Colloidal Nanosilica Research Articles

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.

Effect of GGBS, Metakaolin and Colloidal Nano-Silica on Mechanical Properties of Concrete

Abstract: Concrete is the most common used material for construction &their design consumes almost the total cement production in the world. The use of large quantities of cement produces increasing CO2 emission and as a consequence the greenhouse effect. A method to reduce the cement content in the concrete mixes is the use of GGBS, Metakaolin Nano-Silica. This project aims to present the state of GGBS, Metakaolin& Nano-Silica's effect on the workability and mechanical properties of concrete and to find out the economy of the experiment as compared to convential concrete. Concrete has occupied an important place in construction industry in the past few decades and it is used widely in all types of constructions ranging from small buildings to large infrastructural dams or reservoirs.. Keywords: GGBFS, Mechanical Properties, Workability, Economy

Investigation on Mechanical Durability Properties of High‐Performance Concrete with Nanosilica and Copper Slag

Mineral admixtures are frequently utilized as cement substitution materials in high‐performance concrete (HPC), and so many studies have explored the influence of mineral admixtures on the rheological behavior of HPC. Investigations were done to examine the impact of nanosilica less than 100 nm on HPC by substituting copper slag at a fixed substitution of forty percent for fine aggregate. Concrete samples were cast by substituting cement with nanosilica at (0.5, 1, 1.5, 2, 2.5, and 3) percentages. Examinations on mechanical properties and durability were done on specimens. The above tests demonstrated an increase in water demand because of the increase in the nanosilica substitution percentage. Mechanical and durability properties were improved at a larger rate with the incorporation of nanosilica. The outcomes indicated that colloidal nanosilica is an effective material that enhances the microstructure and acts as a catalyst for pozzolanic activity. The incorporation of nanosilica improves the strength up to two percentage substitution level.

Impact of nano silica on the cementitious systems of built environment

In today’s scenario, most of the construction materials are man-made and are naturally sourced but have limitations, especially with regard to their impact on environment. Further, the conventional materials and technologies for construction are unsustainable and less durable with fast depletion of natural resources, pollution of environment and heavy economic cost. Silica Fumes or its more finer counterpart Nano silica, made from waste materials have excellent pozzolanic, pore filling and nucleating properties and proposes to be the most promising sustainable nanomaterial aiming the ultimate solution in built environmental applications.Work presented by many authors reveal that the Silica Fumes improve the performance of cement composites and concretes through micro-level contributions but Nano silica additions have brought in further improvements. This paper reports the effect of adding colloidal Nano Silica (NS) of 5–40 nm dia. sized particles & adding them to cement: sand ratio of 1:3 with a water-cement ratio of 0.4. Due to the continued hydration mechanism of cement particles, mechanical strength results of the cementitious composites were taken at all terms up to longer term of 365 Days. The optimized quantity of NS as found in cement composites is then added to fly ash-based cement composites for compressive strength testing at both shorter, standard & longer terms following Indian standard protocols. This paper aims to investigate and analyse the mechanical performance for both blended & ordinary cement and the corresponding microstructures of Nano silica additions in ordinary cement composites. Results reveal that the non-standard mortar strength and its rapid strength gaining are particularly in favour for fly ash PPC blended cement with Nano Silica additions.

Experimental studies of sustainable concrete modified with colloidal nanosilica and metakaolin

Experimental studies of sustainable concrete modified with colloidal nanosilica and metakaolin

Performance evaluation of sustainable recycled aggregate concrete with colloidal nano-silica

The use of recycled coarse aggregate (RCA) in concrete is a sustainable thing in the concrete industry. But during the recycling process of concrete waste for RCA, some mortar will be adhered to it and the coarse aggregate may have got fractured; if it was used in making the recycled aggregate concrete (RAC), it may produce inferior-quality RAC. To enhance its mechanical and microstructural characteristics of RAC, an admixture in the form of colloidal nano-silica (CNS) which are highly reactive in producing C-S-H gel with the hydrated cement and effectively fill the microvoids and crack in RAC and improves the interfacial transition zone (ITZ) was considered in the present experimental investigation with 100% replacement of natural coarse aggregate (NCA) with RCA and partially replacing the cement with CNS (0%, 1%, 2% and 4% by weight). The detailed analysis of the experimental results revealed that the replacement of cement with CNS in both the NAC and RAC mixes has enhanced the mechanical and microstructural characteristics; most notably, reduction in voids and improvement in the ITZ. The concrete mixes even with 100% RCA and partial replacement of cement with CNS satisfies the design requirements for its application in the construction industry.

