Effects of Reactive MgO on the Reaction Process of Geopolymer

Abstract

In order to compensate for the shrinkage of geopolymer pastes uniformly, reactive MgO powders are evenly dispersed in the geopolymer. The deformation performance, mechanical properties, microstructure and components of geopolymer pastes with reactive MgO are characterized. The effects of the content and the activity of MgO are discussed. The results indicate that the chemical shrinkage, autogenous shrinkage and drying shrinkage decrease with the addition of reactive MgO. MgO reacted with water, and fine Mg(OH)2 crystals forms as a geopolymer paste. Mg(OH)2 produces uniform expansion, which refines the pore size of pastes and the compressive strength increases. The shrinkage of the geopolymer pastes is thus effectively compensated.

Effects of Fineness and Chemical Composition of Blast Furnace Slag on Properties of Alkali-Activated Binder

“…An earlier and more extensive heat development corresponded to higher fineness of the slag. Others indicated also that higher Na 2 O concentration could also increase the amount of the developed heat but it cannot be confirmed in the present studies [23,34]. An interesting difference was observed before the development of the main peak.…”

“…The Kb value was calculated as K b = (CaO + MgO)/(SiO 2 + Al 2 O 3 ) and the HM as HM = (CaO + MgO + Al 2 O 3 )/SiO 2 ). The data included values for the three types of slag used in this study and 8 other slags used by others [23,30,40,41]. All slags were activated with liquid sodium silicate SS and had fineness values showed in Table 3.…”

“…Addition of a highly reactive MgO produced by calcination of MgCO 3 at temperatures below 1000 °C to sodium silicate-activated-slag paste accelerated the early stage reaction, reduced the drying shrinkage and increased the carbonation resistance [21,22]. Those effects were related to the formation of C-M-S-H, having more polymerized units, stronger bond strength and better carbonation resistance in comparison with the C-S-H [23]. On the other hand, it also generated a severe cracking under drying condition [21,22].…”

Fresh and Hardened Properties of High Calcium Fly Ash-Based Geopolymer Matrix with High Dosage of Borax

“…This difference in CaO content is indicated from the pH of the two fly ash samples, i.e., FA2 shows higher pH than FA1. Although the MgO content was quite high, the result from Li (Li et al 2019) suggested it could have beneficial effect in reducing the shrinkage.…”

Erratum: Li, Z.; Zhang, W.; Wang, R.; Chen, F.; Jia, X.; Cong, P. Effects of Reactive MgO on the Reaction Process of Geopolymer. Materials 2019, 12, 526

“…The authors wish to revise the authorship and the affiliations, due to the fact that we did not get the permission of the project leader of the Guangdong Water Conservancy Science and Technology Innovation Project (2015-10) in this published paper [1]. The previous authorship and affiliations were shown below:…”