Non-destructive Ultrasonic Pulse Velocity Research Articles

Ensaios não destrutivos para avaliação do desempenho de concreto autocicatrizante por adição de microcápsulas contendo metacrilato de metila

Abstract The objective of this work was to develop a chemical admixture to make concrete capable to heal its fissures autonomously and, consequently, mitigate the concrete’s reinforcement corrosion due to the ingress of aggressive agents. For that, polymeric microcapsules built by a shell of urea-formaldehyde-melamine (UFM) and a core of methylmethacrylate were developed and added to the concrete to further evaluation. The concrete specimens containing 0%, 3% and 6% of the proposed microcapsules (mass of microcapsules / mass of cement) were subjected to destructive and non-destructive tests. The water absorption and the mechanical tests i.e., compressive strength and indirect tensile strength (Brazilian test) were carried out to characterize concrete, while the electrochemical impedance spectroscopy (EIS) and the non-destructive ultrasonic pulse velocity (UPV) tests were conducted to evaluate the concrete self-healing ability. These tests showed that the proposed admixture was able to heal the concrete’s fissures partially. In addition, it was concluded that the samples with 3% of microcapsules presented higher self-repairing rates. Despite the microcapsules developed in this work have presented a satisfactory self-healing efficiency, their effectiveness looks to be affected by the mixing procedure once part of them is broken during the process.

Quantification of Effective Flow Resistivity for Parametric Assessment of Pervious Concrete by Using Ultrasonic Pulse Velocity Method

The use of nondestructive ultrasonic pulse velocity (UPV) testing to assess the hardened properties of pervious concrete (PC) mixtures is an emerging research area. Further, UPV has been successfully used to determine the effective flow resistivity (EFR) of asphalt concrete and cement concrete pavements. However, no research studies have focused on understanding PC characteristics using EFR. Thus, the major objectives of this study were to assess the suitability of UPV testing for characterizing PC mixtures and to quantify their EFR, which is a measure of the material’s characteristic impedance and is dependent on the mix variables along with porosity. Thirty-six control and sand-modified PC mixtures were prepared with four aggregate gradations, and three levels each of water-to-cement (w/c) and aggregate-to-cement (a/c) ratios. Test results indicated that EFR was significantly dependent on the mix variables, with aggregate gradation being the most influential factor (six and eight times higher than w/c and a/c ratios, respectively). Lower EFR or higher sound absorption capacity was reported for PC with higher porosities. The sand-modified PC mixtures had higher EFR (by 4%–12%) than the control PC, and consequently lower sound absorption capacity, attributed to the presence of mortar that densified the mixes. Further, good-to-excellent correlations were obtained for various PC properties with UPV and EFR, which underscored the potential of UPV in characterizing PC. The major contribution of this research was the development of a simple, fast, and cost-effective approach, which can be suitably adopted as a quality-control test to determine PC mixture properties.

Cationic asphalt emulsion as an additive of RCC Pavement: Exploring for Mode-I fracture behavior and dynamic modulus properties

So far, several studies with the aim of investigating the feasibility of applying emulsified asphalt as an additive in the different types of cement concrete have been conducted, of which the results show a promising performance. Nonetheless, a relevant study on the dynamic and cracking behavior of Roller Compacted Concrete (RCC) containing Cationic Emulsified Asphalt (CEA) have been seldom accomplished. Therefore, it paved a way for studying this issue by conducting experiments on cylindrical and semi-circular bending (SCB) specimens made with CEA contents of 0, 2, 4, 6, 8 and 10% by weight of cement. The SCB specimens were subjected to three-point bending test (mode-I fracture) to evaluate the effect of CEA on the fracture properties. The cylindrical specimens were subjected to dynamic modulus testing with sinusoidal loading/unloading with different frequencies (5, 2, 1, and 0.5 Hz) as per AASHTO T342 to assess the effect of CEA on the dynamic modulus. Non-destructive ultrasonic pulse velocity (UPV) test was also performed on the cylindrical specimens 200 × 100 mm, which were prepared by cutting 50 mm disc from two ends of the specimens. Applying multiple linear regression on experimental results, a set of models were thus developed for estimating mechanical properties based on UPV measurements at a 95% confidence level. Using ANOVA at a 5% significance level, the results revealed a significant decline in stress intensity factor and thereby cracking resistance following the addition of 4% or more CEA to the mixture. Adding 6% or more CEA significantly reduced the mixtures’ dynamic modulus but also significantly increased their fracture energy. Given that adding CEA and changing the loading frequency, respectively, had no significant impact on the mixtures’ phase angle and mechanical properties, it was concluded that the behavior of the RCC made with CEA additive remained within the linear elastic range.

