Reaction Of Lime Research Articles

Performance and microstructure development of lime – calcined fluvial sediment binders under different curing conditions

Fluvial sediments need to be periodically dredged from waterways. At the same time, the building sector has to find high-volume alternatives to the extraction of non-renewable mineral resources. In this context, recent research has shown the benefit of reusing calcined sediments as supplementary cementitious materials. On a different note, this study examines the hydration and performance of blends of calcined fluvial sediment with low amounts (10 to 30 wt%) of hydrated lime with the aim of keeping the carbon footprint of the binder the lowest as possible. The effect of different curing conditions (moist curing at 20 °C or 50 °C and dry curing at 65%RH) is studied on compressive strength, reaction kinetics (fixed lime by TGA and heat of hydration), reaction products (XRD), microstructure (SEM) and porosity (MIP). The outcomes of the study revealed that heat curing for 3 days and 10 wt% of lime results in satisfactory strength development for the design of bio-based concretes (compressive strength of 9 MPa). Furthermore, the highest compressive strength of 17.5 MPa was achieved at 110 days at 20 °C for the mix with 20 wt% of lime. The amount of unreacted lime was found to be the highest for the mix including 30 wt% of lime for which the degree of reaction of lime at 90 days was around 0.7 for both curing temperatures. Under dry curing, a large part of the initially available lime was carbonated and some reaction products underwent carbonation leading to very low strength by 110 days.

Experimental Study on the Cracking and Mechanical Properties of Lime Soil with Different Slaking Conditions of Newly Repaired Earthen City Walls.

In this paper, a method to control the lime reaction by different slaking conditions is proposed to reduce the occurrence of cracks in newly repaired earthen city walls. The effects and mechanisms of the slaking time (0 h, 12 h, 24 h, 48 h and 72 h), lime content (10%, 15% and 20%), and moisture content (14%, 18% and 22%) on the cracking and mechanical properties of lime soil were analyzed by the test results of surface cracks, triaxial compression, particle gradation, pH value, X-ray diffraction and scanning electron microscope. The results show that proper slaking of lime soil specimens can reduce surface cracks and improve mechanical properties. After 12 h of appropriate slaking, the crack rate of the lime soil with 20% content decreased by 97.13%, the cohesion increased by 20.27%, and the internal friction angle decreased by 11.27%. However, the mechanical properties decreased when the slaking time was too long. After 72 h of slaking, the cohesion of 20% lime soil decreased by 8.21% and the internal friction angle increased by 2.82%. Further analysis shows that the appropriate slaking conditions can regulate the reaction rate and alkali environment, control the lime produced cementitious substances, improve the particle gradation and further reduce the occurrence of surface cracks. These results provide a basis for the restoration technology of newly repaired earthen city walls.

Strength and durability properties of concrete using incinerated biomedical waste ash

Biomedical waste is a collection of medical waste from diverse sources that pose a major risk to human, plant, or animal life now or in the future. It cannot be processed or discarded off without proper processing. Biomedical waste is often burnt in incineration plants, yielding Incinerated Biomedical Waste Ash (IBMW) which is disposed off in landfills, which are not completely leak-proof. The impact of IBMW ash as cement replacement on the strength and permeability properties of concrete is discussed in this research. For comparison, a control concrete mix is created, as well as five concrete mixes with varying percentages of IBMW (2.5, 5.0, 7.5, 10 and 12.5%). Lime reactivity test suggests marginal pozzolanic activity of IBMW. The experimental study results suggest that including 7.5% IBMW as a partial cement replacement improves the compressive strength by 20%; improves the split tensile strength by 17% and flexural strength by 14% compared to control mix in 28 days. Compressive, split tensile and flexural strength tests is performed up to 90 days of age, and water absorption, sorptivity, and leachate analyses is performed up to 28 days of age. The Toxicity Characteristic Leaching Procedure (TCLP) test was also carried out and is discussed.

