Amount Of Calcium Hydroxide Research Articles

Influence of nano-silica on the performances of concrete under the negative-temperature curing condition

In previous studies, nano-silica (NS) can improve the concrete performances under the conventional curing condition (about 20 °C). However, because more and more engineering projects are constructed in cold regions, it is very important to study the performances of concrete, which is cured under the negative-temperature condition. In order to explore whether NS still has the positive effect on concrete cured under the negative-temperature condition, multi-scale experiments were conducted to investigate the influence of NS on the performances (mechanics, resistance to chloride ion penetration (RCP) ability, pore characteristics, microstructure, and hydration products) of the concrete cured under the condition of −3 °C. The results indicate that the negative-temperature curing condition is not conducive to the formation of compressive strength for concrete. Under the curing condition of −3 °C, the cement paste and the interface transition zone are deteriorated by the addition of NS, which reduces the compressive strength of concrete. In addition, as the increase of the NS content added into the concrete under the curing condition of −3 °C, the compressive strength, the RCP ability, and the amount of calcium hydroxide generated decrease, and the coarsening of pore structure increases.

Studies on computing compressive strength of zeolite blended concrete using multiple regression analysis

Concrete is most extensively adopted materials for construction, due to its high ration of durability to cost. The important factor on which concrete performance depends is characteristics of cement consumed during concrete production. Greater the environmental and economic profits can be achieved when addition of Pozzolanic mineral additives such as fly ash, GGBFS in Concrete production. It is normally accepted that adding of pozzolan decreases the amount of calcium hydroxide in paste of cement and raises the perviousness of concrete.Zeolites are alumina silicates having crystalline properties with even pores and hollows. They hold exceptional characteristics, such as molecular sieves, ion exchange, a huge area of Surface, and catalytic action, which mark them as anticipated ingredient for numerous industrial uses. The Pozzolanic features of Zeolite are largely due of their volatile content of SiO2 and Al2O3. This content reacts with calcium hydroxide (CaOH2) which is generated in the procedure the Cement hydration, and transforms it into Calcium silicate hydrate (CSH) gel. Hence, the microstructure of concrete is enhanced and the concrete turn out to be impermeable.Additives of zeolite concrete implants have been attempted to advertise hazardous substances, especially those contained in car extinguishing. It can be believed that the estimation regarding CO2 absorption of concrete with added zeolite has not been tested, yet zeolite displays a very good adsorption property for CO2 and NOx.In this study, it is proposed to examine the influence of blending of Natural Zeolite on strength properties of Concrete. Statistical Package for the Social Sciences (SPSS) package is used for multiple regression Analysis to suggest a formulae for strength forecast. The predicted result is validated with the test results conducted in Laboratory on Zeolite blended Concrete.

Petrographic analysis of in-service cementitious mortar subject to freeze-thaw cycles and deicers

Chloride-based deicers, especially CaCl2 and MgCl2, can damage cementitious materials due to the formation of mineral phases such as calcium oxychloride and brucite. However, there are only limited direct observations of calcium oxychloride formed in cementitious materials in the field. This paper uses petrographic methods to evaluate damage of an in-service cementitious mortar substrate subject to freeze-thaw cycles and deicers for six years. The amount of calcium hydroxide in the mortar was quantified using thermogravimetric analysis. Changes in hydration products and microstructure were characterized by optical microscopy. Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy was used to examine the morphology and elemental composition of secondary deposits related to the deicer damage. The mortar with less than 3% air exhibits horizontal cracks and microcracks cutting around aggregate particles. The cracks and microcracks are partially filled with calcium oxychloride due to the application of CaCl2. A densified crust of brucite and calcite, likely associated with the usage of MgCl2, covers the top surface of the damaged mortar. The deicer exposure results in leaching of calcium hydroxide mainly due to the formation of calcium oxychloride. Calcium leaching increases the apparent paste porosity in the damaged mortar, which likely weakens the physicomechanical properties of the mortar and accelerates the ingress of external deicer solutions. Moreover, the deicer application results in air-void-filling by calcium oxychloride and secondary ettringite, which may reduce the space available to release the internal stresses associated with ice formation and thus compromises the freeze-thaw durability.

