Pulse Velocity Values Research Articles

Effect of polymer latex on the efflorescence, drying shrinkage and microstructure of alkali-activated slag paste

This study investigated the performance of alkali-activated slag (AAS) paste modified with different levels of styrene-acrylic resin (SAR) polymer latex. The AAS paste samples were prepared using GGBFS of two different fineness levels and NaOH solutions with respective molarities of 10 M, 12 M, and 14 M. Polymer latex was added at levels of 2.5%, 5%, and 7.5% of GGBFS weight. The AAS paste with fine GGBFS and NaOH 12 M performed the better strength than that with coarse GGBFS. The AAS paste samples modified with SAR polymer latex up to 5% exhibited slightly increased compressive strength results but reduced the ultrasonic pulse velocity (UPV) values. Furthermore, the addition of polymer latex enhanced the microstructure and significantly reduced efflorescence and drying shrinkage results. C-(A)-S-H gel and hydrotalcite phase were the main reaction products of both the latex-free and latex-modified AAS paste samples, with no new reaction products generated by the addition of polymer latex.

Evaluation of Corrosion Damage in Sulfate-Attacked Concrete by CT, Ultrasonic Pulse Velocity Testing and AHP Methods

Coarse aggregate in concrete is basically free from sulfate corrosion. If the influence of the coarse aggregate in the concrete is not eliminated, the change amount of the concrete ultrasonic pulse velocity value is directly used to evaluate the damage degree of sulfate corrosion in the concrete, and the results are often inaccurate. This paper presents an evaluation method of corrosion damage for the sulfate-attacked concrete by CT, ultrasonic velocity testing and AHP methods. CT was used to extract the coarse aggregate information in the specimen, and the proportion of coarse aggregate on the ultrasonic test line was calculated based on CT image analysis. Then, the correction value of ultrasonic pulse velocity (UPV) of the concrete structure was calculated, and the sulfate corrosion degree of concrete structure was evaluated using the analytic hierarchy process (AHP). The results show that the evaluation method proposed in this paper could more accurately evaluate the corrosion damage in the sulfate-attacked concrete structures, and the evaluation results were more in line with reality.

Waste incineration bottom ash as a fine aggregate in mortar: An assessment of engineering properties, durability, and microstructure

This study was developed to investigate the potential re-utilization of waste incineration bottom ash (IBA) sourced from Southern Vietnam as a replacement for natural crushed sand in cement-based mortars. In this study, all of the mortar mixtures were designed using the novel densified mixture design algorithm with a detailed step-by-step standard operating procedure and an empirical example of the calculation. Changes in the engineering properties (i.e., flowability, fresh unit weight, compressive strength, bending strength, and drying shrinkage), durability (i.e., porosity, water absorption, chloride ion penetration, ultrasonic pulse velocity, and resistance to sulfate attack), and microstructure of the mortars were systematically evaluated using mortar specimens produced with five different IBA replacement levels of 0, 25, 50, 75, and 100% (by volume). Moreover, the correlations among these several mortar properties were established and discussed. The experimental results indicate that the IBA replacement level significantly affects the properties of mortars in both fresh and hardened stages. Increasing the IBA replacement level was found to increase porosity, water absorption, and drying shrinkage and to reduce compressive and bending strengths in the mortar specimens. Moreover, increasing the IBA replacement level reduced resistance to sulfate attack. However, all of the proposed mortars exhibited very good chloride penetration resistance and good quality, with chloride ion penetration and ultrasonic pulse velocity values ranging from 355 to 638 Coulombs and 3483–4416 m/s, respectively, at 56 days of curing age.

Evaluation of ultrasonic pulse velocity (UPV) for reinforced concrete corrosion

This study was undertaken to evaluate the efficiency of the ultrasonic test for detecting reinforcement corrosion levels under varying conditions and to form a correlation between the ultrasonic pulse velocity (UPV) values and the flexural capacity of corroded beams. To establish this, several reinforced concrete beams were cast and subjected to an impressed current accelerated corrosion process. The severity of corrosion was then investigated using the UPV test and four-point loading test. The results showed that the UPV test values vary with the corrosion level of reinforcement in concrete beams. However, the degree of variation in UPV test values at different levels of corrosion does not permit a clear cut for the evaluation of corrosion severity, particularly at low levels of corrosion. The four-point testing of corroded beams showed that corrosion affects the flexural capacity and ductility of the beams. This effect was correlated in this study with the UPV test values. The correlation analysis showed that there exists a moderate to a high positive correlation between the UPV test values and flexural capacity of the beams while a low negative correlation between the UPV test values and ductility of the beams was observed.

