A new scheme for analysis of pore characteristics using centrifuge driven non-toxic metal intrusion

Abstract

This study investigates the intrusion behavior of a non-toxic low-melting-point metal using centrifugation to develop a better pore characterization technique for cementitious materials such as ordinary Portland cement. This study suggests that centrifugation is a safe and effective method for driving melted low-melting-point alloys into cementitious material at pressure between 12 and 15 MPa. The non-toxic Field's metal alloy is suggested as a replacement for the toxic Wood's metal. For pores between 100 nm and 10 lm, Field's metal can be used without vacuuming the sample before intrusion. For pores [10 lm, pre-vacuuming of the sample is suggested to prevent the extrusion of hardened Field's metal from large pores. Different failure modes for the extrusion phenomenon were analyzed and the results suggest that weak bonding between the Field's metal and the cement matrix is the main cause for the extrusion. The new scheme may also be applicable to porous geomechanical materials such as porous rock, sand and clay.

Characterization of the Pore Structure of Well Cement under Carbon Capture and Storage Conditions by an Image-Based Method with a Combination of Metal Intrusion

“…A zoomed-in view of the inner unreacted cement ( Figure 9 (e-1)) illustrates that the porous CSH gel, capillary pores, and unhydrated cement grains are the three main morphologies in unreacted cement. 31 , 34 Visually, the porous CSH gel makes up the major portion of unreacted cement and possesses a massive amount of small capillary pores with diameters less than a few hundred nanometers. In contrast, the size of capillary pores is much larger but the number is much lower.…”

“…The relevant chemical composition and physical properties of Field’s metal are listed in Table 2 . 31 A low-viscosity transparent epoxy resin (purchased from Kemet, Inc.) was used to prepare the epoxy resin-impregnated samples.…”

“…37 First, the scale was set based on the scale bar on the BSE image. 31 Then, the image data was converted into 8-bit grayscale, with the range of grayness from 0–255. Binary images of the pores were obtained by thresholding of pores.…”

“…Then, a scheme based on the combination of nontoxic low-melting point metal intrusion and BSE image analysis was applied. 31 , 32 Before the application, a comparative study between the metal intrusion method and epoxy impregnation method was conducted to state the feasibility and advantage of the metal intrusion method in pore structure analysis. Based on the pore structure analysis results from the BSE image analysis, the variation characteristics of the pore structure of exposed cement along the corrosion direction in a two-dimensional (2D) plane were analyzed.…”

“…An additional limitation of MIP and BET methods is they cannot offer a visible interpretation of pores, such as connectivity and shape. Image analysis based on BSE imaging is an effective way to offer quantitative information about the pore structures of porous media, such as cement-based materials on a fine scale. , During the image analysis, thresholding is particularly important to differentiate the background from the image objects of interest. , However, for the traditional epoxy resin-impregnated cement, the contrast and gray-level differences between epoxy resin and hydration products are small, making it difficult to distinguish epoxy-filled pores individually and obtain trustworthy data. − Therefore, image analysis based on epoxy impregnation was normally used to provide some qualitative information on the pore structure of cement in previous research studies.…”