Mechanical Properties And Constitutive Relation Of Basic Magnesium Sulfate Cement Concrete

It is very important for researching the mechanical properties and constitutive relation of new concrete to take full advantage of the high strength,rasing design standards and reducing project cost.A new cement named“Basic Magnesium Sulfate Cement”was invented,it’s cementitious material is MgO-MgSO₄-H₂O system,the main hydration product is Basic Magnesium Sulfate whisker（5Mg（OH）·MgSO₄·7H₂O）.The cement has advantages of fast setting,early strength,high strength,especially high tensile strength and rupture strength.The thesis carried out a series of studies such as compression test,bending test,splitting tensile test and compression stress-strain curve test based on the research status at home and abroad of ordinary cement concrete and Basic Magnesium Sulfate Cement Concrete（BMSCC）,the basic mechanical properties and constitutive relation equations are obtained.The main conclusions of this paper are as follows:（1）There are strong linear relationships between axial compressive strength and cubic compressive strength,splitting tensile strength and cubic compressive strength,rupture strength and cubic compressive strength of BMSCC.Under the condition of the same strength grade,the axial compressive strength of BMSCC of C20,C30,C40,C50,C55 and C60 are increased by 23%,22%,22%,26%,27%and 28%than that of ordinary concrete.Under the condition of the same strength grade,the splitting tensile strength of BMSCC of C20,C30,C40,C50,C55 and C60 are increased by27%,32%,40%,53%,66%and 121%than that of ordinary concrete.Under the condition of the same strength grade,the rupture strength of BMSCC of C20,C30,C40,C50 are increased by 38%,25%,8%,1%.（2）There is a hyperbolic relationship between static elastic modulus and cubic compressive strength of BMSCC.The elastic modulus of BMSCC of C40^C60 are increased by 9%²7%than that of ordinary concrete.(3 The average Poisson’s ratio of BMSCC is 0.23.（4）The failure modes of BMSCC is oblique section failure.The cracks of the surface develop along the oblique direction,run through the whole section,the sample is divided into small columns by cracks,which is similar to ordinary concrete.（5）The regularities of uniaxial compression stress-strain curve of BMSCC is:with the increase of strength of BMSCC,the stress-strain curves become steeper and steeper.With the increase of strength,the peak stress of BMSCC are higher than that of ordinary concrete;in the same strength grade,the descending stage of stress-strain curves of BMSCC are slightly gently than that of ordinary concrete,this shows that BMSCC has higher strength and it is more ductile than ordinary concrete slightly.