Physical Properties Of Mortar Research Articles

Encapsulated crystallisation inhibitor as a long-term solution to mitigate salt damage in hydraulic mortars

Salt (NaCl) weathering in mortar, can be mitigated by incorporating a crystallisation inhibitor (sodium ferrocyanide) during mortar preparation. However, the service-life of the inhibitor is limited, due to its susceptibility to leaching out of mortar. Encapsulating the inhibitor in chitosan-calcium alginate capsules has demonstrated controlled-release of the inhibitor and therefore, reduction in its leaching. Nevertheless, the addition of capsules may have a negative effect on mortar's properties and/or its salt-weathering resistance. In this research, natural hydraulic lime (NHL) and commercial cement-based mortars were prepared, with encapsulated inhibitor and with directly mixed-in inhibitor. Mechanical and physical properties of mortars were assessed experimentally. An accelerated NaCl-weathering test was performed to assess the durability of mortar to salt damage. The damage evolution was assessed visually and by quantifying material loss, efflorescence and leaching of the inhibitor. At the end of the test, crystal morphology inside the pores was examined using SEM. The results show that adding inhibitor, both in encapsulated and mixed-in form, had a negligible effect on the properties of NHL and cement-based mortars. Compared to the reference mortar without inhibitor, NHL-mortars with mixed-in inhibitor and encapsulated inhibitor had a better durability to salt damage, showing negligible material loss. The capsules facilitated controlled-release and reduced leaching of the inhibitor. In cement-based mortars including the reference, no damage was observed; still, the inhibitor was shown to be effective in modifying the salt crystal habit. The results show that encapsulation of the inhibitor can improve the service-life of the mortar without compromising its performance.

An experimental study on the sulfuric acid resistance of mineral additive mortars

Mineral additives are preferred to improve the physical, mechanical and durability properties of cement-based composites and to reduce the use of cement to prevent environmental pollution and high production costs. Within the scope of this study, a new pozzolanic material, ground profillite powder (GPP), was evaluated by comparing it with granular ground blast-furnace slag (GGBFS), and it was used as a substitute for cement at ratios of 5, 10 and 15% by weight. The effects of these two mineral additives on the mechanical and physical properties of mortars and their resistance to sulfuric acid (SA) were investigated. In the production of the mortar samples, CEM I 42.5/R-type Portland cement (ordinary Portland cement) was used as the binder, and 0–4 mm crushed sand was used as the aggregate. Mineral additive and non-additive mortars were produced in the laboratory environment in dimensions of 40 × 40 × 160 mm. Spreading values, bending and compressive strengths, water absorption and porosity values and weight and strength loss values under the effect of SA were examined comparatively. It was determined that the mortar samples produced using GPP showed higher resistance to SA attacks than the pure and GGBFS-added mortars, reducing weight losses up to 21% and compressive strength losses up to 30%.

Production of environmentally-friendly, high-strength repair mortar for the restoration of historical buildings

In this study, repair mortars with artificial and natural pozzolan additives were produced for the restoration of historical buildings. Class C fly ash, an artificial pozzolan and zeolite the natural pozzolan, were substituted into these lime-based mortars. Two different aggregate types were used in the preparation of the mortars: natural river sand and crushed brick. A total of 18 batches of mortars were produced, two of which were reference batches. In the first group of batches, fly ash, which is the major pozzolan, was tested in both aggregate groups in 20%, 40%, and 60% ratios of lime substitution. In the second group of batches, fly ash and zeolite were used in different proportions as lime substitution. In the reference series, air lime was used alone. At the end of the 28, 56, and 90 days curing period, mechanical, physical properties, and phase composition of the mortars were determined. When the pozzolan-added mortars were compared with the reference mortars, it was observed that pozzolans provided significant improvements in the physical and mechanical properties of the repair mortars. While significant improvements were observed in the physical properties of the mortars where fly ash was used as the only pozzolan, mechanical properties were better in the mortars with zeolite.

Physical and Mechanical Effects of Silica Sand in Cement Mortars: Experimental and Statistical Modeling.

