Cementitious Layer Research Articles

Numerical study and experimental validation of heat transfer in a CenoPCM reinforced multi-layered meta-material wall for energy efficient buildings

Increasing concerns about energy consumption have led to an increasing need for buildings that can efficiently manage heat transfer and reduce reliance on active heating or cooling systems. The combination of cenosphere cementitious layers, meta-material layers, and cenoPCM in the proposed wall aims to overcome the limitations of traditional construction materials and provide a potential solution for improved heat transfer control. This study presents numerical modeling and simulations of the proposed wall using SolidWorks and ANSYS software. The thermal performances are evaluated with both heating and cooling loads to determine the thermal efficiency of selected PCMs as well as the Meta-Material Wall Systems. Analysis indicates that the heat transfer between the outer and inner layer is restricted to around 30°C, which is almost 20°C less than the outer wall temperature, while applying heating and cooling loads simultaneously at the outer and inner layers for 120 min. Practical application In this study the heat transfer in a cenosphere Phase Change Material reinforced Multilayer Meta-material Wall (cenoPCM-MMW) is analyzed numerically as well as experimentally. This study provides real insight to the optimization of heat transfer in buildings, which has potential practical application in the form of improved building energy efficiency. The proposed ceno cementitious layer could, for example, act as a surface finishing layer for buildings which are located in high ambient temperature zones leading to reduced indoor temperature, improved thermal comfort, and reduced HVAC-related energy use due to its heat storage capacity.

Experimental research on bonding mechanical performance of the interface between cementitious layers

Abstract Interfaces of cementitious layers have widely existed in construction projects, and they are the weakest part of the whole building. In this article, laser scanning and ultrasonic pulse, splitting tensile, and semi-disc fracture tests were carried out to study the bonding performance of cementitious layers. Different performance metrics, such as splitting tensile bond strength, ultrasonic pulse velocity, and attenuation of first arrival, were used to evaluate the bonding characteristics of the concrete layers. The results revealed that the parameters of the interface curve decreased, and the mechanical properties of the interface became weaker with an increase of the interval time. The amplitude of the first wave was more sensitive to the presence of the interface than the ultrasonic pulse velocity. Finally, the relationships between the performance metrics were analyzed. The fracture toughness of model I and mode II was highly correlated with the parameters of the micromorphology of the layered concrete, and the correlation coefficient is not less than 0.9511. The fracture toughness of mode I was strongly related to the splitting tensile strength, with a correlation coefficient of not less than 0.9744. This study was useful for the future study of the mode I and I fracture performance, the morphology, and other physical properties of cementitious layers.

Data-Driven Integrated Decision Model for Analysing Energetic Behaviour of Innovative Construction Materials Capable of Hybrid Energy Storage

Aligning the European Union goals for climate neutrality by 2050 and the ambition for carbon equivalent emissions reduction to almost half by 2030 demands the exploration of alternative decarbonisation pathways. Energy consumption across all sectors is identified as a crucial contributor to this challenge, with a number of legislative and regulatory frameworks and commitments to be introduced every year. In response to these trends, the concept of exploiting a building’s thermal mass through the integration of phase change materials (PCMs) enhances the ability of building elements to reserve and deliver large amounts of energy during phase transitions. However, the incorporation of PCMs into building elements requires the thorough understanding of their thermal behaviour. This study evaluates and predicts the thermophysical properties of mineral particles carrying PCMs and coated with a cementitious layer able to be utilised as fillers in construction applications. By employing deep learning and predictive modelling techniques, the numerical data-driven model developed in this paper enhances accuracy and efficiency in property estimation and prediction, facilitating material selection, system design, and optimisation. A model in a MATLAB simulation environment is presented, evaluating and predicting the thermophysical properties of semi-organic particles able to enhance building envelope thermal mass as a hybrid energy storage solution. These findings show the time needed for a building block to undergo cooling, demonstrating a clear upgrade in the thermal discharge of the walls. Substituting traditional EP with PCM-enhanced EP leads to a minimum reduction of 1 °C per hour in the discharge rate, thereby extending the comfort duration of indoor spaces without necessitating additional space heating. These models offer the potential for assessing diverse material compositions and usage scenarios, offering valuable insights to aid decisions in optimizing building energy efficiency.