Linking small-strain stiffness to development of chemical reactions in lime-treated soils

In the context of lime stabilization, this note shows how the development of soil–lime reactions can be linked to the variation of small shear stiffness with time. To determine the evolution of small-strain stiffness, the shear wave velocity was measured by means of bender elements (BE) on a compacted clayey soil treated with 3% quicklime, starting form 2 h after compaction until 98 days of curing. Different methods of signal interpretation were applied with the purpose of highlighting how the peculiarity of lime treated soils affects BE testing results and to provide practical indications for optimizing similar testing on lime-treated soils. The results showed that lime treatment and compaction affect the waveform of the received signal and that measurements should span across a wide range of input frequencies in order to identify an optimal waveform. The small strain shear modulus was found to increase with curing time with a trend that can be related to that of soil–lime chemical reactions, thus representing a promising parameter to monitor the development of soil–lime reactions.

Critical assessment of rapid methods to qualify supplementary cementitious materials for use in concrete

In this study, several tests for supplementary cementitious materials (SCMs) were evaluated to find the best methods to rapidly screen out inert materials, measure overall reactivity, and differentiate between pozzolanicity and latent hydraulicity. The R3 matrix and lime reactivity tests were found to be the most effective at quickly screening out inert materials. However, slow-reacting materials may appear to have low reactivity in both tests and extending the test duration better depicts material reactivity. Additionally, SCMs with higher alumina content perform better in the R3 tests due to the higher heat release and more bound water associated with the formation of calcium aluminate hydrates compared to calcium silicate hydrates, creating reactivity bias when compared to SCMs with lower alumina content. Measuring the calcium hydroxide content of R3 pastes, through thermogravimetric analysis or single point mass loss, can also differentiate between pozzolanic and hydraulic materials.

Effects of process variables on the reactivity of slaked lime produced from Shuk quicklime

This is a research report of the effects of process variables on the reactivity of slaked lime produced from Shuk quicklime. It involved the calcination (at temperature of 1000 0C, particle size of 90 µm and time of 3 hrs) of Shuk limestone and subsequent slaking of its quicklime. The quicklime was characterized by x-ray diffractometer (XRD) and scanning electron microscopy (SEM) respectively to determine its mineral content and surface morphology respectively. Effects of process variables (quicklime/water ratio, particle size and time) on the reactivity of the slaked lime were determined. The reactivity was optimized using response surface methodology (RSM). The XRD analysis revealed calcite as the type mineral of the Shuk quicklime. The surface morphology of the quicklime sample showed that the particles are packed together in powdered form with visible pores that will allow passage of water. Reactivity of the lime was influenced by the quicklime/water ratio, particle size and time. Quadratic model appropriately explained the relationship between reactivity and considered slaking factors of quicklime/water ratio, particle size and time. The optimum reactivity value of the slaked lime was obtained as 59.3 oC at quicklime/water ratio of 0.24 g/ml, particle size of 88.2 µm and time of 15.1 minutes.

Effects of process variables on the reactivity of slaked lime produced from Shuk quicklime

Effects of process variables on the reactivity of slaked lime produced from Shuk quicklime

Reactive, Sparingly Soluble Calcined Magnesia, Tailor-Made as the Reactive Material for Heavy Metal Removal from Contaminated Groundwater Using Permeable Reactive Barrier

A laboratory method was designed and verified that allows for the testing of alkaline, magnesite-based reactive materials for permeable reactive barriers (PRBs) to remove heavy metals from contaminated groundwater. It was found that caustic calcined magnesia (CCM) with high reactivity and low solubility to remove Cu2+, Zn2+, Ni2+, and Mn2+ cations from mixed aqueous solutions can be prepared by calcination at a suitable temperature and residence time. Regarding the solubility of both the reactive material itself and the precipitates formed, the CCM should contain just a limited content of lime. One way is the calcination of a ferroan magnesite at temperatures above 1000 °C. However, the decrease in pH is accompanied by lower efficiency, attributed to the solid-phase reactions of free lime. A different way is the calcination of magnesite under the conditions when CaCO3 is not thermally decomposed. The virtually complete removal of the heavy metals from the model solution was achieved using the CCM characterised by the fraction of carbonates decomposed of approximately 80% and with the highest specific surface area. CCM calcined at higher temperatures could also be used, but this would be associated with higher consumption of crude magnesite. Under the conditions considered in the present work, the product obtained by the calcination at 750 °C for 3 h appeared to be optimal. The full heavy metal removal was observed in this case using less magnesite, and, moreover, at a lower temperature (resulting, therefore, in a lower consumption of energy for the calcination and material handling).