Effects of Recycled Rubber Particles Incorporated as Partial Sand Replacement on Fresh and Hardened Properties of Cement-Based Concrete: Mechanical, Microstructural and Life Cycle Analyses.

Cement is one of the most valuable materials in today's society, as it is used in most construction developments known to mankind. However, the energy intensive process and significant environmental impacts related to the production of Ordinary Portland Cement have shown the importance of searching for more sustainable materials. Concrete uses different aggregates added to the cement binder to lower, not only cost, but other factors like environmental burden, while maintaining good mechanical properties. This study analyzes the properties of fresh and hardened concrete incorporating recycled rubber to replace fine aggregate. Locally sourced 2 mm diameter rubber was incorporated in a regular strength concrete matrix into three different replacement levels, i.e., 3%, 5%, and 10%. Compression, tensile, flexural, and modulus of elasticity of hardened concrete were carried out in specimens aged 7, 14, and 28 days. In addition, non-destructive ultrasonic pulse velocity and rebound number tests were only performed on specimens aged 28 days. Once the tests were carried out, the fresh and hardened concrete properties were obtained. Similarly, the compressive and flexural strengths had the exact relationship between the values obtained. On the other hand, the modulus of elasticity tends to decrease due to the presence of the rubber. Consequently, it is recommended not to develop mix designs with more than 5% rubber because it is not meaningfully affected. The fine aggregate can be partially replaced by the rubber, keeping almost the same performance compared with sand-only counterparts. In addition, the life cycle assessment showed a reduction of up to 40% in the global warming potential. In fact, the 15% recycled rubber concrete mix has a climate change indicator of approximately 245 kg of CO2 eq.

Experimental study on metakaolin and nano alumina based concrete

The purpose of the study was to better understand the impacts of adding to freshly produced concrete nanoparticles like nano alumina (NA) at concentrations of 1%, 1.25%, and 2%, as well as the advantageous cementitious (pozzolanic) substance metakaolin at concentrations of 10%, 15%, and 20%. In order to conduct the various tests on freshly formed concrete at intervals of 7 days, 14 days, and 28 days after proper curing, nano alumina and metakaolin were combined. Studies were done on concrete grade M30 to determine its split tensile strength, bending strength, and compression strength. The specimen is put through a non-destructive ultrasonic pulse velocity (UPV) test and a non-destructive rebound hammer test on hardened concrete after 90 days. In order to evaluate the consistency of the concrete specimen, the slump test is also carried out. All test results were compared to the data from normal concrete, and from this we conclude that, when compared to conventional concrete, the percentage of NA powder and metakaolin in modified concrete specimens enhances concrete's properties in both the hardened and fresh stages, including compression strength, bending strength, split tensile strength, and workability.

Study on anisotropy of 3D printing PVA fiber reinforced concrete using destructive and non-destructive testing methods

To further understand the mechanical properties and anisotropy characteristics of 3D printing PVA fiber reinforced concrete (PFRC). This study first obtained 3D printing PFRC mixes with superior mechanical properties through slump tests, penetration resistance tests, printability tests, and flexural tests. Second, the fiber reinforcement mechanisms and anisotropy characteristics of PFRC were analyzed by nondestructive ultrasonic pulse velocity tests, destructive mechanical property tests, and scanning electron microscope tests. Third, the correlation between mechanical properties and ultrasonic signals was analyzed, and the conversion criteria were further established. Moreover, the application range of conversion criteria was also determined. The test results showed that the optimum dosage of PVA fibers is 0.5 wt% for 3D printing FRPC, and the highest cube compressive strength and flexural strength are 98.2 MPa and 6.8 MPa, respectively. The mechanical properties and acoustics of 3D printed specimens showed significant anisotropy. The conversion criteria show a good agreement with the test data and are applicable to 3D printing fiber concrete with a small aggregate size.

