Mortar Aggregate Research Articles

Synergetic effect of a chemical activator and blast-furnace slag on enhancing recycled aggregate mortar

The inferiority of recycled fine aggregate mortar (RFAM) is a major obstacle to its utilisation and a method to enhance RFAM is thus necessary to scale up applications. The concept behind the method proposed in this paper involves using a calcium hydroxide solution to pre-coat the surface of recycled fine aggregates in order to activate blast-furnace slag incorporated in RFAM to enhance performance. The results of this experimental research showed that, compared with conventional RFAM, the synergistic effects of using a calcium hydroxide solution and blast-furnace slag in RFAM produced better workability, earlier setting time, higher compressive strength at early and later ages, higher flexural and splitting tensile strengths, a lower volume of permeable voids, a greater formation of hydration products, a lower water absorption by immersion and a lower rate of capillary absorption. The method was found to enhance the performance of RFAM remarkably and, in addition, is economically and environmentally feasible.

Effect of Maximum Size of Aggregate on the Behavior of Reinforced Concrete Beams Analyzed using Meso Scale Modeling

In this study, simply supported reinforced concrete (RC) beams were analyzed using the Extended Finite Element Method (XFEM). This is a powerful method that is used for the treatment of discontinuities resulting from the fracture process and crack propagation in concrete. The mesoscale is used in modeling concrete as a two-phasic material of coarse aggregate and cement mortar. Air voids in the cement paste will also be modeled. The coarse aggregate used in the casting of these beams is a rounded aggregate consisting of different maximum sizes. The maximum size is 25 mm in the first model, and in the second model, the maximum size is 20 mm. The compressive strength used in these beams is equal to 26 MPa.
 The subjects of this study are two RC beams subjected to a two-point loading designed to fail due to flexure. The RC beams under loading were studied in the laboratory as well as numerically. ABAQUS program was used for modeling and analyzing the RC beams. The mesoscale modeling that was used to model the concrete required used a special program using different programs but has not used the ABAQUS program directly. The result of the comparison between the numerical and experimental showed that the mesoscale numerical model gave results that were more approximate to the experimental ones, and the mesoscale modeling of reinforced concrete is most convenient when the maximum size of aggregate is decreased.

Synergetic recycling of waste glass and recycled aggregates in cement mortars: Physical, durability and microstructure performance

The generation of large quantities of waste glass and construction waste has increasingly become an environmental burden in city governments. This study investigated the joint utilization of recycled glass cullet (RGC) and recycled fine aggregates (RFA) in cement mortars. The mechanical, durability and microstructure properties of the cement mortars were evaluated. The experimental results showed that the synergetic reuse of RGC and RFA in cement mortars was feasible both from mechanical and durability points of view. The replacement of RGC by RFA was beneficial to enhancing the compressive strength of cement mortars due to the improvement of the interfacial transition zone and microhardness of the paste matrix, and the refinement of the pore structures. Encouragingly, the combined use of RGC and RFA in cement mortars could exhibit low drying shrinkage and alkali-silica reaction expansion. In particular, the acid resistance of the cement mortars was improved effectively when the RGC was used in conjunction with RFA as 100% fine aggregates in the mortars.

Properties of eco-friendly cement mortar contained recycled materials from different sources

Building materials such as sand, cement, bricks, and steel are usually the main components of the construction sector. All these materials are produced from existing natural resources and they will cause substantial damage to the environment as a result of their continuous depletion. Moreover, during the manufacture of various building materials, especially cement, a high concentration of carbon dioxide is constantly emitted into the atmosphere. Therefore, to reduce this environmental damage as well as to save natural resources, this study was performed to recycle the wastes of some of building materials such as marble, granite and porcelain tiles and clay brick through using them as cement and aggregate replacement materials in cement mortar. Sixteen mixtures were cast for this study. In addition to the control, the mortar mixes were divided into five groups, three mixes in each group. In four of the five groups, cement was replaced in three proportions (5%, 10%, 15% by weight) with each of marble, granite, porcelain and clay brick waste powders (passing through 150-μm sieve). The fifth group included 100% replacing (by weight) of the natural sand with the marble, granite and porcelain tiles wastes (with a comparable gradation). The influence of these wastes on flow rate, compressive strength, flexural strength, bulk density, ultrasonic pulse velocity (UPV) and water absorption tests were observed. Results showed that it is possible to produce an eco-friendly mortar made with 100% recycled marble or porcelain aggregate with a significant improvement in the mechanical and durability properties in comparison with natural aggregate mortar.

