Mechanical Properties Of Mortar Research Articles

Influence of geometric shape, pore structure and surface modification of recycled fine aggregate on the rheology behaviour and strength development of mortar

The complex physical properties of recycled fine aggregate affect the rheological and mechanical properties of mortar, thereby limiting its application in cement-based materials. This paper evaluated the geometric shape and pore structure of natural fine aggregate (NFA), recycled fine aggregate (RFA), and recycled fine aggregate modified by water glass (MRFA), and studied its water absorption and bulk density. The influence of complex physical properties of RFA before and after modification on the rheological behavior, strength development, and microscopic properties of mortar was analyzed. The rheological tests were carried out on the fresh mortar with 7 mixes, and the compressive strength and flexural strength of hardened mortar after curing for 3, 7 and 28 days were tested. The results shown that the modification of water glass has improved the water absorption and geometric shape of RFA to some extent, resulting in a small increase in the apparent viscosity and yield stress of recycled mortar compared to NFA mortar. When the replacement level of RFA was less than 30 %, the compressive strength of recycled mortar was 13 % higher than that of NFA mortar. As the replacement level increased to 40 %, the incorporation of water glass also helped to improve the mortar strength. The irregular geometric shape and high water absorption of RFA were conducive to achieving dense mechanical bonding and reducing the Ca/Si ratio in the interface transition zone.

Study on the influencing factors of mechanical properties of anti-icing modified asphalt mortar

Accumulated snow and ice on road surface affect traffic operation. Anti-icing asphalt pavement is widely implemented as an active snow melting technology. However, there are few studies on anti-icing modified asphalt mortar mechanical properties and the effect of mortar materials on the interaction between modified asphalt and anti-icing filler. For this reason, this study investigated the mechanical properties of asphalt including rheological, high-temperature, fatigue and low-temperature properties through frequency and temperature scan, multiple stress creep recovery, linear amplitude scan, and single edge notched beam test. Based on this, the significant factors affecting asphalt mechanical properties were identified by analysis of variance. Subsequently, the Palierne-C-G* parameter was used to quantify the interaction between modified asphalt and anti-icing filler, and the effect of asphalt chemical structure on the interaction was revealed by Fourier Transform Infrared Spectroscopy (FTIR) test. The results indicated that the anti-icing filler significantly improved the high temperature and fatigue resistance of asphalt. Compared with SBS modified asphalt mortar, the mechanical properties of composite modified asphalt mortar were superior. The most significant factor affecting the mechanical properties of SBS modified asphalt mortar was modifier dosage, while the most significant factor affecting the composite modified asphalt mortar was crushed rubber dosage. The interaction showed a decreasing trend with the increase of frequency, while it appeared to increase and then decrease with the increase of temperature. The carbonyl functional group of asphalt correlated best with the interaction between asphalt and filler.

Effect of titanium dioxide on fresh and mechanical properties of Mortar: A review

Nanotechnology-based engineering approaches are rapidly developing throughout the world. Modern, cutting-edge nanotechnology has proven useful in a variety of technical applications. In emerging and developed countries, increasing infrastructure needs a considerable amount of cement, which has a significantly impact on the environment and human health, resulting in greenhouse gas emissions and severe acute respiratory illnesses (asthma and silicosis, respectively). To overcome such difficulties, cement consumption in building materials must be reduced. Several novel extra materials have lately been introduced to improve the performance of mortar. Nano-titanium dioxide (NT) in cement mortar is widely used in green building construction because NT capable to the degradation of air pollution, self-cleaning, and enhancing mechanical, microstructural, and durability properties. In this paper, the effect of NT on fresh and hardened properties of cement mortar has been discussed. For the collection, screening and implementation of data for review paper PRISMA analysis and VOSviewer technique was used. Existing literature indicates that the reduction in workability 15% − 20% whereas improvement in compressive strength (CS) up to 15% and tensile strength up to 45% was noted with NT in mortar. Current research supports using NT as a cement replacement in mortar. Aside from the key findings, some identified gaps, problems, and future scope challenges have been presented in order to develop NT based mortar as a sustainable material in the building sector.

