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Abstract Natural-based materials represent green choices for biomedical applications. In this study, resin pulp capping restoration enclosing strengthening silica and bioactive portlandite nanofillers were prepared from industrial wastes. Silica nanoparticles were isolated from rice husk by heat treatment, followed by dissolution/precipitation treatment. Portlandite nanoparticles were prepared by calcination of carbonated lime waste followed by ultrasonic treatment. Both were characterized using x-ray diffraction, energy dispersive x-ray, and transmission electron microscopy. For preparing pulp capping restoration, silica (after silanization) and/or portlandite nanoparticles were mixed with 40/60 weight ratio of bisphenol A-glycidyl methacrylate and triethylene glycol dimethacrylate. Groups A, B, and C enclosing 50 wt.% silica, 25 wt.% silica + 25 wt.% portlandite, and 50 wt.% portlandite, respectively, were prepared. All groups underwent microhardness, compressive strength, calcium release, pH, and apatite forming ability inspection in comparison to mineral trioxide aggregate (MTA) positive control. In comparison to MTA, all experimental groups showed significantly higher compressive strength, group B showed comparable microhardness, and group C showed significantly higher calcium release. Groups B and C showed prominent hydroxyapatite formation. Thus, the preparation of economic, silica-fortified, bioactive pulp capping material from under-utilized agricultural residues (rice husk) and zero-value industrial waste (carbonated lime from sugar industry) could be achieved.

The present study evaluates the impact of calcium compounds on the reaction kinetics of alkali-activated construction demolition waste. Two materials, concrete and brick demolition waste, were milled to powders and supplemented with either carbonated cement stone or freshly ground cement stone. The mixed solids were further subjected to alkaline activation using a sodium silicate solution. X-ray diffraction, isothermal conduction calorimetry, thermogravimetric analysis, scanning electron microscopy and compressive strength tests were employed to understand the interaction of the reactants. The results indicate that cubes prepared from freshly ground cement stone exhibited higher compressive strength of around 18 MPa than those from carbonated cement stone with a maximum of 7 MPa. This superior strength was approved by subsequent analysis methods. A more significant reaction was observed in the material containing freshly ground cement stone, resulting in increased strength within the system. The presence of portlandite in freshly ground cement stone facilitated the initial formation of calcium silicate hydrate phases.

This research investigated the influence of using chemically treated glass microparticles as a partial replacement for cement in Portland cement pastes and mortars. The microparticles were obtained by grinding glass waste into three different particle size fractions (< 75 µm, < 45 µm, and < 25 µm), treated with calcium hydroxide (CH), and characterized using SEM/EDS and a laser particle size analyzer. Samples prepared with the incorporation of glass were characterized using XRD, TGA/DTG, and SEM/EDS. The pretreatment with calcium hydroxide induced the formation of C-S-H with different morphologies on the surface of the particles, in addition to causing changes in particle size distribution due to the formation of agglomerates. The pastes prepared with treated particles had lower amounts of CH and higher levels of hydrated silicates. However, when indirectly measuring the pozzolanicity of treated particles through the compressive strength of mortars, no significant differences were observed in the strengths of mortars made with treated and untreated particles.

The carbonation of recycled concrete aggregates (RCA) has emerged as a possible significant carbon sink to mitigate the increase of CO2 concentration in atmosphere and global warming. A reliable determination of bound CO2 content is thus needed to optimize carbonation processes but there is no real consensus on the existing quantification methods, mainly based on thermal decomposition of calcium carbonate. With the aim of developing a relevant quantification method of bound CO2 during the carbonation of RCA, an experimental study based on the combination of two main techniques – thermogravimetric analysis (TGA) and high-temperature oven – was performed at different scales: paste, mortar, and concrete. XRD analyses allowed highlighting the overlaps between the decomposition of portlandite and calcium carbonate polymorphs during linearly increasing temperatures. Oven and TGA with isothermal steps were found to provide consistent and complementary data on RCA composition and their bound CO2 content from initially dried specimens.

