Effect Of Colloidal Nano-silica Research Articles

The microscopic fracture model for determining the fracture behavior of self-compacting lightweight concrete

The fracture toughness (KIC) and tensile strength (ft) of concrete are critical parameters governing crack resistance. Concrete usually exhibits brittleness under flexure and tension, so this brittle fracture first occurs at the micro level. Many researchers have studied its fracture properties at the micro level. However, the theoretical model and calculation formulae do not reflect the influence of micro-material parameters on the corresponding fracture properties. In this paper, the microscopic fracture model of self-compacting lightweight aggregate concrete (SCLC) was developed, considering the parameters of micro-nano silica materials. First, the characteristic parameters, such as particle size, specific surface area, and unit weight of micro silica (MS) and colloidal nano-silica (CNS), were considered, and the calculation equation for fictitious crack growth length was proposed. Then, the micro-fracture model was developed, which was further used to calculate the fracture parameters KIC and ft of SCLC incorporated with micro-nano silica. The results are found to be consistent with the fracture parameters determined by the size effect model. In addition, the failure curves of different structural fracture modes of SCLC were established through the fracture parameters KIC and ft obtained from the microscopic fracture model, and the fracture modes of SCLC incorporated with MS and CNS were identified. The peak load of the minimum specimen size satisfying linear elastic fracture was also predicted. This research provides a new perspective for evaluating concrete fracture parameters, realizes the progressive prediction of concrete fracture performance from macro to micro, and fills in the research gaps in the existing knowledge base on the synergistic effect of MS and CNS to enhance the fracture performance of SCLC.

Effect of colloidal nano silica on the freeze-thaw resistance and air void system of portland cement concrete

The present study investigates the impact of colloidal nano silica (CNS) on the freeze-thaw durability of concrete, with a particular focus on understanding the fundamental mechanism via a systematic analysis of the air void system. Experimental results suggest that the incorporation of CNS increases the total air content of the sample while reducing the average void size. This phenomenon can be attributed to the remarkable capacity of CNS to stabilize air bubbles within the concrete matrix, by a heightened viscosity and lower surface tension of the fresh concrete mixture. The increase in air void chambers facilitates the release of internal stress during freezing expansion, thereby enhancing the freeze-thaw resistance of the concrete. Additionally, the inclusion of CNS results in the formation of a denser cement matrix that improves the water impermeability of the concrete and prevents the ingress of water and other potentially corrosive substances.

Effects of colloidal nanoSiO2 on the hydration and hardening properties of limestone calcined clay cement (LC3)

This research investigates the influence of colloidal nanosilica (CNS) on the hydration and hardening properties of Limestone Calcined Clay Cement (LC3). The sulfation degree for LC3 was first optimized based on the hydration heat, and the results suggested that gypsum increases the cumulative heat release during the hydration process of LC3, with a dosage of 2% by weight gypsum leading to the highest heat release. The effects of CNS on hydration reaction, fluidity, mechanical properties and microstructure of LC3 were then investigated. According to the results obtained from isothermal calorimetry and thermogravimetric analysis, CNS can considerably accelerate the reaction rate of the LC3 system. 3% and 5% by weight CNS can significantly improve the compressive strength of LC3 blends, especially at early ages of 3 and 7 days. The findings from this study lead to a better understanding of the modification effects of CNS on LC3 which subsequently provides an insight into regulation mechanism of CNS on LC3.

Influence of colloidal nanosilica on hydration kinetics and properties of CaO/CaSO4-activated slag binder

To solve the energy consumption and CO 2 emission during cement production, the new binders must be developed as an alternative to cement. CaO/CaSO 4 -activated slag binder is an eco-friendly and safe cementitious material; however, its low strength during initial stages limits its applications. In this study, colloidal nanosilica (CNS) was employed as an additive to improve the strength of CaO/CaSO 4 -activated slag binder, and the effects of CNS on the workability, hydration kinetics, hydration products (type, quantity, and polymerization degree), and binder microstructure were thoroughly investigated. A moderate CNS content, through its nucleation effect, significantly increased the hydration rate of the nucleation and crystal growth (NG), phase boundary interaction (I) and diffusion (D) processes, which generated large quantities of calcium aluminosilicate hydrate (C-A-S-H) gel in the initial hydration stage. Meanwhile, the addition of CNS improved the polymerization degree of C-A-S-H gel. This amorphous reactant well-filled the pore space between slag particles and yielded a compact microstructure, consequently enhancing the binder strength. Considering the reduction in fluidity and the increase in production cost, the CNS mass fraction was controlled as ∼ 3%, and the binder reached the satisfactory strengths of 3.87, 24.47, 31.43, and 41.78 MPa at 1, 3, 7, and 28 d, respectively.

