more pronounced than that of the strength. For various specimens, the strength and combined water content presented a linear relationship, and the strength and UPV presented an exponential function. The reduction rate of normalized CO2 emissions (the ratio of CO2 emissions of the paste to its strength) was much higher than the replacement percentage of nano CaCO3. This was because nano CaCO3 increased the late strength and had a negative CO2 emission value.

Effects of nano-CaCO3 and nano-iron phosphate on microstructure and properties of SiO2 porous ceramics prepared by direct foaming

SiO2 porous ceramics are often used in industrial kilns for thermal insulation. Burning loss method is the main method for preparing SiO2 porous ceramics at present, but there are problems of environmental pollution and uneven pore distribution. Meanwhile, SiO2 is prone to cracking due to crystal-to-crystal transformations. In order to overcome above problems, in this study, nano-CaCO3 and nano-iron phosphate with high activity have been used to stabilize the crystal-to-crystal transformations of SiO2, and SiO2 porous ceramics have been prepared by simple and environmental direct foaming method. Results show that the addition of nano-CaCO3 and nano-iron phosphate can promote the formation of tridymite and densification of SiO2 porous ceramics, which can also increase their pore wall thickness and improve compressive strength. In addition, the compressive strength of SiO2 porous ceramics is proportional to their relative density, which is consistent with the Ashby’s theory. And their thermal conductivity is well matched with the universal model, indicating that SiO2 porous ceramics have complex pore structures. Comparing the effects of nano-CaCO3 and nano-iron phosphate on SiO2 porous ceramics, it is concluded that nano-CaCO3 as the mineralizer is better than nano-iron phosphate. This study enriches the fabrication technology of energy-saving and environmentally friendly SiO2 porous ceramics, which is of great significance to the practical production and application of SiO2 porous ceramics.

Cracking failure behavior of high strength concrete containing nano-CaCO3 at early age

Nano-calcium carbonate (CaCO3) has been added to high strength concrete (HSC) to reduce cement usage, control greenhouse gas emissions, increase durability, and control excessive shrinkage of HSC. Many investigations on the mechanical properties and shrinkage of HSC containing nano-CaCO3 have conducted. However, the early-age cracking failure behavior of that considering temperature, shrinkage, restrained stress, and tensile creep simultaneously was rarely investigated. Temperature stress test machine, which could measure these factors simultaneously, was used to investigate the influence of nano-CaCO3 contents (0%, 1%, 2%, and 3% by weight of cement powder) on the early-age cracking failure behavior of HSC in the present investigation. Mechanical properties of HSC containing nano-CaCO3 were tested. The addition of nano-CaCO3 to HSC improved the mechanical properties, and reduced the tensile creep as well as autogenous shrinkage of that at early age. A simplified stress-strain failure criterion was proposed.

Simulation of hydrophobic lotus leaves for preparing hydrophobic starch blending films based on starch-based graphite oxide carbon

Inspired by the hydrophobic mechanism of lotus leaf, hydrophobic starch blending films based on starch-based graphite oxide carbon(S-GOCs) was synthesized, while nano calcium carbonate (nano-CaCO3) and hydrophobic plasticizer (acetyl tributyl citrate, ATC) were also introduced for further improving its water resistance. The TEM, SEM, XRD, and FTIR characterizations were used to analyze the properties of S-GOCs. With increased addition of the S-GOCs, the water contact angle (θw) increased prominently (θw: from 35.5° to 91.5°), the moisture content (MC) and the water vapor permeability (WVP) of the starch blending films significantly decreased (MC: from 22.19% to 14.12%; WVP: from 3.86 to 3.27 g m m−2 s−1 Pa−1). The addition of the nano-CaCO3 and ATC further promoted its waterproof properties with the highest θw, the lowest MC, and WVP (θw = 112.2°, MC = 11.15%, WVP = 2.88 g m m−2 s−1 Pa−1). Although the S-GOCs resulted in a higher volume dissolution (the total soluble matter (TSM) increased from 26.26% to 32.13%), the incorporation of nano-CaCO3 and ATC could minimize the solubility of the films (TSM = 23.40%). Careful evaluation of tensile strength (TS) and elongation at break (E) of the films has concluded that the S-GOCs could make the films more flexible, and the extra addition of nano-CaCO3 and ATC have no adverse effect on this balance. Combined with the result of surface free energy and the analysis of AFM and FTIR, the hydrophobic mechanism of the starch blending films was illustrated, which was due to the synergistic effect of reducing surface free energy, improving surface roughness and structure water resistance. Finally, a simple application in the packing field was developed to envisage the prospect of starch-blending film.

