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1. Introduction. High-reactivity metakaolin 1 () is a mineral admixture, which is relatively new to the concrete industry that has the potential for improving the durability of concrete. differs from the more commonly used mineral admixtures, such as fly ash and silica fume, in that it is not a by-product; it is manufactured under a carefully controlled process …
Then, the co-toughening mechanism of polyurethane and epoxy resin on the metakaolin-based geopolymer matrix was revealed by analyzing the changes of chemical bonds inside the geopolymer composites before and after modification so as to provide theoretical guidance for the practical engineering applications of geopolymer composites.
In recent years, there has been a growing body of research on the use of metakaolin (MK) in Ultra-High Performance Concrete (UHPC) to address the issue of unstable production yields and quality of industrial by-product Silica fume (SF). However, the current scientific literature tends to focus primarily on performance enhancements, often neglecting to …
The influence of calcium hydroxide content was due to different hydration mechanisms: ... In concrete mixtures, metakaolin replaced either cement or sand in percentages of 10% or 20% by weight of the control cement content. The strength development of metakaolin concrete was evaluated using the efficiency factor (k value).
The contribution of the presence of metakaolin to the strength development is mainly in the late age [26]. A lime-based mortar with 20 % metakaolin was used as a repair mortar for historic adobe buildings. As confirmed by XRD analysis, the metakaolin showed volcanic ash activity by generating monocarbon aluminate C 411.
They are rich in aluminum and silicate, such as metakaolin (MK), fly ash, ... [11, 12], thus benefiting the mechanical properties and durability of the geopolymer concrete [13]. The general mechanism involves various mineral compounds containing silica, aluminum, and calcium in the rock (e.g., basalt) ...
Plain cement concrete, fly ash concrete, and slag concrete with different water/binder (w/ b) ratios (0.35, 0.45, 0.55, and 0.65) were submitted to the accelerated chloride migration test (ACMT ...
Hence, there is an increased need for alternate binder systems with the ability to reduce the effects of chloride attack in concrete. This paper presents a critical review of the engineering properties of metakaolin (MK) based concrete exposed to chloride attack.
The effectiveness of metakaolin on improving setting behavior and strength development of cement aged under laboratory conditions (at a temperature of 20 ± 2 °C and RH of 60 ± 5 %) has been investigated and the operating mechanism also discussed. Metakaolin demonstrated significant effectiveness in ameliorating the impaired properties of ...
Alkali-activated slag (AAS) is an alternative cementitious binder with promising mechanical properties and excellent chemical durability [1], [2].In comparison to ordinary portland cement (OPC), AAS can significantly reduce the environmental impacts of concrete products by lowering 73% greenhouse gas emissions, 43% energy demand and 25% water use due to …
Although the 2.5% metakaolin and 2.5% silica fume mix initially had lower strength than the control mix with 5% fine aggregates, it achieved the highest strength from 28 to 120 …
metakaolin concrete using local materials in the Western Cape province of South Africa, as a means of concrete performance improvement. The study investigated concrete durability properties: penetrability (sorptivity, permeability, conductivity and diffusion), mitigation of Alkali‐Silica Reaction (ASR), and
The CO 2 emission by the cement has created major effects on environment, this resulted a need for replacement of cement in the making of concrete. This study explains the mechanical properties and microstructural analysis of concrete made by partial replacement of cement with the metakaolin (MK) and alccofine (AL) which are mineral admixtures.
This paper presents a critical review of the engineering properties of metakaolin (MK) based concrete exposed to chloride attack. The key advantages and limitations of using MK for concrete ...
Metakaolin affects concrete strength b y three pri mary mechanisms: filler effect, hydration of OPC accelerated, and reaction bet ween MK and CH induced b y pozzolanic reaction. To prepare mortars ...
standing of the metakaolin dissolution mechanisms but also provide insights into the reactivity of calcined clays that are becoming increasingly important to the sustain-ability of the cement and concrete industry. Keywords Metakaolin · Dissolution · Kinetics · Congruency · Reactivity 1 …
Fig.4: Drying Shrinkage of Controlled Concrete and Metakaolin Concrete. Durability of Hardened Concrete Incorporating Highly Reactive Metakaolin Air entrained concrete containing about ten percent of metakaolin by mass supremely withstand ingression of chloride ions and has outstanding durability to repeated cycles of freezing and thawing ...
Metakaolin (MK) is a highly active pozzolanic material and MK is increasingly used in producing high performance concrete. This study presents an integrated hydration-mechanical-durability model for evaluating various …
Request PDF | Dissolution behaviors and mechanisms of metakaolin in acidic activators | Aluminosilicate dissolution is critical for understanding the chemistry of silico-aluminophosphate (SAP ...
