Condensed Silica Fume Research Articles

Addition of Ground Zeolite to Improve the Flowability and Cohesiveness of Mortar

Packing density if of cardinal importantce in the performance of cement-based materials. Theoretically, ground zeolite (GZ), a cementitious material that is finer than cement and coarser than condensed silica fume (CSF), is able to fill the voids between the cement particles in mortar for performance improvement without excessively high specific surface area. In order to evaluate the effects of GZ on flowability and cohesiveness, a total of 15 mortar mixes with different GZ contents and different cementitious materials/aggregate ratios at the same water/cementitious materials ratio were produced for flowability, cohesiveness and strength measurement. Results indicated that adding GZ as no more than 5% cement replacement would increase the flowability and strength, but further addition of GZ to more than 5% decreased the flowability, cohesiveness and strength. The experimental results are in general agreement with the findings from the literatures. Adding GZ tas no more than 5% cement replacement improve both the flowability and cohesiveness at equal-strength basis, further addition of GZ upon 5% improved the concurrent flowability and strength performance when the strength requirement is low, but impaired the concurrent cohesiveness and strength performance. It can be concluded that 5% is optimum GZ addition content in the viewpoint of flowability and cohesiveness performance of mortar.

Regression Anaylsis for the Experimental Study on the Pullout Strength of Steel Fiber Self- Compacting Concrete

This article describes experimental research of the interfacial adhesion of triple blended steel fibre self-compacting concrete (TBSFSCC) and it varies depending on the percentage of steel fibre. In self-compacting concrete, mineral admixtures such as condensed silica fume and flyash are utilised as supplementary cementitious materials (SCMs).the percentage of replacement of cement by condensed silica fume at 10 where as flyash at 20 respectively, to meet the SCC criteria stipulated by ACI. The embedment length of a steel bar with a diameter of 12mm was chosen to be 100mm in all of the standard specimens. Fe-415 steel rod is used in this research. The pull-out test in the universal testing machine is used to evaluate the bond strength of this triple blended Self-Compacting Concrete (TBSCC). Ordinary steel fibres are then added to the concrete volume at various percentages, such as 0.2, 0.4, 0.6, and 0.8. The bond strength, slip, and the method of failure of each rebar were all noted in the test results. The comparison of these results clearly shows that the percentage of steel fibre contributes to the TBSCC bond strength, and conclusions are generated.

Use of Particle Size Distribution Model to Produce High-Flowability Cementitious Composites

High packing density is desired for production of high-flowability cementitious composites. To achieve dense packing, various particle size distribution models have been proposed by researchers. In present study, with the use of two supplementary cementitious materials at different scale smaller than ordinary Portland cement (OPC), an ideal particle size distribution curve according to modified Andreasen’s formula has been produced. Analysis of particle size distribution showed that blending the cement with superfine cement (SFC) and/or condensed silica fume (CSF) would make the curve closer to the ideal curve, hinting that a better packing could be achieved. Packing densities of the cementitious materials were then directly obtained through a wet packing method, and results verified that cementitious materials mix blended with SFC and/or CSF own higher packing densities.

Effect of ambient curing periods on the mechanical properties of geopolymer concrete prepared with three mineral admixtures and glass fibers

Fly ash serves as the primary binder in geopolymer concrete (GPC), Several experiments have been performed using ground blast furnace slag (GGBS) as a fly ash additive in GPC and the results show that GGBS enrichment improves the mechanical properties. Existing experimental investigation employs a constant (optimum) percentage of condensed silica fume (CSF) along with GGBS as part replacement of fly ash in GPC of M40 grade. Glass fiber reinforcement was incorporated at percentages of 0.5,0.75 and 1.0 in the GPC composite. Laboratory specimens were prepared, and the mechanical properties were found at various curing periods ranging from 7 days to 60 days under ambient conditions. It is inferred that extended curing periods at ambient conditions have increased the mechanical strengths of GPC mixes. Glass fiber has contributed to strength increase, particularly in tension and flexure. Condensed silica fume has contributed towards more strength and workability of GPC.

