scholarly journals Rheology of Alkali-Activated Blended Binder Mixtures

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5405
Author(s):  
Biruk Hailu Tekle ◽  
Ludwig Hertwig ◽  
Klaus Holschemacher
Keyword(s):  
Sodium Hydroxide ◽  
Rheological Properties ◽  
Yield Stress ◽  
Sodium Silicate ◽  
Total Solid ◽  
Environmental Benefits ◽  
Total Water ◽  
The Past ◽  
Binder Ratio ◽  
Alkali Activated

Alkali-activated cement (AAC) is an alternative cement that has been increasingly studied over the past decades mainly because of its environmental benefits. However, most studies are on heat-cured AACs and are focused on mechanical properties. There is a lack of research on the fresh properties of ambient-cured AAC systems. This study investigates the rheological properties of ambient-temperature-cured alkali-activated blended binder mixtures activated with sodium silicate and sodium hydroxide solutions. The influence of binder amount, alkaline solid to binder ratio (AS/B), sodium silicate to sodium hydroxide solids ratio (SS/SH), and total water content to total solid (from the binding materials) ratio (TW/TS) on the rheological properties are investigated. The effect of borax as an admixture and silica fume as a replacement for fly ash is also investigated. The results showed that both the yield stress and plastic viscosity are mainly affected by the binder content and TW/TS ratio decreasing with the increase of each parameter. The yield stress increased with the increase of the SS/SH ratio. Borax significantly reduced the yield stress, while silica fume’s effect was dependent on its dosage.

scholarly journals The Effect of the Activator/Precursor Ratio on the Rheological Properties of the Alkali-activated Mining Waste Mud Paste

2020 ◽  
Author(s):  
Abdelhakim Benhamouda ◽  
João Castro-Gomes ◽  
Luiz Pereira-de-Oliveira
Keyword(s):  
Compressive Strength ◽  
Sodium Hydroxide ◽  
Rheological Properties ◽  
Yield Stress ◽  
Rheological Behaviour ◽  
Mining Waste ◽  
Bingham Model ◽  
Precursor Ratio ◽  
Alkali Activated ◽  
The Ideal

To determine the properties of paste, mortar or concrete, it is necessary to understand its rheological behaviour first. This study discusses the effect of the activator/precursor ratio on the rheological properties of the alkali-activated paste. The pastes consisted of a mix of 70 % of tungsten mining waste mud, 15% waste glass and 15% of metakaolin. This mix was activated by combining sodium hydroxide and sodium silicate. Five activator/precursor (a/p) ratios were studied: 0.37, 0.38, 0.39, 0.40 and 0.41. The result obtained shows that the rheology of the pastes is affected by the activator/precursor ratio. The rheological behaviour of the paste fits the Bingham model. The yield stress (τ0) and plastic viscosity (μ) increase inversely with the activator/precursor ratio (e.g. a/p=0.37 gives τ0=84.19 and μ=0.4185; a/p=0.41 gives τ0=30.389 and μ=0.2937). The workability increases proportionally with the activator/precursor ratio (e.g. a/p=0.37 gives a slump=133 mm; a/p=0.41 gives a slump=158 mm). The compressive strength decreases when the activator/precursor ratio increases (e.g. at 28 days for a/p=0.37, the compressive strength was 19.6 MPa; for a/p=0.41, the compressive strength was 13 MPa). Finally, the ideal ratios were 0.38 and 0.39.

scholarly journals Influence of Activator on the strength of Ultra Fine Natural Steatite Powder based on Geopolymer Mortar

2019 ◽  
Vol 9 (1S3) ◽  
pp. 416-420
Keyword(s):  
Compressive Strength ◽  
Sodium Hydroxide ◽  
Sodium Silicate ◽  
Binding Property ◽  
Al Content ◽  
Super Plasticizer ◽  
Binder Ratio ◽  
Polymer Mortar ◽  
Soluble Base ◽  
Alkali Activated

In this study the detailed analysis was made on alkali activated ultra fine natural steatite powder (UFNSP) mortars. The activating alkali was prepared through sodium hydroxide and sodium silicate with different molarities concentration of NaOH. The molarities of NaoH are various from 8, 10, 12, 14 and 16. The proportion of sodium hydroxide and sodium silicate proportion are fixed 1:2.5. Further the strength gained was accelerated through polyvinyl alcohol [PVA]. And various water binder ratio of 0.5, 0.6, 0.7, 0.8 and 0.9 with addition of PVA. For workability purpose super plasticizer was used, here Poly carboxylic ether was used as a superplasticizer. These various ratios concentration of alkali activators were tried on compressive strength of polymer mortar and the results were discussed. The watched outcomes demonstrate that, increment in sodium hydroxide content in soluble base fluid expands the strength. Exhibit the outcome was effect of Si/Al proportion on compressive strength of the specimen with various water binder proportions. In general, the study shows that integrating low ratio of Si/Al content in UFNSP with PVA can fetch low binding property on alkali activator UFNSP material.