The use of high percentages of substitution of Portland cement by pozzolans can provoke the total consumption of portlandite. The present research proposes the study of ternary systems of Portland cement (PC), fly ash (FA), and hydrated lime (CH). After 180 days of curing, the mortar with 50% substitution of PC by FA obtained 65.9 MPa versus the mortars with an addition of 20% of CH and control mortar (100 PC) that obtained 69.9 MPa and 76.7 MPa respectively: this behavior is very positive value considering that tested FA containing mortars had a 50% of Portland cement. Regarding the effect of the amount of extra hydrated lime on durability issues, the evolution against carbonation of PC-FA and PC-CH-FA mortars was studied: the reduction of carbonation velocity was around a 37% for the mortar with CH respect the PC-FA mortar.

In this study, nano-structural and nano-constraints behavior of two silica aggregate mortars are investigated. The first silica aggregate (A) is almost pure silica and the second one (B) contains silica, calcite and dolomite phases. The relationship between the durability and nano-structural changes is evidenced using Transmission Electron Microscope, X-ray diffraction (XRD) and TGA/DTA. The nano-structural results show that the macroscopic properties of mortars greatly depend on physico-chemical properties of aggregates. Higher the water absorption, higher the consumption of the Portlandite; the consumption of Portlandite, after 28 days of curing, is more in Bm sample than in Am sample. A relationship between the Portlandite content and the water absorption is evidenced. The relationship between reactivity and nano-constraints deduced from XRD modeling is highlighted.

Introduction. Construction of large-scale offshore structures in the coastal area of Vietnam requires new compositions of binders for hydraulic concretes, advanced concrete mixing technologies, and concrete transportation to depositing sites.Materials and methods. The binder, containing sulfate resistant Portland cement and finely dispersed mineral additives, including low calcium fly ash of TPP “Vung Ang” and silica fume SF-90 (SF-90), was added to the mortar mix, and the same about SR 5000F superplasticizer and quartz river sand. Powder particle shape and size were measured using laser granulometry; X-ray diffraction was employed to identify the mineral composition of sulfate-resistant cement; the effect of multi-component organo-mineral additives on the phase composition of the cement stone was studied using methods of thermogravimetric analysis; the absolute volume method was employed to analyze the composition of the mortar.Results. The co-authors have analyzed the application of new compositions of multi-component organic-mineral additives whose content, if taken as a percentage of the cement weight, reaches 1.1-1.45 % of SF 5000F superplasticizer, 10-15 % of SF-90, and 30 % of fly ash. New additives accelerate compressive and tensile strength development by 1.4-1.9 times, and that’s been confirmed by bending early-age and 28-day cement-sand mortar specimens, that have sulfate-resistant cement, and their benchmarking against control specimens. It’s been identified that SF-90 and fly ash, if added to the mix, reduce the Portlandite content in the cement stone by 1.27-3.29 % at the age of 28 days in comparison with the benchmark composition due to their high pozzolanic activity.Conclusions. Testing results enable co-authors to recommend the application of multi-component organo-mineral additives to increase the resistance of cement-sand compositions to sulfate corrosion due to the denser structure and lower porosity of the cement stone, caused by the lower value of the water/binder ratio and the packing of pore spaces with active mineral fillers. Therefore, new additives are recommended for use in the production of corrosion resistant concretes suitable for construction of offshore hydraulic structures in Vietnam.

The landfill disposal of waste newspapers has triggered an environmental concern that must be addressed. The ink from the waste newspaper is toxic and could be leached out of the waste newspapers by rainwater at landfill sites, causing water contamination. This contributed to the degradation of aquatic ecosystems. In another environmental problem, cement manufacturing resulted in a large emission of carbon dioxide into the air. Considering all these issues, it is necessary to investigate waste newspaper ash as a supplementary cementing material in concrete cylinders for cleaner production. The waste newspaper ash was produced by incineration in an electric furnace at 800 °C for 1 h before it was cooled down and sieved. Based on the ACI 211.1–91 standard, two sets of concrete cylinders were cast, namely control and waste newspaper ash treated concrete cylinders; each having a size of 150 mm diameter × 300 mm height. They were cured in water for 3 to 90 days before being tested for their mechanical and chemical properties. The mix design of 7.5% waste newspaper ash as partial cement replacement in the treated concrete cylinders was found to be the optimal one. The optimally treated concrete cylinder was tested to have an average 28-day compressive strength of 33.28 MPa, which is 2.15 MPa lower than the control ones. At 90-day curing age, however, its average compressive strength value was traced to be 44.06 MPa, which is 3.17 MPa higher than the control ones. Investigation of the surface morphology and X-ray diffraction patterns of the treated concrete cylinder samples revealed that there was a progressive pore refinement and a continuous decrease in portlandite when the curing age was prolonged from 28 to 90 days. Inspection of a failed 90-day optimally treated concrete cylinder revealed that it had higher stiffness and fewer extreme macrocracks compared to that cured in 28 days. These positive outcomes pointed out that the pozzolanic reaction in the optimally treated concrete cylinders was pronounced at 90-day curing age and added to their strength improvement in the long term.