Predictability of concrete damage level by non-destructive test methods

Non-destructive methods have many advantages over traditional test methods, especially since it does not damage the specimen, it can be used multiple times on the same specimen. These advantages also provide a great benefit in terms of following the property development in concrete as the same specimens are used which eliminates the variations related to the specimens. In this study, it is aimed to determine the damaged amount of concrete produced with different binders by electrical bulk resistivity, resonance frequency, and ultrasonic pulse velocity methods. Firstly, concretes containing different binders were produced, and along with the mechanical properties, ultrasonic wave velocity, resonance frequency, and electrical resistivity values of the produced concrete were determined at the 7, 28, and 90 days. Besides, the specimens were subjected to gradually increase compressive loads and non-destructive methods were used to estimate the extent of damage on specimens. It was attempted to establish a relationship between the damage on concrete specimens and the results obtained by non-destructive methods. Consequently, the compressive strength, electrical resistivity, ultrasonic pulse velocity and resonance frequency values of all specimens increased with the advancing age. It was concluded that the resonant frequency method is more successful than other methods in estimating the amount of damage in concrete.

Influence of nano graphite platelets on the behavior of concrete with E-waste plastic coarse aggregates

Past works have used electronic waste (E-waste) plastic as a raw material for the production of plastic aggregate to be used as a substitute for natural aggregates. However, the results have shown that the plastic aggregate reduces the strength properties of resulting concrete limiting its application to non-structural components. Nano graphite platelets (NGPs) are nanofillers that significantly improve the density and hardness of the cementitious composite due to reduction in porosity and reinforcement in microstructure. In the current study, NGPs have been utilized to increase the strength of plastic concrete. The natural coarse aggregates are partially substituted by 25% of E-waste plastic coarse aggregate. Locally available NGPs are utilized, and their structural characteristics were assessed by scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) spectroscopy. A dispersion test is carried out and a ratio of 0.6:1 (surfactant:NGPs) is found to yield maximum dispersion. Different dosages of NGPs (1%, 3%, and 5%) have been introduced into plastic concrete. This research work aims to explore the fresh, mechanical, durability, and microstructure characteristics. The mechanical properties of the cementitious composites declined with the incorporation of E-waste plastic aggregates which were significantly enhanced by incorporating NGPs. The specimens containing 25% of plastic aggregate and 5% of NGPs showed the hardened density, compressive strength, tensile strength, and flexural strength to increase by 2.16%, 13.56%, 15.53%, and 31.42%, respectively compared to the samples without NGPs. Sorptivity and ultrasonic pulse velocity values are found to decrease by 56.5% and increase by 2.53%, respectively for plastic concrete with 5% NGPs compared to the control mix. SEM-EDX spectroscopy was carried out to examine microstructure investigation and it was found that by the inclusion of NGPs in the concrete composites, the hydrated crystals stacked one over the other and became massive and thicker implying that the addition of NGPs is a promising reinforcing agent in plastic concrete.

Engineering performance of sustainable geopolymer foamed and non-foamed concretes