Evaluation of the effectiveness of reciprocal and conventional shaping systems and EDDY and CanalBrush activation systems in calcium hydroxide removal

Aim: To compare the effectiveness of two preparation systems and two irrigation techniques in calcium hydroxide removal from straight root canals.
 Methodology: Forty-four mandibular premolar teeth were included in this study. The teeth were filled with a calcium hydroxide-based paste and randomly divided into two different preparation groups (Reciproc 50 (R50; VDW, Munich, Germany and ProTaper Universal F5 (PTU; Dentsply Maillefer, Ballaigues, Switzerland). Subsequently, the groups were divided into two subgroups and irrigated using EDDY (VDW, Munich, Germany) and CanalBrush (CB; Roeko, Langenau, Germany) irrigation activation systems. The percentage of calcium hydroxide removed from the canal walls was analyzed using a dental operating microscope (DOM) at 25× magnification. An independent samples t-test, a Mann–Whitney U, Wilcoxon’s tests were used for statistical analysis.
 Results: There was no significant difference in calcium hydroxide removal throughout the root canal using the R50 and PTU F5 preparation systems (P = 0.847). Both activation systems significantly increased the amount of calcium hydroxide removed from the root canal. Conclusions: EDDY and CB significantly improved calcium hydroxide removal. There was no significant difference between the R50 and PTU F5 systems in calcium hydroxide removal.
 How to cite this article: Keskin NB, İnce Yusufoğlu S. Evaluation of the effectiveness of reciprocal and conventional shaping systems and EDDY and CanalBrush activation systems in calcium hydroxide removal. Int Dent Res 2021;11(1):16-22. https://doi.org/10.5577/intdentres.2021.vol11.no1.4
 
 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Evaluation of the efficacy of XP-endo Finisher, Easy Clean, Passive ultrasonic irrigation, and conventional irrigation in the removal of calcium hydroxide in simulated internal root resorption cavities

This study aimed to evaluate the efficacy of 5 irrigation protocols in removing calcium hydroxide in simulated internal root resorption cavities. Eighteen extracted human teeth, upper anterior and uniradicular, were prepared up to size 50. The teeth were divided longitudinally, and internal root resorption cavities were made by acid demineralization using nitric acid. The same sample was submitted to the five irrigation protocols. The cavities and root canals were filled with Ultracal XS (Ultradent, South Jordan, UT, USA) and stored in an incubator at 37ºC for one week. Afterward, the irrigation protocols were carried out: XP-endo Finisher (XPF; FKG, La Chaux-de-Fonds, Switzerland), passive ultrasonic irrigation (PUI), Easy Clean (Bassi/Easy Equipamentos Odontológicos, Belo Horizonte, Brazil) with reciprocating movement (ECR), Easy Clean with continuous rotation (ECC) and conventional irrigation with a syringe (CI). The solutions used, 2.5% NaOCl, and 17% EDTA, were warmed. The total volume of irrigant used for each sample was 20 mL (10 mL of 2.5% NaOCl, 5 mL of 17% EDTA and 5 mL of distilled water). The amount of calcium hydroxide remaining in the internal resorption after irrigation was assessed using scores. The data were analyzed using the Pearson and Kruskal-Wallis (Dunn) tests. Significantly more calcium hydroxide was removed in the XPF group than all other sample groups (P < 0.0001). XPF was superior to the other methods tested to remove calcium hydroxide in teeth with simulated internal resorptions.

Carbonation Effects and Its Mitigation Measures in Concrete/Cement Mortar Mass Made of Cent Percentage Recycled Coarse and Fine Aggregates

The recycled demolished concrete aggregate obtained from processing unit contains the maximum amount of calcium hydroxide (lime) andthese lime inreaction with atmosphericcarbon dioxide and forming a calcium carbonate and reducing the PH of the aggregatesand making the aggregates mass carbonated. These carbonated aggregates when used in concrete/cement mortar results in intense carbonated mass with PH of the mass less than 9 and thereby damaging the mass and rendering it unfit for its intended use. The research deals with the process and technique dealing with improving the surface and internal structure of the recycled aggregate massobtained from processing plants andmaking it fit for its usage in production of concrete /cement mortar mass and analyzing the process of the carbonation in the concrete/cement mass prepared with conventional and treated and untreated demolished concrete coarse and fine aggregates. The results obtained have shown a surface modificationand surface treatment methods founds to be an effective solution countering the carbonation of the aggregatesand the treatment helps in retaining the hydroxideion concentration (OH-) andits usage in the concrete/cement mortar mass helps in retaining the alkalinity at par with conventional concrete andmakes mass more dense and self resilient

Efficacy of glycolic acid for the removal of calcium hydroxide from simulated internal Resorption cavities.

