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Purpose: Occasionally, cement concrete is used in the machine tool industry to reduce costs and improve the dynamic behavior of the machine. Due to a lack of information on the material behavior of cement concrete under dynamic loads with high frequencies, a test bench has been developed based on the principle of resonance at WZL. This paper presents the further development of the test bench to improve the testing and the evaluation of the results. Furthermore, the execution of dynamic tests with alternating loads in a high-frequency range of specimens of ultra-high-performance concrete (UHPC) is described. The aim of the described tests is to investigate the influence of frequency range and the autoclaving post treatment on the limiting load of UHPC specimens. Methods: To be able to react in situ to a change in the natural frequency of the system and thus to ensure a consistent level of dynamic loading, a control and regulation method was developed and implemented into the test bench. Additionally, dynamic tests of UHPC specimens with different load levels and frequency ranges are executed on the test bench also using the automatic test regulation. The UHPC specimens were autoclaved after production to achieve high material properties and to anticipate shrinkage deformation. The amplitudes of load applied to the specimens were determined as function of the previously determined static tensile strength. The amplitudes of load tested were set between 37 and 50% of the static centric tensile strength. The frequencies tested were at about 326 Hz respectively 475 Hz and therefore lie in a high-frequency range. Results: First tests with the new developed automatic test regulation show, that a consistent level of dynamic load can be achieved. The dynamic long-term tests of autoclaved UHPC specimens with different load levels and frequency ranges show, that the limiting load for alternating forces on UHPC in a high-frequency range lies in the area of 40% of the static centric tensile strength. These results confirm the conclusions of other researchers for the lower-frequency ranges and expand the conclusions to the examined frequency ranges. With the test set-up and the automatic test regulation, fatigue tests can be performed 40 to 50 times faster than with conventional test set-ups (with frequencies at about 10 Hz as a reference). Conclusion: By implementing an automatic adaption of the actual resonance frequency of the system, a consistent level of dynamic load on the specimens could be achieved. Furthermore, it can be stated, that the limiting load for alternating forces on UHPC at high frequencies is mostly unaffected by the actual range of high frequencies or the follow-up treatment of the specimens. Future research should issue a more detailed localization of the limiting force as well as other post-treatments and a transfer to the application of UHPC in real parts of machine tools. [ABSTRACT FROM AUTHOR]

In order to improve the mechanical properties of concrete, the active admixture silica fume was first selected and mixed into the cement by the internal admixture method, and then macro-mechanical tests were carried out on the pure slurry and concrete with different silica fume content, the silica fume was compared respectively. The improvement results of ash on the mechanical properties of pure slurry and concrete were compared, and the reasons for the difference in the modification results were analyzed. Finally, the modification mechanism was explored by combining scanning electron microscope(SEM) and X-ray diffraction(XRD) microscopic test techniques. The results show that the addition of silica fume does not significantly improve the mechanical properties of the cement paste. The 28 d compressive strength of cement concrete based on interface modification is greatly improved. When the silica fume content is 10%, it is relatively unchanged. The compressive strength of concrete has increased by 26. 4% . It can be inferred that silica fume improves the concrete interface and thus improves the overall mechanical properties of the concrete. Comparing the scanning electron microscope images of the concrete before and after the interface modification, silica fume not only improves the compactness of the cement matrix, but also improves the structure and density of the concrete interface, as well as the arrangement of the hydration product calcium hydroxide (CH) at the interface. Silica fume has the filling effect, promotes the secondary hydration reaction and the pozzolanic reaction with CH, etc. As the content of silica fume increases, its CH content decreases, C3 S and SiO2 increase, and the physical and chemical effects between silica fume and hydration products are used to improve the overall performance of the modified concrete. [ABSTRACT FROM AUTHOR]

The effect of partial replacement of coarse aggregate by plastic waste on the performance of concrete under impact three-point bending loading was investigated experimentally and numerically. Specimens were prepared for 5%, 10% and 20 % replacements by volume of coarse aggregate. For each case, three beams of 100 mm wide, 50 mm deep and 400 mm long were loaded to failure in a drop-weight impact machine by subjecting it to 30 N weight from 400 mm height, while another three beams of the same size were tested under static load. The load-displacement of beams of concrete with plastic waste subjected to static and impact loads were studied. The dynamic beam behaviour was also analysed numerically using the finite-element method (FEM) based LUSAS software. In general, the experimental results reveal that the impact tup, inertial load and bending load increase with the increase in the percentage of coarse aggregate replacement by plastic waste, while the static peak bending load always decreases. The concrete with plastic waste is stronger and more energy-absorbing under impact loading, than under static loading. The predicted load against displacement behaviours of both ordinary concrete and concrete with plastic waste, are well matched with the experimental results.

The bending and pulling fatigue test is critical for inspecting cement concrete. The existing fatigue test equipment is expensive and non-conducive for the grassroots sector of construction units. The purpose of this study is to explore a scheme to modify an asphalt mixture rutting test machine to perform bending and pulling fatigue tests on cement concrete specimens. The test results show that (1) the fatigue life obtained from the fatigue test equipment for cement wheel load under the same stress level has a large dispersion, but the fatigue equation for the same group of specimens under different stress levels is fitted and found to be above 0.9; (2) the fatigue life of cement concrete obtained by cyclic loading using semi-positive sagittal loading waveform is shown by the Weibull data distribution model, and the fit is above 0.99; and (3) in a comparative study of the fatigue obtained from fatigue tests performed on other fatigue test equipment, the percentage of the absolute value of the average difference of the equation’s correlation coefficient is between 0.01% and 10.12%. In summary, the cement wheel load fatigue test equipment data is reliable, and the test scheme is reasonable. Thus, it can be used as a test scheme to examine the bending and tensile fatigue tests of cement concrete.

