Mortar Flow Research Articles

The effect of powder type on the setting time and self compactability of mortar

In this paper, fly ash and metakaolin as pozzolan while limestone powder and kaolin as filler material were used at replacement levels of 5%, 10%, 15%, and 20% by weight of cement and sand, respectively. The effects of these powders on the fresh property of mortar mixes were studied and reported. Superplasticizer dosages were determined from flow test on cement paste and mortar with different powder content. A total of 33 mixes were prepared, mixed, and tested. The mini slump cone and mini V-funnel box tests were used to assess the flowability of the fresh mortar. In addition, the effect of mineral admixture on setting time of the mixes was also evaluated. In this study, the optimum dosage of superplasticizer was determined based on the desired flowability for self compactability. Superplasticizer at higher dosages than optimum reduced the stability due to bleeding. The results confirmed the role of the mineral powders in determining the desired stability and the flowability of mortar mixes which is crucial for self compacting concrete.

Design of the Dry-Mixed Mortar Truck in Avoiding Segregation

The way of dry-mixed mortar air-sliding has many advantages，such as improving transport efficiency, ensuring cement quality. But, dry-mixed mortar air-sliding may occur segregate, this phenomenon serious break the original ratio of cement, risking quality of cement[2]. This article suggested a new model of discharge opening with multi-holes, this model can allow dry-mixed mortar flow out at different height, and control the rate of flux in each port to keep mortar equally, this model eliminated the non uniforms caused by different height, eliminated the affection of segregate, ensure the quality of the cement.

바이오숯을 함유한 모르타르의 역학적 특성

Bio-char, obtained from biomass as a by-product of the pyrolysis process, is used successfully as a soil amendment and carbon sequester in this limited study. Recent and active research from literatures has extended the application of bio-char in the industry to promote sustainability and help mitigate the negative environmental impacts caused by carbon emissions. This study aims to investigate the feasibility of high-carbon bio-char as a carbon sequester and/or admixture in mortar and concrete to improve the sustainability of concrete. This paper presents the experimental results of an initial attempt to develop a cement admixture using bio-char. In particular, the effects of the water retention capacity of bio-char in concrete are investigated. The chemical and mechanical properties (e.g., the chemical components, microstructure, concrete weight loss, compressive strength and mortar flow) are examined using sample mortar mixes with varying replacement rates of cement that contains hardwood bio-char. The experimental results also are compared with mortar mixes that contain fly ash as the cement substitute.

Field-oriented test methods to evaluate structural build-up at rest of flowable mortar and concrete

Thixotropy of flowable mortar and concrete is an important property that affects stability and form pressure characteristics. The increase in thixotropy can reduce lateral pressure on formwork systems. On the other hand, low thixotropy or a continuous casting is required to eliminate the formation of weak interface between lifts in multilayer casting. Thixotropy can be assessed by determining the rate of structural build-up at rest, which necessitates the use of simple and robust test methods to be quantified. Five field-oriented test methods that can be used for the determination of structural build-up at rest of mortar and concrete are proposed in this paper in an attempt to select a reliable field-oriented test. This includes the inclined plane (IP), portable vane (PV), undisturbed slump spread (USS), cone penetration (CP), and K-slump test methods. The repeatability of these test methods was determined four times using two concrete-equivalent mortars and two self-consolidating concretes (SCC) of different thixotropy levels. The IP, PV, and USS tests showed relative error (RE) values of 0.5–37 %. The CP test was successfully used to determine structural build-up of mortar; however, it was difficult to assess the thixotropy of concrete. The K-slump test exhibited a RE, less than 12 % for SCC mixtures with low thixotropy, but up to 76 % for highly thixotropic SCC. Good correlations were established among the various structural build-up indices determined from the proposed test methods and those determined by rheometric tests using various concrete.

The Properties of Mortar Mixtures Blended with Natural, Crushed, and Recycled Fine Aggregates for Building Construction Materials

In this research, the possible applicability of mixture blended with natural, crushed, and recycled fine aggregate are discussed. The fresh and hardened properties of mortar using blended fine aggregates are monitored depending on various blending ratio of fine aggregates. Newly developed ternary diagram was also utilized for better interpretation of the data. It was found that air content increased and unit weight decreased as recycled fine aggregate content increased. With moisture type processing of recycled fine aggregate, the mortar flow was not negatively affected by increase in the recycled fine aggregate content. The ternary diagram is found to be an effective graphical presentation tool that can be used for the quality evaluation of mortar using blended fine aggregate.

