Microsilica Addition Research Articles

Development of high strength one-part geopolymer mortar using sodium metasilicate

In this study, the solid activator – the synthetic sodium metasilicate pentahydrate – was compared against water and a hybrid sodium silicate and sodium hydroxide activator solution. It was found that the solid activator outperformed the liquid activator as a part of water remained chemically bound to the undissolved particles, thus reducing the apparent water to binder ratio. Contrary to the liquid activator, the increase in activator content past a certain limit did not correspond to improvement in strength. Instead, the compressive strength reduced and the risk of efflorescence increased significantly. Scanning electron microscopy (SEM) analysis showed that the denser reaction products took up less volume and formed a shell as the remaining metasilicate particles gradually dissolved under moisture ingression. This would eventually develop into a void, and cause strength- and durability-related issues. Additionally, fly ash content, microsilica addition, particle size of the activator, binder content, water to binder content and curing condition also played an important role in the hardening and pore refinement of the mixes. The one-part synthesis method could improve the safety and efficiency in geopolymer production.

Influence of Addition of Micro Silica on Strength Properties of Basalt Fiber Reinforced Multi Blended Concrete

In recent years, the development of multi blended mix concrete has gained attention due to its multiple advantages and environmental friendliness. This paper has attempted to examine mechanical properties of Multi blended concrete of M30 grade made with micro silica and basalt fibers. To reduce the deleterious effects of the production of cement on the environment, concrete is being developed by substituting admixtures like GGBS and Fly Ash in place of cement. Multi blended concrete developed with Fly ash and GGBS showed depletion in the mechanical properties. Micro silica & Basalt fibers were added to this mix additionally to overcome this deficiency. Initially four series of mixes of multi blended concrete were developed with a composition of Fly ash 20% and GGBS 30%, 40%, 50% & 60% as replacement of cement. For better performance, micro silica at 5% by weight of cement and Basalt fibers at 0.2% by volume of concrete were added. The mechanical properties such as Split tensile & Compressive strengths were studied at the age of 7 & 28 days. The results showed that M30 grade multi blended concrete can be achieved with 30% GGBS, 20% fly ash, 5% micro silica, 0.2% basalt fibers.

NOx degradation by photocatalytic mortars: The underlying role of the CH and C-S-H carbonation

This study aims to understand the impact of carbonation mechanism of C-S-H and CH in photocatalytic mortars on NOx removal efficiency. Changes in surface chemistry and microstructure induced by the carbonation of portlandite and C-S-H (AFm/AFt) were correlated with the photocatalytic efficiency of the mortars doped with three types of titania-based photocatalysts. Furthermore, the influence of cementitious matrix on the photocatalytic selectivity was evaluated by studying the capacity of hydration/carbonation products to adsorb NO2. The study revealed that in terms of both photocatalytic efficiency and selectivity, mortars with microsilica addition exhibit superior properties over the pure cement-based mortars upon carbonation. Carbonation of C-S-H (AFm/AFt) gel results in the formation of capillary pores between10–50 nm, which outbalances the shielding effects of carbonates formed, leading to the enhanced photocatalytic properties. Moreover, C-S-H gel maintains its high NO2 adsorption capacity even after carbonation, resulting in the high selectivity of the photocatalysis.

The Effect of Homogenization Procedure on Mechanical Properties of High-Performance Concrete with Partial Replacement of Cement by Supplementary Cementitious Materials

High-performance concrete is a very specific type of concrete. Its production is sensitive to both the quality of compounds used and the order of addition of particular compounds during the homogenization process. The mechanical properties were observed for four dosing procedures of each of the three tested concrete mixtures. The four dosing procedures were identical for the three mixes. The three mixes varied only in the type of supplementary cementitious material used and in water content. The water content difference was caused by variable k-value of particular additives. The water-to-binder ratio was kept constant for all the concretes. The additives used were metakaolin, fly ash and microsilica. The comparison of particular dosing procedures was carried out on the values of basic mechanical properties of concrete. The paper compares compressive strength and depth of penetration of water under pressure. Besides the comparsion of macro-mechanical properties, the effect of microsilica and fly ash additives on micro-mechanical properties was observed with the use of scanning electron microscopy (SEM) and nanoindentation data analysis. Nanoindentation was used to determine the thickness and strength of interfacial transition zone (ITZ) for different sequence of addition of cement, additive and aggregate. The thickness obtained by nanoindentation was further investigated by SEM EDS line scanning.