Effect of activator concentration on setting time, workability and compressive strength of sustainable concrete with alkali-activated slag binder

The global need to reduce carbon dioxide (CO2) emissions prompted studies on sustainable alternatives to conventional concrete made with ordinary Portland cement (OPC) binders. Alkali-activated ground granulated blast furnace slag (GGBS) is a promising sustainable to OPC in terms of the impact on the environment and reduction of CO2 emissions. Concretes and mortars made with alkali-activated binders demonstrate promising fresh and mechanical properties. This article presents the findings of an experimental study investigating the fresh and mechanical properties of mortar using alkali-activated GGBS binder. The activators used were sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution with 6 M, 8 M, 10 M, and 12 M molarities. The study assessed their initial setting time, workability, and 28-day compressive strength. The study evaluated the effect of partial replacement of GGBS with 5 % silica fume. The compressive strength was determined after 28 days of curing in three different environments: 1) ambient air temperature, 2) water submersion, and 3) water immersion for 7 days followed by 21 air curing in ambient temperature. The results showed an increase in compressive strength with higher NaOH concentration but a corresponding decrease in initial setting time and flowability. Depending on the curing method, efflorescence, and blue-green pigmentation were seen during the physical assessment of the samples. The highest 28-day compressive strength was 67.5 MPa when the NaOH activator molarity was 10 mol/L which represents an optimum concentration for strength development. Replacing 5 % of the GGBS binder with silica fume resulted in a decrease in the 28-day compressive strength and workability without affecting the initial setting time.

The Effect of Different Proportions of Waste Rubber Substitution on Alkali-Silica Reaction and Mechanical Properties in Mortars

This study investigates the alkali-silica reaction (ASR) and mechanical properties of mortars containing crumb and powder rubber instead of river sand. In this regard, mortars were produced using waste rubber whose ratios in the mixture are 0%, 3%, 6%, 9%, 12%, 15%, 18%, and 21%. ASR expansion, compressive and flexural strength tests were conducted on the samples. ASR measurements were performed on days 3, 7, 14, 21, and 28. Besides, at the end of the ASR experiment, the microstructures of the mortars were examined using scanning electron microscope (SEM) images. Examining the results of this study reveals that the use of waste rubber in rising portions in the mortars led to an increase in the ASR expansions of the mortars. The study shows that the ASR expansions of the mortar samples that have 9% and 15% waste rubber replacement are comparatively higher than the other mortar samples. Furthermore, the results of the SEM analysis verified this finding. The study demonstrates that 3% of waste rubber mortar samples have the highest compressive and flexural strengths. On the other side, the ASR expansion of the mortars with 3% substituted waste rubber was considerably low compared to other mortars containing waste rubber. These findings (ASR, compressive and flexural strength tests results) show that using 3% waste rubber is ideal for producing mortars and supports a sustainable production approach in the sector.

Effects of reactive MgO on durability and microstructure of cement-based materials: Considering carbonation and pH value

Reactive MgO is a type of eco-friendly material with a lower carbon footprint, as it is produced by calcination of magnesite (MgCO3) at 750 ℃, much less than that (i.e. 1450℃) needed for calcination of (CaCO3) to produce clinker for Portland cement. Carbonation can enhance the mechanical properties of reactive MgO-based cementitious materials but will lower the pH value, leading to the neutralization of cement-based materials and further deterioration in rebar passivation. In this study, varying amounts of reactive MgO (0%, 10%, 20%, and 30%) were incorporated into mortars as cement replacements. By adjusting the duration of CO2 curing (i.e. carbonation curing) and standard curing, it was found that the curing regime involving 36 hours of carbonation curing plus 26.5 days of standard curing led to a higher pH and compressive strength of cement mortars. The pore size distribution was improved as the internal pores of the mortar were filled with carbonation products, which hindered the reaction between CO2 and alkaline hydration products inside specimens and was conducive to maintaining the alkalinity within the mortar. Therefore, the chloride ion penetration resistance and the mechanical properties of mortar were enhanced. SEM and EDS characterization results indicate that the excessive MgO did not fully participate in carbonation and continuously hydrated to generate Mg(OH)2. The expansion of Mg(OH)2 led to crack formation inside the mortar and reduced its strength, which accelerated CO2 diffusion and further reduced the pH value of reactive MgO-based cementitious materials.

