脱硝粉煤灰中铵盐对水工混凝土性能的影响  

Effect of ammonium in denitration fly ash on the performance of hydraulic concrete

作　　者：孔祥芝[1] 陈改新[1] 刘艳霞[1] 张思佳[1] 吴葵 KONG Xiangzhi;CHEN Gaixin;LIU Yanxia;ZHANG Sijia;WU Kui(China Institute of Water Resources and Hydropower Research,Beijing 100038, China)

机构地区：[1]中国水利水电科学研究院,北京100038

出　　处：《水利水电技术》2020年第9期216-223,共8页Water Resources and Hydropower Engineering

基　　金：十三五国家重点研发计划(2016YFB0303601-3,2018YFC0406701);中国长江三峡集团公司科研项目(JG/18032B);中国水科院科研基金项目(SM0145B262019,SM0145B632017)。

摘　　要：利用脱硝粉煤灰拌制混凝土有时会产生刺鼻性气味,其对水工混凝土各项性能的影响尚不清楚。为此,制备了五个铵含量等级的粉煤灰样品,依据现行水工试验方法研究脱硝粉煤灰对混凝土拌和物、力学性能、抗冻性和孔结构的影响,测试了混凝土拌和与成型过程中铵盐的释放量。试验结果表明,粉煤灰铵含量在394 mg/kg以内,对水工混凝土的用水量、减水剂掺量、拌和物的坍落度没有影响,但随着铵含量增大新拌混凝土含气量增大,如果保持含气量不变,引气剂掺量需降低8%~13%。粉煤灰铵含量由6 mg/kg增加至394 mg/kg,混凝土抗压强度约降低5.8%~11.3%,降低混凝土引气剂掺量使拌和物含气量不变,则抗压强度不会降低、抗冻性能不降低。粉煤灰中铵盐引起硬化混凝土的气孔个数增加,气孔孔径减小,气孔平均弦长由0.159 mm降至0.082 mm。采用铵含量大于250 mg/kg的粉煤灰拌制混凝土,实验室内充满了强烈的刺鼻性气味。实测结果表明,混凝土在拌和与成型过程中铵盐的释放率为2.98%~10.91%,铵盐含量越高释放量越大。There is a pungent smell when the denitration fly ash is used to mix concrete,and its impact on the performance of hydraulic concrete is not clear.For this reason,five kinds of fly ash samples with different ammonium content are prepared.According to the current hydraulic test method,the influence of ammonium in fly ash on concrete mixture,mechanical properties,durability and pore structure is studied.At the same time,the release percentage of ammonium salt in the process of concrete mixing and pouring is tested.The test results show that the content of ammonium in fly ash is less than 394 mg/kg,which has no effect on water content,water reducing agent content and slump of hydraulic concrete.However,with the increase of ammonium content of fly ash,the air content of concrete mixture increases.If the air content of concrete mixture keeps unchanged,the air entraining agent content needs to be reduced by 8%~13%.The content of ammonium in fly ash increases from 6 mg/kg to 394 mg/kg,and the compressive strength of concrete decreases by 5.8%~11.3%.If the air entraining agent decreases to keep the air content of mixture unchanged,the compressive strength and frost resistance of hardened concrete will not decrease.Denitration fly ash causes the number of pores to increase significantly.The pores of hardened concrete show a trend of refinement,and the average chord length of pores decrease from 0.0159 cm to 0.0082 cm.When the content of ammonium in fly ash is more than 250 mg/kg,the laboratory is full of strong pungent smell when mixing hydraulic concrete.The measured results show that the release percentage of ammonium in the process of concrete mixing and pouring is 2.98%~10.91%.The amount of ammonium released from concrete with high ammonium content is large.

关 键 词：脱硝粉煤灰 铵盐 水工混凝土 性能 

分 类 号：TV431[水利工程—水工结构工程]