Properties Of Fresh Mortar Research Articles

Enhancing mechanical properties of 3D printed cementitious composites utilizing hybrid recycled PP and PET fibers

The integration of fibers offers a means to fabricate intricate, load-bearing architectural configurations that were previously challenging to achieve with conventional 3D printed concrete. This study investigates the incorporation of recycled plastic fibers (RPFs) derived from polyethylene terephthalate (PET) and polypropylene (PP) to enhance the mechanical properties of 3D printed cementitious composites (3DPCC). Two distinct fiber lengths, 6 mm and 12 mm, were utilized for each fiber type across various fiber volume fractions ranging from 0.3 % to 1.5 % of the mortar volume. The results show that the optimal volume fractions are 1 % for 6 mm fibers and 0.7 % for 12 mm fibers. The findings indicate that hybrid combinations of PP and PET fibers achieve superior mechanical characteristics compared to the use of individual fiber types. The assessment of fresh mortar properties included fluidity, buildability, and extrudability, along with the evaluation of compressive and flexural strength as indicators of mechanical properties. Additionally, this study assessed the influence of a hybrid fiber mix comprising 40 % PP and 60 % PET of the 6 mm fiber length volume fraction, which exhibited the highest average compressive (20.6 %) and flexural strength (44.9 %) in the Z direction for 3DPCC, surpassing the performance of individual PP and PET fibers at the same volume fraction across all the volume ratios. When 12 mm fibers were utilized, the compressive and flexural strengths in the Z direction increased by 20.8 % and 46.7 %, respectively, for a mix of 20 % PP and 80 % PET of the total volume fraction. Concerning buildability, the control sample achieved a maximum of 29 layers, whereas the addition of 1.5 % PET fibers at 12 mm enabled the structure to reach 48 layers.

Evaluation of basalt fibers and nanoclays to enhance extrudability and buildability of 3D-printing mortars

A study of the rheological and fresh mechanical properties of fly ash-cement 3D printing (3DP) mortars with six types of nanoclays (NC) as rheology modifiers, two sepiolites, three attapulgites and one bentonite, and reinforced with short basalt fibers (BF) was carried out. Fresh mortar properties were evaluated with a flow table test (FTT), cylindrical slump test (CST) and cone-penetration test (CPT) on samples left at rest and stirred before testing. Squeeze test (SQT) was carried out on samples cast-in-the-mold and 3D printed to compare the effects of 3DP on the fresh mechanical behavior. Extrudability was assessed with an electrical barrel extrusion device. NC and BF enhanced mortar cohesion by preventing water drainage and improving material extrudability. NC increased shear yield stress (τ0) over time on samples left at rest, enhancing reversible thixotropy. Besides, NC required larger amounts of superplasticizer, increasing open time windows. Among NC, Sepiolite in powder form showed the best fresh mechanical performance on 3DP samples. BF enhanced extrudability due to the bridging effect but also shows mechanical synergies with some NC. 3DP samples showed lower compressive yield stress and Young modulus evolution over time (σ˙ and Ė) than cast-in-the-mold samples, due to their layered structure.

The influence of selected grain size fractions of coal fly ash on properties of clay-cement mortars used for the flood levees construction

This study examines the influence of different grain size fractions of coal fly ash on the properties of clay-cement mortars used in flood levee construction. Dry aerodynamic separation and mesh sieving were used to obtain ultrafine, fine, and medium fractions of high-calcium and silica fly ash. The experimental results reveal that the rheological properties of fresh mortars are significantly influenced by these fractions. High-calcium fly ash mortars exhibit high reactivity and rapid increase in viscosity, with finer fractions showing the highest reactivity. Silica ashes show increased reactivity in the later stages of suspension hardening. Their spherical shape contributes to reducing internal friction during flow in initial technological operations. Furthermore, the compressive strength of hardened mortars improves as the particle size decreases for both ashes, resulting in a dense and uniform microstructure. The separation and fractionation of fly ashes contribute to the obtaining of fractions that influence the parameters of clay-cement suspension application on different scales. The results show the potential benefits of ash separation, which can bring advantages in terms of economic viability, engineering performance, and ecological sustainability.