VALORIZATION OF DIVERSE SIZES OF COAL BOTTOM ASH AS FINE AGGREGATE IN THE PERFORMANCE OF LIGHTWEIGHT FOAMED CONCRETE

In recent years, research work on the use of coal bottom ash (CBA) as a partial alternative for aggregate in concrete is on the rise. This research is aimed at examining the characteristics of lightweight foamed concrete with CBA as fine aggregate to produce environmentally sustainable product. With the volume replacement technique, CBA was used as 25%, 50%, 75%, and 100% replacement for conventional mining sand with different sieve sizes of smaller than 4.75, 2.36, and 0.6 mm in concrete. Water absorption, porosity as well as mechanical characteristics tests, including compressive strength, splitting tensile strength, and modulus of elasticity (MOE) were conducted and analyzed. X-ray diffraction and scanning electron microscopy microstructural investigations were also performed to correlate test results. The quality of concrete was investigated using a non-destructive ultrasonic pulse velocity test. According to the findings, the highest replacement level of CBA with a sieve size smaller than 0.6 mm had an impact in reducing workability. The effect of CBA particles on water absorption, MOE, compressive strength, and tensile strength depends on the size of the fine aggregate, the replacement ratio and the density. In general, substituting mining sand with CBA aggregate improved the mechanical performance of concrete, notably for the aggregate size of less than 0.6 mm. Moreover, the SEM images indicate that the addition of CBA particles decreased the size and quantity of voids in the foamed concrete.

Compressive strength assessment of high strength concrete after fire using ultrasonic test method

This paper aims to evaluate the non-destructive ultrasonic pulse velocity (UPV) test method for determining the compressive strength of high strength of concrete (HSC) after fire. The compressive strength was determined through destructive cylinder test and by measuring ultrasonic pulse velocity. A total of 10 equations that relate compressive strength of concrete to UPV were evaluated in a total of 20 concrete samples. None of the equations were well suited for the case of HSC. The paper proposed a new equation and the UPV test showed suitable to assessment post-fire damaged HSC.

Evaluation of Concrete by Non-destructive Ultrasonic Pulse Velocity Method

Concrete is a material whose properties depend on its initial formulation, its conditions of use, and its change over time depending on its environment and the different types of degradation that it is likely to undergo. Knowledge and monitoring of its various mechanical properties are therefore essential for the maintenance of civil engineering works. All of the concrete assessment methods, whether destructive or non-destructive, can then provide a valuable diagnosis to the operators of the structure. Depending on their precision, they can be used to easily detect an alteration in the characteristics of the materials, locate a damaged area, the extent of the damage, or even precisely quantify the evolution of this damage over time and predict future changes. This paper presents the Ultrasonic Pulse Velocity technique (UPV) which is used by many companies to assess the compressive strength of concrete in situ and which allows measuring the speed and attenuation of elastic waves. The influence of the reinforcements on the ultrasonic pulse velocity has been studied and this is in the case of reinforcement perpendicular and parallel to the direction of propagation. The influence of several factors affecting the UPV, whether related to the properties of concrete or otherwise, was mentioned. Indeed, the porosity, the water/Cement ratio, the micro-cracks, the state of saturation and the temperature of concrete are parameters which strongly influence the values of UPV.

Monitoring the curing process of in-situ concrete with piezoelectric-based techniques – A practical application

The stiffness and strength properties of freshly poured concrete develop over time as the concrete hardens due to curing. The monitoring of such properties therefore enables timely construction decisions such as formwork removal. Traditional point-in-time destructive tests can be cumbersome, while continuous non-destructive testing is desirable. Piezoelectric-based electromechanical impedance (EMI) and wave propagation (WP) techniques fall into the latter, and they have been verified for monitoring concrete properties during curing in the laboratory. This paper reports the first field application of the EMI and WP techniques for monitoring concrete curing, where smart aggregate (SA) sensors are embedded into concrete pour strips of a multi-storey residential building during construction. For comparison and verification purposes, destructive compression and non-destructive ultrasonic pulse velocity (UPV) tests were conducted. Results obtained from both EMI and WP techniques were consistent and repeatable. They were also comparable to the UPV result, and they showed a close correlation to the compressive strength tests. The current study has also revealed that the electrical signatures acquired from the EMI and WP techniques have a linear relationship. EMI-based and WP-based semi-analytical models (and their derivations) that can quantify the compressive strength and modulus of elasticity of concrete at various curing durations are also presented. This reported study ultimately demonstrates the applicability and practical application of the EMI and WP techniques for real-time measurements, bridging the gap between laboratory-based studies and field applications.