The Influence of Nano-CaCO3 on the Mechanical and Dynamic Thermo-Mechanical Properties of Core–Shell Structured Wood Plastic Composites

Using bamboo residue and high-density polyethylene (HDPE) as the main raw materials, core–shell structured wood plastic composites (WPCs) with nano-CaCO3 filling shell were prepared by coextruded technology. The effect of nano-CaCO3 contents on the flexural properties, impact strength and dynamic thermo-mechanical properties of the core–shell structured WPCs were investigated. And the value of core–shell interface interaction parameter was calculated by dynamic thermodynamic parameters. The results showed that the flexural strength increased by 48.1% and 40.3% when it was loaded with 10%–15% nano-CaCO3, compared to the HDPE shell composites, respectively. While nano-CaCO3-filled HDPE shell had lower impact strength in comparison with HDPE shell, the field emission scanning electron microscope revealed proper interfacial adhesion between the core and shell layers. The storage modulus of core–shell structured WPCs increased as nano-CaCO3 contents increased, but the values were lower than that of the HDPE shell. Addition of nano-CaCO3 caused an increase in the glass transition temperature (Tg) of the core–shell structured WPCs, loss factor (tanδ) of the core–shell structured WPCs decreased. The value of the core–shell interface interaction parameter of the core–shell structured WPCs increased significantly after the nano-CaCO3 loading reached 15%, which was consistent with the bending test results. These findings demonstrate that the core–shell structured WPCs have excellent properties filling with nano-CaCO3 in the shell layer, and bamboo residue is added to the core layer.

Laboratory investigation of the effect of nano Caco3 on rutting and fatigue of stone mastic asphalt mixtures

In this research, the influence of Nano Caco3 as an additive on the mechanical characteristics of stone mastic asphalt (SMA) mixtures is investigated. For this purpose, asphalt binder 60–70 is modified with different ratios of Nano Caco3 to create the SMA samples. Indirect tensile fatigue, wheel track, and indirect tensile strength tests were conducted to evaluate fatigue, rutting, and moisture damage resistance of modified and control samples. The results revealed that by adding Nano Caco3 particles, the fatigue life of SMA mixtures is increased and their final strain is reduced. Nano Caco3 has a good potential to delay the formation and propagation of fatigue cracks in the SMA mixture. The results of the wheel track test demonstrated that Nano Caco3-modified SMA mixtures had lower rut depth than control mixtures. Also, the rutting performance of the SMA mixture was improved at high temperatures and stress levels. The results of the indirect tensile strength test showed that the addition of Nano Caco3 increased the moisture damage resistance of the SMA mixture and improved its performance when it was subjected to continuous exposure to water. It was observed that almost in all cases, modified SMA mixtures with a Nano ratio of 0.9%, exhibit the best behavior.