PCCP Mortar Protection Layer Research Progress

Prestressed steel cylinder concrete pipe (PCCP) has the characteristics of high strength, excellent impermeability, strong sealing and easy installation, and has become an irreplaceable first choice pipe in China's long-distance water diversion project. However, in the process of using PCCP, there will be pipe bursts and other phenomena, most of which are caused by the broken wire of the prestressed steel wire, and the most important function of the protective layer of PCCP mortar is to protect the prestressed steel wire. In this paper, the research progress of PCCP by scholars at home and abroad is reviewed from five aspects: PCCP working environment, mortar mechanical properties, mortar durability, mortar thickness and mortar curing. as well as testing the durability of the mortar through different solution environments; The research prospect of the production of PCCP mortar protective layer, the detection of PCCP mortar protective layer, and the monitoring of PCCP mortar protective layer were carried out, which provided reference enlightenment for the development of PCCP mortar protective layer.

Investigation of gradient properties for cement mortar interfacial transition zones and their effects on mechanical characteristics using micro-CT

The interfacial transition zone (ITZ) in cement-based composites with aggregates is widely recognized as the most vulnerable component, greatly affecting their physical and mechanical properties. In this study, the effect of the ITZ characteristics on the mechanical behavior of cement mortar using its actual microstructure was investigated with image-based numerical approaches in this study. The volumetric information of the ITZ of the mortar sample was obtained and characterized from high-resolution synchrotron micro-computed tomography (micro-CT) images. The mechanical properties of the mortar were evaluated using the finite element method, based on the components characteristics represented by grayscale information of the micro-CT images. It was found that the adhesion between the aggregates and binder was well replicated in the simulation with the multiple-phase model, based on the gradient characteristics and properties of the ITZ. Considering the ITZ thickness according to the aggregates size, a more realistic crack propagation trend can be observed. The obtained results confirmed the significant influence of the ITZ thickness and phase distribution characteristics on the mechanical properties of cement mortars, emphasizing the importance of considering ITZ phases for accurate material analysis.

The effect of nano-biochar produced from various raw materials on flow and mechanical properties of mortar

ObjectivesThe objectives of this study are to determine the effects of nano-biochar produced from waste sludge (industrial and municipal) and a hybrid combination of municipal sewage sludge biochar and lignocellulosic biochar (apricot kernel shell) on the fresh state (flow) and mechanical properties (compressive strength, flexural strength, and fracture energy) of mortar. MethodologyAs methodology, the biochar was produced by a pyrolysis process at 500 °C and ground to 200 nm average particle size by ball milling. Detailed characterization of biochars with X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), X-ray diffraction (XRD), BET (Brunauer-Emmett-Teller) analysis, and the strength activity index test was conducted. Mortar mixtures were designed by adding single and hybrid nano-biochar with different volume percentages (between 0.04–0.15%). Flow, flexural strength and compressive strength tests were performed on mortar samples along with microstructural SEM investigations. FindingsAs major findings, the addition of 0.06% municipal sewage sludge nano-biochar (BCSS) resulted in an increase in flexural strength by 23% while an increase in fracture energy by 100% compared to the control mortar. The addition of 0.12% BCSS increased the compressive strength by 17% and the compressive fracture energy by 28%. The hybrid nano-biochar additions also improved the strength and ductility. Sewage sludge nano-biochar and hybrid combinations have the potential to enhance the performance of the cement composites. The mechanisms governing the nano-biochar effect on mortar were enlightened as: pore filler effect, crack bridging and divergence, hydration initiation cite, internal curing of mortar. NoveltyNovelty of this work are: the use of nanoscale biochar in cement composite; the use of nano-biochar derived from sewage and industrial sludge in cement composite; the investigation of the effect of a hybrid nano-biochar on the properties of cement composites. The use of nano-biochars in cement composites can enable waste recycling while improving environment protecting and the mechanical properties of cement composites.

