Properties Of Cementitious Composites Research Articles

Data-driven machine learning approach for exploring and assessing mechanical properties of carbon nanotube-reinforced cement composites

Traditional experimental investigation on the mechanical properties of cement composites is deprecated due to the intensive time and labor involved. Existing predictive models can hardly map the complicated relationships among mechanical attributes and behavior. This study first adopts machine learning to predict the mechanical properties of carbon nanotube (CNT)-reinforced cement composites. For this purpose, predictive models are trained on the previously published experimental data and results demonstrate that machine learning models present better generalization ability and predictive performance than the traditional response surface methodology. A sensitivity analysis indicates that the factor having the maximum influence on compressive strength is the length of CNTs, whereas that having the maximum influence on flexural strength is the curing temperature. Thus, it can be concluded that compared with the traditional experimental investigation and regression methods, machine learning can efficiently and accurately predict the mechanical properties of CNT-reinforced cement composites.

Effect of Wood Biomass Ash Storage on the Properties of Cement Composites.

Since ash from wood biomass mostly ends up in landfills, recent research has focused on finding its economic and environmental added value as a potential new raw material in the construction industry. However, for wood ash to be used on an industrial scale in construction, a strategy for its proper storage must be defined. Proper storage of WBA is important to ensure quality control for applications in cementitious composites. This work investigated the aging of wood biomass ash (WBA) collected from five different power plants in Croatia and its influence on the performance of cementitious composites. WBA and cement pastes were investigated at different aging times (up to one year) using thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), isothermal calorimetry and initial and final setting times. The results showed that storage of WBA in closed and open containers resulted in carbonation and hydration of mainly free lime and periclase, respectively, which affected the reactivity and setting times of WBA cement pastes.

Sound-Absorbing and Thermal-Insulating Properties of Cement Composite Based on Recycled Rubber from Waste Tires

This article describes an experimental study aimed at investigating the potential use of recycled rubber granulate from waste tires of fractions 0/1 and 1/3 mm in cement composites as a 100% replacement for natural aggregates. The use of waste in the development and production of new building materials represents an important aspect for the sustainability and protection of the environment. This article is focused on the sound-absorbing and thermal-insulating properties of experimental cement composites based on recycled rubber from waste tires. The article describes the grain characteristics of recycled rubber, sound absorption capacity, thermal conductivity and strength characteristics. The results of this research show that the total replacement of natural aggregate with recycled rubber in cement composites is possible. Replacing natural aggregate with recycled rubber has significantly improved the thermal and acoustic properties of the prepared cement composites, however, at the same time; there was also the expected decrease in the strength characteristics due to the elasticity of rubber.

Physicochemical and Piezoresistive properties of smart cementitious composites with graphene nanoplates and graphite plates

Graphene nanoplate (GNP) and graphite plate (GP) are promising functional nanofillers for smart self-sensing cementitious composites. The effects of GNP and GP on physicochemical, mechanical and piezoresistive properties of cementitious composite were investigated in this paper. The results show that cement hydration was accelerated with the increased amounts of GNP and GP because of nucleation effect. The electrical resistivity of GNP-cementitious composites was always lower than the counterpart with GP with the same concentration. On the other hand, percolation occurred for the GNP/cementitious composites at the dosages from 2 to 3% (by weight), while it never happens for the GP/cementitious composites. Moreover, the GNP/cementitious composites reached the maximum mechanical strength when the GNP content was 1.0%, while for the GP/cementitious composites, only minor strength improvement was obtained with a dosage of 0.5% GP. As for the piezoresistivity, the cementitious composites with GNP exhibited higher fractional changes of resistivity. Irreversible resistivity happened for 2–3% GP/cementitious composites subjected to cyclic compression, due to the poor and loose microstructures. The outcomes are expected to provide an insight into the application of GNP/cementitious and GP/cement composites as cement-based sensors for the future structural health monitoring.

