Cement Mortar Composites Research Articles

Evaluation of carbon nanotube (CNT) cement-based traffic sensor incorporating steel slag based on Accelerated Pavement Test (APT)

ABSTRACT In this study, a carbon nanotube (CNT) cement composite containing CNT and steel slag was developed and its application in traffic information sensing was studied. The mix ratio of steel slag cement mortar matrix and CNT cement composite was determined by mechanical properties and electrical conductivity tests. Then the CNT cement composite intelligent sensing device was prepared and an Accelerated Pavement Test equipment was used to test its piezoresistive response curve. The test results show that steel slag and CNT enhance mechanical properties and electrical conductivity. The vehicle speed and wheelbase were calculated based on the piezoresistive response results, and the calculation errors of the wheel speed (0.375 and 0.844 km/h) were less than 10% and 20%, respectively. The wheelbase estimate has a maximum error of approximately 12% and 15% for wheel speeds of 0.375 and 0.844 km/h, respectively. Therefore, the CNT cement composite containing steel slag developed in this study has the potential to serve as a traffic sensor.

Dispersion effect of nano-structure pyrolytic carbon on mechanical, electrical, and microstructural characteristics of cement mortar composite

ABSTRACT In material science, converting waste into nanomaterials by green technologies highlights the interest in producing sustainable carbon nanomaterial (SCN). This study first-ever utilized tyre-char as a Nano-Structure Pyrolytic Carbon (NSPC) to develop electrically conductive composites. Unlike other carbon nanomaterials, the efficiency of NSPC particle as an SCN in developing electrically conductive composites was investigated in terms of dispersion, mechanical, water absorption, electrical resistivity, and microstructure. The results of sedimentation and zeta potential (−19 mV) showed the excellent dispersion of NSPC particle in water with the combined effect of superplasticizer and ultrasonication. The compressive (40.37%) and flexural strength (10.76%) than that of plain cement mortar composite (CMC) is achieved with 2 wt.% and 1.5 wt.% of NSPC particle, respectively. The water absorption rate and volume of permeable voids were reduced, exhibiting less agglomerations. The percolation zone of AC and DC resistivity of NSPC composite ranges between 1 and 2 wt.%, and the established percolation threshold is at 2 wt.%. XRD analysis showed C-S-H formation consistently increased with curing age, and HR-SEM with EDAX analysis exhibits the dense microstructure and well-distributed NSPC particle at the nanoscale. These experimental outcomes significantly enhanced the reliability and provided a framework for tailoring NSPC particle as SCN for developing electrically conductive composite.

Enhancement of the tensile properties of cement mortar composites with nanoadditives produced by chemical vapor deposition

While graphene effectively enhances the performance of cement-based materials, its current production methods are characterized by environmental unfriendliness and high energy consumption. To investigate a large-scale and eco-friendly graphene preparation approach, Carbon Nano Sheets (CNS) were synthesized via chemical vapor deposition (CVD). The influence of CNS content on the tensile strength of cement mortar was assessed through the Brazilian splitting test. Concurrently, the mechanism of CNS was examined using acoustic emission monitoring and scanning electron microscope. The experimental results revealed that methane can be effectively decomposed into high-quality CNS at 1080 ℃ when using fly ash, silica fume, and sand as substrates. The Brazilian splitting test revealed that CNS effectively enhances the tensile strength of cement mortar, with improvements ranging from 9 % to 58.7 %. Acoustic emission results indicated that the inclusion of CNS reduces the occurrence of micro-fractures during the failure of cement mortar specimens. Furthermore, nano-mechanical testing and microstructural characterization demonstrate that CNS can reduce micro-cracks and pores in the interface transition zone and hydration products, playing a role in dense hydration products. Furthermore, it can decrease the width of the interface transition zone and enhance the micro-mechanical properties of cement pastes. This study offers a novel approach for the eco-friendly production of cement nano additives.