Mineralogical Characterization of Historical Cement-based Mortars from the Rupnik Military Fortification Line

ABSTRACT This paper presents the results of cement-based mortars characterizations that were taken from rendered layers of military bunkers in the Rupnik Line. The Rupnik Line was conceived as a part of the fortified defence system protecting the Rapallo Border between the Kingdom of Italy and the Kingdom of Yugoslavia, established in 1920. The bunkers were built between 1938 and 1941, and the renders of various compositions were applied as a camouflage layer that merged the bunkers with the environment. Results of petrographic examination and microstructural and chemical analysis of the samples confirmed that locally available crushed dolomite or limestone sands were used as an aggregate in the mortars. As binders, pure Portland cement or a mixture of cement and ground granulated blast furnace slag were used. The selection of the aggregate and binder type in a particular mortar was based on the colour of the artificial stone produced. All samples with the dolomite aggregate show the presence of alkali-aggregate reactions, dedolomitization of the grains and secondary calcite formation in the cement binder, along with the Mg-Al, Mg-Si and Mg-Al-Si phase formations. In mortar compositions with a high Portland cement content, the presence of delayed ettringite formation was also confirmed.

Physical properties and microstructure of plastic aggregate mortars made with acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC), polyoxymethylene (POM) and ABS/PC blend waste

This paper investigates cement mortars made with waste plastic aggregates (polycarbonate-PC-, polyoxymethylene -POM-, acrylonitrile-butadiene-styrene -ABS-, an ABS/PC blend -ABSC- and polyethylene terephthalate -PET-) as partial sand replacements at 5–20% by volume.Even at 20% plastic content, the strength surpasses the standard strength requirements for masonry, rendering and plastering mortars, with compressive strengths ranging from c.37–71 MPa and flexural strengths reaching 4–9 MPa. Most plastics, in contents up to 15%, enhance the flexural strength of the standard cement mortar which can improve the resistance to tensile stress caused by loading and expansion by frost, salt or swelling clays.The plastic aggregates increase the cement mortar's ability to deform on stress application, delaying failure and turning the typical brittle failure of cement mortars into a ductile failure, a notable asset for those specifying repair mortars for masonry which typically deforms over time.The fall in the mechanical/hygric properties and density caused by the plastic (>15% content), is mainly due to the proliferation of disrupted interfaces rather than to the physical properties of the plastics themselves. There is not significant direct correlation between the properties of the mortars and those of their plastic aggregates – except for the compressive strength. The relationship can sometimes appear inverse, suggesting that larger differences between plastic and cement matrix properties can enhance incompatibility and lower durability. However, the grading, shape and surface characteristics of the plastic particles impact the properties of the resultant mortars. The results highlight the performance of the ABS (best graded plastic) barely rising the hygric properties, even at 15% replacement, and showing high strengths and sealed interfaces.

Effect of Recycled Iron Powder as Fine Aggregate on the Mechanical, Durability, and High Temperature Behavior of Mortars.

This study evaluates the mechanical, durability, and residual compressive strength (after being exposed to 20, 120, 250, 400 and 600 °C) of mortar that uses recycled iron powder (RIP) as a fine aggregate. Within this context, mechanical strength, shrinkage, durability, and residual strength tests were performed on mortar made with seven different percentages (0%, 5%, 10%, 15%, 20%, 30% and 50%) of replacement of natural sand (NS) by RIP. It was found that the mechanical strength of mortar increased when replaced with up to 30% NS by RIP. In addition, the increase was 30% for compressive, 18% for tensile, and 47% for flexural strength at 28 days, respectively, compared to the reference mortar (mortar made with 100% NS). Shrinkage was observed for the mortar made with 100% NS, while both shrinkage and expansion occurred in the mortar made with RIP, especially for RIP higher than 5%. Furthermore, significantly lower porosity and capillary water absorption were observed for mortar made with up to 30% RIP, compared to that made with 100% NS, which decreased by 36% for porosity and 48% for water absorption. As the temperature increased, the strength decreased for all mixes, and the drop was more pronounced for the temperatures above 250 °C and 50% RIP. This study demonstrates that up to 30% RIP can be utilized as a fine aggregate in mortar due to its better mechanical and durability performances.