Investigation of the Effect of Seawater and Sulfate on the Properties of Cementitious Composites Containing Silica Fume

Concrete consumes over two billion tons of freshwater every year and 75 % of regions of the world will become water shortages in 2050. Because of increasing freshwater scarcity seawater may become reasonable as an alternative mixing and curing water for concrete. In this study, seawater (SW) was utilized for mixing and curing of concrete and investigated the seawater and sulfate on the properties of cementitious composites containing silica fume (SF). Hence, SF was replaced with the cement at ratios corresponding to 0 %, 2.5 %, 5 %, 7.5 %, 10 %, 12.5 %, and 15 % by weight of cement, and SW and tap water (TW) were used as mixing water in the production of cementitious composites. Thus, the effect of SW on the properties of fresh cement pastes and the flexural and compressive strengths of 7-day, 28-day, and 90-day old cementitious composites were examined. Additionally, the lengthening change values of cementitious composites containing SF that were kept in 5 % Na2SO4 solution for 7-day, 28-day, and 90-day were determined. The SF delayed the setting period while increasing the water requirement of the cement paste. It is determined that the SW accelerated the setting period of cement. In the case when 10 % SF in cementitious composites was used, the maximum compressive and flexural strengths were obtained for cementitious composites produced by mixing with SW and SF fume at an age corresponding to 28-day and 90-day. It was observed that the length change of the cementitious composites decreased due to the increase in the SF replacement ratio.

Electromagnetic shielding properties of cementitious composites containing carbon nanofibers, zinc oxide, and activated carbon powder

Exposure to electromagnetic radiation is known to cause many adverse effects such as malfunction of electronic devices and health problems in humans. Since currently used metallic shields suffer from various drawbacks, using construction materials that would provide the same amount of shielding has become a novel research area in the construction industry. Set of experiments were carried out to find the effect of carbon nanofibers, zinc oxide, and activated carbon powder on electromagnetic interference shielding in cementitious composites. Additionally, the impact of these additives on mechanical and electrical conductivity was measured. For these experiments, four different types of carbon nanofibers were used to establish the best type of carbon nanofibers. Different contents of each additive were mixed into the cementitious composite to find the optimal content of each additive. These three different types of additives were then combined with 12 mm unsized carbon fibre within the cementitious matrix. Effects of the hybrid composites were measured similar to previous tests to find out the best combination of additives that would provide the optimum amount of electromagnetic shielding. Electromagnetic shielding tests were carried out within the frequency range of 30 MHz to 1.5 GHz according to ASTM D4935 – 18 standard method. Results showed that the inclusion of individual additives did not have a significant impact on the electromagnetic shielding properties. The best shielding properties were obtained when 0.5% of activated carbon powder was combined with the carbon fibre, which was 42.5–60.0 dB.

Radiative cooling potential of cementitious composites: Physical and chemical origins

Passive radiative cooling includes spontaneously cooling a structure by reflecting and emitting light through atmospheric window (8 μm–13 μm) into the cold universe. This paper involves a systematical study on maximizing the radiative properties of cementitious composites by optimizing constituents and microstructures. Relatively high hemispherical solar reflectance (82 ± 2) % and middle infrared (MIR) emissivity (87 ± 2) % were achieved simultaneously, allowing for an inner temperature drop of 12 °C in field test. Whiter surface, micro-magnitude pore size and TiO2 particle diameter all lead to higher reflectance in visible and near-infrared (VIS- NIR, 0.4 μm–2.5 μm) region. From the hydration products, complex infrared absorbance of O–H bonds yields low reflectance, while O–H, Si–O, Si–O–Si bonds stretching vibrations guarantee high emissivity. CaCO3, whether added as admixture or formed by carbonation, significantly increases the VIS reflectance. Both numerical simulation and field test demonstrate great potential of utilizing radiative cooling cementitious composites for building energy saving.

Nanomaterials in Cementitious Composites: An Update.

This review is an update about the addition of nanomaterials in cementitious composites in order to improve their performance. The most common used nanomaterials for cementitious materials are carbon nanotubes, nanocellulose, nanographene, graphene oxide, nanosilica and nanoTiO2. All these nanomaterials can improve the physical, mechanical, thermal and electrical properties of cementitious composites, for example increase their compressive and tensile strength, accelerate hydration, decrease porosity and enhance fire resistance. Cement based materials have a very complex nanostructure consisting of hydration products, crystals, unhydrated cement particles and nanoporosity where traditional reinforcement, which is at the macro and micro scale, is not effective. Nanomaterials can reinforce the nanoscale, which wasn’t possible heretofore, enhancing the performance of the cementitious matrix.