This study evaluated the efficacy of 5% and 10% glycolic acid solutions for the removal of calcium hydroxide medicament from artificial internal resorption cavities. A total of 170 human maxillary premolars were selected and artificial internal resorption cavities were prepared using round burs and 37% orthophosphoric acid in the apical third of the root halves. Entire canal and resorption cavity were filled with calcium hydroxide paste. Then, the specimens were assigned to 2 control groups or ten experimental groups according to the irrigating solutions used for medicament removal with and without activation with ultrasonic energy as following: 5% glycolic acid, 10% glycolic acid, 17% EDTA, and 10% citric acid and distilled water. The resorption cavities were examined under different magnifications using stereomicroscopy and scanning electron microscopy (SEM). The calcium hydroxide remnants in the resorption cavity were scored by 2 evaluators using a 4-scoring scale. The data were analyzed with Kruskal-Wallis H tests with 5% significance threshold. There was no significant difference regarding the distribution of removal scores among non-activated solutions (P > 0.05). In activated groups, 10% glycolic acid irrigation removed significantly more amount of calcium hydroxide than EDTA and distilled water (P < 0.05). No significant difference was found between the efficacy of 10% glycolic and citric acid (P > 0.05). Citric acid, 5% glycolic acid, and EDTA showed similar removal scores (P > 0.05). Passive ultrasonic irrigation significantly improved calcium hydroxide removal scores in 10% glycolic acid, citric acid, and EDTA groups (P < 0.05). The SEM examination revealed that the specimens that were scored 0 are not entirely free of calcium hydroxide remnants. Concentration of 10% glycolic acid removed significantly more calcium hydroxide paste from resorption cavities than EDTA when used with passive ultrasonic irrigation. Although passive ultrasonic irrigation favored medicament removal in all irrigating solutions, complete elimination of medicament remnants was unattainable. This study showed the improved efficacy of ultrasonically activated 10% glycolic acid in removing the calcium hydroxide medicament from the internal resorption cavity.

Effect of Sugarcane Bagasse Ash as Partial Cement Replacement on the Compressive Strength of Concrete

The disposal of solid waste in open environment is a serious alarming concern that needs immediate attention from the researchers. The hazardous solid agro-industrial wastes which include: wheat straw ash, rice husk ash, corn cob ash and sugarcane bagasse ash (SCBA), having pozzolanic properties, have a versatile use in concrete. The solid pozzolana enhances the various concrete properties by the reaction of silicates with calcium hydroxide in the presence of water, which in result generate a saturated zone of calcium silicate hydrate (CSH) gel. This C-S-H gel reduces the amount of calcium hydroxide C(OH)2 during the hydration process of cement. Very limited research works have been done on concrete by partially replacing cement with SCBA. This research work was focused on evaluating the properties of concrete by partially replacing cement with SCBA at 0, 5, 10, and 15 percentages. Compressive strength, Strength activity index, and water absorption of all mixes were examined. And it was observed that all SCBA mixes showed an increase in compressive strength and at 10% replacement the strength activity index was at a peak of 115.67%, but all the SCBA mixes showed a strength activity index greater than 75% which satisfied the standard specification. The water absorption test for all SCBA mixes showed a slight increase in water absorption.

Effect of calcium hydroxide on the alkali-silica reaction of alkali-activated slag mortars activated by sodium hydroxide

Alkali-silica reaction (ASR) is one of the major durability issues in ordinary Portland cement (OPC) concrete. Previous literature suggested that the alkali-activated slag (AAS) concrete is less susceptible to ASR compared to OPC concrete. This study investigated the effect of calcium hydroxide on the ASR expansion of AAS mortars with the aim to understand the mechanism governing the ASR resistance of the AAS mortars. The ASR expansions of AAS mortars containing different amount of calcium hydroxide were compared with OPC mortars. The investigations on the ASR products, pore solution and the binder were conducted. The results show that the control AAS mortar exhibited innocuous ASR expansion despite of its high pore solution alkalinity. Addition of calcium hydroxide substantially increased the ASR expansion of the AAS mortars and the expansion increment was almost linearly proportional to the amount of calcium hydroxide addition. The results suggest that the deficiency of calcium hydroxide is one controlling factor for the low ASR expansion of the AAS mortars. No obvious difference was observed in the ASR products in all the mortars in terms of morphology and composition, implying that the additional calcium hydroxide may increase the amount of the ASR products in the AAS mortars, as the presence of calcium could facilitate the gelation and formation of the ASR products.