This investigation delineates the enhancement of fly ash (FA) properties through mechanical treatments for sustainable construction applications and reducing carbon dioxide (CO 2) emissions. FA, a byproduct of coal combustion in power generation, inherently exhibits limited pozzolanic activity. This research evaluates the impact of particle size reduction via dry and wet milling treatments on FA's pozzolanic behavior. The study's comparative analysis involves three FA variants: untreated raw material, dry-milled, and wet-milled FA. Extensive characterization encompassed chemical composition, physical properties, and microstructural features. Results demonstrate a marked improvement in pozzolanic activity in milled FAs, with wet milling yielding superior outcomes in particle size reduction (98% diminution compared to raw FA) and pozzolanic reactivity. The comparative assessment underscores wet milling's efficacy over dry milling and untreated FA in enhancing FA's performance as a sustainable construction material. In light of these findings, the study advocates for continued exploration of FA treatments, aiming to optimize their utility in eco-friendly construction practices. • Chemical, physical, and microstructure properties of fly ash (FA) were investigated. • A significant improvement in pozzolanic activity of fly ash was observed due to wet milling. • Mechanical treatment of FA contributes to lower CO 2 emissions, supporting eco-friendly construction practices. • FTIR analysis shows that finer FA particles exhibit improved crystallographic ordering within silicate minerals, potentially improving their pozzolanic properties. [ABSTRACT FROM AUTHOR]

Thermal conductivity is a fundamental material parameter involved in various infrastructure design guides around the world. This paper developed an innovative neural network (NN) aided homogenization approach for predicting the effective thermal conductivity of various composite construction materials. The 2-D meso-structures of dense graded asphalt mixture, porous asphalt mixture, and cement concrete were generated and divided into 2n × 2n square elements with specific thermal conductivity values. A two-layer feed-forward neural network with sigmoid hidden neurons and linear output neurons was built to predict the effective thermal conductivity of the 2 × 2 block. The Levenberg-Marquardt backpropagation algorithm was used to train the network. By repeatedly using the neural network, the effective thermal conductivities of 2-D meso-structures were calculated. The accuracy of the above NN aided homogenization approach was validated with experiment, and various factors affecting the effective thermal conductivity were analyzed. The analysis results show that the accuracy of the NN aided approach is acceptable with relative errors of 1.92~4.34% for the dense graded asphalt mixture, 1.10~6.85% for the porous asphalt mixture, and 1.13~3.14% for the cement concrete. The relative errors for all the materials are lower than 5% when the heterogeneous structures are divided into 512 × 512 elements. Ignoring the actual material meso-structures may lead to significant errors (134.01%) in predicting the effective thermal conductivity of materials with high heterogeneity such as porous asphalt mixture. While proper simplification is acceptable for dense construction composite materials. The effective thermal conductivity of composite cement-asphalt mixtures increases with higher saturation of grouted material. However, the improvement effect of the high-conductive cement paste on the composite cement-asphalt mixtures could be significantly reduced when the cement paste concentrates at the bottom of the mixture. Cracked aggregates and segregation of material components tend to decrease the effective thermal conductivity of construction materials. The NN aided homogenization approach presented in this paper is useful for selecting the effective thermal conductivity of construction materials.

Motivated by the multiple benefits of recycling plastic ingredients in cementitious materials, the present study focuses on the design of sustainable cement concrete incorporating recycled mixed plastic fine aggregate (MPFA) as a partial replacement of natural sand (NS). The MPFA produced in this work is composed of a combination of polymer types with similar concoctions to those observed in the postconsumer waste streams. This study approach is vastly different from past reported studies on the use of sorted, highly purified single-type recycled plastic aggregate in cement concrete. A multi-criteria decision-making technique, Best-Worst Method (BWM), was integrated with the Taguchi method to maximize the quality of MPFA concrete based on the Fuller–Thompson theory. More specifically, an L9 (34) Taguchi orthogonal array with four three-level design factors was adopted to optimize the fresh, durability, and mechanical properties of MPFA concrete. The results showed that MPFA concrete produced with 400 kg/m3 cement content, 0.43 water/cement ratio, 0.43 fine aggregate/total aggregate ratio, and 10 vol% MPFA content exhibited the highest quality. Findings from the present work also revealed that MPFA concrete produced with tailored particle size distribution of MPFA NS fine aggregate system achieved superior, if not comparable, qualities to those of conventional concrete.

Automotive paint sludge (PS) is the waste product generated in the painting process of vehicle bodies. Although automotive spray painting is an automated operation, its efficiency is still quite low, since approximately 40–50% of the employed paint does not reach the target and, after being mixed with the collecting water, becomes PS. PS is a very complex material that contains several organic and inorganic components, in addition to 90% water immediately after production. Italian automotive factories produce from 2.5 to 5.0 kg of PS per painted car. If that figure is related to the number of vehicles produced worldwide every year, in the order of 100 million, it determines an annual PS amount in the order of 200,000–500,000 t. Consequently, a proper final destination for PS must be found. The waste management hierarchy and the principles of the circular economy require that we privilege solutions that foresee the recovery of valuable products or energy. This paper first reviews the processes and the machines that have been recently developed to obtain an enhanced mechanical dewatering of PS. The pretreatment of PS dewatering is often crucial in order to obtain high efficiency in the subsequent recovery process. Afterwards, the paper presents and discusses the recovery options that have been proposed and tested, at different scales, by several authors in the last thirty years. The processes for PS management can be grouped as follows: (i) direct employment of physically/chemically treated PS in the production of primers and sealants; (ii) utilization of PS for the production of building materials, as supplementary components of cement concrete, mortar, or bituminous mixtures; (iii) extraction of valuable organic and inorganic products by using thermal processes (pyrolysis, gasification); (iv) biological processes for PS detoxification, metal recovery, and stabilization before landfilling.