Cement mortar composites including 1-tetradecanol@PMMA Pickering emulsion particles for thermal energy management of buildings

In this study, a poly(methyl methacrylate) (PMMA) shell 1-tetradecanol core microencapsulated phase change material (MPCM) was produced using the Pickering emulsion technique. Characterization tests of the produced MPCMs were performed using Fourier transform infrared (FT-IR) spectroscopy, particle size distribution (PSD) analysis, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) techniques. The latent heat, melting temperature and encapsulation rate of MPCM were determined and they were found as 108.4 J/g, 33 °C, and 46.7 % for heating period, respectively. The effect of 1-tetradecanol@PMMA MPCM on the physical, mechanical, and thermal performance properties of cementitious mortars was also investigated in the study. For this reasons 1-tetradecanol@PMMA MPCMs are included in mortar mixes at 5 %, 7.5 %, and 10 % by weight of cement. As the MPCM ratio increased, the water absorption rate and porosity increased, while the workability, unit weight of the mortar, ultrasonic pulse velocity, flexural strength and compressive strength parameters decreased. The compressive strength of the mortar containing 10 % MPCM on the 28th day was measured as 34.74 MPa. The highest thermal storage capacity was found in mortars containing 10 % MPCM. When the thermal performance of the reference and 10 % MPCM-containing mortars were compared, the indoor temperature differences at the end of the heating and cooling periods were measured as 4.7 °C and 3.9 °C, respectively. The results showed that MPCM produced by the Pickering emulsion technique has the potential to increase thermal comfort in buildings, reduce fuel consumption used for heating purposes and, accordingly, reduce carbon emissions.

Optimised repairment properties of waterborne epoxy resin–cement composite material: An experimental and simulation study

The demand for high-performance repair materials has significantly increased owing to continuous infrastructure construction. However, current research on epoxy resin–cement mortar composites lacks a theoretical investigation of the proportion of epoxy resin and hardener necessary to prepare a composite material with optimal performance. Composite material preparation often relies on the results of empirical studies. To address this issue, this study used E44 (waterborne epoxy resin, WER) and D230 (hardener) as raw materials to theoretically determine the optimal ratio for preparing a composite material. The optimal ratio and content were validated considering various test parameters, such as workability, mechanical properties, self-developed shear bond strength, and impermeability performance. The results indicated that the epoxy resin-to-hardener ratio of the composite material should be 4:1, with a 30% content. In addition, the microstructure of the composite material was analysed using various test methods, including scanning electron microscopy (SEM), SEM–energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and mercury intrusion porosimetry (MIP), to investigate its influence on the interfacial transition zone (ITZ), composition, and pore structure. Furthermore, molecular dynamics simulations were performed to analyse the mechanical properties, adsorption energy, mean square displacement (MSD), and radius dispersion function (RDF) of the calcium silicate hydrate (C-S-H) and epoxy resin molecule (cross-linked structure) composite, explaining the effect of water molecules on the composite material from an atomic-scale perspective. By combining experimentation and simulation, this study proposes a computational ratio design method that could provide new insights into the research and development of WER–cement composites while creating a simple shear bond strength test method for repair materials.

Electromechanical properties of multi-reinforced self-sensing cement-based mortar with MWCNTs, CFs, and PPs

This experimental research examines the electromechanical properties of hybrid cement-mortar composites strengthened with different amounts of multi-walled carbon nanotubes (MWCNTs), carbon fibers (CFs), and polypropylene microfibers (PPs). The experimental program included optimal mechanical improvement at the nano and micro levels. The optimum micro-composite mortar derives from the finest mechanical response of the CFs and PPs micro-modified specimens in terms of flexural and compressive strength. Further, the electrical response of the mortars with the improved mechanical response was examined. The improved mechanical and electromechanical response of the optimum amounts of the two scales indicates the hybrid mortar with exceptional performance. This optimum amount in micro-scale in synergy with the optimum amount of MWCNTs constituted the hybrid-reinforced cement-based mortar. The optimized nano-, micro-, and hybrid-reinforced mortars were examined for their electrical properties in terms of electrical conductivity, impedance, and piezo-resistivity. These measurements in combination with the Nyquist plots of the resistance-reactance specified the sensing ability of the cementitious self-sensor. Results indicated that the optimum reinforcement in the nanoscale is 0.2 wt% MWCNT and in microscale 0.5% wt.% CFs exhibited improvement in flexural strength, compressive strength, and flexural toughness. The optimum nano- and micro-reinforced cement-based mortars presented much higher conductivity of about 867% and 633%, and lower impedance of about 89.4% and 86%, respectively, compared to the reference specimen, and a one-order-of-magnitude compared to the other contents. The excellence of the hybrid combination of 0.2 wt% MWCNΤs and 0.5% wt.% CFs occur with even more improved flexural strength of about 27%, flexural toughness of about 1607%, conductivity of 2617% more than the reference mortar, and lower impedance of about 96%, compared to the reference specimen. The piezoresistive response of the tested cement-mortar composites denotes the enhanced strain-sensing ability of the examined multi-reinforced mortars, highlighting the superiority of the hybrid one.