Properties of High-Strength Flowable Mortar Reinforced with Palm Fibers

This study was conducted to determine some physical and mechanical properties of high-strength flowable mortar reinforced with different percentages of palm fiber (0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, and 1.6% as volumetric fractions). The density, compressive strength, flexural strength, and toughness index were tested to determine the mechanical properties of this mortar. Test results illustrate that the inclusion of this fiber reduces the density of mortar. The use of 0.6% of palm fiber increases the compressive strength and flexural strength by about 15.1%, and 16%, respectively; besides, the toughness index (I5) of the high-strength flowable mortar has been significantly enhanced by the use of 1% and more of palm fiber.

Effect of size and type of fine aggregates on flowability of mortar

The present study investigated how the aggregate characteristics namely individual size, grade and type affects flowability of mortar mixes. Two types, river sand and crusher dust four single sizes namely 1.18 mm, 0.600 mm, 0.300 mm, 0.150 mm and for single gradation of each fine aggregate were considered in the present research work. In total, 103 mortar batches was made with three different sand to cement ratios [s/c] and two different water to cement ratios [w/c] to find out the flowability of mortar and tested using standard flow table. Out of 103 mortar batches, 52 were with river sand and 51 were with crusher dust. Tests were performed as per ASTM 109 standards. S/c ratio varied from 1 to 3 with an increment of one and w/c ratio was chosen in such a way that all the mixes to give measurable flow. The influence of particle shape and surface texture of aggregate were characterized with an angularity test based on ASTM C1252 in terms of percent of air voids in a loosely compacted fine aggregate. The results indicate that the size of aggregate and uncompacted void content have greater impact flowability of mortar. Mortar made with river sand has got better flowability than that of mortar made with crusher dust due to its higher degree of irregularities. Mortar with higher aggregate content has low percentage of spread compared to mortar with low aggregate content. Similarly, graded aggregate has lesser percentage of spread due to its proper packing compared to single sized aggregates.

High-strength flowable mortar reinforced by steel fiber

High-strength flowable mortar reinforced by steel fiberAn experimental study was conducted on High-Strength Flowable Mortar (HSFM) reinforced at different percentages of steel fiber (0, 0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75 and 2.0% as volumetric fractions) to determine the density, compressive strength, static modulus of elasticity and flexural strength. The load-deflection curves under a static flexural load were established, and the flexural toughness indices were obtained in accordance with ASTM C1018. The results indicate that by increasing the fiber content up to 1.75%, the flexural strength and toughness indices are increased. The density, compressive strength and static modulus of elasticity also increased using steel fiber.

Flow, water absorption, and mechanical characteristics of normal- and high-strength mortar incorporating fine bottom ash aggregates

This study focused on investigating the flow, water absorption, and mechanical characteristics of normal- and high-strength mortar incorporating fine bottom ash (FBA) aggregates. It was also intended to examine the effects of FBA aggregates on the performance of the mortar. The effects of FBA aggregates on the density, compressive strength, dynamic modulus of elasticity and flow characteristics of the mortar were investigated, and the porosity and water capillary absorption of the mortar were measured to evaluate the properties of moisture transport, which may affect the durability of the mortar. It was found from the study that the mortar flow was increased by 10–20% with the replacement by FBA aggregates. The specific compressive strength of the mortar with FBA aggregates was shown to be 5–11% higher than that of the mortar with normal fine aggregates. It was also shown that water would be absorbed more slowly into the mortar with FBA aggregates when the porosity was the same as that of the mortar with normal aggregates.

Experimental Research on Rheological Properties of Cemented Mortar in Tail Void Grouting of Shield Tunnel

Grout flow pattern and rheological parameters determine grouting pressure transfer process in annular tail void and filling rate for shield tail void. However, cemented mortar is a mixture of cement, fly ash, sand, bentonite and water, which lead to grout rheological properties and rheological parameters are difficultly determined. Based on orthogonal experimental design method, grout rheological properties were tested by rotational viscometer. Utilizing variance and poly-nonlinear regression analysis, the qualitative and quantitative relationships between mix ratios and rheological parameters were obtained respectively. It is shown that cemented mortar flow pattern commonly agree with Bingham fluid type, and plastic viscosity varies between 1 and 4Pa•s, and shear yield stress varies between 10 to 40Pa respectively. Water-binder ratio and bentonite-water ratio are key influencing factors for grout rheological parameters. With the water-binder ratio increasing and bentonite-water ratio decreasing, plastic viscosity and shear yield stress present reducing tendency.