Strength evaluation of soil stabilized with nano silica- cement mixes as road construction material

In pursuit of replacing the conventional GSB courses by stabilizing locally available soil and reconciling it for road constructions, an experimental investigation was undertaken by treating silty sand with colloidal nano silica in three different concentration grades of NS-20, NS-30 and NS-40. Each proportion was further treated with 2%, 4% and 6% of cement. Experiments were conducted to study the effect of nano silica on modified proctor compaction, CBR and UCS tests. XRD and SEM tests were conducted to discern the latent mechanisms to study the physico- chemical changes within the soil matrix. The results demonstrated that the increase in cement content with different grades of nano silica treated soil played an indispensable role in improving the mechanical properties of soil. Optimal results were obtained for soil treated with NS-40 and 6% cement. Soaked CBR values of soil mixes were substantially enhanced by 240.76%, 268.62% and 312.90% and 7-days UCS results were observed to be enhanced by 20.98%, 43.93% and 80.19% on addition of 2%, 4% and 6% cement in case of optimized soil mixes. XRD and SEM results postulated the evidences of the furtherance in cementitious activity within the soil matrix. The paper also discusses about Resilient Modulus parameters for optimized samples by cyclic triaxial tests under different cell pressures. Results demonstrated that nano silica-cement reinforced soil satisfied the criteria for chemically stabilized bound sub bases as per codal provisions.

Modification of recycled aggregate by spraying colloidal nano silica and silica fume

Modification of recycled aggregate by spraying colloidal nano silica and silica fume

Performance enhancement of silica fume blended mortars using bio-functionalized nano-silica

This work explores a naturally occurring bio-molecule, tannic acid (TA) to functionalize the colloidal nano-silica (NS) for better performance in the silica fume (SF) blended mortars. The functionalization process is achieved via mixing the colloidal NS with TA solution for 5 min. The introduction of well-dispersed nano-silica can improve the particle packing of silica fume blended mortars with better gradation. As a result, both mechanical properties and durability of produced mortars can be significantly enhanced. To this end, an experimental program was carried out to evaluate the effects of TA functionalization, including hydration kinetics, workability, setting time, compressive strength, pore structure, and nanomechanical properties. Testing results show that functionalizing with TA leads to up to 15% increase in the workability of silica fume blended mortars and more than 12% reduction of the porosity of pastes. These improvements are due to the filler effect of the nano-silica particles and higher packing density of hydration products induced by TA functionalization. As a result, the average elastic modulus and packing density of the major hydration product, calcium silicate hydrate (C-S-H) are increased by 8.15% and 2.68%, respectively, and the compressive strengths of the mortars at 28d is improved up to 34.97%.

Evaluating resistance of microsilica and colloidal nanosilica in Indian ordinary Portland cement mortar against combined chloride and sulfate attack

Evaluating resistance of microsilica and colloidal nanosilica in Indian ordinary Portland cement mortar against combined chloride and sulfate attack

Experimental studies on the development of a self-healing cementitious matrix for repair and retrofitting of concrete structures