Mechanical and Microstructural Studies of High Performance Concrete with Condensed Silica Fume

This article is an extended version of the conference paper “Influence of silica fume on mechanical and fracture properties of high performance concrete” published in Procedia Structural Integrity as a part of the Special Issue for the 3rd International Conference on Structural Integrity (ICSI 2019). Tests were carried out to evaluate the compressive strength, tensile splitting strength, modulus of elasticity, flexural strength, and fracture properties of high performance concretes (HPC) having different levels of condensed silica fume (CSF) replacements for cement. It was found that CSF replacement for cement by up to 25% may have a favorable effect on the mechanical properties. HPC containing CSF was characterized by quite large increases in compressive strength (up to 14%) and flexural strength (16%). However, the most significant improvements in mechanical properties were obtained for splitting tensile strength (26%) and fracture energy (30.5%). There were slight reductions up to 2% in the elastic modulus, flexural strength and fracture properties at the 25% level of CSF substitution for cement. Microstructural studies showed that the narrowest microcracks and the smallest pores in the interfacial transition zone (ITZ) between the paste and grains of aggregate occurred in the HPC having 10% CSF. In addition, a reduction of ITZ around the aggregate and the formation of more high-strength hydration products was observed in all CSF-added HPCs. The outcomes reported that CSF can successfully replace cement. It is suggested that the substitution should not exceed 20%.

Regression Analysis for the Bond Strength of Steel Fibre Self-compacting Concrete Based on the Experimental Studies

This article describes experimental research of the interfacial adhesion of triple blended steel fibred self-compacting concrete (TBSFSCC) and it varies depending on the percentage of steel fiber. In self-compacting concrete, mineral admixtures such as condensed silica fume and fly ash are utilized as supplementary cementitious materials (SCMs). Condensed silica fume can replace 10 percent of the cement and fly ash can replace 20 percent of the cement to fulfill ACI's SCC guidelines. The embedment length of a steel bar with a diameter of 12mm was chosen to be 100mm in all the standard specimens. Fe-415 steel rod is used in this research. The pull-out test in the universal testing machine is used to evaluate the bond strength of this triple blended Self-Compacting Concrete (TBSCC). Ordinary steel fibers are then added to the concrete volume at various percentages, such as 0.2, 0.4, 0.6, and 0.8. The bond strength, slip, and the method of failure of each rebar were all noted in the test results. The comparison of these results clearly shows that the percentage of steel fiber contributes to the TBSCC bond strength, and conclusions are generated.

Mathematical model for the impact strength of triple-blended steel fiber self-compacting concrete based on the experimental study

This technical research paper deals with the study on the impact strength behavior of steel fiber reinforced self-compacting concrete (SFRSCC) with a triple blended technique. The triple blended means the partial replacement of cement by Fly ash (FA) and condensed silica fume (CSF) by mass. The replacement of cement by FA and CSF were 20and 10 percentages respectively to fulfill the rheological requirements of the Self-compacting concrete (SCC). Steel fibers having 1 mm diameter, 20, 30, and 40 as aspect ratios are used. The steel fibres are added to the volume of the concrete were at 0%, 0.2%, 0.4%, 0.6% and 0.8%. From which the result benefits of the impact strength are studied. The specimens are tested for impact as per ACI specifications. The regression equation is carried out based on experimental values. A mathematical model developed and verified the validity of the equation from the experimental results.

Mechanical properties of geopolymer concrete reinforced with steel and glass fibers with various mineral admixtures

Efforts are being made by several researchers and concrete technologists towards sustainability of concrete. Researchers are working on the replacement of ordinary Portland cement either partly or fully by using mineral admixtures. Geopolymer concrete has been a relatively new development which is becoming popular over the last decade. It is prepared with mineral admixtures, coarse and fine aggregates and certain chemicals so as to undergo polymerization. In the present experimental investigation, the main aim is to develop a more efficient and stronger fiber reinforced geopolymer concrete using several mineral admixtures and fibers so as to recommend it for structural applications. Fiber reinforced geopolymer concrete mixes were produced by employing metallic fibres like steel and non-metallic fibers like glass. Four types of mineral admixtures like fly ash, ground granulated blast furnace slag, condensed silica fume, and metakaolin were mixed in several percentages to serve as the binder. Solidum hydroxide with the required molarity and sodium silicate were used as alkaline liquids for polymerization. Various combinations of fibrous geopolymer concrete mixes by incorporating steel and glass fibers were prepared separately. Specimens were prepared for all the mixes and tested after 28 days of ambient curing for mechanical properties like compression, split tension & flexure. Tests for mechanical properties were conducted on hardened specimens and conclusions are drawn on optimum combinations. From the test results it can be concluded that by reinforcing GPC with fibers strength properties and other benefits can be achieved. The results indicate that fiber reinforced geopolymer concrete may be used for structural applications.