EFFECTS OF ZEOLITE INCORPORATION AND INERT FILLERS ON THE CURING OF CEMENT MORTARS

One of the main approaches to reducing the environmental impacts of the construction industry is the use of mineral additives reducing the use of cement in mortars and concretes for construction. The objects of this research are different cement composites with high content of inert mineral fillers (marble and quartz sand), the influence of zeolite incorporation on the microstructure, and low water-cement ratio, obtained after the hydration of white portland cement.In this study, the evolution of the curing processes and the crystal formation during up to 120 days of water-curing are investigated. Moreover, the effects of replacing up to 10 wt. % of white cement with natural zeolite are studied. Attention was focused on the general microstructural development during curing with special attention on the evolution and morphology of pore space and the observed calcium silicate hydrates (C–S–H), portlandite, and carbonate-containing phases.The phase composition (newly formed phases as well as the formation of C-S-H gel) is defined by using powder X-Ray diffraction and SEM. The experimental data shows that the cement composites with the inert marble filler as an additive lead to the creation of carbo-aluminates. The incorporation of up to 10 percent of clinoptilolite in concrete mixtures by mass of the total cementitious components is more efficient when used in lower strength mixes. A significant reduction in the workability of the fresh mortars is not observed, but the high surface area of zeolite reduces bleeding and accelerates setting without any strong effects on the other physical and technological properties of fresh mortars.

The use of air entraining/plasticizing admixtures in cement-lime masonry mortars: Effects on fresh and hardened mortar properties

Modern day masonry mortars rely on more than just standard constituents, which by definition include binder, aggregates and water. Due to different requirements imposed onto various types of masonry construction, ready mix mortar manufacturers and even masons and labourers on construction sites add certain additives to their mortar formulations. In this study, one standardized admixture is studied – an air entrainer/plasticizer (EN 934-3), coming in two forms – liquid and powder. It is applied to increase the air content and plasticity of cement-lime masonry mortar, formulated in volumetric proportions of 1:1:6 for cement, lime and aggregates. The dosage of admixtures is gradually increased starting with the manufacturer’s recommendations until the excessive air entrainment is achieved in order to determine the optimal dosage. Fresh mortar properties, including consistency, air content and bulk density are used to assess the enhancement of mortar influenced by the addition of the admixture, whereas compressive and flexural testing is performed at 7 and 28 days to monitor the disadvantages brought by reducing density. The results of this study reveal that the efficacy of a liquid admixture is better than that of a powdered air entrainer/plasticizer, albeit it being more difficult to use accurately. In both cases, higher dosage than manufacturer’s recommendations was required to reach satisfactory improvement of the fresh mortar structure, which resulted in a mixing water reduction, increased air content and reduced bulk density. That subsequently influenced the decreased strength, although optimally formulated mortars adhered to their strength class requirements.

Adhesive and rheological properties of fresh mortar with manufactured sand as replacement of river sand

This paper investigates the adhesive properties of fresh mortar with manufactured sand (Msand) as replacement of river sand (Rsand). Adhesive properties were evaluated by normal force evolution curves from the tack test. Both static and dynamic yield stress were measured to elaborate the influence of Msand replacing Rsand on the adhesive properties. Results indicate that Msand increases the adhesive force, critical displacement, stiffness, and adhesive failure energy whereas shortens the debonding duration. Replacement of Rsand by Msand gradually promotes the transition of failure mode from cohesive rupture to adhesive rupture. The adhesive force of mixtures showing cohesive rupture is highly related to their static yield stress values.

Rheological Properties of Carbon Nanotube Infused Cementitious Composites with Various Amounts of CNT

The addition of carbon nanotubes (CNTs), which are hydrophobic materials, significantly influences the rheology of cementitious materials but requires important mix modifications in order to provide proper flowability for further use. This paper investigates the influence of various dosages of carbon nanotubes (0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.5 wt.%, and 1 wt.%) on the flowability, rheological parameters, air content, and volume density of cement mortars. The results show an increase in the yield stress parameter with an increment in CNT dosage up to the threshold of 0.5 wt.% for mixes with an increased amount of cement. For standard proportions, it was on a stable level for all mixes except for 0.2 wt.%. The plastic viscosity parameter also increased with the CNT dosage; mixes with standard proportions of components were not higher than the reference, and mixes with an increased amount of cement were lower than the reference for dosages up to 0.5 wt.% of CNT. The addition of a superplasticizer and modifications of the ratio of the components were employed to achieve proper flowability and measure the rheological parameters. The presented results show that regardless of the negative influence of carbon nanotubes on the properties of fresh mortar, it is possible to achieve a stable flow and workability using simple modifications of the composition.