Mechanical characteristics of experimental multi-scale steel fiber reinforced polymer concrete and optimization by Taguchi methods

Polymer Concrete (PC) has been widely used in reinforced concrete structures over the past few decades. Despite that, few studies have performed on its mechanical behavior. The present work investigates the PC mechanical behavior. Polymer concrete mixes were prepared and tested with three different polymer content (10%, 15% and 20%) and two filler contents (20% and 30%) and three different content of steel fiber (0.5%, 1% and 2%). In this study used the mix of cement and Micro-Silica as the filler. Afterward, Taguchi method and analysis of variance (ANOVA) were used to optimize the polymer concrete mix design based on the results of compressive strength, tensile strength and flexural strength in different percentages of polymer and fiber contents. Non-destructive ultrasonic pulse velocity test was also performed to estimate the porosity of the specimens. Scanning electron microscope (SEM) was used to analyze the interface between the aggregates and the polymer, the microstructure phase and the pores in the polymer concrete structure. Experimental results show that increasing the percentage of polymer content from 10 to 15% improves the mechanical properties of polymer concrete, while increasing this polymer content by up to 20% reduces the mechanical properties of the polymer composite. Based on non-destructive tests (NDT), it was found that increasing the content of cement and micro-silica reduces the porosity of the specimens. Moreover, as the content of steel fibers increases, the ductility and energy absorption of the specimens increase. At the end of this study, two functions were proposed to predict the mechanical properties of PC.

Dynamic modulus of elasticity and compressive strength evaluations of modified reactive powder concrete (MRPC) by non-destructive ultrasonic pulse velocity method

ABSTRACT This study investigates the method of ultrasonic pulse velocity technique as a non-destructive test for concrete to estimate the mechanical properties of RPC, modified reactive powders concrete (MRPC). This study is based on data obtained from the experimental investigation done in this work and comparison with the data of previous works. After conducting pulse velocity tests on cubic samples, the relationship between pulse velocity, elastic modulus and compressive strength of samples was obtained with an acceptable approximation. Also, the validity of the proposed relation ACI 363.1 and four distinguished researchers regarding the calculation of RPC, MRPC elastic modulus and its comparison with the dynamic elasticity modulus (ASTM C 597) with respect to different materials and mix designs. The dynamic modulus of elasticity (Ed) increased on average by 19% over the modulus of elasticity (Ec). Given the lack of research on the relationship between the parameters mentioned in the MRPC, the present study is an exploratory research concerned with the relationship of these methods. Also, two new models are presented for relating these parameters.

An intelligent model for the prediction of the compressive strength of cementitious composites with ground granulated blast furnace slag based on ultrasonic pulse velocity measurements

In this study, the compressive strength of cementitious composite containing ground granulated blast furnace slag (GGBFS) has been predicted. For this purpose, the intelligent models: the self-organizing feature map (SOFM) and the artificial neural network (ANN) were used and compared. A database containing 84 sets of data was created based on the time and mixture proportions of concrete, as well as on nondestructive ultrasonic pulse velocity measurements. It was proved that the developed model of predicting the compressive strength of the green cementitious composites containing GGBFS was accurate. It was also simple as it contained only three parameters that were used as input variables. The novelty of this research is the fact that they can be performed on existing structures, not only after 28 days, but also at early ages (3 and 7 days) and much longer periods (after 150 and 180 days). This makes this method more universal and increases the possibility of it being useful for construction practice.