Production of Agro-waste cement Composites: Influence of nutshells on mechanical and hardened properties

Different countries have been encountering significant obstacles in the disposal of agro-wastes in landfills, with a recent increase in landfill sites receiving inadequate or no treatment. Moreover, in addition to high disposal costs, several factors related to landfills pose a significant threat to human health and ecosystems – examples include leachates, toxins, and greenhouse gases, which constitute environmental problems. Nutshells are an example of agro-waste materials that can be utilized in different industrial and engineering applications to help save the environment. This study aims to evaluate and investigate the utilization of nutshells (from pistachios, walnuts, and hazelnuts) as a replacement material to produce an agro-waste cement composite. Different nutshell contents (0.5, 1, 1.5, 2, and 2.5% by weight of cement) were used in the preparation of the cement composite mixtures. The nutshells were characterized by X-ray diffraction and energy-dispersive X-ray spectroscopy, and scanning electron microscopy (SEM) was also implemented to observe the prepared cement mortar composites. The compressive strength, hardness, thermal conductivity, and water absorption of cementitious composites were investigated, highlighting that the addition of nutshells significantly enhances the compressive strength. Agro-waste cement composite specimens with a nutshell content of 2.5% exhibited the highest compressive strength. Other properties of the cement composites, such as the thermal insulation properties, were also enhanced by the inclusion of nutshells. For instance, thermal conductivity of all mortar composite samples reduced by 57, 48, and 45% for the addition of 2.5% walnut, pistachio, and hazelnut shells, respectively. This eco-friendly material represents a potential way to address the generation of waste products from agricultural activities and nature; suggested uses of such composites include their application in lightweight panels, thermal insulators, and sustainable building blocks, among several other materials.

Evaluation of rheological and mechanical properties of bottom ash based masonry mortar with graphene oxide

This paper evaluates the rheological and mechanical properties of lignite based bottom ash as fine aggregate in cement mortar with GO as an additive. The annual extraction of such a huge amount of bottom ash needs a massive transfer to the field, as it constitutes a threat to the environment. The utilization of such residue as a partial replacement of fine aggregate in masonry mortar is not fully explored. Hence, an attempt has been made to utilize the bottom ash as FA in cement mortar composites, and studied the influence of graphene oxide (GO) in the properties of mortar matrix. In this study, bottom ash replacement from 0 to 60% and GO at dosage of 0.1, 0.15 and 0.20% by weight of cement were used. Compressive and flexural strengths of composites were improved significantly at GO = 0.15%. Mechanical properties at 40% bottom ash replacement level only have shown minor improvement. It was observed from the flow table test that addition of bottom ash leads to reduction in workability of masonry mortar, and GO enhanced both the rheological and mechanical properties of mortar matrix.

Effect of multiwalled carbon nanotube size on electrical properties of cement mortar composites

Cement mortars (CM) containing different contents and sizes of multiwalled carbon nanotubes (MWCNTs) were prepared using surfactants in combination with ultrasonic dispersion. The effects of the content, diameter and length of MWCNTs on the electrical conductivity of cement mortar and the self-inductive piezoresistive rate under single and cyclic loading were studied using the four-electrode method. The results show that the conductive percolation thresholds of CMs containing MWCNTs with different length–diameter ratios occur at an approximate MWCNT content of 0.1 wt%. The electrical conductivity of cement mortars with MWCNT diameters of 10–20 nm was the largest for a content of 0.1 wt%, and the values were 112% and 128.3% of the conductivity of the MWCNTs/CM with diameters of 20–40 nm and 40–60 nm, respectively. In addition, the fractional change in resistivity of the cement mortar specimens varied most significantly at a content of 0.75 wt% of MWCNTs; the fractional change in resistivity reached 14.27%. Adding small-diameter MWCNTs to cement mortar can maximise the sensitivity of electrical resistance of cement mortar to compressive stress.