Exposed-aggregate areas and photocatalytic efficiency of photocatalytic aggregate mortar

By having the potential to remove nitrogen oxide (NOx) air pollutants generated by vehicles and other anthropogenic combustion processes, particularly in urban areas, photocatalytic concrete has attracted significant commercial interests all over the world. In contrast to typical photocatalyst applications in concrete, in which titanium dioxide (TiO2) – the most utilised photocatalyst – is dispersed within the cementitious materials, the study reported here utilises titanium dioxide-coated aggregates. Used in an exposed-aggregate finish, this format aims to have a higher photocatalytic efficiency than titanium dioxide cement-bound materials. An exposed titanium dioxide-coated aggregate has the potential to provide a significantly higher proportion of catalyst to direct ultraviolet radiation and minimise lost performance due to occlusion. The exposed-aggregate surface area on the test mortar samples was measured with three-dimensional imaging techniques. Thereafter, photocatalytic efficiency was measured in comparison with that of the titanium dioxide cement mortar. The relationship between exposed area for photocatalytic reaction and photocatalytic efficiency was established. This indicated that the photonic efficiency increases with increasing exposed area, regardless of the method to support the catalyst – that is, either within the cement paste or externally mounted on the aggregate. The data confirm that exposing coated aggregate significantly enhances photonic efficiency.

Thermal behaviour of ladle slag mortars containing ferrochrome slag aggregates

Concretes, depending on their application, may be exposed to elevated temperatures during their lifetime, especially when placed near or in a furnace or during an accidental fire. The thermal stability of alkali-activated mortars and hydrated mortars prepared using ladle slag and two different aggregates was studied. A commercial calcium aluminate cement was used as a comparison for the properties after exposure to temperatures up to 1000°C. All samples were characterised and analysed through a strength test, dilatometric analysis, thermogravimetric analysis, ultrasonic pulse velocity and scanning electron microscopy. The hydrated ladle slag mortars exhibited properties similar to or better than the commercial calcium aluminate cement, while the alkali-activated ladle slag's thermal properties were inferior to the hydrated ladle slag mortars. The tests also showed that the use of ferrochrome slag aggregates in hydrated ladle slag mortars exhibited similar properties to those using sand aggregate mortars. The damage behaviours of the mortars were dependent on the temperature-induced dehydration, dehydroxylation and thermal incompatibility between the paste and aggregates. The results from this study specify the possibilities of using 100% industrial by-product-based mortar and near-zero carbon dioxide emissions as a fire-resistant material in furnaces, buildings and fireplaces.

Compatibilization of recycled rubber aggregate in mortar

The incorporation of rubber aggregates from tire wastes into mortar is a way to reach new properties of materials based on Portland cements and to generate alternatives for the mechanical recycling of tire rubber waste. However, the rubber aggregates present distinct chemical characteristics when compared to the others mortar components, leading to a low interface interaction between the rubber and the cementitious matrix and consequent reduction of mechanical properties of the material. Thus, the aim of this study was to evaluate the compatibilization in rubberized mortar, using unsaturated polyester resin as coupling agent to cover the rubber particles and chemically bond them to the others mortar components. The compatibilization methods employing the adhesion systems rubber–sand, rubber–cement and rubber–sand–cement were analysed and the compatibilized materials were characterized by mechanical test and scanning electron microscopy. The compatibilization caused positive changes in the rubberized mortar, generating perspectives for development and application of the material.

Synergetic effect of waste tire rubber and mil scale on electromagnetic wave attenuation properties of new generation mortar

