水和氯离子在风积沙混凝土中的迁移规律

Migration law of water and chloride ions in aeolian sand concrete

为解决中国西北部地区普通河砂资源匮乏问题,利用库布齐沙漠风积沙等质量替代普通河砂作为细骨料配制风积沙混凝土.研究不同水胶比、不同浓度NaCl溶液对风积沙混凝土中水分和氯离子渗透规律的影响,通过分层钻孔取粉和化学滴定的方法测定氯离子含量,探讨毛细作用下水分和氯离子传输之间的联系.结果表明:水分作为氯离子传输的媒介,氯离子的侵入深度远小于水分的侵入深度,两者传输呈现非同步性;毛细吸收28 d后,风积沙混凝土水胶比为0.55的试块水分侵入深度约为氯离子侵入深度2倍,水胶比为0.45和0.40的风积沙混凝土试块水分侵入深度大约为氯离子侵入深度1.5倍;毛细吸收超过7 d时,水胶比为0.55的风积沙混凝土试块内部生成大量盐结晶,减缓水分侵入速率;在毛细吸盐前期阶段,风积沙混凝土试块内部水分和氯离子侵入深度近似呈线性关系,随着毛细吸收时间的推移,水分在其基体内部迁移速率减小,在高浓度梯度作用下氯离子以扩散方式继续向更深处渗透;当毛细吸盐浓度超过6%,风积沙混凝土试块内部氯离子侵入量不再随NaCl浓度的增大而增大.该研究可为风积沙混凝土在中国西北地区水利工程耐久性研究提供一定的理论依据.

To solve the problem of resources shortage of ordinary river sand in northwestern of China,the aeolian sand of Kubuqi Desert was used instead of ordinary river sand as fine aggregate to prepare aeolian sand concrete.The effects of different water-binder ratios and different concentrations of NaCl solutions on the permeation patterns of water and chloride ions in aeolian sand concrete,the chloride ions content was determined by means of stratified borehole powder extraction and chemical titration to explore the connection between water and chloride ions transport under capillary action.The results show that water as a medium of chloride ions transport,the penetration depth of chloride ions is much smaller than the penetration depth of water,the two transport presents non-synchronous.After 28 days of capillary absorption,the water-binder ratio of aeolian sand concrete is 0.55,and the water penetration depth is about twice the chloride ion penetration depth,and the water-binder ratio is 0.45 and 0.40.The water penetration depth of the aeolian sand concrete specimen is about 1.5 times that of the chloride ion penetration.When the capillary absorption of more than 7 days,aeolian sand concrete specimens with the water-binder ratio of 0.55 generates a large number of salt crystals inside,which slows down the rate of water penetration.In the early stage of capillary salt absorption,the internal water and chloride ions penetration depth of the aeolian sand concrete specimen is nearly linear,with the capillary absorption time,the water migration rate inside its matrix decreases,and the chloride ions continues to penetrate deeper by diffusion under the effect of high concentration gradient.When the capillary salt absorption concentration exceeds the critical value of 6%,the chloride ions penetration inside the aeolian sand concrete specimen does not increase with the increase of NaCl concentration.This research can provide a theoretical basis for the research on durability of aeolian sand concrete in water conservancy projects in Northwest of China.