FeSO4·H2O协同DTPA改性氯氧镁水泥的作用机理OA

In this study,the effects of ferrous sulfate monohydrate(FeSO4·H2O)and diethylene triamine pentaacetic acid(DTPA)on setting time,mechanical properties,water resistance and microstructure of magnesium oxychloride cement(MOC)were investigated.The mechanism of water resistance improvement of MOC by FeSO4·H2O and DTPA was revealed.FeSO4·H2O and DTPA were added to MOC in different proportion from 0%to 2%(mass fraction).The results show that when 2%FeSO4·H2O and 2%DTPA are added,the performance of MOC is significantly optimized.The initial setting time and final setting time are extended to 339 and 374 min,respectively,which are 120%and 81%higher than those of the control group(without FeSO4·H2O and DTPA).At the same time,the 7 d softening coefficient is increased to 0.9,which is 164%higher than that of the MOC group.The 28 d compressive strength reaches 130 MPa,which is 76%higher than that of the group control,and the porosity is also significantly reduced.This is attributed to the fact that the carboxyl structure of DTPA chelates Mg2+,which provides the active site for Mg2+in the MOC system,so that the 5Mg(OH)2 MgCl2·8H2O(5·1·8 phase)crystals are arranged more closely and the structure is denser.At the same time,the gel-like 5·1·8 phase crystals are formed to fill the micropores between the crystals,thus significantly improving the water resistance of MOC.