scholarly journals Micropore Structures in Cenosphere-Containing Cementitious Materials Using Micro-CT

2017 ◽  
Vol 2017 ◽  
pp. 1-10
Author(s):  
Seyoon Yoon ◽  
Inhwan Park
Keyword(s):  
Fly Ash ◽  
Pore Volume ◽  
Elastic Moduli ◽  
Cementitious Materials ◽  
Matrix Composites ◽  
Micro Ct ◽  
Principal Moment ◽  
The Moment ◽  
Portland Cement Paste ◽  
Alkali Activated

Cenospheres have been recently applied to increase the volume of uniform micropores in hardened cementitious materials. Therefore, application of micro-CT to cenosphere-containing binders will help better understand the micropores formed by cenospheres in the hardened materials. Accordingly, the present study prepared Portland cement paste, alkali-activated fly ash/silica fume, and alkali-activated fly ash with 60% weight replacement by cenospheres and reconstructed their micropore structures using micro-CT. From the pore structure, individual micropores were extracted and analyzed using the principal moment ratios (I11/I33 and I22/I33). Based on the moment ratios, the representative pore shapes were determined in the different pore-volume ranges. Four-factor pore compliance contribution (4-factor PCC) model was then applied to predict the influences of the micropores on the elastic moduli of the micropore/matrix composites.

Mechanical Characteristics Analysis of Alkali-Activated Fly Ash Cementitious Materials

2010 ◽  
Vol 452-453 ◽  
pp. 721-724
Author(s):  
Gum Sung Ryu ◽  
Hyun Jin Kang ◽  
Su Tae Kang ◽  
Gyung Taek Koh ◽  
Jang Hwa Lee
Keyword(s):  
Fly Ash ◽  
Mechanical Characteristics ◽  
High Strength ◽  
Cementitious Materials ◽  
Molar Concentration ◽  
Basic Study ◽  
Co2 Gas ◽  
Characteristics Analysis ◽  
Alkali Activated Concrete ◽  
Alkali Activated

Recently, research on alkali-activated concrete that does not use cement as binder has been actively conducted. This alkali-activated concrete is a cement zero concrete which, instead of cement, is activated by alkali solution using fly ash known to be rich of Si and Al and enables to reduce effectively the emission of CO2 gas. This paper presents a basic study for the manufacture of cementless concrete using 100% of fly ash. To that goal, the mechanical characteristics of cementless concrete is evaluated according to the age and the variation of the molar concentration of the alkali activator with focus on the identification of the reaction mechanism. The experimental results show that larger molar concentration elutes larger quantities of Si4+ and Al3+. Specifically, approximately twice larger quantities of Si4+ and Al3+ were eluted for molar concentrations of 9M and 12M than 6M. The formation of gel at the surface of fly ash appeared to be caused by the stronger activation of fly ash in higher alkali environment. The resulting compressive strengths per age indicated that the strength of concrete could be controlled according to the molar concentration of NaOH. Moreover, results also demonstrated that a molar concentration of 9M for NaOH seems to be appropriate to secure a strength superior to 40MPa as the reference for high strength concrete in ordinary concrete.

scholarly journals Resistance to Chemical Attack of Hybrid Fly Ash-Based Alkali-Activated Concretes

Molecules ◽  
2020 ◽  
Vol 25 (15) ◽  
pp. 3389
Author(s):  
William G. Valencia-Saavedra ◽  
Ruby Mejía de Gutiérrez
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Strength Loss ◽  
Cementitious Materials ◽  
Sodium Sulphate ◽  
Unburned Carbon ◽  
Chloride Permeability ◽  
Chemical Attack ◽  
Concrete Production ◽  
Alkali Activated

The environmental impacts related to Portland cement production in terms of energy consumption, the massive use of natural resources and CO2 emissions have led to the search for alternative cementitious materials. Among these materials, alkali-activated cements based on fly ash (FA) have been considered for concrete production with greater sustainability. In the present article, the chemical durability properties (resistance to sulphates, chloride permeability, and resistance to carbonation) of a hybrid alkali-activated concrete based on fly ash–ordinary Portland cement (FA/OPC) with proportions of 80%/20% were evaluated. It is noted that the FA was a low-quality pozzolan with a high unburned carbon content (20.67%). The results indicated that FA/OPC concrete had good durability with respect to the OPC concrete, with 95% less expansion in the presence of sodium sulphate and a 2% strength loss at 1100 days, compared with the 56% strength loss of the OPC concrete. In addition, FA/OPC showed lower chloride permeability. On the contrary, the FA/OPC was more susceptible to carbonation. However, the residual compressive strength was 23 MPa at 360 days of CO2 exposure. Based on the results, FA/OPC, using this type of FA, can be used as a replacement for OPC in the presence of these aggressive agents in the service environment.