Compressible cementitious composite materials: Multiscale modeling and experimental investigation

Tunnel linings installed in difficult geological conditions characterized by a high expansion potential, such as Opalinus Clay and rocks containing anhydrite, may exhibit a loss of integrity due to excessive ground deformations in case water penetrates the rocks. One of the potential remedies against lining deterioration and failure of the tunnel structure is the incorporation of a compressible cementitious layer around the tunnel. This compressible layer serves as a cushion that protects the tunnel structure by tolerating a certain amount of deformations prior to collapse. The deformation capacity of the compressible layer can be enhanced by introduction of various soft inclusions or air bubbles in the cementitious mix. However, such soft inclusions reduce the overall elasticity modulus and strength of the composite. Hence, it is crucial to determine the optimal mix that provides the required compaction potential without compromising on stiffness and strength. For this design purpose computational modeling can be adopted. The model should be able to account for the material properties of the individual components and their volume fraction, which strongly influence the overall behavior of the cementitious composite, and to capture the main features characterizing compressible composites, such as a yielding plateau after a certain threshold loading has been reached. The compaction process of such a composite is described by a voxel model with a discrete distribution of material properties, where the voxels are compacted by applying an Eigenforce when the local stress state reaches a threshold value. This threshold is determined within the framework of continuum micromechanics on the scale of individual inclusions. The model predictions are compared with data from experimental investigations on the compression behavior of different cementitious mixes.

An introduction to Geosynthetic Cementitious Composite Mats and Barriers – a new approach to lining canals

A new class of geosynthetic has recently emerged known as GCCMs (Geosynthetic Cementitious Composite Mats) defined by the ASTM D-35 committee in 2017 as ‘a factoryassembled geosynthetic composite consisting of a cementitious layer contained within a layer or layers of geosynthetic materials that becomes hardened’. GCCMs consist of a three-dimensional fibre structure filled with a dry cement/concrete mix, overlain by a hydrophilic filter layer and underlain by a watertight membrane, which is typically a polymeric film. The material is delivered in its dry format and unrolled into place using similar installation techniques to traditional geosynthetics. Once in place, it is hydrated by spraying with water and the cement/concrete mix hardens. The result is a watertight polymeric film which is overlain by a protective fibre-reinforced concrete layer. GCCMs have been in use since 2009 and are predominantly used for the lining of water channels for small scale drainage. More recently a variant of GCCMs has emerged which integrates a geomembrane liner onto the rear surface which allows the joints to be thermally welded. These are known as Geosynthetic Cementitious Composite Barriers (GCCBs). It is estimated that Egypt has more than 110,000 kilometers of canals comprised of approximately 30,000 km of public canals (first and second level) and 80,000 km of private third-level canals (mesqas) and irrigation ditches. A common problem associated with canals, is seepage. Seepage can result directly in water loss through the network or result in waterlogging of adjacent land. In the case of land used for cultivation, waterlogging can reduce crop yields or cause salinization of the soils. This does not only occur in earthen canals, but also in concrete lined canals, particularly those that have experienced cracking, scour, panel separation or damage. It is also a common misconception that concrete lining of canals is an effective method of mitigating seepage losses. The 25-year study performed by the USBR indicates that concrete over geomembrane has a 95% effectiveness at reducing seepage through canals1. This abstract introduces a revolutionary new class of materials called Geosynthetic Cementitious Composite Mats (GCCM’s), specifically Type II GCCM’s to ASTM D8364 for lining of bulk water transportation canals. The Type II GCCM in question consists of concrete encapsulated by between two geotextile layers with a minimum 1mm thick LLDPE geomembrane backing which can be thermally welded to produce a testable and low permeability joint, per ASTM D5820, with air channel testing to ensure a leak free installation. Because it is a composite of concrete and geomembrane in a single application, installation can occur as a one-stepprocess imparting both cost and time savings to the project. The abrasion resistance of the concrete layer is 3.5 times that of typical 20Mpa concrete typically used for canal applications. With a design life of more than 50 years, this new product classification will provide a feasible, long-term solution to help preserve and protect fresh, clean water, one of Egypt’s most precious – and ever more scarce – natural resources.