The environmental impacts of cement manufacturing are becoming a real-time issue that requires attention. This paper investigates the mechanical and physical properties of mortars with finely ground sand as a substitute for cement. The experimental program consisted of three silica sands with a Blaine Specific Surface (BSS) area of 459 m2/kg, 497 m2/kg, and 543 m2/kg and four substitution ratios of 10%, 20%, 30%, and 40%. A total of 12 mixtures have been prepared and tested for comparison to the reference mortar. The pozzolanic effect of the sand was evaluated using thermogravimetric analysis (TGA). The results revealed that the fineness variation from 459 m2/kg to 543 m2/kg resulted in an increase of 20% and 30% in water absorption and compressive strength, respectively. However, increasing the substitution ratio from 10% to 40% led to a 40% decrease in mechanical strength and a 25% increase in water absorption. The statistical analysis of the results demonstrated that both factors under study influenced compressive strength and water absorption. The ANalysis of VAriance (ANOVA) confirmed that the proposed regression equations predict the experimental results. Further studies will investigate both the technical and environmental performances of cement mortars with finely ground silica sand.

Effect of Initial Water Sprinkling Curing on Strength Development of Precast Concrete

In general, steam curing is applied to improve the productivity of precast concrete products. After steam curing, products are stored outdoors for secondary curing before shipment. However, drying shrinkage and microcrack expansion that occurs during steam curing may impede strength enhancement. On the other hand, water curing is also clearly effective as a secondary curing process. However, installing a water curing pool in a precast concrete plant is not easy due to limited space. Therefore, this study focused on water sprinkling curing, which is relatively easy to perform without such restrictions. In this study, the effects of water sprinkling curing on the physical properties of mortar at the initial age of steam curing were investigated from the aspects of materials, mix proportions, curing conditions, and test piece dimensions. The results showed that water sprinkling curing increased the compressive strength by about 10% compared to curing under air. The effect of water sprinkling curing increased as the specific surface area of the test piece increased.

Basic Study on the Effect of Water Sprinkling Curing Immediately after Demolding on the Initial Strength of Steam Cured Mortars

Steam curing is generally applied to improve productivity of precast concrete products. After steam curing, the products are stored outdoors as a secondary curing process until shipment. However, drying shrinkage and expansion of microcracks that occur during steam curing may inhibit strength improvement. On the other hand, water curing is also clearly effective as a secondary curing process. However, installing a water curing pool in a precast concrete plant is not easy due to limited space. Therefore, we focused on water sprinkling curing, which is relatively easy to perform without such restrictions. In this study, the effects of water sprinkling curing on the physical properties of mortar at the early age of steam curing were studied from the aspects of materials, mix proportions, curing conditions, and temperature of water used for sprinkling curing. As a result, it was confirmed that water sprinkling curing at an early age after demolding resulted in a rapid decrease in the temperature of the mortar surface layer. However, it was confirmed that the same conditions were effective in increasing compressive strength.

Influence of the Partial Substitution of Industrial Clinker by Volcanic Lava Powder from Nyiragongo Volcano on the Physical Properties of Mortars

Influence of the Partial Substitution of Industrial Clinker by Volcanic Lava Powder from Nyiragongo Volcano on the Physical Properties of Mortars

Substitution of aggregates by waste foundry sand: effects on physical properties of mortars

The substitution of the normalized aggregate by residual foundry sand (WFS) was studied on the physical properties of mortars by means of resistance to compression and capillary absorption tests. The aggregate was replaced by WFS in its natural state (WFS), washed residual foundry sand (WFSW) and heat treated residual foundry sand (WFST). The WFS had a percentage of bentonite, which was sought to be thermally activated. It was found that the physical behavior of the mortars containing WFS and WFSW was similar to that of the control sample. The clay recovered from the sand washing was evaluated for its pozzolanic potential, it was found that, with the thermal treatment, the montmorillonite acquires pozzolanic behavior. Mortars with WFST presented a drop in compressive strength. The pozzolanic effect achieved in the clay was not reflected in the compressive strength of the mortars with WFST.

