Saturated Lime Solution Research Articles

Study of the influence of synthesised zeolite as a self-healing for hardened cementing materials

ABSTRACT The impact of incorporating synthesized zeolite on Portland cement with different ratios was analyzed to enhance the healing effeciency of pre-cracked hardened matrix. The pre-cracked hardened specimens was subjected to treatment through immersion in tap water or a saturated lime solution, with the objective of enhancing the effectiveness of the healing process. These matrices represent the most frequently used environments suitable for crack healing. Given that water is a crucial component for cement hydration, saturated lime can alternatively be applied on cracks via spraying to facilitate the ability of heaing thr cracks. The outcomes demonstrated the effectiveness of repairing the pre-cracked structure in both conditions, while the fully saturated lime possesses a higher potential in mending the cracks, as evident from visual observation and petrographicanalysis. Additionally, Fourier Transform Infrared Spectroscopy revealed the incorporation of synthesized zeolite into the structure resulted in an enhancement of the intensity of the formed binder, which interm positively influenced its healing ability. The highest compressive strength was observed in specimens with 4% zeolite addition immersed in tap water, reaching 89 MPa. Furthermore, the compressive strength increased to 116 and 157 MPa with 4% and 6% zeolite addition, respectively, in the fully saturated lime environment.

Resistance of basalt fiber to alkaline environment of hydrated Portland cement

The article shows a study of the effect of hydrated Portland cement, aggressive towards basalt fiber, and more aggressive saturated lime solution over time. The degree of destruction of basalt fiber over time has been established.

Experimental determination of gas holdup and volumetric mass transfer coefficient in a jet bubbling reactor

The hydrodynamics and mass transfer characteristics of a lab-scale jet bubbling reactor (JBR) including the gas holdup, volumetric mass transfer coefficient and specific interfacial area were assessed experimentally investigating the influence of temperature, pH and superficial gas velocity. The reactor diameter and height were 11 and 30 cm, respectively. It was equipped with a single sparger, operating at atmospheric pressure, 20 and 40 °C, and two pH values of 3 and 6. The height of the liquid was 23 cm, while the superficial gas velocity changed within 0.010–0.040 m·s −1 range. Experiments were conducted with pure oxygen as the gas phase and saturated lime solution as the liquid phase. The liquid-side volumetric mass transfer coefficient was determined under unsteady-state oxygen absorption in a saturated lime solution. The gas holdup was calculated based on the liquid height change, while the specific interfacial area was obtained by a physical method based on the bubble size distribution (BSD) in different superficial gas velocities. The results indicated that at the same temperature but different pH, the gas holdup variation was negligible, while the liquid-side volumetric mass transfer coefficient at the pH value of 6 was higher than that at the pH = 3. At a constant pH but different temperatures, the gas holdup and the liquid-side volumetric mass transfer coefficients at 40 °C were higher than that of the same at 20 °C. A reasonable and appropriate estimation of the liquid-side volumetric mass transfer coefficient ( k l a ) in a pilot-scale JBR was provided which can be applied to the design and scale-up of JBRs. • k l a is determined experimentally for O 2 absorption into Ca(OH) 2 solution in the JBR. • k l a is calculated for SO 2 absorption into Ca(OH) 2 solution in the JBR. • Specific surface area, is experimentally obtained by a physical method based on BSD. • Effects of temperature, solution pH, and superficial gas velocity are studied on k L a . • Gas holdup as a hydrodynamic parameter is investigated for the JBR.

The Metakaolin - A New Hydraulically Active Pozzolanic Additive

The replacing part of Portland cement with thermally activated clays will reduce the "clinker factor", which in turn will reduce greenhouse gas (CO2) emissions. The metakaolin activity by the lime absorption method from a saturated lime solution and by binding Cao from limestone dough was determined. It is shown that the metakaolin interaction products with Ca (OH)2 are characterized by a multiphase and are composed mainly of hexagonal and cubic hydroalumination calcium and various basicity poorly crystallized calcium hydro-silicates. The results obtained allow the Metakaolin to be considered a new, hydraulically active pozzolanic additive.

