Non-destructive evaluation of eco-friendly cementitious materials by ultrasound (original) (raw)
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Application of Ultrasonic Measurements for Determination of Setting and Hardening in Cement Paste
Journal of Civil Engineering and Architecture, 2011
Concrete setting and hardening processes are the most critical phases during construction works, influencing properties of a concrete structure. The initial set is important as it provides an estimate when concrete has reached a point that it can no longer be vibrated without damaging concrete. The point at which final set occurs is important since it provides an estimate when the development of concrete strength and stiffness starts. In this study, experimental work is performed under laboratory conditions to indentify the setting time of cement paste using ultrasonic waves. Correlation between the ultrasonic wave parameters (speed, amplitude and energy) passing through the fresh cement paste and setting time determined using the Vicat test method is analyzed. A method of acoustic emission is also used and acoustic signals recorded in cement paste during hydration are presented.
Cement and Concrete Research, 2009
This paper presents the comparison between ultrasonic wave transmission (USWT) method and ultrasonic wave reflection (USWR) method in their ability to monitor the setting process of cement pastes. The velocity of ultrasonic longitudinal waves and shear wave reflection coefficient were measured simultaneously on cement pastes with different hydration kinetics. Even though both methods are able to reliably monitor the hydration process and formation of structure of an arbitrary cement paste, they monitor the setting process in different ways. The relationship between the velocity of longitudinal waves and shear wave reflection coefficient can be simplified into three characteristic phases and the end of the first phase can be used to define the beginning of the setting process of cement paste.
NDT & E International, 2013
In the paper a new setup for measuring setting and hardening process of cementitious materials, using a non-destructive ultrasonic shear wave reflection technique and designed with the objective to be easily used in-situ, is described. Using the developed setup, the measurements can be performed by slight deepening of a measuring head into a paste in a mold or by placing the paste into a mold fixed on a measuring head. To test the proposed methodology, cement pastes with different compositions were prepared and exposed to different curing temperatures. Significant differences in the evolution of a change of a shear wave reflection coefficient Δr in time were observed, indicating ability of the method to monitor setting process of cement pastes. Moreover, some interesting phenomena in the solidification process of the materials can be identified. A linear relationship between development of the Δr and penetration resistance d P values in time was found, allowing development of a simplified procedure to determine both initial and final setting times of the material.
Ultrasonic assessment of early-age changes in the material properties of cementitious materials
Materials and Structures, 2007
After casting, cementitious materials exhibit a continuous change in the mechanical properties with time due to a chemical reaction known as hydration. In addition, these materials also exhibit a change in state, from a fluid to a solid, in the first few hours. Conventionally, changes in the material properties are obtained by monitoring the visco-elastic moduli with time before setting and the increase in the elastic material properties of the solid cementitious material, after setting. An ultrasonic test setup and the data analysis procedures, which provide for continuous monitoring of the hydrating cementitious materials from a very early age through setting are presented in this paper. The test procedures for obtaining the ultrasonic test data and the inversion subroutines for assessing the material properties of the cementitious material at different stages of hydration are discussed. The experimental test results obtained from mortar mixtures of varying compositions are presented. The observed experimental trends are explained considering wave propagation in viscoelastic materials. There is a two-stage increase in the value of shear modulus of mortar with time. Experimental evidence suggests that initially there is a larger relative increase in the viscous component of the shear
Effects of air voids on ultrasonic wave propagation in early age cement pastes
2011
The objective of this paper is to investigate effects of air voids on ultrasonic wave propagation in fresh cement pastes, and relate ultrasonic wave parameters to cement setting times. First, Biot's theory was used to analyze wave propagation in poroelastic media containing air bubbles. Then, in the experimental study, both the compressional (P) and shear (S) waves were monitored in cement pastes with different water/cement ratios (w/c = 0.4 and 0.5) and various air void content (0.1%-5.3% by cement paste volume). Experimental results indicated that existence of air bubbles in cement paste significantly decreases the P wave velocity, but has little effect on the shear wave propagation. Further analysis shows that the shear wave velocity corresponding to the Vicat initial setting times is a relatively constant value for the investigated air content range. This study shows the potential of using shear waves to monitor setting and hardening process of cement.
