Polymer-modified Cement Mortar Research Articles

Study on the Mechanical Properties of Polyurethane-Cement Mortar Containing Nanosilica: RSM and Machine Learning Approach

Polymer-modified cement mortar has been increasingly used as a runway/road pavement repair material due to its improved bending strength, bonding strength, and wear resistance. The flexural strength of polyurethane–cement mortar (PUCM) is critical in achieving a desirable maintenance effect. This study aims to evaluate and optimize the flexural strength of PUCM involving nano silica (NS) using a central composite design/response surface methodology (CCD/RSM) to design and establish statistical models. The PU binder and NS were utilized as input parameters to evaluate the responses, such as compressive and flexural strength. Moreover, machine learning (ML) algorithms including artificial neural networks (ANN) and Gaussian regression process (GPR) were used. The PUCM mixtures were prepared by adding a PU binder at 0%, 10%, 15%, and 25% by weight of cement. At the same time, NS was incorporated into the mortar mixes at 0 to 3% (interval of 1%) by cement weight. The results showed that the simultaneous effect of PU binder at the optimal content and NS improved the performance of PUCM. Adding NS to the mortar mixture mitigated some of the strength lost due to the PU binder, which remarkably reduces the strength properties at a high content. The optimized PUCM can be obtained by partly adding 3.5% PU binder and 2.93% NS particles by the weight of cement. The performance of the machine learning algorithms was tested using performance indicators such as the determination of coefficient (R2), mean absolute error (MAE), mean-square error (MSE), and root-mean-square error (RMSE). The GPR algorithm outperformed the ANN with higher R2 and lower MAE values in the training and testing phases. The GPR can predict flexural strength with 90% accuracy, while ANN can predict it with 75% accuracy.

Some Properties of Cement Mortar Modified by Styrene Butadiene Rubber

This research studies the effect of adding five different percentages of polymer (2, 4, 6, 8, and 10% of cement weight) on cement mortar's fresh and hardened properties, which was cured at laboratory temperature for 7, 14, and 28 days. Workability increases with increasing polymer. The workability value was lowest (25.6 and 29.4) % in mixtures containing 2% and 4% of (SBR). Increasing polymer ratios significantly decreased mechanical properties (compressive and flexural strength). Therefore, the best results were at 2% SBR and 4% SBR at 28 days of age. An inverse relationship was recorded between the increase in SBR ratios and polymer-modified cement mortar's compressive and flexural strength values. In general, the highest improvement in the water absorption and dry density resulted in better results with a decrease in the proportion of the polymer for all specimens of cement mortar containing 4% SBR polymer relative to the reference mixture.

Performance evaluation of super absorbent polymer modified cement mortar with nano-silica/GGBS

Modified cement mortar plays a major role in enhancing the properties of conventional cement mortar such as strength, durability, better adhesion, reduce porosity and shrinkage and improve workability. Certain modifiers, like industrial by-products, can be incorporated into mortars to promote sustainability and reduce environmental impact. The main aim of this study is to develop Super Absorbent Polymer Modified cement mortars with Nano Silica/GGBS. In this study, conventional cement mortar blended with Nano Silica and Super Absorbent Polymer (SAP) as one combination then GGBS and SAP blended mortar as another combination was examined to mitigate the negative impact of SAP. Ternary Blended cement mortars prepared with various SAP dosages of 0.25% of cement and 0.5% of cement. Nano-Silica is an additive used in the range of 1%, 1.5%, and 2% of the weight of cement. A combination containing GGBS and SAP, GGBS is a replacement for cement in the range of 15%, 30%, and 45% to the weight of cement. The combined effect of altering SAP and Nano-silica/GGBS composition on the mechanical, durability, and microstructural properties were studied using experimental investigation. Peak improvement in the compressive strength of the control mix of 6.52% is noted in the mix combination that contains 0.25% SAP and 15% GGBS replacement. The durability test revealed that the weight loss minimized by 19.58% and strength loss minimized by 36.17% due to acid attack is noted in the combination of GGBS and SAP. Weight loss minimized by 36.17% and strength loss minimized by 22.71% due to sulphate attack is noted in a mix containing GGBS. From experimental investigation, 30% & 45% GGBS replacement in place of cement had no significant improvement in mechanical, durability, and microstructural properties compared to 15% GGBS replacement, which optimum obtained in this study to alleviate the negative consequence of SAP when used as an internal curing agent.