Cement-Based Mortars with Waste Paper Sludge-Derived Cellulose Fibers for Building Applications

This study assesses the mechanical properties of mortars incorporating waste paper sludge-derived cellulose fibers. Compression and flexural tests were carried out on specimens prepared with cellulose fibers at different proportions, ranging from 0% to 2% of the total weight of the solid mortar constituents (cement, sand, and lime). In addition, a comparative analysis was carried out to evaluate the influence of the preparation method on the mechanical properties of the mortars. To this end, two series of mortars were studied: one prepared following a rigorous control of the preparation parameters and the other made without systematic parameter control to simulate typical on-site conditions. Finally, the applicability of both traditional and eco-friendly mortars in the construction of small-scale masonry walls was assessed through compression tests. Overall, the mechanical properties of mortars with cellulose fibers were comparable to those with 0% waste material, regardless of the production process. Regarding the compressive behavior of masonry walls, experimental tests showed significant similarities between specimens made with traditional and eco-friendly mortar. In conclusion, incorporating cellulose fibers into cement-based mortar shows considerable potential for building applications, enhancing the environmental benefits without compromising the mechanical behavior.

Effect of Surface Hydrophilized Plastic Waste Aggregates Made by Mixing Various Kinds of Plastic on Mechanical Properties of Mortar.

The surface hydrophilization of mixed plastic waste aggregates (MPAs) was conducted to improve the bond between an MPA and the surrounding cement matrix using two types of coating agents: a silicone amine resin and acrylic binders. The coating agents formed a physical bond with the MPAs, and the results of contact angle measurement also revealed that the surface of MPAs was hydrophilic. The workability of a mortar mix increased by up to 1.47 times with the surface hydrophilization of MPAs. Meanwhile, the compressive and flexural strengths of mortar mixes decreased by 29~43% and 72~86%, respectively, at 28 days with the surface hydrophilization of MPAs. Namely, the surface hydrophilization of MPAs was successively conducted, and the workability of mortar mixes was improved accordingly, but the compressive and flexural strengths of mortar mixes decreased as the physical bond was partially separated from not only the MPA but also the surrounding cement matrix and the surface friction was decreased.

Effect of Using Recycled Colemanite Waste and Cathode Ray Tube Glass in the Cement Mortar on Physical and Mechanical Properties

In this study, the performance of colemanite, which is a valuable boron waste, and recycled cathode ray tube glass (CRT) in the cement mortar was examined by experimentally. Colemanite waste (CW) and CRT were replaced with cement and aggregate and used as mineral additives, and their effect on the physical and mechanical properties (PP and MP) of mortar was investigated. In addition to the reference sample that didn’t contain CW or CRT, seven more samples were used. In these samples, cement was used at a rate of 2.5% along with CW, and the aggregate was replaced with CRT at the rates of 10%, 20%, and 30%, and with the combination of CW and CRT. The workability, unit weight, and water absorption, compressive strength (CS), flexural strength (FS), and abrasion resistance properties of the mortars were compared. As a result of this study, it has been observed that the use of waste materials can make positive contributions to some of the PP and MP of the mortar. Thus, the goal of both improving the properties of the mortar and making it affordable by using waste materials were achieved.

Study on the Influence of Magnesite Tailings on the Expansion and Mechanical Properties of Mortar.

To reduce the mining of high-grade magnesite and solve the environmental pollution caused by magnesite tailings, magnesite tailings were used to produce MgO expansion agent (MEA), and a detailed study of its performance was carried out in this study. Firstly, the effects of different calcination times on the calcination products, the specific surface area, and the activity of MEA were analyzed. Then, the MEA produced by calcinating at 950 °C for 1 h was taken as the research object, and the effects of its content on the expansion performance, compressive strength, and flexural strength of the mortar were studied. The results showed that the decomposition of magnesite tailings after high-temperature calcination produced MEA, and the longer the calcination time, the lower the activity. The calcined tailings could compensate for the shrinkage of the mortar, and the expansion increased with the increase in curing temperature. What is more, when the content was less than 8%, the hydration of MEA filled the pores and improved the compactness, so the strength of the mortar increased with the increase in the expansion agent content. When the dosage was greater than 8%, excessive expansion increased the porosity, causing harmful expansion of the mortar and damaging its integrity, leading to a decrease in strength. Fly ash reduced the expansion of mortar, and after adding 30% fly ash, the expansion decreased by 20.0-36.1%, and the ability to suppress expansion decreased with the increase in curing temperature.