Hydration mechanism and sintering characteristics of hydratable alumina with microsilica addition

Abstract Hydratable alumina is potential for the application in refractory industry as one of Ca-free binders, but it is greatly limited because of the excess hydration of rho-alumina (ρ-Al2O3). In this study, hydration mechanism and sintering characteristics of hydratable alumina with different microsilica addition are researched, via the rheological, hydration, and morphological characteristics of ρ-Al2O3–SiO2–H2O system during aging are analyzed using various techniques. Boehmite (AlOOH) initially appears and increases in content after 1 h aging at the setting temperature of 30 °C and relative humidity of 80%. As the addition of microsilica increases from 0 wt% to 8 wt%, the SiO2 coating combines with the boehmite gel and efficiently suppresses the hydration reaction, resulting in decrease of relative hydrated densities from 5.42% to 4.27% and increase of zeta potential from −10.1 mV to −21.3 mV. Further, the thus-formed SiO2-AlOOH gels cover the surface of hydratable alumina particles, connect with each other, and get distributed homogeneously around hydratable alumina particles to harden, thus inhibiting the further hydration. This is reflected by the high-temperature X-ray diffraction and the final sintering microstructures. Overall, these results indicate that the 6 wt% addition of microsilica makes hydratable alumina promising for application as a kind of controlled binders.

دراسة تأثير المواد النانوية على الخواص الميكانيكية لمواد مصفوفة البوليمر المركبة

في الكثير من التطبيقات الصناعية ، تلعب المواد المركبة دورًا أساسيًا. يهدف تصنيع المواد المركبة الجديدة إلى تحسين قابلية تطبيق المواد. في هذا العمل تم دراسة تأثير نوع حشو النانو السيليكا ومقارنة هذا التأثير مع تأثير حشوات السيليكا الدقيقة على الخواص الميكانيكية للبوليستر. لهذا الغرض ، تم استخدام الاختبارات الميكانيكية. كانت إضافة النانو سيليكا والسيليكا الدقيقة بنسب مختلفة 1٪ و 3٪ و 5٪ ، ويرجع ذلك إلى حقيقة أن البوليستر هو أحد مصفوفة البوليمر التي تستخدم بشكل متكرر مع تقوية الألياف لتطبيقات معقدة من المركبات بسبب مقاومتها. للتآكل ، والتكلفة المنخفضة ، والتعامل السلس ، وقدرته على منع اندلاع اللهب.

Dependencies between Cracking Patterns and the Physico-Mechanical Properties of Microsilica Modified Cement Matrix

The article presents and evaluates the dependencies that occur between the parameters describing the geometry of cracking patterns on the sample‘s surface and the selected physico-mechanical properties of cement pastes with the addition of microsilica. The stereological parameters obtained with the use of image analysis were applied to the quantitative description of cracking patterns; also the compressive and tensile strength as well as the apparent density were examined. Cracks analyzed in the surface were caused by loading the samples with an elevated temperature. The relationships were calculated using the least squares method, and the quality of the fit of the model curves to the experimental data was evaluated on the basis of the diagnostic statistics. The results obtained indicated the existence of very strong relations between the geometry of cracking patterns and selected material features of the cement matrix. The analysis carried out is also of a great practical importance as it can help in assessing the degree of degradation of a cement structure exposed to elevated temperatures.

Understanding the need for pre-injection from permeability measurements: What is the connection?

