The Volume Stability Of Concrete Mixed With MgO And Stress Simulation Analysis

Mass concrete volume stability problem in the modern construction is widespread in the concrete.Concrete volume change will inevitably cause deformation and crack of concrete and its structure,accelerate concrete chemical erosion, carbon, steel rust, reduce the strength of concrete and the safetyof structure.This paper focuses on the mechanical properties, deformation properties and correlation ofconcrete with two novel expansive materials. Based on the finite element ANSYS software, theinternal stress distribution of MgO concrete was analyzed. The main research conclusions are asfollows:(1) When the E1expansion material dosage less than8%, the compressive and flexural strengthof concrete increased with the expansive material content. When the E2expansive material dosagewas no more than6%, the compressive and flexural strength of hydraulic concrete increased with theexpansive material content.(2) The compressive and flexural strength of concrete mixed with MgO after autoclave increasedwith the increase of expansion rate at first, then decreased. When the expansion rate of the concretemixed with MgO was controlled in a certain range, the compression and flexural strength of concretein autoclave was improved.(3) The free expansive ratio of concrete and hydraulic concrete mixed with MgO in20°C curingto360d was about1.8and2.0times of the limit expansive ratio respectively. While curing in60°Cwater, free expansive ratio was about2.2and2.5times of the limit expansive ratio respectively. In theearly age, the free expansive ratio of MgO concrete was lower than the autogenous volume expansiveratio. In the later age, the free expansive ratio was higher than that of autogenous volume expansiveratio. Autoclave expansion rate was higher than the free expansion rate.(4) From the SEM images, TG-DSC curves and XRD patterns of the cement paste with6%expansion material. The hydration degree of expansion materials in autoclave condition significantlywas higher than that in the normal condition, which increased gradually with the prolongation ofcuring time.(5) The SX horizontal tensile stress, SZ horizontal compressive stress, SXY horizontal shearstress, and SXZ horizontal shear stress inside the MgO concrete, and the Z-direction tensile stress ofreinforcement increased with the content of expansive material.