Surface Layer Of Concrete Research Articles

Preparation of nano-TiO2 by waste clay bricks and photocatalytic effect on concrete

In this paper, a composite photocatalyst is prepared by using waste clay bricks to adsorb nano-titanium dioxide (TiO2), and a decorative concrete surface layer is made by using it. Then, it is found that reclaimed clay sand (RCA) prepared by building waste clay bricks has poor workability, with a relative strength between 40% and 80%, but can meet the strength requirements of ordinary building mortar. Compared with RCA, natural sand (NS) has lower water absorption, coarser particles and higher hardness. The relative strength of the mortar prepared using NS is between 50% and 80%, which also meets the basic strength requirements of the mortar. In terms of photocatalytic effect, the decorative concrete surface layer prepared using the composite photocatalyst has a good photocatalytic effect and can effectively degrade nitrogen oxide (NO x ) in automobile exhaust. The decorative concrete surface layer made of NS has lower nitrogen oxide degradation efficiency than RCA. The photocatalytic concrete surface layer prepared using RCA loaded with nano-titanium dioxide has good photocatalytic durability.

ВИКОРИСТАННЯ ГОТОВИХ УЩІЛЬНЮВАЧІВ ШВІВ В ЦЕМЕНТОБЕТОННИХ ПОКРИТТЯХ АВТОМОБІЛЬНИХ ДОРІГ І АЕРОДРОМІВ

Increased requirements for reliability, performance and durability of pavement caused by the increase in vehicle carrying capacity and traffic on the roads. As the domestic and world experience shows, the increasing requirements of the movement are best matched by cement concrete pavements. Stable transport transport performance, high durability give them advantages over pavements built using organic binders. During construction and reconstruction, longitudinal and transverse joints for various purposes are arranged in cement concrete pavements of roads and airfields to prevent deformation and destruction of coating pavements (cracking, chipping of corners and edges of slabs, peeling of the concrete surface layer, the appearance of potholes and sinks, vertical displacement of slabs and their warpage destruction of butt joints and joint fillers). The destruction of pavements, as a rule, takes place in cases where the stresses and deformations arising in the plates exceed the permissible values, as well as in case of failure of the sealing of joints and cracks. Restoring the sealing of expansion joints and cracks are important stages of work to extend the operational life of pavements. A large role on the efficiency of the sealant in the joints and its service life is provided by the deformability of the sealing materials. When choosing a type of sealant, the possible maximum negative and positive air temperatures of the region where the pavements are used are taken into account. Currently, unique sealing materials using polymer compositions have been created. These materials have high technical and operational characteristics and a guaranteed service life of at least 5 years. The sealing or filling of transverse and longitudinal joints in cement concrete pavements is an important factor in ensuring long-term performance of the coating. The experience of using different types of joint sealing materials shows that their proper installation can provide important protective equipment that improves the performance of joints and pavements. In recent years, in foreign practice, the technology of pressing elastic whole or porous rubber profiles into the seam is very often used for sealing joints. In this case, it is possible to carry out work even in wet weather and at low temperatures. Special machines have been developed for the installation of profiles. The article discusses the sealing of transverse and longitudinal seams of cement concrete pavements of roads and airfields with sealing materials, including ready-made seals, the need to use them and study the effect of sealing materials on the design of joints and operational performance of cement concrete coatings in general.

Study on micro structure and composition distribution of concrete surface zone based on fractal theory and XCT technology

Based on the fractal theory, the fractal dimension model of coarse aggregate gradation in concrete was proposed, and the fractal dimension of coarse aggregate gradation in concrete was calculated based on the measured data. The variations of the micro structure, composition distribution and porosity to paste ratio of concrete surface layer were investigated by the methods of X-ray computed tomography (XCT) and profile grinding technology (PGT). Moreover, the content variations of coarse aggregate and paste with depth in concrete surface were also studied. The results show that the coarse aggregate content in concrete surface layer increases but the porosity decreases with increase of depth from concrete surface. Finally, they all tend to be a constant when the depth is larger than a certain value. The porosity to paste ratio of concrete surface decreases with increase of concrete strength. The major composition is cement paste within 0.1 mm of concrete surface, which turns into mortar within 0.1 mm ~ 0.4 mm. The volume fractal dimension of coarse aggregate and the fractal dimension of coarse aggregate gradation in concrete is about 1.35 and 2.68, respectively.