Influence of Lime on Strength of Structural Unreinforced Masonry: Toward Improved Sustainability in Masonry Mortars

The choice of a sustainable construction material needs to take into account not just the environmental impact of the material, but according to the 2030 Agenda for Sustainable Development by the UN, one also needs to consider ease of access, the utilization of locally available materials, and the durability and reliability of the construction itself. Mortared masonry has been used around the world for several hundred years as an accessible type of construction. In masonry mortars, lime and cement are often integrated together for combined advantages: enhanced workability, breathability, and better environmental performance due to the former, and higher strength and shorter setting duration due to the latter. However, despite being extensively studied for their effects on the mechanical properties of mortar, not much is known about the impact of varying lime and cement ratios in the binder on the mechanical performance of masonry as a whole. Variations in the properties of mortars do not always have a significant impact on the mechanical behavior of masonry structures. Therefore, this article details an experimental campaign to measure the compressive strength, E-modulus, flexural strength, and shear bond strength of masonry samples containing two distinct lime–cement mortars (1:2:9 and 1:1:6 cement:lime:sand) and one cement mortar (1:0:5). The results show that more than the presence of lime in the mortar, the strength of the mortar influenced the flexural strength of the masonry ranging from 0.1 to 1.2 MPa. No discernable correlation was observed between the presence of lime in the mortar and the cohesion in the masonry (0.29 to 0.41 MPa). The values of the compressive strength (6.0 to 7.2 MPa) and E-modulus (3.8 to 4.5 GPa) of the masonry decreased and pre-peak ductility increased with an increase in the quantity of lime in the mortar. The recommendations of Eurocode 6 for the flexural strength of the initial shear bond strength were found to be conservative for different mortar strength classes, and significantly unconservative for compressive strength (by 50% to 70%).

Development of Lightweight Mortars Using Sustainable Low-Density Glass Aggregates from Secondary Raw Materials.

In this study, different lightweight expanded glass aggregates (LEGAs) were produced from glass cullet and various carbonated wastes, through a thermal impact process. The effects of LEGA microstructure and morphology on both the adherence to the cement paste and the mechanical properties of mortars after 28 days of curing were studied. The properties of lightweight mortars made of either LEGAs or expanded clay aggregates were compared. The results demonstrated the feasibility of using LEGAs to produce glass lightweight aggregate mortar, with flexural and compressive strength values ranging from 5.5 to 8.2 MPa and from 28.1 to 47.6 MPa, respectively. The differences in mechanical properties were explained according to the microstructures of the fracture surfaces. Thus, arlite-type ceramic aggregates presented surface porosities that allowed mortar intrusion and the formation of an interconnected interface; although the surfaces of the vitreous aggregates were free from porosity due to their vitreous nature, the mortars obtained from different wastes presented compressive and flexural strengths in the range of lightweight mortars.

Microstructural and mechanical properties of photocatalytic cement mortar with g-C3N4/CoAl-LDH nanoflowers

The g-C3N4/CoAl-LDH nanoflowers with a strong photocatalytic activity under UV–visible light irradiation was synthesized and applied with different dosages to prepare photocatalytic cement mortars (PCM). Besides the photocatalytic assessment by NOx degradation, the effect of g-C3N4/CoAl-LDH on the microstructural and mechanical properties of cement mortars were investigated by means of X-ray diffraction (XRD), X-ray computed tomography (X-CT), mercury intrusion porosimetry (MIP), capillary water absorption and strength tests. The results show that in addition to the unique air self-purification characteristics, g-C3N4/CoAl-LDH can promote cement hydration with filling effect and further improve the microstructural and mechanical properties of mortar. Moreover, the ability of g-C3N4/CoAl-LDH to capture CO32− can alleviate the influence of carbonation on photocatalytic performance. Therefore, g-C3N4/CoAl-LDH exhibits lasting photocatalytic performance in cement-based materials. This work is expected to contribute to the effort of searching for new multifunctional nano-additives for improved sustainability of building materials.

