scholarly journals Structural and microscopy characterization of an alternative low-energy binder containing Ca(OH)2 as an alkaline activator

2021 ◽  
Vol 3 (6 (111)) ◽  
pp. 71-79
Author(s):  
Aditianto Ramelan ◽  
Adhi Setyo Nugroho ◽  
Teti Indriati ◽  
Riska Rachmantyo
Keyword(s):  
Portland Cement ◽  
Water Immersion ◽  
Pozzolanic Reaction ◽  
Low Energy ◽  
Hydration Products ◽  
Amorphous Phases ◽  
Average Maximum ◽  
Hydrated Products ◽  
Pozzolanic Materials

The development of potential alternative binders to Portland cement is still becoming a global challenge in housing and infrastructure aspects. That is because cement and concrete become the major materials needed in building constructions. The Ordinary Portland cement can form a solid and hard mass when mixed with water with a certain ratio. This is due to the formation of ettringite and calcium silicate hydrate (CSH) phases that contribute to the strength of the hydrated products about 33–53 MPa. However, the manufacturing temperature of Portland cement can reach up to 1,500 °C in producing clinker. In order to lower the energy consumption and production cost, scientists were trying to utilize pozzolanic materials. The research of pozzolanic materials as alkali-activated cement, such as soil cement or geopolymer cement, is also still conducted. Hence, a better understanding of pozzolanic reaction and its hydration products is needed. In this work, the hydration products of low-energy binders composed of Ca(OH)2-SiO2 and Ca(OH)2-metakaolin-gypsum mixtures were studied. The hydrated products of 41 wt. % Ca(OH)2 – 41 wt. % metakaolin – 18 wt. % gypsum mixtures followed by water immersion curing at 50 °C for 28 days undergone a pozzolanic reaction. XRD characterization showed that the hydrated product is mainly composed of ettringite (60.0 %) and crystalline-CSH (23.4 %). The diffractograms obtained have shown a specific hump indicating the presence of amorphous phases besides the crystalline. To confirm the presence of the non-crystalline or amorphous phases of the hydrated products, a polarizing optical microscope (OM) using a crossed Nicols method was used. The characterization of the phases is the novelty of the present research. The ettringite, crystalline CSH and the amorphous phases act as a strong binder that consequently contribute to its average maximum compressive strength of 22.17 MPa.

Prediction of the Carbonation Depth of Concrete with a Mortar Finish

2008 ◽  
Vol 385-387 ◽  
pp. 633-636 ◽  
Author(s):  
Han Seung Lee ◽  
Xiao Yong Wang
Keyword(s):  
Portland Cement ◽  
Numerical Procedure ◽  
Pozzolanic Reaction ◽  
Surface Coatings ◽  
Reinforced Concrete Structures ◽  
Hydration Products ◽  
Application Time ◽  
Carbonation Depth ◽  
Hydration Model ◽  
Corrosion Of Steel

It is well known that carbonation will result corrosion of steel reinforcement in reinforced concrete structures. To reduce the rate of carbonation, the surface coatings, such as mortar finish, has been used widely to concrete. This paper presents a numerical procedure about carbonation of the coating-concrete system. This numerical procedure starts with a multi-component hydration model. By hydration model which considers both and Portland cement and pozzolanic reaction, the amount of hydration products which are susceptible to carbonate as well as porosity is obtained as function of age. Furthermore, the diffusivity of CO2 is determined and carbonation depth of concrete is predicted. Parameter studies are performed to show the influence of composition and application time of mortar finish on carbonation depth of substrate concrete.

Characterization of fly ash reactivity in hydrating cement by neutron scattering

2009 ◽  
Vol 24 (7) ◽  
pp. 2435-2448 ◽  
Author(s):  
Walairat Bumrongjaroen ◽  
Richard A. Livingston ◽  
Dan A. Neumann ◽  
Andrew J. Allen
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Pozzolanic Reaction ◽  
Effective Density ◽  
Partial Replacement ◽  
Cement Pastes

Partial replacement of hydrating Portland cement by fly ash produces competing effects: it contributes calcium hydrate silicate (C-S-H) gel through the pozzolanic and alkali-activated reactions but dilutes the contribution of the main Portland cement reaction. To investigate this, two neutron-scattering methods were applied to density-fractionated lignite-type and bituminous-type fly ash/Portland cement pastes (20% by mass replacement). Small-angle neutron scattering (SANS) measured the effect of the fly ash on the fractal C-S-H microstructure, whereas inelastic neutron scattering (INS) measured the pozzolanic reaction in terms of calcium hydroxide (CH) consumption. The CH consumption increased with the effective density fraction, and the fractal microstructure evolved more slowly for all fly ash mixes compared with the pure cement control. However, gel volume measured by SANS showed no correlation with the CH consumption measured by INS. The implications of these results are discussed.

