Showing papers on "Silica fume published in 2021"

Pore structural and fractal analysis of the influence of fly ash and silica fume on the mechanical property and abrasion resistance of concrete

Abstract: Dam concrete suffers from serious abrasion damages in southwestern China, the abrasion resistance of concrete is therefore one of the most important factors determining the reliability even the saf...

Improvement in Fresh, Mechanical and Microstructural Properties of Fly Ash- Blast Furnace Slag Based Geopolymer Concrete By Addition of Nano and Micro Silica

Abstract: In this study, the effect of nano-silica (NS) and silica fume (SF) on workability, setting time, compressive strength and microstructural properties of fly ash-ground granulated blast furnace slag (FA-GGBFS) based geopolymer concrete (GPC) is investigated. Five mixtures of each containing 0.5%, 1.0%, 1.5%, 2.0% and 2.5% NS and SF are prepared for this investigation. The optimum GPC mixture with NS resulted in compressive strength of 63 MPa and the SF modified GPC achieved a compressive strength of 59.59 MPa after 28 days of outdoor temperature curing (Avg. temp. 31.4℃). The hardened concrete samples are analyzed through X-ray diffraction (XRD), X-ray fluorescence (XRF), field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR), and petrographic examination, for the better understanding of geopolymer mineralogy, mechanism and microstructure. Results indicate that both NS and SF facilitated a higher degree of geopolymerization, leading to the densification of the geopolymer matrix which led to the improvement of the properties of FA-GGBFS based GPC.

Recent progress of utilization of activated kaolinitic clay in cementitious construction materials

Abstract: The development of a green alternative that can partially or completely substitute the Ordinary Portland cement (OPC) as a practical construction material with low CO2 footprint is an important subject to researchers for decades. The use of artificial pozzolanic materials, e.g. fly ash, slag, silica fume, etc. cannot meet the huge-scale demand for cement replacement. Kaolinitic clay, with its high pozzolanic reactivity after activation and abundant resources worldwide, is regarded as a promising supplementary cementitious material (SCM) for cement. Recent studies have addressed that the utilization of calcined kaolinitic clay as SCM can effectively improve the properties of cement products. This paper presents a comprehensive review of the research progress on activated kaolinitic clay as SCM in the last decade. It systematically introduces the essential properties, activation mechanism and pozzolanic reactivity assessment of kaolinitic clay. Application of calcined clay in two different cementitious systems (calcined clay blended cement and limestone calcined clay cement) is reviewed from the aspects of workability, mechanical properties, and long-term durability properties with the mechanism discussion. Finally, the environmental and economic impacts of the application of calcined clay in different cementitious systems are discussed.

Studies of Fracture Toughness in Concretes Containing Fly Ash and Silica Fume in the First 28 Days of Curing.

Abstract: This paper presents the results of the fracture toughness of concretes containing two mineral additives. During the tests, the method of loading the specimens according to Mode I fracture was used. The research included an evaluation of mechanical parameters of concrete containing noncondensed silica fume (SF) in an amount of 10% and siliceous fly ash (FA) in the following amounts: 0%, 10% and 20%. The experiments were carried out on mature specimens, i.e., after 28 days of curing and specimens at an early age, i.e., after 3 and 7 days of curing. In the course of experiments, the effect of adding SF to the value of the critical stress intensity factor—KIcS in FA concretes in different periods of curing were evaluated. In addition, the basic strength parameters of concrete composites, i.e., compressive strength—fcm and splitting tensile strength—fctm, were measured. A novelty in the presented research is the evaluation of the fracture toughness of concretes with two mineral additives, assessed at an early age. During the tests, the structures of all composites and the nature of macroscopic crack propagation were also assessed. A modern and useful digital image correlation (DIC) technique was used to assess macroscopic cracks. Based on the conducted research, it was found the application of SF to FA concretes contributes to a significant increase in the fracture toughness of these materials at an early age. Moreover, on the basis of the obtained test results, it was found that the values of the critical stress intensity factor of analyzed concretes were convergent qualitatively with their strength parameters. It also has been demonstrated that in the first 28 days of concrete curing, the preferred solution is to replace cement with SF in the amount of 10% or to use a cement binder substitution with a combination of additives in proportions 10% SF + 10% FA. On the other hand, the composition of mineral additives in proportions 10% SF + 20% FA has a negative effect on the fracture mechanics parameters of concretes at an early age. Based on the analysis of the results of microstructural tests and the evaluation of the propagation of macroscopic cracks, it was established that along with the substitution of the cement binder with the combination of mineral additives, the composition of the cement matrix in these composites changes, which implies a different, i.e., quasi-plastic, behavior in the process of damage and destruction of the material.