Properties Affecting the Reactivity of Lime

Lime reactivity is the most used identification parameter for lime quality. The reaction may vary in its rate and maximum reached temperature. In this study, the influence of the properties of limestone on the course of the reaction is studied. The samples are thoroughly examined from a geological point of view (geological age and origin, genesis and diagenesis) and their physicochemical properties are described (total porosity, limestone category, chemical analysis, insoluble residue). Different temperatures and isothermal loads were selected to study the effect of the burning process on the lime microstructure. The newly formed CaO is observed by scanning electron microscopy (SEM images). Lime reactivity analysis is performed, and different reaction courses are compared.

Decomposition of Crystalline Limestones during the Burning Process

The decomposition of limestone during the firing process is mainly based on the decarbonation of CaCO3. In the case of crystalline limestone, it is the decomposition of calcite crystals. In this study, different limestone properties on the course of decarbonation are studied. Therefore, the samples are determined from a geological and physicochemical point of view (geological age and origin, total porosity, limestone category, chemical analyses and insoluble residue). After thorough identification of the samples, various analyses focused on limestone and lime microstructure are performed, such as SEM image analysis or lime reactivity. For these analyses, the samples are burned at different temperatures. The decrepitation amount of limestones during burning process is determined.

Bacteria fixing CO2 to enhance the volume stability of ground steel slag powder as a component of cement-based materials aiming at clean production

Steel slag is a by-product in the process of steel manufacture. It has caused huge environmental pressure. The use of steel slag as the admixture of cement-based materials is an effective way to enhance clean production. But the poor volume stability caused by dead burned lime and periclase in steel slag is a crucial factor restricting its utilization. Some research has shown that carbonization could convert dead burned lime and periclase into carbonate. But the carbonization rate and carbonization degree were low. The objective of this paper is to adopt Bacillus Mucilaginosus (BM) to absorb carbon dioxide to promote the carbonization of dead burned lime and periclase, thereby enhancing steel slag utilization in cement-based materials. The effects of BM on the carbonization rate and degree of dead burned lime and periclase were studied by conducting experiments; the influence of BM on the stability of steel slag mortar with different particle sizes was studied. The results show that BM can reduce the apparent activation energy of the carbonization reaction of dead burnt lime and periclase, and increase the reaction rate and maximum reactivity. MIP (Mercury Intrusion Porosimetry) analysis found that steel slag mortar specimen with BM had a lower porosity than that without BM. The autoclaved linear expansion rate of the steel slag mortar specimen with BM can meet standard requirements while that without BM cannot. It is indicated that the addition of BM can effectively promote the carbonization of dead burned lime and periclase in steel slag and solve the problem of poor volume stability of cement-based materials caused by steel slag. This research helps to improve the utilization of steel slag as an alternative binder to cement and alleviates the environmental pressure caused by the storage of waste steel slag.

Geotechnical Properties and Microstructure of a Diesel Contaminated Lateritic Soil Treated with Lime

ABSTRACT Studies involving oil-contaminated lateritic fine-grained soils are still scarce in literature, especially regarding treatments for improving soils mechanical properties. In this study, geotechnical properties and microstructure of a diesel-contaminated lateritic soil treated with lime are investigated and compared to tests conducted on lime-treated soil (2% to 8% lime) and diesel-contaminated soil (2 to16% diesel). The presence of diesel had no significant effect on soil plasticity but decreased soil strength. Lime stabilization applied to diesel-contaminated soils significantly improved soil properties after 6% of lime stabilizer. The diesel presence led to an inhibition of lime reaction due to reduction of cation exchange capacity and flocculation, which reflected in loss of its effectiveness in improving strength as compared to natural soil response. The water retention behavior and unsaturated hydraulic conductivity of soil were affected by diesel contamination, leading to curve shapes similar to clay materials. Adding 2% of lime to the contaminated soil, increase in the soil pores and changes in the shapes of water retention curve and k-functions were observed with similar behavior of a course-grained material. Overall, this study highlights how the presence of diesel and lime affects lateritic soil properties and microstructure.

