alkaline activator
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Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 307
Author(s):  
Zhengdong Luo ◽  
Biao Luo ◽  
Yufei Zhao ◽  
Xinyu Li ◽  
Yonghua Su ◽  
...  

To solve the issues of insufficient early strength of cement stabilized soil and high resource cost, high reduction cost, and high environmental cost induced by the application of cement, the slag and fly ash-based geopolymer was adopted as the stabilizer to treat riverside soft soil. This study mainly investigated the effects of stabilizer content, slag-to-fly ash ratio, and alkaline activator content on the strength of geopolymer stabilized soils with different curing ages. Unconfined compressive strength (UCS), scanning electron microscope (SEM), and X-ray energy spectrum analysis (EDS) tests were carried out. The results show that the stabilizer content, slag–fly ash ratio, and alkaline activator content have a decisive influence on the UCS of geopolymer-stabilized soil. The mix-proportions scheme of geopolymer stabilized riverside soft soil, with a geopolymer content of 15%, a slag–fly ash ratio of 80:20, and an alkaline activator content of 30%, is considered optimum. It is proven by SEM that the uniformly distributed gelatinous products formed in the geopolymer-stabilized soil bind the soil particles tightly. Moreover, the EDS analysis confirms that the gelatinous products are mainly composed of C-S-H gel and sodium-based aluminosilicate (N-A-S-H).


Molecules ◽  
2022 ◽  
Vol 27 (2) ◽  
pp. 498
Author(s):  
Ana María Moreno de los Moreno de los Reyes ◽  
José Antonio Suárez-Navarro ◽  
María del Mar Alonso ◽  
Catalina Gascó ◽  
Isabel Sobrados ◽  
...  

The use of more eco-efficient cements in concretes is one of the keys to ensuring construction industry sustainability. Such eco-efficient binders often contain large but variable proportions of industrial waste or by-products in their composition, many of which may be naturally occurring radioactive materials (NORMs). This study explored the application of a new gamma spectrometric method for measuring radionuclide activity in hybrid alkali-activated cements from solid 5 cm cubic specimens rather than powder samples. The research involved assessing the effect of significant variables such as the nature of the alkaline activator, reaction time and curing conditions to relate the microstructures identified to the radiological behavior observed. The findings showed that varying the inputs generated pastes with similar reaction products (C-S-H, C-A-S-H and (N,C)-A-S-H) but different microstructures. The new gamma spectrometric method for measuring radioactivity in solid 5 cm cubic specimens in alkaline pastes was found to be valid. The variables involved in hybrid cement activation were shown to have no impact on specimen radioactive content. The powder samples, however, emanated 222Rn (a descendent of 226Ra), possibly due to the deformation taking place in fly ash structure during alkaline activation. Further research would be required to explain that finding.


2022 ◽  
Vol 955 (1) ◽  
pp. 012010
Author(s):  
A Kustirini ◽  
Antonius ◽  
P Setiyawan

Abstract Geopolymer concrete is concrete that uses environmentally friendly materials, using fly ash from waste materials from the coal industry as a substitute for cement. To produce geopolymer concrete, an alkaline activator is required, with a mixture of Sodium Hydroxide and Sodium Silicate. This research is an experimental study to determine the effect of variations in the concentration of sodium hydroxide (NaOH) 8 Mol, 10 Mol, 12 Mol, and 14 Mol on the compressive strength of geopolymer concrete. Mortar Geopolymer uses a mixture of 1: 3 for the ratio of fly ash and sand, 2.5: 0.45 for the ratio of sodium silicate and sodium hydroxide as an alkaline solution. The specimens used a cube mold having dimension 5 cm x 5 cm x 5 cm, then tested at 7 days and 28 days. The test resulted that concentration of NaOH 12 Mol obtained the maximum compressive strength of geopolymer concrete, that is 38.54 MPa. At concentrations of 12 Mol NaOH and exceeding 12M, the compressive strength of geopolymer concrete decreased.


2021 ◽  
Vol 2021 (2) ◽  
pp. 52-57
Author(s):  
Uliana Marushchak ◽  
◽  
Myroslav Sanytsky ◽  
Nazar Sydor ◽  
Ihor Margal ◽  
...  