Cracks and cavities belong to two basic forms of damage to the concrete structure, which may reduce the load-bearing capacity and tightness of the structure and lead to failures and catastrophes in construction structures. Excessive and uncontrolled cracking of the structural element may cause both corrosion and weakening of the adhesion of the reinforcement present in it. Moreover, cracking in the structure negatively affects its aesthetics and in extreme cases may cause discomfort to people staying in such a building. Therefore, the following article provides an in-depth review of issues related to the formation and development of damage and cracking in the structure of concrete composites. It focuses on the causes of crack initiation and characterizes their basic types. An overview of the most commonly used methods for detecting and analyzing the shape of microcracks and diagnosing the trajectory of their propagation is also presented. The types of cracks occurring in concrete composites can be divided according to eight specific criteria. In reinforced concrete elements, macrocracks depend on the type of prevailing loads, whereas microcracks are correlated with their specific case. The analyses conducted show that microcracks are usually rectilinear in shape in tensioned elements; in shear elements there are wing microcracks with straight wings; and torsional stresses cause changes in wing microcrack morphology in that the tips of the wings are twisted. It should be noted that the subject matter of microcracks and cracks in concrete and structures made of this material is important in many respects as it concerns, in a holistic approach, the durability of buildings, the safety of people staying in the buildings, and costs related to possible repairs to damaged structural elements. Therefore, this problem should be further investigated in the field of evaluation of the cracking and fracture processes, both in concrete composites and reinforced concrete structures.

The thermal properties of pavement layers made of concrete with varying bulk densities are a particularly interesting topic in the context of development road technologies. If a hybrid layer system is used as a starting point, with thin asphalt layers (from 1 cm to 4 cm) laid on top of a foam concrete layer, thermal properties begin to play a crucial role. The main research problem was to create a test method enabling the assessment of the influence of solar heating on the thermal parameters of the building material, especially cement concrete. For this reason, this paper is concerned specifically with the assessment of a new methodology for testing and calculating the value of the thermal diffusivity coefficient of samples made of concrete varying bulk densities. In this case, using the proprietary concept the authors built a solar simulator using a multi-source lighting system. The analysis of the results of laboratory tests and numerical analyses allowed the authors to observe that there is a strong correlation between the bulk density of samples heated and the thermal diffusivity parameter, which appears in the unidirectional heat transfer equation. The strength of this relationship has been expressed with the coefficient of determination and amounts to 99%. The calculated values of the coefficient of thermal diffusivity for samples made of foam concrete range from 0.16×10−6m2s to 0.52×10−6m2s and are lower (from 2.5 to 8 times) than the value determined for samples made of typical cement concrete.

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The performance of waterproof bonding layer systems significantly affects the service life of concrete bridge deck pavement. This article aims to compare the bonding properties and composite structure mechanical properties of different waterproof bonding layer systems in bridge deck pavement to recommend appropriate structures based on service conditions. To fulfill this objective, four kinds of waterproof bonding material composite systems were designed, and test samples were fabricated. Then, the waterproof bonding layer properties were studied by penetration resistance tests, scalding resistance tests, and corrosion resistance tests. Pull-off tests were conducted to compare the bonding properties. Then, dynamic modulus tests, Hamburg wheel tracking tests, and static load creep tests of composite structure specimens were implemented to evaluate the dynamic and static mechanical performances and water-temperature stability. The findings showed that the four schemes had good impermeability. The pull-off strengths of scheme III at 25 °C were about 2.5-, 2.5-, and 4-times those of schemes I, II, and IV, respectively, and the pull-off strengths at 50 °C were about 1.6-, 2-, and 1.6-times those of schemes I, II, and IV, respectively, and the bonding performances and dynamic modulus of different schemes were ranked as follows: III > I > II > IV. The results of the Hamburg wheel tracking test were consistent with the static load creep test. The high-temperature stability of scheme IV was the best, while the stabilities of scheme III and I were better than that of scheme II. In conclusion, the scheme of concrete bridge deck pavement can be selected based on the environmental conditions and traffic load, and schemes III and I should be considered first. The findings of this research could provide technical support for the future design of bridge deck waterproof bonding systems. [ABSTRACT FROM AUTHOR]

Cement concrete has always played an essential role in the general development of the construction industry. Many studies improve the properties and durability of cement concrete by adding chemical additives and mineral additives. One of them, fly ash, is one of the most preferred applied mineral additives. Currently, the demand for fly ash is becoming an urgent problem, as it is also can reduce environmental pollution from by-products of thermal power plants not only in Vietnam but also all around the world. To evaluate the factors affecting compressive strength of concrete, such as fly ash, type of cement used, date and designed concrete grade, we based our study on the design of experiment (DOE). The influencing variables have different levels of investigation, which are based on previous studies. With the useful statistical analysis tools, the number of experiments, and the results of the experimental analysis, we can see the influence of each element and their interaction on the compressive strength of the concrete. On that basis, it is possible to choose the option with reasonably selected ingredients to achieve the expected optimal compressive strength.

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The paper presents a fragment of on-going investigations directed on creation of optimal information environment that ensures an access to the R&D publications from the known scientific journals and other scientific serials which are necessary for qualitative execution of scientific and technological activities on priority areas in highway engineering. A citation analysis has been applied while using data of Journal Citation Reports for selection of world scientific publications which are necessary for execution of investigations on heat and mass transfer in road dressings. Their deformations occur under various climatic conditions due to heat and mass transfer processes, interaction of transport flows and road surface that leads to crack formation in depth and on the surface of road dressings. Structure of constructive layers especially which are created with the help of technogenic wastes (asphalt-, reinforced concrete, concrete, brick scrap and products of their recycling, various wastes of production etc.) exerts an influence on heat and mass transfer. The paper presents results of investigations on heat flows, boundary layers according to viscosity, air velocity, geometric characteristics, permeability, capillary pressures in materials. It has been shown that calculations based on principles of complex number usage have specific features in engineering practice: it is required to observe their accuracy in approaches, calculation reduction due to some accuracy degradation as a consequence of transition from complex numbers to their modules with exclusion of phase shift account and related with propagation of thermal waves. In this respect calculations of heat resistance without phase shifts are considered as rather important if they are in agreement with principles based on the fact that a complexity is characterized by thermal absorptivity of the material in a great number of calculations. The investigations have been supported by Henan Center for Outstanding Overseas Scientists, Grant Number GZS 2018006 (People’s Republic of China, Henan Province).

