CAJ | 학술논문

干燥收缩是混凝土的一个复杂性质,测定时存在一个长期的内部应力作用过程.通过两种主要的物理作用机理:吸附作用和分离压力作用,解释了混凝土的干燥收缩机理,并对基于两种机理建立的预测方法与试验结果进行了比较.主要包括:(1)水分在窄裂口处的直接观测;(2)不同材料的吸附曲线和吸附长度变化;(3)新拌混凝土和早期混凝土的毛细收缩;(4)防水处理混凝土的收缩机理;(5)离子浓度对收缩的影响.研究结果表明,吸附作用在水泥基材料的收缩作用中仅起到次要的作用.收缩是混凝土结构在干燥过程中产生裂缝的根源,而裂缝的存在又会降低腐蚀环境下混凝土结构的使用寿命.因此,更好地理解混凝土的收缩机理有助于今后建造更耐用、更持久的结构工程.
간조수축시혼응토적일개복잡성질,측정시존재일개장기적내부응력작용과정.통과량충주요적물리작용궤리:흡부작용화분리압력작용,해석료혼응토적간조수축궤리,병대기우량충궤리건립적예측방법여시험결과진행료비교.주요포괄:(1)수분재착렬구처적직접관측;(2)불동재료적흡부곡선화흡부장도변화;(3)신반혼응토화조기혼응토적모세수축;(4)방수처리혼응토적수축궤리;(5)리자농도대수축적영향.연구결과표명,흡부작용재수니기재료적수축작용중부기도차요적작용.수축시혼응토결구재간조과정중산생렬봉적근원,이렬봉적존재우회강저부식배경하혼응토결구적사용수명.인차,경호지리해혼응토적수축궤리유조우금후건조경내용、경지구적결구공정.
First of all it is outlined that shrinkage as measured on drying concrete is not a simple material property but the complex response of a given specimen to long lasting time-dependent internal stresses. Then the physical basis of two frequently cited approaches to explain the origin of hygral shrinkage is briefly described: capillary action and disjoining pressure. The predictions of the two concepts are compared with experimental findings. The following examples have been selected for a critical comparison: (1) direct observation of the interaction of water in a narrow gap, (2) sorption and length change isotherms of different materials, (3) capillary shrinkage of fresh and young concrete, (4) shrinkage of water repellent concrete, and (5) influence of ion concentration on shrinkage. From the presented results it can be concluded that capillary action plays a minor role in the process of shrinkage of cement-based materials. Shrinkage is at the origin of crack formation in drying concrete structures. Cracks reduce service life in aggressive environment. Better understanding real shrinkage mechanisms will help to build more durable and more sustainable constructions.