Effect of nano calcium carbonate (nano CaCO3) on the strength and consolidation properties of clayey sand soil

Nanotechnology is extensively used in engineering to improve systems, characteristics and standards. Various techniques can be used for soil improvement in road embankment and geotechnical engineering. The present study examined the effect of nano calcium carbonate (nano-CaCO3) on clayey sand soil using uniaxial and consolidation tests on specimens containing 10%, 20% and 30% kaolinite and bentonite, and 0.3%, 0.7%, 1.1% and 1.5% nano-CaCO3 at curing times of 7, 14 and 28 days. The results showed that mixtures containing 10% and 20% clay plus 0.7% nano-CaCO3, and specimens with 30% clay and 1.1% nano-CaCO3, exhibited optimal UCS and consolidation properties. XRD patterns indicated an increase in the intensity of the phases (calcium silicate hydrate, kaolin, calcite, etc) after the addition of nano-CaCO3 to the soil. SEM micrographs showed better filling of voids after the addition of nano-CaCO3 to both clay types. The amounts of these products were higher in the bentonite specimens.

Experimental and Numerical Evaluation of the Effect of Nano Calcium Carbonate on Geotechnical Properties of Clayey Sand Soil

The effect of nano-CaCO3 on the geotechnical properties of clayey sand (SC) soil was investigated. SC soil containing 10%, 20% and 30% clay and 0.3%, 0.7%, 1.1% and 1.5% nano-CaCO3 were cured for 7, 14 and 28 days and then subjected to uniaxial compression testing. The experimental results were analyzed numerically by the group method of data handling using an artificial neural network. Crystalline phases were analyzed by x-ray diffraction (XRD) to study the microstructure of soil specimens improved with nano-CaCO3. The addition of nano-CaCO3 to SC specimens, especially those with lower clay contents, increased their uniaxial compressive strength and the compressive strength increased over time. An optimum nano-CaCO3 level of 0.7% was determined for soil containing 10% and 20% clay and 1.1% for soil containing 30% clay. The results indicated a decrease in deformation and increase in stiffness of the soil with the addition of nano-CaCO3. The effect of nano-CaCO3 on the ultimate compressive strength of the soil in the XRD patterns indicated an increase in the recrystallization of the particles. Numerical analysis of the experimental results found a correlation for predicting the uniaxial compressive strength of the improved SC soil with a mean error of 4%.

Multiple effects of nano-CaCO3 and modified polyvinyl alcohol fiber on flexure–tension-resistant performance of engineered cementitious composites

Nanomaterial modification and fiber reinforcement are both effective modifications for concrete toughening. In this study, the cement matrix was reinforced by a combination of nanomaterials and surface-modified polyvinyl alcohol (PVA). The modification of PVA involves the treatment of interface weakening, which is based on the enhancement of the slip effect. The workability and static mechanical properties of engineered cementitious composites (ECCs) were studied, and the micromorphology of the fiber and matrix after bending failure was observed through scanning electron microscopy. Different nanomaterial contents and concentrations of PVA were designed in the experiment, the purpose of which is to investigate the mechanism of the effect of multiple superposed on the toughening effect of ECCs. The research demonstrated that the direct addition of traditional PVA fiber and nanomaterials adversely affects the workability of ECCs, but it can be improved by fiber modification and ultrasonic dispersion of nanomaterials. An experimental study on the compressive properties showed that, with the increase in PVA fiber modification concentration, the compressive strength decreased, but the addition of nano-CaCO3 improved the strength of the matrix, thereby compensating for the strength loss. Four-point bending and tensile tests demonstrated that both PVA fiber modification and the addition of nano-CaCO3 affected the flexural properties of ECCs to some extent. PVA fibers modified with 1% and 2% nano-CaCO3 at vinyl acetate ethylene concentrations of 25% and 50% can improve the toughness of ECCs. Nano-CaCO3 can improve the toughness of ECCs by improving the compactness of the matrix structure and fiber interface, while PVA fiber can supplement the defects of the matrix structure by bridging and sliding and have a positive superposition effect on the toughness of the material after proper treatment.