Microwave deicing technology, as a new environmentally friendly deicing technology, can effectively solve the problem of the frequent icing of road surfaces in the winter, which affects the safety of traffic. To improve the efficiency of microwave deicing on cement concrete pavement, this study proposed the use of magnetite, iron sulfide slag, steel slag, lead–zinc slag, and graphite as microwave-absorbing materials, and conducted microwave deicing tests under the influence of five factors, namely the form of the pavement surface structure, the content of the microwave-absorbing material, microwave power, the shielding state, and dry and wet conditions. Layer by layer, we selected the combination of pavement surface structure, microwave-absorbing material content, microwave power, shielding state, and dry and wet conditions on the bottom surface of the concrete slab with the optimal deicing effect. The results showed that the 2 cm scattered microwave-absorbing surface concrete structure has the fastest heating rate; the higher the magnetite content and microwave power, the higher the deicing efficiency; the maximum heating rate can be increased by 17.6% when the shielding layer is set at the bottom of the cement concrete slab; and the heating rate of the microwave-absorbing concrete slab in the wet state is increased by 20.8% relative to the dry state. In summary, 7000 W of power, a magnetite content of 60 vol % in the scattered microwave-absorbing surface, a shielding layer set at the bottom surface, and wet conditions can greatly improve the efficiency of microwave deicing compared with the microwave ice melting effects of plain cement concrete and other microwave-absorbing materials mixed into the concrete. In addition, the temperature uniformity of the microwave-absorbing materials is essential to improve the deicing efficiency of microwave-absorbing concrete, so it is essential to explore it further.

With the development of the technical trend, concrete using waste alternate material instead of sand material found economic potential for good structural behaviour. Besides, the susceptible crack, low strength-to-weight ratio, and low compressive strength are the reasons for shrinkage. Due to this reason, the investigation aims to limit the shrinkage under live load and increase the compression and flexural strength by the introduction of coconut waste chopped fiber (wCF), waste fly ash (wFA), and carbon nanotube powder (CNT) blended with conventional Portland paste. The developed concrete consists of 5 wt% wCF, 10 wt% wFA, and 0, 5, 10, and 15 wt% of CNT and is subjected to X-ray diffraction analysis, bulk density, compression and flexural strength, and water absorption studies. The X-ray diffraction pattern revealed the wCF, wFA, CNT, and matrix compositions. The concrete developed with 5 wt% wCF, 10 wt% wFA, and 15 wt% CNT cured within 28 days recorded maximum behaviour of compression strength (47 ± 1.8 MPa), flexural strength (4.9 ± 0.19 MPa), and water absorption of (2.8 ± 0.05 %)., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 Published by Elsevier Ltd.)

The mixing water used for cement concrete has a significant effect on the physical properties of the material after hardening; however, other than the upper limit for the mixed impurities, not enough consideration has been given to the functions and characteristics of water at the molecular level. In this study, we investigated the effect of four different types of water (two spring-, mineral waters, tap water and distilled water) on the drying shrinkage of the hardened cement by comparing the material properties of the concrete specimens and analyzing the molecular structure of the water and cement mortar using aquaphotomics. The near infrared (NIR) spectra of waters used for mixing were acquired in the transmittance mode using a high-precision, high-accuracy benchtop spectrometer in the range of 400–2500 nm, with the 0.5 nm step. The NIR spectra of cement paste and mortar were measured in 6.2 nm increments in the wavelength range of 950 nm to 1650 nm using a portable spectrometer. The measurements of cement paste and mortar were performed on Day 0 (immediately after mixing, cement paste), 1 day, 3 days, 7 days, and 28 days after mixing (cement mortar). The spectral data were analyzed according to the aquaphotomics’ multivariate analysis protocol, which involved exploration of raw and preprocessed spectra, exploratory analysis, discriminating analysis and aquagrams. The results of the aquaphotomics’ analysis were interpreted together with the results of thermal and drying shrinkage measurements. Together, the findings clearly demonstrated that the thermal and drying shrinkage properties of the hardened cement material differed depending on the water used. Better mechanical properties were found to be a result of using mineral waters for cement mixing despite minute differences in the chemical content. In addition, the aquaphotomic characterization of the molecular structure of waters and cement mortar during the initial hydration reaction demonstrated the possibility to predict the characteristics of hardened cement at a very early stage. This provided the rationale to propose a novel evaluation method based on aquaphotomics for non-invasive evaluation and monitoring of cement mortar.

Moisture content has implications on the durability and service life of a concrete structure. Measurement of the moisture content is usually performed via non-invasive electrical techniques. In this paper, the electrical response of hardened concrete is acquired and correlated to the Degree of Saturation (DoS) of the material. The pulsed electrical excitation is imposed on the sample and the output is recorded at various electrode locations along the sample length. Using a one dimensional circuit model and a Gaussian and Inverse Multiquadric Radial Basis Function (RBF) based inversion scheme, the cumulative and spatial distribution of the real and imaginary parts of the impedance are re-constructed along the length of the sample. An excellent fit with the experimental data is observed and an empirical relationship is proposed between the DoS and the absolute impedance, which would facilitate the estimation of the DoS profile in samples with homogeneous and non-homogeneous moisture distribution. [ABSTRACT FROM AUTHOR]

The effect of partial replacement of coarse aggregate by plastic waste on the performance of concrete under impact three-point bending loading was investigated experimentally and numerically. Specimens were prepared for 5%, 10% and 20 % replacements by volume of coarse aggregate. For each case, three beams of 100 mm wide, 50 mm deep and 400 mm long were loaded to failure in a drop-weight impact machine by subjecting it to 30 N weight from 400 mm height, while another three beams of the same size were tested under static load. The load-displacement of beams of concrete with plastic waste subjected to static and impact loads were studied. The dynamic beam behaviour was also analysed numerically using the finite-element method (FEM) based LUSAS software. In general, the experimental results reveal that the impact tup, inertial load and bending load increase with the increase in the percentage of coarse aggregate replacement by plastic waste, while the static peak bending load always decreases. The concrete with plastic waste is stronger and more energy-absorbing under impact loading, than under static loading. The predicted load against displacement behaviours of both ordinary concrete and concrete with plastic waste, are well matched with the experimental results. [ABSTRACT FROM AUTHOR]

