Inherently multifunctional geopolymeric cementitious composite as electrical energy storage and self-sensing structural material

Abstract

In this paper, we demonstrate for the first time that potassium-geopolymeric (KGP) cementitious composites can be tuned to store and deliver energy, and sense themselves without adding any functional additives or physical sensors, thus creating intelligent concrete structures with built-in capacitors for electrical storage and sensors for structural health monitoring. Density function theory (DFT)-based simulations were performed to determine the electronic properties of the KGP cementitious composite and understand its conduction mechanism. Experimental characterization was also conducted to determine the structure, chemical composition, conduction mechanism, energy storage and sensing capabilities of the KGP cementitious composite. The DFT simulations suggested that the KGP cementitious composite relies on the diffusion of potassium (K +) ions to store electrical energy and sense mechanical stresses. The geopolymeric cementitious composite exhibited a good room temperature ionic conductivity in the range of 12 (10-2 S/m) and an activation energy as high as 0.97 eV. The maximum power density of the KGP capacitors is about 0.33kW/m 2 with a discharge life of about 2 hours. The KGP stress sensors showed high sensitivity to compressive stress: 11 Ω/MPa based on impedance measurement and 0.55 deg/MPa based on phase measurement. With further development and characterization, the KGP cementitious composite can be an integral part of concrete structures in the form of a battery to store and deliver power, and sensors to monitor the structural integrity of urban infrastructure such as bridges, buildings and roads.

Self-Sensing Alkali-Activated Materials: A Review

“…Likewise, under tension the resistance of the specimen increases. This behaviour has been widely reported in both AAM [24][25][26]52,57,92] and OPC [106,[117][118][119][120]…”

“…As mentioned in Section 3.2, AAM have seen multiple applications without the use of conductive filler due to ionic conductivity of the alkali metals in the matrix. In simple terms, most researchers accept that strain affects the mechanisms responsible for hopping of the Na + or K + ions in the matrix [23,24,92,143]. The exact mechanisms are not completely understood, however.…”

“…II. Saafi et al [24,92] stated that the alkali ions diffuse in the structure by hopping through vacancy sites to balance the negative charge on the AlO 4 − tetrahedral. It was hypothesized that the induced load to the substrate changes the lattice structure and alters the ion diffusion paths (essentially the distances between electron holes) in the matrix.…”

“…Self-sensing mechanism in AAM (a) AAM sensor under stress, (b) ion diffusion pathway in the matrix and energy landscape, (c) effect of the compressive stress on the activation energy and hopping distance d; adapted from[92].…”

Humidity Driven Transition from Insulator to Ionic Conductor in Portland Cement

“…Such alkaline characteristics have been mainly studied to elucidation of the mechanism for the formation of C-S-H [10,11,12,13]. Nevertheless, there have been few reports on ionic conduction associated with the alkalinity of Portland cement, although there was a report that describes the conduction of potassium ions in the commercial geopolymer cement known as geocement [14]. So far, electrochemical impedance spectroscopy (EIS) has been limited to assessment of the dielectric properties, mechanical strength, carbonation, and chlorination behaviors of concrete, mortar, and cement paste [15,16,17,18].…”