Frost Resistance of Redispersible Polymer Powder–Modified Fast-Hardening Cement Mortars under Simulated Climatic Conditions

Polymer-modified fast-hardening cement mortar is widely used as road repair material due to its excellent performance attributes of shorter setting time and good workability as well as high adhesive strength. However, in the complex actual service environment, whether it can still maintain stable performance has become a concern. Therefore, this study performed an indoor freeze–thaw cycle test to investigate the frost resistance of polymer-modified fast-hardening cement mortar under winter climate conditions in Lanzhou. The macro properties of the fabricated mortar were characterized by compressive strength and flexural strength, and the microstructures were investigated by MIP, FTIR, and SEM. It was found that with increasing polymer doses, the frost resistance of the fast-hardening cement mortar was improved, and the flexural strength increased gradually, but the compressive strength showed an opposite evolutionary trend. The overall performance of mortars was best when the content of polymer admixture was 4%, by mass, of the cementitious material. In addition, the polymer significantly refined the pore structure in the range of 3–10 nm, which made the total porosity of the system increase. Meanwhile, the polymer could be involved in the chemical reaction to generate polymer film and interlap with the needlelike ettringite (AFt) to form a spatial network structure, as shown by FTIR and SEM analysis. This means that incorporating polymer 5010N improved the microstructure of the fast-hardening cement mortar, leading to improved frost resistance.

Simultaneous tolerance intervals for linear regression models using an adjusted product set method

Pointwise tolerance intervals for linear regression models are well established in the literature, however, there is no gold standard for a procedure to construct simultaneous tolerance intervals for linear regression models. The existing methods vary considerably with respect to their finite sample performance in terms of coverage probabilities. Moreover, the numerical investigations into their coverage performance have only been conducted under very limited settings. In this work, we investigate the coverage performance for the major procedures available for the construction of simultaneous tolerance intervals for linear regression models, with increasing complexity in the structure of the models considered. We further show that an adjustment made to the confidence level for a product-set-based method provides coverages close to nominal for the majority of models considered, and this adjusted method is nearly always better than each of the other existing methods. Simultaneous tolerance intervals are then constructed and interpreted for a chemical oxygen demand regression model and two models for the strength of polymer-modified cement mortar.

Study on skid resistance and skid-resistance durability of polymer modified cement mortar based on surface texture properties

In this paper, the effects of the three polymer emulsions-EVA, XSBRL, and SBR, on the skid resistance and skid-resistance durability of cement mortar were investigated based on the surface texture properties of the specimens. The surface texture properties include texture roughness and texture abrasion resistance, which were evaluated by 3D surface texture parameters. Using close-up photography and reverse engineering techniques, texture data was retrieved from the surface of the specimen to determine the 3D texture parameters. The friction coefficient tester and the wet track abrasion tester were used to verify the surface texture roughness and texture abrasion resistance, respectively. The results show that the polymer content increment can significantly improve the surface texture roughness, which is beneficial to enhancing the skid resistance of cement mortar. The varying surface texture roughness improvement effects of the various polymer emulsions are the main reason for the variation in the skid resistance of the three PCMs. EVA provides the best skid resistance by effectively improving the surface texture height (Sa), symmetry (Ssk), and core material volume (Vmc) of the cement mortar. In contrast, XSBRL enhances skid resistance by increasing the surface texture sharpness (Sku), slope (Sdq), top material volume (Vmp), and surface area (Sdr), with slightly less improvement. SBR is the least effective in improving the surface texture parameters of the cement mortar and therefore has the worst skid resistance. The three polymer emulsions increased the texture abrasion resistance of cement mortar. E-PCM was the highest texture abrasion resistance, followed by X-PCM, and S-PCM was the poorest. The Vmc may have a role in the variation in texture abrasion resistance, as the more peak core material volume there is, the more material is available for abrasion. Therefore, polymer emulsions can enhance the skid resistance and skid-resistance durability of cement mortar by improving the texture properties, with E-PCM being the most enhancement effect.