This paper focuses on the investigation of the material properties of FC500 foam concrete. Innovation is very important for the solution of cast-in-place concrete forms in practice today. Part of its innovative construction application is the possibility of using foam concrete in a composite structure and the use of its mechanical properties in the load-bearing parts of civil engineering structures. The method of detecting the mechanical properties of foam concrete by using non-standard cantilever test is also innovative. Here, an advanced approach of modelling specimens using powerful computational systems based on the finite element method is used. This modern material is researched especially for its use in transportation structures. For its application, it is necessary to define its resistance to mechanical loads. The main content of the research consists of correlations between experimental measurements and analytical and numerical results. This is the principle of quasi-linear identification of the non-linear behavior of polymeric cementitious porous material during tests on specimens. The focus of the research is an extensive experiment: measurements of the deformation of the specimens until failure. The following methods were chosen to investigate the material properties: small cantilever test, standard tensile test and compression test. The cantilever test was performed for the individual components of the FC500 composite and cement concrete, but also as a compact composite. Numerical simulation models were developed to correlate the individual results in order to validate the uniaxial test results. The conclusions of the research led to the definition of standardized stress–strain diagrams of the FC500 material for compression and especially tension. This is a definition of the behavior of this polymer composite, usable for the development of numerical models of full-scale structures. The results of the research will be applied in the development of national standards for the use of advanced materials in transportation structures (cycle paths, parking lots, traffic playgrounds, lightly trafficked forest roads and trails, etc.).

Accelerator/retarder admixtures are often added into concrete to improve its early-age strength, which needs to be effectively monitored during its hardening process. The electromechanical impedance (EMI) technique has validated its effectiveness for concrete hydration monitoring, this study attempted to extend the EMI technique to monitor 28-day age of strength gain in concrete that added with accelerator/retarder admixtures. Two types of new piezoelectric (PZT) transducers namely cement/aluminum embedded PZT (CEP/AEP) were proposed for EMI monitoring. The feasibility of the CEP and AEP was first verified via finite element analysis, where hydration heat effect on the two types of transducers was comparatively evaluated by numerical modeling. In the experiment, CEP/AEP transducers were applied to monitor the strength gain in concrete cubes, where characteristics of EMI signature and its statistical indices including root mean square deviation (RMSD) and mean absolute percentage deviation (MAPD) were analyzed and correlated to strength development in concrete. Monitoring results demonstrated that concrete hydration triggered by retarder/accelerator were successfully captured by EMI signature. RMSD and MAPD indices further indicated that AEP had preferable performance than CEP transducer for monitoring early-age strength gain of concrete, as it could immune from hydration heat effect. [ABSTRACT FROM AUTHOR]

Cement concrete plays a crucial role in modern construction, but its production process results in significant CO 2 emissions, posing a substantial threat to the environment. To achieve green production, the use of industrial waste slag as a raw material for concrete has been widely accepted. This study focuses on the potential utilization of Bayer Process Red Mud (RM), a by-product of the alumina refining process, characterized by high alkalinity and low pozzolanic activity, limiting its application in cement concrete. The reactive activity of RM after calcination treatment was investigated to overcome this challenge and enhance the reactivity of RM. Fourier Transform Infrared Spectroscopy (FTIR) was employed to determine the degree of polymerization of RM at different calcination temperatures, and thus evaluate its pozzolanic activity. Integrating physical tests, chemical experiments, and microscopic analysis, this study thoroughly analyzes the relationships between different evaluation methods and finds a negative correlation between the degree of polymerization and the pozzolanic activity index, boasting a correlation coefficient of 0.904. The results indicate that RM exhibits the highest pozzolanic activity at a calcination temperature of 700 °C. Therefore, this method has been proven effective and can serve as a quick and convenient means of evaluating the pozzolanic activity of RM. The findings of this study are expected to promote the green development of the cement industry, better utilize waste slag resources, reduce CO 2 emissions, and enhance the performance of building materials. • Activity of red mud was analyzed from chemical, physical, and microstructural testing. • Polymerization degree was introduced for rapid pozzolanic activity assessment. • The degree of polymerization of RM was characterized through FTIR analysis. • A strong correlation between polymerization degree and strength activity index was found. [ABSTRACT FROM AUTHOR]

The development of road network infrastructure is an important component of the economic development of the European Union. Updating of the road network contributes to the integration of the economies of countries into a coherent whole. The road network provides the free movement of citizens, the movement of goods and the effective implementation of various services. The increase in the length of the road network leads to an increase in the financial and material costs necessary to ensure its maintenance and repair. One of the ways to reduce costs is by strengthening the physic-mechanical and operational characteristics of the pavement due to the widespread use of cement concrete. The quality of the pavement of cement concrete depends largely on the rational selection of its composition. This allows a significant increase in the durability of road pavement. The purpose of the research was: the development of recommendations for the rational selection of the composition of the road pavement material of cement concrete, aimed at upgrading longevity, and taking into account its frost resistance grade. According to the goal, the following tasks were developed: the analyses of the climatic zones in which the road network of the European Union is located; the development of a research plan, a selection of the response function and influence factors; the study of physico-mechanical and operational characteristics of the researched material of road pavement; on the basis of the obtained data, the calculation of the complex of experimental-statistical models, which describe the physico-mechanical and operational characteristics of the road pavement material; on the basis of experimental statistical models, a method was proposed for selecting the rational compositions of the cement concrete pavement road material depending on the conditions of its application. The results presented in the article can be used in engineering and scientific practice for the selection of road pavement from cement concrete for highways.

