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This paper aims to investigate the bond strength of metakaolin-based geopolymer mortar with cement mortar.

The mortar-mortar bond strength is assessed by slant shear and split tensile tests; pure shear strength is evaluated by Mohr’s criterion for result validation. Metakaolin-based geopolymer mortar is cast over the cured cement mortar specimen with two levels of surface roughness: smooth or grooved interface. The influence of the alkaline solution to metakaolin ratio on geopolymer bond strength is studied. Compressive strength, ultrasonic pulse velocity, permeability and flow table tests are also performed.

The paper’s findings are highlighted as follows: (1) strong mortar-mortar bond properties achieved for geopolymer mortar in all tests and conditions and validated by Mohr’s criterion and pure shear, (2) a lower alkaline solution to metakaolin ratio achieves higher bond strength to Portland cement mortar and (3) geopolymer mortar has higher compressive strength and ultrasonic pulse velocity than cement mortar at all curing ages; additionally, it is more flowable and less permeable.

The full replacement of Portland cement with metakaolin, a more sustainable cementitious material, will contribute to the decarbonization of the construction industry.

Limited research has been carried out on the bond strength of metakaolin-based geopolymer mortar to Portland cement mortar. Also, computing the pure shear using Mohr’s circle criterion of metakaolin-based geopolymer to validate the results can be considered original.

The purpose of this paper is to investigate the influence of cement/sand ratio on behaviour of cement mortar.

Literature review was used to confirm that the cement/sand ratio have influence on the mortar strength and that its influence is not very studied. The literature points out also that the constitutive model of mortar is very important in the structural design of masonry but it has not been investigated much.

The results of study allow to forecast the mortar strength by the cement/sand ratio when the water/cement ratio is fixed (0.50). Besides, the obtained experimental results allow defining a constitutive model for sand mortar.

Other experiments would be proper to extend the research field.

The findings are of particular importance to mix design of cement mortar and to structural design of masonry. In fact, for mortar in the practices, there are no constitutive equations to use in the structural calculation, and so, normally the engineers use the constitutive equations of concrete (very rough). The idea is to find constitutive equations that, using simple and economic tests, allow to engineers to model more correctly the realty.

There are few studies which try to investigate the relationship between the behaviour of cement mortar and cement/sand ratio, as well as to study constitutive model of cement mortar. This paper contributes to bridging that gap.

The main aim of the current study is to investigate the effect of Anti-Crack HP 67/36 glass fibre on the mechanical performance of mortars made of cement, with a focus on post-cracking evaluations using the digital image correlation (DIC) technique.

Experimental tests were carried out on 36-mm long fibres at 0.8% by volume and added to the normal strength (NSM), high strength (HSM) and high strength mortar with fly ash (HSMFA) mortars. CEM I 52.5 CP2 NF, CEM II/A-L 42.5 NF and CEM III/C 32.5 N-SR PM were used for each series of mortar to assess the performance of the glass fibres with the types of cement. F-class fly (FA) ash was used to reduce global CO₂ emissions.

The mortar’s strength decreased as the cement types changed from CEM I to CEM II and III. However, due to changes in the portlandite content of the cement, water porosity increased for both types of mortar, without and with fibre. It was also found that using glass fibre increased flexural strength more than compressive strength, regardless of the type of cement used. For all the strength classes, it was found that the mortar mixes with CEM I had the highest critical crack opening (w_c) and fracture energy (G_F), followed by CEM II and III. No significant effects were observed in the mortar’s property by replacing fly ash (12%).

Only mortars were formulated in this study, but the results must be verified at the concrete scale.

Validation of the DIC technique to characterize the post-cracking behaviour of cement-based material. Use of glass fibres to improve the material’s resistance to cracking.

Use of CEM II and CEM III cements with low CO₂ footprint instead of CEMI without altering the mechanical performance of the material.

The work is a further contribution to studying the cracking behaviour of several series of variable mortars depending on the resistance class and the type of cement used.

This study aims to propose a technique that establishes a mathematical relationship between width and time, and utilizes a derivative method to determine the initial printable time (tint) for mortar suitable for 3D printing. The study conducted experimental tests on the tint, layer strain, and the relationship between filament width and time. These tests involved plain mortar and mortar reinforced with micro-fibers at varying volume fractions. The tint was determined analytically using the derivative method.