Cement paste hydration is a complex physical-chemical process. The aim of this paper is to use three approaches to determine the degree of hydration: portlandite quantification, scanning electron microscopy and bound water quantification. In order to investigate the physical-chemical and mechanical properties, as well as the hydrates generated. Portland cement was synthesized and characterized in the laboratory. At all hydration durations, the portlandite quantification method and SEM-BSE image analysis show similar results. The method of SEM images analysis requires time to gather and process images, but is unaffected by the type of hydrates produced. The bound water quantification method gives a lower degree of hydration than two other methods at all hydration times. To test the reliability of these procedures, the compressive strength was calculated based on the degree of hydration. The results indicate that the portlandite quantification method and SEM-BSE image analysis are more accurate than the bound water quantification approach in terms of reproducing the experimental results.

Comparison of the content of Ca(OH)2 in hardened cement matrices, which contains the additive SiO2 nanoparticles and in matrice without additives was performed by the method of thermogravimetric analysis. Alite portland cement «SsangYong» and «Denki» were used. Hydrothermal sol of «Geosil» was introduced as an additive of nanoparticles of SiO2. The amount of introduced nano-SiO2 was from 1.15 to 1.74 wt.% in respect to cement consumption. Water-cement ratio was provided at the level of W/C = 0.39–0.26. The compensating amount of polycarboxylate SVC-5Neu was 0.2–0.77 wt. %. The Ca(OH)2 content was calculated from the mass loss of the cement matrice sample in the temperature range 460–510о C. It was determined that the sol «Geosil» additive reacts quickly with Ca(OH)2 (CH) in cement matrice, significantly (up to 40%) reducing its content. By the period of 24 h sol «Geosil» binds 750 [mg CaO /g SiO2 ] and continues to bind CH up to 100–700 days, to the value δCaO = 1300 [mg CaO /g SiO2 ]. The pozzolan binding reaction Ca(OH)2 with the formation of calcium hydrosilicates may be one of the mechanisms for increasing the strength of concrete when introducing SiO2 nanoparticles.

Determining the age of ancient architectural and cultural monuments is a significant scientific problem. An approach based on the transformation of portlandite into calcite and subsequent recrystallization of calcite is considered, which allows for estimating the relative age of ancient brickworks for local groups of historic buildings based on the results of diffraction studies of powder samples of carbonate mortars and measurements of samples with a known age. This article presents the results of the study of lime mortars of ancient brickwork. Under natural conditions, the process of transformation of portlandite into calcite takes from 100 to 200 years. The rate of this process is influenced by temperature, humidity, peculiarities of interaction with carbon dioxide contained in the air, etc. Examples show that portlandite is completely transformed into calcite in masonry mortars of the 18th century and that portlandite is not found in older mortars. It was determined that after the transformation of portlandite into calcite, an increase in the degree of recrystallization of calcite is observed, which manifests itself in powder diffraction patterns in the relative broadening of the diffraction peak of calcite hkl 104. In a detailed study, an estimate of the peak width at half maximum (FWHM) associated with the degree of crystallinity is effective. The actual data are given, which show that in older lime mortars the degree of recrystallization of calcite is higher than in younger ones. This fact makes it possible to indirectly determine the relative age of brickwork and masonry of various buildings of architectural heritage, which is especially relevant for the objects with the use of lime mortars of the northern provinces of the Byzantine Oecumene and other periods of various cultures.