Effect of polypropylene fibre on cementitious mortar early shrinkage cracking using the eccentric-ring test

The effects of polypropylene fibres on mortar and cement-paste cracking were investigated using different amounts of fibre fractions and eccentric rings under restrained-shrinkage conditions. Eccentric-ring tests were conducted to investigate early-age shrinkage cracks. The characteristics of restricted cementitious materials were described by evaluating the cracking time and using concrete mixtures that are less likely to crack. Different fibre-volume fractions significantly enhanced the width, area, and age of cracking. Increasing the water-cement ratio and sand percentage increased the cracking age. The eccentric-ring test showed a greater susceptibility to cracking in cement-mortar composites. The mechanical strength was assessed, and the impact of polypropylene fibres was investigated.

Corrigendum: Thermal performance experiment and numerical simulation of micro-PCM cement mortar composite wall

Simeon Oka, Editor-in-Chief Emeritus of the journal Thermal Science request that it is, due to request of the authors, necessary to correct affiliations of the author THERMAL PERFORMANCE EXPERIMENT AND NUMERICAL SIMULATION OF MICRO-PCM CEMENT MORTAR COMPOSITE WALL by Mei Liang* School of Civil Engineering, Zhengzhou University of Industrial Technology, Zhengzhou, China Original scientific paper https://doi.org/10.2298/TSCI2304013L published in the journal Thermal Science, Year 2023, Vol. 27, No. 4A, pp. 3013-3028 since by the request of the author, AFFILIATION of the author must be changed. Instead of: School of Civil Engineering, Zhengzhou University of Industrial Technology, Zhengzhou, China has to be written: School of Economics and Management, Hebi Institute of Engineering and Technology, Henan Polytechnic University, Hebi, China <br><br><font color="red"><b> Link to the corrected article <u><a href="http://dx.doi.org/10.2298/TSCI2304013L">10.2298/TSCI2304013L</a></b></u>

Strength, Durability and Permeability Studies on Cement Concrete with and without Nano-Silica

The application of nanomaterials in cement/concrete has resulted in the development of smart materials which are durable, sustainable and high performance oriented apart from being eco-friendly. Several types of nanomaterials are being used by researchers all over the world to improve the properties of cementitious system, amongst them silica nanoparticles (SNPs) have been credited with high pozzolanic reactivity and pore filling effects. It is also very well known that permeability is the major factor for deteriorations of concrete structures in the long term thus affecting its durability. A thorough study was performed on cement mortar composites and standard grade concrete with the additions of colloidal silica nanoparticles(SNPs) in various dosages starting from 0.5%,0.75%,1.0%,1.25% and 1.5% by weight of cement(b.w.c.) to understand the impact from micro-structure improvement to macro-level property enhancement. The results show that in presence of colloidal SNPs (Indian branded) having 35-40% active nano content with 5-40nm particle size the strength increase at 28 days is 32% increasing to 59% at 90 days. An influence on durability is also observed with strength increasing from 4% to 8% with the addition of more SNPs from 0.75% to 1.0% b.w.c. The microstructural investigations reveal that silica nanoparticles refines the pore structure due to accelerated hydrated mechanisms leading to the creation of more hydration products and thus to a more denser microstructure. A M-40 grade standard concrete was prepared as per IS:10262 with the addition of optimized SNPs as found for cement mortar composites strength results at 28 days maximum strength keeping the water-cement(w/c) ratio fixed at 0.4. Tests were conducted on concrete to find out the compressive strength and permeability of concrete. The compressive strength of concrete containing nano materials were found to be 24% more than that of normal cement concrete (NCC) of M-40 grade. The permeability values were found to be decreased by 57% with the addition of nano silica particles to concrete.