Investigation on effect of colloidal nano-silica on the strength and durability characteristics of red mud blended Portland cement paste through tortuosity

A novel binder system for cement-based composites depending upon the strength and durability characteristics is introduced in this study. The possibility of calcined red mud cement pastes with and without colloidal nano-silica (CNS) over Ordinary Portland Cement paste (OPC) at three W/B ratios (0.3, 0.4, 0.5) is evaluated. The optimum percentage of cement replacement by red mud (15%) was selected from compressive strength values of different cement replacements (5%, 10%, 15%, and 20%). Colloidal nano-silica (CNS) was added at 0.5%, 1%, 1.5%, and 2 % to the selected red mud cement paste. Water absorption, sorptivity, resistance to sulfate attack, and resistance to acid attack tests were conducted for optimum red mud cement paste with and without CNS. The experimental results are explained based on tortuosity with empirical formulas and mathematical models of pore network distribution. The tortuosity is directly proportional to the inter-connectivity of the pores. The mixes with 15% calcined red mud and 1.5% CNS replacement performed better strength and durability at all W/B ratios. The mix (R15NS1.5) with minimum tortuosity value results in the higher overall performance of the paste. The mixes with a 0.3 W/B ratio give high-performance cement paste compared to higher W/B ratios.

Loading-rate-dependent effects of colloidal nanosilica on the mechanical properties of cement composites

Colloidal nanosilica (CNS) has shown great potential in the fabrication of high-performance cement composites by improving their quasi-static mechanical properties. However, the effects of CNS under higher strain rates (i.e. dynamic loads) have been seldom explored. In this study, we thoroughly investigated the loading-rate-dependent effects of CNS on the mechanical performance of Portland cement paste. A Split Hopkinson Pressure Bar (SHPB) equipped with a high-speed camera was utilised to conduct dynamic testing under two different strain rates, namely ≈40 (1/s) and ≈120 (1/s), to analyse dynamic compressive strength, modulus of elasticity, failure strain, energy absorption, and fragment size distribution of the composites. Although CNS significantly improved the quasi-static mechanical properties, it had detrimental effects on the dynamic strength, stiffness, energy absorption, and fragmentation behaviour of the cement composites. These negative effects were attributed to the rapid flocculation of CNS upon mixing with the alkaline environment of cement, which led to the formation of a weak and porous hydration phase in the hardened cement paste, as corroborated by microscopy analysis. These findings demonstrate the importance of dynamic characterisations to fully understand the mechanical effects of nanomaterials because quasi-static investigations might not reveal their potential side effects.

Colloidal Nanosilica Effect on the Properties and Durability of Coir Reinforced Cement Brick

The impact of nanosilica on the properties and microstructure of cement-based products has lately attracted a lot of attention. The effects of colloidal nanosilica (CNS) at different concentrations on the hydration process and performance of cement-based composites reinforced with coconut coir were examined in this study. CNS was applied at concentrations of 0%, 2%, 4%, and 6% by weight of cement, respectively. The samples were evaluated in terms of flexural test, scanning electron microscopy (SEM), thermogravimetric analysis (TG-DTG), and X-ray Diffraction (XRD) after 7, 28, and 60 days of curing. Flexural strength improved by 13%, 11%, and 23% in the presence of CNS after 7, 28, and 60 days of hydration, respectively, as compared to the samples without CNS addition. The highest flexural strength was reported in samples containing 4% CNS. Beyond this, flexural strength decreases noticeably owing to the presence of too much nanosilica, which repressed the hydration process. The predominant causes of sample failure appear to be fiber breakage and fiber pull-out. In the sample containing 4% CNS, a dense structure was seen. The fibers had a strong bond with the matrix, showing that fiber/matrix bonding was improved. CNS served as a pozzolanic reaction promoter, converting CH to C-S-H, and a filler to improve cement microstructure. The CH content decreased when CNS was added, while the C-S-H gels increased.