Insights into the microstructure evolution of slag, fly ash and condensed silica fume in blended cement paste

This study traces the spatial microstructure evolution and chemical changes of supplementary cementitious materials (SCMs) during the hydration process at the particle scale. Backscattered electron microscopy and energy-dispersive X-ray spectroscopy (BSE-EDS) techniques coupled with strip delineation image analysis are used to visualize and identify the phase assemblage in the particle region, inner product region and outer product region. The EDS mapping profiles change rapidly in the inner product region and stabilize in the outer product region, which is attributed to the migration of the ions dissolved from the SCMs. The inner products of fly ash and slag display higher Si/Ca and Al/Ca ratios than those in the outer products. It is worth noting that the Mg in the inner product region shows a similar concentration to that in the unreacted slag particle region. In addition, the newly formed C-S-H phase located in the reacting rims could trigger the microcrack within the silica fume agglomeration by inserting expansive forces.

Properties, durability and microstructure of concrete incorporating waste electrical and electronic plastics as partial replacement for aggregates in concrete

This paper presents the results of an experimental study to assess the properties, durability and microstructure of concrete incorporating different types of Waste Electrical and Electronic Plastic (WEEP) as partial replacement of both fine and coarse natural aggregates. These include acrylonitrile-butadiene-styrene, polycarbonate acrylonitrile-butadiene-styrene and high impact polystyrene. Concrete mixtures studied contained 5%, 10%, 20% and 30% WEEP replacement for the natural aggregate. Metakaolin and condensed silica fume were incorporated to enhance the performance of hardened concrete. Results show that all mixes achieved a minimum structural strength of 25 MPa. It was observed that concrete made using WEEP had a lower mechanical strength and durability performance compared to the control mix. This was mainly attributed to the poor bonding between the natural aggregate and WEEP due to the smooth surface associated with WEEP. Microscopy analysis revealed that the pozzolans increased the density of the concrete matrix and reduced the interfacial transition zone which in turn increased the overall performance of mixes containing WEEP.

Impact of condensed silica fume on splitting tensile strength and brittleness of high strength self‐compacting concrete

AbstractSelf‐compacting concrete (SCC) is a type of concrete that can consolidate itself without external compaction. High‐strength SCC (HS‐SCC) is becoming more popular having a very broad range of application in Civil Engineering, such as piles, columns of tall buildings and piers for long‐span bridges. However, HS‐SCC is very brittle that limits its application above. To this, present study aims at mitigating the brittleness of HS‐SCC having a fixed water/binder ratio of 0.30 and binder content of 500 kg/m3 by blending cement with condensed silica fume (CSF). The percentage of CSF that replaced cement was 0–15% by weight. Apart from measuring the brittleness, mechanical property such as splitting tensile and compressive strength, as well as fresh property, such as slump flow, V‐funnel time, and L‐box passing ability was also obtained. The experimental results indicated that 10% replacement of cement by CSF could effectively decrease the brittleness of HS‐SCC and simultaneously increase the 28‐day compressive strength. On the other hand, the slump flow of concrete decreased as the content of CSF increased, but nonetheless was able to maintain at above 600 mm, which is a commonly accepted criteria for SCC. Lastly, scanning electron microscope figures showed that the microstructure of concrete and hydration morphology were enhanced by CSF particle.

Experimental Study on the Presence of Mineral Admixtures and Steel Fiber on the Elastic Properties of Self-Compacting Concrete (SCC)

The elastic properties like young’s modulus and poison’s ratio are critical issues in the design of concrete structures. This technical paper focuses on the influence of the mineral admixtures like flyash and condensed silica fume along with percentage of steel fibers on the compressive strength and elastic properties of self-compacting concrete (SCC). The flow ability, passing ability along with the segregation resistance tests were conducted. Designed the M40 grade of SCC as per American concrete institute (ACI) provisions. The cement is mingle with flyash(FA) at 20% and condensed silica fume(CSF) at 10% as partial replacement by weight. The steel fiber of diameter 1mm and aspect ratio of 40 mixed at 0.2, 0.4, 0.6, and 0.8 percentages by volume of the concrete. The Young’s modulus and Poisson’s ratio are resolved as per American standard for testing materials (ASTM) specifications. Based on the experimental investigation, conclusions drawn on the contribution of mineral admixtures and steel fiber on the compressive strength and elastic properties of SCC. A mathematical model developed and checked the validity of the equation with the experimental results.