Bond strength evaluation of polymer modified cement mortar incorporated with polypropylene fibers

Bond strength is the adhesion between an overlay and a substrate mortar; it is the key parameter ensuring durability and having a monolithic system. A proper bond is essential to resist any stresses associated with volume changes, freeze-thaw cycles, and vibrations at the interface. Polymer-modified cement mortar (PCM) is one of the most well-known adhesive materials, used widely as a binding agent in engineering construction. Two forms of PCM were investigated in this study. These products are known commercially as Sika MonoTop®− 620, a form of repair material for concrete structures, and DCP Cemfix 2CS, which is occasionally used as an adhesive to connect the tiles to the concrete base. The effect of polypropylene fiber with volume fractions of 0, 0.5, 0.75, and 1 % was investigated using three different water-to-binder ratios. A total of 24 distinct mixes were made. The material's compressive strength, flexural strength, and bond strength were all determined. The bond strength of each mix was assessed using the Slant-Shear and Pull-off test methods. The bond strength values derived by Slant-Shear and Pull-off tests had a high correlation, about 85 %. Furthermore, bond strength was connected with the material's compressive and flexural strength with 95 % and 86 % with Slant-Shear, and 80 % and 76 % with Pull-off, respectively.

Flexural behavior of concrete slabs strengthened with textile reinforced geopolymer mortar

This paper presents results from experimental and numerical studies on the flexural behavior of reinforced concrete (RC) one-way slabs strengthened with textile reinforced geopolymer mortar (TRGM). Eight one-way RC slabs, comprising of five TRGM strengthened slabs, two TRPM (textile reinforced polymer-modified cement mortar) strengthened slabs and one un-strengthened slab, were tested under static loading. The varied parameters in the experiments included the number of textile layers, spacing of the lateral textiles, presence of anchorage, and type of binder. Data from the tests is utilized to validate finite element models developed to simulate the flexural response of TRGM strengthened slabs. Then a set of parametric studies were conducted, to evaluate the effect of reinforcement ratio, slab thickness and the number of strengthening layers. Results from the tests and numerical studies clearly show that use of TRGM for strengthening delays the development and progression of cracks in slabs and enhances the post-cracking stiffness, as well as flexural capacity. In addition, the flexural capacity increases with increased number of strengthening layers, and decreased spacing of lateral textiles. Compared with TRPM strengthened slabs, TRGM strengthened slabs possess higher flexural capacity and better crack control. Finally, a calculation model for predicting the flexural capacity of TRGM strengthened slabs is proposed and the model predictions of flexural capacity is in good agreement with the results from tests and numerical simulations.

Influence of the cure procedure on the properties of Polymer-Modified Cement Mortars (PMCM)

To study the influence of the curing procedure polymer-modified cement mortars (PMCM) were realized in two stages. In stage 1, PMCM with different percentages of PVA (5, 10, and 15%) were produced considering two times of PVA addition in the mix (3 and 6 minutes) evaluating the fresh and the hardened state. Stage 2, focuses on analyses of different cure procedures: dry, wet, and two types of intermittent cure (dry/wet and wet/dry) by compressive, tensile strength, water absorption, and dynamic modulus of elasticity. In stage 1, the mixtures produced with 10 and 15% of PVA were selected for their results. Regarding the time of addition of the PVA to the mix, the results obtained do not show significant differences when the samples were produced with the two times. Then the addition time of 3 minutes is considered optimal, for manufacturing efficiency. In stage 2, the results show that the cure influences the performance of the PMCM, wherein the M1 cure showed the best results in the mechanical properties (justified by the correct hydration of the cement). In general, the incorporation of polymer reduced the absorption of water and the dynamic modulus of elasticity, thus contributing to producing more durable materials.

