Controlling and increasing the inherent voltage in cement paste

Abstract

An inherent voltage occurs in cement paste, making the material an electret. Both poling (up to 225 V/m DC, causing long-range ion movement) during the 24 h setting and the use of sodium silicate liquid (which provides Na þ ions) as an admixture were found to increase the inherent voltage, in addition to making the voltage more stable and better controlled. Without poling and sodium silicate, the inherent voltage after curing varied in sign and magnitude in an uncontrolled fashion among specimens poured from the same mix; for the same specimen, it varied significantly with the curing time and asystematically during the first 10 days of curing and stabilised thereafter. With both sodium silicate and poling, the voltage was positive (same polarity as the poling voltage), decreased with time throughout curing, and levelled off at a voltage that increased with increasing sodium silicate content, with the highest value attained in the present study being 0 . 35 V. The time constant for depoling during curing ranged from 2 to 7 days in the initial depoling period (up to 11 days), and ranged from 74 to 150 days in the subsequent period.

Electret, piezoelectret and piezoresistivity discovered in steels, with application to structural self-sensing and structural self-powering

“…The electrets of this work are to be distinguished from prior electrets that are essentially not conductive (mostly in the form of polymers or ceramics [1][2][3][4][5][6]). Due to the essential non-conductivity, the prior electrets act as capacitors and DC electric current cannot continuously flow through them (figure 11(a)); only a pulse of DC current can flow from the positive electrode to the negative electrode.…”

“…An electret is a manifestation of the dielectric behavior of the material. Electrets have been reported for low-conductivity materials such as polymers and ceramics, including cementbased materials [1][2][3][4][5][6]. They are commonly formed after an electrical activation process such as one involving corona discharge.…”

Kaolin Clay-Based Geopolymer for Ionic Thermoelectric Energy Harvesting

“…Prior to applying any temperature, a high intrinsic voltage of −106 mV was observed, as previously reported in the literature. 28 , 51 , 52 To extract information solely on thermoelectric behavior of a material, stabilization of the intrinsic voltage is necessary. After 40 h, a stable value of V = −19.6 mV was recorded and a temperature of T 1 = 60 °C was applied to the sample through a ceramic heater.…”