Supplementary cementitious materials (SCMs) prove to be effective to meet most of the requirements of durable concrete and leads to a significant reduction in CO2 emissions. This research studies the effect different SCMs (natural pozzolan (PN)/ limestone fine (FC) at various remplacement levels) on the physical and mechano-chemical resistance of blended mortar. The paper primarily deals with the characteristics of these materials, including heat of hydration, strength and effects of aggressive chemical environments (using sulphuric acid and nitric acid). Over 6 mixes were made and compared to the control mix. Tests were conducted at different ages up to 360 days. The experimental results in general showed that Algerian mineral admixtures (PN/FC) were less vulnerable to nitric and sulphuric acid attack and improved the properties of mortars, but at different rates depending on the quantity of binder.

The results of studying the effect of the vibration processing time on the size of calcium hydroxide particles are given. The physicochemical processes affecting the size and morphology of calcium hydroxide particles have been studied. A stage-by-stage mechanism of the process of the carbonation of lime, depending on its specific surface, is established. The results show that the optimal period for the vibration treatment of lime to obtain the most active material is 20 min. A longer period of vibration results in the merging of particles into larger agglomerates.

Calcium hydroxide, a crystal involved in the cycle of calcination and carbonation of calcium oxide, finds several applications from cultural heritage to the dentistry branch or to the construction industry. When excited at 1064 nm, Raman spectra of calcium hydroxide show a broad composite band peaked at about 780 cm−1, corresponding to 1170 nm. Since it is not observed with visible excitation, the origin of this band is debated, being assigned to some pre-existent luminescent impurities or some structural defect of the lime formed after the synthesis of the material. To shed light on the formation of this band, we synthetised the lime paste starting from pure calcite powders. The obtained fresh Ca(OH)2 samples did not show any band in the investigated range, irrespective of the laser excitation applied. A detailed analysis of the excitation and emission spectra in the near infrared region did not show the 1170 nm band, supporting the hypothesis of a post-synthesis origin. Thus, we carried out thermal treatments at different temperatures (90–500 °C) and under different environments (in air or under nitrogen flux) on synthesised fresh Ca(OH)2 powders. We also investigated the time evolution of the samples, monitoring the Raman spectra over 90 days after a specific treatment. The collected data support the hypothesis of a defect-related luminescence centre, whose formation depends on the temperature and environment of the treatment, which appears as a preferential site for the carbonation process of the calcium hydroxide. These results can be useful in the field of Cultural Heritage for dating purposes, and to determine the conservation state of Ca(OH)2 containing relics to prevent the possible activation of degradation processes.

In this paper, thermal behavior of calcite as raw material of CaO-based expansive agent was investigated. The products were characterized by using differential thermal analysis (DTA), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR) and X-ray powder diffraction (XRD). DTA curves show that calcite has endothermic peak and impurity affects the onset of reactions. The more the impurity increases, the more energy changes increase. At 800-900°C, calcite was decomposed into solid calcium oxide (CaO) and gaseous CO2. Lime (CaO) used as the base of expandable material is the ultimate product of heated calcite. The calcium oxide phase, in reaction to water forms portlandite, at an onset temperature of about 900°C was also characterized by the appearance of the FT-IR mode at 867,3424 and 3644 cm-1. XRD results show that quartz impurity in calcite samples at 900°C forms larnite phase (Ca2SiO4). The expansions are mainly generated from the hydrations of CaO in the CaO-type expansive agent.

Abstract Industrial wastes from pulp and paper mills are potentially useful materials to use as alternative materials in clinker production. In this study, eco-friendly clinkers were obtained using only waste as feedstock. Eco-friendly clinker with different C3S and C2S contents were produced and hydrated for 7 days at 40 °C, or for 28 and 90 days at room temperature. The potentialities of these waste and the products obtained were revealed through chemical (XRF), thermal (DTA/TG) and surface area (BET) analysis. For comparison, a common ordinary Portland cement (OPC) was tested. As expected, the hydration rate of formulations presenting higher C3S content was higher, generating higher amounts of Ca(OH)2. Furthermore, the amount of Portlandite formed was lower when compared to OPC.