交通工程废弃混凝土再生砂的基本性能

Basic Performance of Recycled Sand for Waste Concrete in Traffic Engineering

选用铁路和公路工程六种废弃混凝土制备再生砂,通过试模法、硫酸钠溶液法、压碎指标法等对其基本性能指标进行分析。结果表明:再生砂表面粗糙且微粉含量高,会对试模法测试再生砂饱和面干吸水率造成不利影响,因此采用试模法测试再生砂饱和面干吸水率时需控制其微粉含量;再生砂抗硫酸盐侵蚀能力优异但压碎指标较低,原因是再生砂中存在高孔隙率的黏附砂浆,可释放硫酸钠结晶产生的应力,但无法抵消外部荷载对再生砂产生的破坏;六种再生砂有害物质含量均小于规范限值,再生砂有害物质含量与废弃混凝土配合比和服役环境密切相关。为避免废弃混凝土中有害物质含量超标,回收利用废弃混凝土时应根据其设计强度等级和服役环境合理分类。

Six types of waste concrete from railway and highway engineering were selected to prepare recycled sand.Their basic performance indicators were analyzed through trial mold method,sodium sulfate solution method,and crushing index method.The results indicate that the rough surface and high content of micro powder in recycled sand can have adverse effects on the dry water absorption rate of the saturated surface of recycled sand using the trial mold method.Therefore,when using the trial mold method to test the dry water absorption rate of the saturated surface of recycled sand,it is necessary to control its micro powder content.Recycled sand has excellent resistance to sulfate attack but low crushing index,the reason is that there is a high porosity adhesive mortar in the recycled sand,which can release the stress generated by sodium sulfate crystallization,but cannot offset the damage caused by external loads on the recycled sand.The content of harmful substances in six types of recycled sand is less than the standard limit,and the content of harmful substances in recycled sand is closely related to the mix proportion of waste concrete and the service environment.To avoid excessive levels of harmful substances in waste concrete,when recycling waste concrete,it should be reasonably classified based on its design strength level and service environment.