Novel cement-based sandwich composites engineered with ground waste tire rubber: design, production, and preliminary results

The challenge of making a structure as light and eco-friendly as possible without sacrificing strength is fundamental in the current construction design. Sandwich technology is well-established in lightweight design since the separation of two thin face sheets by a lightweight core allows for outstanding excellent mechanical properties combined with a high strength-to-weight ratio. The aim of this study was to design and characterize newly developed cement-based sandwich structured composites using rubber-concrete mixes as a core layer and stiff face sheets made of ordinary concrete. It was attempted to combine the high mechanical strength and stiffness of the outer cementitious layers with the technological characteristics of the rubberized core to achieve a final product having optimized properties in terms of acoustic damping, toughness, and load-bearing capacity. The sandwiches were made by two different rubberized cores, involving the use of selected rubber particles from waste tires as a total aggregate fraction of the mix. Static and dynamic mechanical testing revealed better performance of sandwich composites in terms of flexural strength, stiffness, energy absorption, and ductility with respect to the monolithic rubberized concrete materials. Acoustic insulation test highlighted very good noise damping characteristics in the high-frequency range. The physical-mechanical characteristics of the core greatly influenced the technological behavior of sandwich samples due to the significant impact of the rubber size gradation on the rubber-concrete's characteristics. Based on the discovered performance, sandwich composites were suggested for low-load paving unit applications, combining reduced weight with satisfactory mechanical and acoustic properties.

Use of Steel Slag as an Alternative to Aggregate and Filler in Road Pavements.

Today the use of Construction and Demolition Materials (CDM) can be considered as a suitable solution for the construction or the rehabilitation of road pavements. In this context, it is central to minimizing waste production, favoring the reuse through new production cycles to replace virgin natural raw materials. As illustrated in this study, steel slag has mechanical properties that justify its use as aggregate in the manufacture of bituminous mixes. In road construction, their use is focused on the substitution of fine aggregate and filler in bituminous mixtures. Mechanical characterizations, Marshall stability and indirect tensile resilient modulus (ITSM) tests were used to evaluate the laboratory performance of the mixtures. The research aims are to provide the use of these materials for the construction of the entire road pavement structure; in this study authors used these materials both in the characterization of cementitious layers and in those with bituminous conglomerate. In both cases, the use of steel slag has favored an increase of stiffness in the mixtures.

Research and analysis of processes occurring during abrasive wear of materials with heterogeneous cementitious structures

The article considers the impact of hardness and the number of solid-phase inclusions, as well as the properties of steels with ferritic, austenitic and martensitic matrices with heterophase cementitious structures on wear resistance. It is demonstrated that to ensure high wear resistance and impact toughness, solid phase particles in the structure of a heterophase metal material must be isolated from each other by sections of a relatively viscous matrix. Such structures can be obtained on the surface of a part or tool by surfacing, chemical-thermal treatment, and other methods. The results of calculations of the hardness of steel with different content of the carbide phase in its structure and the specific strain energy absorbed by the cementitious layer from the relative content of carbides in the ferritic, austenitic and martensitic matrices are presented. The contribution of carbide particles to determining the level of wear resistance of a two-phase material with different amounts of them in steels with different matrices is evaluated.

An Experimental Study Examining the Size Effect on the Compressive Dynamic Performance of Nuclear Power Containment Concrete

To study the size effect of nuclear power containment concrete (NPCC) under compressive dynamic performance, the cube concrete specimens with 3 different cube sizes were measured at 10 different loading strain rates using a hydraulic servo, and the failure mode and compressive strength of NPCC were compared and analyzed under different loading conditions. Based on the comparative analysis of experiment results, the following conclusions can be drawn: the effect of loading strain rate has caused NPCC to develop from static strain rate, mainly cement cementitious layer damage and uniform distribution of cracks, to dynamic strain rate, where there are partial coarse aggregate failures and oblique cracks as the main crack distribution. Due to the size effect, the integrity of large‐scale NPCC specimen after compression failure is relatively high. With the increase of loading strain rate and decrease of cube size, compressive strength of NPCC is gradually increased, and, with the increase of loading strain rate, the size effect on the mechanical properties of NPCC becomes more significant. Moreover, this paper quantitatively analyzes the influence of the coupling effect of strain rate and size effect on the compressive strength of NPCC, and its mechanism is discussed in depth. The research results are of great significance to the safety of nuclear power concrete containment.