Composition, strength and workability of alkali-activated metakaolin based mortars

This study has investigated the joint effect of several factors on the workability and mechanical strength of alkali-activated metakaolin based mortars. The factors analysed through a laboratory experiment of 432 specimens, pertaining to 48 different mortar mixes were, sodium hydroxide concentration (10 M, 12 M, 14 M, 16 M), the superplasticizer content (1%, 2%, 3%) and the percentage substitution of metakaolin by calcium hydroxide in the mixture (5%, 10%). The results show that the workability decreases with the concentration of sodium hydroxide and increases with the amount of calcium hydroxide and superplasticizer. The results also show that the use of 3% of superplasticizer, combined with a calcium hydroxide content of 10%, allows improving the mortar flow from less than 50% to over 90%, while maintaining a high compressive and flexural strength.

New Approach to Calibrate the Mortar Flow Table

The flow table is a standardized test that is widely used to qualify a mortar for compressive strength and air content. The flow table is also the only standard test to quantify the workability of a mortar. Therefore, the calibration of this device is paramount, and it is done today by preparing a reference material consisting of a mixture of silica powder and oil. The two materials are mixed; tests are performed with the use of the reference flow table located in the Cement and Concrete Reference Laboratory. This flow table is identical to commercial versions currently used, and the values obtained with this flow table are considered the reference values for calibrating flow tables in the United States. This is an empirical procedure and relies heavily on one device that could break or generate results that can drift over time. This study reviewed the manufacturing process of the reference material, provided historical data, and proposed a more scientifically based approach to develop an improved reference material.

Flowability in crushed sand mortar

The present experimental study explored the relationship between mortar flowability and the voids content in crushed sand to determine the effect of grain shape and surface texture as well as dust content on the behaviour of fresh mortar. The findings revealed a close correlation between voids content and the volume of paste needed for mortar to begin to flow as a continuous material, mortar flowability and the water content needed to attain a given flowability. The comparison of the empirical findings to the results obtained with the Larrard (1, 2) model provided further information on the effect of sand grain morphology on fresh mortars.

Flowable high-strength system as repair material

The use of steel fibres in concrete or mortar is known for its potential to enhance the flexural toughness, the energy dissipation and the impact resistance for many structural applications, especially in building repairs and other civil engineering works. The use of steel fibres in flowable mortar provides a great advantage in arresting cracks and enhancing the flexural rigidity of the composite material. Hence, this experimental investigation was performed to provide a clear indication and understanding of the behaviour and structural performance in engineering construction. The experimental tests conducted were: density, compressive strength, splitting tensile strength, flexural strength and toughness indices tests. These tests are required to show that the best performance of high-strength flowable mortar or high-strength flowing concrete could be fulfilled by using steel fibres and the optimal percentages of silica fume as partial replacement of cement. The conductivity of the repair material was evaluated by adoption of some combined systems of repair materials with concrete to determine the bond action of this repair material (flowable high-strength system). The results indicate that the high-strength flowing concrete has an excellent performance in terms of compressive strength for the repaired system. On the other hand, the high-strength flowable mortar improves significantly the tensile strength of the repaired system.

High-Strength Geopolymer Using Fine High-Calcium Fly Ash

In this paper, the synthesis of high-strength geopolymer using fine high-calcium fly ash was studied. The effect of fineness of fly ash on the setting time of geopolymer paste, workability, strength development, and drying shrinkage of geopolymer mortars made from classified fine high-calcium fly ash was investigated. Air-classified fly ash with three different finenesses—coarse original fly ash (CFA), medium-fineness fly ash (MFA), and fine fly ash (FFA)—from the Mae Moh Power Station was used for this study. The heat-cured geopolymers were activated with sodium hydroxide (NaOH) and sodium silicate. A small amount of water was incorporated for workability. The results indicate that the setting time of paste decreases with an increase in fly-ash fineness. The flow, strength, and drying-shrinkage characteristics of mortars were improved using fine fly ash. Geopolymer mortars with high 28-day compressive strength of 86.0 MPa were obtained.