Ultrasonic assessment of initial compressive strength gain of cement based materials
Cement and Concrete Research, 2015
In this paper, a possibility of using frequency spectrum of ultrasonic P-waves to determine very early age compressive strength (fc) of cement based materials (CBMs) is analyzed. TG parameter, representing the ratio between maximum amplitudes of high and low frequency ranges that appear in the frequency spectrum of the transmitted signal, is used to observe the changes in the spectrum. Both fc and TG start to increase simultaneously and later develop according to similar trend. Thus, strong correlation between fc and TG is established, regardless of the CBM's composition. By comparing stress-strain curves and time derivatives of TG-t curves, the stage when the material is clearly plastic and stage when material exhibits solid behavior, can be distinguished. These results explain physical meaning of TG parameter in more detail and expand the range of practical applications of methods based on spectral analysis of transmitted P-waves.
Utilization of the ultrasonic method to evaluate the properties of high performance concrete
Revista IBRACON de Estruturas e Materiais, 2010
O presente trabalho trata da utilização do método ultra-sônico para avaliar a desempenho do concreto de alto desempenho. As propriedades mecânicas avaliadas foram a resistência à compressão e o módulo de elasticidade. Com respeito ao módulo, foi feito um estudo comparativo en- tre os resultados obtidos com o aparelho de ultra-som e com extensômetros colados. Os resultados obtidos em ambos os ensaios foram também contrastados com os valores previstos de acordo com o CEB 90 [1] e a NBR 6118 [2]. Através desse estudo se verificou que as leituras realizadas com o método ultra-sônico são sensíveis às variações das propriedades mecânicas. Por outro lado, a análise comparativa do módulo de elasticidade mostrou que é possível estimar o seu valor por meio dos resultados obtidos com o aparelho de ultra-som.
EVALUATION OF CEMENT MORTARS BY ULTRASOUND
ndt.net
Most of the concrete properties are affected by the cement and the mechanical as well as some durability properties of cements are determined through cement mortars. However, applications of ultrasound on determining the properties of cement mortars are quite limited. Therefore, the required specimen dimensions, transducer frequencies have not yet been established for cement mortars. In this study, ultrasonic pulse velocity (UPV) of mortars was determined with different transducers of different frequencies for different size and shape of specimens and the relations between UPV and various properties of cement mortars were investigated. Within the scope of the experimental program, three different ultrasonic frequencies (54, 82, and 150 kHz) were utilized. For this purpose, mortar mixtures were prepared with various water-to-cement ratios having a constant cement content of 500 kg/m 3 . From each mortar mixture, cubical and prismatic specimens of various sizes were prepared. It was concluded that when the effect of specimen geometry on the UPV of mortars were considered, as the path length increases there is a significant reduction in the measured UPV, and when the length/wavelength ratio increases, the measured UPV with different transducer frequencies tends to converge to a single value. It was also observed that the linear relationship that exists between the compressive strength and UPV varies, as the age of mortar increases.
Using Ultrasonic Waves to Detect Basic Properties of Portland Cement Concrete
An experimental study was conducted to investigate the feasibility ofusing ultrasonic waves to detect the basic properties of Portland cement concrete (PCC). The experimental programme was initiated to investigate the effect of watercement ratio (w/c), aggregate type, air entrainment, and curing time on measured ultrasonic wave velocity and signal energy. Three wlc ratios (0.35, 0.45 and 0.55) were evaluated. Two aggregate types (quartzite and limestone) were included in the PCC mixes separately. Mixes were prepared as non-air entrained and with air entrainment. Thus, a total of twelve batches were prepared. Ultrasonic measurements were performed on 7.5 x 10 x 40 em PCC specimens at 1, 3, 7, 14,21, and 28 days of moist curing using direct and indirect measuring methods. Ultrasonic waves were used at two frequencies, 54 and 340 kHz. Collected data was analysed based on ultrasonic wave velocity and signal energy.