Microstructural Characterization of 3D Printed Cementitious Materials.

Three-dimensional concrete printing (3DCP) has progressed rapidly in recent years. With the aim to realize both buildings and civil works without using any molding, not only has the need for reliable mechanical properties of printed concrete grown, but also the need for more durable and environmentally friendly materials. As a consequence of super positioning cementitious layers, voids are created which can negatively affect durability. This paper presents the results of an experimental study on the relationship between 3DCP process parameters and the formed microstructure. The effect of two different process parameters (printing speed and inter-layer time) on the microstructure was established for fresh and hardened states, and the results were correlated with mechanical performance. In the case of a higher printing speed, a lower surface roughness was created due to the higher kinetic energy of the sand particles and the higher force applied. Microstructural investigations revealed that the amount of unhydrated cement particles was higher in the case of a lower inter-layer interval (i.e., 10 min). This phenomenon could be related to the higher water demand of the printed layer in order to rebuild the early Calcium-Silicate-Hydrate (CSH) bridges and the lower amount of water available for further hydration. The number of pores and the pore distribution were also more pronounced in the case of lower time intervals. Increasing the inter-layer time interval or the printing speed both lowered the mechanical performance of the printed specimens. This study emphasizes that individual process parameters will affect not only the structural behavior of the material, but they will also affect the durability and consequently the resistance against aggressive chemical substances.

Design of semi-rigid type of flexible pavements

The primary objective of the study presented in this paper is to develop design curves for performance prediction of stabilized layers and to compare semi-rigid flexible pavement designs between the empirical AASHTO 1993 and the mechanistic-empirical pavement design methodologies. Specifically, comparisons were made for a range of different sections consisting of cementitious layers stabilized with different types and percentages of additives. It is found that the design thickness is influenced by the type of soil, additive, selection of material property and design method. Cost comparisons of sections stabilized with different percentage and type of additives showed that CKD-stabilization provides economically low cost sections as compared to lime- and CFA-stabilized sections. Knowledge gained from the parametric analysis of different sections using AASHTO 1993 and MEPDG is expected to be useful to pavement designers and others in implementation of the new MEPDG for future pavement design.

Cement-waste interactions: Hardening self-compacting mortar exposed to gamma radiation

For the disposal of high level radioactive waste and for attenuation of the emitted radiation, the Belgian supercontainer concept considers the use of cylindrical concrete containers: the radwaste (encapsulated in a canister and stainless steel overpack) is embedded in a hardened self-compacting concrete buffer, and for closure of the supercontainer the remaining gap is filled by casting a self-compacting mortar (filler and lid). As a consequence, this cementitious layer, surrounding the radwaste, will be exposed immediately to the heat-emitting radioactive waste and gamma radiation with dose rates up to 20 Gy/h during hardening and hydration of the cementitious matrix.In this research study, the effect of gamma radiation on the mechanical properties (e.g. compressive strength) and the microstructure of the cementitious samples is investigated thoroughly. By means of compressive strength determination and by analysing the microstructure of the cementitious samples, the effect of gamma radiation during the hardening process of the samples is identified. Small self-compacting mortar cubes were cast and irradiated immediately by gamma rays during hardening. The effect of the total absorbed dose (Gy) and the applied dose rate (Gy/h), in combination with different hardening times at first exposure and total irradiation times is determined. Furthermore, the impact of the composition of the cementitious mortar (e.g. by changing the cement type and the water-to-cement ratio (W/C-ratio)) is investigated.Throughout the test program it was found that a strength loss due to gamma irradiation can be expected, influenced by the total received dose and by the applied dose rate. Furthermore, the age at which irradiation starts (hardening time at first exposure), plays a role in the effect of the gamma irradiation. A correlation between the strength of the mortar samples and its microstructure is found by means of fluorescence microscopy on thin sections and nitrogen adsorption tests: by applying gamma radiation the capillary porosity, the pore volume distribution and the specific surface of the pores is affected. Scanning electron microscopy (SEM) also revealed a change in microstructure due to gamma radiation.