Study of Chloride Corrosion Organic Inhibitors in Alkaline Pore Solution

This paper compares the inhibition properties of aspartic and lactic acid salts with nitrite ions and their effect on critical chloride concentration. The tests were carried employing carbon steel specimens in saturated lime solution with varying pH in the range between13 to 13.6. The critical chloride concentration was estimated through multiple specimen potentiostatic tests at potentials in the usual range for passive rebar in the alkaline concrete of atmospheric structures. During tests, chloride salt was added every 48 h until all the specimens showed localized attacks. The cumulative distribution curves, i.e. the number of corroded specimens as a function of the chlorides concentration was obtained. Furthermore, IR spectra were recorded for the evaluation of the presence of the organic inhibitors on the passivity film. The results confirmed the inhibitory effect of 0.1M aspartate comparable with nitrite ions, at a similar concentration. Addition of calcium lactate did not result in an increase in the critical chloride concentration. However, the formation of a massive scale containing the substance that could reduce the corrosion propagation was observed.

Short-term lime solution-kaolinite interfacial chemistry and its effect on long-term pozzolanic activity

Abstract Soils stabilization with lime addition is a widespread technique in geotechnical field. Better understanding of interaction mechanism is central for optimization of the technique. In the present work, the short-term kaolinite-lime solution interfacial chemistry and the effect on the dissolution and long-term reaction has been investigated. Calcium adsorption from saturated lime solution (i.e. simulated alkaline pore solution ([Ca] = 22 mmol/l and pH = 12.63)) characterized by initial fast uptake followed by slower adsorption rate curves, whereas only initial fast uptake is identified from chloride solution ([Ca] = 22 mmol/l and pH = 7). Species of calcium available for adsorption are strongly dependent on the pH conditions (i.e. Ca2+ at pH 7 and CaOH+ at pH 12.63). The adsorption increased with increasing initial concentration of calcium. On the other hand, the more the quantity of calcium adsorbed, the less the measured concentration of silicon and aluminum in the supernatant. The adsorbed calcium distribution has been mapped using μ-XRF. Regardless of the quantity of calcium adsorbed, homogeneous distribution has been identified suggesting coating of kaolinite particle by adsorbed calcium. The coating in turn prevented the kaolinite particles from alkaline attack and retards long-term pozzolanic reaction.

Effectiveness of the mild alkali and dilute polymer modification in controlling the durability of jute fibre in alkaline cement medium

With the aim to improve the durability of natural fibres used as fibre reinforcement in the cement matrix, the combined alkali and polymer modification would be a unique approach. The present investigation deals with the durability performances of the unmodified and combined mild alkali and polymer emulsion modified jute fibres exposed to alkaline medium and cement medium as well. Initially, the jute fibres were modified using mild alkali (0.5% NaOH, 24 h) and dilute polymer emulsion (0.125% carboxylated styrene butadiene rubber (SBR)) sequentially. Afterward, the unmodified and modified jute fibres were then exposed to the saturated lime solution, 0.1 N NaOH solution, and cement paste for 360 days. After periodic exposure in different media, the fibres were removed and tested. Based on the results, it is demonstrated that the combined alkali and polymer modified jute fibre retains 17, 19 and 20% more tensile strength as compared to that of the raw jute fibre after 360 days exposure in saturated lime solution, NaOH solution, and cement paste, respectively. The improved durability of the combined alkali and polymer modified jute appears to be due to the reduction of fibre mineralization by forming a protective coating of polymer on the fibre surface as demonstrated by elemental analysis, FTIR, XRD, NMR, SEM in conjugation with EDS.

Correlation of Surface Adsorption and Oxidation with a Floatability Difference of Galena and Pyrite in High-Alkaline Lime Systems.

