Southeast University

Sobute New Materials Co., Ltd

Jiangsu Sobute New Materials Co., Ltd.

Jiangsu Research Institute of Building Science Co. Ltd

Jiangsu Bote New Materials Co. Ltd.

Qian Tian

Yujiang Wang

Jiaping Liu

Jianye Zhang

Hang Zhang

Chao Chen

Jianhui Wu

Qiang Zhao

Fei Guo

Xiao Shi

Ting Yao

Zhilin Liu

Junfeng Wen

Xudong Wang

Chunfeng Bai

Disclosed is a method for testing the self-drying effect of a cement-based material, capable of testing the change in humidity of the cement-based material after the final setting until the Id stage of adding water, so as to reflect the water consumption therein and the self-drying course. In the time period after the final setting of the cement-based material until the 1 d stage of adding water and forming, the dew-point temperature inside the cement-based material is tested, and then the relative humidity inside the cement-based material is calculated using a formula. The present invention can test the change in humidity of the cement-based material after the final setting until the Id stage of adding water, so as to reflect the internal water consumption therein and the self-drying course. Further provided is a multi-stage test method for the whole course, capable of testing the whole course of continuous reduction in relative humidity from an initial 100%, in sealed conditions, starting with adding water and formation of the cement-based material, so as to provide a theoretical foundation for the quantitative calculation of the self-drying and shrinking thereof.

Method for testing self drying effect of cement-based material

Disclosed is a method for testing the setting time of a cement-based material: testing the capillary negative pressure of a non-bleeding cement-based material, with the time at which the capillary negative pressure reaches a threshold value A as the initial setting time, and/or the time at which the capillary negative pressure reaches a threshold value B as the final setting time, wherein threshold value A is 8-10 kPa, and threshold value B is 54-56 kPa. Alternatively, threshold value A and threshold value B are determined by the following method: formulating a cement-based material for the determination of threshold values with the same raw materials at the same formulation ratio; after vibration-compaction, placing a portion into a measuring mold; after vibration-compaction, testing the capillary negative pressure of the non-bleeding cement-based material placed in the measuring mold; under the same conditions, synchronously testing and determining the initial setting time and final setting time of the cement-based material for the determination of threshold values by a penetration resistance method; the capillary negative pressure corresponding to the initial setting time and final setting time of the cement-based material for the determination of threshold values are respectively threshold value A and threshold value B. The method can not only be used in standard tests for a laboratory cement setting time under standard temperature conditions, but can also be used to realize remote, automatic, and continuous in situ monitoring for the setting time of a cast-in-situ concrete structure.

Method for testing setting time of cement-based material

A transconductance-enhancing passive frequency mixer comprises a transconductance amplification stage, a frequency mixing stage, and an output transresistance amplifier. The transconductance amplification stage has a pre-amplification transconductance-enhancing structure, so that the transconductance is greatly enhanced, thereby obtaining the same transconductance value at a lower bias current. A radio-frequency current is modulated by the frequency mixing stage to generate an output mid-frequency current signal. The mid-frequency current signal passes through the transresistance amplifier, to form voltage output, and finally obtain a mid-frequency voltage signal. The transresistance amplifier has a transconductance-enhancing structure, thereby further reducing input impedance, and improving current utilization efficiency and port isolation. The frequency mixer has the characteristics of low power consumption, high conversion gain, good port isolation, and the like.

Transconductance-enhancing passive frequency mixer

Growing community of inventors

Nanjing, China

Qian Tian