scholarly journals Long-Term Strength Development of Fly Ash-Based One-Part Alkali-Activated Binders

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4160
Author(s):  
Sani Haruna ◽  
Bashar S. Mohammed ◽  
Mubarak M. A. Wahab ◽  
Mubarak Usman Kankia ◽  
Mugahed Amran ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Water Absorption ◽  
Sodium Metasilicate ◽  
Strength Properties ◽  
Experimental Result ◽  
Term Strength ◽  
Alkali Activated Binders ◽  
Alkali Activated

This research aims to study the effect of the dosage of anhydrous sodium metasilicate activator on the long-term properties of fly ash-based one-part alkali-activated binders (OPAAB) cured at ambient conditions. Powdered sodium metasilicate activator was utilized in the range of 8–16% by weight of the fly ash in producing the OPAAB. The properties examined are hardened density, compressive strength, flexural strength, water absorption, efflorescence formation, and microstructural analysis. The experimental result revealed that the binders exhibited excellent long-term strength properties. The compressive strength of the OPAAP is well correlated with its hardened density. The pastes were found to exhibit good soundness characteristics over the long-term. The absorption of water decreases with an increase in the activator dosage from 8–12%, and beyond that, the water absorption relatively remains the same. Field emission scanning electron microscope (FESEM) micrograph revealed uniformly formed solid matrices with the micro-crack present were observed in the samples. The larger pore size promotes the crystallization of the resulting hydrate substances (N, C)-A-S-H gel. The initial dissolution of the OPAAP occurred within the first 30 min. At longer age of curing, mixtures with a higher dosage of powdered activator tend to absorb less water. Strength properties beyond 28 days are considered as the long-term strength.

Alkali Activated Binders Based on Metakaolin

2015 ◽  
Vol 1 ◽  
pp. 200
Author(s):  
Laura Sele ◽  
Diana Bajare ◽  
Girts Bumanis ◽  
Laura Dembovska
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Water Absorption ◽  
Raw Materials ◽  
Sodium Silicate Solution ◽  
Total Porosity ◽  
Lead Silicate ◽  
Cement Production ◽  
Alkali Activated Binders ◽  
Alkali Activated

<p>According to research conducted in last 25 years, alkali activated binders have been considered as one of the most progressive alternative binders, which can effectively replace Portland cement. Production of alkali activated binders differs from the Portland cement production and is associated with lower CO2 emissions. The use of recycled industrial by-products and wastes is also possible, what corresponds to the future guidelines and principles of sustainable binder production in the world.<br />The aim of this study was to create innovative alkali activated binders by using secondary raw materials, which will be different from the ones described in the scientific literature – alkali activated binders with porous structure. Raw materials used for the binders were metakaolin containing waste, waste from aluminium scrap recycling factory and recycled lead-silicate glass; solid contents were activated with modified sodium silicate solution with an addition of sodium hydroxide.<br />The physical properties of alkali activated binders, such as density, water absorption, open and total porosity, were determined and flexural and compressive strength of hardened alkali-activated binders were tested at the age of 28 days. Durability was examined by sulphate resistance test, which was performed according to SIA 262/1, appendix D: applicability and relevance for use in practice. 40x40x160 mm prismatic specimens were used for expansion measurement and determination of compressive strength. <br />The open porosity of obtained materials was up to 45%, density from 380 to 1720 kg/m3, compressive strength up to 29,8 MPa, water absorption 6 – 114 wt.%. After analysing the results from the sulphate test it was concluded that glass additive reduced the alkali activated binder resistance to sulphate attack.</p>

Theoretical and Experimental Research on Compressive Strength of High Fly-Ash Content Concrete

2011 ◽  
Vol 477 ◽  
pp. 257-262 ◽  
Author(s):  
Hong Mei Ai ◽  
Li Jiu Wang ◽  
Jing Wei ◽  
Jun Ying Bai ◽  
Pu Guang Lu
Keyword(s):  
Growth Rate ◽  
Compressive Strength ◽  
Fly Ash ◽  
Ash Content ◽  
Theoretical Formula ◽  
Term Strength ◽  
Single Factor ◽  
Binder Ratio ◽  
Water Binder Ratio

