Frost Resistance of Alkali-Activated Concrete—An Important Pillar of Their Sustainability

Sustainable development of concrete construction requires sustainable materials or sustainable binders. Specifically, alkali-activated materials (AAMs) are an interesting and wide group of materials. They have good strengths and are considered environmentally friendly materials because secondary materials are consumed during the preparation of AAMs. The durability of AAMs is also excellent. One of the most important parts of durability is frost resistance. The frost resistance of alkali-activated materials is usually very good. However, some studies showed opposite properties and poor frost resistance. The reason for this may be a different composition of the activator. The content of alkalis is often considered the main characteristic of alkali-activated materials. However, SiO2 content can play an important role too. This paper discusses the different results for the mechanical properties and frost resistance of different compositions of alkali activators made of sodium water glass with a silicate modulus modified with potassium hydroxide. The role of the activator content and the water-to-cement ratio in this phenomenon is discussed. The results of this article show that the strengths of AAMs are significantly affected by the curing method. Water curing reduced some of the strength of the specimens compared to foil-covered specimens. Frost resistance depends on the method of curing and on the composition of the activator; some concretes with high strengths showed very low frost resistance.

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Development of Cementless Fly Ash Based Alkali-Activated Mortar

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.417-418.721 ◽

2009 ◽

Vol 417-418 ◽

pp. 721-724 ◽

Cited By ~ 1

Author(s):

Kyung Taek Koh ◽

Su Tae Kang ◽

Gum Sung Ryu ◽

Hyun Jin Kang ◽

Jang Hwa Lee

Keyword(s):

Compressive Strength ◽

High Temperature ◽

Fly Ash ◽

High Strength ◽

Molar Ratio ◽

Early Age ◽

Water Curing ◽

Curing Method ◽

Alkali Activated Concrete ◽

Alkali Activated

This study investigates the effects of alkaline activators and curing method on the compressive strength of mortar for the development of cementless alkali-activated concrete using 100% of fly ash as binder. Results reveal that the compressive strength improved according to the increase of the molar concentration of NaOH. In addition, molar ratio Na2O to SiO2 of 1.12 activated the reaction of fly ash with Si and Al constituents and resulted in the most remarkable development of strength. In the case of mortar requiring high strength at early age, higher curing temperatures appeared to be advantages. Curing at 60°C during 48 hours is recommended for requiring high strength at age 28days. Moreover, performing atmospheric curing after high temperature curing appeared to be more effective for the development of strength than water curing. Based on these results, it has been analyzed that alkaline activators fabricated with proportions of 1:1 of 9M NaOH and sodium silicate should be used and that atmospheric curing should be performed after curing at 60°C during 48 hours to produce high strength alkali-activated mortar exhibiting compressive strength of 70MPa at age 28 days.

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Compressive Strength Performance of Alkali Activated Concretes under Different Curing Conditions

Periodica Polytechnica Civil Engineering ◽

10.3311/ppci.17016 ◽

2021 ◽

Author(s):

Anıl Niş ◽

İlhan Altındal

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Strength Performance ◽

Curing Conditions ◽

Standardization Process ◽

Water Curing ◽

Curing Regimes ◽

Alkali Activated Concrete ◽

Alkali Activated ◽

Ambient Curing

This study investigated the influence of different curing conditions on the compressive strength (CS) of the different alkali activated concrete (AAC) specimens at the ages of 2, 28, and 90 days for the structural utilization and standardization process of AAC instead of OPC concrete. For this aim, 100% slag (S100), 75% slag and 25% fly ash (S75FA25), and 50% slag and 50% fly ash based (S50FA50) AAC specimens were produced. Based on the oven-curing (O), water-curing (W), and ambient-curing (A) methods, the influence of 2O for 2 days, 26A2O, 2O26A, 28A, 28W, 26W2O, and 2O26W for 28 days, and 88A2O, 2O88A, 90A, 88W2O, 2O88W, 90W for 90 days on the CS of the AAC were examined in details. In addition, the influence of delayed oven-curing conditions on CS development was also investigated. The results indicated that curing conditions significantly affected on the CS and the water-curing condition could provide a better CS for those of AAC at 90 days. Although, the oven-curing enhanced CS of the S100 specimens at initial ages (first oven-curing applied), delayed oven-curing (oven-curing applied later) was found significant for S75FA25 and S50FA50 specimens. The delayed oven-curing affected more on the CS of the AAC when fly ash content increased. The most of AAC specimens with oven-curing had significantly enhanced the CS at 28 days, but S50FA50 at the age of 90 days decreased. Different curing regimes were proposed for the superior compressive strength values for each AAC specimens at the ages of 28 and 90 days.

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Texture, morphology and strength performance of self-compacting alkali-activated concrete: Role of fly ash as GBFS replacement

Construction and Building Materials ◽

10.1016/j.conbuildmat.2020.121368 ◽

2020 ◽

pp. 121368

Author(s):

Ghasan Fahim Huseien ◽

Abdul Rahman Mohd Sam ◽

Rayed Alyousef

Keyword(s):

Fly Ash ◽

Strength Performance ◽

Alkali Activated Concrete ◽

Alkali Activated

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Sustainable materials and role of professionals in the built environment

WABER 2019 Conference Proceedings ◽

10.33796/waberconference2019.72 ◽

2019 ◽

Keyword(s):

Built Environment ◽

Sustainable Materials

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Assessing the sustainability potential of alkali-activated concrete from electric arc furnace slag using the ECO2 framework

Construction and Building Materials ◽

10.1016/j.conbuildmat.2021.122559 ◽

2021 ◽

Vol 281 ◽

pp. 122559

Author(s):

Hisham Hafez ◽

Dany Kassim ◽

Rawaz Kurda ◽

Rui Vasco Silva ◽

Jorge de Brito

Keyword(s):

Electric Arc Furnace ◽

Electric Arc ◽

Arc Furnace ◽

Electric Arc Furnace Slag ◽

Furnace Slag ◽

Alkali Activated Concrete ◽

Alkali Activated

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Evaluation of Chemical Variability of Cured Vanilla Beans (Vanilla tahitensis and Vanilla planifolia)

Natural Product Communications ◽

10.1177/1934578x0900401016 ◽

2009 ◽

Vol 4 (10) ◽

pp. 1934578X0900401 ◽

Cited By ~ 1

Author(s):

Christel Brunschwig ◽

François Xavier Collard ◽

Jean-Pierre Bianchini ◽

Phila Raharivelomanana

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Dry Matter ◽

Monounsaturated Fatty Acids ◽

Vanilla Planifolia ◽

Chemical Variability ◽

Total Fatty Acids ◽

Curing Method ◽

Fatty Acid Compositions

In order to establish a chemical fingerprint of vanilla diversity, thirty samples of V. planifolia J. W. Moore and V. tahitensis G. Jackson cured beans from seven producing countries were examined for their aroma and fatty acid contents. Both fatty acid and aroma compositions were found to vary between vanilla species and origins. Vanillin was found in higher amounts in V. planifolia (1.7-3.6% of dry matter) than in V. tahitensis (1.0-2.0%), and anisyl compounds were found in lower amounts in V. planifolia (0.05%) than in V. tahitensis (1.4%-2.1%). Ten common and long chain monounsaturated fatty acids (LCFA) were identified and were found to be characteristic of the vanilla origin. LCFA derived from secondary metabolites have discriminating compositions as they reach 5.9% and 15.8% of total fatty acids, respectively in V. tahitensis and V. planifolia. This study highlights the role of the curing method as vanilla cured beans of two different species cultivated in the same country were found to have quite similar fatty acid compositions.

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