Pre-grouting ahead of tunnels has three main functions: to control water inflow into the tunnel, to limit groundwater drawdown above the tunnel, and to make tunnelling progress more predictable since rock mass quality is effectively improved. It helps to avoid settlement damage caused by consolidation of clay deposits beneath built-up areas, since towns tend to be built where terrain is more flat, due to the clay deposits. There are so many instances of settlement damage that the profession needs to take note of the need for high-pressure pre-grouting, to use micro-cements and micro-silica additives. The use of high-pressure injection may cause joint jacking, but this is local in extent when the rapid pressure decay away from an injection hole is understood. This effect is variable and depends on the geometrical parameters of the joints. This pressure-decay advantage must not be violated by maintaining high pressure when grout flow from the injection hole has ceased. The latter can cause damage to the grouting already achieved. Simplified methods of estimating mean hydraulic apertures (e) from Lugeon testing are described, and from more sophisticated three-dimensional (3D) permeability measurement. The estimation of the larger mean physical joint apertures (E) is based on the joint roughness coefficient (JRC). Comparison is then made with the empirical aperture-particle size criterion E > 4d95, where d95 represents almost the largest cement particle size. Depending on joint set orientations and on the available micro-cements, the decision must be made of which range of pre-injection pressure should be aimed for, using successive reductions of the water-cement ratio w/c. More simple estimation of permeability, also with depth dependence, can be made with the empirical link between a modified rock mass quality Q and permeability, which is termed QH2O. The value of this parameter can be based on core-logging or in-tunnel face logging. The 3D before-and-after-grouting permeability measurements have been used to justify the quantification of rock mass quality Q-parameter improvement, and the consequent increases in expected P-wave velocity and deformation modulus, for application in dam foundation treatment and its monitoring.

Effect of micro silica and aggregate size on cracking of self-compacting concrete

In the evaluation of long-term serviceability leading to prevention of damage of self-compacting concrete (SCC) structures, a thorough understanding on fracture parameters and cracking performance from initial stage to hardened stage is important. This paper reports the effect of coarse aggregate size and micro silica addition on fracture characteristics and ductility of SCC. Experiments were performed by conducting three-point bending tests on notched beams as per recommendations by Rilem standards. For all mixes, the parameters are analysed by the size-effect method. The tests proved that an increase in the size of the coarse aggregates can increase the fracture energy and ductility due to changing fractal dimensions and the fracture process zone length. A 10% addition of micro silica showed better fracture properties. Equations for assessing the fracture energy and length of the fracture process zone using a statistical approach were then developed.

Experimental Study on the Use of Granite as Fine Aggregate in Very-High-Strength Concrete

The aim of the study is to assess the usefulness of using granite aggregate to make very-high-strength concrete. The paper presents a comparative analysis of the results that are obtained for three types of concrete mixtures. The main components of the analysed concretes are sand or granite aggregates and cement CEM I 52,5 with the addition of microsilica and fly ash. The first, basic concrete mixture is made using sand as aggregate. The main assumption for the basic concrete mixture is to obtain a compressive strength of not lower than 100 MPa in normal conditions of curing in water. Furthermore, using the aggregate fractions up to 2 mm and the semi-liquid consistency (i.e. ≥S3) of the concrete mixture are assumed. The second concrete mixture contains granite aggregate added in the same proportion as sand in the basic mixture. While in the third concrete mixture, the granite aggregate is used taking into account density factor. Laboratory tests are carried out in range of compressive and flexural strength of concrete. Furthermore, the investigations of the consistency of concrete mixtures and the water absorption by the hardened concrete are presented in the paper. Comparative analysis of the obtained results indicates that the exchange of sand to granite aggregate improves the compressive and flexural strength of concrete. Compressive strength of concrete based on granite aggregate is 10% higher than that of concrete based on sand. The test results indicate that both concrete made of sand and concrete made of granite aggregate can be qualified as very-high-strength.

Influence of Micro and Nanosilica on the Frost–Heave Process

Frost-heave of soils is an important problem in engineering practice. Thus, it became necessary to find an adequate method that would reduce the negative effect of this phenomenon on building structures. The paper presents the preliminary tests results of microsilica (MS) and nanosilica (NS) influence on the water freezing process in frost-susceptible soils. The selection of stabilising additives also allowed for the analysis of changes that result from their transition from micro to nanoscale. For the purposes of the experiment a test stand was constructed, that enables to analyse six samples at the same time, at inflow of water from the bottom and freezing direction from the top. The use of linear potentiometer displacement sensors allowed to measure the increase in the height of samples automatically. Additionally, the measurement stand was equipped with digital semiconductor temperature sensors, so temperature could be measured at various heights of the samples. Moreover, an array of electrodes was applied to measure the electrical conductivity of soil at various levels of samples, which enabled the analysis of changes that occur in freezing soil. The tests were conducted according to the BS 812-124:1989 standard, in three variants: soil, soil + 5% MS, soil + 5% NS. The obtained results demonstrated that the addition of microsilica reduces the occurrence of ice lenses, which in turn significantly decreases the growth in sample height. However, the addition of nanosilica completely stops the frost-heave process. Ice lens is not created, only a frost line is noticeable. Analysing the distribution of temperatures at different heights, it was noted that stabilised samples are characterised by higher temperature in comparison to the soil without additives. This means that the analysed stabilisers reduce the degree of freezing of the soil mixture. The highest temperatures were noted in samples stabilised with nanosilica. Conductivity tests also demonstrated that the smallest changes occurred in samples stabilised with nanosilica. This results from the fact that ice lenses did not occur in such samples. In order to analyse the obtained results and their interpretation thoroughly, it is necessary to perform a detailed analysis of the microstructure both of soil and of soil with stabilising additives.