다양한 붕소화합물이 혼입된 모르타르의 물리적 특성과 제타전위와의 관계

본 연구에서는 붕소화합물을 혼입하여 시험체를 제작하였으며 이에 대한 물리적 및 전기적 특성에 대한 검토를 수행하였다. 사용된 붕소화합물은 pH 값에 따라 선별한 것으로 산성인 붕산(AA)과 약알칼리성의 붕사(AB), 강알칼리성인 붕사(HB)이다. 실험은 모르타르의 전기적 특성을 파악할 수 있는 제타전위 측정을 기본으로 슬럼프 및 공기량 측정, 응결시험, 재령별 압축강도 시험을 수행하였다. 제타전위 측정 결과 전반적으로 붕소화합물을 혼입한 시험체가 기준 시험체보다 제타전위의 절대값이 높게 측정되었다. 이로 인해 붕소화합물을 혼입한 시험체의 슬럼프 플로우 값은 기본 시험체(MOR)보다 전반적으로 증가하였다. 또한, 응결 시험 결과에서도 붕소화합물이 혼입된 시험체의 경우 응결 지연 등이 발생하였다. 압축강도 시험 결과 붕소화합물의 종류에 상관없이 전반적으로 강도 저하가 발생하였으며 이는 제타전위의 영향으로 응결 지연이 발생하고 이로 인해 수화 및 화학반응 등이 저해되어 강도에 영향을 미친 것으로 판단된다. 따라서 붕소화합물을 혼입시 붕소의 종류 및 화합물의 성분, pH 환경에 따라 제타전위 값이 다르게 발생되며 이로 인해 슬럼프 플로우 및 응결 지연 등의 물리적 성능에 영향을 미치기 때문에 이를 고려하여 최적 혼입량 등을 결정하는 것이 바람직할 것으로 판단된다.

Bacteria incorporated with calcium lactate pentahydrate to improve the mortar properties and self-healing occurrence

Concrete can be harmful to the environment due to its high energy consumption and CO2 emission and also has a potential crack formation, which can promote a drop in its strength. Therefore, concrete is considered as a non-sustainable material. The mechanisms by which bacterial oxidation of organic carbon can precipitate calcite that may fill the voids and cracks on cement-based materials have been extensively investigated to prevent and heal the micro-cracks formation. Hence, this study focused on utilizing a new alkaliphilic bacterial strain indigenous to an Indonesian site, Lysinibacillus sphaericus strain SKC/VA-1, incorporated with calcium lactate pentahydrate, as a low-cost calcium source, with various bacterial inoculum concentrations. The bacterium was employed in this study due to its ability to adapt to basic pH, thus improving the physical properties and rejuvenating the micro-cracks. Experimentally, the addition of calcium lactate pentahydrate slightly affected the mortar properties. Likewise, bacteria-incorporated mortar exhibited an enhancement in the physical properties of mortar. The highest improvement of mechanical properties (an increase of 45% and 36% for compressive and indirect tensile strength, respectively) was achieved by the addition of calcium lactate pentahydrate incorporated with 10% v/v bacterial inoculum [about 7 × 107 CFU/ml (colony-forming unit/ml)]. The self-healing took place more rapidly on bacterial mortar supplemented with calcium lactate pentahydrate than on the control specimen. XRD analysis demonstrated that the mineralogical composition of self-healing precipitates was primarily dominated by calcite (CaCO3), indicating the capacity of L. sphaericus strain SKC/VA-1 to precipitate calcite through organic carbon oxidation for self-healing the artificial crack on the mortar. To our knowledge, this is the first report on the potential utilization of the bacterium L. sphaericus incorporated with calcium lactate pentahydrate to increase the mortar properties, including its self-healing ability. However, further study with the water-cement ratio variation is required to investigate the possibility of using L. sphaericus and calcium lactate pentahydrate as an alternative method rather than reducing the water-cement ratio to enhance the mortar properties.

Influence of Mixed Admixtures on Properties of Aeolian-sand Mortar

Using Aeolian sand as fine aggregate, adopt fixed lime sand ratio(1:2, Under the same consistency of mortar, the effect of single and compound doping of VAE and Water retaining agent(BS-W) on the working and physical properties of mortar was studied. Through the coMparison of its properties with blank mortar, to get the best content of admixture and the best proportion of compound admixture, to provide ideas for the development and research of high proportion or total replacement of aeolian sand mortar. The results show that: VAE and water retaining agent can obviously improve the workability, construction and water retaining performance of the slurry, but the physical and mechanical properties of mortar are reduced. When VAE content is 0.7%, BS-W content is 0.15%, the overall performance of mortar mixed with them is better, the flexural strength and compressive strength of mortar reached 4.78Mpa and 15.3Mpa respectively in 28d.