Evolution of physicochemical properties of quick lime at converter-smelting temperature

Abstract The volume stability caused by the hydration of f-CaO is one of the main obstacles to the comprehensive utilization of steel-making slag. In view of the f-CaO produced by incomplete dissolution of lime, it is necessary to strengthen the dissolution behavior of lime in the converter process. The reactivity of lime determines the dissolution efficiency and is closely related to its microstructure. The experimental results show that the reactivity and porosity of quick lime decrease and the average diameter of pore increases with an increase in temperature. The CaO crystals gradually grow up under the action of grain boundary migration. When the temperature increased from 1,350 to 1,600°C, the lime reactivity decreased from 237.60 to 40.60 mL, the porosity decreased from 30.55 to 15.91%, the average pore diameter increased from 159.10 to 1471.80 nm, and the average CaO particle size increased from 0.33 to 9.61 µm. The results indicate that reactivity is decreased because of the deformation and growth of CaO crystals and the decrease in porosity in reactive lime. This will cause an obstacle to the dissolution of lime and is not conducive to the control of f-CaO in slag.

Reaction of Converter Slag with Supercritical Carbon Dioxide and Its Potential Applicability as Aggregate for Concrete

The presence of free lime and periclase in converter slag prevents it from directly being utilized as a source of concrete aggregate due to the deleterious expansion caused by reaction of free lime and periclase. In general, a six-month aging period is suggested in order to avoid any potential problems, but it is a tedious process that requires a long period of time. In this work, supercritical CO2 (SCD) was used to reduce the aging period down to one day or so. Since SCD creates a more aggressive environment for reaction, it can directly attack the surface of free lime and periclase to induce expansive reaction before using converter slag as concrete aggregate. According to the experimental results, the surface of converter slag was successfully carbonated by SCD, showing 7.80% of CO2 uptake by weight of converter slag. It was found that the mortar bar made of reacted converter slag reduced the amount of expansion. The 28-day compressive strength of mortar with converter slag was slightly reduced after reaction with SCD, but it was still 32% higher than mortar made of conventional sand.

Analysis of Thermal Behavior of Crystalline Minerals in Bituminous Coal Samples under Air and Argon Atmospheres.

The thermal behavior of ash components in two bituminous coal samples [Upper Freeport (the “UF”) and Illinois #6 (the “IL”)] was investigated under air and argon atmospheres in the temperature range of 800–1200 °C using thermal gravimetric–differential thermal analysis, X-ray diffraction transmission electron microscopy (TEM), and TEM–energy dispersive X-ray spectrometry measurements. The UF treated under air formed the needle-like crystals which were assumed to be mullite-related substances formed by transformation of andalusite, because the crystals are mainly composed of SiO2 and Al2O3. In contrast to the UF, the IL did not generate such crystals; however, when the IL was treated under air after carbonization under Ar, crystals appeared. The composition of the UF with an Al/Si ratio higher than that of the IL favored the formation of mullite-related substances, while the presence of lime in the IL inhibited the formation of mullite-related substances. Oldhamite was formed by the reaction of lime with sulfur at the carbonization of the IL under Ar and remained even at the successive air treatment. As lime was consumed, the formation of mullite-related substances was ceased to be inhibited under air after Ar treatment.

Study of calcium-silicate composite lightened by waste expanded perlite

The term calcium-silicate composite can be recalled several basic building materials. The most common representatives are lime-silicate bricks and autoclaved aerated concrete. It is any material based on the reaction of lime and siliceous raw material. In this paper, attention is paid to composites based on autoclaved aerated concrete production technology. Possibilities of lightening the composite utilizing waste expanded perlite as a secondary raw material were investigated without the use of aluminium powder, which is commonly used in aerated concrete technology. Replacements of 10%, 30%, 50%, and 100% waste expanded perlite for sand were used. Based on physico-mechanical properties, and with the assessment of the microstructure, it has been found that up to 50% of the replacement of waste expanded perlite results in a lightening of the composite while increasing the compressive strength.

Indicators of lime reactivity in soil: particle size, carbon dioxide evolution, and citric acid titration

ABSTRACT Accurate predictions of the short-term reactivity of liming products are needed for situations where rapid soil pH adjustment is desired. Lime efficiency (LE) describes the capacity of a liming material to neutralize soil acidity in comparison with a finely ground CaCO3 standard (LE = 100%). Our objectives were to evaluate LE for calcitic liming materials varying in particle size at 1–12 months after soil incorporation using pH change (LEpH) and CO2 evolution (LECO2) as response indicators, and to evaluate a 15-min citric acid (CA) test as a predictor of LE. We evaluated LE for lime particle size separates from 10 to 200 USA mesh (< 2000 µm to 75 µm) and for three commercial liming products (65, 25 and 11 µm average particle size) in a sandy loam soil. In field microplots, it took 6 months to achieve LE of > 80% with lime particles of <60 mesh (< 250 µm). LEpH was linearly related to LECO2 at one month following lime incorporation into soil. Both LEpH and LECO2 increased as a function of CA test values, as described by logarithmic equations. Lime particle size, CO2 evolution, and CA test values were all useful indicators of short-term LE.