Synergistic effect of colloidal nano and micro-silica on the microstructure and mechanical properties of mortar using full factorial design

The optimum interaction of colloidal nano-silica (CNS) and micro-silica (MS), which is a function of W/C and cement fineness, has an exclusive effect on the particular properties of cement composites, such as strengths, porosity, and microstructure. For sensitivity analysis, a full factorial design was applied wherein two water-to-binder (W/B) ratios were applied inconstant workability, and four levels of CNS and MS were produced and tested at different ages through many specimens.The results show that the synergistic effect of CNS and MS leads to higher performance of mechanical strength and porosity at all ages of curing when compared with their individual use. Using silica particles more than optimum values leads to inverse behavior in strength while the porosity continues to improve. Wider particle size distribution in ternary mixtures creates cement composite more dense and homogeneous, which was also confirmed by microstructure tests (MIP and SEM). Besides, according to XRD and MIP tests, the further production calcium silicate hydrate (C-S-H) gel is believed to be the reason for this improvement. Sensitivity analysis and analysis of variance also showed that the contribution of CNS to improving strength is greater than that of MS, while MS is more effective in decreasing porosity.

Effect of colloidal nanosilica as an admixture on chloride ion diffusion of Portland cement–fly ash mortars

The properties of the ordinary Portland cement (OPC) mortar having a water–cement (w/c) proportion of 0.450 and cement/sand ratio of 1:2 are altered by replacing cement with 25% fly ash and adding 2% colloidal nanosilica separately and in a combined form. The changes were studied experimentally. Cured specimens at different ages were subjected to compressive strength test, split tensile test, and durability tests such as sorptivity, water absorption, and chloride penetration. The impact of the addition of colloidal nanosilica on the permeability of the mortar matrix, estimated by the coefficient of absorptivity, was computed by performing a water absorption test for 60 min. It was observed that in the initial curing regime, fly ash expansion causes a decrease in strength and an increase in water permeability. The addition of 2% colloidal nanosilica proves to be advantageous in the hardened OPC and fly ash mortar as it increases the materials characteristic strength by conferring it a dense microstructure. Nanosilica in the cement matrix with and without fly ash assists the rapid growth of hydrated products by creating additional nucleation sites and improving the durability properties of the material as anodic polarization decreases under impressed voltage. The microstructure was analyzed by SEM and found to have the refinement of a pore structure and densification of binding gels in the colloidal nanosilica -incorporated samples.

Micro Structure Properties of Parent Concrete with Nano Silica and Polypropylene Fibre in Recycled Aggregate

This paper involves the study made to investigare the effects of colloidal nano silica and their properties on concrete with a constant replacement of recycled aggregates at a level of 100%. Polypropylene fiber of 2% is added in all mixes to enhance tensile properties of concrete. In many cities there is a surge in construction and demolition wastes constitute the major portion of solid waste production in the world. The reuse of such wastes as a new construction material were used to reduce the huge amount of natural resources. Here, ordinary Portland cement is replaced by weight fraction of nano silica at replacement levels of 0%, 0.5%, 1%, 1.5%, and 2%. The colloidal nano silica act as a filler material which increase some of the mix properties, it also act as accelator to enhance pozzolonic action. The further presence of nano silica enhance the strength and properties of concrete up to 1.5% of replacement criteria, such as mechanical strength tests were conducted in concrete mixes. it has been concluded from scanning electron microscope (SEM) analysis that the denser matrix is formed at 1.5% of replacement of nano silica.

Sustainable self compacting hybrid fiber reinforced concrete using waste materials

The current study investigates the behavior of hybrid fiber reinforced self compacting concrete (HyFRSCC) with crimped steel fibers (CSF) and polypropylene fibers (PPF) along with class F type fly ash (FA) and colloidal nano silica (CNS). To ascertain the fresh properties of self compacting concrete, the maximum volume of fiber content is restricted. The L16 orthogonal array of Taguchi method is followed to avoid the huge amount of experiments. In comparison to the control mix, mechanical properties of concrete are increased due to the combined effect of FA, CNS, CSF, and PPF. Rapid chloride penetration test is conducted to study the durability aspect of hardened concrete. Non‐destructive tests like ultrasonic pulse velocity and rebound hammer tests are conducted for the characterization of the properties of concrete. Based on the present study, a combination of FA, CNS, CSF, and PPF is proposed for an optimal recommendation in producing a ready‐mix type of HyFRSCC.

