scholarly journals Enhancement of Material Properties of Lime-Activated Slag Mortar from Intensified Pozzolanic Reaction and Pore Filling Effect

2018 ◽  
Vol 10 (11) ◽  
pp. 4290 ◽  
Author(s):  
Yang-Hee Kwon ◽  
Sung-Hoon Kang ◽  
Sung-Gul Hong ◽  
Juhyuk Moon
Keyword(s):  
Silica Fume ◽  
Material Properties ◽  
Pozzolanic Reaction ◽  
Physical Effect ◽  
Strength Development ◽  
Pore Filling ◽  
Improvement Strategy ◽  
Microstructural Investigation ◽  
Curing Condition ◽  
Activated Slag

To utilize alkali-activated materials widely, this study investigates the effects of an intensified pozzolanic reaction and pore filling by silica fume on various material properties of lime-activated slag mortar. Although ground-granulated blast-furnace slag is classified as a cementitious material, it commonly requires an activator to enhance the performance of structural materials. In the first step of the improvement strategy, slag reaction is activated by hydrated lime. Next, silica fume is added to densify the microstructure by the physical pore filling effect and/or the pozzolanic reaction that additionally forms hydration products. This increased the compressive strength by 18% at 28 days and by 25% at 91 days under ambient curing condition, mainly due to the physical effect. Moreover, elevated temperature curing for three days was highly effective to further improve the strength, and to accelerate strength development. This is because both the physical effect and the chemical reaction are effective at the high temperature curing condition. The conducted microstructural investigation provided the evidence for the intensified pozzolanic reaction and pore filling effect, both of which are closely related to the mechanical properties. It is also found that the use of silica fume positively contributes to the dimensional stability. Since the developed material exhibits high strength (>40 MPa after 14 days) without Portland cement or highly toxic chemicals, it can be practically used as an eco-friendly structural mortar.

The Pozzolanic Reaction of Silica Fume

2012 ◽  
Vol 1488 ◽  
Author(s):  
Ole M. Jensen
Keyword(s):  
Silica Fume ◽  
High Performance ◽  
Cement Hydration ◽  
Theoretical Calculations ◽  
Pozzolanic Reaction ◽  
Interfacial Transition Zone ◽  
Strength Development ◽  
Micro Structure ◽  
Cementitious Binder ◽  
Portland Cement Hydration

ABSTRACTSilica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone. In the present paper different aspects of the pozzolanic reaction of silica fume are investigated. These include chemical shrinkage, isothermal heat development and strength development. Key data for these are given and compared with theoretical calculations, and based on presented measurements the energy of activation of the pozzolanic reaction of silica fume is estimated. The results show that the pozzolanic reaction of silica fume has notable differences from Portland cement hydration.

scholarly journals Strength Development and Microstructure of Alkali-activated Slag-MgO in Air Curing Condition

2018 ◽  
Vol 186 ◽  
pp. 02003
Author(s):  
Chao-Lung Hwang ◽  
Duy-Hai Vo ◽  
Mitiku Damtie Yehualaw ◽  
Vu-An Tran
Keyword(s):  
Compressive Strength ◽  
Strength Development ◽  
X Ray Diffraction ◽  
Alkali Activated Slag ◽  
X Ray ◽  
Binder Ratio ◽  
Curing Condition ◽  
Activated Slag ◽  
Water To Binder Ratio ◽  
Alkali Activated

The aim of this study is to analysis the effect of MgO on strength development and microstructure of alkali-activated slag (AAS) in air curing condition. Four mixtures of AAS are prepared using different MgO content (0%, 5%, 10%, and 15 % by weight of slag) at water to binder ratio of 0.4. The flow, compressive strength, scanning electron microscopy, and X-ray diffraction are tested under relevant standards. The addition of MgO significantly accelerated the hydration rate of AAS. AAS with adding MgO tended to increase the compressive strength and to reduce the flow. The higher adding MgO content was associated with higher hydrotalcite-like phase (Ht) formation which improved the microstrure of AAS in the air curing condition.

scholarly journals Partial Replacement of Microsilca on Compressive Strength Concrete: Applying Predictive Model

2020 ◽  
Vol 4 (1) ◽  
Keyword(s):  
Silica Fume ◽  
Concrete Strength ◽  
High Surface ◽  
Pozzolanic Reaction ◽  
Influential Factors ◽  
Influential Factor ◽  
Partial Replacement ◽  
Strength Development ◽  
Predictive Values ◽  
Micro Silica

Monitoring the rate of micro-silica variation was carried out to determine different rate of strength developed applying various dosage, these are the pozzolanic reaction which occurs between silica fume and CH producing additional CSH in many of the voids around hydrated cement particles. This is due to high surface area of silica fume that normally affect the mobility of water within concrete segregation, this include bleeding of concrete that are virtually eliminated . This application detailed on the reactions from micro-silica reflection of it are influential factors on rapid increase of concrete strength, these are based on the mixed designed output, such application reflects the significant growth rate of concrete performance in the study, mathematical model application using analytical solution generated derived model for the study, this derived model techniques developed predictive values through simulation, the predictive were applied on the reflection of various water cement ratios including variation of micro-silica dosage numerically to ninety days of curing, water cement ratios influence of strength development were expressed in the study, variation of concrete permeability and void ratios are also detailed as an influential factor in concrete formations, the study has express its significant influence based on the developed strength within seven and ninety days of curing.