Drying Process of Cement Mortar Composites Reinforced with Cellulosic Fibres: Experiment and Mathematical Modelling

Drying Process of Cement Mortar Composites Reinforced with Cellulosic Fibres: Experiment and Mathematical Modelling

Effects of graphene oxygen content on durability and microstructure of cement mortar composites

• The effect of rGO oxygen concentration on the durability of cement mortar is studied. • Both GO and rGO are beneficial to promote the hydration rate of C 3 A, C 3 S. • Moderately reduced rGO is more beneficial to increase CSH and CH contents in composites compared to GO. • Moderately reduced rGO/cement-mortar composites exhibit high erosion resistance. • The mechanism of rGO enhancing the corrosion resistance had been summarized. Graphene materials have been extensively explored and successfully used to improve the properties of cement-based composites. However, current studies mainly focus on optimizing additional amounts and dispersion modes of graphene. The influence of other parameters, such as graphene crystallinity, size, and oxygen-containing functional group level, on the performance of cement mortar composite is not fully understood. Therefore, in this study, a series of reduced graphene oxides (rGO) with different oxygen concentrations were synthesized by controlling two parameters, namely, different concentrations of l -Vitamin C (10, 20, 50, and 70 wt%) and different reduction times (15, 30, 45, and 60 min), and added to the cement-mortar composite at the same dosage. The effect of rGO with different oxygen concentrations on the durability and microstructure of the composites was investigated. The durability results revealed that rGO with mild oxygen group level (i.e., prepared by 50 % l -Vitamin C reduction for 30 min) can remarkably enhance the durability of cement mortar composite material. Adding 0.1 wt% rGO with mild oxygen concentration to the cement mortar caused the initial water absorption and secondary water absorption to decrease by 44.75 % and 31.95 %, respectively, compared with ordinary cement mortar. This enables rGO/cement-mortar composites to have outstanding resistance in harsh erosive environments (i.e., high concentrations of CO 2 ) because rGO promotes the cement hydration reaction and generates more hydration products. Meanwhile, the mild oxygen acid groups on the surface of the rGO act as a neutralizer in a strong alkaline medium, resulting in the formation of calcium carbonate precipitation, which further improves the compactness of the matrix.

Effects of graphene nanoplatelets type on self-sensing properties of cement mortar composites

Graphene nanoplatelets (GNPs) that possess high electrical conductivity and relatively low cost have been considered to obtain self-sensing capability in cementitious composites. However, there is limited understanding on the effects of physical properties of GNPs such as particle size and surface area on the self-sensing characteristics of the cement composites. In this study, nine types of GNPs that have different surface areas, particle sizes, and thicknesses are considered in the development of self-sensing mortar composites. For each type of GNPs, specimens with GNP concentrations of 2.5%, 5%, and 7.5% by weight of cement were prepared. The bulk electrical resistivity of the developed mortar composites was measured at different curing ages. The compressive strength of the specimens was also evaluated. The piezoresistive behaviors of the GNP-reinforced mortar composites were studied through cyclic compressive loading tests at different load levels. During piezoresistivity tests, the measurements were conducted through both direct current (DC) and alternating current (AC) and the results obtained from each method were evaluated. Results reveal that GNPs with very small particle sizes and large surface areas cannot disperse effectively in the cement matrix and do not provide piezoresistive characteristics. For GNPs with relatively smaller surface areas, the GNPs with higher particle sizes form effective conductive paths and exhibit better piezoresistive characteristics.

Effect of adding depolymerized polyethylene terephthalate waste on the acoustic insulation and hardness properties of Iraqi cement mortar

depolymerized Polyethylene terephthalate waste (DPET) particles were prepared by bubble column reactor adding ethylene glycol as a solvent and Nano MgO as a catalyst and using DPET particles to modify the mortar by partial replacement of sand. The mechanical hardness test, the physical ultrasonic pulse velocity test and the acoustic insulation test of the modified cement mortar composite have been studied. DPET particles were used with four percentages of (1, 3, 6 and, 9)%wt of sand for each one of them. All tests were done for 28 days of curing. The cement mortar composite was prepared using water/cement ratio of (0.48) while sand-to-cement material ratio of (1:2.75) (2.75 parts of sand and 1 part of cement). The findings showed that there was no clear influence of DPET on the hardness of the cement mortar, where the hardness of mixture with 3% DPET equal to that of mixture with no DPET was (91.7 shore A), while the hardness of other mixtures with (1, 6 and 9)% PET were (91.6, 91.2 and 90.8 shore A) respectively. While the UPV of the modified cement mortar decrease with increase the amount of DPET particles, where the drops in UPV were (-2.98%) at 9% of DPET particles. The acoustic insulation of the modified cement mortar composite increase as the DPET increases in all frequencies that were used. This is indicate that DPET particles which that made through depolymerized the PET of waste water bottles can enhancement the physical and insulating properties of the mortar.