The aim of this study is to investigate the effect of municipal solid waste incineration bottom ash from a cogeneration plant on the physical and mechanical properties and durability of cement concrete. Part of the cement in concrete mixtures tested was replaced with 0%, 3%, 6%, 9%, and 12% by weight of municipal solid waste incineration bottom ash. Concrete modified with 6% of bottom ash had a higher density (2323 kg/m3), compressive strength at 28 days (36.1 MPa), ultrasonic pulse velocity (3980 m/s), and lower water absorption rate (3.93%). The tests revealed that frost resistance, determined in all-sided testing directions, of concrete modified with 6%, 9%, and 12% of bottom ash added by weight of cement corresponds to strength grade F100. Such concrete can be used in construction works.

Alkali-activated binders are currently a widely-researched material. Thanks to the use of secondary raw materials such as slag from metallurgical production and ash from combustion, it appears to be a more promising and more environmentally friendly material than conventional cement concrete. Considerable attention is paid to the bonding phase itself, but only a few works deal with the binder-aggregate interaction. With cement concrete, much more attention is paid to this issue. This paper deals with the possibility of observation using electron microscopy and the information that can be obtained by this method. The problems of sample preparation and difficulties in the course of our own observation are observed.

The study analyses the different kinds of sealing materials that wrapped coffins, examples of which were excavated from several Chinese tombs. The mineral compositions, microstructure and properties of these materials were assessed by means of scanning electron microscopy with energy‐dispersive spectroscopy (SEM‐EDS), differential scanning calorimetry with glass transition (DSC‐TG), X‐ray powder diffraction (XRD), as well as mechanical and weather resistance tests. The results showed that the historical cement concrete had best overall performance due to its compact structure. This concrete contains more calcium and aluminium, and most likely belongs to old artificial white Portland cement. The properties and structures of lime mortar were related to the content of lime and the kinds of organic additives. Although the ancient people perhaps had found these rules, subject to social productivity, the optimum lime mortars were not widely used. As a natural sealing material, green paste mud had been used in this field for a long time. It consisted of microcrystalline muscovite, feldspar and quartz. Its strength, sealing and water resistance were better than ordinary soil, but the stability was general. Thus, it was gradually replaced by hybrid artificial materials. [ABSTRACT FROM AUTHOR]

The aim of this research was to find the best alternative for river sand in concrete. In both geopolymer concrete (GPC) and cement concrete (CC), the fine aggregates are replaced with various sustainable mineral ashes, and mechanical and durability tests are conducted. Specimens for tests were made of M40 grade GPC and CC, with five different soil types as river sand substitute. The materials chosen to replace the river sand are manufactured sand (M-sand), sea sand, copper slag, quarry dust, and limestone sand as 25%, 50%, 75%, and 100%, respectively by weight. GPF50 and CC50 were kept as control mixes for GPC and CC, respectively. The test results of respective concretes are compared with the control mix results. From compressive strength results, M-sand as a fine aggregate had an increase in strength in every replacement level of GPC and CC. Additionally, copper slag is identified with a significant strength reduction in GPC and CC after 25% replacement. Copper slag, quarry dust, and limestone sand in GPC and CC resulted in considerable loss of strength in all replacement levels except for 25% replacement. The cost of GPC and CC is mixed with the selected fine aggregate replacement materials which arrived. Durability and cost analyses are performed for the advisable mixes and control mixes to have a comparison. Durability tests, namely, water absorption and acid tests and water permeability and thermal tests are conducted and discussed. Durability results also indicate a positive signal to mixes with M-sand. The advisable replacement of river sand with each alternative is discussed.

To understand the enhancing effect and fiber-reinforced mechanism of composite fibers reinforced cement concrete, the influences of composite fibers on micro-cracks and the distribution of composite fibers were evaluated by optical electron micrometer (OEM) and scanning electron microscope (SEM). Three kinds of fiber, such as polyacrylonitrile-based carbon fiber, basalt fiber, and glass fiber, were used in the composite fibers reinforced cement concrete. The composite fibers could form a stable structure in concrete after the liquid-phase coupling treatment, gas-liquid double-effect treatment, and inert atmosphere drying. The mechanical properties of composite fibers reinforced concrete (CFRC) were studied by universal test machine (UTM). Moreover, the effect of composite fibers on concrete was analyzed based on the toughness index and residual strength index. The results demonstrated that the composite fibers could improve the mechanical properties of concrete, while the excessive amount of composite fibers had an adverse effect on the mechanical properties of concrete. The composite fibers could significantly improve the toughness index of CFRC, and the increment rate is more than 30%. The composite fibers could form a mesh structure, which could promote the stability of concrete and guarantee the excellent mechanical properties. [ABSTRACT FROM AUTHOR]

The article presents the influence of the suggested operating media on the modification of parameters of cement concrete intended for airfield pavements. Cement concrete contains cement CEM I 42,5, granite grit, fine washed aggregate, water and air entraining as well as plasticizing additive. Analyses included the assessment of changes in mechanical and physical parameters (weight absorbability and water capillary action) of hardened concrete. The observed changes were associated with the internal structure of concrete composite. Based on the obtained results, different influence of the applied operating media on mechanical parameters of hardened concrete was determined. [ABSTRACT FROM AUTHOR]

In this paper, the effects of water-cement ratio, air-entraining agent type, and air content on the pore characteristic parameters of hardened concrete were investigated through an extensive series of experimental studies. First of all, according to different water-cement ratios, air-entraining agent types, and air contents, the correlation between the concrete pore spacing factor and the frost resistance durability factor was revealed by using the automatic analysis and testing instrument for the pore system of hardened concrete. Then, the decision tree method was utilized to propose specific pore spacing factors for different concrete scenarios, including the non-air-entrained concrete, air-entrained concrete, concrete with unqualified frost resistance, and concrete with qualified frost resistance. In cases where the pore spacing factor measurement fell within an ambiguous range, the classification was further refined according to the water-cement ratio. On that basis, the comprehensive range of pore spacing factors for the concrete with a qualified frost resistance was determined. Finally, the post-evaluation method and standard procedure for assessing the frost resistance of concrete entities based on pore spacing factor and water-cement ratio were proposed to verify whether the frost resistance of concrete buildings meets the life expectancy requirements. This method facilitates the evaluation of the frost resistance quality of newly-built concrete projects, as well as the investigation and monitoring of frost resistance in existing structures during service. • The correlation between the pore spacing factor and the frost resistance durability was established. • The threshold value of the pore spacing factor was determined based on the decision tree method. • A post-evaluation method for frost resistance of hardened concrete was proposed. • The frost resistance quality evaluation system for in-service concrete entities was constructed. [ABSTRACT FROM AUTHOR]

