Mechanical property and microstructure of quaternary phase paste blended with metakaolin

Microstructure Evolution Mechanism of Quaternary Phase Paste Containing Metakaolin and Silica Fume

“…In comparison, no significant changes in CAH 10 peaks are found, indicating that the stability of CAH 10 under the studied conditions is better than that of C 2 AH 8 . It was reported that the rate of conversion of CAH 10 into C 3 AH 6 is much lower than that of C 2 AH 8 . − However, CAH 10 is absent when the age is further increased to 28 d. Meanwhile, the major C 2 ASH 8 peaks and moderate C 3 AH 6 peaks are observed, and there is no significant difference concerning Q phase peaks between 7 and 28 d. Therefore, from the change of peak intensity of CAH 10 , C 2 AH 8 , C 2 ASH 8 , C 3 AH 6 , and Q phase with age, it can be deduced that C 2 ASH 8 is formed by the reactions of dissolved silica from SF with metastable hydrates, rather than by the reactions between the dissolved silica and calcium aluminates. Furthermore, CAH 10 reacts with the dissolved silica to form C 2 ASH 8 more efficiently than C 2 AH 8 , although they also convert into C 3 AH 6 at the same time.…”

“…The Ca/Al and Si/Al ratios of the IP formed in both pastes (spots 3 and 4) are similar to those reported in the Q phase paste without any addition. 30 This indicates that the presence of SF or MK does not affect the composition of IP. The Si/Al ratio of IP is about 0.2, which is significantly lower than that of C 2 ASH 8 (Si/Al ratio = 0.5), suggesting the absence of C 2 ASH 8 in IP.…”

“…In manual thresholding, the threshold value is determined when the segmented pixels correspond satisfactorily to the features of interest in the original image. Figure 2 shows an example of the original BSE image and Q phase paste exhibits good strength gain at ambient temperature, 30 but it suffers from significant strength reduction when cured at 40 °C. With the addition of SF, the strength of the blended pastes still decreases with time, but incorporating 15% SF partially mitigates the strength loss.…”

“…Metakaolin (MK) is a type of aluminosilicate SCM. Its silica mainly presented as Q 4 is the same as that presented in SF, representing the high polymerization of SiO 4 tetrahedra. , While the alumina in MK exists in the form of Al IV , Al V , and Al VI , which has higher reactivity than that contained in FA (mainly Al VI ). , Q phase paste containing 15% MK exhibits excellent mechanical properties, and incorporating MK enhances the stability of CAH 10 , rather than forming C 2 ASH 8 , which is mainly related to the dissolution of alumina in MK . MK has great potential to inhibit the conversion reactions, but there are only a few studies about the MK-blended CAC. ,, Additionally, the mechanism of MK inhibiting the conversion is different from that of the siliceous SCMs such as SF.…”

“…34,35 Q phase paste containing 15% MK exhibits excellent mechanical properties, and incorporating MK enhances the stability of CAH 10 , rather than forming C 2 ASH 8 , which is mainly related to the dissolution of alumina in MK. 30 MK has great potential to inhibit the conversion reactions, but there are only a few studies about the MK-blended CAC. 28,36,37 Additionally, the mechanism of MK inhibiting the conversion is different from that of the siliceous SCMs such as SF.…”