Enhanced workability, durability, and thermal properties of cement-based composites with aerogel and paraffin coated recycled aggregates

The use of construction and demolition (C&D) wastes in building materials is a key step toward a sustainable construction industry. In this context, the application of recycled concrete aggregates (RCAs) in cement composite mixtures has been investigated by various researchers. The results available in the literature indicate that cement mortar adhered to the surface of RCAs leads to high water absorption and large porosity in cementitious mixtures. As a result, lower workability, durability, and mechanical properties in comparison to conventional aggregates are often known as the main attributes of mixtures containing RCAs. Additionally, improving the thermal energy storage capability of RCAs by using high-performance thermal insulation materials, such as phase change materials (PCMs) and aerogel can assist in minimizing the energy consumption in buildings. Accordingly, this paper aims at characterizing RCA mixtures with enhanced workability, durability, and thermal properties. The effect of using paraffin coated recycled concrete aggregates (PCRAs) and aerogel aggregates on the mechanical, thermal, and durability properties of cement composites are investigated in this paper. Results of dry density, compressive strength, water absorption content, permeable voids, thermal conductivity, rapid chloride migration test (RCMT), capillary water absorption, and scanning electron microscopy (SEM) tests along with energy-dispersive X-ray spectroscopy (EDX) are reported to evaluate the effect of several variables on the investigated concrete mixtures. Results of the conducted tests indicate that using PCRA significantly improves the durability characteristics of mixtures such as water absorption content, permeable voids, and RCMT, while it slightly decreases the compressive strength of mixtures with respect to the control mixture. In addition, aerogel aggregates significantly improve the thermal conductivity of mixtures while reduced the mechanical and durability characteristics.

Review of recent developments in cement composites reinforced with fibers and nanomaterials

The quest for high-performance construction materials is led by the development and application of new reinforcement materials for cement composites. Concrete reinforcement with fibers has a long history. Nowadays, many new fibers associated with high performance and possessing eco-environmental characteristics, such as basalt fibers and plant fibers, have received much attention from researchers. In addition, nanomaterials are considered as a core material in the modification of cement composites, specifically in the enhancement of the strength and durability of composites. This paper provides an overview of the recent research progress on cement composites reinforced with fibers and nanomaterials. The influences of fibers and nanomaterials on the fresh and hardened properties of cement composites are summarized. Moreover, future trends in the application of these fibers or of nanomaterial-reinforced cement composites are proposed.

Piezoresistivity performance of cementitious composites containing activated carbon powder, nano zinc oxide and carbon fibre

Intrinsic self-sensing cement-based structures or sensors have a great potential for structural health monitoring applications, which can be achieved by incorporating conductive functional fillers into the cementitious composites. This study examined the mechanical, electrical and piezoresistivity of two types of cementitious composites, one with mono activated carbon powder (ACP)/nano zinc oxide (ZnO) and other carrying a hybrid of both carbon fibre (CF) and ACP/nano ZnO. The performance of mono fillers were investigated by fabricating the cementitious composites with different content of ACP (0.5%, 1%, 2% and 4% by weight of binder) and nano ZnO (0.05%, 0.1%, 0.3% and 0.5% by weight of binder). Moreover, the hybrid effect was studied by incorporating CF at 0.7 wt% with the additional ACP/nano ZnO at various concentration. The result showed that ACP/nano ZnO could improve the mechanical properties of cementitious composites. In terms of piezoresistivity behaviour, composites containing 2 wt% of ACP have favourable performance parameters with a sensitivity of 3.571%/MPa and linearity of 7.849%. Composites containing 4 wt% of ACP can achieve repeatability at 0.952%, which indicate a good reproducibility of the piezoresistivity. Although the developed cementitious composites cannot achieve a sensitivity as high as carbon fibre reinforced cementitious composites (CFRCCs), the linearity of the piezoresistive response of the composites containing hybrid ACP/CF and nano ZnO/CF has improved compared to CFRCCs.

Prefabricated Concrete Elements for the facade Industry with Nano cement composites containing silica fume, nano-silica and TiO2

Using mineral admixtures in cement composites as a way to improve their mechanical and durability properties is a common practice in concrete technology. Among them silica fume and nano-silica effectively influence the composite's early and long-term properties. Due to the limited particle size distribution of nano and micro silica it is expected that the incorporation of some mineral additives with a size of greater than 500 nm may result in better mechanical and durability performance because of the filler effect. In this study, the effect of different percentages of TiO2 on mechanical properties of cement composites containing nano-silica and silica fume was investigated. Six designs were tested for compressive strength with respect to zero, 2.5 and 5 percent replacement of cement with TiO2. The addition of TiO2 has led to an increase in compressive strength. The best results from the sample with 2.5% TiO2 are obtained. This could be due to the effect of TiO2 particles filling. Comparison of SF3, SF2 and SF1 at 28 days of age showed that SF2 increased the compressive strength. This shows that TiO2 has a great potential for improving the mechanical properties of composite cement.The results showed that the addition of TiO2 had a positive effect on compressive strength.