Influence of treated bio-fibers on the mechanical and physical properties of cement mortars

Alfa plant (Stipatenacissima L.) and wheat straw fibers were investigated as reinforcement in cementitious matrix. The fibers were used separately in three states: raw, wet (by immersion in water) and alkali treated. A reference mortar without fibers and mortars with 1% and 1.5% by volume of the two different bio-fibers were used. The mechanical and physical properties of mortar specimens were studied as well as the morphological analysis was carried out after 28 days of curing. The results exhibit that both Alfa and Straw fibre addition changed the mechanical performance of mortars in comparison to the reference mortar. A higher porosity and water absorption were observed after the addition of raw and wetted fibers. The alkali treatment caused morphological changes that were proved more efficient. This treatment provided a good result in terms of mechanical and physical properties. Furthermore, the addition of 1% by volume of alkali treated fibers affords both mechanical and physical properties better than the control mortar. SEM micrographs confirmed the good fibers/matrix adhesion of the alkali treated fibers.

Physical and mechanical studies on binary blended Portland cements containing mordenite-rich tuff and limestone filler

In this research, we made physical and mechanical analyses thanks to which we deduced that the potential of replacing the Portland cement up to 20% by modernite-rich tuff (TM) and limestone filler (LF). The experimental procedure was done in two main stages. The first stage was dedicated to the pastes, including water requirement, setting time, hydration heat and free Ca(OH)2 content. In the second stage, mechanical and physical properties of mortars, water porosity and pore size distribution were studied. The final results show that LF mixtures closest to the control mixtures unlike the MT mixtures which exhibited a high water demand, less free Ca(OH)2, rapid appearance of the maximum thermal effect, an increase in the total and water accessible porosity, there is also a delay in improving of strength.

Characterization of sewage sludge ash and its effect on moisture physics of mortar

A study was carried out to investigate the potential use of ash obtained as an incinerated by-product in sewage sludge treatment, as a possible supplementary cementitious material. Chemical parameters and granulometry of the sewage sludge ash and selected physical and hygroscopic properties of cement-ash-based mortar are presented and compared with results from previous studies. The effect of different ratios of cement substitution and two pre-treatment methods for ash, i.e. ash grinding and water washing, on the physical properties of mortar were investigated by using density, porosity and compressive strength as elemental indicators of the mortar quality. The hygroscopic sorption properties of the individual constituents alone and the resulting mortar samples were described by sorption isotherms for water vapour and by a capillary water absorption test. Results showed that the SSAs typically consisted of larger particles compared to the cement particles. Incorporation of ash resulted in more porous mortar structures compared to cement-based mortar, which affected the material's mechanical properties such as the compressive strength. 28-day compressive strength decreased with increasing ash content and porosity. Cement conveyed the greatest ability to adsorb and react with water and there were clear differences between the different ashes. Despite the differences in sorption properties between the different constituents, the effect of ash content on mortar sorption isotherms was negligible.

Formulation of low cost eco-repair mortar based on dune sand and Stipa tenacissima microfibers plant

Mortar for patch repair of damaged concrete elements by corrosion or honeycombing are extensively used. However, they are quite expensive and they frequently incorporate low volume of synthetic fibers. This paper presents an experimental study on the development of an eco-repair mortar based on dune sand and microfibers plant. The vegetable fibers are 3–5 mm long Alfa microfibers plant (Stipa tenacissima L.) and are used with different volume ratios. The physical and mechanical properties investigated are compressive strength, flexural strength, shrinkage and bonding strength. The durability of mortar was evaluated through gas permeability and capillary water absorption tests. The results obtained show an enhancement of the mechanical and physical properties of mortars with natural microfibers compared to those of mortars without natural fibers. A lower sorptivity and a lower gas permeability were also obtained for the repair mortar reinforced with microfibers plant.

Effect of Polysiloxanes on Roughness and Durability of Basalt Fibres⁻Reinforced Cement Mortar.

The influence of roughness and the way it affects the adhesion properties and surface free energy (SFE) of polysiloxanes hydrophobised basalt fibres–reinforced cement mortars were determined in this article. The physical properties of mortars were investigated in the experimental part, which also explored the impact of hydrophobisation and basalt fibres (BF) addition on SFE, frost resistance, contact angle (CA), and roughness. A device capable of calculating all parameters was used to indicate the surface roughness and 3D topography. Prior to and after conducting surface and weight hydrophobisation, the contact angle of mortars was specified. Subsequently, it was used for carrying out SFE calculation by means of Neumann’s method, enabling us to characterize the adhesion properties and wettability of mortars. The research indicated that the surface roughness was substantially decreased, in turn raising the frost resistance. The corrosion resistance drops when the surface roughness, water absorption, and number of fibres in the mortar increase. The SEM images presenting the structure of polysiloxane coating and mortars were provided.