The improvement of mechanical, physical and durability characteristics of volcanic tuff based geopolymer concrete by using nano silica, micro silica and Styrene-Butadiene Latex additives at different ratios

This study aims to the improvement of volcanic tuff-based geopolymer concrete (GPC) with the addition of nano silica (NS), micro silica (MS) and Styrene-Butadiene Latex (SBL) at the different ratios. For this purpose, incorporating of volcanic tuff with NS (1, 2, 3%), MS (1, 3, 5%) and SBL (5, 10, 15%) was provided. GPC samples were produced with two different activation method (Na2SiO3 + NaOH and sole NaOH). 28-day compressive strength, freeze-thaw (FT) resistance, microstructure, water absorption, density, bulk density and apparent porosity values of volcanic tuff-based GPC samples were investigated. The results indicated that the compressive strength of NaOH-activated samples was much higher than similar ones activated with Na2SiO3 + NaOH. In both activation methods, the optimum NS and SBL ratios were determined as 2% and 5%, respectively. Also, the optimum additive of MS ratio was determined 5% and 3% for Na2SiO3 + NaOH and sole NaOH-activated samples, respectively. As well as the highest compressive strength losses as a result of 300 FT cycles were observed in pure samples for both activation methods, Na2SiO3 + NaOH-activated samples exhibited better resistance to FT effect than similar ones activated with sole NaOH.

Influence of Silica Fume Addition on Selected Properties of Fine-Grained Concrete

The article presents the results of laboratory tests of selected mechanical and physical properties of fine-grained concrete. The tests were carried out on samples with varying degrees of microsilica addition. The consistency class, shrinkage, compressive and bending strength, water resistance and frost resistance were determined for the designed concrete mixtures and made samples.

Microsilica in Sodium Silicate Bonded Sands

This paper investigates the microsilica addition value in the improvement of the sand molds and cores properties made with sodium silicate binders. There are experiments confirming the importance of the better sand mixtures mobility in the strengthening of these molds and cores. The paper explains the difference between microsilica and nanosilica in their interaction with alkaline silicate solutions and shows how the products of this interaction affect the properties of the sand mixtures. The results presented in the paper show the role of microsilica in curing sodium silicate bonded sands and demonstrate more possibilities to spread its positive complex effect on the sand molds and cores cured chemically, without heat. Conducted experiments with these sands proved the benefits of applying microsilica as a sand additive for increasing density and strength of the molds and cores, for easing their shakeout by lowering silicate level in the binder system. It is shown that the microsilica presence in the powder component allows using a hydrous sodium silicate powder also as a part of this component to replace a liquid sodium silicate in the two-component silicate binder system as well as creating pourable dry mixtures of silica sand and all solid additives of the binder system.

Investigation of Mechanical Properties of Self Compacting Polymeric Concrete with Backpropagation Network

Acrylic polymer that is highly stable against chemicals and is a good choice when concrete is subject to chemical attack. In this study, self-compacting concrete (SCC) made using acrylic polymer, nanosilica and microsilica has been investigated. The results of experimental testing showed that the addition of microsilica and acrylic polymer decreased the tensile, compressive and bending strength of the concrete. The addition of nanosilica and an increase in polymer content increased the bending strength of concrete and decreased the tensile and compressive strengths. Because, in the laboratory, the number of samples were limited and the amount of variation was small, comprehensive results cannot be achieved. With the help of neural networks, estimating any amount within the range of the input data is possible. In this paper, in addition to the experimental results, a backpropagation neural network (BNN) was used to simulate the testing on the strength of self-compacting polymeric concrete. The results showed that the use of the normalized mean squared error, resilient backpropagation training, tangent-sigmoid and log sigmoid transfer functions and five neurons in each hidden layers in a two-layer BNN produced good results with a regression value of 0.95 and error of 0.17.

