scholarly journals Influence of different sources of coal gangue used as aluminosilicate powder on the mechanical properties and microstructure of alkali-activated cement

2019 ◽  
Vol 69 (336) ◽  
pp. 199 ◽  
Author(s):  
B. J. Frasson ◽  
R. C.A. Pinto ◽  
J. C. Rocha
Keyword(s):  
Mechanical Properties ◽  
Coal Mining ◽  
Building Materials ◽  
Mechanical Performance ◽  
Pulse Velocity ◽  
Coal Gangue ◽  
Microstructural Development ◽  
Mining Wastes ◽  
Alkali Activated ◽  
Alkali Activated Cement

Coal mining wastes are associated with serious environmental problems; they have potential as building materials, including alkali-activated cement. In this study, the effect of different coal mining wastes on the mechanical properties and microstructural development of alkali-activated materials (AAMs) was evaluated through XRD, SEM and FTIR spectroscopy. Different alkali-activated compounds were produced; the alkaline solution was composed of NaOH+Na2SiO3. The results obtained using the calcined coal sludge showed excellent mechanical performance, with compressive strength higher than 60 MPa. However, addition of metakaolin and ordinary Portland cement was necessary to increase the mechanical performance of calcined coal gangue materials. The formation of N-A-S-H gel and the incorporation of iron ions into the cementitious matrix were evidenced. Ultrasonic pulse velocity indicated the early polymerization during the reaction processes. The study verified that the different characteristics of the wastes influence the performance of alkali-activated materials.

MECHANICAL PROPERTIES OF FLY ASH-BASED ALKALI-ACTIVATED CEMENT USING A STATISTICAL ANALYSIS TECHNIQUE

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Hyuk Lee ◽  
Vanissorn Vimonsatit
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Statistical Analysis ◽  
Fly Ash ◽  
Silica Fume ◽  
Dry Density ◽  
Analysis Method ◽  
Solid Ratio ◽  
Alkali Activated ◽  
Alkali Activated Cement

This paper presents the mechanical properties of fly ash-based alkali-activated cement (AAC). A statistical analysis method was used to determine the effect of mix proportion parameters on the dry density and compressive strength of fly ash-based AAC pastes and mortars. For that purpose, sample mixtures were designed according to Taguchi’s experimental design method, i.e., in a L9 orthogonal array. Four factors were selected: “silica fume content” (SF), “sand to solid ratio” (s/c), “liquid to solid ratio” (l/s), and “superplasticiser content” (SP). The experimental results were analysed by using signal to noise for quality control of each mixture, and analysis of variance (ANOVA) was used to determine the significant effect on the compressive strength of fly ash-based AAC. Furthermore, a regression-analysis method was used to predict the compressive strength according to the variation of the four factors. Results indicated that silica fume is the most influencing parameter on compressive strength, which could be decreased by superplasticiser and l/s ratio. There is no significant effect of sand-to-cementitious ratio on compressive strength of fly ash-based AAC. The dry density decreases as the sand-to-cementitious ratio is decreased. The increasing l/s ratio and superplasticiser dosage could further decrease the dry density of fly ash-based AAC.

scholarly journals Cement Paste Mixture Proportioning with Particle Packing Theory: An Ambiguous Effect of Microsilica

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6970
Author(s):  
Paweł Niewiadomski ◽  
Anna Karolak ◽  
Damian Stefaniuk ◽  
Aleksandra Królicka ◽  
Jacek Szymanowski ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cement Paste ◽  
Building Materials ◽  
Mechanical Performance ◽  
Physical And Mechanical Properties ◽  
Sio2 Nanoparticles ◽  
Negative Influence ◽  
Particle Packing ◽  
Cement Pastes ◽  
Low Porosity