Influence of hydroxypropyl methylcellulose and silica fume on stability, rheological properties, and printability of 3D printing foam concrete

Abstract: Printability is a key parameter that affects the application of foam concrete to 3D printing. In this study, the hydroxypropyl methylcellulose (HPMC) and silica fume (SF) were doped into foam concrete as a viscosity modifier and thixotropic agent, and their effects on the stability, rheological properties, and printability of 3D printing foam concrete were investigated. Both HPMC and SF effectively reduced the volume bleeding rate of foam concrete, while HPMC was beneficial for stabilizing the foam, and SF increased the wet density of foam concrete. With the increase in the dosage of HPMC and SF and resting time, the static yield stress, dynamic yield stress, and plastic viscosity of foam concrete increased continuously. SF increased the static yield stress considerably, while HPMC affected the dynamic yield stress and plastic viscosity considerably. It is suggested to combine tanθ and stack height of the printed foam concrete together to evaluate the buildability of 3D printing foam concrete. The suitable ranges of static yield stress, dynamic yield stress and plastic viscosity for 3D printable foam concrete with a wet density from 1550 to 1850 kg/m3 are 1113–1658 Pa, 66.4–230.1 Pa, and 2.08–3.71 Pa s, respectively. The compressive strength of the 3D printed foam concrete with dry density of 1815 kg/m3 in the testing direction Z, Y, and X reached 19.9 MPa, 28.5 MPa and 24.6 MPa, respectively.

Green Concrete Based on Quaternary Binders with Significant Reduced of CO2 Emissions

Abstract: The article presents studies of plain concretes prepared based on a quaternary binder containing various percentages of selected supplementary cementitious materials (SCMs). The possibilities of nanotechnology in concrete technology were also used. An additional important environmental goal of the proposed solution was to create the possibility of reducing CO2 emissions and the carbon footprint generated during the production of ordinary Portland cement (OPC). As the main substitute for the OPC, siliceous fly ash (FA) was used. Moreover, silica fume (SF) and nanosilica (nS) were also used. During examinations, the main mechanical properties of composites, i.e., compressive strength (fcm) and splitting tensile strength (fctm), were assessed. The microstructure of these materials was also analyzed using a scanning electron microscope (SEM). In addition to the experimental research, simulations of the possible reduction of CO2 emissions to the atmosphere, as a result of the proposed solutions, were also carried out. It was found that the quaternary concrete is characterized by a well-developed structure and has high values of mechanical parameters. Furthermore, the use of green concrete based on quaternary binders enables a significant reduction in CO2 emissions. Therefore quaternary green concrete containing SCMs could be a useful alternative to plain concretes covering both the technical and environmental aspects. The present study indicates that quaternary binders can perform better than OPC as far as mechanical properties and microstructures are concerned. Therefore they can be used during the production of durable concretes used to perform structures in traditional and industrial construction.

Mechanical Properties of Silica Fume Modified High-Volume Fly Ash Rubberized Self-Compacting Concrete

Abstract: The existing form of self-compacting concrete (SCC) comprises of a large amount of powdered and fine materials. In this study, a part of the cementitious material was replaced with constant high-volume fly ash, and a portion of fine aggregates was substituted by crumb rubber (CR). Besides that, silica fume (SF) was added, with the hope that by implementing a new type of nanomaterial, the loss in mechanical strength due to previous modifications such as rubberization and replacement will be prevented. Two variables were found to influence the constituent/component in the mix design: SF and CR. The proportion of SF varies from 0% to 10%, while that of CR from 0% to 30% by volume of the total river sand, where 55% of cement was replaced by the fly ash. A total of 13 rubberized SCC samples with CR and SF as controlling variables were made, and their design mix was produced by a Design of Experiment (DOE) under the Response Surface Methodology (RSM). The results reveal a slight increase in the mechanical properties with the addition of SF. The theoretical mathematical models and equation for each different mechanical strength were also developed after incorporating the experimental results into the software.

Mechanical properties of GGBFS-based geopolymer concrete incorporating natural zeolite and silica fume with an optimum design using response surface method