When it comes to Pb-Zn ores with high amounts of pyrite, the major problem encountered is the low separation efficiency between galena and pyrite. By virtue of high dosage of lime and collector sodium diethyl dithiocarbamate (DDTC), pyrite and zinc minerals are depressed, allowing the galena to be floated. However, there have been significant conflicting reports on the flotation behavior of galena at high pH. In this context, correlation of the surface adsorption and oxidation with the floatability difference of galena and pyrite in high-alkaline lime systems would be a key issue for process optimization. Captive bubble contact angle measurements were performed on freshly polished mineral surfaces in situ exposed to lime solutions of varying pH as a function of immersion time. Furthermore, single mineral microflotation tests were conducted. Both tests indicated that the degree of hydrophobicity on the surfaces of galena and pyrite increased in the presence of DDTC at natural or mild pulp pH. While in a saturated lime solution, at pH 12.5, DDTC only worked for galena, but not for pyrite. Surface chemistry analysis by time-of-flight secondary ion mass spectrometry (Tof-SIMS) confirmed the preference of DDTC on the galena surface at pH 12.5, which contributed to a merit recovery. Further important evidence through measurements of Tof-SIMS, ion chromatography, and high-performance liquid chromatography indicated that in high-alkaline lime systems, the merit floatability of galena could exclude the insignificant contribution of elemental sulfur (S8) and was dominantly attributed by the strong adsorption of DDTC. In contrast, the poor flotation response of pyrite at high pH was due to the prevailing adsorption of CaOH+ species. This study provides an important surface chemistry evidence for a better understanding of the mechanism on the better selectivity in the galena-pyrite separation adopting high-alkaline lime systems.

Kinetic effect of carbonic anhydrase enzyme on the carbonation reaction of lime mortar

ABSTRACTThe effect of carbonic anhydrase enzyme on the precipitation kinetics and phase transformations of calcium carbonate, and on the strength development of lime mortars has been investigated with saturated lime solutions, lime pastes and lime mortars under atmospheric conditions. The results clearly show that carbonic anhydrase catalyzes the reaction between carbon dioxide and aqueous lime, and increases the rate of calcium carbonate crystallization, the yield of the carbonation reaction and mortar strength at early ages. This is most likely a kinetic effect associated with the increased rate of carbonate ions supply to the solution by the enzyme. In addition, this enzyme favors the formation of stable calcite and significantly modifies its morphology by developing new crystal faces. These results suggest a novel approach for accelerating the hardening of lime mortars using carbonic anhydrase enzyme, which may offer a potentially novel approach with significant benefits on the applications of lime mortars in architectural heritage conservation as well as in construction.

Thermal activation of an industrial sludge for a possible valorization

This work fits within the framework of sustainable management of sludge generated from wastewater treatment in industrial network. The studied sludge comes from an industry manufacturing sanitary ware products.Physico-chemical and mineralogical characterization was performed to give an identity card to the sludge. We noted the absence of metal pollution.The industrial sludge has been subjected to thermal activation at various temperatures (650°C to 850°C). The pozzolanic activity was evaluated by physico- chemical and mechanical methods [1]. Pozzolanicity measurement was carried out based on Chapelle test and conductivity revealed the existence of pozzolanic properties of the calcined samples. The best pozzolanic reactivity was obtained for the sample calcined at 800°C. We noticed a decrease in the reactivity of the sample calcined at 850°C. In addition, analysis by means of X-ray diffraction and Fourier transform infrared spectroscopy showed that sludge recrystallization begins at a temperature of 850°C. Pozzolanicity index of the thermally treated samples was determined by measuring the mechanical resistance of mortar specimens previously kept in a saturated lime solution for 28 days (ASTM C618 [2]). The best pozzolanic activity index was obtained for the sample calcined at 800°C (109.1%).This work is a contribution to the research for new supplying sources of raw materials and additives in the field of construction. It presents a proposition of a promising solution for the valorization of waste material as an additive instead of being discharged into open air dumps causing a major environmental problem.

Structure Analysis of Microbe-Repaired Concrete Using Scanning Electron Micrographs

As one of the most popular materials used in construction, concrete is prone to superficial flaws, such as crack, due to the load-bearing and external environment. This research manually made cracks of 2 mm with 100 mm length and 30 mm depth on concrete vessels as specimens. Subsequently, bacteria, specifically B. pasteurii, was used in crack rehabilitation to enhance the compression strength of the repaired concrete. The mixture of microbes, urea medium, and urea-CaCl2 medium was added to a sludge and fine aggregate with a weight ratio of 0.6:1:1 to be the repairing material for crack rehabilitation. Crack rehabilitation was conducted by injected the mixture into the test samples after 90 days curing in saturated lime solution. In addition to the traditional test – compression test, scanning electron microscope (SEM) was used to examine the structure composition of the microbe-repaired concrete for calcium carbonate crystal formation. Various rectangular and polygonal crystals were observed in the SEM photographs of the microbe-repaired concrete samples with high bacterial concentrations demonstrated that bacteria can induce calcium carbonate precipitation to complete crack rehabilitation. The results prove that high concentration of bacterial broth induced a great amount of calcium carbonate precipitate and improved the concrete strength of the microbe-repaired samples.