This study investigates the effect of using palm oil fuel ash (POFA) as a partial replacement for fly ash (FA) in lightweight geopolymer foamed concrete and geopolymer mortar. Three different proportions of POFA contents of 10%, 20%, and 30% with a target fresh density of about 1300 ± 50 kg/m3, were used. The development of compressive strength and splitting tensile strength were investigated over a 28-day curing period. Transport properties, in terms of water absorption, porosity, and sorptivity, were also investigated. Microstructural characteristics through XRD, SEM and EDX were also investigated and reported. The results found that the compressive strength of geopolymer foamed concrete, with up to 30% POFA, was higher than the control; however, for the POFA-based geopolymer mortar, the compressive strength reduced with increasing POFA content. The highest compressive strength of 6.1 MPa was recorded in the geopolymer foamed concrete with 20% POFA, whereas the control mix of geopolymer mortar produced 36.6 MPa. The geopolymer foamed concrete achieved 70% of its 28-day compressive strength within 3 days. The oven-dry density of the geopolymer foamed concrete ranged from 1193-1344 kg/m3. The ultrasonic pulse velocity (UPV) value was 1.5 km/s for the geopolymer foamed concrete while the geopolymer mortar had the range of 2.2–2.4 km/s. In general, the transport properties were mostly dependent on the oven-dry density of the geopolymer foamed concrete. The POFA content of 20% was found to provide the required silica and alumina to produce geopolymerization gel. Further, the SEM images showed unreacted FA particles that led to an increase in the voids. Furthermore, the XRD patterns showed the addition of foam affected the intensity of the peaks.

The hybrid effects of basalt and PVA fiber on properties of a cementitious composite: Physical properties and non-destructive tests

This study aimed to experimentally examine the physical properties and non-destructive properties of cementitious composites for different hybrid basalt and PVA fiber contents. The total fiber content of 2% was formed with five different proportions of PVA fiber and basalt fiber. Within the scope of the experimental studies, various mechanical (compressive strength and elasticity modulus), durability (capillary water absorption and water absorption), physical (apparent void volume and bulk density), non-destructive (ultrasonic pulse velocity and Schmidt rebound hammer) and microstructural (scanning electron microscopy) tests were carried out to investigate the properties of the produced hybrid fiber reinforced composites. The results showed that the water absorption capacity and water absorption coefficient by capillarity values decreased while the hardened composite density values increased as the basalt fiber ratio increased in the mixtures. The maximum ultrasonic pulse velocity values were obtained from P0B100 (consisting of only 100% basalt fiber) samples with the highest Schmidt rebound hammer values of 4.11 km/s and 32, respectively.

Strength and flexural toughness of hybrid fibre reinforced fly ash based concrete

To overcome concrete brittleness and to provide toughness, fibre reinforcement is commonly utilized. Fibre reinforcement to concrete in the form of hybrid fibre is a new concept to achieve individual fibre benefits. In this paper, the effect of polypropylene fibre (PF) and steel fibre (SF) either individually or with different combinations at 1% fibre volume fraction on the strength, flexural toughness, and Ultrasonic pulse velocity (UPV) value of FIBRE-reinforced fly ash (FA) based concrete has been presented. For this purpose, one control mix having 25% FA and 0% fibre and five mixes with different hybrid fibre combinations of 1%PF-0%SF, 0.75%PF-0.25%SF%, 0.50%PF-0.50%SF, 0.25%PF-0.75%SF, and 0%PF-1%SF were cast. ASTM C 1609 method was utilized to evaluate the flexural toughness. Experimental results have shown an improvement in all the above-said properties (expect UPV) by the addition of fibre, but improvement is more significant in mixes with a higher percentage of SF when compared with mixes at a higher percentage of PF. Mix with a hybrid fibre combination of 0.25% PF and 0.75% SF gave the best result among all the fibre-reinforced fly ash-based mixes.

Manufacture and Engineering Properties of Cementitious Mortar Incorporating Unground Rice Husk Ash as Fine Aggregate

This study investigates the manufacture and engineering properties of cementitious mortar incorporating unground rice husk ash (URHA) as fine aggregate. Six mixtures of mortar were produced with using URHA to substitute for crushed sand in amounts of 0%, 20%, 40%, 60%, 80%, and 100% by volume at constant water-to-powder ratio of 0.6 and volume ratio of fine aggregate to powder of 2.5. The experimental series consisted of the flowability, density, water absorption, compressive strength, flexural strength, dynamic modulus of elasticity, ultrasonic pulse velocity, and scanning electron microscopy tested under relevant standards. The fresh and dried densities of mortar with URHA significantly reduced from 5% to 29% and from 8% to 39%, respectively, compared to mortar without URHA. The higher ratio of URHA to fine aggregate led to a darker color, and higher water absorption of cementitious mortar. Replacing of 20%–40% fine aggregate volume by URHA produced mortars with comparable compressive strength at later ages. The flexural strength, dynamic modulus of elasticity, and ultrasonic pulse velocity values of mortar presented the downtrend with increase of URHA content; however, the developing rate of these values was meaningfully promoted at later ages due to internal curing and pozzolanic action. The present study supported the technical feasibility and environmental friendliness of cementitious mortar produced with replacing the natural fine aggregate up to 100% in volume.