An Investigation on Pozzolanicity of Mechanically Activated Pond Ash

Pond ash (PA) is one of the major industrial solid wastes from thermal power plants. In the present study, PA of different storage durations, i.e. freshly ponded, two year ponded and Six-year ponded ash were collected from Bellary Thermal Plant (BTP). All three kinds of PA were mechanically activated by grinding in Industrial Hammer Mill. Unprocessed Pond Ash (UPA) and Ground Pond Ash (GPA) were characterised for Particle Size Distribution (PSD) by Laser-diffraction analyser. Mineralogical and Morphological characteristics were analysed through X-ray Diffraction and Electron Microscopic studies. Chemical composition of PA was analysed. The pozzolanicity of PA and other Supplementary Cementitious Materials (SCM) was determined and compared by conducting Lime reactivity test. XRD patterns and Chemical analysis clearly indicate the presence of relatively more amorphous phases in a fresh batch of PA compared to the one which is ponded for a longer duration. Lime reactivity strength (LRS) of UPA was far behind the LRS of commonly used SCM’s. Mechanical activation of PA improved the LRS from 0.57 MPa to 2.41 MPa. The results suggest the possibility of enhancing the reactivity of PA with early use and more efficient grinding process, thus add value to PA for its use in concrete.

Plant Parasitic Nematodes Associated with Citrus Trees and Reaction of Two Citrus Cultivars to Tylenchulus semipenetrans in Northern Egypt

A survey of plant-parasitic nematodes (PPN) associating citrus trees in Alexandria, El-Behera and Kafr El-Shiekh governorates, northern Egypt was carried-out during 2017 – 2019 growing seasons. A total of 432 root and rhizosphere soil samples were collected from the surveyed citrus trees. Nematodes were extracted using sieving and Bearmann-pan techniques and, identified to the generic level, based on the morphological characters. Besides, the reaction of mandarine, Citrus deliciosa and lime, C. aurantifolia against the citrus nematode, Tylenchulus semipenetrans, was determined under greenhouse conditions. Results showed that 9 genera of PPN were found in association with the surveyed citrus trees in the three governorates. The citrus nematode, Tylenchulus semipentrans was found to be very common (frequency of occurrence (FO) = 100% in all the surveyed locations, followed by the stubby root nematodes, Trichodorus spp., and the lesion nematodes, Pratylenchus spp. The reaction of the two citrus cultivars; Mandarine, Citrus deliciosa and Lime, Citrus aurantifolia to T. semipenetrans showed that the two cultivars are susceptible to all the tested populations of T. semipentrans with a nematode reproduction factor (RF) was (1.67-2.6).The shoot and root dry weights of these cultivars were reduced as a result of the nematode infection.

Effect of addition of lime on coir fiber admixed BC soil

Expansive soils, having predominantly montmorillonite clay mineral, pose acute construction problems for many civil engineering structures. Admixing lime is popular and cost-effective which is used widely. However, BC soil has inherent low tensile strength but a high compressive strength. Incorporating fiber reinforcement that is capable of absorbing tensile loads or shear stresses will address the problem. In this context, the use of cheaply and abundantly available natural coir fibers as soil reinforcement in the BC soil along with lime is investigated. The effect of lime reaction and associated heat of hydration on coir fiber was investigated in terms of unconfined compressive strength (UCC) of BC soil. XRD and SEM studies on surface characteristics of coir fiber were studied. It was found that, at longer curing periods after addition of lime, plate-like particles are replaced by foil-like membranes and fine filaments due to flocculation–agglomeration of soil particles along with carbonation. XRD confirmed that these fine filaments are foils consisted of calcium silicate hydrate gel that increases strength due to cementation. It was observed that admixing both untreated and treated coir fibers in lime-stabilized BC soil beyond 7 days of curing causes decrease in the UCC due to heat of hydration of lime reaction that seems to affect the fiber characteristics.