Solubility of Phosphogypsum in Pure Water and Lime Solution

In this work, the solubility of phosphogypsum(PG) in water and saturated lime solution was determined in experiments carried out at different temperatures from 10 to 50°C. The solubility of natural gypsum(NG) was also studied at an attempt to find out differences in solubility between PG and NG due to the effect of impurities. The results show that in pure water media, PG dissolves more rapidly than NG at early time, and then equally with NG. With increasing the temperature of water, the dissolution rates PG decreased while that of NG increased. In saturated lime solution, compared with NG, the solubility of PG was distinctly influenced due to the existence of impurities. Possible reaction among soluble impurities and calcium ion retarded the dissolution of calcium sulfate dihydrate.

Measurement of surface‐transfer coefficient values for CO2 absorption in lime solutions in presence of surfactants

AbstractA modified manometric apparatus has been used for the experimental determination of surface‐transfer coefficient values, used for the design calculations of various mass‐transfer equipments, for the absorption of carbon‐dioxide gas in saturated lime solution in presence of different types of surfactants. An analytical expression has been derived for estimation of the volume of gas absorbed, using the manometric data, for different times of absorption. The rate of gas absorption was found to remain constant initially for about 1 min and thereafter decreased with the progress of absorption time. Surface‐transfer coefficient values for gas absorption have been calculated using the experimental data of the volume of gas absorbed, without and with the addition of different concentrations of surfactants to the lime solutions. For a particular surfactant, surface‐transfer coefficient values were found to decrease with an increase in the concentration of surfactant in solution. The calculated values of the surface‐transfer coefficients for different surfactants are in close agreement with those reported in the literature.

Pozzolanic activity and alkaline reactivity of a mordenite-rich tuff

A natural mordenite-type zeolite from Palmarito ore deposit (Cuba) was studied along the reaction with a saturated lime solution at 40 °C in order to determine its pozzolanic activity. Ca(OH) 2 is an alkali activating agent that simulates the release of lime from ordinary portland cement during the hydration reaction. Formation of C–S–H-like phases with very low Ca/Si ratio (below 0.8) was observed in agreement with previous studies, however, the transformation of the original mordenite into a heulandite–clinoptilolite-type secondary zeolite was also detected. A thermodynamic approach was used to evaluate the stability of the zeolite minerals and showed that clinoptilolite is the most stable zeolite that forms under the experimental alkaline conditions. The results indicate that not all Ca 2+ consumed from solution is used in the pozzolanic reaction. Calcium aluminates hydrates were not detected as products of the alkali-activated reaction.

Zinc recovery from the water-jacket furnace flue dusts by leaching and electrowinning in a SEC-CCS cell

Zinc containing flue dusts generated during a copper matte smelting process in a water-jacket furnace was leached in a zinc electrowinning return solution at 55 °C. Ninety percent of the metal was dissolved after 2 h of treatment. The leaching residues contained near 43 wt.% PbSO 4. Iron was removed from leaching solutions by precipitation using a saturated lime solution at pH 3–4. The precipitate formed mainly consisted of gypsum CaSO 4.2H 2O. Iron and magnesium co-precipitated into a chloro-hydroxide compound. No zinc compound had co-precipitated during iron removal. Copper and germanium contents lower than 10 mg/l were achieved by solvent extraction using 10% LIX 64N and cementation. Cobalt contents lower than 1 mg/l in the solution were achieved by cementation on zinc granules for 2 h at 72 to 82 °C in presence of antimony. Cadmium contents of solutions were reduced to 10 mg/l by cementation on zinc granules at room temperature. Electrons transfer regime was identified as a limiting step during zinc electrolysis in a symmetric electrolysis current–continuous circulating system, SEC-CCS. Electrolysis current efficiency higher than 94% and 3.5 kWh/kg of specific energy consumption was achieved under 500–600 A/m 2 at 35 to 40 °C in the presence of gelatine.

