EARLY AGE PROPERTIES OF MAGNESIUM PHOSPHATE-BASED CEMENTS UNDER VARIOUS TEMPERATURE CONDITIONS

Presented in this paper are the effects of temperature on the early age properties of two rapid-hardening magnesium phosphate-based cements and their combinations, as follows: (a) magnesium phosphate cement for cold and regular weather use; (b) magnesium phosphate cement for hot weather use; (c) a 50-50 blend of magnesium phosphate cement and magnesium phosphate cement for hot weather use; and (d) magnesium phosphate cement with the addition of borax. A combination of both mechanical (setting and compressive strength) and physicochemical (X-ray diffraction; optical microscopy and infrared spectroscopy) tests was performed. Overall, 35 mixes were made, cured under various temperature conditions, and tested. The strengths were determined at the ages of 1, 3, and 24 hr. Freeze-thaw experiment was left for future work. The tests revealed that all the above cements develop almost 2,000 psi (14 MPa) compressive strength within an hour regardless of various curing conditions; the 28 days' strengths are more than 4,500 psi (31 MPa); and the 90 days' strengths are more than 6,500 psi (45 MPa) under normal curing conditions. Thus, their applicability for rapid road repair and other concrete repair works seems promising. Further, the MPH cement appears to have the best mechanical properties among them all under the majority of weather conditions.