基于NMR的风积沙混凝土冻融孔L隙演变研究

利用风积沙等质量替代河砂来配制风积沙混凝土,并对其进行抗冻性试验,同时借助核磁共振(NMR)技术分析其冻融孔隙演变特征.研究表明:评价风积沙混凝土抗冻性时,相对动弹性模量指标比质量损失率指标更为精准;经冻融循环后,风积沙混凝土的孔隙度和渗透率均增大,其中风积沙替代率为40%的风积沙混凝土束缚水饱和度增大、自由水饱和度减小,其抗冻耐久性最佳;风积沙混凝土的孔隙分布会影响其抗冻性的优劣,冻融循环后若孔径小于10nm的孔隙增多且大于100nm的孔隙减少,则可延缓混凝土冻融损伤,若孔径小于10nm的孔隙减少且大于100nm的孔隙增多,则会加剧混凝土冻融损伤.

Freeze Thaw Pore Evolution of Aeolian Sand Concrete Based on Nuclear Magnetic Resonance

Aeolian sand rather than river sand was used to prepare concrete. The freeze thaw resistance test of aeolian sand concrete was carried out. The freeze thaw evolution of pore characteristic of aeolian sand concrete was analyzed by means of nuclear magnetic resonance(NMR) technique. The results show that for evaluation of frost resistance of aeolian sand concrete, relative dynamic elasticity modulus is more accurate than mass loss rate; the porosity and permeability of the concrete increase after the freeze thaw cycles in which the frost resistance of aeolian sand concrete with the replacement rate of 40% is the best. The bound water saturation after the freeze thaw cycles of the concrete with the replacement rate of 40% increases and the free water saturation is reduced. The pore distribution of aeolian sand concrete affects the frost resistance. After the freeze thaw cycles, the pores with radius less than 10nm increase and pores with radius larger than 100nm decrease with the result that the freeze thaw damage delays. Conversely, pores with radius less than 10nm decrease and pores with radius larger than 100nm increase which may result in aggravating the freeze thaw damage.