Effect of Blast-Furnace Slag Replacement Ratio and Curing Method on Pore Structure Change after Carbonation on Cement Paste.

The frost damage resistance of blast-furnace slag (BFS) cement is affected by carbonation. Hence, this study investigates the carbonation properties of pastes incorporating BFS with different replacement ratios, such as 15%, 45%, and 65% by weight, and different curing conditions, including air and carbonation. The BFS replacement ratio properties, determined by the Ca/Si ratio of calcium silicate hydrate in the cement paste sample, were experimentally investigated using mercury intrusion porosimetry, X-ray diffraction, and thermal analysis. The experimental investigation of the pore structure revealed that total porosity decreased after carbonation. In addition, the porosity decreased at a higher rate as the BFS replacement rate increased. Results obtained from this study show that the chemical change led to the higher replacement rate of BFS, which produced a higher amount of vaterite. In addition, the lower the Ca/Si ratio, the higher the amount of calcium carbonate originating from calcium silicate hydrate rather than from calcium hydroxide. As a result of the pore structure change, the number of ink-bottle pores was remarkably reduced by carbonation. Comparing the pore structure change in air-cured and carbonation test specimens, it was found that as the replacement rate of BFS increased, the number of pores with a diameter of 100 nm or more also increased. The higher the replacement rate of BFS, the higher the amount of calcium carbonate produced compared with the amount of calcium hydroxide produced during water curing. Due to the generation of calcium carbonate and the change in pores, the overall number of pores decreased as the amount of calcium carbonate increased.

Assessing the pozzolanic activity of sugarcane bagasse ash using X-ray diffraction

This paper proposed to assay the pozzolanic activity of different types of sugarcane bagasse ash (SBA) using the X-ray powder diffraction technique. The as-received SBA presented a high loss on ignition and a coarse particle size, and then, the processing employed calcination and grinding. Pastes and mortars formed with SBA and calcium hydroxide were used for X-ray powder diffraction, thermogravimetric analysis, and compressive tests. The evaluation of the pozzolanic activity was based on the measurement of the calcium hydroxide amount by a relative decrease in peak intensity (RDPI) at 18° and 34° (2θ), RIR, and Rietveld refinement analysis. These results were compared with the data obtained from thermogravimetric analysis and compression tests, and showed good correlation. In the correlation matrix, all p-values were below 0.05, indicating that the variables did not show any independence from each other. Finally, it was concluded that assessing CH consumption only by the RDPI, even considering a low-accuracy method, can be a relevant tool for evaluating the SBA pozzolanic activity.

Using EDTA-2Na to inhibit sulfate attack in slag cement mortar under steam curing

This paper explored a novel method to inhibit sulfate attack in slag cement mortar under steam curing, by using ethylenediaminetetraacetic acid disodium (EDTA-2Na) to chelate calcium ions. 0.5 and 1% EDTA-2Na were used in slag cement mortars to evaluate the inhibition effect in sulfate solution (7.5% Na2SO4 and MgSO4 solution) for 360 days. The weight variation, compressive strength, along with FT-IR spectroscopy, XRD and DTG, were conducted to analyze the sulfate degradation. Additionally, the isothermal calorimetry was measured to study the effect of EDTA-2Na on the hydration of cement. Results indicated that 1% EDTA-2Na retarded the cement hydration distinctly. The EDTA-2Na enhanced the resistance of steam-cured slag mortar against sulfate attack. For the Na2SO4 attack, the enhancing effect of 1% EDTA-2Na was higher than that of 0.5% EDTA-2Na. For the MgSO4 attack, 0.5 and 1% EDTA-2Na was both beneficial. The EDTA-2Na decreased the amount of calcium hydroxide due to the chelation, retarding the formation of gypsum and secondary ettringite.