PurposeSelf-healing concrete is a revolutionary building material that will generally reduce the maintenance cost of concrete constructions. Self-healing of cracks in concrete structure would contribute to a longer service life of the concrete and would make the material more durable and more sustainable. The cementitious mortar with/without incorporating encapsulates at different percentages of slag replacement with the cement mix improves autogenous healing at different ages. Therefore, this study’s aim is to develop a self-healing cementitious matrix for repair and retrofitting of concrete structures.Design/methodology/approachIn the present work, waste straw pipes are used as a capsule, filled with the solution of sodium hydroxide (NaOH), sodium silicate (Na2SiO3) and colloidal nano-silica as self-healing activators. An artificial micro-crack on the control and blended mortar specimens at different percentages of slag replacement with cement (with/without encapsulation) is developed by applying a compressive load of 50% of its ultimate load-carrying capacity. The mechanical strength and ultrasonic pulse velocity, water absorption and chloride ion penetration test are conducted on the concrete specimen before and after the healing period. Finally, the self-healing activity of mortar mixes with/without encapsulation is analysed at different ages.FindingsThe encapsulated mortar mix with 10% of slag content has better self-healing potential than all other mixes considering mechanical strength and durability. The enhancement of the self-healing potential of such mortar mix is mainly due to hydration of anhydrous slag on the crack surface and transformation of amorphous slag to the crystalline phase in presence of encapsulated fluid.Research limitations/implicationsThe self-healing activities of the slag-based cementitious composite are studied for a healing period of 90 days only. The strength and durability performance of the cracked specimen may be increased after a long healing period.Practical implicationsThe outcome of the work will help repair the cracks in the concrete structure and enhances the service life.Originality/valueThis study identifies the addition encapsulates with a self-healing activator fluid that can recover its strength after minor damage.

High-performance cement mortars-based composites with colloidal nano-silica: Synthesis, characterization and mechanical properties

In recent years, nanotechnology has found great application in the concrete and cement mortars industries. In this study, silica nanoparticles have been prepared in acidic solution via simple, low-cost, and efficient sol–gel methods. The effect of surfactant and calcination on the morphological properties of silica nanoparticles was investigated. The prepared silica nanoparticles are characterized via X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and dynamic light scattering (DLS) analysis. Prepared silica nanoparticles are introduced to cement mortars at different dosage and their effects on compressive and flexural strengths were studied. Results showed that 4% (%wt) have the highest improvement in cement mortars quality. The presence of 4% contents of silica nanoparticles in cement mortars increases the compressive strength by 10.54% in three days, 12.35% in one week, and 15.04% in 28 days. Flexural strengths are increased to 23.25% in three days, 9.45% in one week, and 18.40% in 28 days.

Influence of nano-silica on the microstructural and mechanical properties of high-performance concrete of containing EAF aggregate and processed quarry dust

The present study investigates nano-silica (NS) in ternary binder composite and the influence of the same on Electrical Arc Furnace (EAF) slag coarse aggregate-based various high-performance concrete (HPC) mixes. Processed Quarry Dust (PQD) was used as fine aggregate throughout the investigation to limit the consumption of natural river sand and make HPC more sustainable. Control HPC was designed using the Ordinary Portland Cement (OPC)- Ground Granulated Blast Furnace Slag (GGBS) binary binder and various replacement levels of natural crushed granite rock aggregate by EAF coarse aggregate. Additionally, the binary binder composite was added with colloidal nano-silica to achieve high strength HPC. A microstructure study was carried out on paste samples of OPC, OPC with GGBS, and OPC, GGBS with the inclusion of nano-silica. FESEM, EDX, XRD, FTIR, and TGA results showed that the addition of nano-silica has significantly enriched the microstructure characteristics of the binder system. The slump flow of HPC mixes decreased drastically with the inclusion of nano-silica and EAF aggregate. Mechanical properties viz., compressive strength, split tensile strength, flexural strength, and modulus of elasticity of HPC mixes containing EAF and nano-silica have exhibited superior results due to the synergetic effect of nano-silica as well as the more robust physical characteristics of EAF aggregate compared to natural crushed granite rock aggregate. The UPV values and water absorption tests have shown that nano-silica positively affects the binder composite system.

