Study On Durability Of Fiber Textile Reinforced Seawater Sand Concrete In Simulated Marine Environment

Seawater and sea sand concrete(SWSSC)is prepared by using sea water as mixing water and sea sand as mixing aggregate.Its mechanical properties is comparable to ordinary concrete,and it does not need to consume fresh water and river sand resources.It is one of the research hotspots in the field of concrete at present.The problem of reinforcement corrosion caused by chloride ions in seawater and sea sand is the bottleneck of SWSSC in the material engineering application.Fiber fabric reinforced concrete(TRC)is a composite material made of high performance fiber fabric and concrete matrix,which is not restricted by the problem of steel corrosion.Therefore,using sea water and sea sand to prepare fabric reinforced sea water sand concrete(TRSWSSC)can not only alleviate the shortage of fresh water and river sand resources,but also obtain green environmental protection and excellent performance for TRC composite material,which meets the development needs of the society.This paper systematically studies the long-term mechanical behavior of basalt fiber fabric reinforced seawater sand concrete and alkali-resistant glass fiber fabric reinforced seawater sand concrete specimens under the conditions of room temperature,seawater immersion at high temperature and seawater wetting and drying cycle,and the improvement effect of epoxy resin on the mechanical properties of the specimens.The main research results are as follows:(1)The four-point bending properties of the specimens were tested at room temperature.The results show that the number of fabric layers has a great influence on the bending properties of the BTR-SWSSC specimens,and the increase of the number of fabric layers makes the BTR-SWSSC specimens obtain better bending properties.The mechanical properties of TRC specimens(BTR-SWSSC,GTR-SWSSC)prepared by seawater and sea sand were not significantly different from those prepared by fresh water and river sand at room temperature.Epoxy resin treatment of the fiber surface can improve the mechanical properties of the fiber,effectively enhance the bending strength of the specimen,and increase the number of cracks.(2)Mechanical tests were carried out on the specimens after seawater dry-wet cycle treatment.Compared with the data at room temperature,the results showed that seawater dry-wet cycle would lead to the reduction of specimen strength.The strength retention rate of BTR-SWSSC specimens was about 68% when the sea water was recycled for 56 days.After 14 days of drying and wetting treatment,the strengthening effect of basalt fiber on the matrix is greatly reduced,and the strengthening effect is basically lost at 56 days.Glass fiber fabric reinforced concrete(GTR-SWSSC)has better durability under the condition of wetting and drying cycle.When the wetting and drying cycle is 56 days,the strength retention rate of the specimens is about 65%.However,the strengthening effect of glass fiber specimens is still very obvious,and the durability of alkali resistant glass fiber fabric is better than that of basalt fiber.Epoxy resin processing fiber surface can improve the bending strength of the specimens,delay the degradation of specimen strength within the time limit.The enhancement effect of epoxy resin processing on the basalt fiber specimens basically lost at 28 days in the dry-wet circulation.The strength of alkali glass fiber reinforced specimens are 2 MPa higher than those without epoxy resin at 56 days.(3)After the specimens were soaked in seawater at high temperature,the mechanical test and microscopic observation were carried out on the specimens.The results showed that the bending properties of the specimens gradually decreased with the process of soaking,and the strength retention rate was lower than that of the specimens with dry-wetting cycles in the same period.Compared with the specimens prepared by sea water and sea sand,the strength retention rate of the specimens prepared by fresh water and river sand was slightly higher at 7 days,and the strength retention rate of the specimens in subsequent periods was similar.The durability of glass fiber specimens is better than that of basalt fiber specimens.The strengthening effect of the basalt fiber on the concrete was lost after soaking for 7 days,and the reinforcement effect of the specimen treated with epoxy resin was lost after soaking for 56 days.For glass fiber reinforced specimens,the fiber reinforcement effect always exists.For the specimens prepared by the two fibers,the strength retention rate decreased significantly compared with the specimens in the same period of dry-wet cycle.The protective effect of epoxy resin failed earlier,and the seawater immersion environment was more harmful to the specimens than the dry-wet cycle environment.