Study On Preparation Of Double Component MPC Fast Repair Material Under Negative Temperature

Magnesium Phosphate Cement.MPC is a new kind of cementing material,which can form hard stone by acid-base reaction and physical action after adding water at room temperature,but the winter temperature is relatively low in northern China.The mixing water added in the preparation of MPC will freeze and the pavement in the process of MPC construction will be in a negative temperature state.Therefore,a kind of antifreeze(ethylene glycol)is used to reduce the freezing point of mixing water,so that the mixing water added in the preparation of MPC under negative temperature will not freeze.Thus smooth system MPC road repair materials are available and can be continuously hydrated during construction.The specific contents of the study are as follows:(1)preparation of basic MPC cement.Firstly,the optimum admixture of magnesium oxide and ammonium dihydrogen phosphate for the preparation of MPC was determined by comparing the experimental results.Then different borax content was designed.The ratio of water to cement and the ratio of ammonium dihydrogen phosphate to magnesium oxide were used to prepare MPC material.The fluidity,fluidity loss,setting time and strength of each age were measured and the results were compared.The optimum proportion of MPC cement was determined by analysis.(1)simulation of the winter negative temperature conditions,through the calculation of temperature measurement of raw materials are mixed,access to information to determine the temperature conditions to avoid the concentration of ethylene glycol solution of frozen water should be used in the 15%-21%.of different concentration in negative temperature under the condition of ethylene glycol(15%,18%,21%)for preparing double a group of MPC,the effect of ethylene glycol on the performance of MPC analysis and comparison of the test results,the preparation of two component determined the optimal concentration of MPC ethylene glycol.(2)simulating the negative temperature conditions in northern winter,estimating the range of freezing point concentration of ethylene glycol solution,mixing MPC slurry with different concentrations of ethylene glycol solution under negative temperature conditions,and analyzing the influence of ethylene glycol on the properties of MPC.(3)Under the condition of ethylene glycol solution,the content of borax,the ratio of water to cement and the ratio of ammonium dihydrogen phosphate to magnesium oxide were changed.The fluidity,fluidity loss,setting time and strength of each age of the prepared MPC materials were measured.By comparing the test results,the optimum proportion of the two-component MPC materials was determined under negative temperature conditions.The experimental results show that ethylene glycol has the dual effects of enhancing the negative temperature hydration activity and retarding hydration in MPC repair mortar with a certain concentration of ethylene glycol solution.It can not only guarantee the workability of MPC repair mortar under negative temperature condition,but also ensure that the strength of mortar can still increase during the negative temperature curing,and it can be changed into positive temperature curing.A higher strength can be obtained.Under the negative temperature of about-15 0 C in the north,the refired magnesium oxide is used,the ammonium dihydrogen phosphate is added by grinding method,the amount of borax is 10 and the ratio of water to cement is 0.15.When the concentration of ethylene glycol is 18%,the properties of the two-component MPC modified paste are the best.Borax content When the ratio of water to cement is 0.17 and the concentration of ethylene glycol is 18,the MPC two-component repair mortar has the best performance.