Influence of microencapsulated Phase Change Materials (PCMs) on the properties of polymer modified cementitious repair mortar

Microencapsulated Phase Change Materials (PCMs) can be directly incorporated into mortars to enhance their thermal performance. In this study, the addition of a commercial microencapsulated PCM in a polymer modified cement mortar was investigated, aiming at the development of a thermally efficient repair composite that may be used, along with textile reinforcement, for the structural and energy retrofitting of existing building envelopes. The effect of incorporating this PCM into the reference mortar at percentages ranging from 5% to 20% by wt. of solid constituents was thoroughly evaluated by assessing the physico-mechanical and thermal properties of the hardened end-product. Emphasis was placed on specific operational characteristics associated with the intended use of the modified mortar, such as its stress-strain behavior and temperature regulating efficiency. The results show a substantial drop in the mechanical properties of the composite with PCM addition, as well as an increase in its porosity and deformation capacity. In terms of thermal performance, the microencapsulated PCM contributed towards the attenuation and time shifting of temperature peaks. At dosages ≤20% by wt., it was thus possible to obtain mortars with favorable thermal characteristics, without compromising their physico-mechanical behavior to a degree that would preclude repair/strengthening applications.

In-situ assessment of the water-penetration resistance of polymer modified cement mortars by μ-XCT, SEM and EDS

Anti-water-penetration techniques are important to raise the durability of cement-based materials (CBMs). Here the water penetration resistances of cement mortars with ethylene-vinyl acetate copolymer (EVA) and styrene butadiene rubber (SBR) were in-situ and non-destructively probed by micro-focus X-ray computed tomography (μ-XCT). Caesium Chloride (CsCl) was mixed in water to enhance the contrast gradients of μ-XCT images. SEM and EDS tests were provided to assess the mortar microstructure changes induced by water penetration. Results show that the CsCl enhancement helps trace the water penetration fronts, while exerting minor influences on the water penetration kinetics. The polymers can greatly raise the resistance against the water penetration into the cement mortars. The pore blocking induced by the formation of polymer films on the surfaces of cement grains and aggregates may account for the enhanced water-penetration resistance. The findings of this work provide a new method to track the water penetration in CBMs by μ-XCT and deepen the knowledge in the anti-water mechanisms of polymer-modified cement materials.

Influence of Polymer Types on the Mechanical Properties of Polymer-Modified Cement Mortars

This is an experimental study showing the effect of four types of polymers (acrylate polymer (AC), polyvinyl alcohol (PVA), styrene–butadiene rubber (SBR), and ethylene-vinyl acetate (EVA)) on the mechanical properties of polymer-modified cement mortars (PCMs). One polymer dosage was used in this study (3%), and the effect of this dosage on PCMs was compared with a control mortar mix with 0% polymer. The compressive, flexural, and pull-off bond strengths were measured and compared with previous results in works of literature. The effect of polymer addition on improving the mechanical properties of PCMs was clarified, and this effect was more obvious on the flexural strength than that on the compressive strength. The PCMs containing EVA showed the best performance, with up to 33% and 63% increases in compressive and flexural strengths after 28 days, respectively. In comparison, AC, PVA, and SBR produced smaller (16%–46% compared to control) improvements in the flexural strength after 28 days. In general, PCMs containing EVA showed the best mechanical properties.

Development of banana fibers and wood bottom ash modified cement mortars

Many plant wastes have been generated from agriculture for years and as the current global drive towards a green-economy continues, more agro-based wastes will be generated in the future. Some of these wastes are being used presently as a form of renewable energy and result into ashes which are sent to landfills. However, previous studies have shown that ashes could be used as cement replacement while others considered the use of these agricultural wastes from plants as fiber reinforcement in cement appli-cations. In this study, an environment friendly solution was provided to replace cement with wood bot-tom ashes at 10, 15, 20 and 25% levels and modify the mortars produced with styrene butadiene polymers for improved strength. Also, as a way of providing sustainable path towards utilization of wastes from plant fibers, banana fibers were treated with alkaline solution and used to reinforce the polymer modified cement mortars. The developed cement composites were subjected to mechanical tests, microstructural, elemental, functional group and thermal conductivity analyses. It is realistic to conclude that optimum performance of the composite can be obtained when cement is replaced by up to 10% of wood bottom ash, 1.5% of banana fiber content and of 0.3% of styrene butadiene polymer emulsion The composite developed provided good thermal insulation properties and could be used in some selected cement based applications.

