Abstract
The obtained physico-mechanical properties (mainly flexural and compressive strength) of cement-based composite materials depend on various factors (type of mixture, its composition, standard hardening process, proper testing, handling during transportation, etc.). Important properties to be tested include in particular properties of materials in the fresh, still plastic, state, since accurate identification of defects in building materials/structures at the early stage will allow early elimination and minimization of their future consequences. The aim of this paper is the application of the acoustic emission (AE) method for the detection of high-frequency elastic waves created by physical and chemical processes accompanying setting and hardening of cement pastes. The experiment was conducted on cement pastes produced from different cements but with the same water/cement ratio. Since there are many possible sources of AE and the identification of the individual sources is difficult, the monitoring of the setting cement paste was conducted simultaneously with measurements of the internal temperature. The results of these experiments can be used to expand the understanding of the various processes occurring at the early stage of setting and hardening of cement-based materials.
Highlights
The acoustic emission (AE) method is a non-destructive method (NDT) widely employed to detect damage and defects in building materials or structures
The graphs (Figure 2) show the number of acoustic emission counts (NAE) and the temperature curve (ΔT is the difference between the internal temperature in the sample and the ambient temperature in the laboratory) recorded for the cement pastes ageing under autogenous conditions
The paper presents the results of an experiment dealing with the use of the AE method for monitoring of the early stage of setting and hardening of cement pastes ageing under autogenous conditions
Summary
The acoustic emission (AE) method is a non-destructive method (NDT) widely employed to detect damage and defects in building materials or structures. The principle of the measurement is based on monitoring of released portions of accumulated elastic energy resulting from dynamic processes that may be induced by external as well as internal forces. Monitoring of structures with the AE method is unique, non-invasive and passive. The AE parameters are influenced by the type of load as well as by the material characteristics of the investigated element or structure. The composition of the material itself, i.e. maximum aggregate size, aggregate/binder ratio, or the porosity of the internal structure of the investigated materials, is a significant influence. Conditions to be met for successful implementation of the AE method include a thorough understanding of the physical background of the principle of the AE generation by ongoing processes, awareness of the limitations rooting from the random propagation and origin of AE, and the limitations given by the specific technical design of the measuring apparatus and the AE sensors, e.g. their correct calibration [5, 6, 7, 8]
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