Fundamental Properties of Magnesium Phosphate Cement Mortar for Rapid Repair of Concrete

Joon Woo Park,Ki Yong Ann,Ki Hwan Kim

doi:10.1155/2016/7179403

Joon Woo Park, Ki Yong Ann + Show 1 more

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https://doi.org/10.1155/2016/7179403

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Abstract

Fundamental properties of magnesium phosphate cement (MPC) were investigated in this paper. The setting time and compressive and bond (i.e., flexural and tensile bond) strengths were measured to assess the applicability, and hydration product was detected by the X-ray diffraction. The specimens were manufactured with magnesia and potassium dihydrogen phosphate (K2HPO4) was added to activate hydration process. The Borax (Na2B4O7·10H2O) was used as a retarder to mitigate overwhelming rapid hardening. Mercury intrusion porosimetry was used to examine the pore structure of MPC mortar, and simultaneously rapid chloride penetration test was performed. As a result, the compressive strength of MPC mortar was mostly achieved within 12 hours; in particular, the MPC mortar at 4.0 of M/P ranked the highest value accounting for 30.0 MPa. When it comes to tensile and flexural bond to old substrate in mortar patching, the MPS had the higher tensile and flexural strengths, accounting for 1.9 and 1.7 MPa, respectively, compared to OPC mortar patching. Unlike Portland cement mortar, the MPC mortar contained mainly air void rather than capillary pores in the pore distribution. Presumably due to reduced capillary pore in the MPC, the MPC indicated lower penetrability in the chloride penetration test.

Highlights

Concrete structure may often suffer from an unexpected deterioration in terms of pop-out arising from physical/chemical delamination and corrosion of steel reinforcement
magnesium phosphate cement (MPC) paste specimens were cast for a measurement of X-ray diffraction (XRD) analysis
MPC mortar specimens were cast for a measurement of mechanical properties and pore structures

Summary

Introduction

Concrete structure may often suffer from an unexpected deterioration in terms of pop-out arising from physical/chemical delamination and corrosion of steel reinforcement. A recent study reported that magnesium phosphate cement (MPC) can rapidly harden to gain the strength in a short duration, ranging about several hours to the level of normal strength of ordinary Portland cement concrete [7, 8]. Many researchers have effort on finding other phosphate slat. As a result, they found potassium dihydrogen phosphate (KH2PO4) as a replacement. Further studies on MPC using potassium dihydrogen phosphate showed that it has high bond strength [11, 12] and low drying shrinkage [13]. To verify the feasibility of the MPC as a repair mortar to concrete pavement, the setting time was measured by a monitoring of the penetration resistance to fresh mortar, and simultaneously a development of the strength was evaluated. The pore structure of MPC mortar was examined by mercury intrusion porosimetry to explain the relation between the porosity and mechanical properties and explain the relation between pore distribution and ionic permeability

Experimental Works

Results and Discussion

50 Without borax

Conclusion