Influence of Polyaluminum Chloride Residue on the Strength and Microstructure of Cement-Based Materials

Abstract

In this paper, cement and dechlorinated Polyaluminum Chloride Residue (PACR) have been used to prepare a net slurry and mortar specimens. Two hydration activity indicators have been used to quantitatively analyze the dechlorinated PACR hydration activity. In particular, the effect of dechlorinated PACR content on the compressive strength of mortar has been assessed by means of compressive strength tests. Moreover, X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been employed to observe the microstructure of the considered hydration products. The following results have been obtained. The 28th day activity index of the dechlorinated PACR is 75%, and therefore it meets the criterion for the use of active admixture. The increase in the content of the dechlorinated PACR tends to reduce the compressive strength of mortar specimens, however, it is beneficial to its later strength growth. When the content is not greater than 10%, the strength remains unchanged, otherwise, it decreases. The PACR does not form a new crystalline phase in the cement slurry, and the dechlorinated PACR remains active until the age of the 28th day. The inclusion of the PACR mainly deteriorates the early strength of the cement slurry, but it promotes the production of hydration products in the cement slurry after the 7th day.