In this study, the behaviors of cement based building materials containing a certain amount of crumb rubbers (CR) and mill scales as additives were explored. For this purpose, five different CR content by volume of the natural fine aggregate mortars and different mill scale (MS) doped rubberized mortars were prepared. The CR and MS used in the study were obtained from waste tires and rolling mill facility which are desirable due to economic and environmental reasons. EM behaviors of the samples were explored in the frequency range of 3–12GHz for the first time in the related literature. Flexural and compressive strength tests are then carried out. The crystallinity and morphology of the mortars were also investigated with X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The increment of rubber content in the mortar reduced the reflection characteristic due to lower reverse polarizability of the structure with incident wave, related with the dielectric properties of rubber and decreased the reflection response of the mortar due to reduced polarization of the samples with increased dielectricity for incident wave. The dielectric constants of mortar including mill scale has higher values due to better polarizability of the small conductive parts in mill scale. The existence of conductive parts increases the electron mobility and polarizability of the structure. Besides, the higher ratio of rubber with the same mill scale percentage (15%) in mortar also slightly enhanced the dielectricity of the samples. The higher dielectric constant with respect to the free space gives opportunities to be used in shielding devices. The replacing crumb rubber with fine aggregate resulted in a decrease in both compressive and flexural strength.

Efficient Engineering Techniques for Segregation and Management of Non-Biodegradable Wastes: Saving the Earth by Replenishing its Dearth

The climatic conditions of the Earth seem to be deteriorating every single moment and mankind is receiving the signals of an upcoming environmental catastrophe in the forms of Global Warming, Ozone holes and Environmental Pollution. The Segregation and Management of wastes are two vital issues in the 21st century globalized world. The waste generation rates are on a sharp rise throughout the world. In 2016, the quantity of solid wastes generated globally summed up to a figure of 6.3 billion metric tonnes. With a swift population growth and rapid urbanization, scientists are expecting a rise of about 70% in the production of wastes as compared to 2016 amounting to nearly 26 billion metric tonnes of in 2050. Plastics, MPW etc. constitute a major portion of these wastes having secured an irreplaceable role in human life today. This paper majorly gives an insight to the Recycling of the globally produced wastes (after their Segregation by an IoT/GLCM/PLC based Segregator) by utilizing them in Road/ Pavement Construction, RDF, Mortar Aggregates and Toilet Blocks (Plastones) in some innovative, cost-efficient and easy-to-implement novel methods viz. Cold Plasma Pyrolysis, CMP, Injection Molding etc. for the Management of wastes to frame a greener and sustainable future. Also, certain high potential techniques for the Re-usage and Reduction of waste products have been incorporated for the Environmental amelioration.

对于赤泥沥青胶浆的沥青–集料界面粘附性研究

对于赤泥沥青胶浆的沥青–集料界面粘附性研究

Characteristics of isolation mortars produced with expanded vermiculite and waste expanded polystyrene

Mortar is one of the most important component of cement based composites. Aggregates have also a significant effect on properties of mortars. Generally natural and crushed fine aggregates are used in mortar production for different applications and aims, one of which is energy conservation in buildings and facilities. Vermiculite and waste polystyrene as aggregates in mortar presents an opportunity to reduce the unit weight and the thermal conductivity coefficient that is important for thermal isolation. Five vermiculite+polystyrene/cement ratios, 3, 4, 5, 6 and 7, by volume were used to produce mortars. In each ratio, 100% vermiculite and 100% polystyrene by volume were studied in addition to their combination at 25%, 50% and 75%. Totally, 25 mortars with 4 × 4 × 16 cm were fabricated to investigate physical, mechanical and thermal properties. It was observed that the usage of vermiculite and polystyrene in mortar makes possible the production of mortars with unit weight between 393 and 946 kg/m3 due to very high porosity up to 67.2%. This is also very important in terms of thermal conductivity which decreases up to 0.09 W/mK. Compressive strength presents a variation between 0.57 and 5.89 MPa. Mortars with vermiculite and polystyrene can be used as a good insulation material where needed.

Mesoscale Analysis of Fatigue Damage through Aggregate–Mortar Bond Cracks in Cementitious Composites

AbstractA micromechanics-based model is developed to study the fatigue response of cementitious composites. Microcrack growth, which is the predominant mechanism responsible for fatigue damage, is ...

Internal curing effect of saturated recycled fine aggregates in early-age mortar

This paper explored the potential for internal curing of saturated recycled fine aggregate (RFA) in mortar. Water release from saturated RFAs at various relative humidity (RH) values was investigated using desorption isotherms. Capillary pressure measurements and autogenous shrinkage tests for mortar (W/C = 0.30) with RFA at an early age were used to evaluate water release. The influences of the RFA particle size, water absorption capacity, and dosage were analyzed. Desorption isotherms of the RFAs showed that only 16%–36% of the water they absorbed in 24 h was released at RH > 93%. Retardation of self-desiccation and reduction of early autogenous shrinkage of mortar were observed with saturated RFAs. RFAs with finer particle sizes and higher water absorption capacities gave greater reductions in autogenous shrinkages at the first three days, which could be attributed to the RFA pore structure. Internal curing with the RFA was observed clearly in a mixture with a high aggregate content.