Recently, the research of innovative building materials is focused on applying supplementary materials in the form of micro- and nanopowders in cementitious composites due to the growing insistence on sustainable development. Considering above, in paper, a research on the effect of microsilica and SiO2 nanoparticles addition to cement paste, designed with Andreasen and Andersen (AA) packing density model (PDM), in terms of its physical and mechanical properties was conducted. Density, porosity, compressive strength, hardness, and modulus of indentation were investigated and compared regarding different amount of additives used in cement paste mixes. Microstructure of the obtained pastes was analyzed. The possibility of negative influence of alkali-silica reaction (ASR) on the mechanical properties of the obtained composites was analyzed. The results of the conducted investigations were discussed, and conclusions, also practical, were presented. The obtained results confirmed that the applied PDM may be an effective tool in cement paste design, when low porosity of prepared composite is required. On the other hand, the application of AA model did not bring satisfactory results of mechanical performance as expected, what was related, as shown by SEM imaging, with inhomogeneous dispersion of microsilica, and creation of agglomerates acting as reactive aggregates, what as a consequence caused ASR reaction, crack occurrence and lowered mechanical properties. Finally, the study found that the use of about 7.5% wt. of microsilica is the optimum in regards to obtain low porosity, while, to achieve improved mechanical properties, the use of 4 wt. % of microsilica seems to be optimal, in the case of tested cement pastes.

Electrical Properties of Alkali-Activated Slag Mortar with Carbon Fibres

2017 ◽  
Vol 908 ◽  
pp. 100-105 ◽  
Author(s):  
Pavel Rovnaník ◽  
Maria Míková ◽  
Ivo Kusák
Keyword(s):  
Mechanical Properties ◽  
Electrical Properties ◽  
Building Materials ◽  
Specific Conductivity ◽  
Carbon Fibres ◽  
Alkali Activated Slag ◽  
Order Of Magnitude ◽  
Activated Slag ◽  
Mixing Water ◽  
Alkali Activated

Building materials with enhanced electrical properties gain the importance in the new field of applications such as self-sensing or self-heating materials. In this paper, 3 mm long carbon fibres were used as a conductive admixture to alkali-activated slag mortar in order to reduce its resistivity. The amount of carbon fibres was ranging from 0.5 to 4.0% of the slag mass and the effect of the conductive admixture on the mechanical properties, electrical impedance, specific conductivity, and microstructure of alkali-activated slag composite was investigated. Only 0.5% of carbon fibres caused a significant decrease in impedance of alkali-activated slag composite and the addition of 4% reduced the impedance by one order of magnitude for low AC frequencies. However, due to problematic dispersion and higher demand of mixing water, the mechanical properties were deteriorated, especially at higher content of carbon fibres.

scholarly journals Investigation of the Effect of Mixing Time on the Mechanical Properties of Alkali-Activated Cement Mixed with Fly Ash and Slag

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2301
Author(s):  
Taewan Kim ◽  
Choonghyun Kang
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Mixing Time ◽  
Blending Method ◽  
Mixing Method ◽  
The Difference ◽  
High Alkali ◽  
Mixed Water ◽  
Alkali Activated ◽  
Alkali Activated Cement

This is an experiment on the effect of mixing time for alkali-activated cement (AAC) using a binder mixed with ground granulated blast furnace slag (slag) and fly ash (FA) in a ratio of 1:1 on the mechanical properties. The mixing method of ASTM C305 was used as the basic mixing method, and the following mixing method was changed. Simply adding the same mixing time and procedure, the difference in the order of mixing slag and FA, and controlling the amount of activator and mixed water were considered. As a result of the experiment, the addition of the same mixing time and procedure, pre-injection of slag, and high-alkali mixed water in which half of the activator and mixing water were mixed showed the highest mechanical properties and a dense pore structure. As a result, the design of a blending method that can promote the activation action of slag rather than FA at room temperature was effective in improving the mechanical properties of AAC. In addition, these blending factors showed a clearer effect as the concentration of the activator increased. Through the results of this experiment, it was shown that high-temperature curing, high fineness of the binder, or even changing the setting of the mixing method without the use of excessive activators can lead to an improvement of mechanical properties.

scholarly journals Experimental Evaluation of Untreated and Pretreated Crumb Rubber Used in Concrete

