The pore structure and hydration performance of sulphoaluminate MDF cement

Abstract

The hydration and pore structure of sulphoaluminate MDF cement were studied by X-ray diffractometer (XRD), scanning electron microscope (SEM) and mercury intrusion porosimeter (MIP) etc. The experimental results indicate that hydration products of the materials are entringites (AFt), aluminium hydroxide and CSH (I) gel etc. Due to its very low water-cement ratio, hydration function is only confined to the surfaces of cement grains, and there is a lot of sulphoaluminate cement in the hardenite which is unhydrated yet. Hydration reaction was rapidly carried under the condition of the heat-pressing. Therefore cement hydrates AFt, CSH (I) and aluminium hydroxide gel fill in pores. The expansibility of AFt makes the porosity of MDF cement lower (less than 1 percent) and the size of pore smaller (80 percent pore was less than 250A), and enhances its strength.