Performance evaluation of basalt fiber-reinforced geopolymer composites with various contents of nano CaCO3

High carbon footprint of cement production is the major drawback of plain cement concrete resulting in environmental pollution. Geopolymer composites paste can be effectively used as an alternative to Portland cement in the construction industry for a sustainable environment. The demand for high-performance composites and sustainable construction is increasing day by day. Therefore, the present experimental program has endeavored to investigate the mechanical performance of basalt fiber-reinforced fly ash-based geopolymer pastes with various contents of nano CaCO3. The content of basalt fibers was fixed at 2% by weight for all specimens while the studied contents of nano CaCO3 were 0%, 1%, 2%, and 3%, respectively. The compressive strength, compressive stress-strain response, flexural strength, bending stress-strain response, elastic modulus, toughness modulus, toughness indices, fracture toughness, impact strength, hardness, and microstructural analysis of all four geopolymer composite pastes with varying contents of nano CaCO3 using scanning electron microscopy (SEM) were evaluated. The results revealed that the use of 3% nano CaCO3 in basalt fiber-reinforced geopolymer paste presented the highest values of compressive strength and hardness while the use of 2% nano CaCO3 showed the highest values of flexural strength, impact strength, and fracture toughness of composite paste. The SEM results indicated that the addition of nano CaCO3 improved the microstructure and provided a denser geopolymer paste by refining the interfacial zones and accelerating the geopolymerization reaction.

Fracture Resistance of Simulated Immature Teeth Reinforced with Different Mineral Aggregate-Based Materials.

This study assessed the fracture resistance of simulated immature teeth reinforced with calcium aluminate cement (CAC) or mineral trioxide aggregate (MTA) containing calcium carbonate nanoparticles (nano-CaCO3). The microstructural arrangement of the cements and their chemical constitution were also evaluated. Forty-eight canines simulating immature teeth were distributed into 6 groups (n=8): Negative control - no apical plug or root canal filling; CAC - apical plug with CAC; CAC/nano-CaCO3 - apical plug with CAC+5% nano-CaCO3; MTA - apical plug with MTA; MTA/nano-CaCO3 - apical plug with MTA+5% nano-CaCO3; and Positive control - root canal filling with MTA. The fracture resistance was evaluated in a universal testing machine. Samples of the cements were analyzed under Scanning Electron Microscope (SEM) to determine their microstructural arrangement. Chemical analysis of the cements was performed by Energy Dispersive X-ray Spectroscopy (EDS). The fracture resistance of CAC/nano-CaCO3 was significantly higher than the negative control (p<0.05). There was no significant difference among the other groups (p>0.05). Both cements had a more regular microstructure with the addition of nano-CaCO3. MTA samples had more calcium available in soluble forms than CAC. The addition of nano-CaCO3 to CAC increased the fracture resistance of teeth in comparison with the non-reinforced teeth. The microstructure of both cements containing nano-CaCO3 was similar, with a more homogeneous distribution of lamellar- and prismatic-shaped crystals. MTA had more calcium available in soluble forms than CAC.

CO2 Sequestration in the Production of Portland Cement Mortars with Calcium Carbonate Additions

The paper presents the obtention and characterization of Portland cement mortars with limestone filler and nano-calcite additions. The nano-calcite was obtained by the injection of CO2 in a nano-Ca(OH)2 suspension. The resulted nano-CaCO3 presents different morphologies, i.e., polyhedral and needle like crystals, depending on the initial Ca(OH)2 concentration of the suspension. The formation of calcium carbonate in suspensions was confirmed by X-ray diffraction (XRD), complex thermal analysis (DTA-TG), scanning electron microscopy (SEM) and transmission electron microscopy (TEM and HRTEM). This demonstrates the viability of this method to successfully sequestrate CO2 in cement-based materials. The use of this type of nano-CaCO3 in mortar formulations based on PC does not adversely modify the initial and final setting time of cements; for all studied pastes, the setting time decreases with increase of calcium carbonate content (irrespective of the particle size). Specific hydrated phases formed by Portland cement hydration were observed in all mortars, with limestone filler additions or nano-CaCO3, irrespective of curing time. The hardened mortars with calcium carbonate additions (in adequate amounts) can reach the same mechanical strengths as reference (Portland cement mortar). The addition of nano-CaCO3 in the raw mix increases the mechanical strengths, especially at shorter hardening periods (3 days).