Effect of microcrystalline and microfibrillated cellulose on the evolution of hydration of cement pastes by thermogravimetry

The interest in the use of cellulose fibers of increasingly smaller sizes in cementitious materials has increased in recent years. This paper brings new contributions in this field showing from respective paste thermal analysis data, how microcrystalline cellulose (MCC) and microfibrillated cellulose (MFC) affect differently the formation of Class G cement pastes hydration products from early (2 h) to later hydration ages (672 h). Pastes containing 0, 0.25 and 0.5% of cellulose per cement mass and a water/cement mass ratio of 0.45 were cured at 23 °C, and the TG/DTG tests were carried out after 2, 6, 12, 24, 168 and 672 h. The results show that the pastes with MCC and MFC additions presented higher total combined water content than the reference paste, especially after 24 h of hydration. However, this is strongly related to the quantity of water adsorbed by different celluloses and their concentrations in the mixture. Comparing cellulose pastes, MFC pastes showed lower total combined water up to 28 days, attributed to the fiber’s microfibrillar form. No higher amount of calcium hydroxide was formed in the presence of cellulose, but it was more crystalline than that obtained in the reference. Other hydrated phases (dehydration from 200 to 400 °C) are differently affected by the presence of the celluloses, the highest formation occurring for 0.25% MCC paste. This behavior was attributed to an additional cure of these mixtures related to morphological characteristics and water retention capacity of cellulose.

Root-end restoration using MTA against the intractable cases of root canal treatment

Root-end restoration using Mineral Trioxide Aggregate (MTA) was performed on two patients who received root canal treatment but had poor progress. In one case, a large amount of Calcium hydroxide(Ca (OH)2), a intracanal medicament, escaped from a wide-open apex, stagnated around the tooth root, and the apical lesion did not disappear. The other case is a case where the root canal at the apical part has a complicated anatomical form, the root canal cannot be tightly packed, and the apical lesion has not disappeared. Root-end restoration using MTA was performed on these two cases, and improvement of the lesion was confirmed. From these results, it was shown that Root-end restoration using MTA is effective for patients with poor prognosis of root canal treatment for which the apical portion cannot be tightly packed for various reasons. Keywords: Mineral Trioxide Aggregate; MTA; Root-end restoration

Effects of Single and Compound Electrolyte Electrolyzed Cathode Waters on Mechanical Property and Hydration Reaction of Concrete

In this study, two kinds of different electrolyzed cathode water were used to prepare the concrete, the effects on mechanical property and hydration reaction of concrete were determined ultimately. Taking the influence of air-entraining admixture into consideration, the blank control test was also conducted. The experiment results showed that the single and compound electrolyte electrolyzed water both can effectively improve the strength of ordinary concrete, and the differences in strength between these two kinds of electrolyzed water concrete were not significant. To a small extent, the air-entraining admixtures would affect the activity of electrolyzed water and decrease the growth ratio of strength due to resistance effect. TG/DTA results test showed the calcium hydroxide amount of electrolyzed water concrete was obviously higher than that of natural tap water concrete at each age. In other words, the electrolyzed water in concrete can promote and boost the hydration reaction to produce more C–S–H gels and calcium hydroxide, leading to strength improvement and porosity reduction of concrete. In addition, the influence of the reaction between CO2–3 ions in electrolyzed water and calcium hydroxide on the increase of strength was little.

Cement-based composites with waste expanded perlite - Structure, mechanical properties and durability in chloride and sulphate environments

Implementation of fine, dusty materials generated during the production of expanded perlite is a challenge from the waste disposal point of view. However, after proper treatment, it is possible to use them in the composite building materials manufacturing where they can play a role of so-called pozzolanic additive, strengthening setting and hardening process when mixed with cement. In this study waste expanded perlite – Portland cement composites were exposed to the action of sodium chloride, sodium sulphate and magnesium sulphate solution. The results show that the durability of cement composites with waste expanded perlite is significantly improved; the lifecycle of these materials would be markedly enhanced. Due to the pozzolanic reaction between the vitreous aluminosilicate component of perlite and calcium hydroxide released from cement clinker, the phase assemblage of hardened cement matrix is changed towards the partial replacement of calcium hydroxide by the C-S-H phase. The amount of calcium hydroxide is therefore markedly reduced, as well as the pore refinement and compact microstructure of products is observed. As a consequence, the compressive strength increases, the permeability of final material decreases. Therefore the durability of Portland cement - perlite mortars is significantly improved. The reference mortars with cement subjected to the sodium and magnesium sulphate started to expand after 200 and 100 days of curing respectively. They were destroyed after about a year, while the samples containing 20% of WEP exhibited no expansion after 5 years of storage in corrosive solutions.