Application on cementitious materials to promote durability of alkali-activated concrete containing co-fired fly ash and water-quenched slag

2017 ◽  
Vol 148 (7) ◽  
pp. 1349-1354 ◽  
Author(s):  
Che-Hung Sung ◽  
Ran Huang ◽  
Chia-Jung Tsai ◽  
Yann-Hwang Wu ◽  
Wei-Ting Lin ◽  
...  
Keyword(s):  
Fly Ash ◽  
Cementitious Materials ◽  
Alkali Activated Concrete ◽  
Alkali Activated

Durability of alkali-activated fly ash cementitious materials

2006 ◽  
Vol 42 (9) ◽  
pp. 3055-3065 ◽  
Author(s):  
A. Fernandez-Jimenez ◽  
I. García-Lodeiro ◽  
A. Palomo
Keyword(s):  
Fly Ash ◽  
Cementitious Materials ◽  
Alkali Activated

scholarly journals Mechanical properties of fly ash and blast furnace slag based alkali activated concrete using high silica modulus activator

2021 ◽  
Vol 309 ◽  
pp. 01202
Author(s):  
G.V.V. Satyanarayana ◽  
Kaparaboina Greeshma
Keyword(s):  
Blast Furnace ◽  
Fly Ash ◽  
Blast Furnace Slag ◽  
Setting Time ◽  
High Strength ◽  
Cementitious Materials ◽  
Split Tensile Strength ◽  
High Silica ◽  
Furnace Slag ◽  
Alkali Activated

The alternative to cement is grabbing attention of inventors due to the numerous advantages with their usage. Fly Ash (FA) and Blast furnace slag (BFS) are abundantly available in bi product form. There is heavy problem in disposal and land availability for industries. So many studies are going on to reduce these problems by usage as cementitious materials in concrete adding advantages towards green concrete. It is developed that Alkali activated flyash concrete has high strength, high acid resistance and heat resistance where as Alkali activated slag concrete has rapid setting time, high strength, impermeable and improved fire resistance. In this study FA and BFS are activated with high silica modulus activator with different activator/binder ratios and binder contents. The alkali activated FA-BFS concrete is verified for workability, compressive strength, split tensile strength, and flexural strength.

scholarly journals Investigation on alkali activated fly ash and slag concrete using neutral grade water glass as activator

2021 ◽  
Vol 309 ◽  
pp. 01195
Author(s):  
G.V.V. Satyanarayana ◽  
Kaparaboina Greeshma
Keyword(s):  
Fly Ash ◽  
Construction Industry ◽  
Raw Materials ◽  
Sodium Silicate Solution ◽  
Silicate Solution ◽  
Cementitious Materials ◽  
Polymer Concrete ◽  
Portland Cement Concrete ◽  
Lime Stone ◽  
Alkali Activated

The utilization of cement in concrete was an ancient method as well the utilization of cementitious materials in concrete not only improves mechanical properties but also improves workability and durability etc., Today urbanization expands in many folds, so that the usage of cement became more due to this the production of cement increases. The production of cement on one hand affects the environment in form of Carbon dioxide gases on other hand depreciation of raw materials like lime stone and sand etc. Globally many construction industry and researches focussed in reduction of cement content in concrete by production of new alternatives like Geo polymer concrete etc. In this investigation Alkali-Activated Fly Ash slag concrete (AAFSC) is introduced as an alternative for ordinary Portland cement concrete (OPCC). Researchers developed AAFSC with NaOH and Na2SiO3 as activators. In this study AAFSC produced is with neutral grade sodium silicate solution with silica modulus 2.9 (Ms).For production of AAFSC the quantity of binder content is 500kg/m3 by varying binders proportions like Fly Ash and GGBS along with solution/binder ratios varying from 0.6 to 0.7. During this experimental investigation the workability and compressive strength of AAFSC is tested.

scholarly journals New Cementitious Materials Based on Alkali-Activated Fly Ash: Performance at High Temperatures

2008 ◽  
Vol 91 (10) ◽  
pp. 3308-3314 ◽  
Author(s):  
Ana Fernández-Jiménez ◽  
Angel Palomo ◽  
José Y. Pastor ◽  
Antonia Martín
Keyword(s):  
Fly Ash ◽  
High Temperatures ◽  
Cementitious Materials ◽  
Alkali Activated
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