Mechanical Characteristic of Surface Layer of Concrete with Recycled SiC

Abrasion measurement of surface of specific concrete elements is presented in this paper. This article is focus on determination of wear resistance and strength of concrete floor. This concrete contains silicon carbide binder and part of it is recycled origin. This material are high on Mohr hardness scale and are they are suitable for use in indoor and outdoor areas with the heaviest traffic loads. From the results, follows that the even small differences in mixture (using new and recycled binder) has impact on the mechanical parameters. However, it is possible design mixture with recycled binder and reach characteristic of concrete, which are almost similar to the normal concrete.

Evaluating Properties of Asphalt Mixtures Containing polymers of Styrene Butadiene Rubber (SBR) and recycled Polyethylene Terephthalate (rPET) against Failures Caused by Rutting, Moisture and Fatigue

Properties of asphalt mixture play a vital role in structural integrity and performance of flexible pavements structure. In flexible pavements asphalt concrete surface layer consists of asphalt binder, aggregates and in some cased additives. In this research study styrene butadiene rubber (SBR) and recycled polyethylene terephthalate (rPET) used to evacuate their individual and also their combination effects upon moisture susceptibly, rutting and low temperature cracking of asphalt concrete mixture. Three combination of SBR and rPET along with water were vulcanized to from thermoplastic elastomer polymers as bitumen modifier. Then conventional bitumen tests including penetration grade, softening point and rotational viscosity (RV) as well as asphalt mixture tests including resilient modulus, dynamic creep, IDT fatigue and moisture susceptibility tests were performed on binders and asphalt mixture specimens. The test results indicated that SBR and rPET increase viscosity and softening point and stiffen the binders by reducing their penetration grade. Test results of spearmens prepared with modified binders showed higher tensile strength and higher rutting resistance than that of control specimen within the contest of this study it is conclude that modification of bitumen with SBR reduces low temperature stiffness of binder and hence reduces failure of thermal cracking and modification with rPET increases rutting resistance of the mixture at high temperatures.

Modelling of membrane bonding response: part 1 development of an adhesive contact interface element

ABSTRACT The adhesive bonding strength of the membrane layers between the asphalt concrete surface layers and the decks of steel bridges has a strong influence on the fatigue life of orthotropic steel deck bridges (OSDBs). The most important requirement for the application of membrane materials to orthotropic steel deck bridges is that the membrane adhesive layer is able to sufficiently bond to its surrounding material layers. The interfacial properties between the membrane and the layers bonded to it have not been extensively studied in the current orthotropic steel deck bridge system. In this paper, details of the contact interface element utilised to model the interfacial bonding properties will be discussed. Furthermore, the traction-separation material law will be chosen to describe the bonding response of the interfacial properties of the membrane to its surrounding surfacing layers on OSDBs. Some numerical examples, in which various aspects of the finite elements response of the contact interface model will be presented. Utilisation of the model in finite element analyses has enabled the investigation of the response of a 3D orthotropic steel deck bridge subjected to the different traffic loading conditions.

Modelling of membrane bonding response: part 2 finite element simulations of membrane adhesion tests

ABSTRACT The adhesive bonding strength of the membrane layers between the asphalt concrete surface layers and the decks of steel bridges has a strong influence on the fatigue life of orthotropic steel deck bridges (OSDBs). The interfacial properties between the membrane and the layers bonded to it have not been extensively studied in the current orthotropic steel deck bridge system. For the adequate characterisation of the adhesive-bonding strength of various membranes and surrounding materials on OSDBs and for the collection of the necessary parameters for finite element model, details of the membrane adhesion test (MAT) are introduced and simulated by using the adhesive traction-separation interface element which was developed in a companion paper to this contribution (Liu, X., Kasbergen, C., Li, J., & Scarpas, A. (2019). Modelling of membrane bonding response: part 1 development of an adhesive contact interface element. International Journal of Pavement Engineering). Parametric studies of the adhesive contact element utilised for modelling the membrane bonding layer in the MAT test have been performed on the basis of the combination of different critical strain energy release rates and the characteristic opening length in the constitutive model. Comparison of membrane deformation profiles and the in-time debonding force distribution between experimental observations and finite element simulations have been presented.