The Threshold Value of Effective Replacement Ratio of Fly Ash Mortar Based on Amount of Calcium Hydroxide

The effective mineral admixture in mortar can consume the calcium hydroxide produced by hydration reaction because of pozzolanic effect. For high volume mineral admixture mortar, when the replacement ratio exceeds a certain ‘threshold’ value, the supply of Ca(OH)2 amount is insufficient, the superfluous and ineffective mineral admixture will no longer react in mortar but as fine aggregate. This study presents an experiment study on the threshold value of effective replacement ratio of fly ash mortar by the comprehensive analysis of Ca(OH)2 amount and consumption curves. Under the conditions of different curing temperature, the effective replacement ratios of fly ash mortar have been determined ultimately. The results showed that Ca(OH)2 amount and consumption in mortar both decreased with replacement ratio. For fly ash mortar, at 20°C curing temperature, when the replacement ratio was less than 40%, the Ca(OH)2 amount decreased obviously with replacement ratio. However, when replacement ratio was more than 40%, Ca(OH)2 amount at 91d changed slightly with replacement ratio, the Ca(OH)2 amount was consumed to a limit value at this time. Under the condition of 30°C curing temperature, when the replacement ratio exceeded 30%, the change of Ca(OH)2 amount with replacement ratio was close to a straight line, the superfluous fly ash no longer consumed Ca(OH)2 basically. Moreover, the consumption of Ca(OH)2 was not much difference to the Ca(OH)2 amount at the same replacement ratio under the condition of 20°C curing temperature. This result has a great significance on effective utilization of mineral admixtures in engineering application.

Thermal Properties of Alkali Activated Slag Plaster for Wooden Structures

Currently, the production of green building materials grows up. Alkali-activated materials (AAMs) based plaster have better fire resistance properties compared to Portland cement-based concrete and plasters. Compared to Portland cement-based systems AAMs retain a significant level of structural stability after exposure to fire events. AAM based concrete doesn’t have at all or has an insignificant amount of calcium hydroxide in the binder structure which exposed to high-temperature changes to calcium oxide. This weakens Portland cement structural properties and allows cracks to appear under high-temperature conditions. This study shows that AAM based plaster that consisted of alkali-activated ground granulated blast furnace slag (slag) with the addition of Phosphogypsum (PG), sand and polypropylene fibre filling exposed to 1000 °C temperature shows up to 2% longitudinal dimension shrinkage. After exposure of elevated temperature these fibers melted leaving a network of channels that allow water vapour vaporize and inner pressure in the material decreased. The start of the wood surface charring process tch is 10 minutes after the start of heating. Using an AAM binder as fire-resistant plaster coating on a wooden structure delays the start of the char layer forming on the wood surface. This allows using AAMs base plaster for fire-resistant coatings on combustible materials as the barrier layer in order to increase the passive safety of wooden structures in heritage buildings.

Isoconversional kinetic analysis of decomposition of bastnaesite concentrates with calcium hydroxide

Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added. The apparent activation energy was calculated, and the results indicate that the overall reaction involves more than one single step. The reaction with a lower content (<15 wt%) of calcium hydroxide can be divided into two steps, while the reaction with a higher content (>15 wt%) involves another step which denotes the decomposition of newly formed calcium carbonate during roasting. The activation energy increases with increasing amount of calcium hydroxide in the lower range (0–15 wt%). This is due to the resistance of calcium hydroxide to heat and mass transport. However, more calcium can promote the decomposition reaction more effectively and thus reduce the activation energy. Nonlinear fitting was performed by fitting the experimental data to Avrami-Erofeev model to determine the reaction model and pre-exponential factor. The theoretical models were proven to be reliable for kinetic prediction.

Mechanical Properties and Chemical Characterization of Mortars with Halloysite Nanoclay after Exposure to Elevated Temperatures

Abstract In this study, the effects of halloysite nanoclay (HNC) on cement mortars after exposure to elevated temperatures were investigated. The compressive strength, microstructure, and chemical composition of mortars with 0 %, 1 %, 2 %, and 3 % HNC were compared after exposure to temperatures of up to 1,000°C. Also, the materials analysis using diffraction program was used to analyze the X-ray powder diffraction data based on the Rietveld method. Test results revealed that the HNC samples maintained higher strength of up to 10 % at elevated temperatures when compared to plain mortars. An increase in the relative elastic modulus and a higher energy absorption rate were also observed when the HNC was added. It is safe to state that the HNC had an interlocking effect by which it obstructed the heat-induced microcracks. Furthermore, the quantitative analysis showed that the HNC lowered the calcium hydroxide amount and increased/accelerated the hydration of alite and belite in the matrix.