Study of Manufacture Process and Properties of Tailings and Slag Based Geopolymers

2010 ◽  
Vol 156-157 ◽  
pp. 803-807
Author(s):  
Fu Sheng Niu ◽  
Shan Shan Zhou ◽  
Shu Xian Liu ◽  
Jin Xia Zhang
Keyword(s):  
Compressive Strength ◽  
Sodium Hydroxide ◽  
Sodium Silicate ◽  
Raw Material ◽  
Silicate Concentration ◽  
High Compressive Strength ◽  
Curing Period ◽  
Manufacture Process ◽  
Alkali Activated

The tailings and slag based geopolymers was prepared by sodium silicate, sodium hydroxide alkali-activated tailings and slag. The compressive strength in 7 d under different raw material proportion were tested. The result indicated that tailings and slag based geopolymers has high compressive strength . As the tailings in slag is 80%, the compressive strength in 7d can reach 45.10 MPa . As the Na2SiO3 to NaOH ratio is 0.5, the compressive strength in 7d can reach 63.79 MPa. As the NaOH and sodium silicate concentration in the solution is 35%, the compressive strength in 7d can reach 38.35 MPa respectively; As the curing period is 14 d , the compressive strength can reach 71.25 MPa. As the steel scoria in solid is 20%, the compressive strength in 7d can reach 61.86 MPa respectively.

scholarly journals Pressure-Induced Geopolymerization in Alkali-Activated Fly Ash

2018 ◽  
Vol 10 (10) ◽  
pp. 3538 ◽  
Author(s):  
Sol Park ◽  
Hammad Khalid ◽  
Joon Seo ◽  
Hyun Yoon ◽  
Hyeong Son ◽  
...  
Keyword(s):  
Fly Ash ◽  
Sodium Hydroxide ◽  
Sodium Silicate ◽  
Sodium Silicate Solution ◽  
Silicate Solution ◽  
Elevated Pressure ◽  
X Ray Diffraction ◽  
27Al Mas Nmr ◽  
Alkali Activated

The present study investigated geopolymerization in alkali-activated fly ash under elevated pressure conditions. The fly ash was activated using either sodium hydroxide or a combination of sodium silicate solution and sodium hydroxide, and was cured at 120 °C at a pressure of 0.22 MPa for the first 24 h. The pressure-induced evolution of the binder gel in the alkali-activated fly ash was investigated by employing synchrotron X-ray diffraction and solid-state 29Si and 27Al MAS NMR spectroscopy. The results showed that the reactivity of the raw fly ash and the growth of the zeolite crystals were significantly enhanced in the samples activated with sodium hydroxide. In contrast, the effects of the elevated pressure conditions were found to be less apparent in the samples activated with the sodium silicate solution. These results may have important implications for the binder design of geopolymers, since the crystallization of geopolymers relates highly to its long-term properties and functionality.

scholarly journals Mix-design and Properties of Mortars from Alkali-activated Fly Ashes Containing High Amounts of Unburned Carbon Matter

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Stefania Manzi ◽  
Andrea Saccani ◽  
Luca Baldazzi ◽  
Isabella Lancellotti
Keyword(s):  
Ad Hoc ◽  
Environmental Benefits ◽  
Mix Design ◽  
Unburned Carbon ◽  
Carbonaceous Matter ◽  
Fly Ashes ◽  
Fresh State ◽  
Binder Ratio ◽  
Alkali Activated ◽  
Promising Type

AbstractAlkali-activated materials are a promising type of binder candidate as a substitute to Portland cement. Fly ashes can be used as binder precursors giving higher environmental benefits. In the present research, fly ashes (Type F) containing different amounts of unburned carbonaceous matter have been used to formulate mortars. Serious problems concerning the workability in the fresh state have been found when high carbon content are reached. An attempt to avoid the preliminary treatments used to eliminate the unburned matter is carried out by exploiting different mix-design receipts obtained by changing the water/binder ratio, the ratio of the alkaline activators and using different types of superplasticizer additives. Data so far collected underline that a high amount of unburned carbonaceous matter can not only compromise the mechanical properties of the materials, but also the rheological ones and underline the necessity to develop ad hoc additives for this type of binders.

scholarly journals Evolution of flow properties, plastic viscosity, and yield stress of alkali-activated fly ash/slag pastes

2020 ◽  
Vol 5 ◽  
pp. 141-149
Author(s):  
Mohammed Fouad Alnahhal ◽  
Taehwan Kim ◽  
Ailar Hajimohammadi
Keyword(s):  
Fly Ash ◽  
Yield Stress ◽  
Plastic Viscosity ◽  
Rheological Parameters ◽  
Time Intervals ◽  
Increasing Trend ◽  
Binder Ratio ◽  
Drastic Effect ◽  
Effect On Yield ◽  
Alkali Activated