Effect of Type of Aggregate on Abrasion Resistance of Concrete

Abrasion is the physical wear of a surface due to cyclically recurring dynamic forces and shifts. Therefore, abrasion resistance can be defined as the ability of a surface to resist wear due to friction. The paper deals with the issue of the resistance of concrete surface layers to the effects of abrasion. The research focused on monitoring the influence of different types of aggregate on increasing the abrasion resistance of concrete surfaces. Concrete surfaces with three different types of aggregate were tested: amphibolite, granodiorite and psammite. The concrete class was C35/45. Abrasion was tested using the Böhme method. The highest abrasion resistance after 28 days of maturation was found in concrete surfaces with amphibolite aggregate.

Fracture performance of a PCM-Rich concrete pavement under thermal stresses

ABSTRACT Curling stresses in rigid pavements are the result of temperature gradient through the thickness of the concrete slab. These stresses have a periodic nature, and the induced cyclic flexural curling stresses lead to the cracking of the concrete slab. In a previous research by the authors, a phase change material (PCM)-rich concrete overlay was proposed as an effective method to control this failure mechanism. A PCM-rich concrete overlay is a concrete surface layer that contains a relatively high percentage of PCM. In the previous study, a phenomenological approach was employed, and it was demonstrated that the incorporation of PCM improves the curling fatigue performance of the concrete slab. Using fracture mechanics, this paper builds upon the findings of the previous study, and it serves as a mechanistic verification of the conclusions of the previous work. A modified Paris’ Law was adopted to calculate the cumulative fatigue-fracture damage of the concrete slab due to cyclic thermally-induced curling stresses. The findings of this research demonstrated that the PCM-modified concrete slab undergoes a curling-induced fracture process that is less severe than the slab without the PCM. The impact of this reduction was quantified in terms of an improved fatigue-fracture performance of the pavement.

Study on the compression performance of steel reactive powder concrete columns

In this study, the mechanical properties and failure characteristics of steel reactive powder concrete columns with different strength grades were investigated through compression testing. Six steel reactive powder concrete columns were tested; three columns underwent axial compression testing and three columns underwent eccentric compression testing. The results of the axial compression testing showed that steel and reactive powder concrete could work cooperatively at the initial stage, and the final column failure mode was primarily splitting failure at the end of the column, with the formation of a main crack in the longitudinal direction extending to the middle of the column. The results of the eccentric compression testing showed that the eccentrically loaded steel reactive powder concrete columns had comparatively strong deformability. The columns presented ductile failure mode under the eccentric load with 0.2 eccentricity. The final failure of the column involved a sudden increase in the horizontal crack width on the tension side, the steel flange on the tension side reached the yield state, the reactive powder concrete in the middle of the compressive side was crushed, and the reactive powder concrete surface layer burst open and partially spalled off. According to the test results and with reference to the relevant standards, equations for calculating the approximate ultimate bearing capacities of axially and eccentrically compressed reactive powder concrete columns were proposed.

Detection of Defects in Reinforced Concrete Surface Layer by Using Non-Destructive Testing Method

Detection of Defects in Reinforced Concrete Surface Layer by Using Non-Destructive Testing Method

On micro-level vulnerability of concrete surface layer in process of crystallization of hydrating Portland cement and upon mechanical load

The target of this research is to make a system of data on discontinuity of the cement stone microstructure in concrete. To achieve this, the following issues have to be addressed: a) a justification for the presence of dislocations in cement stone and definition of their type needs to be provided; b) the source of the considered material weakness has to be identified; c) an explanation of formation and propagation of micro cracks starting at the surface and going deeper into the concrete needs to be given; d) an educated guess has to be made for the opening/depth ratio of micro cracks; e) information about the distances between micro cracks in the capillary walls of the cement stone should be obtained; e) binding energy in the calcium silicate crystalline hydrate has to be determined. The research results show that the mechanical properties of crystals and polycrystals in the cement stone (concrete) depend on the ratio of small-angle (θ≤10…150) and large-angle boundaries. Due to a relatively small number of large-angle boundaries, intergranular and plastic flow deformations are dampened under straining, resulting in cleavage in the areas where stress-raisers are found (pores, capillaries, submicrocracks, etc.).