Bentonite in two-component grout applications

Two-component grout is a cement-based material, currently the most used technology for backfilling in tunnelling applications. Despite its intensive, knowledge on this material is quite limited, especially as concern the role of ingredients and their effect on the properties of fresh mortar and hardened grout. In this work, an accurate and innovative test campaign focused on the role of the bentonite was performed. Three different bentonites were used. The activation of the bentonite and its effect on both mortar stability and grout strength was investigated with the purpose to recognise the bentonite parameters useful to select, at the design stage, the best bentonite according to the designers’ requirements. Swell index and Atterberg’s liquid limit were recognised as useful parameters for predicting results in terms of suitable bleeding and surface compression strength.

Effects of Silica Fume Addition on Properties of Fresh Mortar

In recent years, concrete structures have tended to be taller and larger than before. With that trend, concrete as a material has diversified, and various kinds have been developed to meet differing quality requirements. In particular, the need for high-strength concrete is increasing. In general, high-strength concrete has a low water-binder ratio, so its workability is inferior to general concrete. Including admixtures such as silica fume is one way to remedy this problem. Previous studies have discussed the quality and hardening characteristics achievable using silica fume. Nevertheless, expected increasing demand for high-strength concrete dictates the need to understand not only its properties when fresh, but also to have an accurate picture of its vibration compaction properties on construction sites. In this study, the effect of adding silica fume on the workability of mortar was investigated by evaluating its fresh properties, plastic viscosity, and vibration propagation characteristics. Changes to mortar’s fresh properties due to pressure were also investigated to clarify its behavior in pumping environments. The study confirmed that the addition of silica fume decreases plastic viscosity and increases vibration propagation characteristics, and that increased plastic viscosity due to pressurization can be reduced.

Influence of brick industrial rice husk ash on properties of ambient cured geopolymer mortar matrix

Abstract Sustainability plays an important role by utilising hazardous waste into green technology. This study includes various Class F Fly Ash (CFFA) and Brick Industrial Rice Husk Ash (BIRHA) proportions with alkalis to make matrix of geopolymer mortar under the curing temperature of 40 °C ± 2 °C till the testing ages. The effect of BIRHA upto 50% with NaOH concentration of 10 M was assessed with sodium based alkali ratio of 2.5. Morphology and mineralogy was determined using FESEM, XRD and Wet chemical analysis for the base binders. Fresh mortar properties like flowability and unit weight was determined and hardened properties like compressive strength was determined for both ambient curing upto 56 days and higher temperature effect at 56 days for all mix proportions. Research leads to the findings that the specimens made of 10 M NaOH and 30% BIRHA exhibits higher compressive strength at 56 days in ambient temperature beyond which it decreases. The mix made with 90% CFFA and 10% BIRHA is found to be optimum for fire load applications. Hence from the present investigation it can be revealed that the BIRHA is a promising solid waste material for geopolymer application.

Properties of mortar with fine eggshell powder as partial cement replacement

Solid waste management is one the leading problems faced by developing nations. In Malaysia, the average per capita generation of municipal waste is about 0.85 kg per person per day, and this number is only expected to raise as the population grows and nation becomes more industrialized. One of the wastes is eggshell waste, as Malaysians have among the largest egg consumption in the world. This paper presents the properties of cement mortar with fine eggshell powder as partial replacement of cement. Type-N mortar was prepared with cement: sand: water ratio of 1: 2.75: 0.60 and the percentages of cement replacement tested are 2.5%, 5%, 7.5% and 10% by weight of cement. Flow table test was conducted to access the fresh properties of mortar, while compressive test and flexural test were carried out to determine the mechanical properties. Water absorption and acid resistance eggshell mortar were also studied. From the result, eggshell mortar has similar flow consistency with the control. 5% eggshell produces mortar with optimal compressive and flexural strength and the water absorption of eggshell mortar is lower compared to control. However, eggshell mortar loses more weight when subjected to acid attack.

