Influence Of Combined Environmental Loads On Durability Of Sea Sand Concrete

With the expansion of the scale of construction and the shortage of river sand resource, sea sand has already been used as fine aggregate of concrete in many coastal areas. However, because the degradation mechanism of sea sand concrete has not been fully understood, the durability of sea sand concrete structures is poor. Located in coastal area, most sea sand concrete structures are exposed to combined environmental loads of carbonation and chloride penetration since they have been built. It is necessary to study the combined carbonation and chloride penetration with respect to durability of sea sand concrete.Firstly, an analysis of the physical properties and the contents of harmful substances of Haiyang sea sand, Haiyang washed sea sand, Changdao sea sand, Qingdao beach sand and river sand was taken. Secondly, concrete with strength class of C30, C40, C50, C60 were prepared from Haiyang sea sand, Haiyang washed sea sand and river sand. The experimental test series were described by accelerated carbonation, natural carbonation and combined carbonation and chloride penetration. Finally carbonation depth, CaCO₃ content, Ca(OH)₂ content and chloride content of concrete after different environmental loads were determined.Results show that the principle of sea sand concrete and washed sea sand concrete is basically the same as river sand concrete after carbonation. With the increase of carbonation time, carbonation depth and CaCO₃ content increase, Ca(OH)₂ content decreases; with the strength class improved, carbonation depth and CaCO₃ content decrease, Ca(OH)₂ content increases. When the carbonation time is longer and the strength class is higher, the difference of durability among the three types of concrete is smaller. After combined carbonation and chloride penetration test, the chloride content of sea sand concrete is the highest, and that of washed sea sand concrete and river sand concrete has no significant difference. The higher the strength class is, the less chloride the concrete absorbed. Chloride content increases with the penetration time, solution concentration and carbonation time. Of the above three factors, the effect of solution concentration is the strongest, followed by penetration time, the carbonation time is the weakest.