The Fundamental Investigation of Pure Mechanical Behaviors of Cement Paste without Microstructural Flaw
In this paper, the mechanical behaviors of cement paste in several drying conditions after arresting hydration will be discussed.In the past, some researchers attempted to investigate the mechanical behaviors of cementitious material in several drying conditions.The purpose of those studies is to comprehend the influence of drying shrinkage on cementitious material.On the other hands, this paper would like to discuss about the change of pure mechanical behaviors in association with drying condition without microstructural flaw due to drying shrinkage.The main purpose of this study is to establish the experimental method of mechanical test, which can determine the pure mechanical behaviors due to the change of microstructure such as cement hydration, pore structure and so on.In this experiment, OPC pastes, which water to cement ratio is 0.4, are used.Plate-like paste specimens is casted, the specimen size is 5x10x250 mm and they store until certain curing time by sealed curing.After 28 days curing, the specimen is cut for three-points bending test and the size is 5x10x60 mm.All specimens are imposed arresting hydration of cement by using solvent exchange method with Isopropanol.After arresting hydration, all specimens are put into the chambers which relative humidity (RH) are kept to 95, 72, 48, 33, 20 % for 12 days.Subsequently, three-points bending tests are conducted to clarify bending strength and elastic modulus.Furthermore, to understand the fundamental physical properties of OPC paste, the changes in moisture content, true density and total pore volume are determined up to 56 days curing.As a result, the softening behaviors can be obtained in case of relatively higher RH whereas relatively lower RH cases indicates brittle behavior.It is notable that the bending strength is about 4.5 times of bending strength of sealed case when RH is lower than 48%.This tendency is different from previous experimental results that the arresting hydration was not carried out before drying.That bending strength of lower RH case is much higher may be attributed to no microstructural flaw due to drying shrinkage.Moreover, the increase of bending strength could be interpreted by the microstructural changes of C-S-H.
Bending strength Elastic modulus Drying condition Arresting hydration
T.Miura H.Nakamura Y.Yamamoto
Graduate School of Civil Engineering, Nagoya University, Nagoya, Japan
国际会议
福州
英文
321-327
2018-11-04（万方平台首次上网日期，不代表论文的发表时间）