1. Introduction. In the construction of marine concrete structure, the substitution of river sand by sea sand and coral sand is conducive to reduce the transporting cost and enhance construction efficiency (Bendixen et al., 2019).However, the free chloride ions introduced from sea sand and coral sand would cause the corrosion of steel bar, ultimately leading to the failure of …
Geopolymer setting is seen to be substantially accelerated by addition of calcium and the objective of this study was to determine the mechanism for this effect by examining metakaolin geopolymers with and without calcium. Solid-state 27 Al NMR tests were used to examine the dissolution extent both qualitatively and quantitatively.
Therefore, this study investigates the chemical degradation mechanism of AAS with various dolomite-to-metakaolin ratios when exposed to Na 2 SO 4, MgSO 4, NaCl and artificial seawater. Powdery AAS binders are used for solution exposure to eliminate the impact of microstructure for ion diffusion and allow a full chemical reaction between AAS and ...
This paper presents a study on investigating the effect of metakaolin (MK) on the hydration, microstructure and volume stability of steam cured high strength concrete (HSC) with a low water to binder ratio (w/b) of 0.25 cured at 80 °C.The structure of C-A-S-H series with a Ca/Si ratio of 1.0 and Al/Si ratio varying from 0 to 0.3 are investigated to discuss the effect of …
The widespread use of reinforced concrete continues to face challenges, particularly in mitigating alkali-silica reaction (ASR), due to its detrimental effects on concrete strength and durability. …
This experimental research investigates the effect of utilizing metakaolin (MK) on the behavior of recycled aggregate concrete (RAC). The RAC incorporates recycled coarse …
The mechanism of this test is presented in Fig. ... Ma ZM, Liang CF, Zhang XX, Abreham AA, Shi JY (2020) Utilization of nano-metakaolin in concrete: a review. J Build Eng 30:101259. Google Scholar Raheem AA, Abdulwahab R, Kareem MA (2021) Incorporation of metakaolin and nano silica in blended cement mortar and concrete—a review. J Clean Prod ...
This study scrutinises the effect of Zn on metakaolin-based geopolymer reaction mechanisms and kinetics, and investigates the incorporation mechanism of Zn in geopolymer gels. Isothermal calorimetry and X-ray diffraction analyses show that substitution of ZnO (20 mol% c.f. metakaolin) significantly hinders reaction, likely due to preferential ...
Use of Metakaolin in concrete accelerates the initial setting time of concrete. 02. It helps in development of the early age strength of concrete which allows the early removal of formwork and thus enhances the production rate. 03. Metakaolin consumes calcium hydroxide thereby preventing the reaction of alkali-silica. Use of Metakaolin ...
Antoni [21] found that metakaolin is essentially amorphous aluminum silicate (Al 2 Si 2 O 7), which can react with calcium hydroxide (Ca (OH) 2) in a conventional …
In this study, we investigated the degradation process of metakaolin-based geopolymers exposed to high temperatures up to 1,000°C. The changes in mechanical properties, microstructure, and phase assemblage of the samples were studied, and the results demonstrated that at high temperatures the activator type [i.e., Na 2 SiO 3 / NaOH (Na/Na) …
Metakaolin demonstrates pozzolanic reaction, reacting with calcium hydroxide to form C-A-S-H. However, its solitary use may lead to issues like excessive water absorption at high dosages. To address this, the study incorporates ground quartz, which moderates metakaolin's activity and boosts concrete performance.
In recent years, there has been a growing body of research on the use of metakaolin (MK) in Ultra-High Performance Concrete (UHPC) to address the issue of unstable …
Dissolution behaviors and mechanisms of metakaolin in acidic activators. Author links open overlay panel Mengxin Bu a, Qingrui Yang a, Penghui Wang a, Biqin Dong a, Dongshuai Hou b ... New insights into strain evolution of concrete under different freeze-thaw conditions: Investigation based on real-time and full-field monitoring. Cement and ...
Table 5 show that the apparent activation energy of Si dissolution in low fineness metakaolin is about 77–90 kJ/mol, while the apparent activation energy of Si dissolution in high fineness metakaolin soil is about 75–85 kJ/mol. Comparing with Al, it can be found that the effect of grinding on the activation energy of Si in metakaolin is ...
In this study, the multi-stage shrinkage characteristics of ultra-high performance concrete (UHPC) was investigated along with the corresponding dominant mechanisms by the aid of simultaneous measurement on shrinkage deformation, relative humidity and hydration heat evolution and ultrasonic pulse velocity (UPV). Major conclusions are as follows.