Effect of nano and micro SiO2 on brittleness and fracture parameters of self-compacting lightweight concrete

In the present study, 16 mix compositions with two different water to binder ratios of 0.35 and 0.45 were designed to assess the fracture behavior of self-compacting lightweight concrete (SCLC) mixes with micro and colloidal nano silica. To do so, 192 notched beam specimens of various sizes were cast. The contribution of 10% micro silica (MS), 1%, 3%, and 5% colloidal nano silica (CNS) were considered in forms of binary and ternary mixtures and then the results were compared with those of controlling specimens. In order to analyze the fracture behavior of mixes, type-II size effect law were used and all tests were conducted in accordance with RILEM recommendations. The results indicated that W/B ratio as well as the replacement of MS and CNS with cement could substantially affect the fracture behavior of SCLC mixes. For instance, the use of 10% MS in the absence of CNS has led to the increase of fracture energy by 9.8% and 16.4% for mixes with W/B ratios of 0.35 and 0.45, respectively, while at the same level of 10% MS replacement by cement, the replacement of 1%, 3%, and 5% CNS by cement, has improved the initial fracture energy of the W35 group of mixes by 11.38%, 16.58%, and 8%, respectively. This was 1.8%, 10.6%, and 4.6% for W45 group of mixes with 10% of MS. In addition, this research showed that the proposed model could conveniently predict the experimental results.

Experimental Investigation of Electrochemical Corrosion and Chloride Penetration of Concrete Incorporating Colloidal Nanosilica and Silica fume

Enhancement of durability and reduction of maintenance cost of concrete, with the implementation of various approaches, has always been a matter of concern to researchers. The integration of pozzolans as a substitute for cement into the concrete is one of the most desirable technique. Silica fume (SF) and colloidal nanosilica (CS) have received a great deal of interest from researchers with their significant performance in improving the durability of concrete. The synergistic role of the micro and nano-silica particles in improving the main characteristics of cemented materials needs to be investigated. This work aims to examine the utility of partial substitution of cement by SF and CS in binary and ternary blends in the improvement of the durability characteristics linked to resistance for electrochemical corrosion using electrical resistivity and half-cell potential analysis and chloride penetration trough rapid chloride penetration test. Furthermore, the effects of this silica mixture on the compressive strength of concrete under normal and aggressive environment have also been investigated. Based on the maximum compression strength of the concrete, the optimal cement substituent ratios have been obtained as 12% SF and 1.5% CS for binary blends. The optimal CS and SF combination mixing ratios has been obtained as 1.0% and 12% respectively for ternary blends. The ternary blends with substitution of cement by optimal percentage of CS and SF exhibited decreased rate for electrochemical corrosion. The strength and durability studies were found in consistence with the microstructural analysis signifying the beneficiary role of CS and SF in upgrading the performance of concrete.

Experimental study of the mechanism of grouting colloidal nano-silica in over-broken coal mass

Grouting is an important process for stability control of unfavourable geology. A multi-parameter grouting monitoring device was designed to monitor pump pressure, inlet density, outlet density, outlet electrical resistance and osmotic pressure. On the basis of multi-source information, this paper presents an experimental study of the process of grouting colloidal nano-silica into an over-broken coal mass, which was verified by percolation mechanics theory and numerical simulation simultaneously. The porosity and permeability of the injected sample were 15.34% and 5.45 mD. The results showed that the variation of pump pressure generally showed an obvious three-stage regularity. The time-dependent curves of outlet density and outlet resistance were consistent with that of pump pressure, whereas the curve of inlet density was opposite to that of pump pressure. The law of the dominant penetration mechanism was as follows: miscible displacement mechanism in the first stage (0–46 min), Darcy flow in the second stage (46–200 min) and filtration flow in the third stage. This research can guide grouting theory study and design in an over-broken rock mass.

Grouting of cohesionless soils by means of colloidal nanosilica

Colloidal nanosilica is an innovative grouting material, currently used in tunnelling applications for grouting fine cohesionless soils when environmental limits prevent the application of other solutions. Despite a large number of applications, knowledge of operational parameters for grouting such as gelling time and dynamic viscosity is very limited. Furthermore, the influence of the type of nanosilica (in terms of SiO2 concentration) and accelerators on the achievable mechanical performance of injected soils has never been investigated. In this work, a laboratory test campaign based on two commercial colloidal nanosilica and two accelerators was conducted. Once the operational parameters had been investigated, four different soils have been grouted and, after curing, mechanically tested. The results, in terms of gelling time and viscosity order of magnitude, are crucial for the correct functioning of a grouting. Furthermore, the results of the uniaxial compression tests, the indirect tensile tests and the direct shear tests have shed light on the potential of colloidal nanosilica and on the differences between the chemicals.