Introduced the concept of “Cementitious Coefficient” of fly ash, theoretical formula of strength of HFCC at a certain age was found with two variables: actual water-binder ratio and micro-aggregate-binder ratio. Development regularity of compressive strength of HFCC was studied and formula of long-term strength coefficient D28t was settled. Influence of actual water-binder ratio and micro-aggregate-binder ratio on long-term strength of HFCC was analyzed. Experimental results showed that along with the single-factor increase of actual water-binder ratio and micro-aggregate-binder ratio, growth rate of long-term strength of HFCC increased; influence of actual water-binder ratio was deeper than that of micro-aggregate-binder ratio.

scholarly journals Influence of Water Content on Mechanical Strength and Microstructure of Alkali-Activated Fly Ash/GGBFS Mortars Cured at Cold and Polar Regions

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 138 ◽  
Author(s):  
Xiaobin Wei ◽  
Feng Ming ◽  
Dongqing Li ◽  
Lei Chen ◽  
Yuhang Liu
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Water Content ◽  
Negative Temperature ◽  
Polar Regions ◽  
Uniaxial Compression Strength ◽  
Influence Of Water ◽  
Strength And Durability ◽  
Alkali Activated Binders ◽  
Alkali Activated

Negative temperature curing is a very harmful factor for geopolymer mortar or concrete, which will decrease the strength and durability. The water in the geopolymer mixture may be frozen into ice, and the water content is a crucial factor. The purpose of this paper is to explore the influence of water content on the properties of alkali-activated binders mortar cured at −5 °C. Fly ash (FA) and ground granulated blast furnace slag (GGBFS) were used as binders. Three groups of experiments with different water content were carried out. The prepared samples were investigated through uniaxial compression strength test, Scanning electron microscopy (SEM), and X-ray diffraction (XRD) for the determination of their compressive strength, microstructural features, phase, and composition. The results indicated that, the compressive strength of samples basically maintained 25.78 MPa–27.10 MPa at an age of 28 days; for 90 days, the values reached 33.4 MPa–34.04 MPa. The results showed that lower water content is beneficial to improving the early strength of mortar at −5 °C curing condition, while it has little impact on long-term strength. These results may provide references for the design and construction of geopolymer concrete in cold regions.

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.

scholarly journals Correlation between the Compressive, Tensile Strength of Old Concrete under Marine Environment and Prediction of Long-Term Strength

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Weilai Yao ◽  
Shiyong Jiang ◽  
Wei Fei ◽  
Tao Cai
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Marine Environment ◽  
Concrete Strength ◽  
Exponential Model ◽  
Experimental Result ◽  
Term Strength ◽  
Two Parameters ◽  
The Relationship

Compressive strength and tensile strength are important mechanical properties of concrete. The long-term strength of concrete under real service environment is an important parameter when evaluating existing buildings, which should also be properly considered in structural design. In this study, the relationship between compressive and splitting tensile strength of old concrete existing for long period under marine environment was investigated. At a deserted harbour, concrete cores samples were drilled by pairs in site. For each pair of samples, the two cores were drilled from the adjacent location and conducted to compressive, splitting tensile test, respectively. 48 compressive and splitting tensile strengths were finally obtained. From the test results, tensile strength presents general uptrend with compressive strength, and the two parameters are well positively correlated. Exponential model generally recommended by building codes or literatures is still capable of describing the relationship between compressive and tensile strength of old deteriorated concrete, when function parameters are properly determined. Based on statistical theory and the experimental result of this study, a method for predicting long-term tensile strength of concrete is developed and an example is given, which may provide a potential way to estimate long-term concrete strength under real marine environment.

scholarly journals Modification of AA Binder Matrix with the Use of PP Fibres – Strength Investigations

2020 ◽  
Author(s):  
Szymon Dawczyński ◽  
Anna Stokłosa
Keyword(s):  
Fly Ash ◽  
Bending Strength ◽  
Waste Product ◽  
Strength Properties ◽  
Laboratory Research ◽  
Fibre Reinforcement ◽  
Polypropylene Fibres ◽  
Strength Tests ◽  
Alkali Activated Binders ◽  
Alkali Activated