Effect of Hollow Corundum Microspheres Additive on Physical and Mechanical Properties and Thermal Shock Resistance Behavior of Bauxite Based Refractory Castable.

This paper analyses the effect of hollow corundum microspheres (HCM) on both physical-mechanical properties (density, ultrasonic pulse velocity, modulus of elasticity, and compressive strength) and thermal shock resistance behavior of refractory medium cement castable with bauxite aggregate. Moreover, the scanning electron microscopy (SEM) results of HCM and refractory castable samples are presented in the paper. It was found that the replacement of bauxite of 0–0.1 mm fraction by HCM (2.5%, 5%, and 10% by weight of dry mix) had no significant effect on the density and compressive strength of castable, while the modulus of elasticity decreased by 15%. Ultrasonic pulse velocity (Vup) values and the visual analysis of the samples after thermal cycling showed that a small amount of HCM in composition of refractory castable could reduce the formation and propagation of cracks and thus increase its thermal shock resistance.

Soft computing techniques for the prediction of concrete compressive strength using Non-Destructive tests

This study presents a comparative assessment of conventional soft computing techniques in estimating the compressive strength (CS) of concrete utilizing two non-destructive tests, namely ultrasonic pulse velocity and rebound hammer test. In specific, six conventional soft computing models namely back-propagation neural network (BPNN), relevance vector machine, minimax probability machine regression, genetic programming, Gaussian process regression, and multivariate adaptive regression spline, were used. To construct and validate these models, a total of 629 datasets were collected from the literature. Experimental results show that the BPNN attained the most accurate prediction of concrete CS based on both ultrasonic pulse velocity and rebound number values. The results of the employed MARS and BPNN models are significantly better than those obtained in earlier studies. Thus, these two models are very potential to assist engineers in the design phase of civil engineering projects to estimate the concrete CS with a greater accuracy level.

The Combined Effect of CKD and Silica Fume on the Mechanical and Durability Performance of Cement Mortar

To manufacture high-strength and high-performance concrete, the incorporation of silica fume with concrete was becoming popular nowadays. When utilizing various amounts of cement substitute products, the design becomes even more complicated. The latest research has been dedicated to researching the applicability of cement substitute products for cement kiln dust (CKD) and silica fume (SF). In permeability and compressive strength terms, the effect of these components on the efficacy of the concrete would be studied. Also, the materials proposed might limit greenhouse gas emissions, which will mitigate climate change on other causes of global pollution. Casting a standard concrete cube (100 percent OPC) equivalent to (150 gm) would initiate the experiment, which was utilized later for comparative purposes. The industrial waste materials (SF and CKD) was be applied as cement substitution proportions (10 percent, 20 percent, and 30 percent) of the dry cement weight at varying percentages of each component (5 percent, 10 percent, and 15 percent). Eventually, after 7, 14, 28 days, the compressive strength shift would be calculated. The permeability of the latest concrete will be checked after (7, 14, and 28) days of healing utilizing ultrasonic pulse velocity (UPV) technology. The experimental findings indicate that with a specimen comprising 20 percent of (SF and CKD) relative to (100 percent OPC) specimen, there is an improvement in compressive intensity and pulse velocity values in various curing times and specimens of various (SF and CKD) specimen M3 have a decrease in pulse velocity value after 7 curing days.

