Improvement of early-age properties of silico-aluminophosphate geopolymer using dead burnt magnesia

Wang, Yanshuai; Alrefaei, Yazan; Dai, Jian‐Guo

doi:10.1016/j.conbuildmat.2019.05.050

Cited by 32 publications

(15 citation statements)

References 43 publications

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“…This helps distinguish them from other CBPC made of metal oxide whose reaction products are crystallized. However, depending on the synthesis conditions (curing condition or addition of divalent metal oxides), semi-crystalline reaction products including struvite, monetite, brushite, and berlinite can be detected [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Control of the setting reaction and strength development of slag-blended volcanic ash-based phosphate geopolymer with the addition of boric acid

Djobo

2021

J Aust Ceram Soc

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This work aimed to evaluate the role of the addition of blast furnace slag for the formation of reaction products and the strength development of volcanic ash-based phosphate geopolymer. Volcanic ash was replaced by 4 and 6 wt% of ground granulated blast furnace slag to accelerate the reaction kinetics. Then, the influence of boric acid for controlling the setting and kinetics reactions was also evaluated. The results demonstrated that the competition between the dissolution of boric acid and volcanic ash-slag particles is the main process controlling the setting and kinetics reaction. The addition of slag has significantly accelerated the initial and final setting times, whereas the addition of boric acid was beneficial for delaying the setting times. Consequently, it also enhanced the flowability of the paste. The compressive strength increased significantly with the addition of slag, and the optimum replaced rate was 4 wt% which resulted in 28 d strength of 27 MPa. Beyond that percentage, the strength was reduced because of the flash setting of the binder which does not allow a subsequent dissolution of the particles and their precipitation. The binders formed with the addition of slag and/or boric acid are beneficial for the improvement of the water stability of the volcanic ash-based phosphate geopolymer.

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Section: Introductionmentioning

confidence: 99%

Control of the setting reaction and strength development of slag-blended volcanic ash-based phosphate geopolymer with the addition of boric acid

Djobo

2021

J Aust Ceram Soc

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“…Excess free ions will inhibit the dissolution of aluminosilicate and hinder complete geopolymerisation reaction, which has been discussed in the previous paper published [ 27 ]. The slightly acidic aluminum phosphate will also partially neutralize the alkalinity of the geopolymer system [ 28 , 29 ].…”

Section: Resultsmentioning

confidence: 99%

Elevated-Temperature Performance, Combustibility and Fire Propagation Index of Fly Ash-Metakaolin Blend Geopolymers with Addition of Monoaluminium Phosphate (MAP) and Aluminum Dihydrogen Triphosphate (ATP)

et al. 2021

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Thermal performance, combustibility, and fire propagation of fly ash-metakaolin (FA-MK) blended geopolymer with the addition of aluminum triphosphate, ATP (Al(H2PO4)3), and monoaluminium phosphate, MAP (AlPO4) were evaluated in this paper. To prepare the geopolymer mix, fly ash and metakaolin with a ratio of 1:1 were added with ATP and MAP in a range of 0–3% by weight. The fire/heat resistance was evaluated by comparing the residual compressive strengths after the elevated temperature exposure. Besides, combustibility and fire propagation tests were conducted to examine the thermal performance and the applicability of the geopolymers as passive fire protection. Experimental results revealed that the blended geopolymers with 1 wt.% of ATP and MAP exhibited higher compressive strength and denser geopolymer matrix than control geopolymers. The effect of ATP and MAP addition was more obvious in unheated geopolymer and little improvement was observed for geopolymer subjected to elevated temperature. ATP and MAP at 3 wt.% did not help in enhancing the elevated-temperature performance of blended geopolymers. Even so, all blended geopolymers, regardless of the addition of ATP and MAP, were regarded as the noncombustible materials with negligible (0–0.1) fire propagation index.

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“…28 The significant increase in the strength with time is because of the slow dissolution of aluminum and iron with a low pH (<2) along with the slow condensation process between Al 3+ , Fe 2+ /Fe 3+ , and H 2 PO − 4 . 13,29 The latter is attributed to the hardening time of 3 days observed for volcanic ash phosphate geopolymers with Fe/P = 0.50 and 0.54, and 14 days for volcanic ash phosphate geopolymer mix with Fe/P = 0.27. The rate of the consumption of the H 2 PO − 4 species with an increase of reaction time, as shown in FTIR results, also confirms that explanation.…”

Section: Reaction Kinetics Strength Development and Binder Characteri...mentioning

confidence: 97%

“…22,31 The increase in the pH with the reaction time could have fostered that reaction. 29 In addition, the formation of the denser phase consisting of silica-free binder (ferro-aluminophosphate) was observed in volcanic ash phosphate geopolymer with Fe/P = 0.5 and 0.54 (corresponding to a molar ratio of Al/P = 0.93 and 1, respectively). The presence of that phase explains the lowest water absorption and porosity obtained with those samples.…”

Section: Microstructure and Chemistry Of The Bindermentioning

confidence: 98%

Understanding the binder chemistry, microstructure, and physical properties of volcanic ash phosphate geopolymer binder

Djobo

Stephan

2022

J Am Ceram Soc

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This work aims to assess the influence of the chemical composition of the binder resulting from the reaction of phosphoric acid and volcanic ash on its final characteristics. Six initial compositions of volcanic ash phosphate geopolymer with molar ratios Fe/P of 0.27, 0.5, 0.54, 0.81, 1, and 1.5 were designed by adding various dosages of phosphoric acid to volcanic ash. The results show that the hardening time increases with the decrease of molar ratios Fe/P. An excess of phosphoric acid leads to an unstable binder that is partially destroyed with the aging of the binder. The volcanic ash phosphate geopolymer with molar ratios of Fe/P = 0.5-0.54 has the optimum compressive strength (49-53 MPa at 90 days), the lowest water absorption (8.8-9.5 wt.%) as well as porosity (18-19.6 vol.%). The main binder is a porous phase of ferro-silico-aluminophosphate. Secondary phases were also identified in some mixes including ferro-aluminophosphate and magnesium phosphate.

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Improvement of early-age properties of silico-aluminophosphate geopolymer using dead burnt magnesia

Cited by 32 publications

References 43 publications

Control of the setting reaction and strength development of slag-blended volcanic ash-based phosphate geopolymer with the addition of boric acid

Control of the setting reaction and strength development of slag-blended volcanic ash-based phosphate geopolymer with the addition of boric acid

Elevated-Temperature Performance, Combustibility and Fire Propagation Index of Fly Ash-Metakaolin Blend Geopolymers with Addition of Monoaluminium Phosphate (MAP) and Aluminum Dihydrogen Triphosphate (ATP)

Understanding the binder chemistry, microstructure, and physical properties of volcanic ash phosphate geopolymer binder

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