Use of supplementary aggregates in mortars produced using a novel lime-drying technique

Formulated lime mortars suitable for long-term storage in silos or bags can be produced by adding quicklime to wet, as-received quarried sand. However, sands with high water content may require the addition of more quicklime that would alter the mortar proportioning. This work investigates the possibility to replace part of the lime-dried sand with dry, crushed, mixed glass cullet and calcium carbonate aggregate to allow greater control over mortar formulations. It is shown that the use of glass yields a similar or slightly weaker product, depending on curing regime, than the control while calcium carbonate generates the strongest mortar.

Recycling of Foundry Sand Wastes in Self-Compacting Mortars: Use as Cementitious Materials and Fine Aggregates

Abstract This work aims to study the possibility recycling of foundry sand wastes (FSW) as a cementations additive and fine aggregate in self-compacting mortars (SCM). For this, an experimental study was carried out to evaluate physical and mechanical properties of SCM. Firstly, sand is substituted by the foundry sand waste at dosages (0%, 10%, 30%, and 50%) by weight of the sand. Secondly cement is partially substituted by crushed foundry sand waste at different ratio (0%, 10%, 20%, 30%, and 50%) by weight of cement. The obtained results show that up to 50%, (FSW) can be used as fine aggregate for mortars without affecting the essential proprieties of mortar. However, beyond 50% of sand substitution, mortars lose their fluidity. The compressive strength of the mortars with 50% of cement substitution decreased compared to the control mortar. Value of the highest compressive strength recorded at 28 days, is of the order of 50 MPa for the mortar with 20% of cement substitution. Also, stress-strain curve show an acceptable mechanical behavior of FSW-based mortar at 50% of sand substitution.

UTILIZATION OF CRUMB RUBBER AS AGGREGATE IN HIGH CALCIUM FLY ASH GEOPOLYMER MORTARS

This research was carried out to find out the possibility of utilizing tire crumb rubber waste as fine aggregate in fly ash-based geopolymer mortars (GPMs). The effect of replacement of river sand with crumb rubber at the levels of 0, 25, 50, 75, and 100% by volume on the geopolymer mortar properties including workability, dry density, compressive strength, flexural strength, thermal conductivity, ultrasonic pulse velocity (UPV), water absorption, and porosity were studied. The results were compared to those of the Portland cement-based mortars (PCMs). The test results demonstrated that the higher crumb rubber content resulted in the less dense matrix of mortar. However, GPMs with crumb rubber resulted in a significant improvement in flexural strength. The average ratio of flexural to compressive strengths of GPMs was 25% compared to 15% of PCMs. Also, the lower dry density and thermal conductivity of GPMs indicated better insulating properties than those of PCMs.

Investigating Various Factors Affecting the Long-Term Compressive Strength of Heat-Cured Fly Ash Geopolymer Concrete and the Use of Orthogonal Experimental Design Method

This work quantified the hierarchy of the influence of three common mixture design parameters on the compressive strength and the rate of strength increase over the long term of low-calcium fly ash geopolymer concrete (FAGC) through designing 16 mixtures by the orthogonal experimental design (OED) method. The parameters used in the study were liquid to fly ash (L/FA) ratio, sodium hydroxide concentration (SHC) and sodium silicate solution to sodium hydroxide solution (SS/SH) ratio. The L/FA ratio showed little effect on compressive strength when it was varied from 0.40 to 0.52. SHC showed the greatest influence on compressive strength with little impact on the rate of strength increase after the initial heat curing. Even though the SS/SH ratio showed a small effect on the initial compressive strength, it had a considerable influence on the rate of strength increase over the long term. It was found that the compressive strength at 480 days was positively related to the Na2O/SiO2 molar ratio when it was varied from 0.49 to 0.80 and the Si/Al molar ratio was increased up to 1.87. Analysis of the failure types of specimens demonstrated that compressive strength of FAGC was associated with the strength of the mortar–aggregate interface zone (MAIZ).