Treatment with nano-silica and bacteria to restore the reduced bond strength between concrete and repair mortar caused by aggressive removal techniques

Removal of degraded concrete during repair activities might have a detrimental impact on the bond strength between the concrete and the repair mortar. This research aims to improve the bonding strength in case aggressive removal techniques were used, by the singular and combined application of bacterially induced CaCO3 and colloidal nano-silica (CNS) treatments. Water jetting (WJ) and jackhammering (JH) were compared and the treatments were performed on the substrates prepared with the technique causing the lowest bonding. Pull-off test results on crushed stone concrete (CC) substrates showed that JH substrates possessed the lowest bond strength compared to WJ and unprepared substrates. To assure that reported results are reproducible, pull-off tests were also performed on another type of concrete, gravel concrete (GC). The results showed that in both cases JH-substrates achieved a lower bond strength than unprepared- and WJ-substrates. The reduced bond strength by JH was restored by the CNS treatment irrespective of the concrete composition. Regarding the biodeposition treatment, the spraying technique showed to be superior to the pouring technique. Microstructural analysis confirmed the survival of the bacteria and carbonate precipitation. Porosity of the prepared substrate surfaces was studied by capillary absorption, water absorption (including the gravity effect) and vacuum absorption tests. The reduction in the initial water uptake of CNS-treated samples was evidenced by the precipitation of the silica gel at the superficial layer of the substrate. The efficacy of Energy Dispersive X-Ray Analysis (EDX) to recognize the interlayer of layered composites with a monolithic structure was observed.

Properties of concrete with high volumes of unprocessed coarser fly ash and nanosilica

The limitation of fly ash as a cement substitute in concrete is often low due to its slow rate of strength development. The use of unprocessed coarser siliceous fly ash is also negligible. An attempt was made to produce a structural-grade concrete using a high volume of unprocessed coarser fly ash and colloidal nanosilica that was curable at ambient conditions. The fly ash content in the trial mixes varied from 50 to 70%. The temperature of fresh mixes during early age indicated that adding nanosilica accelerated the rate of hydration. Also, substantial improvements in early- and later-age compressive, split tensile and flexural strengths; modulus of elasticity; and stress–strain characteristics were observed for mixes with nanosilica. The compressive strength test results were corroborated with the inferences made from scanning electron microscopy and differential thermogravimetric analysis of the hardened cementitious pastes. The material cost of the mixes with nanosilica was found to be in a range similar to that of an ordinary Portland cement concrete, and the carbon dioxide equivalent emission of such concretes was 45–65% lower. It was concluded that with the addition of 3% colloidal nanosilica, it is possible to prepare a structural-grade concrete using unprocessed coarser siliceous fly ash that is curable at ambient conditions and has significantly improved early-age strength and also high later-age strength, while at the same time achieving sustainability and favourable cost benefits.

Investigation of different permeability properties of self‐healing cementitious composites under colloidal nano silica curing conditions

AbstractIn this study, the self‐healing behavior of engineered cemetitious composites (ECC) containing different types and quantities of fly ash (FA) under colloidal nano silica (CNS) curing conditions was investigated through the examination of their different permeability properties. FA in two different characters, Class F and Class C, were used in the preparation of the mixtures in high volumes (FA/portland cement = 1.2 and 2.2). Self‐healing capacities developed under CNS curing conditions were evaluated by changes in different permeability properties such as rapid chloride permeability test (RCPT) and electrical impedance measurement methods. In addition to these, the self‐healing effects of the cracked composites were supported by microstructure analysis with the help of SEM–EDX and XRD tests on the sections taken from the crack interface of the sample. The results have showed that the CNS curing condition helps improve the permeability properties of composites by quickly and effectively covering their micro pores and cracks. In addition, the results of the experiment have revealed the effects of the use of different types and quantities of FA on the self‐healing behavior of the ECC material. Finally, correlation analysis of ECC samples was applied according to the results obtained from EI and RCPT test methods and it was revealed that there was a negative significant relationship between test methods.