While being operated auto-road pavements are subjected to intensive mechanical impacts, ultraviolet ray irradiation, freeze-thaw temperatures, freezing and thawing, drying and moistening. Due to these actions various types of pavement distresses appear on the road pavement. The most significant and dangerous type of distresses is micro-cracks on the road surface. One of the main reasons for their formation is an action of weather and climatic factors that initiate large changes in temperature of coating surface and occurrence of large temperature gradients in the upper layer. In this context while designing and operating auto-roads it is rather essential to investigate a stress state in road surface which is caused by temperature action. Purpose of the described investigations is to determine permissible temperature gradients for cement-concrete pavements that exclude formation of micro-cracks on their surface and thickness of damaged surface layer. Calculations of road pavement have been carried out at various laws for temperature distribution in its depth. A finite difference method realized in PARUS software has been used for studying a stress state of cement-concrete auto-roads. Regularities for distribution of stresses in cement-concrete pavement of auto-roads have been obtained at various surface temperatures. Permissible temperature gradients in the upper pavement layer have been determined and thickness of the layer where micro-cracks are formed has been assessed in the paper. Strength criterion based on the process of micro-crack formation and development in the concrete has been used for calculations. Risk of micro-crack formation on the auto-road pavement depends on material strength, conditions of plate fixing and temperature gradients.

The aim of the study was to study behavior of concrete containing marble mining waste under aggressive environment. Waste from marble mining and processing industries was used in concrete as coarse aggregate in combination with conventional coarse aggregate. The particle packing density approach was followed to design the concrete mix and 75% conventional coarse aggregate was replaced by aggregate obtained by crushing waste from marble mining waste. The water-cement ratio was fixed 0.45 for all the mixes. Properties of concrete under aggressive environment such as chloride ion penetration, resistance to sulphates were evaluated. The test results revealed that, resistance to chloride ion penetration and sulphate attack increased as compared to control concrete. Overall the results supported by microstructure analysis indicate that there is no significant adverse effect on the use of marble waste as a coarse aggregate on the durability properties of concrete. The results of fire study reveal that, concrete with marble waste performs better than control concrete up to a temperature of 800 ºC.

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• Heat-reflective and superhydrophobic cement concrete surface were prepared. • The surface has high infrared reflectance approaching that of the white TiO 2. • The superhydrophobic properties exhibit good stability to rain and UV exposure. • The superhydrophobic surface has good anti-ice rain properties under −12 °C. • The surface has great potential in the exterior of building walls or roofs. Antifouling, weatherable, and heat-reflective coatings have much value for solar sheltering of building in summer. In this work, a multifunctional cement mortar mixture was obtained by mixing "cool cold" black pigments with cement, sand, TiO 2 nanoparticles and water. After the mixture was mortared on a cement concrete slab, dried at room temperature and treated with fluorine silicon sol, a gray cement concrete layer was obtained. UV–visible-infrared spectrometer confirmed that the layer has obvious infrared-reflective property at 780–2500 nm. Under the radiation of a 275 W and 40 cm height infrared lamp, the surface temperature of the gray "cool cold" cement concrete is about 40 °C lower than that of the carbon black cement concrete, and is about 20 °C lower than that of the ordinary cement concrete, and is only about 1 °C higher than that of the white TiO 2 cement concrete. Moreover, all these cement concrete surfaces showed typical superhydrophobic (SH) property and the "cool cold" cement concrete surface further exhibited stable SH properties to both rain and UV radiation, which may allow for self-cleaning performance for the surface and the ability to retain its heat-reflective property over a long period of time. Meanwhile, the "cool cold" cement concrete SH surface exhibited excellent anti-ice rain performance. Because the layer can be easily mortared on the cement concrete substrate, we think it would have great potential for use on building roof and outside walls to reduce air-conditioning energy consumption in the summer. [ABSTRACT FROM AUTHOR]

The development of road network infrastructure is an important component of the economic development of the European Union. Updating of the road network contributes to the integration of the economies of countries into a coherent whole. The road network provides the free movement of citizens, the movement of goods and the effective implementation of various services. The increase in the length of the road network leads to an increase in the financial and material costs necessary to ensure its maintenance and repair. One of the ways to reduce costs is by strengthening the physic-mechanical and operational characteristics of the pavement due to the widespread use of cement concrete. The quality of the pavement of cement concrete depends largely on the rational selection of its composition. This allows a significant increase in the durability of road pavement. The purpose of the research was: the development of recommendations for the rational selection of the composition of the road pavement material of cement concrete, aimed at upgrading longevity, and taking into account its frost resistance grade. According to the goal, the following tasks were developed: the analyses of the climatic zones in which the road network of the European Union is located; the development of a research plan, a selection of the response function and influence factors; the study of physico-mechanical and operational characteristics of the researched material of road pavement; on the basis of the obtained data, the calculation of the complex of experimentalstatistical models, which describe the physico-mechanical and operational characteristics of the road pavement material; on the basis of experimental statistical models, a method was proposed for selecting the rational compositions of the cement concrete pavement road material depending on the conditions of its application. The results presented in the article can be used in engineering and scientific practice for the selection of road pavement from cement concrete for highways. [ABSTRACT FROM AUTHOR]