The alkali-activated (AA) binders are assumed to be more ecological than ordinary Portland cement (OPC) binders, because of lower energy requisition and lower CO2 emissions during the production processes. The purpose of using polypropylene(PP) fibres in traditional concrete, geopolymers and mortars is to improve strength properties by inhibiting the growth of cracks that usually occur due to shrinkage, as well as improving the mechanical properties. This paper presents laboratory research into the fibre reinforcement impact on the strength properties of an AA binder made of fly ash suspension. In addition to the suspension, which is a waste product from the coal power plant, recycled ground glass and metakaolin were used as the precursors. The chemical activator of the geopolimerisation reaction was prepared using sodium hydroxide and sodium silicate. Five different sets of the prism samples 40x40x160 mm were made (with different PP fibres ratio,  from 0% to 2%  by weight) and then the flexural and compressive strength tests were performed.  The addition of polypropylene fibres increased the bending strength, which produced the beneficial effect of reducing crack propagation in cases of tensile stress occurrence. Keywords: alkali-activated binders, geopolymers, polypropylene fibres, fly ash suspension, bending strength

scholarly journals Strength, Shrinkage and Early Age Characteristics of One-Part Alkali-Activated Binders with High-Calcium Industrial Wastes, Solid Reagents and Fibers

2021 ◽  
Vol 5 (12) ◽  
pp. 315
Author(s):  
Dhruv Sood ◽  
Khandaker M. A. Hossain
Keyword(s):  
Fly Ash ◽  
Sodium Metasilicate ◽  
Cementitious Materials ◽  
Industrial Wastes ◽  
Supplementary Cementitious Materials ◽  
Powder Form ◽  
High Calcium ◽  
Dry Mixing ◽  
Alkali Activated Binders ◽  
Alkali Activated

Alkali-activated binders (AABs) are developed using a dry mixing method under ambient curing incorporating powder-form reagents/activators and industrial waste-based supplementary cementitious materials (SCMs) as precursors. The effects of binary and ternary combinations/proportions of SCMs, two types of powder-form reagents, fundamental chemical ratios (SiO2/Al2O3, Na2O/SiO2, CaO/SiO2, and Na2O/Al2O3), and incorporation of polyvinyl alcohol (PVA) fibers on fresh state and hardened characteristics of 16 AABs were investigated to assess their performance for finding suitable mix compositions. The mix composed of ternary SCM combination (25% fly-ash class C, 35% fly-ash class F, and 40% ground granulated blast furnace slag) with multi-component reagent combination (calcium hydroxide and sodium metasilicate = 1:2.5) was found to be the most optimum binder considering all properties with a 56 day compressive strength of 54 MPa. The addition of 2% v/v PVA fibers to binder compositions did not significantly impact the compressive strengths. However, it facilitated mitigating shrinkage/expansion strains through micro-confinement in both binary and ternary binders. This research bolsters the feasibility of producing ambient cured powder-based cement-free binders and fiber-reinforced, strain-hardening composites incorporating binary/ternary combinations of SCMs with desired fresh and hardened properties.

Strength Properties of Sludge Solidified with Fly Coal Ash and Portland Cement

2011 ◽  
Vol 378-379 ◽  
pp. 439-442
Author(s):  
Tomáš Daněk ◽  
Jan Thomas ◽  
Jiří Mališ ◽  
Jan Jelínek
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Portland Cement ◽  
Uniaxial Compressive Strength ◽  
Coal Fly Ash ◽  
Coal Ash ◽  
Strength Properties ◽  
Mixture Composition ◽  
Metallurgical Production

The paper deals with the properties of mixtures on the base of fly ash and sludge from the metallurgical production. The mixture composition of this group is grounded in the knowledge acquired during testing of various mixtures. The mixtures of sludge and coal fly ash and/or cement after of curing were used for tests. The uniaxial compressive strength of solidified sludge was examined. To understand the behaviour of mixtures in the long term, the prepared mixtures were tested after 14, 28, 56 and 120 days.

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