Investigation of Biostability of Concrete Constructions for Special Purpose

Concrete of used sewers is exposed to various aggressive environments. While making concrete pipes for special purposes, special attention is paid to reducing the permeability of the surface layer of concrete. It is possible to increase the operational characteristics of concrete by introducing into the cement system the active components chemically interacting with the cement minerals. When the complex modifier interacts with cement particles, the structure and properties of the modifier undergo qualitative changes. The article presents the results of researching the porosity of the modified cement matrix. It has been established that in the neoplasms of the modified cement matrix of concrete, the quantity of free calcium hydroxide does not exceed 5% that is a necessary condition for getting a corrosion-resistant material. As a result of the analysis of modern technologies, it has been established that physical modification is possible by removing excess mixing water that increases the use of the potential qualities of cement in order to increase the density, impermeability and strength of concrete in the process of compaction of the mixture.

Review of Factors Affecting the Quality of Architectural Concrete

The paper deals with the properties, quality and durability of the exposed concrete. The main part of this paper are characteristic of architectural (sometimes called visible or naked) concrete and the criterion of the quality evaluation of the performed work. This is mainly the colour balance of the subject area, the quantity and the size of the pores, the quality of the raw material and the surface structure. Achieving the quality of architectural concrete is considerably more technologically demanding compared with conventional concrete. This is reflected also in its cost. In conclusion, the problems of surface layers of architectural concrete are summarized. Especially environments can cause faster degradation, reducing the lifetime of the whole construction, but also pointing to one of the main problems in construction, which is technological discipline.

Modelling the influence of root position and growth on pavement tensile crack failure when occurring under three thicknesses of asphaltic concrete

Root-pavement conflicts are a common challenge in urban forest management. Given the expense of pavement installation and the time needed to develop large trees, there is a preference for modelling design solutions to integrate trees and pavement with shared soil volumes. While Finite Element (FE) models are used in pavement analysis and design, and have been used to describe root growth in soils, there are few examples exploring of integration of the two applications with respect to designing urban root zones under pavements. Four series of FE models were developed to test the influence of an asphaltic concrete wearing surface layer thickness and base layer thickness (the top two layers in a pavement design) in surface crack formation from a growing tree root simulation in positions within the top zone of the base layer and below the base layer. The expected pavement damage was defined at places where horizontal tensile stresses exceeded 862 kPa. The testing series were developed from a common group of 18 FE pavement layer configurations using 3 asphalt concrete (AC) thicknesses and 3 granular base thicknesses with a growing root element at 2 root elevations. In the first series, an AC layer of a thickness of 7.6 cm did not exceed the horizontal stresses needed to develop a crack when a simulated root element increased from 3.6 to 5.1 cm when the root element was below the base layer at least 10.16 cm below the bottom of the AC layer. A second series of 77 model runs with a refined root simulation verified the impact of a changed root simulation (shift of element shape with a material modeling change that accounted for soil hardening during deformation). For the second series, a 2.54 cm diameter circular root was expanded to a final size ranging from 3.8 to 10.16 cm. Results of the second series confirmed and added detail to the first, but required a significant increase in computational time to accommodate the added model and data output details. The third series developed root simulations from an initial 0.508 cm diameter (the smallest diameter available in the PLAXIS FEM modeling platform) to a maximum 5.08 cm diameter in a series of 55 tests. The third set allowed a method to observe and compare the colonization step to a series of radial growth steps, which caused minimal influence to the stress state of the AC as a consequence of soil displacements from the root growth. Finally, in the fourth testing series of 58 simulations, we tested a cluster of three root elements at a 10.16 cm spacing 0.635 cm below the AC or the base layer, growing from an initial 2.54 cm to 6.35 cm diameter. Modeling three root elements at the 10.16 cm spacing generated tensile stress-induced cracks in all AC-base-root depth configurations. Displacements in those models exceeded the imposed upward displacement limit of 1.27 cm after doubling in size from an initial 2.54 cm diameter.

Experimental evidence that micro and macrostructural surface properties markedly influence on abrasion resistance of concretes

Surface abrasive wear is a pathological manifestation that compromises concrete floors. Although the abrasion resistance of concretes has been extensively associated with the materials and matrix properties, the influence of the surface layer quality has been less explored. The present work investigated the influence of micro and macrostructural properties related to the surface layer as compared to matrix properties on the abrasion resistance of concretes with different materials and proportions. A decrease of hardness and microhardness was observed, as well as an increase of total porosity and pore diameters, in concretes with 0.6 water/binder (w/b) ratio and when cured in a heat box, which were associated with an increase of the abrasive wear. Interestingly, silica fume (SF) improved the abrasive resistance of the surface but only of the composites with 0.4 w/b ratio. In contrast, we verified a beneficial effect of SF in concretes with either 0.4 or 0.6 w/b ratio on the matrix properties. Altogether, the data demonstrated that the micro and macrostructural surface properties markedly influenced in the abrasion resistance, indicating that this parameter may be more related to the quality of the concrete surface layer than to the matrix performance.