Strength Development and Microstructural Investigation of Calcium Carbide Residue and Fly Ash Prepared with Optimized Alternative Green Binders

2021 ◽  
Vol 904 ◽  
pp. 429-434
Author(s):  
Papantasorn Manprom ◽  
Phongthorn Julphunthong ◽  
Pithiwat Tiantong ◽  
Tawat Suriwong
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Raw Materials ◽  
Extended Period ◽  
Calcium Carbide ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Chemical Compositions ◽  
Microstructural Investigation ◽  
Calcium Carbide Residue

The development of new environmentally friendly binder from calcium carbide residue and fly ash wastes were investigated in this study. The key point of this work is difference to several previous investigations in that the optimized mixture proportion of the raw materials were calculated based on their chemical composition and their reaction. The compressive strength development over the curing age was also compared with reference mortar created with OPC binder. Mortar cubes were cast from the mix containing the calcium carbide residue and fly ash, at the optimized ratio. The compressive strength of the mortar was then monitored over an extended period: at 56 days it was 10.66 MPa, which is approximately 47% of the reference mortar. The morphologies and chemical compositions of the developed mortar showed the presence of spherically shaped of unreacted fly ash powder particles embedded in a cement C–S–H gel resulting from the pozzolanic reaction of raw materials.

The Effect of Curing Time on Compressive Strength of Composite Cement Concrete

2012 ◽  
Vol 204-208 ◽  
pp. 4105-4109 ◽  
Author(s):  
Md. Alhaz Uddin ◽  
Mohammed Jameel ◽  
Habibur Rahman Sobuz ◽  
Noor Md. Sadiqul Hasan ◽  
Md. Shahinul Islam ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Cement Content ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Ambient Conditions ◽  
Cement Concrete ◽  
Composite Cement ◽  
Compressive Strength Development ◽  
Curing Condition

The effect of curing condition of five different composition of Portland composite cement (PCC) and ordinary Portland cement (OPC) were investigated in this study. Compressive strength development of five different concrete types has been investigated in terms of cement content and curing duration. From the experimental observation, it is found that the early age strength of concrete made with PCC is lower than that of concrete made with OPC due to the presence of fly ash in PCC which is responsible for the pozzolanic reaction. The continued pozzolanic activity of fly ash contributes to increase strength gain at later ages at continued curing condition. It is also found that drying ambient conditions reduction of the strength potential of concrete made with PCC because the secondary (pozzolanic) reaction fails to contribute to the development of strength.

scholarly journals Heat-Induced Acceleration of Pozzolanic Reaction Under Restrained Conditions and Consequent Structural Modification

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2950
Author(s):  
Nankyoung Lee ◽  
Yeonung Jeong ◽  
Hyunuk Kang ◽  
Juhyuk Moon
Keyword(s):  
High Temperature ◽  
Silica Fume ◽  
High Performance ◽  
Structural Modification ◽  
Cement Hydration ◽  
Mechanical Performance ◽  
High Performance Concrete ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Ultra High Performance Concrete

This study investigated the heat-induced acceleration of cement hydration and pozzolanic reaction focusing on mechanical performance and structural modification at the meso- and micro-scale. The pozzolanic reaction was implemented by substituting 20 wt.% of cement with silica fume, considered the typical dosage of silica fume in ultra-high performance concrete. By actively consuming a limited amount of water and outer-formed portlandite on the unreacted cement grains, it was confirmed that high-temperature curing greatly enhances the pozzolanic reaction when compared with cement hydration under the same environment. The rate of strength development from the dual reactions of cement hydration and pozzolanic reaction was increased. After the high-temperature curing, further strength development was negligible because of the limited space availability and preconsumption of water under a low water-to-cement environment. Since the pozzolanic reaction does not directly require the anhydrous cement, the reaction can be more easily accelerated under restrained conditions because it does not heavily rely on the diffusion of the limited amount of water. Therefore, it significantly increases the mean chain length of the C–S–H, the size of C–S–H globules with a higher surface fractal dimension. This finding will be helpful in understanding the complicated hydration mechanism of high-strength concrete or ultra-high performance concrete, which has a very low water-to-cement ratio.

scholarly journals Mechanical and durability assessment of cement-based and alkali-activated coating mortars in an aggressive marine environment

2021 ◽  
Vol 3 (6) ◽  
Author(s):  
Salar Lashkari ◽  
Farzad Yazdipanah ◽  
Mahyar Shahri ◽  
Prabir Sarker
Keyword(s):  
Silica Fume ◽  
Marine Environment ◽  
Strength Test ◽  
High Rate ◽  
Chloride Diffusion ◽  
Strength Development ◽  
Diffusion Resistance ◽  
Capillary Absorption ◽  
Durability Analysis ◽  
Alkali Activated

AbstractCoatings are used as practical solutions against the intrusion of corrosive ions into concrete structures, particularly, in the harsh marine environment. In the present study, the effectiveness of using cement-based and geopolymer-based coatings produced using by-product materials has been evaluated. Silica fume and GGBFS at their optimum dosages were incorporated into mortar mixtures as a cement replacement, and mixtures of NaOH or KOH and sodium silicate solutions were used in the alkali-activated mortars. Shrinkage test, RCMT, and capillary absorption test as common experiments for durability analysis, as well as tests related to the mechanical and bonding properties including compressive strength test, pull-off test, and shear bonding strength test were carried out on the specimens. According to the results, both geopolymer and cement-based mortars improved the compressive and bonding strengths, and chloride diffusion resistance of coatings compared to the OPC mortar. Silica fume was found to be more effective in the strength development of mortars at young ages, while GGBFS was more responsible for acting as a filler and producing further gel in the older ages. The major drawback with geopolymer mortars is the high rate of water absorption and shrinkage coefficient in the early hours, which shows the importance of curing of these mortars at young ages. Overall, the mix design produced with 30% GGBFS and 7.5% silica fume showed the highest durability and mechanical properties and proved to be more compatible with the harsh environment of the Persian Gulf.

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