Abstract: Geopolymer concrete (GPC), usually produced via the activation of the cementitious nature of industrial by-products (IBPs) such as ground granulated blast furnace slag (GGBFS) and fly ash (FA), has potential to be used as a replacement for conventional portland concretes (CPCs). In this study, the effect of the concentration of sodium hydroxide (NaOH) and substitution of GGBFS with pozzolans such as natural zeolite (NZ) and silica fume (SF) on the mechanical properties of GPC was investigated experimentally. For this purpose, the compressive, flexural, and tensile strengths of various GPC mixes were measured. GPC mixes were prepared with various concentrations (i.e., 4, 6, and 8 M) of sodium hydroxide as well as GGBFS substitution (i.e., 5, 10, 15, 20, 25, and 30 wt%) with NZ and SF. Furthermore, the response surface method (RSM) was employed to achieve the optimum values of the design variables to maximize the compressive, flexural, and tensile strengths of pozzolanic GGBFS-based GPC. Overall, the results showed that with increasing NaOH concentration, the compressive strength was decreased while the maximum flexural and tensile strengths were obtained when the concentration of NaOH was 6 M compared with 4 and 8 M. In addition, the utilization of NZ improved the compressive, flexural, and tensile strengths of GGBFS-based GPC by about 4%, 6%, and 20%, respectively, at 10 wt% replacement. Moreover, the substitution of GGBFS with SF could improve the compressive, flexural, and tensile strengths of GPC up to 30%, 20%, and 25%, respectively, at 30 wt% substitution. Besides, the optimization results demonstrated that by substituting GGBFS with 60.29 kg (i.e., 15.9%) of NZ and using 5.28 M NaOH the optimal trinary conditions in terms of the compressive, flexural, and tensile strength values could be achieved. The optimal conditions could also be obtained by substituting GGBFS with 113.79 kg (i.e., 30.0%) of SF and using 6.19 M NaOH.

Sustainable development of ultra high performance concrete using geopolymer technology

Abstract: This paper presents the investigation on the adoption of reaction powder concrete (RPC) concept in geopolymer concrete (GPC) technology to develop ultra high performance concrete (UHPC) Ultra high performance geopolymer concrete (UHPGPC) was developed by completely eliminating Portland cement (PC) with industrial by-products such as ground granulated blast furnace slag (GGBFS) and silica fume (SF) activated with sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solution The fresh (flow) and mechanical (compressive strength) properties of the mixes with varying replacement level of GGBFS with silica fume, river sand with quartz powder and the inclusion of steel fibres were investigated The results infer that the inclusion of silica fume, quartz powder and steel fibres has a momentous role on the strength development of the UHPGPC mixes Additionally, statistical analysis has been carried out by design of experiments using response surface methodology The ecological parameters were also assessed with the aid of embodied energy and carbon dioxide emission and the results were compared From the results, it has been inferred that the analytical results were well correlated with the experimental results and the ecological parameters were also less compared to the cement concrete mixes and terms it to be sustainable production

Effect of Addition of Alccofine on the Compressive Strength of Cement Mortar Cubes

Abstract: In the modern era, many research works are going on throughout the world for finding suitable cementitious material for the replacement of cement since it causes environmental pollution. In this order Fly ash, Silica fume, GGBS, Metakaolin, Micro materials, Quartz powder, etc. are tried out for replacing partially or fully the cement in concrete. A new ultrafine material called Alccofine (AF) which is manufactured from glass wastes is tried out for replacing partially in this research. Compressive strength is one of the important properties of cement. Strength tests are not made on neat cement paste because of difficulties of excessive shrinkage and subsequent cracking of neat cement. Cement mortar of 1:3 mix proportion is used to cast the cubes having an area of 50 cm2 are used for the determination of compressive strength of cement as per IS: 4031-1988 (Part-6). The graded Indian Standard sand (Ennore Sand -ES) confirming to IS: 650-1991 is used for preparing the cubes. In the same mix proportion, the same size cubes are cast with the River Sand (RS) to study the difference of the compressive strength between the Indian standard sand and river sand. Ordinary Portland cement (OPC) and Portland Pozzolana Cements (PPC) are used. The present study is the influence of Alccofine on cement mortar cubes by replacing the cement by Alccofine with various proportions like 5%, 10%, 15%, 20% were cast and tested in the laboratory as per Indian Standard 4301-1988 (Part-6) and the results were analysed and presented in the form of charts and graphs. It is observed that the early age strength is obtained for all the combinations but 10 percent of Alccofine yields more strength than other dosages. Doi: 10.28991/esj-2021-01265 Full Text: PDF

Applying a meta-heuristic algorithm to predict and optimize compressive strength of concrete samples

Abstract: The successful use of fly ash (FA) and silica fume (SF) materials has been reported in the design of concrete samples in the literature. Due to the benefits of using these materials, they can be utilized in many industrial applications. However, the proper use of them in the right mixes is one of the important factors with respect to the strength and weight of concrete. Therefore, this paper develops relationships based on meta-heuristic (MH) algorithms (artificial bee colony technique) to evaluate the compressive strength of concrete specimens using laboratory experiments. A database comprising silica fume replacement ratio, fly ash replacement ratio, total cementitious material, water content coarse aggregate, high-rate water-reducing agent, fine aggregate, and age of samples, as model inputs, was used to evaluate and predict the compressive strength of concrete samples. Developed models of the MH technique created relationships between the mentioned parameters. In the new models, the influence of each parameter on the compressive strength was determined. Finally, using the developed model, optimum conditions for compressive strength of concrete samples were presented. This paper demonstrated that the MH algorithms are able to develop relationships that can serve as good substitutes for empirical models.