Atmospheric chloride deposition in field concrete at coastal region

A field research is carried out at atmospheric marine zones for evaluating the chloride deposition behavior of concrete structures under multiple geographic and environmental factors. Geographic factors of offshore distance, elevation, concrete surface orientation and building barrier, and environmental factors of temperature variation and rainfall on chloride deposition of concrete surface layer are evaluated. Our investigation demonstrates that chloride deposition content is significantly affected by offshore distance, elevation, and building barrier. Effect of concrete surface orientation on chloride deposition depends on the presence of building barrier. Besides, the large temperature variation and rainfall facilitate the chloride deposition.

The effect of ageing and drying on laser scabbling of concrete

Laser scabbling of concrete is a process by which the surface layer of concrete is removed through the use of a high power (low power density) laser beam. In order to understand how the age and treatment of structures may affect the laser scabbling process, the aim of the research presented in this paper was to establish a relationship between laser interaction time, surface temperature and volume removal for cementitious materials of different ages and different degrees of saturation. The investigation focussed on (i) the effect of age on saturated specimens and (ii) the effect of prolonged drying. The results show that drying of specimens had the largest effect on scabbling. The effect of age on saturated specimens was small for PFA + OPC pastes, mortars and concretes, but significant for OPC pastes, where the volume of scabbling dramatically reduced with age.

Study the effect of carbon nanoparticles in concrete

Carbon nanoparticles, whether in the form of nanotubes, fibers or graphenoids, can under suitable application improve mechanical as well as durability properties of cement composites. The use of carbon nanoparticles in concrete is limited by their relatively high cost but also by the difficulty of their dispersion in concrete. The experimental research was focused on the issue of dispersion of carbon nanotubes (CNT) and the effect of CNT in concrete. Concrete with different doses of multi-walled CNT (0.0015 % and 0.012 % from the weight of cement) was prepared. The dispersion of CNT, superplasticizing admixture based on polycarboxylate ether, and water was carried out using ultrasonic cavitator. The impact of various doses of CNT on the strength of concrete after 7 and 28 days and frost resistance of concrete after 100 cycles was observed. The best results were achieved with the addition of 0.012 % CNT of cement weight, representing a dose of 43.2 g per 1 m3 of concrete. The increase in compressive strength was 11.9 %, 17.3 % in flexural strength, 15.2 % in the tensile splitting strength and 26.9 % is the tensile strength of concrete surface layers after 28 days compared to the reference samples without CNT. Changes in properties of concrete with the addition of CNT were observed also in the case of frost resistance of concrete (8 % increase in the coefficient of frost resistance of concrete with the addition of 0.012 % CNT of cement weight).

Detecting the depth of weak layer in concrete using R-wave dispersion techniques

This study used the dispersion of R-waves in layered structures to detect the thickness of the deteriorated concrete surface layer. This study employed the mechanical impact to generate stress waves in tested objects. A receiver was placed on the impacted surface to record surface displacements caused by the arriving waves, which were subsequently fed into Morlet Wavelet Transform (MWT) to convert the displacement waveforms into spectrograms to observe R-wave dispersion characteristics. This study first conducted numerical analysis to assess the feasibility of the research concept; numerical models with a surface deteriorated layer of 30, 50, and 70 mm in thickness were employed to explore the influence of bottom surface reflection, contact time of impact, and receiver locations. Subsequently, experiments were carried out on concrete specimens containing weak layers to verify the numerical analysis results. Both the numerical and experimental results revealed that when the receivers were sufficiently far from the point of impact, dispersion occurs among the R-waves propagating along the deteriorated surface layer because R-wave velocity increases with wavelength. Furthermore, the dispersion curves all exhibit a turning point that signifies the rapid increase in wave velocity with wavelength, and this turning point corresponds to a wavelength that is approximately 1.7 times the thickness of the deteriorated layer. This is an effective rule for estimating the deteriorated layer's thickness.