The development of high-performance materials, which are characterized by high compressive and flexural strength, durability and performance properties, is an urgent problem of modern construction. Engineered cementitious composites are one such material. Improving of properties of composites is achieved by partial replacement of cement with supplementary cementitious materials. The ratio of binder and filler components and superplasticizer consumption were selected. The optimal ratio of cement:fly ash:sand is 1:1:1 and the dosage of polycarboxylate superplasticizer is 0.75% by weight of the binder. The reduction of the negative impact of the increased amount of fly ash, which is characterized by low reactivity, is provided by the introduction of metakaolin and alkaline hardening activator. Alkaline activated cement system is characterized by increasing of the early strength in 1.5 times comparison with equivalent mixture without alkaline activator. Strength of alkaline activated cementing matrix after 28 days is 66.1 MPa and specific strength Rc2/Rc28 is 0.61.


Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7303
Author(s):  
Zhibing Xing ◽  
Fenglan Han ◽  
Jiuliang Tian ◽  
Zhichao Xu ◽  
Jiaqi Wang ◽  
...  

A large number of natural aggregates are used in the field of construction materials, resulting in the exhaustion of natural aggregates. Therefore, looking for an alternative will slow down the consumption of natural aggregates. The sintering method not only consumes a lot of energy to prepare aggregates but also produces a lot of pollutants. In this study, silico-manganese (SM) slag was dried, ground into powder, and used as raw material. Solid and liquid alkaline activator methods were used to prepare SM slag non-burning aggregate (SMNA) by the cold bonding method. The effects of grinding time, amounts of solid and liquid alkaline activators, curing temperature, and the amount of added fly ash on aggregate properties were investigated. The aggregate microstructure was characterized by XRD, SEM, and FTIR methods, and the toxic leaching analysis of aggregate was performed. The results showed that with a fixed amount of liquid activator (16.2% wt.) and solid activator (15% wt.) and fly ash (20% wt.), respectively, and curing was performed at room temperature, the aggregate properties were optimal: the bulk density of 1236.6–1476.9 kg/m3 and the water absorption lower than 4.9–5.5%. The apparent density was 1973.1–2281.6 kg/m3, and the bulk crushing strength was 24.7–27.9 MPa. The XRD, SEM, and FTIR results indicated that amorphous gel could be formed from SM under an alkaline activator, improving the aggregate strength. The results of toxic leaching showed that the aggregate prepared from SM exhibited environmentally friendly characteristics. The SMNA was obtained via the simple and low-energy consumption production process, paving the new way toward large-scale utilization of SM.


Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4160
Author(s):  
Xiaoyun Yang ◽  
Yan Zhang ◽  
Zhuhan Li ◽  
Minglei Wang

Coal gangue-slag geopolymer is a kind of environment-friendly material with excellent engineering performance and is formed from coal gangue and slag after excitation by an alkaline activator. In this study, three kinds of coal gangue-slag geopolymer were activated by different activators, and the compressive and flexural strengths of water and sulphate solutions in the wetting-drying (W-D) cycles were compared. The microscopic mechanism was analyzed by the XRD, the FTIR and the SEM. The following conclusions are drawn: The influence of W-D cycles on flexural strength was greater than compressive strength. The water migration and the recombination of geopolymers lead to the change of colour, as well as the reduction of flexural strength and compressive strength of geopolymers. The SH geopolymer had excellent anti-erosion ability in terms of flexural strength, and the reason for this was the recombination and polymerization reaction of geopolymer being weaker than the SS and the SSG. The corrosion resistance of the SS was reflected in the compressive strength, because its geopolymerization reaction was fierce, which produced more Na-rich C–N–A–S–H, N–A–S–H and C–A–S–H gels. Therefore, the compressive strength could still reach more than 39 MPa after 150 cycles. Sulfate solution could effectively control the reduction of compressive strength of the SH and the SS geopolymers during W-D cycles. The SSG had the worst corrosion resistance.