A non destructive testing method for masonry by using UPV and cross validation procedure

The paper presents a new procedure to assess the compressive strength of regular masonry starting from results of non-destructive ultrasonic pulse velocity tests (UPV) on the constituent materials. The procedure has been calibrated on a soft calcarenitic stone used in the heritage masonry of Southern Italy, and starts from the knowledge of the regression between UPV and the compressive strength (UCS) of the material, determined by means of a wide experimental campaign on different varieties of quarry samples. Through an improved cross validation technique, the proposed method allows to estimate the compressive strength of new samples by making only non-destructive measurements without the need to conduct compression tests. The quality of the procedure was assessed both at the block scale and at the wall scale by comparing the estimated results with those obtained experimentally. In particular, the experiments were performed using new quarry stone blocks and blocks taken from existing walls of two ancient buildings during restoration works. The proposed method has proven to be reliable for the investigated material and it is easy to apply also for other materials as soon as it is possible to carry out a preliminary calibration in the laboratory, which allows knowing the UPV–UCS relationship over a wide range of strengths.

Rheology-based determination of injectable grout fluidity for preplaced aggregate concrete using ultrasonic tomography

With the increasing use of preplaced aggregate concrete in construction, the grout filling in preplaced aggregate concrete is important for ensuring proper consolidation and high mechanical performance. This paper proposes a framework for determining the injectable grout fluidity for preplaced aggregate concrete according to the rheological properties of the grout mixture, which are associated with the filling performance for the given aggregates. To assess the grout filling, cost-effective, nondestructive ultrasonic pulse velocity (UPV) testing was performed, and ultrasonic tomography images were constructed for visually identifying internal air voids, which were verified by high-resolution micro-computed tomography. Rheometer tests evaluated the rheological properties of the grout mixtures. The UPV-based void-detection results and grout rheological properties were employed to determine the injectable grout fluidity range.

Mechanical behaviour of structural concrete with ground recycled concrete cement and mixed recycled aggregate

This article analyses the combined effect of valorising ground recycled concrete (GRC) as 10% or 25% cement replacement and 0% or 50% mixed recycled construction and demolition waste aggregate (RA-CDW) in structural concrete. An exhaustive experimental programme was designed to assess the variation in compressive and tensile strength, modulus of elasticity and hardened concrete density. Non-destructive ultrasonic pulse velocity and electrical resistivity tests were also conducted. The concrete mixes prepared with GRC and RA-CDW exhibited lower mechanical performance than those manufactured with natural aggregate and cement only (although the difference was smaller than the respective replacement ratios). These findings were attributed to: a higher water/binder (cement + GRC) ratio, the dilution effect resulting from a lower cement content in the new mixes and the intrinsic properties (water absorption and abrasion resistance) of the new recycled components. The mixes with 10% GRC and 50% RA-CDW, however, showed similar mechanical performance and remained in the same strength class as those with 50% RA-CDW and 100% Portland cement. In terms of the electrical resistivity and ultrasonic pulse velocity tests, the effect of replacing OPC with GRC was below 14%, irrespective of whether natural or recycled aggregates were used. Such promising findings pave the way for more efficient and global C&DW management with a view to steering the construction industry toward the circular economy.

Setting time and compressive strength prediction model of concrete by nondestructive ultrasonic pulse velocity testing at early age

This study proposes a new model for estimating the setting and compressive strength development times, which involve changes in the concrete condition at early ages, using the ultrasonic pulse velocity testing. To this end, various effects, such as the effects of the water-to-cement (W/C) ratio, curing conditions (air-dry curing and curing at constant temperature and humidity), and aggregate, were experimentally examined to meet the specified concrete strength, i.e., 18–45 MPa. We found that varied as the W/C ratio of concrete decreased, which are affected by the hydration reaction, and that the ultrasonic pulse velocity was somewhat higher in concrete than in mortar. The samples cured under constant temperature and humidity exhibited a smaller error range than those that underwent air-dry curing. In addition, the relationships among parameters in different concrete samples were found to be linear during the initial and final setting periods and parabolic after the final set at early ages; subsequently, an exponential function prediction model was proposed for modeling the relationships.

