地聚合物混凝土抗冻性影响因素

The Influence Factor of the Anti-freeze of Geopolymer Concrete

通过调整地聚合物的氧化物SiO_(2)/Al_(2)O_(3)、Na_(2)O/Al_(2)O_(3)和H 2O/Na_(2)O的物质的量比,利用碱激发偏高岭土制备不同强度等级的地聚合物混凝土。同时,用相同强度等级的普通硅酸盐水泥(OPC)混凝土作对比,评价地聚合物混凝土的抗冻性。结果表明:随着n(Na_(2)O)/n(Al_(2)O_(3))和n(H_(2)O)/n(Na_(2)O)增大,地聚合物混凝土的抗冻性降低;当n(SiO_(2))/n(Al_(2)O_(3))=3.3时,地聚合物混凝土的抗冻性最佳,冻融循环次数可达200。当地聚合物混凝土达到冻融极限时,相对动弹性模量损失较小,说明其冻融破坏的主要形式是表面脱落,而其内部结构破坏速率较OPC混凝土更慢。当抗压强度为30~50 MPa时,地聚合物混凝土抗冻性略优于OPC混凝土的抗冻性;但抗压强度在50~70 MPa时,OPC混凝土抗冻性远优于地聚合物混凝土抗冻性。此外,地聚合物混凝土具有较高水饱和系数,值均在0.85~0.95,说明地聚合物混凝土孔结构以开口孔为主。

Geopolymer concretes with different compressive strength were prepared by alkali-activated metakaolin by adjusting the molar ratio of geopolymer oxides SiO_(2)/Al_(2)O_(3),Na_(2)O/Al_(2)O_(3)and H 2O/Na_(2)O.The freeze-thaw cycles of geopolymer concrete and ordinary portland cement(OPC)concrete were tested and the anti-freeze property of those concrete were compared.Results showed that the anti-free-zing of geopolymer concrete decreased with the increase of the n(Na_(2)O)/n(Al_(2)O_(3))and n(H_(2)O)/n(Na_(2)O).The optimal anti-freezing of geopolymer concrete was achieved when the n(SiO_(2))/n(Al_(2)O_(3))=3.3 was used and the freeze-thaw number could reach to 200 cycles.There was a slightly decrease in relative dynamic elasticity modulus when freeze-thaw damage of geopolymer concrete reached to the failure limit,illustrated that the main failure form of geopolymer concrete under the freeze-thaw cycles was the surface scale,but the damage ratio of inner structure was lower than that of the OPC concrete.For concrete with compressive strength between 30 MPa and 50 MPa,the anti-freezing of geopolymer concrete was slightly better than that of the OPC concrete.However,for concrete with compressive strength between 50 MPa and 70 MPa,the anti-freezing of geopolymer concrete was much lower than that of the OPC concrete.The coefficient of water saturation of geopolymer concrete ranged from 0.85 to 0.95,indicating that the majority pore was the open pore.