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 558
Author(s):  
Hamad Hassan Awan ◽  
Muhammad Faisal Javed ◽  
Adnan Yousaf ◽  
Fahid Aslam ◽  
Hisham Alabduljabbar ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Water Treatment ◽  
Mechanical Performance ◽  
Strength Loss ◽  
Ultrasonic Pulse Velocity ◽  
Crumb Rubber ◽  
Pulse Velocity ◽  
Unit Weight ◽  
Lime Treatment

The present research aims at evaluating the mechanical performance of untreated and treated crumb rubber concrete (CRC). The study was also conducted to reduce the loss in mechanical properties of CRC. In this study, sand was replaced with crumb rubber (CR) with 0%, 5%, 10%, 15%, and 20% by volume. CR was treated with NaOH, lime, and common detergent for 24 h. Furthermore, water treatment was also carried out. All these treatments were done to enhance the mechanical properties of concrete that are affected by adding CR. The properties that were evaluated are compressive strength, indirect tensile strength, unit weight, ultrasonic pulse velocity, and water absorption. Compressive strength was assessed after 7 and 28 days of curing. The mechanical properties were decreased by increasing the percentage of the CR. The properties were improved after the treatment of CR. Lime treatment was found to be the best treatment of all four treatments followed by NaOH treatment and water treatment. Detergent treatment was found to be the worse treatment of all four methods of treatment. Despite increasing the strength it contributed to strength loss.

scholarly journals Mechanical Performance of High-Strength Sustainable Concrete under Fire Incorporating Locally Available Volcanic Ash in Central Harrat Rahat, Saudi Arabia

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 21
Author(s):  
Muhammad Nasir Amin ◽  
Kaffayatullah Khan
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elevated Temperature ◽  
Volcanic Ash ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
High Strength ◽  
Pulse Velocity ◽  
Sustainable Concrete ◽  
Harrat Rahat

This study investigated the effect of elevated temperatures on the mechanical properties of high-strength sustainable concrete incorporating volcanic ash (VA). For comparison, control and reference concrete specimens with fly ash (FA) were also cast along with additional specimens of VA and FA containing electric arc furnace slag (EAFS). Before thermal exposure, initial tests were performed to evaluate the mechanical properties (compressive strength, tensile strength, and elastic modulus) of cylindrical concrete specimens with aging. Additionally, 91 day moist-cured concrete specimens, after measuring their initial weight and ultrasonic pulse velocity (UPV), were exposed up to 800 °C and cooled to air temperature. Subsequently, the weight loss, residual UPV, and mechanical properties of concrete were measured with respect to exposure temperature. For all concrete specimens, test results demonstrated a higher loss of weight, UPV, and other mechanical properties under exposure to higher elevated temperature. Moreover, all the results of concrete specimens incorporating VA were observed before and after exposure to elevated temperature as either comparable to or slightly better than those of control and reference concrete with FA. According to the experimental results, a correlation was developed between residual UPV and residual compressive strength (RCS), which can be used to assess the RCS of fire-damaged concrete (up to 800 °C) incorporating VA and EAFS.

scholarly journals Characteristics of Preplaced Aggregate Concrete Fabricated with Alkali-Activated Slag/Fly Ash Cements

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 591
Author(s):  
Salman Siddique ◽  
Hyeju Kim ◽  
Hyemin Son ◽  
Jeong Gook Jang
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Water Absorption ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Cement Grout ◽  
Aggregate Concrete ◽  
Alkali Activated ◽  
Alkali Activated Cement

This study assesses the characteristics of preplaced aggregate concrete prepared with alkali-activated cement grout as an adhesive binder. Various binary blends of slag and fly ash without fine aggregate as a filler material were considered along with different solution-to-solid ratios. The properties of fresh and hardened grout along with the properties of hardened preplaced concrete were investigated, as were the compressive strength, ultrasonic pulse velocity, density, water absorption and total voids of the preplaced concrete. The results indicated that alkali-activated cement grout has better flowability characteristics and compressive strength than conventional cement grout. As a result, the mechanical performance of the preplaced aggregate concrete was significantly improved. The results pertaining to the water absorption and porosity revealed that the alkali-activated preplaced aggregate concrete is more resistant to water permeation. The filling capacity based on the ultrasonic pulse velocity value is discussed to comment on the wrapping ability of alkali-activated cement grout.

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