Sustainable masonry mortar for brick joint and plaster in the UK

Blended mixtures of ground granulated blastfurnace slag and Portland cement were used in making sustainable masonry mortars suitable for brick joints and for plastering, with Portland cement mortar as control. The testing programme included the determination of a relationship between the mortar flow value and mortar water demand for a wide range of mix compositions. The mortar tensile strength is not a very critical property due to the fact that brickwork mortar is not usually under tension when in service; however, this parameter was determined in the laboratory using a standard briquet towing/testing machine. Chemical durability of the control and blended mortar in aggressive sulfate-bearing exposure conditions was investigated. The relationship between compressive strength of the mortar cured in water and in sodium sulfate solution at room temperature (20 ± 2°C) for from 3 to 120 days was established. The results demonstrated that after a prolonged period of exposure, significant strength and weight loss in the control mortar was observed. This phenomenon is explained, due to calcium hydroxide production as a consequence of Portland cement hydration, change in mortar morphology, inhibition of reaction species and the final disruption of the mortar matrix, resulting in loss of strength and weight at late age. The results obtained suggest that ground granulated blastfurnace slag can be incorporated into Portland cement for the development of sustainable and durable mortars in the UK.

Influence of Nano-SiO2 Addition on Microstructure and Mechanical Properties of Cement Mortars for Ferrocement

Because of their unique physical and chemical properties, nanoparticles have been gaining increasing attention and have been used in many fields to fabricate new materials with novel functions. If nanoparticles are integrated with cement-based building materials, the new materials might possess some outstanding properties. Ferrocement is a type of thin-wall reinforced concrete commonly constructed of hydraulic cement mortar reinforced with closely spaced layers of continuous and relatively small-sized wire mesh. The low level of technical skill required to make ferrocement and the ready availability of its materials make ferrocement suitable for a wide variety of applications. This study investigates the mechanical properties (compressive and flexural strengths) and microstructural properties (as determined by scanning electron microscopy) of the interfacial transition zone between cement pastes and aggregates of mortars applicable for the casting of thin ferrocement elements combining with nanosilica. Study parameters include the ratio of nanosilica to cement in ordinary portland cement mortar mixtures (including 1%, 2%, and 3%) and the water-to-binder ratio (including 0.35 and 0.4). The results show that cement mortars containing nanoparticles have a reasonably higher strength and denser interfacial transition zone than do ordinary portland cement ferrocement mortars, while the flowability of mortars with and without nanoparticles is considered equal.

Development of high strength flowable mortar with hybrid fiber

An experimental study was conducted on the high strength flowable mortar reinforced by the different percentages of steel fiber (0–2%), palm fiber (0–1%) and the hybridization of these two fibers with 2% volumetric fractions to determine the density, compressive strength, flexural strength and toughness. The results show that such hybridization are promising concept and the replacement of a portion of steel fiber with palm fiber can significantly reduce the density, enhance the flexural strength and toughness.

Effect of limestone filler content and superplasticizer dosage on rheological parameters of highly flowable mortar under light pressure conditions

The influence of pressure on the yield stress and plastic viscosity of SCC mortars was investigated using an adapted Marsh cone with cylindrical shear paddles. Nine mortars proportioned with various limestone filler content and high-range water-reducing admixture (HRWRA) dosage from 0.65% to 0.85% were prepared. Test results show that when a pressure is exerted on the mortars, the material does not behave as a homogeneous fluid, i.e. having a yield stress depending only on the specific gravity of the mixture and the height of poured mortars and a constant value of plastic viscosity, but as a separative multiphasic material which consolidates, leading to exponential variations of τ 0 and lowering values of μ with pressure. The HRWRA dosage or the limestone filler content has only an effect on the initial value of the yield stress, but has more influence on the variation of plastic viscosity of the mortar with pressure.

Lubricated compression and X-ray microtomography to analyse the rheology of a fibre-reinforced mortar

In this work, the microstructure and the rheology of a glass-fibre-reinforced fresh mortar were studied. Various fibre contents and aspect ratios and two types of fibrous reinforcement, i.e. slender fibre bundles and fibres, were tested. The microstructure was analysed by using X-ray microtomography. It is shown that the non-deformed mortar is a porous granular suspension, the porous microstructure of which is not influenced by the presence of fibres, which in turn display a 2D planar random fibre orientation. The rheology was investigated by subjecting samples to constant axial strain rate and lubricated compression. The roles of the actual strain, the mortar resting time, the fibre content and aspect ratio on recorded stress levels are emphasised. Besides, for the investigated strain rate and material parameters, the mortar flow is quasi-incompressible and does not affect significantly the porous microstructure nor the fibrous one. Lastly, the stress increase which is induced by the addition of fibre bundles is similar to that predicted by Newtonian models of semi-dilute fibre suspensions.