About the Possible Limitations in the Usage of the Non-Destructive Ultrasonic Pulse Velocity Method for Assessment of Cracks in Reinforced Concrete Structures, Subjected to Direct Environmental Exposure

Failures occur in the structures of reinforced concrete buildings and facilities during their continuous exploitation, without being overloaded or exposed to extreme impacts, the most common being cracks. Their detection and change in time are related to the assessment of the state of the structures, their safety, and reliability during their construction and especially for their safety exploitation. This paper describes the results of the experimental studies conducted by authors aiming to verify the possibility of using the non-destructive ultrasonic pulse velocity method (NDUPVM) for detection and evaluation of cracks. Results of an experimental study of 12 reinforced concrete beams are presented. In previous experiments, some of them were subjected to bending until the maximum crack width of 0.3 mm was reached and others until yielding of the longitudinal reinforcement. The results obtained from the measurements of the depths of the normal cracks with different widths with NDUPVM were compared with the visually measured ones. In the present research cracks with the same width and with a similar depth were chosen. The influence of extreme external conditions to the accuracy of the measured crack depths by the NDUPVM was investigated. Non-destructive ultrasonic research was done by a portable device Proceq TICO.

Investigating the Utilization of Ground Palm Kernel Shells for Partial Replacement of Cement in Concrete Using Nondestructive Method

The objective of this research is to investigate the utilization of palm kernel shells in ground form (GPK) for partial replacement of ordinary Portland cement (OPC) in concrete by investigating its optimal strength using nondestructive ultrasonic pulse velocity method for both cubic and cylindrical concrete test specimen. In all a total of 135 cubes and 66 cylinders of concrete were prepared. The dimension of the cubic concrete specimens was 150 × 150 × 150 mm and that of the cylindrical specimens were 110 mm and 500 mm diameter and length respectively. The mix design of the GPK shells used as a partial replacement for OPC ranged between 0% and 50% by weight of cement using mix ratio of 1:2:4 with water to cement ratio of 0.8. The concrete specimens were test at curing periods of 7 days, 28 days and 60 days for the cubes and 7 days and 28 days for the cylinders. Based on the results and the analysis done, it was generally observed in all cases that, as the mix ratio is increased, the ultrasonic pulse velocity, modulus of elasticity and the density decreased and as the curing period increased, these values increased across all the mix ratios. The ultrasonic pulse velocity and the density of the specimens shows that concretes containing GPK “fuel” shells has higher values than those containing GPK ordinary shells. Generally, the density, ultrasonic pulse velocity and the modulus of elasticity of concrete containing GPK shells decrease as the replacement percentage increase.

Mechanical properties soil stabilized with nano calcium carbonate and reinforced with carpet waste fibers

Abstract One of the geotechnical engineering strategies for dealing with weak soils in a construction site is to alter their mechanical properties with the assistance of soil improvement techniques. The present study examined the effect of the addition of nano calcium carbonate (0, 0.4, 0.8 and 1.2% by weight of the soil) as a stabilizing nanoparticle and carpet waste fibers (0, 0.2, 0.4, and 0.6% by weight of the soil) as a reinforcement agent on the soil behavior. A total of 52 unconfined compressive strength tests, 52 ultrasonic pulse velocity tests, 12 unconsolidated undrained (UU) triaxial tests, and 8 Atterberg limit tests were performed to investigate the effect of fiber and nanoparticle contents and treatment time on the geotechnical properties of the clayey soil. The results showed that the addition of nanoparticles to the clayey soil reduces its liquid limit and increases its plastic limit. The best improvement in the soil strength, which was about 100%, was observed in the 42 days old sample with 1.2% nano calcium carbonate content. The combined use of fibers and nanoparticles also led to significant strength improvement. The addition of carpet waste fiber was found to increase the soil stiffness. Increasing the carpet waste fiber content above the 0.2% did not have much impact on the maximum strength, but significantly improved the residual strength. The addition of carpet waste fibers up to 0.2% increased the velocity of ultrasonic waves, but further increase in the fiber content resulted in reduced velocity. The paper provides a number of equations that express the relationship between the unconfined compressive strength and the ultrasonic pulse velocity for the clayey soils with different additive contents. The provided equations can be used to estimate the success of stabilization and strength improvement efforts based on the results of non-destructive ultrasonic pulse velocity test. The results of unconsolidated undrained triaxial tests showed that the used fibers alter the sample behavior in high strains. Also, the use of nano calcium carbonate and carpet waste fibers together almost doubled the undrained cohesion.