|Table of Contents|

Strength mechanism of cement cementitious hardening products affected by coal gasification slag or fly(PDF)

长安大学学报（自然科学版）[ISSN:1006-6977/CN:61-1281/TN]

Issue:
2023年2期
Page:
26-34
Research Field:
道路工程
Publishing date:

Info

Title:
Strength mechanism of cement cementitious hardening products affected by coal gasification slag or fly
Author(s):
XIE Hai-wei1; 2;  PAN Fu-yuan2;  LIU Zun-qing2;  LI Zu-zhong3;  LIU Xi-xi2
(1. School of Traffic & Transportation Engineering, Changsha University of Science & Technology,Changsha 410114, Hunan, China; 2. School of Transportation and Logistics Engineering, XinjiangAgricultural University, Urumqi 830052, Xinjiang, China; 3. School of Materials Science and Engineering, Chang’an University, Xi’an 710064, Shaanxi, China)
Keywords:
road engineering;  cementitious mechanism;  microstructure and phase composition;  coal gasification slag or fly;  mortar strength
PACS:
U414
DOI:
10.19721/j.cnki.1671-8879.2023.02.003
Abstract:
In order to explore the feasibility of coal gasification slags as cement admixture, the strength mechanism of cement cementitious hardening products affected by coal gasification slags was studied. The differences of the formation processes between coal gasification slags or fly were analyzed by comparison with each other. The microstructure and phase composition of coal gasification slags, fly ash and their cement cementitious products were studied by scanning electron microscope, energy dispersive spectrometer and X-ray diffraction test. Cement mortar specimens with coal gasification slags or fly under different dosages were prepared respectively, and the mechanical strength values of cement mortars at different ages were tested. The results show that the distinct formation processes of fly ash and coal gasification slags lead to their great differences in micro-morphology and material compositions. Their ignition loss can be sorted from large to small as fine coal gasification slag, coarse coal gasification slag, fly ash, and the residual carbon content of fine slag is much higher than that of coarse slag and fly ash. Coal gasification coarse slag appears mainly in lamellar and massive structure. The fine slag possesses mostly honeycomb flocs with a small number of spherical particles. Fly ash presents mostly in spherical structures. There are similar in their elemental compositions, including aluminosilicate minerals with pozzolanic activity. The ettringite formed in the coarse slag slurry is thick needle-like and interwoven into reticular structure, while it is fine needle-like and well distributed around the C-S-H gel in fly ash slurry. No obvious ettringite phase is found in fine slag slurry. The amount of the Ca(OH)2 from cement hydration, consumed by the coarse slag is greater than that by fly ash. The active mineral phase in the fine slag is surrounded by residual carbon, so the pozzolanic activity cannot be released, and the residual carbon also affects the hydration process of cement. The 7 d strength of cement mortar mixed with fly ash or coal gasification slags is lower than that of reference cement mortar. The compressive strength of cement mortar mixed with fly ash is higher than that of reference mortar at 28 d. The compressive strength of cement mortar mixed with coarse slag is equal to that of reference mortar, while the strength of cement mortar mixed with fine slag is much lower than that of reference mortar. Coarse slag can be used as cement admixture in place of 5%(mass fraction, the same below)cement, but fine slag is inappropriate used as cement admixture directly. The research results can provide an important reference for comprehensive development and utilization of coal gasification slags.5 tabs, 7 figs, 29 refs.

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Last Update: 2023-03-30