This study introduces a technique to accurately determine the initial printable time (tint) and width/height of printed cement mortar. Precise tint determination is essential for ensuring proper filament printing timing and eliminating the need for trial and error.

Results show that the proposed technique accurately determines the tint, as evidenced by the resemblance between expected and actual initial widths. Fiber-reinforced mortar (FRM) has a smaller tint than plain mortar, which decreases with an increasing fiber content. Additionally, FRM displays smaller layer strains compared to plain mortar.

Results show that the proposed technique accurately determines the tint, as evidenced by the resemblance between expected and actual initial widths. FRM exhibits smaller tint and displays smaller layer strains than plain mortar.

This study introduces a novel technique that uses a mathematical relationship to determine the tint and height of cement mortar printing.

Efflorescence formation is very common in cement-based materials. In the case of mortar, efflorescence is more studied when only Portland cement is used as a binder. However, the repair of historical heritage, as well as the construction system of some countries, usually uses mortars composed of hydrated lime and Portland cement. This study aims to determine the influence of the hydrated lime content on the incidence of efflorescence in mortars.

Mortars with 0%, 50%, and 100% lime/cement ratio were studied, using three different methods to accelerate efflorescence formation. The surface area of mortars affected by efflorescence was quantified by analysis using image software. Also, analysis of mercury intrusion porosity test, flexural tensile, compressive strength, absorption of water by capillarity, porosity, XRD and TGA was performed.

More efflorescence in mortars with a higher amount of lime in their composition was observed. The results show that the increase in the lime content reduces the flexural tensile and the compressive strength and increased the absorption of water by capillarity and the porosity of the mortars. The material formed by the efflorescence was calcium carbonate, proven by microstructural tests.

The results of greater efflorescence formation in mortars with lime are important to alert users who apply this type of material. Some type of protection must be done more rigorously for lime-cement mortars, especially concerning contact with water, since efflorescence tends to be faster for this type of material.

The purpose of this paper is to add expanded perlite (EP) immobilized microorganisms that replace part of the standard sand in mortar to improve the self-healing ability of mortar cracks and reduce the water absorption of mortar after healing.

Bacillus pseudofirmus spores were immobilized with EP particles as self-healing agents. The effects of adding self-healing agents on the compressive strength of mortar specimens were observed. The ability of mortar specimens to heal cracks was evaluated using crack microscopic observation and water absorption experiments. The filler at the cracks was microscopically analyzed by scanning electron microscope and X-ray diffraction experiments.

First, the internal curing effect of EP promotes the hydration of cement in mortar, which generates more amount and denser crystal structure of Ca(OH)2 at mortar cracks and improves the self-healing ability of mortar. Second, the self-healing ability of mortar improves with the increase of self-healing agent admixture. Adding a self-healing agent of high admixture makes the planar undulation of calcite crystal accumulation at mortar cracks more significant. Finally, the initial crack widths that can be completely healed by adding EP and self-healing agents to the mortar are 200 µm and 600 µm, respectively.

The innovation points of this study are as follows. (1) The mechanism of the internal curing effect of EP particles on the self-healing ability of mortar cracks was revealed by crack microscopic observation tests and microscopic experiments. (2) The effect of different self-healing agent amounts on the self-healing ability of mortar cracks has been studied. (3) The effects of EP particles and self-healing agents on healing different initial widths were elucidated by crack microscopic observation tests.

Hardened cement paste is a heterogeneous system resulting from the grouping of particles, films, microcrystals and other solid structural elements bounded in a porous mass. The cement paste microstructure must be understood firstly due to its influence on concrete properties. The behaviour of concrete greatly depends on the conformation of localised special structures rather than on general structures found in the mass cement paste. The objective of this paper was to study the cement paste microstructure, as a function of the water–cement ratio, in order to interpret the variations of the steel–mortar bond strength and the developing of the corrosion process in steel–mortar specimens kept in tap water and 3 percent sodium chloride solutions for 1 year. A description of the steel–mortar interface was also provided.

For the purposes of this article, adhesives, lutes and putties are excluded even though many of them have applications in the corrosion‐resistant field. Included are the pouring and mortar‐type cements based on bitumen or sulphur, sodium and potassium silicate solutions, silica sols, rubber or synthetic rubber latices, and synthetic resins. The author considers the composition and working properties of these cements and surveys present trends in their use in industry. Recent and possible future developments are covered.