The Effects of Crystalline Admixture on the Self-Healing Performance and Mechanical Properties of Mortar with Internally Added Superabsorbent Polymer.

Crystalline admixture (CA) can be incorporated into concrete to achieve self-healing of concrete cracks. In this study, both CA and superabsorbent polymer (SAP) were used as self-healing agents to investigate the effects of CA on the self-healing performance and mechanical properties of mortar with internally added SAP at different self-healing ages. The healing effect of cracks in mortar is assessed by crack observation and impermeability. The structure and composition of the filler in the cracks were analyzed by microscopic experiment. The experimental results indicate that CA enhances the healing of cracks in mortar specimens. The chemical reactions of CA primarily contribute to significantly improving the early-age crack-healing ability of the specimens, and the water absorption and expansion ability as well as the internal curing effect of SAP also facilitate the crack-healing process. Increasing the CA content leads to an increase in the Ca/Si ratio of C-S-H, causing a transition from a layered structure to a more compact needle-like structure. When 4% CA was added to the mortar, it resulted in an adequate formation of needle-like C-S-H structures, which eventually penetrate and fill the pits formed by SAP, compensating for the strength loss caused by SAP.

Mehanička svojstva morta s dodatkom aditiva EarthZyme

Concrete is the most widely used building material in the world. However, owing to the high CO2 emissions from the production of cement, its use has been questioned, and attempts have been made to improve it. Various chemical additives are being used to improve concrete properties. Enzymes are organic materials and have been especially favoured in recent years owing to their low costs when used in traditional soil stabilisation methods. This study used the ‘EarthZyme’ enzyme as a plaster mortar additive and investigated its effects on the mechanical properties of mortars. EarthZyme completely biodegrades in nature and is used for soil stabilisation. By producing mortar specimens with additive enzyme ratios of 0 %, 0.01 %, 0.02 %, 0.03 %, and 0.04 %, the effects of the enzyme additions on the mechanical properties of the mortars (ultrasonic pulse velocity UPV, flexural strength ff and compressive strength fc) were determined. The flow table values of the mortar specimens in the flow table test varied within the range of 15–17 cm. According to the results, the flow table values of the mortars increase with an increasing addition rate of EarthZyme. Although the additive ratio of the EarthZyme does not significantly affect the mechanical properties of mortars at early ages (3 days), the enzyme addition ratio reduces the UPV and fc while improving ff at late ages (28 days). The enzyme addition ratio has no significant effect on the UPV and ff but has a significant effect on fc.

Numerical modeling to predict the impact of granular glass replacement on mechanical properties of mortar

Numerical modeling to predict the impact of granular glass replacement on mechanical properties of mortar

Mechanical Properties of Cement Mortars Reinforced with Polypropylene Fibers Subjected to High Temperatures and Different Cooling Regimes

This study experimentally investigated the mechanical properties of cement mortars that were reinforced with polypropylene (PP) fibers after being exposed to high temperatures and cooled under different regimes. PP fibers were added in amounts of 2, 3 and 4 kg/m3, the residual strengths of the mortars exposed to various temperatures up to 500 °C and cooled under different regimes were determined. It was found that the addition of PP fiber at the level of 2 kg/m3 improves the residual flexural and compressive strengths up to 300 °C. The residual flexural strength was approximately 75%, which is 15% higher than that observed in the simple mortar, and the same happens with the residual compressive strength which was approximately 85%, which is 17% higher than that observed in the simple mortar, regardless of the types of cooling used on the specimens. It was determined by means of a statistical analysis that there are no significant differences in the mechanical properties of the mortar according to the cooling regimes used, after having been exposed to high temperatures. The correlation of the residual flexural and compressive strengths was achieved with a coefficient of determination, R2 = 0.82, and the relationships between the variables were considered acceptable regardless of the types of cooling used.