Rheological, mechanical, and abrasion characteristics of polymer-modified cement mortar and concrete

The settlement of fresh concrete or improper operation during construction usually makes the water to cement (w/c) ratio of the cement mortar on the concrete pavement surface higher than designed, which may influence the abrasion resistance of concrete pavement. This study firstly tried to establish relationships between abrasion of hardened cement mortar and rheological characteristics of fresh cement mortar in the laboratory. Secondly, a polymer-modified cement mortar was developed with carboxyl styrene butadiene rubber latex added to the cement mortar. Its rheological properties in mixing, mechanical properties, and abrasion were investigated. It is found that the polymer-modified cement mortar has a much better abrasion resistance and flexural strength while lower compressive strength than cement mortar. A stronger correlation was observed between flexural strength rather than compressive strength and abrasion resistance of cement mortar. The proposed polymer-modified concrete also exhibited good abrasion resistance.

Effect of water-based acrylic copolymer on void systems of cementitious repair mortar

Recent literature has found excessive air content as a drawback in the polymer-modified cement mortars. Excessive air content has an adverse impact on the compressive strength of polymer-modified, cement-based mortars. Entrapped air voids in the cement based mortars are typically classified greater than 1 mm in diameter. In contrast to these voids, the entrained air voids (<1 mm) are identified as fine voiding systems in the cement matrix. Modification of cement-based mortars through polymers commonly leads an increase in entrapped air voids volume. This increase developed a concern of reducing the compressive strength of the polymer-modified mortars. Therefore, the objective of this article is to assess this concern by introducing a new composition of Styrene acrylic copolymers. An anti-foaming agent is introduced in this proposed copolymer in order to reduce the entrapped air voids. Quantitative image analysis is run as a well-known technique in Petrographic methods. The entrapped air volume is assessed in the samples that are modified with different polymer dosages of Portland cement within 0 to 20 0–20 wt% range. The effect of adding Styrene Acrylic on the compressive, tensile, bonding, and flexural strength are assessed within 0–20 wt% ratio of Portland cement. Quantification of air void contents reveal a decreasing trend through the entrapped air voids for samples with higher dosage of the copolymer (optimizing in dosage of 15%). This reduction in the entrapped air voids is further strengthens by the results of mechanical analyses. According to these obtained results, an inverse correlation is found between the porosity and the mechanical property of the polymer-modified mortars.

Synthesis and properties of a modified sodium carboxymethylcellulose superplasticiser

The polymeric admixture sodium-carboxymethylcellulose (CMC-Na)/poly methyl allyl polyoxyethylene ether (PHPEG)/poly sodium p-styrene sulfonate (PSS) was synthesised and used in cement-based materials. The polymer was tested using Fourier-transform infrared spectroscopy and X-ray diffraction and the results showed that the superplasticiser was successfully synthesised. The polymer was applied to cement pastes, cement mortars and concretes. The results of thermogravimetric analysis and differential scanning calorimetry showed that the polymer promoted the cement hydration reaction. With the addition of the polymer, the compressive strength of the concrete increased by 42·17%, 21·94% and 20% at age 3 d, 7 d and 28 d, respectively, and the slump increased by 29 mm. Scanning electron microscopy was conducted to characterise the plain cement mortars and the polymer-modified cement mortars and the results revealed more hydration products in the polymer-modified cement mortars.