Effects of colloidal nano-silica on fresh and hardened properties of self-compacting lightweight concrete

The aim of this study is to investigate the effects of different levels of colloidal nano-silica (CS) on fresh and hardened properties of self-compacting lightweight concrete (SCLC). For this purpose, two concrete series including 16 concrete mixes with two water to binder (w/b) ratios of 0.35 and 0.45 were considered. The percentage of CS that replaced cement were 0%, 1%, 3% and 5%. Also, mixtures containing 0% and 10% MS were considered. The fresh properties of SCLCs were observed in terms of slump flow diameter and time, J-ring diameter, V-funnel time and U-box tests. The hardened properties were determined through mechanical properties (compressive strength, splitting tensile strength, flexural strength) and non-destructive tests (electrical resistivity and ultrasonic pulse velocity). The results of this work indicate almost all SCLCs satisfied the requirements of EFNARC. The results of hardened properties indicate that combined addition of MS and CS in SCLC was better than adding just one of them. The higher mechanical properties were obtained by ternary mixes containing 10% MS and 3% CS at both w/b ratios of 0.35 and 0.45. Moreover, the improvement of electrical resistivity and ultrasonic pulse velocity in ternary mixes were better than the binary and control mixes.

Effect of colloidal nanosilica on early-age compressive strength of oil well cement stone at low temperature

The compressive strength of cement stone rises slowly when cementing marine shallow section at low temperature, resulting in increased drilling cost and risk. This paper presents results of experimental study that was conducted to investigate the effect of low temperature on early-age compressive strength of cement stone admixed with colloidal nanosilica. The compressive strength of cement stones was measured after aging at 4 °C for 1, 3, and 7 days respectively. The hydration products of different aging cement stone were analyzed by X-ray diffraction and Fourier Transform infrared spectroscopy, and the microstructures were observed by scanning electron microscopy. In addition, the hydration exotherm of colloidal nanosilica modified cement slurry during hydration process was tested at 20 °C. The results indicated that the compressive strength of cement stone significantly improved by colloidal nanosilica. Interestingly, colloidal nanosilica retarded the initial hydration, and then promote the hydration process afterward. The mechanism of colloidal nanosilica to improve the compressive strength of cement stone was that colloidal nanosilica consumed calcium hydroxide to produce additional calcium silicate hydrate, filling large pores and cracks inside cement stone. More importantly, nanosilica particles provided nucleation sites of cement hydration and modified the internal structure of the hardened stone. The improvement of early-age compressive strength of oil well cement stone is beneficial to saving costs and reducing risk.

Modification effects of nanosilica on the interfacial transition zone in concrete: A multiscale approach

The effects of colloidal nanosilica on the interfacial transition zone (ITZ) in concrete at three days are studied. Mechanical properties are investigated at macro-scale, followed by nanoindentation characterization at micro-scale. A top-down and a bottom-up modelling are carried out, respectively, at macro- and micro-scales. Macro-mechanical results show that nanosilica addition is especially beneficial for the improvement of ITZ performance. Estimates from statistical nanoindentation provide evidence, suggesting that the hydration acceleration effect of nanosilica dominates in the modification of ITZ in an early age. It is revealed by modelling at both scale levels that the ratio of the Young's modulus of ITZ to that of bulk paste increases from around 50%–80% if nanosilica is incorporated. This work further confirms that a substantial improvement on ITZ can be obtained by ultra-fine nanosilica modification.

Effect of Colloidal Nano Silica as a Viscosity Modifying Agent in Self Compacting Concrete with High Volume POFA

This paper presents effects of Colloidal Nano Silica (CNS) as a Viscous Modifying Agent (VMA) on fresh properties of self-compacting concrete (SCC) containing high volume ground Palm Oil Fuel Ash (POFA). Accordingly, fresh properties of the SCC were tested using slump flow, J ring, L-box, and sieve stability test. To monitor the viscous behaviour of the fresh SCC with CNS, fillingability and passingability parameters were maintained within a desirable performance criterion whilst segregation, cohesiveness, and superplasticizer demand were the variables. All the mixtures were designed with the water/binder ratio of 0.45 and a total binder content of 500 kg/m3. The results revealed that the inclusion of CNS decreased the segregation and augmented the cohesion in all mixes.