Microstructure and Characterizations of Portland-Bottom Ash-Silica Fume Cement Pastes

2008 ◽  
Vol 55-57 ◽  
pp. 629-632 ◽  
Author(s):  
W. Wongkeo ◽  
W. Thawornson ◽  
Arnon Chaipanich
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Silica Fume ◽  
Power Plants ◽  
Thermal Power ◽  
Bottom Ash ◽  
Pozzolanic Reaction ◽  
Cement Particle ◽  
Cement Pastes

This research investigated the microstructure and characterization of Portland-bottom ash-silica fume cement pastes. Bottom ash, a by – product from coal-fired thermal power plants, was obtained from Mae Moh power plant, Lampang, Thailand. It currently exists as waste approximately 1.5 MT per year and has not been put to use. Unlike its counterpart, fly ash, which is recognized as an alternative material used to replace part of Portland cement. Silica fume, a nanomaterial from ferrosilicon industry, is nanoparticle and highly amorphous. It is highly pozzolanic reaction and could improve properties of Portland-bottom ash cement pastes. Thus, this research investigated the effect of silica fume on microstructure and characterization of Portland-bottom ash-silica fume cement pastes. The ratios of bottom ash used to replace Portland cement were 0, 10, 20 and 30 percent by weight and silica fume was added at 5 and 10 percent by weight. Compressive strength test was then carried out. SEM and TGA were used to study the microstructure of Portland-bottom ash-silica fume cement pastes. The results show that, the compressive strength of Portland-Bottom ash-silica fume cement pastes increased with added silica fume at 5 and 10 percent. SEM micrographs show C-S-H gel and silica fume around the cement particle in Portland-bottom ash-silica fume cement pastes which gives a highly dense and less porous microstructure. TGA graphs show Ca(OH)2 decreased with silica fume content.

Mechanism of Cement Paste with Different Particle Sizes of Bottom Ash as Partial Replacement in Portland Cement

2017 ◽  
Vol 68 (10) ◽  
pp. 2367-2372 ◽  
Author(s):  
Ng Hooi Jun ◽  
Mirabela Georgiana Minciuna ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Tan Soo Jin ◽  
Andrei Victor Sandu ◽  
...  
Keyword(s):  
Portland Cement ◽  
Construction Material ◽  
Bottom Ash ◽  
High Volume ◽  
Cement Composite ◽  
Pozzolanic Reaction ◽  
High Specific Surface Area ◽  
Partial Replacement ◽  
Natural Aggregates ◽  
Pozzolanic Properties

Manufacturing of Portland cement consists of high volume of natural aggregates which depleted rapidly in today construction field. New substitutable material such as bottom ash replace and target for comparable properties with hydraulic or pozzolanic properties as Portland cement. This study investigates the replacement of different sizes of bottom ash into Portland cement by reducing the content of Portland cement and examined the mechanism between bottom ash (BA) and Portland cement. A cement composite developed by 10% replacement with 1, 7, 14, and 28 days of curing and exhibited excellent mechanical strength on day 28 (34.23 MPa) with 63 mm BA. The porous structure of BA results in lower density as the fineness particles size contains high specific surface area and consume high quantity of water. The morphology, mineralogical, and ternary phase analysis showed that pozzolanic reaction of bottom ash does not alter but complements and integrates the cement hydration process which facilitate effectively the potential of bottom ash to act as construction material.

scholarly journals Characterization of nitrogen species incorporated into graphite using low energy nitrogen ion sputtering

2016 ◽  
Vol 18 (1) ◽  
pp. 458-465 ◽  
Author(s):  
Hisao Kiuchi ◽  
Takahiro Kondo ◽  
Masataka Sakurai ◽  
Donghui Guo ◽  
Junji Nakamura ◽  
...  
Keyword(s):  
Low Energy ◽  
Nitrogen Species ◽  
Ion Sputtering ◽  
Zigzag Edge ◽  
Nitrogen Doped ◽  
Doping Mechanism ◽  
Nitrogen Ions ◽  
Nitrogen Ion

The well-controlled nitrogen doped graphite with graphitic nitrogen located in the zigzag edge and/or vacancy sites can be realized using the low energy nitrogen sputtering. The doping mechanism of nitrogen ions is also discussed.

scholarly journals Characterization of low-energy magnetic excitations in chromium

2004 ◽  
Vol 70 (14) ◽  
Author(s):  
H. Hiraka ◽  
P. Böni ◽  
K. Yamada ◽  
S. Park ◽  
S-. H. Lee ◽  
...  
Keyword(s):  
Low Energy ◽  
Magnetic Excitations
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