The development of cementless concrete is attracting increasing attention in practice and research to reduce both greenhouse gas emissions and energy consumption of concrete. Alkali-activated materials (AAMs) are one of the viable alternatives to replace Portland cement due to their lower CO2 emissions. This study investigated the evolution of rheological parameters of alkali-activated fly ash/slag pastes as a function of time. Flowability and rheological measurements were carried out to determine the fluidity, plastic viscosity, and yield stress at different time intervals. The effects of the slag content, the concentration of SiO2 in the activator, and the solution/binder ratio were considered. Based on the results, the yield stress and plastic viscosity followed an increasing trend over time coinciding with a reduction in the paste fluidity. The plastic viscosity of AAM pastes was in the range of 1.3–9.5 Pa.s and 2.6–28.9 Pa.s after 5 min and 45 min of mixing, respectively. Given the same alkali activator, the higher content of slag the paste had, the higher yield stress the paste showed. In addition, this paper confirmed that the SiO2/Na2O ratio in the activator had no significant effect on yield stress, but a drastic effect of this ratio was found on the plastic viscosity of the paste.

scholarly journals Interaction of Magnesia with Limestone-Metakaolin-Calcium Hydroxide Ternary Alkali-Activated Systems

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
A. Cwirzen ◽  
L. Metsäpelto ◽  
K. Habermehl-Cwirzen
Keyword(s):  
Sodium Hydroxide ◽  
Calcium Hydroxide ◽  
Sodium Silicate ◽  
Ternary Systems ◽  
Sodium Sulphate ◽  
Crystalline Phases ◽  
Amorphous Phases ◽  
Porous Microstructure ◽  
Alkali Activated

The effect of magnesia on ternary systems composed of limestone, metakaolin and calcium hydroxide, alkali activated with sodium silicate, sodium hydroxide, and sodium sulphate was studied by determination of the compressive strength, X-ray powder diffraction (XRD), thermogravimetry (TG), and scanning electron microscope (SEM). Pastes activated with sodium silicate and sodium sulphate showed strength regression caused by a formation of an unstable prone to cracking geopolymer gel. The presence of magnesia in sodium hydroxide-activated system hindered this trend by promoting a formation of more stable crystalline phases intermixed with brucide. In general, magnesia densified the binder matrix by promoting a formation of amorphous phases while sodium hydroxide produced the most porous microstructure containing high amount of crystalline phases.

Effect of sodium hydroxide and sodium silicate solutions on strengths of alkali activated high calcium fly ash containing Portland cement

2016 ◽  
Vol 21 (6) ◽  
pp. 2202-2210 ◽  
Author(s):  
Tanakorn Phoo-ngernkham ◽  
Sakonwan Hanjitsuwan ◽  
Nattapong Damrongwiriyanupap ◽  
Prinya Chindaprasirt
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Sodium Hydroxide ◽  
Sodium Silicate ◽  
High Calcium ◽  
High Calcium Fly Ash ◽  
Alkali Activated

Optimum Mixture Design of Bottom Ash Based Alkali-Activated Mortar Using Artificial Neural Networks

2010 ◽  
Vol 452-453 ◽  
pp. 733-736
Author(s):  
Su Tae Kang ◽  
Hyun Jin Kang ◽  
Gum Sung Ryu ◽  
Gyung Taek Koh ◽  
Jang Hwa Lee
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Sodium Hydroxide ◽  
Sodium Silicate ◽  
Experimental Studies ◽  
Bottom Ash ◽  
Mixture Design ◽  
Curing Temperature ◽  
Artificial Neural ◽  
Alkali Activated

Bottom ash based alkali-activated mortar is prepared by incorporating sodium hydroxide and sodium silicate with some additional water if needed, and is activated with temperature curing. This research was conducted to derive an optimum mixture design of the bottom ash based alkali-activated mortar. The experimental studies were first performed to estimate the effect of the added water content, alkali activator to bottom ash ratio, sodium silicate to sodium hydroxide ratio as well as curing temperature on workability and strength. In order to optimize the mix proportion, based on the experimental results, artificial neural networks were introduced.

Study of Manufacture Process and Properties of Tailings and Slag Based Mine Filling Cementitious Materials

2013 ◽  
Vol 734-737 ◽  
pp. 1077-1081 ◽  
Author(s):  
Jin Xia Zhang ◽  
Shu Xian Liu ◽  
Jun Xie
Keyword(s):  
Compressive Strength ◽  
Sodium Hydroxide ◽  
Sodium Silicate ◽  
Raw Materials ◽  
Cementitious Materials ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Manufacture Process ◽  
Alkali Activated

The tailings and slag based mine filling cementitious materials was prepared by sodium silicate and sodium hydroxide alkali-activated tailings and slag. Through the test that the cementing materials in the best ratio of raw materials: when slag and tailings admixture is 1.25, the content of NaOH was 50%, the amount of sodium hydroxide for 50%, water cement ratio of 0.22, under the condition of normal temperature curing 7 days, eventually making a compressive strength of 52.3MPa cementing materials.

Sign in / Sign up

Export Citation Format

Share Document