Water absorption kinetics of bitumen modified cement mortars

Concrete permeability is a major factor that affects durability and reliability of structures – bridges, tunnels, culvert pipes, etc. It is important to identify effective methods of protection of such structures against water penetration, for example by using a modifying substance. Samples of cement mortar composites were used for water absorption simulation. Bitumen emulsion was used as a modifying agent. According to the water absorption kinetics, the following parameters of the pore microstructure of the mortar composite were estimated: the index of mean size of open capillary pores, closed porosity, and the index of size uniformity. The research has shown that the addition of bitumen emulsion decreases the pore space and macrocapillaries (from 23.91% to 6.61%), water absorption (3 times), and the index of mean size of open capillary pores (from 0.69 to 0.3) of modified mortars.

Three-phases bubble column to polyethylene terephthalate depolymerization for cement mortar composites improvement

This paper aims to prepare depolymerized polyethylene terephthalate (DPET) powder from recycled plastic water bottles. Adding this DPET powder to the cement mortar was also studied. The adopted PET depolymerization process includes the usage of both ethylene glycol (EG) as solvent and nano-MgO as a catalyst. A bubble column reactor was designed for this process. Five different mortar groups were made; each has different DPET content of 0%, 1%, 3%, 6% and 9% as a sand replacement. The flexural strength test and the water absorption measurement are done after two curing periods: 7 and 28 days. The research finding demonstrated that the flexural strength of mortar was reduced by increasing the DPET powder percentage and the maximum dropping was 15% when 9% of DPET was added. The ability of the mortar to absorb the water was reduced by 14.5% when DPET powder was 9%. The mortar microstructure is featured with fewer cavities and porosity. This work’s employed bubble column technique is limited only to the laboratory environment and needs to be scaled up within industrial mass production. For future research, it is suggested to decrease depolymerization time by using smaller pieces of plastic water bottle waste and trying other types of nanocatalyst. The modified mortar can be utilized in areas where moisture, rainfalls, and sanitation systems exist. The article claims that depolymerized waste PET improves chemical process efficiency by lowering reaction time and improving mass and heat transfer rates. Besides, this approach saves money. It is found out that the depolymerized plastic waste is much more functional due to its high cohesion capability than being used as small PET pieces.

Chemical Depolymerization of Waste PET Bottles in Bubble Column Reactor for Sustainable and Thermal Installation of Cement Mortar Composites

Chemical Depolymerization of Waste PET Bottles in Bubble Column Reactor for Sustainable and Thermal Installation of Cement Mortar Composites

Properties of 3D-Printed Polymer Fiber-Reinforced Mortars: A Review.

The engineering applications and related research of fiber-reinforced cement and geopolymer mortar composites are becoming more and more extensive. These reinforced fibers include not only traditional steel fibers and carbon fibers, but also synthetic polymer fibers and natural polymer fibers. Polymer fiber has good mechanical properties, good bonding performance with cement and geopolymer mortars, and excellent performance of cracking resistance and reinforcement. In this paper, representative organic synthetic polymer fibers, such as polypropylene, polyethylene and polyvinyl alcohol, are selected to explore their effects on the flow properties, thixotropic properties and printing time interval of fresh 3D-printed cement and geopolymer mortars. At the same time, the influence of mechanical properties, such as the compressive strength, flexural strength and interlaminar bonding strength of 3D-printed cement and geopolymer mortars after hardening, is also analyzed. Finally, the effect of polymer fiber on the anisotropy of 3D-printed mortars is summarized briefly. The existing problems of 3D-printed cement and polymer mortars are summarized, and the development trend of polymer fiber reinforced 3D-printed mortars is prospected.