Optimizing manufactured sand content in mortars and its influence on fresh and hardened state

The shape and roughness of aggregates play a predominant role in the properties of cement mixes. Due to that, some regulations limit the content of manufacture fine aggregate at 30% of the total of fine aggregate in concrete. However, few design methods consider the shape and roughness surface of aggregates in the mix proportioning. This study presents an optimization method to increase the percentage of manufactured fine aggregates to be used, based on the void volume of the aggregates and their correlation with the fresh properties of mortars. To achieve that, the characteristics of the fresh and hard state were evaluated in order to carry out a comprehensive analysis on the influence of the method on the performance of mortars. From the results emerges that it is possible to maximize the content of manufactured aggregates without detrimental effects on compressive strength.

Influence of polypropylene microfibre (PPMF) dispersion procedure on fresh and hardened rendering mortar properties

Abstract This study was carried out to evaluate the influence of a polypropylene microfibre (PPMF) dispersion procedure on fresh and hardened state properties of rendering mortars. Specimens prepared with two different PPMF dispersion procedures were evaluated comparatively with reference specimens prepared without adding PPMF. Changes in the fresh properties were monitored using flow table, squeeze flow, and air-entrainment tests. The hardened state was characterized by capillary water absorption, air-permeability, dynamic elastic modulus (E), tensile strength according to the Brazilian test, and porosity by the Archimedes immersion method. Results show that the fresh mortar properties were not affected by dispersion procedure and all hardened mortar properties were statistically similar, except for the dimensional variation of the specimens. The study also shows that adding polypropylene microfibres in a dispersed form was more effective in terms of controlling total drying shrinkage than directly adding fibres to the cementitious matrix (as recommended by the manufacturer) or the reference mortar.

Effect of high temperature on the performance of self-compacting mortars produced with calcined kaolin and metakaolin

The effects of high temperature up to 900 °C on the mechanical characteristics of self-compacting mortars (SCMs) containing different proportions of calcined kaolin (CK) and metakaolin (MK) were investigated in this study. The percentages of CK and MK that replace cement in this work were 0%, 5%, 10%, 15% and 20% by weight. The mechanical performance was assessed from compressive strength and flexural strength on the specimens of 40x40x160 mm size exposed 3, 28 and 90 day- water curing at ambient temperature and on the 28 day-specimens at high temperature while the durability of 28 day-SCMs samples was assessed from porosity, water absorption, sorptivity and density tests on water cured specimens of 50x50x50 mm size. The fresh properties of mortars were researched by slump and V-funnel tests. The rheological properties of fresh mortars were investigated by conducting the viscosity test. The outcomes of the study reveal that workability of mixtures was decreased with increasing proportion of MK replacement. The results also revealed that at 28 and 90 days of curing ages, the specimens of SCMs with MK15 gained the highest strength of 65.40 MPa and 79.01 MPa for about 10.13% and 15.46% more than the control specimens at the respective ages. Results illustrated that while the temperature rises, the compressive strength reduction of CK blended SCMs samples decreases with increasing replacement ratio of CK. A remarkable reduction in the total water absorption and porosity values of MK blended SCMs samples was observed. The highest density values at all SCMs mixes were observed for MK5 blended samples about 8.44% increase. 15% replacement level of MK gives the lowest sorptivity values.

Properties of mortars based on β-belite-metakaolinite-hydrated lime binder system

A novel β-belite cement was prepared, characterized (by chemical and phase composition, particle size distribution, bulk density, specific surface area) and incorporated into mortars based on a mixed binder β-belite-metakaolinite-hydrated lime with different contents of β-belite cement (0, 20, 40, 60, 80 and 100 wt.%). The metakaoline:hydrated lime weight ratio of 1:1 and binder:sand weight ratio of 1:3 were observed in all mortars. The effect of the β-belite cement fraction on the properties of fresh mortars (water:binder ratio needed to achieve the required mortars consistency and initial setting time), on the phase composition (X-Ray diffraction phase analysis and thermogravimetric analyses) and on the structural properties of mortars (compressive strength, flexural strength, bulk density, water absorption, water absorption coefficient, shrinkage) over 1 year of curing was investigated. Freeze and thaw resistance of the mortars after 1 year of curing was also evaluated. Partial replacement of metakaolinite-hydrated lime binder with β-belite cement affected all investigated mortar properties. Significant improvements in mechanical properties and resistance to freezing and thawing cycles were the main advantages.