Salt weathering and ultrasonic pulse velocity: condition assessment of salt damaged porous limestone

Salt weathering is one of the crucial causes of building stone decay. For assessing the durability of stones against salt weathering, a standardised test procedure (EN 12370:2020 Determination of resistance to salt crystallisation) is used: the mass loss of the stone is measured during sodium sulphate crystallisation cycles. Porous, Miocene limestone test specimens collected from the Sóskút quarry (Hungary) were subjected to salt crystallisation cycles in laboratory conditions. The limestone with open porosities of up to 32 V% is composed of ooids, various types of bioclasts and other carbonate grains. Besides the classical measurements of mass changes, the ultrasonic pulse velocity was also recorded after each crystallisation cycle. The ultrasonic pulse velocity values of quarry stones and salt-laden porous limestone specimens were compared. The results indicate that when salt crystal clogs the pores, an increase in ultrasonic pulse velocity is observed. Additional salt crystallisation cycles reduce the pulse velocity. This negative shift in pulse velocities is linked to the opening of micro-cracks, indicating the damage of the studied limestone. Our tests have proved that ultrasonic pulse velocity testing device can detect salt crystallisation damage in a non-destructive way. Its application is recommended in the condition assessment of salt damaged stone heritage structures.

Effect of binder content and recycled concrete aggregate on freeze-thaw and sulfate resistance of GGBFS based geopolymer concretes

The use of waste materials in concrete production is important because of the recycling of these materials. In this context, the use of both geopolymer binder and recycled concrete aggregate (RCA) becomes important. For this purpose, in this study, ground granulated blast furnace slag (GGBFS) based geopolymer concrete containing RCA was designed and freeze–thaw (F-T) and sulfate resistance of these samples were determined. In the production of geopolymer concrete, three different binder contents (300, 400 and 500 kg/m3) and five different ratios of RCA (0, 25, 50, 75 and 100%) were used. Samples that completed curing period were exposed to 100F-T cycles and two sulfate solutions (3% MgSO4 and 1.5% Na2SO4 + 1.5% MgSO4). Compressive strength, ultrasonic pulse velocity (UPV), weight change and sorptivity values ​​of these samples were determined. At the same time, these results were interpreted together with microstructure analysis (SEM and EDS). An exponential relationship was found between Ca/Si and Si/Al ratios of the samples and their compressive strength. Increasing in Ca/Si ratio and decreasing in Si/Al ratio caused an increase in compressive strength. As the binder content amount increased, the resistance of the samples against F-T cycles and sulfate solutions increased. With the increasing RCA ratio in the samples, there were increases in strength losses, but these losses were low and indicated that RCA was suitable for use in geopolymer concrete production.

Physicochemical, Mineralogical, and Mechanical Properties of Calcium Aluminate Cement Concrete Exposed to Elevated Temperatures

One commonly used cement type for thermal applications is CAC containing 38–40% alumina, although the postheated behavior of this cement subjected to elevated temperature has not been studied yet. Here, through extensive experimentation, the postheated mineralogical and physicochemical features of calcium aluminate cement concrete (CACC) were examined via DTA/TGA, X-ray diffraction (XRD), and scanning electron microscopy (SEM) imaging and the variation in the concrete physical features and the compressive strength deterioration with temperature rise were examined through ultrasonic pulse velocity (UPV) values. In addition, other mechanical features that were addressed were the residual tensile strength and elastic modulus. According to the XRD test results, with the temperature rise, the dehydration of the structure occurred, which, in turn, led to the crystallization of the monocalcium dialuminate () and alumina () structures. The SEM images indicated specific variations in morphology that corresponded to concrete deterioration due to heat.

Strength assessment of steel fibre reinforced recycled aggregate concrete by means of correlation between ultrasonic and point load tests

This paper aimed at assessing the in-situ strength of steel fibre reinforced concrete containing recycled coarse aggregate (RCA) using the correlation between ultrasonic and point load tests. The mechanical properties of recycled aggregate concrete can be improved by adding fibres in concrete mixes. On the other hand, the importance of strength estimation of existing concrete at the building site has led to use non-destructive and partially testing methods. So, in this research, the compressive strength of wet and dry cured mixes made with RCA and steel fibre (SF) at 1.5% by volume was evaluated by mean of point load test (PLT) and ultrasonic method. As per the experimental outputs, the standard deviation (SD) values increased up to 20% by increasing the substitution amount of natural aggregate with RCA from 50% to 100%. In addition, the point load index (PLI) of wet cured concrete mixes was obtained averagely about 14.3% more than that of dry cured concrete mixes. Furthermore, the strength estimation of conventional concrete or fibre reinforced recycled aggregate concrete at different ages was carried out using a two-variable equation between ultrasonic pulse velocity (UPV) and PLI values.