Cement-fly ash mortars durability, with fly ash from fluidized bed boilers and conventional combustion, exposed to aggressive environment influence

The study shows results of research on the aggressive environment impact (1, 3 and 5% HCl solution) on durability of cement mortars with fraction from 30 to 45% by mass of fly ashes from the fluidized bed combustion (FBC fly ash) and conventional fly ashes used separately and in the form of a mixture. The impact of aggressive environments on durability of cement and ash mortars was tested for aperiod of 365 days, by testing the compressive strength, linear changes, mass loss and porosity. It was demonstrated that mortars with the content of FBC fly ashes, after 365 days of tests showed the higher resistance to aggressive environment impact. It is confirmed by e.g. their higher compressive strength, and thus the reduced total porosity. Reduction of total porosity content (<50 nm) was accompanied by the increased compressive strength, which in the aqueous environment was in favour of cement mortars, and in the aggressive environment in favour of cement and ash mortars. It was demonstrated that the content of pores < 200 nm was lower for mortars with FBC fly ashes and mixtures of ashes regardless of environment the mortars were stored in. A beneficial impact of FBC fly ashes was found on physical properties of mortars, i.e. reduction of the shrinkage, lower mass loss and reduced destruction of mortars in the acid corrosion environment. That effect was especially beneficial for the mortar with higher (45% by mass) content of FBC fly ashes, regardless of aggressive character of the environment.

Preliminary electrochemical cementation of high volume fly ash mortars

This paper summarizes a research about the electrochemical activation of the cementitious properties of fly ash. Taking into account that in recent years there have been various environmental issues associated with the production of Portland cement (PC), the use of Fly Ash (FA) has been promoted in the production of concrete. Traditionally, the use of fly ash has been possible through its blending with Portland cement and as a geopolymeric cementitious material. In this research, a third technique for fly ash activation, known as electro-mutagenesis, was investigated. This treatment consisted in the late hydration of fly ash after the migration of ions from an external alkaline solution, by applying an electric field across the hardened mortar. Solutions of sodium hydroxide and sodium silicate with different molar concentrations were used as a source of alkaline ions. The electrical treatment was applied in many mortar samples using high volume proportions of fly ash, a constant water to binder ratio, and a fixed aggregate content. After treatment, the compressive strength, the ultrasonic pulse velocity, and the microstructure of the mortar matrices were investigated. Results showed that the alkaline ions migrated into the hardened mortar through the permeable capillary pores, reacted with the un-hydrated fly ash and mutated in new hydration phases, producing an improvement in the physical properties of mortar.

A Study of Natural Pozzolan Mortars Exposed to Sulfate as Energy Efficient Building Material

Reinforcement corrosion is one of the main causes of concrete deterioration. The steel in concrete is naturally protected from corrosion by the presence of a passive film formed through the high alkalinity of concrete. A technique to improve the protection of steel in concrete is the inclusion of mineral additions. Natural pozzolan (NP) from Beni-Saf is a mineral addition that is abundant in western Algeria. The experiment was conducted on mortar specimens, containing steel bars and exposed to the aggressive solutions of Na2SO4 and MgSO4. The status of reinforcement is periodically monitored by measuring the electrochemical potentials and the corrosion rates by the technique of linear polarization resistance (LPR) and also the thermal conductivity was evaluated. The test results show that natural pozzolan significantly affects the physical properties of mortars, improves the corrosion resistance of mortars containing up to 20% of natural pozzolan and reduces the thermal conductivity.

Influence of Silica Based Waste Materials on the Mechanical And Physical Properties of Mortar

This is an investigation on the influence of silica based waste materials namely silica fume (SF) and recycled vase (RV) on the physical and mechanical properties of mortar. Results showed that 15%SF modified mortar achieved the highest strength and lowest water absorption capability compared to Control mortar and other mixtures. The result was confirmed by water absorption capability test for the same mixtures where 15% SF modified mortar was found to absorb the least. Furthermore, combination of 15% SF and 10% RV achieved the lowest water absorption compared to other combinations samples but higher than Control and 15% SF modified mortar. The results of this study indicated that SF is highly pozzolanic material that can be an excellent cement replacement material to produce high-performance concrete. Study on pozzolanc behavior of SF samples subjected to longer hydration time is needed. Further microstructural investigation is needed to confirm the hypothesis on retardation of hydration due to unreactive RV.