Effect of Colloidal Nano-Silica on the Mechanical and Durability Performances of Mortar

s. The mechanical and durability properties of cement mortars with colloidal nanosilica (CNS) were investigated experimentally. Reference mortar with a low water-to-cement ratio of 0.30 was used in this study. The influence of CNS was evaluated by adding 0.5, 1.0, 1.5 and 2.0% of CNS by weight of cement. CNS was first stirred in the mixing water for 2 minutes before added to cement and sand. Superplasticizer was used to maintain the same flowability. Results showed that the compressive strength consistently increases with higher dosage of CNS at all the curing ages, due to both hydration acceleration and pozzolanic reaction. With the increase in CNS, the migration coefficient and water sorptivity consistently decreased; with 2% of CNS, the migration coefficient and water sorptivity were reduced by 45% and 30% respectively in comparison with the reference mortar. The improved durability could be explained by the reduction and refinement in the porosity, which can be attributed to nanofiller effect and pozzolanic reaction of nanosilica. Furthermore, the addition of CNS could reduce the drying shrinkage by densifying the microstructure in the cement paste, which has not been reported previously.

Effect of Nanosilica on Rheology, Fresh Properties, and Strength of Cement-Based Grouts

AbstractThe effect of colloidal nanosilica on the fresh and rheological parameters, plastic shrinkage, heat of hydration, and compressive strength of cement-based grouts is investigated in this paper. The fresh and rheological properties were evaluated by the minislump flow, Marsh cone flow time, Lombardi plate cohesion meter, yield value, and plastic viscosity. The key parameters investigated were the dosages of nanosilica and superplasticizer and temperature of mixing water. Statistical models and isoresponse curves were developed to capture the significant trends. The dosage of nanosilica had a significant effect on the results. The increase in the dosage of nanosilica led to increasing the values of flow time, plate cohesion meter, yield stress, plastic viscosity, heat of hydration at 1 day and 3 days, and compressive strength at 1 day, while reducing the minislump, plastic shrinkage up 24 h, and compressive strength at 3, 7, and 28 days. Conversely, the increase in the dosage of superplasticizer led ...

Effects of colloidal nanosilica on rheological and mechanical properties of fly ash–cement mortar

The present study is aimed at investigating the combined effects of colloidal nanosilica (CNS) and fly ash on the properties of cement-based materials. The fresh and hardened properties of mixtures with CNS of 10 nm size and two Class F fly ashes were evaluated. Results revealed that CNS accelerates the setting of fly ash–cement systems by accelerating cement hydration, while fly ash can offset the reduction in fluidity caused by CNS. The early-age strength gain (before 7 d) of fly ash–cement systems was improved by CNS. However, the strength gain of mixtures with CNS diminished at later ages (after 28 d), where strength was eventually comparable to or exceeded by mixtures without CNS. Results showed that lack of Ca(OH)2, which results from the high pozzolanic reactivity of CNS at early ages, and the hydration hindrance effect of CNS on cement at later ages can be the critical reasons.

Effect of colloidal nano-silica on the mechanical and physical behaviour of waste-glass cement mortar

This paper presents a laboratory study of the properties of colloidal nano-silica (CS)/waste glass cement composites. The microstructure, alkali–silica reaction (ASR), and the mechanical properties of cement mortars containing waste glass powder (WG) as a cement replacement with and without CS are investigated and compared with plain mortar. In addition, the hydration of cement compounds was followed by differential thermal analysis (DTA), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The results show that incorporation of WG has a positive effect on the mechanical properties of cement mortars especially when CS is presented. In addition, the DTA/TGA results and XRD analysis show a reduction in the calcium hydroxide (CH) content in mortars with both WG and a hybrid combination of WG and CS. This confirms the improvement of mechanical properties and the occurrence of the pozzolanic reaction after 28 days of hydration.

Effects of Colloidal Nanosilica on the Rheological Properties of Epoxy Resins Filled with Organoclay

The rheological properties of epoxy resins filled with organoclay and colloidal nanosilica were investigated by employing a parallel plate rheometer in flow mode at 25 degrees C. Shear thickening and shear thinning behaviors were observed in the epoxy resins filled with a mixture of organoclay and colloidal nanosilica. Minima were observed in the relaxation time of the systems consisting of epoxy resins filled with organoclay and colloidal silica as the content of colloidal nanosilica was increased. It seems that the colloidal nanosilica increased the mobility of the filled epoxy resins and reduced the interactions between the silicate layers in the systems.