The aim of this paper is to determine the thermal conductivity of a protective layer of alkali-activated cement and the possibility of performing fire protection with fireclay sand and Lightweight mortar. Unprotected steel structures have generally low fire resistance and require surface protection. The design of passive protection of a steel element must consider the service life of the structure and the possible need to replace the fire protection layer. Currently, conventional passive protection options include intumescent coatings, which are subject to frequent inspection and renewal, gypsum and cement-based fire coatings and gypsum and cement board fire protection.

Alkali-activated cements provide an alternative to traditional Portland clinker-based materials for specific areas. This paper presents the properties of hybrid cement, its manufacturability for conventional mortars and the development of passive fire protection. Fire experiments were conducted with mortar with alkali-activated and fireclay sand and lightweight mortar with alkali-activated cement and expanded perlite. Fire experiment FE modelling.

The temperatures of the protected steel and the formation of cracks in the protective layer were investigated. Based on the experiments, the thermal conductivities of the two protective layers were determined. Conclusions are presented on the applicability of alkaline-activated cement mortars and the possibilities of applicability for the protection of steel structures. The functionality of the passive fire layer was confirmed and the strengths of the mortar used were determined. The use of alkali-activated cements was shown to be a suitable option for sustainable passive fire protection of steel structures.

Eco-friendly fire protection based on hybrid alkali-activated cement of steel members.

The purpose of this paper is to develop an alternative new ternary geopolymer mortar (MKSP) to resolve a traditional mortar problem which exhibits several disadvantages, including poor strengths and surface microcracks and the CO₂ air pollution.

The MKSP ternary binder was produced using metakaolin (MK), slag (S), and palm oil fuel ash (POFA) activated with an alkaline mixture of sodium silicate (Na₂SiO₃) and 10 M NaOH in a mass ratio of 2.5. Seven different mix proportions of MK, slag, and POFA were used to fabricate MKSP mortars. The water-to-binder ratio was varied between 0.4 and 0.5. The mortars were heat cured for 2 h at 80°C and then aged in air. Flexural stress and strain, mortars flow and compressive strength were tested. Furthermore, the mortars were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) analyses.

The results showed that the sample MKSP6, which contained 40 percent MK, 40 percent slag, and 20 percent POFA, exhibited high compressive strength (52 MPa) without any cracks and flexural strength (6.9 MPa) at 28 days after being cured for 2 h at 80°C; however, the MKSP7 mortar with optimal strength of 55 MPa showed some surface cracks . Further, the results of the XRD, SEM, and FTIR analyses indicated that the MKSP mortars primarily consisted of a crystalline (Si+Al) phase (70 percent) and a smaller amorphous (Si+Ca) phase (30 percent).

The MKSP ternary geopolymer mix has three limitations as an importance of heat curing for development early strength, POFA content less than 20 percent to gain high normal strength and delaying the sitting time by controlling the slag content or the alkali activator type.

The use of geopolymer materials binder in a real building is limited and it still under research, Thus, the first model of real applied geopolymer cement in 2008 was the E-Crete model that formed by Zeobond company Australia to take the technology of geopolymer concrete to reality. Zeobond Pty Ltd was founded by Professor Jannie S.J. van (van Deventer et al., 2013), it was used to product precast concrete for the building structure. The second model was PYRAMENT model in 2002 by American cement manufacturer Lone Star Industries which was produced from the development carried out on inorganic alumino-silicate polymers called geopolymer (Palomo et al., 1999). In 2013 the third model was Queensland’s University GCI building with three suspended floors made from structural geopolymer concrete containing slag/fly ash-based geopolymer (Pathak, 2016). In Australia, 2014, the newly completed Brisbane West Wellcamp airport becomes the greenest airport in the world. Cement-free geopolymer concrete was used to save more than 6,600 tons of carbon emissions in the construction of the airport. Therefore, the next century will see cement companies developing alternative binders that are more environmentally friendly from a sustainable development point of view.

Production of new geopolymer binder of mortar as alternative to traditional cement binder with high early and normal strength from low cost waste materials, less potential of cracking, less energy consumption need and low carbon dioxide emission.