Effect of Metakaolin and Condensed Silica Fume on the Rheological and Structural Properties of Self-compacting Concrete

This article deals with the comparison between the metakaolin and condensed silica fume contributions in the flyash based self-compacting concrete (SCC). Self-compacting concrete with mineral admixtures like flyash and condensed silica fume is prepared by cement replacing partially at 20 and 10 percentages respectively. M40 grade of the concrete was designed by adjusting the ratio of the fine aggregate to the total aggregate volume to fulfill the requirements of the SCC. Another M40 grade of SCC is designed with the flyash and metakaolin as the mineral admixtures with the same percentage of replacement for cement by mass. Rheological properties are examined as per EFNARC specifications for flowability; passing ability and segregation resistance for both the triple blended self-compacting concretes (TBSCC). For getting the required flowability of concrete and for modifying the viscous nature of the concrete, superplasticizer and viscosity modifying agents are additionally added to the concrete. The structural properties like compression and split tensile strengths of the specimens are recorded by conducting the standard tests. By comparing the strength results, it is concluded that metakaolin and silica fume have only marginal changes between them in the rheological as well as the mechanical properties of the triple blended self-compacting concrete.

Silica fume-hydrated lime blended cements: contribution of pre-blending to strength development in mortars

ABSTRACT This paper presents an experimental study on the mechanical properties at 28 days of mortars comprising Condensed Silica Fume (CSF), Hydrated Lime (CH) or both, at various substitution rates and water-to-binder ratios (w/b). An evaluation of the mechanical properties has been carried out using Ultrasonic Pulse Velocity (UPV) tests and compressive/tensile strength tests, to assess CSF, CH and CSF-CH addition and substitution rate effect on strength development. A marked increase in the mechanical properties of the CSF, CSF-CH mortars is noted, with the best results obtained after CSF-CH pre-mixing, reaching 35.71% improvement vs control, highlighting the occurrence of considerable pozzolanic reactions. UPV tests have shown increased velocities for CSF and CSF-CH mixes, transcribing a densification of the matrix. The results of the study seem to indicate that CSF and CSF-CH addition could represent a suitable solution to significantly increase both the mechanical and durability properties of mortars.

Regression Analysis for the Axial Strengths of Muti-Blended Steel Fiber Self Compacting Concrete from the Experimentation.

The present paper deals with triple blended Self-Compacting Concrete (SCC) where 53 grade of cement is blended with flyash and Condensed Silica Fume (CSF) at different percentages as replacements to the cement. The steel fiber of diameter 1mm; with an aspect ratios varying from 20,30 and 40 were mixed to get the higher mechanical properties such as compressive and tensile strengths at four different percentages. The required number of cube and the cylindrical specimens of triple blended steel fibrous SCC were prepared and evaluated for compressive and the tensile strengths. The magnitude of the test results have indicated that there is enhancement in the axial strength properties of this type of the concrete as the percentage of steel increases up to certain value to fulfil the needs of the SCC as per the America Concrete Institute (ACI) norm. The regression equation is derived for the experimental values for the compressive and the spilt tensile strength of steel fibere self-compacting concrete (SFSCC) and verified acceptance the equation. The results of present investigation would help in the preparation of optimum tri- blended steel fibrous SCC ,which are suitable for practical usages like floor slabs bridge decks, important highways, airport runways and thin shaped concrete structural elements.

Ultrasonic Pulse Velocity and Morphology of High Strength Concrete with PVC Waste Aggregate

In this paper, morphology and ultrasonic pulse velocity (UPV) of high strength concrete with a relatively high ratio of condensed silica fume and PVC waste aggregate as sand replacement have been examined. The plastic aggregate was obtained from shredding PVC waste sheets used for secondary roofing and covering walls. Variables tested were PVC plastic grading and ratio of sand replacement with such plastic, in addition to curing time of concrete. Results of scanning electron microscopy showed that there is a good bond between PVC aggregate particles and hardened cement paste. There was a relatively small reduction of UPV value of concrete, increased with increasing PVC aggregate content, reached 14.3% at 40% PVC content. The UPV lost is slightly increased with increasing concrete age from 7 days to 56 days. Results also showed that the effect of PVC aggregate grading on the residual UPV is not important. Based on the measured residual properties of high strength with silica fume and PVC granules, there is a high degree of silica fume hydration and the existence of PVC particles has no effect on such hydration.