Mechanical Degradation and Thermal Decomposition of Ethylene-Vinyl Acetate (EVA) Polymer-Modified Cement Mortar (PCM) Exposed to High-Temperature

A polymer-modified cement mortar (PCM) is widely used as a repair material for reinforced concrete (RC) structures owing to its excellent strength and durability. However, considering the maintenance of the RC structures and the use period of the structures, the change in the physical properties of the PCM should be evaluated when exposed to various high-temperature environments, such as fires. In this study, the degradation of the mechanical properties (compressive strength and modulus of elasticity), thermal decomposition of the PCM in various high-temperature environments, and the change in the pore structure of the PCM after exposure to high temperatures were quantitatively investigated. A mechanical property evaluation of PCM was performed under three heating conditions: (i) heating in a compression tester, (ii) heating the specimen in an oven to a predetermined temperature and then moving it to a compression tester preheated to the same temperature, and (iii) cooling to room temperature after heating. In the experiment, a PCM specimen was prepared by changing the polymer–cement ratio (polymer content) of ethylene-vinyl acetate (EVA), the most commonly used polymer, to perform a high-temperature sectional test from 200 to 800 °C. In addition, to investigate the change in the PCM mechanical properties in the high-temperature region, in terms of the pyrolysis of EVA, the porosity change and mass change were examined using thermal analysis and mercury intrusion porosimetry. Before heating, the compressive strength of the PCM increased with the EVA content up to 10 % of the polymer–cement ratio. Under the cooling conditions after heating up to 200 °C, the mechanical performance of the PCM was restored, whereas the degradation of the mechanical properties of the PCM without cooling was more pronounced. Furthermore, the mass loss, heat flow, and the total porosity of the PCM increased as the EVA content increased, which is correlated with the degradation of the mechanical properties of the PCM.

Experimental correlation between varying processing parameter and compressive strength of polymer-modified cement mortar composites

Experimental correlation between varying processing parameter and compressive strength of polymer-modified Cement Mortar Composites was investigated. Polymer-modified Raffia fiber (RPF) cement mortar was developed by varying the RPF from 0 to 25%. Polyester and polyvinyl alcohol (PVA) were used in the production of the cement mortar. The curing time of 28 days were used. Compressive strength of the developed composite was examined. Factorial design of the experiment can be successfully employed to describe compressive strength of the cement mortar. The results show that increasing the volume percent of RPF from 0 to 25 vol% decreased the compressive strength compressive strength by (− 3.55(PVA), − 3.815(polyester)). Polymer-modified cement mortar has a positive effect on the compressive strength by (2.12(PVA), 1.22(polyester)). The curing days appear to be the most important variable with main effect of (5.043(PVA), 7.535(polyester)). The developed linear equation model can be used in predicting the compressive strength of the composites within the selected experimental conditions.

On the polymer modified cement mortars with different lightweight aggregates in marine environment

AbstractHaving a light weight is a design objective for offshore and coastal structures and in order to reach this aim, use of lightweight concrete consisting lightweight aggregates and polymers is a feasible solution. In this study, materials obtained from locally available crushed volcanic scoria as main aggregate and some additional lightweight aggregates with ceramic, perlite and andesite as well polymers were used in the mixtures with different proportions (totally 14 mixtures) to propose feasible alternatives for coastal structure designers. To evaluate the design performances of the mixtures, their properties such as density, cylinder compressive strength, capillarity, loss of mass under the effects of the agents in marine environment such as sodium sulphate and sodium chloride were obtained experimentally. It was found that mixtures with scoria aggregates showed more favourable results and additional aggregates gave flexibility to the designer to lower densities up to 40 % ‐ 60 % of normal‐weight mixtures. Polymer modification also improved the performance of the related materials.

Development of Polymer Modified Cement Mortars for Waterproof

The paper describes the raw materials and properties of polymer modified cement mortars for waterproof. In this paper, the following aspects were discussed, the effect of different polymer cement ratio on the ratio of compressive strength to flexural strength, the mechanism of the improvement of impermeability, durability and viscosity by the cooperation of super mineral powder and re-dispersible powders respectively. In addition the effect of graded sand and fiber on the cracking resistance and contractility of mortar were also studied.