Evolution of elastic and thermal properties of cementitious composites containing micro-size lightweight fillers after exposure to elevated temperature

This paper studies the evolution of elastic and thermal properties of cementitious composites containing micro-size lightweight fillers after exposure to elevated temperatures (up to 800 °C). A multiscale investigation is carried out to study the thermal degradation of cementitious composite materials at multiple scale levels: at cement past level, the dehydration kinetics of cement hydrates (i.e., C–S–H, CH and aluminate hydrates) and development of microcracks are studied as functions of exposure temperatures. The damage mechanism of the inclusion phases and damages within the interfacial transition zone (ITZ) under elevated temperature are also investigated. In addition, the change of mechanical (i.e., elastic moduli, compressive strengths) and thermal (thermal conductivities) properties are measured as functions of the exposure temperature. Based on the experimental studies, a multiscale thermal degradation model is developed where the thermal degradations of cement paste (including water composition, porosity, and solid phase changes), inclusion phases, and the interfaces are captured through a multiscale sub-stepping homogenization scheme. The thermal degradation model is validated through multiple sets of experimental data. Finally, the influence of key parameters including the particle size distribution of the inclusions, the chemical composition, as well as the effects of ITZ damage are studied.

Enhanced transport properties of graphene oxide based cement composite material

This study is aimed to evaluate the transport properties of a cement composite incorporated with graphene oxide (GO). GO is a 2-dimensional nano material, enriched with reactive oxygen functional groups which made it as a suitable reactive material with cementitious materials. The GO-cement composite was prepared by adding GO in four different proportions such as 0.01%, 0.02%, 0.03%, and 0.04% by weight of cement. In the durability aspect water absorption, water sorptivity, resistance to acid attack, mechanical properties, thermal analysis, chloride migration coefficient, and chloride penetration depth were examined experimentally for GO-cement composite specimens and compared with plane cement composite specimens. Experimental results indicated that 14.5%, 30%, and 40.47% degradation in water absorption capacity, chloride migration coefficient, and chloride penetration depth of cement composite specimens with 0.03% addition of graphene oxide than normal cement composite specimens at 28 days of curing. Additionally, significant decrement in the sorptivity coefficient of cement composite was also achieved at 0.03% of GO addition. Mechanical properties were enhanced by 77.70% in flexural strength at 0.03% of GO addition and 47.61% in compressive strength at 0.04% of GO addition in cement composite at 28 days of curing. SEM analysis of the test samples exhibited the pore filled structure of the cement composites with GO addition. In addition, all GO-cement composite specimens exhibited greater resistance to an acidic environment and negligible loss in strength and weight was observed than normal cement composite specimens at 28 days immersion in 2% and 5% concentrations of both H2SO4 and HCl acidic solutions. Thermal resistance was increased in the terms of compressive strength in all GO-cement composite mixes gradually by increasing the concentration of GO content from 0.01% to 0.04% by weight of cement. It can be concluded that an effective improvement in transport properties of cement composite was achieved by the incorporation of graphene oxide nano material.

Constitutive modelling and mechanical properties of cementitious composites incorporating recycled vinyl banner plastics

This paper describes an experimental study, which has been lacking to date, into the mechanical properties of cementitious composites incorporating granules and fibres from recycled Reinforced PVC (RPVC) banners. A detailed account of over 140 tests on cylindrical, cubic and prismatic samples tested in compression and flexure, with up to 20% replacement of mineral aggregates, is given. Based on the test results, the uniaxial properties of selected recycled materials are examined in conjunction with a detailed characterisation of the RPVC granule size and geometry. Experimental measurements using digital image correlation techniques enable a detailed interpretation of the full constitutive response in terms of compression stress-strain behaviour and flexural stress-crack opening curves, as well as key mechanical parameters such as strength, elastic modulus and fracture energy. It is shown that the mechanical properties decrease proportionally with the amount of RPVC. For each 10% increment of volumetric replacement of mineral aggregates, the compressive strength is halved whilst the flexural strength is reduced by about 30% compared to their conventional counterparts. The reduction in strength is counterbalanced by an improved ductility represented by a favourable post-peak response in compression and an enhanced flexural softening and post-cracking performance. Smaller particles, with a relatively long acicular or triangular geometry, exhibited better behaviour as these acted as fibres with improved bond properties in comparison with intermediate and large size granules. The test results and observations enable the definition of a series of expressions to determine the mechanical properties of cementitious materials incorporating RPVC and other waste plastics. These expressions are then used as a basis for an analytical model for assessing the compressive and tensile stress-strain response of such materials. Validations carried out against the tests undertaken in this study, as well as from previous investigations, indicate that the proposed expressions and the developed constitutive model offer reliable representations for practical application.

