Effect of carbon nanotubes/clay hybrid composite on mechanical properties, hydration heat and thermal analysis of cement-based materials

The search for alternative materials to replace ordinary Portland cement has been the object of work that enhances the investigation of the use of pozzolanic materials and the reduction of the carbon footprint with supplementary cementitious materials. However, not all materials are available to meet the large-scale demand for cement replacement. A relevant exception is the calcined clay, a material found worldwide that, when subjected to appropriate heat treatment, presents pozzolanic reactivity and can be used as a supplementary material to cement. This review presents, through a systematic search, methods for measuring the pozzolanic reactivity of calcined clays, namely, direct, indirect, qualitative, quantitative, chemical and physical methods such as electrical conductivity (Lùxan), the force activity index, the modified Chapelle, R3, Frattini test, thermal analysis, X-ray diffraction and X-ray fluorescence spectrometry. The most usual methods to assess the pozzolanic reactivity of calcined clays were exposed and analyzed. It should be pointed out that there is greater use of the Frattini and modified Chapelle methods as well as the analysis of the mechanical strength behavior of the material in cementitious matrices. X-ray diffraction and thermal analysis were exposed as the most used correlation methods but it was also concluded that different tests are needed to generate accurate results.

Section: Analysis Of the Approaches For Pozzolanic Activity Character...mentioning

confidence: 99%

Methods for Evaluating Pozzolanic Reactivity in Calcined Clays: A Review

Pinheiro¹,

Alexandre²,

Xavier³

et al. 2023

“…The binder was the ordinary Portland cement (OPC), defined in the ASTM C150 [ 15 ]. The OPC which was used in this study is a type I cement whose composition can be easily found in other studies, and is listed in Table 1 [ 16 , 17 , 18 ].…”

Section: Materials and Experimentsmentioning

confidence: 99%

Performance Assessment of Carbon Dioxide Sequestration in Cement Composites with a Granulation Technique

Lee,

Kim,

Min

et al. 2023

The cement industry emits a significant amount of carbon dioxide (CO2). Therefore, the cement industry should recycle the emitted CO2. However, sequestration by carbonation in cement composites absorbs a very small amount of CO2. Therefore, a direct way of achieving this is to improve the absorption performance of CO2 in cement composites. In this study, to improve absorption, unlike in existing studies, a granulation technique was applied, and the material used was calcium hydroxide (CH). In addition, granulated CH was coated to prevent a reaction during the curing of cement paste. The coated CH granule (CCHG) was applied to 5% of the cement weight as an additive material, and the specimens were cured for 91 days to wait for the coating of CCHG to fully phase-change. The experiment of CO2 absorption showed an unexpected result, where the use of blast furnace slag (BFS) and fly ash (FA) had a negative effect on CO2 sequestration. This was because BFS and FA had a filler effect in the cement matrix, and the filler effect caused the blocking of the path of CO2. In addition, BFS and FA are well-known pozzolanic materials; the pozzolan reaction caused a reduction in the amount of CH because the pozzolan reaction consumed the CH to produce a calcium silicate hydrate. Therefore, the pozzolan reaction also had a negative effect on the CO2 sequestration performance combined with the filler effect. The CO2 sequestration efficiency was decreased between ordinary cement paste and BFS-applied specimens by 45.45%. In addition, compared to cases of ordinary cement paste and FA-applied specimens, the CO2 sequestration performance was decreased by 63.64%. Comprehensively, CO2 sequestration performance depends on the porosity and amount of CH.

“…They examined the influence of important factors, such as the width to thickness ratio of piezoelectric ceramics, volume fraction of piezoelectric ceramics, different matrix and functional bodies, mixing amount, curing temperature, and humidity, on the piezoelectric and dielectric properties of the three types of piezoelectric composites. Pan, Chaipanich et al [ 16 , 17 , 18 ] examined the influence of the content of cement-based piezoelectric materials, such as graphene and carbon nanotubes/clay, on the piezoelectric, thermal, and mechanical properties and hydration. Cement-based piezoelectric sensors and PZT sensors have been used to monitor the stress–strain relationships of concrete based on electromechanical impedance.…”

Section: Introductionmentioning

confidence: 99%

Construction of 2-2 Type Cement-Based Piezoelectric Composites’ Mechanic–Electric Relationship Based on Strain Rate Dependence

Dong

Zhu

et al. 2023

It has been found that the mechanic–electric response of cement-based piezoelectric composites under impact loading is nonlinear. Herein, we prepared a 2-2 cement-based piezoelectric composite material using cutting, pouring, and re-cutting. Then, we obtained the stress–strain and stress–electric displacement curves for this piezoelectric composite under impact loading using a modified split Hopkinson pressure bar (SHPB) experimental apparatus and an additional electrical output measurement system. Based on the micromechanics of the composite materials, we assumed that damage occurred only in the cement paste. The mechanical response relationship of the piezoelectric composite was calculated as the product of the viscoelastic constitutive relationship of the cement paste and a constant, where the constant was determined based on the reinforcement properties of the mechanical response of the piezoelectric composite. Using a modified nonlinear viscoelastic Zhu–Wang–Tang (ZWT) model, we characterized the stress–strain curves of the piezoelectric composite with different strain rates. The dynamic sensitivity and stress threshold of the linear response of the samples were calibrated and fitted. Thus, a mechanic–electric response equation was established for the 2-2 type cement-based piezoelectric composite considering the strain rate effects.