The Research On The Durability Of Basalt Fiber Reinforced Cement-based Materials

Basalt fiber is a new fiber with high elasticity module,tensile st rength limit,lower density and good thermal stability.However,the effect of basalt fibers on the mechanical properties of cement matrix materials is still controversial,and the durability of basalt fiber is uncertain in the cement matrix materials for the high alkali environment.The durability needs to be researched if the basalt fiber can act as reinforcement for marine concrete.In order to solve the above issues,the mechanical properties of basalt fiber reinforced cement matrix materials,the durability and the seawater resistance of basalt fiber reinforced cement matrix materials were investigated in this paper.The reinforced efficiency of basalt fiber on the mortar was studied by comparing with alkali free glass fiber,alkali resistance glass fibe r at the content of 1.5%wt cement.The effect of supplementary cementitious materials on the mechanical properties of mortar was also investigated.The results showed that basalt fiber had better effect on the flexural strength than alkali free glass fiber and alkali resistance glass fiber,and the strength growth ratio is 1.2%,-3.6% and-8.5%.All the fiber would lower the compressive strength.The supplementary cementing materials could improve the mechanical properties of fiber reinforced mortar.At the ambient temperature curing for 90 days,the compressive strength of fiber reinforced mortar increased by 24.4% and 8.55%,and the flexural strength increased by 13.25% and 9.64% with the partial replace of cement by 10% silicon fume and 15% fly ash.The effect of volume content,length and diameter of basalt fibers on the workability of fresh concrete and the mechanical properties of hardened concrete were studied based on the concrete of grade C40.The results indicated that the workability decreased with the increase of volume content and length,but increased with the increase of diameter in this experiment.When the volume content reached 0.2%,the slumps of fresh concrete dropped from 210 mm to 168 mm,157 mm,and 110 mm relatively for the fiber of 12 mm,18 mm and 24 mm.The addition of basalt fiber in concrete could improve the flexural strength and splitting strength,but had little effect on the compressive strength.The flexural strength growth ratio ranged from 8.6% to 21.4% at the volume content of fiber from 0.05% to 0.2% compared with plain concrete.The fiber with diameter 13 um and length 12 mm had better reinforced efficiency of basalt fiber on the compressive and splitting strength of fiber reinforced concrete in this experiment.The compressive strength increased about 5.39 to 8.4% at the volume content of fiber from 0.05% to 0.1%,and the splitting strength increased about 5.4 to 11.5% at the volume content of fiber from 0.05% to 0.2%.The alkali resistance of basalt fiber was investigated in 2 mol/L KOH,2 mol/L Na OH,saturated Ca(OH)2 and mixed simulative cement porewater by the mass loss ratio and strength loss ratio,and alkali resistance was compared with alkali resistance glass fiber in the porewater.The corrosion behavior and mechanism was investigated by SEM,EDS and XRD.In addition,the protective effect of supplementary materials on the basalt fiber was also studied.The results showed that the strength loss ratio was up to 42.19%,36.13%,14.25% and 63.3% after immersion in 2mol/L KOH solution,2mol/L Na OH solution,saturated Ca(OH)2 solution and simulative cement porewater for 32 days,and mass loss ratio was 12.01%,15.72%,0.48% and 0.47%.The corrosion result after immersion in the porewater showed that basalt fiber exhibited weaker alkali resistance than alkali resistance fiber.The mass loss ratio for basalt fiber and alkali resistance glass fiber was 0.47% and 0.83%,and the strength loss ratio was 63.3% and 21.01%.The corrosion of basalt fiber in a single alkali solution is homogeneous corrosion,but pitting corrosion in the porewater.The supplementary cementing materials can relieve the corrosion of basalt fiber in the cement matrix materials by SEM.The influence of seawater as mixing water on the mechanical properties of mortar and the resistance of chlorine and sulfate of basalt fiber reinforced concrete were investigated.Seawater as mixing water can improve the early strength of mortar.At 28 days,the compressive and flexural strength increased about 28.85% and 20.24% compared with pipe water as mixing water,but showed no superiority at 180 days.Moreover,the addition of basalt fibers in the cement matrix materials will lower the resistance of chlorine and sulfate.