Study On Durability Of Fiber Reinforced Expansive Self-consolidating Concrete

Expansive agent(EA)and fiber are effective in controlling shrinkage and cracking,and improving the durability of concrete.There has been extensive research on fiber reinforced concrete and expansive concrete,however,few studies on the durability of fiber reinforced expansive self-consolidaitng concrete(FRESCC)can be found,although it has been used in engineering applications.This paper evaluates the free shrinkage,early age cracking resistance,chloride penetration resistance and frost resistance of FRESCC quantitatively,and the durability was compared among FRESCC,expansive self-consolidating concrete(ESCC)and fiber reinforced self-consolidating concrete(FRSCC),thus providing reference for durability evaluation of FRESCC.Twenty three types of samples were prepared including one control group,four EA contents(6%,8%,10% and 12% of the mass fractions of cementitious materials),three steel fiber(SF)contents(0.25%,0.50% and 0.75% by volume),three polypropylene fiber(PP)contents(0.05%,0.10% and 0.15% by volume),three hybrid fiber contents and nine combinations of EA(8% by mass)and fibers.The tests of free shrinkage and compressive strength were conducted when the workability met the requirements of specifications.Early age free shrinkage test was conducted based on the contact method and aimed at analyzing the shrinkage behavior of SCC with age of 10 h-5 d.Two different curing conditions including sealed-cure and top surface exposed to the air-cure were adopted to explore the effect of curing conditions on the free shrinkage of SCC.Test results indicate that when the length change is less than 0.02% for SCC with no EA,the inhibition effect of PP on free shrinkage is greater than that of SF for specimens with equivalent fiber factor.However,when the expansion of SCC with EA is relatively large,SF restrains the free expansion of SCC more significantly compared with PP for specimens with equivalent fiber factor.The slab test was employed to test the early age cracking resistance of SCC,and the initial cracking time and propagation of cracks over time were both observed.Test results indicate that increase of EA dosage presents no significant effect on improving the early age cracking resistance capability.Compared with SF,PP with equivalent fiber factor is particularly effective in reducing the nominal total crack area.In general,crack reduction factors of FRESCC are 70% greater than that of FRSCC containing fiber only.It indicates that the combination of EA and fibers enable SCC to present better early age cracking resistance.The chloride penetration resistance of FRESCC was determined by standard test method for water-soluble chloride in concrete.This study established levels of chloride penetration of FRESCC and found that chloride content increases with the incorporation and increase of fibers at depths less than 17.5 mm.However,chloride penetration resistance along the depth is enhanced with increasing fiber factor.And at the depth of 17.5 mm,the chloride penetration resistance of FRESCC is better than that of SCC containing EA only.The rapid freezing and thawing test was performed to evaluate the forst resistance of FRESCC.The results show that the relative dynamic modulus of elasticity(RDME)of ESCC in the presence of fibers decreases slightly when compared with ESCC in the absence of fibers,and decreases with the increasing fiber factor.It also shows that the increase of fiber content decreases the speed of surface spalling of the specimens as well as the mass change.