Study On The Stress-strain Relationship Of Seawater Sea-sand Concrete Under Uniaxial Compression

With the continuous development of economy and society,the consumption of concrete is considerably increasing.However,the use of fresh water and river sand as raw materials for concrete mixing has become a great challenge for the constructions in marine and coastal regions due to the shortage of these resources.Thus,the direct use of seawater and sea-sand may be an attractive choice and the relevant study has been widely conducted in recent years.Seawater sea-sand concrete refers to the concrete made of seawater and sea-sand to replace all or part of the traditional raw materials of fresh water and river sand in the mix.In this paper,more than 300 specimens with different mix proportions and curing ages were used to analyze the influence of seawater and sea-sand on the mechanical performance of concrete under uniaxial compression,which provided valuable guidance for the existing research of sea water sea-sand concrete.On the basis of experimental study,the stress-strain model of seawater sea-sand concrete was obtained by theoretical analysis.The specific work is listed as follows:(1)The concrete mix proportions were determined according to the trial tests,and 45 cubes with the size of 100 × 100 × 100 mm and 45 cubes with the size of 150 × 150 × 150 mm were used to explore the influence of sea water and sea-sand with different replacement ratios on the compressive strength and failure modes of concrete cube under different curing ages and mix proportions.The results show that the existence of seawater and sea-sand improves the cubic compressive strength.At the same time,the strength conversion coefficient for the specimens with different sizes was also analyzed.(2)The influence of seawater and sea-sand on the elastic modulus and Poisson's ratio of concrete was investigated by 45 specimens with the size of 150 × 150 × 300 mm.The test results show that seawater and sea-sand can both improve the elastic modulus of concrete,but have little effect on Poisson's ratio.(3)Additional rigid elements were used in this study to obtain the complete stress-strain curves of seawater sea-sand concrete under uniaxial compression.Considering the costs and test results of several trial tests,the disc springs were finally adopted as the rigid elements,which can successfully absorb the dissipated energy during the post-peak branch of stress-strain curves.(4)Based on 135 prisms with the size of 100 × 100 × 300 mm,the effect of seawater and the replacement ratio of sea-sand on the stress-strain relationship of concrete under different age and mix proportion was discussed.The results show that the compressive strength,peak strain and initial tangent modulus of concrete are increased with the existence of seawater and sea-sand.At the same time,with the increase of replacement ratio of sea-sand,the compressive strength,peak strain and initial tangent modulus of seawater sea-sand concrete exhibit a decreasing trend.According to the test results,the prediction formulas for compressive strength,peak strain and initial tangent modulus of seawater sea-sand concrete were determined respectively,and a new stress-strain model for seawater sea-sand concrete under uniaxial compression was proposed.The test results show that the new model can effectively predict the stress-strain performance of seawater and sea-sand concrete,which provides a basis for the application of seawater sea-sand concrete in practical design.