Abstract In the recent years, there is a strong desire for discovering light-sensitive materials that can exhibit excellent photocatalytic behavior for purifying the pollutants in water or detecting some type of materials via decomposing the chemical bonds, but most of previous photocatalytic materials need an excitation source. Hence, exploring novel photocatalytic materials that can continuously have the photocatalytic behavior, after removal off the excitation source, becomes desirable. In this work, we report a type of double perovskite La 2 MgGaO 6 :Eu2+ blue-emitting afterglow phosphor that can act as a ceramic substrate to immobilize the TiO 2 powder. Our results reveal that exciting with the UV light does not change Eu2+-emission shape and position with changing the Eu2+ doping content, showing the maximum intensity at 385 nm. Moreover, the La 2 MgGaO 6 :Eu2+ phosphor after irradiating with an UV light can show the Eu2+-blue afterglow luminescence, which broadly covers the absorption region of TiO 2. As a result, the UV-converted Eu2+ afterglow ceramic composite, fabricating by the TiO 2 and La 2 MgGaO 6 :Eu2+ blue phosphor, shows the photocatalytic behavior. Our results reveal the afterglow behavior of La 2 MgGaO 6 :Eu2+ help the TiO 2 to absorb the photons, allowing the TiO 2 to perform the photocatalytic behavior for cement concrete-related methyl orange (MO) degradation (∼3.5 h) without external excitation source. Thus, decomposing the MO chemical bonds can allow to detecting cement concrete-related MO degradation. [ABSTRACT FROM AUTHOR]

Highlights • Cement concrete with recycled polycarbonate from electronic waste was elaborated. • Gamma-irradiated recycled polycarbonate improve compressive strength of concrete. • Polycarbonate concentration increments provoke diminution of concrete densities. • Due to irradiation process, polycarbonate particles become textured and less plastic. Abstract Attending the environmental problems caused by polycarbonate, generated by electronic waste, in this work physical and chemical characterization of gamma-irradiated particles of recycled polycarbonate from electronic waste was made by: X-ray diffraction, energy dispersive spectroscopy (EDS), scanning electron microscope (SEM) and digital photography. Cement concrete was elaborated with Portland cement, aggregates, water and gamma-irradiated polycarbonate. The effects of size, concentration and gamma irradiation doses of polycarbonate particles, on the mechanical properties of concrete, were studied. Results show improvement on the compressive strength (up to 12%). The increments in irradiated recycled polycarbonate concentrations provoke diminution of densities and due to irradiation process, polycarbonate particles become textured and brittles. [ABSTRACT FROM AUTHOR]

This paper investigated the effects of glass usage in finely divided form on the properties of cement concrete. The powdered glass was used as admixture, replacing cement in the concrete production process. The sourced glass were washed and dried for some days. The dried glass was then crushed into smaller pieces before grinding to finely divided form. Replacement of cement with powdered glass was done at 0-10% with 2% increment by weight of cement. Using a design mix of 1:2:4, with a constant water cement ratio of 0.6, the workability of fresh specimens were determined using the slump height procedure. The specimens were then poured in 150x150x150mm steel moulds and left for 24 hours. The hardened concrete specimens were cured by complete immersion in water for 7, 14, 21 and 28 days. The result showed that workability increases with increase in admixture content. It further revealed that the compressive strength increases with admixture addition to about 4% powdered glass addition. The compressive strength at 6% addition of powdered glass was also higher than that of the conventional concrete. Thus replacement can be done to about 6% addition of powdered glass by weight of cement. The models developed from the study corroborated well with experimental values as high coefficient of determination values were obtained. The models can thus, be used to predict the compressive strength of powdered glass-cement concrete. [ABSTRACT FROM AUTHOR]

In Poland the climatic conditions in the autumn and winter season are particularly severe for concrete infrastructure. Concrete's resistance to frost and chemical deicing agents determine the durability of cement concrete pavement. An increase in the premature deterioration of airfield pavements exposed to new generation deicing chemicals may suggest that there is a relation between the damages and the application of the deicers. The paper presents selected results of microstructural analysis of the airfield pavements concrete exposed to the deicers based on acetates and formates. Microscopic evaluation was carried out with the scanning electron microscope (SEM). The local chemical compositions of the phases of interest were performed using the Energy Dispersive X-ray analysis (EDX). [ABSTRACT FROM AUTHOR]

Highlights • Waste brucite short fibers processed to nano diameter level with a simple way. • The physical properties of brucite nano-fiber reinforced concrete have been improved. • Nano-fiber concrete superior to ordinary concrete in cost performance. • 8 years traffic practice proves the practicability of nano-fiber concrete. Abstract In this paper, brucite nano-fiber is processed and used as reinforcement to improve the toughness of road cement concrete material. The brucite nano-fiber is obtained by soaking the natural low-coat brucite short fibers in the superplasticizer solution and then agitating in a forced mixer to refine it to the nano meter level. The mechanical properties as elastic modulus, dry shrinkage, anti-frost, thermal expansion, and flexural fatigue performance of the nano-fiber concrete are investigated. The nano-fiber reinforced cement concrete was also put into practice in highway. Results show that nano-fiber concrete has better toughness. Its flexural strength is 7.4% and 17.7% higher than that of the ordinary fiber concrete and the plain concrete, respectively. Its ratio of compression to flexural strengths is 6.4% and 16.1% lower than that of the rest two. Nano-fiber concrete has lower static modulus and higher dynamic modulus. Compared with ordinary fiber concrete and plain concrete, nano-fiber concrete is 41.0% and 61.3% lower in flexural elastic modulus, and is 1.12 and 1.24 times higher in dynamic modulus of elasticity. Nano-fiber concrete has stronger capability to resist dry shrinkage, freeze-thaw damage, thermal expansion and bending fatigue stresses. Compared with ordinary fiber concrete and plain concrete, nano-fiber concrete is 35.7% and 55.9% lower in dry linear shrinkage; 3.2% and 7.9% less loss rate in compression strength, and 1.9% and 4.5% less loss rate in flexural strength after 50 cycles freezing-thawing; 13.9% and 28.7% lower in coefficient of thermal expansion; and 15% and 50% more longer in bending fatigue service life. Nano-fiber concrete is comprehensively superior to ordinary fiber concrete and plain concrete in cost performance. After more than 8 years traffic practice, the nano-fiber concrete test road is still in good condition. [ABSTRACT FROM AUTHOR]