High Volume Fly Ash Self Compacting Concrete with Lime and Silica Fume as Additives

SCC is expensive when compared with normal conventional concrete. Hence, it is desired to produce low cost SCC by replacing cement with higher percentages of fly ash, which is a no cost material and available in abundance. At the same time to achieve higher grade HVFASCC, micro silica which is otherwise condensed silica fume can also be used along with fly ash to enhance the strength properties of HVFASCC. By replacing fly ash in high volumes in the mix, high amount of pozzolanic material becomes available, majorly reactive silica, for which more calcium hydroxide is necessary for further pozzolanic reaction. As we are reducing cement quantity, the amount of calcium hydroxide available is reduced thus demanding external addition of hydrated lime which can be supplied as additive to cater to the need of calcium hydroxide required for reactive silica in fly ash.The present investigation aims to achieve strength for high volume fly ash self-compacting concrete. The replacement of cement with fly ash is made in 45%, 50%, 55%, 60%, 65% and 70% with 20% hydrated lime and 10% silica fume in one trial. In another trial, 30% hydrated lime and 10% silica fume is added with replacement of fly ash to cement varying in same percentages. The design mix is tested for workability and flowability and cubes are casted for compression strength test and tested at 28 day,, 56 day, and 90 day,.

Special Binding for Refractory Concretes

Abstract The paper shows data related to coexistence of various binding systems, which could be present during the hardening of special concretes. It is taken into account the Ultra Low Aluminous Cement Concretes additivated with different materials (phosphates and mineral ultra dispersed powders - Condensed Silica Fume, Hydrated Alumina etc). In correlation to the pH-value, these substances can favour the forming of new binding systems besides the hydraulic binder (which is not important in this case). The new system is the coagulation binding form. The coagulation binding system has a very important role in the advanced compactness and in the increasing mechanical strengths of concrete structures.

Calcined Marl and Condensed Silica Fume as Partial Replacement for Ordinary Portland Cement

The main objective of this investigation is to replace calcined marl (0, 10, 20%) and condensed silica fume (SF, 0, 7, 10%) partially for ordinary Portland cement (OPC). Marl, a calcium-based supplementary cementitious material (SCM) calcines at a considerably lower temperature (750 °C) than OPC (up to 1480 °C). The calcined marl contributes in prolonged pozzolanic reactions and represents characteristics of latent cement chemistry. To approach the major conclusions, 27 mixes were designed based on the three ratios of water to the total binders (W/B) of 0.38, 0.42 and 0.45. The calcined marl and SF proportioned in mixes with “0, 10 and 20%” and “0, 7 and 10%”, respectively. After the ages of 7, 28 and 90 days all mixes improved, mechanically. In particular, the hardened concretes containing 10 and 20% of calcined marl show stronger reaction for substitution of OPC. In the lower limit of W/B ratio (0.38) mixes with 20% calcined marl exhibit a remarkable increase of some 2.4-fold strengths from 7 to 90 days. Also, the results obtained by tensile strength and modulus of rupture for concrete mixes containing 10 and 20% calcined marl highlight the mechanical progress of hardened concrete after 28 days. Collectively, both SCMs replaced OPC in a considerable amount (up to 30%). However, long-term enhancement in mechanical strength and durability indices are typically supported by calcined marl.

High Performance Concrete with Ternary Binders

Use a ternary binder for production of a high performance concrete with a compressive strengths between 120 and 170 MPa is presented. The water to binder ratio of the concrete is 0.225 and the binder is composed of Ordinary Portland Cement (OPC), condensed silica fume (CSF), ground limestone (L), fly ash (FA) and metakaoline (MK). The dosage of (M + CSF) is kept at a constant level for a better workability of fresh concrete. Different workability, flexural and compressive strengths were obtained for concretes with a constant cement and a metakaoline dosage, and for a constant dosage (FA + L) but a different ratio FA / L. An optimum composition was found and concretes for other tests were designed using this composition.