Systemic multi-scale approaches to predict the flowability at various temperature and mechanical properties of cement paste modified with nano-calcium carbonate

In this study, the effect of nano-calcium carbonate (nano-CaCO3) as an additive to the cement paste was evaluated and quantified. Microstructure tests, experimental tests, and modeling were conducted to predict the cement paste's rheological properties namely yield stress (yield point), shear stress limit, viscosity, and stress at the failure of cement at fresh and hardened stages. The cement paste modified with nano-CaCO3 was tested at a water-to-cement ratio of 0.35 with 0.45 and temperatures ranging from 25 to 75 ⁰C. The addition of nano-CaCO3 increased the shear stress limit and the yield stress (τo) by 10.28 to 51.35% and 14.36 to 91.4%, based on the nano-CaCO3 content, w/c, and temperature of the test. TGA tests showed that the 1% nano-CaCO3 additive reduces the weight loss of the cement at 800 ⁰C by 76% due to interacting with the nano-CaCO3 with the cement paste. The nonlinear regressions (NLR) model and Artificial Neural Network (ANN) technical approaches were used for the qualifications of the flow of slurry and stress at the failure of the cement paste modified with nano-CaCO3. Based on the statistical assessments of R and RMSE, the rheological properties such as yield stress, plastic viscosity, shear stress limit and compressive strength of cement paste modified with nano-CaCO3 can be well predicted in terms of w/c, nano-CaCO3 content, temperature, and curing time using two different simulation techniques. Based on the statistical assessments such as coefficient of correlation (R), root mean square error (RMSE), the NLR model is the most effective model to estimate rheological properties and compressive strength of the cement and it is performing better than the ANN model.

Evolution of Cracks in Nano-CaCO₃ Modified Pre-Disintegrated Carbonaceous Mudstone Under Cyclic Wetting and Drying.

To explore the evolution of cracks in the pre-disintegrated carbonaceous mudstone, wetting-drying tests were carried out on nano-CaCO₃ modified pre-disintegrated carbonaceous mudstone samples. The samples were prepared with aqueous solutions of different pH values. Scanning electron microscopy (SEM) was performed to clarify the mechanism of crack evolution of pre-disintegrated carbonaceous mudstone modified by nano-CaCO₃. The results showed that development of shrinkage and cracks was basically divided into three stages, i.e., the gestation stage, the rapid development stage and the stable stage. For the samples without nano-CaCO₃, the final crack rates and pore sizes of samples with pH = 3 and pH = 11 were larger than corresponding values of the sample with pH= 7. Moreover, final crack rate and pore size significantly decreased with the addition of nano-CaCO₃ suggesting that nano-CaCO₃ can effectively improve cracking resistance of pre-disintegrated carbonaceous mudstone.

Mechanical properties of the nano-CaCO3 and GB co-reinforced CF/PA6 composites

In this work, ternary nano-CaCO3/carbon fiber (CF)/PA6 composites and quaternary glass beads (GB)/nano-CaCO3/carbon fiber/PA6 were fabricated by melt-extrusion and laminating method. The effect of nano-CaCO3 content on the mechanical properties of nano-CaCO3/CF/PA6 composites was evaluated. It was found that the addition of nano-CaCO3 at 10 wt% could make a remarkable improvement of 15.1%, 53.2%, 8.5% and 76.0% in flexural strength and modulus, shear and impact strength respectively contrasted to CF/PA6 composites. The mechanical properties of nano-CaCO3 and glass beads co-reinforced carbon fiber/PA6 composites were enhanced obviously. In particular, the flexural strength and modulus, shear and impact strength reached 427.9 MPa, 19.8 GPa, 51.6 MPa and 87.4 kJ m−2 respectively when the glass beads content of 8 wt% and nano-CaCO3 content of 10 wt%, which were increased by 40.8%, 74.7%, 18.0% and 143.4% respectively compared with CF/PA6 composites, the strengthening and toughening effects of GB/nano-CaCO3/CF/PA6 composites were realized by the synergistic action of multi-scale reinforcements.