Stress-Strain Behaviour and Mechanical Strengths of Concrete Incorporating Mixed Recycled Plastics

Different types of recycled plastic have been used in concrete and most studies have focused on the behaviour of a single type of plastic. However, separating plastic wastes increases the cost and time of processing. To tackle this problem, this research presents an experimental investigation to determine the effect of incorporating different combinations of three types of recycled plastic waste aggregates—Polyethylene terephthalate (PET), High Density Polyethylene (HDPE) and Polypropylene (PP)—at different replacement ratios of coarse aggregate on physical and mechanical properties of concrete. The combinations include two plastic types at 10% and 20% replacement ratios and three plastic types at 15% and 30% replacement ratios. The performance of the plastic concrete was assessed based on various physical and mechanical properties including workability, fresh and dry densities, air content, compressive, indirect tensile and flexural strengths, modulus of elasticity, stress-strain behaviour and ultrasonic pulse velocity. It is found that the workability of Mixed Recycled Plastic Concrete (MRPC) at a low replacement rate is independent of the type of plastic. The minimum reduction in the compressive strength, indirect tensile and modulus of elasticity were achieved by R3 (PET + PP) at 10% replacement, while R5 (HDPE + PP) at 10% replacement achieved the highest flexural strength and ultrasonic pulse velocity values. The findings suggest that the mixed recycled plastics have a good possibility to partially replace coarse aggregates in concrete which will benefit the plastics recycling community and environment. Furthermore, the study will provide guidance to the concrete industry concerning the effect of the implementation of unsorted mixed types of plastic as coarse aggregates in the production of concrete.

Comprehensive microbiological studies on screening bacteria for self-healing concrete

The present study majorly focused on the selection of suitable bacteria through microbiological studies for concrete crack healing. However, Bacillus species of non-pathogenic type bacteria's Viz., Bacillus subtilis, Bacillus cereus, Bacillus licheniformis, and Bacillus halodurans were used as self-healing agents. Also conducted various microbiological studies such as gram staining process, biofilm, Exopolysaccharide, Endospores, Urease Enzyme, and Calcium Carbonate formations. Similarly, the growth pattern of bacteria was measured in different temperatures (25 °C, 30 °C, 35 °C, 37 °C, and 60 °C), environments (such as pH of 3,7,8,9,10,11,12,13, and 14), and concrete composition medium. The gram staining process has identified that the above four bacteria have gram-positive strains and a rod-like shape. The B.halodurans and B.licheniformis have shown more spore formation, urease enzyme production, Exopolysaccharide production, biofilm formation, and calcium carbonate formation than other cultures. The B.licheniformis has shown the highest growth rate at various temperatures and environmental conditions. However, in the case of concrete composition medium B.halodurans has shown the highest growth rate. To determine the above four bacteria's crack healing ability, 40 MPa strengthened concrete samples are prepared and, then 65% and 75% of stress level concentration were applied to form cracks. However, Ultra-sonic pulse velocity values and water absorption values are taken for the concrete specimens to assess the healing capability. From the obtained results, B.halodurans has shown an ultrasonic pulse velocity value of 4.6 km/s and with 1.71% of water absorption, which is optimum among other bacterial cultures. The present study strongly recommends using B.halodurans as self-healing agents in concrete repair works.

Development of a model to estimate concrete compressive strength using ultrasonic testing based on previous models

Ultrasonic pulse velocity test is one of the most important non-destructive tests for exploring the essential properties of concrete such as compressive strength. Many previous researchers have examined relationship between ultrasonic pulse velocity and the compressive strength of concrete, developing equations to link these factors; however, comparing the calculated compressive strengths created by applying different equations to the same ultrasonic pulse velocity value, the results are rarely even close. This research aimed to develop new model based on seven such previous equations using a statistical program (Minitab) to calculate the compressive strength of concrete more accurately. The compressive strength thus obtained was equal or very close to the average results obtained from all seven equations, and the results were verified against a dataset of 100 results from ultrasonic pulse velocity test for multi-story concrete building. The obtained results were also compared with the average results from the seven equations used within the experimental program. The comparisons confirmed that, the new model can be used as an alternative approach to calculating compressive strength instead of using all seven equations.