2021 ◽  
Vol 904 ◽  
pp. 387-391
Author(s):  
Ramiro Correa-Jaramillo ◽  
Berenice Zúñiga-Torres ◽  
Alonso Zúñiga-Suárez ◽  
Francisco Hernández-Olivares ◽  
Israel Briceño-Tacuri

The calcined clay bricks are the second most used materials in construction that, after the demolition processes, tends to become rubble, generating a negative visual and environmental impact, in addition to the fact that the brick-making process has not been industrialized in Ecuador, for that, its properties are deficient; in this way, the present research aims to study the physical, chemical and mineralogical characteristics of brick waste from the Southern part of ​​this country, for the elaboration of ecological bricks through geopolymerization processes, using as alkaline activator Sodium Hydroxide at temperature ranged between 90 °C and 200 °C, obtaining an optimal mixture at the combination 12.5 M, 26 wt% Cs, 150 °C. The mechanical properties of bricks as simple compression and flexural strength, respectively, applying the experimental Griffith criterion method by finite element simulation method. These ecological bricks obtained are suitable for use in construction.


Author(s):  
M. Sh. Salamanova ◽  
Z. Kh. Ismailova

Objective. Issues related to the search for new, less energy- and material- intensive binders have long been on the agenda of many world environmental forums, since the carbonate technology of Portland cement entails pollution of the surrounding atmosphere and habitat, and the price of this product is unjustifiably growing. In our opinion, alkaline cements could contribute to the construction industry. Within the framework of this work, research results have been obtained that confirm the effectiveness of the development of a clinker-free technology for producing alkaline-mixed binders and composites based on them using aluminosilicate additives, both natural and technogenic origin.Method. The methods of electron microscopy and differential thermal analysis make it possible to study the nature of the components and the processes of formation of the structure of the cement stone. Waste from the cement industry has the appropriate granulometric and chemical composition, the aluminosilicate mineralogy of the studied powders confirms their compliance with the ready-made raw mix of Portland cement clinker, which is the key to the possibility of their effective use.Result. The carried out differential thermal analyzes confirmed the presence of the following phases in the composition of cement stone on binding bonds "cement dust - alkaline activator" of zeolite, calcite, mica type muscovite, montrillonite, magnesium oxide, calcium sulfoaluminates, ettringite structure, calcium hydrochloraluminate, calcium hydrosilicate, calcium hydrosilicate calcium.Conclusion. The obtained regularities of the processes of formation of the structure of the cement binder "waste of the cement industry - Na2SiO3", will transform these developments to create strong and durable artificial building composites competing with concretes on Portland cement.


2021 ◽  
pp. 131198
Author(s):  
L. Soriano ◽  
A. Font ◽  
M.V. Borrachero ◽  
J.M. Monzó ◽  
J. Payá ◽  
...  

2021 ◽  
Vol 921 (1) ◽  
pp. 012009
Author(s):  
P R Rangan ◽  
R Irmawaty ◽  
M W Tjaronge ◽  
A A Amiruddin ◽  
B Bakri ◽  
...  

Abstract This study aims to analyze the effect of curing on the compressive strength of geopolymer mortar made from straw ash, fly ash and laterite soil. This research is experimental in the laboratory. Geopolymer mortar was produced using straw ash, fly ash and laterite soil with a percentage ratio of 16.67: 41.67: 41.67. The alkaline activator used is sodium hydroxide (NaOH) with a concentration of 12 M. The compressive strength test of 5 × 10 cm cylinders is used to evaluate the geopolymer mortar mixture produced at the age of 3, 7 and 28 days with curing, namely air and water curing. The results showed that the compressive strength of the geopolymer mortar increased along with the increasing age of each curing. The compressive strength values produced in air curing 3, 7 and 28 days were respectively 1.64 N/mm2, 1.72 N/mm2 and 3.22 N/mm2. While water curing, the resulting compressive strength values for each curing are 1.03 N/mm2, 1.63 N/mm2 and 1.68 N/mm2. At the ages of 3, 7 and 28 days, there was an increase in the compressive strength values from water curing to air curing, which were 0.37%, 5.23% and 47.82%, respectively. It can be seen that the compressive strength of the geopolymer mortar made from straw ash, fly ash and laterite soil in air curing is greater than that of water curing.


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