Effect of Synthesized Calcium Carbonate Nanoparticles on Fresh and Mechanical Properties of High Volume Natural Pozzolan Mortars

Concrete with high levels of Pozzolan suffers from poor early age strength development and an extended setting time and may therefore lead to construction delays thus limiting its use in the concrete industry. The main objective of this study has been to evaluate the effectiveness of calcium carbonate nano-particles (CCNPs) on improving the fresh and mechanical properties of high volume natural Pozzolan (HVNP) cement mortars. At the beginning, CCNPs have been synthesized in a simple and inexpensive way, and then the optimum content of nano-CaCO3 has been determined based on the highest compressive strength achieved by ordinary Portland cement mortar with different proportions of CaCO3 nanoparticles. In the end, the determined optimum content has been used in order to evaluate the effect of nano-CaCO3 on the properties of HVNP mortars containing 40% and 60% natural Pozzolan as partial replacement of cement. Scanning electron microscopy (SEM) and X-ray diffractometery (XRD) techniques have been used in order to investigate the microstructure, the properties, and the compositions of the synthesized nano-particles and the cement-Pozzolan mortars. CCNPs have been synthesized efficiently via the simple precipitation method and suitable sonication process has been used to disperse CaCO3 nanoparticles. The results have indicated that nano-CaCO3 has increased the compressive strength of the Pozzolan-cement mortars, and the best result has been obtained at an optimum content of 1% nano-CaCO3. The addition of nano-CaCO3 to the HVNP mortar improved its setting behavior; on the other hand, it has decreased its workability. However, this reduction in the workability has been offset by an increase due to partial replacement of cement by HVNP. Blending nano-CaCO3 with HVNP (40 and 60% replacement levels) has compensated for the low compressive and flexural strength at early ages of HVNP mortars. Thus, it has proved to be an effective way for improving the mechanical properties of high volume natural Pozzolan-cement mortars. The XRD and SEM results have confirmed that nano-CaCO3 has improved the early strength development and the microstructure of HVNP mortars by making it denser with less pores.

Laboratory performances of nano-particles/polymer modified asphalt mixtures developed for the region with hot summer and cold winter and field evaluation

In some regions with hot summer and cold winter, most modified asphalt mixtures cannot meet the requirement of high-temperature stability and low-temperature cracking resistance simultaneously very well, so rutting or cracking often occurs in these regions. This paper tries to use nano-CaCO3/SBR (Styrene butadiene rubber) and nano-ZnO/TiO2/SBS (Styrene–butadiene–styrene) composite modified asphalt mixtures to solve this problem. The properties of these two asphalt mixtures were compared with those of base, SBR modified and SBS modified asphalt mixtures through rutting, beam bending, immersion Marshall, freeze–thaw splitting, three-point bending fatigue and splitting tests. Results show that the high-temperature stability of nano-CaCO3/SBR composite modified asphalt mixture is better than that of SBR modified asphalt mixture, and their low-temperature cracking resistances are close. In addition, the water stability, fatigue performance, performance after ageing, and splitting strength of SBR modified asphalt mixture can be improved by the addition of nano-CaCO3. All of the performances mentioned above of nano-ZnO/TiO2/SBS composite modified asphalt mixture are better than those of base or SBS modified asphalt mixture. In summary, nano-CaCO3/SBR or nano-ZnO/TiO2/SBS composite modified asphalt mixture has good high-temperature stability and low-temperature cracking resistance and can be used in the regions with hot summer and cold winter.