Rubber modified concrete improved by chemically active coating and silane coupling agent

In the study, a new approach was employed to improve the performance of rubber modified cement concrete by developing a cementitious coating layer around rubber particles with silane coupling agent. To validate the effectiveness of the approach, coated and uncoated rubber modified concrete were evaluated through laboratory experiments. The compressive strength, split tensile strength, chloride ion resistance, and energy absorption capability were characterized through laboratory tests for concrete containing different contents of crumb rubber. The results show that the compressive and split tensile strength of the concrete incorporating coated rubber improved by 10–20%, compared to concrete with uncoated rubber. Although concrete with uncoated rubber exhibited lower chloride ion resistance than control concrete without rubber, concrete with coated rubber could maintain chloride ion resistance similar to that of control concrete. The energy absorption capability of concrete was also improved through the cementitious layer developed using silane coupling agent.

Nonwoven Geotextile Interlayers in Concrete Pavements

Pavement engineers are constantly seeking proven innovative concepts with the potential to improve pavement performance while reducing costs. An example of such a concept is the use of a nonwoven geotextile as an alternative to hot-mix asphalt between cementitious layers. Proven by German engineers to be effective, this concept is not common or widespread in the United States. However, as part of a recent effort to demonstrate the use of nonwoven geotextile interlayers as concrete pavement interlayers, initial recommendations for materials specifications and better construction practices were developed. Implementation of a nonwoven geotextile interlayer was successful in two recent field trials in Missouri and Oklahoma. The material proved to be cost-effective, required minimal training and equipment during construction, and could be placed rapidly. As a result, nonwoven geotextiles have the potential to be a viable alternative to more conventional materials as an interlayer in U.S. pavements.

The Interphase Model for the Analysis of Joints in Rock Masses and Masonry Structures

To study the response of cementitious joints in rock masses or masonry structures, the model of interphase is considered for which the contact stresses and strains interact with the internal stresses or strains within the joint. The frictional slip and sliding effects are then combined with the inelastic deformations of the joint. The constitutive model of the joint is analysed by assuming two interfaces separating the joint from the adjacent material. The case of a cementitious layer interposed between two rigid bodies is treated in detail.

Effects of anticaking agents on the thermodynamics and kinetics of water sorption by potash fertilizers

Equilibrium water vapor pressures and kinetics of water sorption on potash fertilizers (KCl) were determined by a calorimetric method. Enthalpy changes for water sorption were estimated from the temperature dependence of equilibrium vapor pressures. Treatment of the fertilizers with anticaking agents had no effect on the measured parameters. Anticaking agents apparently prevent cementitious crystals from growing between particles either by preventing contact of surface solution film or by modifying the crystal habit of the cementitious layer, instead of by slowing or diminishing the sorption of water.

Water Quality Improvements Resulting from FBC Ash Grouting of Buried Piles of Pyritic Materials on a Surface Coal Mine

A 37 acre surface coal mine in Clinton County, Pennsylvania, was mined and reclaimed between 1974 and 1977. Buried pyrite-rich pit cleanings and tipple refuse were found to be producing severe acid mine drainage (AMD). The pyritic material is located in discrete piles or pods in the backfill. The pods and the resulting contaminant plumes were initially defined using geophysical techniques and confirmed by drilling. Isolating the pyritic material from water and oxygen will prevent AMD production. A grout, composed of fluidized bed combustion (FBC) ash and water, was used in two different approaches that attempted pyrite isolation. Pressure injecting grout directly into the buried pods to fill the void spaces within the pods and coat the pyritic materials with a cementitious layer was the first approach. In the second approach, pods that would not accept grout because of a clay matrix were capped with the grout to isolate the pyrite from percolating water. The grout was also used in certain areas to blanket or pave the pit floor to prevent dissolution of clays, which are a suspected primary source of high aluminum (Al) concentrations at this site. Monitoring wells have been sampled since 1990 to monitor changes in themore » water quality resulting from grouting efforts. Grouting occurred during the summers of 1992 and 1993. Statistically significant water quality improvements have been noted as a result of the grouting, although results are varied. Any water quality improvements resulting from the grouting are expected to be permanent because of the nature of the cementitious grout.« less