Combined usage of micro-silica and nano-silica in concrete: SP demand, cementing efficiencies and synergistic effect

It is well known that the addition of micro-silica (MS) can improve the strength and durability of concrete and the addition of nano-silica (NS) can also improve certain properties of concrete. However, systematic research is still needed to exploit the benefits of combined usage of MS and NS, and more specifically, to evaluate their cementing efficiencies and synergistic effect. In this study, an experimental program was launched to investigate the combined effects of MS and NS on the compressive behaviour of concrete. Concrete mixes with varying water/cementitious materials (W/CM) ratio, MS content and NS content but similar workability were produced for testing. It was found that NS has much higher superplasticizer (SP) demand and cementing efficiency than MS. Nevertheless, at the same strength, the SP demand of (MS + NS) is not higher than that of pure cement. More importantly, the combined usage of MS and NS offers certain synergistic effect, as evaluated by a new formula proposed in this study.

Fabrication of calcium hexaluminate‐based porous ceramic with microsilica addition

AbstractCalcium hexaluminate (CA6)‐based porous ceramic was prepared with α‐alumina powders and nanometer‐sized calcium carbonate using a direct foaming technique with the addition of calcium aluminate cement and microsilica. The microsilica leads to the acceleration of CA6 formation. Moreover, the shrinkage, densification, and elastic modulus at room temperature were enhanced with increasing microsilica content. But the hot elastic modulus showed obvious reduction between 1100°C and 1200°C if the microsilica content was over 0.5 wt%. Furthermore, α‐Al2O3 appeared in the specimens with and without microsilica after treatment at 1550°C, and the proportion of CA6 grains having a high aspect ratio increased after microsilica addition.

The effect of micro- and nanosilica on the soil permeability coefficient under cyclic freezing and thawing conditions

The paper presents the analysis of the permeability coefficient of frost-susceptible soil with microsilica (MS) and nanosilica (NS) addition. Tests were performed in a triaxial apparatus in three variants: on pure soil samples, on soil samples with a 5% MS and on soil samples with a 5% NS addition. Because of the frost-susceptible properties of analysed soil, the permeability coefficient was determined on unfrozen samples and on samples after 10 cycles of freezing and thawing. The preliminary test results demonstrated that both microsilica and nanosilica have beneficial properties related to subsoil sealing. These properties are considerably stronger for nanosilica. Also, in all cases, the permeability coefficient increased after 10 cycles of freezing and thawing, but the change trend remained the same. Nanosilica shows particularly good sealing properties in frost-susceptible soils. This confirms that it may be applied as a separate additive, which is not commonly used in engineering practice. Nano particles are usually used to extend the scope of micro additives’ influence. In order to recognise the beneficial influence of analysed additives on soil permeability, the recognition of the changes in microstructure is necessary.

Effect of microsilica addition on the properties of colloidal silica bonded bauxite-andalusite based castables

Colloidal silica bonded bauxite-andalusite based castables were prepared using homogenized bauxite and andalusite as aggregates, andalusite fines, corundum fines, ultrafine Al2O3 as matrixes and colloidal silica as binders. Effects of microsilica addition on the green strength, physical properties, hot strength and thermal shock resistance of castables were investigated. Moreover, phase composition and morphological evolution of specimens were characterized by XRD and SEM analysis. Green strength after demoulding, cold strength and hot strength as well as thermal shock resistance of the castables are enhanced with microsilica addition, which attribute to generating more chemical bond (–Si–O–Si–) after demoulding and heating at intermediate temperature (up to 1100°C), and creating a stronger mullite bonding at higher temperature (1400°C) compare to the specimens without microsilica.

Developing design methods of concrete mix with microsilica additives for road construction

Based on the laboratory test results, regression equations having standard cone and concrete strength, to determine the available amount of cement, water and microsilica were obtained. The joint solution of these equations allowed the researchers to develop the algorithm of designing heavy concrete compositions with microsilica additives for road construction.