Effect of hybrid basalt fibre length and content on properties of cementitious composites

Nowadays, basalt fibre is gaining popularity in the field of construction materials due to its low production cost and enhanced mechanical properties. However, research is still needed into the use of a single type of fibre with different lengths in composite materials. Therefore, in this paper the hybridisation of basalt fibre of various lengths and contents is studied in order to take full advantage of multi-scale characteristic(s) with a single type of fibre, while the fundamental mechanical properties of single-length basalt-fibre-reinforced cementitious composites and hybridisation of different-length basalt-fibre-reinforced composites are investigated. Additionally, a hybrid fibre coefficient is developed to evaluate the effect of hybrid fibre in cementitious materials. A total of 17 mix proportions were made containing either a single length or a combination of four different lengths of basalt fibre (3, 6, 12 and 20 mm) with various total volume contents. The paper shows that the hybridisation of four different lengths of fibres in cementitious composites generally improved mechanical properties in comparison to plain and single-length fibre-reinforced mortar. The hybrid fibre coefficient also showed good consistency with the results of mechanical properties. Scanning electron microscopy demonstrated the proper bonding of basalt fibre with cementitious composites.

Strength and microstructural analysis of nano-silica based cement composites in presence of silica fume

Replacement of cement with pozzolanic materials has addressed numerous inquiries identified with impact of these materials on the microstructural and other properties of cement composites. On the other hand, because of the absence of technique and pertinent supporting information, an appraisal of general execution of such admixtures is hard to be completed. The utilization of pozzolanic materials as cement substitution in mortar has enhanced the execution of their physico-chemical and mechanical properties. In this study, the composition of silica fume (SF) was differed as 3%, 6%, 9% and 12% at a fixed composition of nano-silica (NS) as 0.5% by weight for substitution of cement. The fresh and hardened properties of cement mortars were analyzed and microstructural analysis was performed. The specimens were found to exhibit better developed microstructure and enhanced compressive strength with inclusion of optimized dosage of SF in presence of NS. The study has confirmed that the simultaneous replacement of cement with the optimized dosage of pozzolanic materials brings improvement in the properties of the cement mortar and can be used to partially substitute cement for the beneficiary effects.

Effects of Moisture on Mechanical and Piezoresistive Properties of Cement Composites containing Carbon Fiber during long age

This paper presents a compressive test program designed to determine the mechanical and self-sensing properties of cement-matrix composites containing carbon fiber. Two kinds of mixes with 0.5% and 0.75% carbon fiber （CF） were prepared. The mechanical and piezoresistive properties of the cement-matrix composites were evaluated at 28, 90, 180, 270, and 360 d. The results show that the mechanical properties were enhanced in most cases. However, the compressive strength of carbon fiber reinforced cement-matrix composites decreased compared with the reference mix at the early curing ages, which agrees with the results mentioned in the literature. What is worth to mention, the 360 d compressive strength of carbon fiber reinforced cement-matrix composites reached the same level as that of the reference. Moreover, both negative and positive piezoresistivity were observed during the experiments. The amplitude of piezoresistivity was found to change with the variation of moisture content, and was not directly proportional to the magnitude of the stress. In the elastic stage with smaller stress amplitude, the piezoresistivity amplitude was larger. When the stress amplitude was multiplied, the piezoresistivity change was not synchronous. The gauge factor for the composite with 0.75% CF was higher than that of the composite with 0.5% CF and commercially available strain gauges.

Investigation of Mechanical and Electromagnetic Properties of Cement Composites with High-Volume Fly Ash and Reinforced with Basalt Fibers

Investigation of Mechanical and Electromagnetic Properties of Cement Composites with High-Volume Fly Ash and Reinforced with Basalt Fibers

Effect of graphene oxide on strength properties of cementitious materials: A review

Reinforcing nanomaterials (0D nanoparticles, 1D nanofibre, 2D nanosheets) in cementitious matrix presents an opportunity to enhance cementitious composites at nanoscale. Reinforcing graphene based nanomaterials in cementitious matrix, enhancement of mechanical and durability properties has been observed at 0.02%, 0.04%, 0.06%, of Graphene Oxide in past research. This paper reviews a comprehensive overview of graphene based nanomaterials (mostly graphene oxide based nanomaterials) at dosages of 0.0%, 0.02%, 0.04%, 0.06%, 0.08% of Graphene Oxide in imparting and altering the properties of cement composites and concrete composites and also points future scope in construction field.