Mechanical Performance Of Polymer Modified Mortar

In recent years,polymer modified mortar(PMM)has been widely used in civil engineering.As a new kind of composite material with organic phase and inorganic phase,PMM has different mechanical properties and temperature sensitivity with ordinary portland cement(OPC).Thus,when PMM mixed by different dosage,with different Tg,and placed in different ambient temperature,their mechanical performance is totally different.In this paper,five kinds of polymer with different Tg were designed to investigate the mechanical properties of PMM.Because of the remarkable influence of temperature on the mechanical properties of polymer emulsion,the Tg and ambient temperature is an important parameter in this paper.The mechanical properties of mortar include non destructive mechanical properties such as static elastic modulus,dynamic elastic modulus,and destructive mechanical properties such as compressive strength and flexural strength.Based on the experimental results,a simulation method aimed at the static elastic modulus of the PMM was established.Under normal temperature,the static compressive elastic modulus of the PMM with soft polymer did not decreased.while the static compressive elastic modulus of the PMM with hard polymer decreased slightly.Under high temperature,the static compressive elastic modulus of the PMM with soft polymer decreased obviously,while the static compressive elastic modulus of the PMM with hard polymer decreased slightly.The experimental results of dynamic elastic modulus showed some comclusions as follows.Under normal temperature,the uniaxial compressive dynamic elastic modulus of OPC was greater than the PMM.Under high temperature,the uniaxial compressive dynamic elastic modulus of PMM was larger than that of OPC.For single cantilever bending condition,the storage modulus of PMM decreased linearly and slowly(the slope is sharper than OPC)when the ambient temperature is below Tg.The storage modulus of PMM decreased sharply when the ambient temperature is above Tg.The experimental results are as follows.Under normal temperature,the three point flexural strength of PMM with soft polymer was higher than that of OPC.The three point flexural strength of PMM with hard polymer was almost equal to the blank.Under high temperature,the three point flexural strength of both OPC and PMM decreased,while the three point flexural strength of PMM decreased more obviously.Under normal temperature,the uniaxial compressive strength of PMM with soft polymer decerased sharply while the uniaxial compressive strength of PMM with hard polymer was almost equal to that of OPC.Under high temperature,the uniaxial compressive strength of both P MM and OPC decreased obviously.Through the calculation of fracture toughness and fracture energy we can found: under normal temperature,the fracture toughness and fracture energy of PMM with soft polymer were significantly higher than that of OPC,while the fracture toughness and fracture energy of PMM with hard polymer were almost equal to that of OPC.In addition,this paper establishes a four levels simulated elastic modulus calculation method.The PMM is divided into 4 Parts: the hardened cement paste with 0 porosity,the hardened cement paste with a porosity,the polymer modified cement paste and the polymer modified mortar.By means of the empirical formula,the Mori-Tanaka inclusion theory and the finite element(FEM)simulation,the parameters of each level was translated to the next level.The simulated results of the elastic modulus of PMM was in agreement with the experimental results.