Effect of Adding Stone Sludge as Sand Replacement on Fresh Properties of Mortar

Shortage of river sand and disposal of stone sludge are the problem of the construction and stone product industries, respectively. Utilization of stone sludge in mortar is one of the feasible strategies to solve these two problems. To study the effects of addition of stone sludge on the performance of mortar, 20 mixes of stone sludge powder mortar with various water/cement ratios and various stone sludge powder contents were produced for flowability measurement. To further study the governing mechanism of flowability and the packing densities of the solid proportions of the 20 mortar mixes were measured. Based on the packing density results, the average film thickness (AFT) of the 20 mortar mixes were calculated for flowability indication. Results proved that addition of stone sludge powder as sand replacement would decrease the flowability. The flowability was mainly governed by the AFT.

A systematic study on EN-998-2 premixed mortars modified with graphene-based materials

Graphite nano-platelets (GNPs) and graphene oxide (GO) modify cementitious materials from the nano- to the macroscale, resulting in enhanced mechanical properties, durability and, eventually, physical multi-functionality. A systematic study on EN 998-2 premixed mortars modified with GNPs or GO is reported. Rheological properties of fresh mortars were investigated in terms of shear stress (or apparent viscosity) versus shear rate. Mortars were casted in bars and hardened for 28 or 14 days. Density, microstructure, compressive and flexural strength of hardened samples were evaluated and compared.

Influence of the Variability of Calcareous Fly Ash Properties on Rheological Properties of Fresh Mortar with Its Addition

One of the main by-products of brown coal burning is calcareous fly ash (CFA). Apart from other applications, it is used as a main component of cement, or as an active mineral additive to concrete. The present study involves the impact of the raw and processed calcareous fly ash (CFA) on the changes of rheological properties of mortars. The said impact was determined by using the coefficient of variation (CV) given in percentage. CFA samples collected from various sources were subjected to testing. The samples were collected from two electrofilters of blocks with boilers of different combustion parameters and from the retention tanks of the CFA sales department (CFA T) in which CFAs from various boilers are mixed. It has been demonstrated that the degree of the impact of CFA addition on the rheological properties of mortars depends on the source of this addition and on bulk density. The present work demonstrates the negative impact of raw CFA on mortar workability, and hence it is questionable to support its use in concrete technology.

Fresh and hardened properties of cement mortars using marble sludge fines and cement sludge fines

The construction sector could provide solutions for the safe utilization of industrial by-products as construction materials, if proper characterization and control of the materials properties is undertaken. Under this consideration, fines produced from marble cutting and fines produced from concrete truck washing were investigated as fine material for use in cement mortars. Both these by-products are produced in large amounts in the form of sludge. Marble Sludge Fines (MSF) and Cement Sludge Fines (CSF) were characterized in terms of fineness, density, chemical analysis and suitability for use with cement. Mortars with variable rate (10%, 20% and 30%) of cement substitution with MSF or CSF were tested and compared to a reference cement mortar in respect to their fresh and hardened properties. Packing ability and viscosity were measured in fresh mortars, while strength development, water absorption and porosity were measured in hardened mortars. The results confirm the suitability of both as filler material; although MSF performed better regarding fresh mortar properties and CSF showed better results regarding strength development.

Production of concrete compatible biogranules for self-healing concrete applications

Recently, cost-efficient nitrate reducing biogranules were suggested as an alternative to axenic microbial cultures for development of microbial self-healing concrete. In a marine environment, biogranule containing microbial self-healing concrete showed simultaneous self-healing of cracks and immunisation against rebar corrosion. Yet, information about the production strategy of these biogranules and their compatibility with a mortar matrix is limited. This study presents the production of biogranules and their compatibility with mortar specimens when incorporated at dosages between 0.36% to 4.30% w/w cement (0.25% to 3% of bacteria w/w cement). In-house produced biogranules composed of 70% bacteria and 30% of minerals w/w of biogranule were used for the compatibility tests. In test mortars, calcium formate (CF) and calcium nitrate (CN) were used as regular nutrient admixtures, and nutrient content was set identical in every batch. Up to 2.9% incorporation, biogranules had no significant influence on the fresh properties of mortar. More than 2.9% incorporation caused poor workability and a 26% decrease in 3-Day compressive strength of biomortar specimens. Overall, the biogranules produced are compatible with a cementitious matrix up to 2.9% w/w cement, and even up to 3.6% if early age strength is not essential, which makes biogranules one of the most compatible microbial healing agents among the suggested agents in the literature.