Methodology for Rapid Determination of Pozzolanic Activity of Materials

Abstract Determination of pozzolanic activity, and in particular lime reactivity, of various materials such as fly ash, cenospheres, blast furnace slag, etc., is quite essential for their efficient application in cement and concrete. It also plays an important role in the selection of the material as a stabilizer in various environmental cleanup projects, such as heavy metal retention and waste immobilization strategies. Though ASTM C 311, ASTM C 593, and IS 1727 are being followed to determine pozzolanic activity of different materials, they are quite time consuming. This necessitates development of a methodology that can be employed for determining the pozzolanic activity of different materials, quite rapidly and easily. With this in view, a methodology that indirectly estimates pozzolanic activity of different materials, by measuring electrical conductivity of their mixture in partially saturated lime solution, has been developed and its details are presented in this paper.

Modification of the properties of salt affected soils using electrochemical treatments

In this project, an in situ soil treatment technique using the principles of electrokinetics was tested using laboratory experimental models in order to identify the potential of this approach in modifying and reinstating the physical properties of salt affected soils. Experiments were conducted in the laboratory using saline-sodic soils collected from two salt affected regions in central Victoria, Australia. Soil specimens were compacted in glass tanks to reproduce in situ density and in situ water content. Using mild steel electrodes inserted into the soil, a direct current was passed through the soil under a constant potential gradient of 0.5 V/cm for a period of 14 days. In separate experiments, distilled water and a saturated lime solution were introduced to the soil via the anode over this experimental period. It was observed that the soil dispersion, otherwise known as soil sodicity (measured as ESP—Exchangeable Sodium Percentage and SAR—Sodium Absorption Ratio) decreased by up to 90% in most regions of the soil between the electrodes. The compressive strength of the soil increased in excess of 100% with electrokinetic treatment alone while the lime-enhanced electrokinetic treatment led to an almost 200% strength increase. The liquid limit and plastic limit of the soil increased causing the plasticity index to decrease, indicating increases in soil compressive strength and workability. These results indicate the potential of this technique for improving the physical properties of salt affected soils both effectively and efficiently, and in particular gives hope for the remediation of salt affected land for infrastructure management and development.

(427) Seed Germination after Steeping in Saturated Lime Solutions

A lime solution is an efficient starch gelatinization agent during the traditional process of nixtamalization of corn for tortilla production. Although the saturated Ca(OH)2 solution is usually heated to speed the process, similar physical-chemical changes occur to corn steeped at room temperature. In addition, the steeped grains are capable of rapid germination. In this study we explored whether, in barley grains subjected to the same steeping conditions, there would be an acceleration of biochemical changes for the production of malt. Barley grains cv. Esmeralda six-row were steeped in saturated solutions of lime from 0% to 2% (w/w) at 18 to 23 °C for up to 72 hours. After treatment, the grains were washed with water and placed in a germination cabinet at 20 ± 2 °C and 90% RH for up to 96 hours to germinate. Activity of α-amylase (U/mg protein), sprout length (cm), seed viability (tetrazolium test), and respiration rates were determined. Scanning electron micrographs were prepared. There was a very rapid uptake of lime solution by the barley grains during the first 30 hours of treatment. The barley grains were 98% viable after all periods of steeping. Grains steeped 24 hours and germinated 70 hours had the highest activity of α-amylase, longest sprout length and highest percentage of germination. Under SEM, chemical gelatinization of starch grains was observed in barley sections after different steeping treatments, and starch breakdown was observed in grains during germination. No fungal growth was observed during germination after the steeping treatments. These results demonstrate that steeping in lime solutions could shorten the period required for barley germination and similar conditions may be useful for germination of other cereal and vegetable seeds.

Properties of high-volume fly ash concrete incorporating nano-SiO 2

This paper presents a laboratory study on the properties of high-volume fly ash high-strength concrete incorporating nano-SiO 2 (SHFAC). The results were compared with those of control Portland cement concrete (PCC) and of high-volume fly ash high-strength concrete (HFAC). Assessments of these concrete mixes were based on short- and long-term performance. These included compressive strength and pore size distribution. Significant strength increases of SHFAC compared to the high-volume fly ash high-strength were observed as early as after 3 days curing, and improvements in the pore size distribution of SHFAC were also observed. In this work, the hydration heat of nano-SiO 2 fly ash cement systems was also studied in comparison to the fly ash–cement systems and to the pure cement systems. In addition, the weight change of fly ash incorporating nano-SiO 2, fly ash, and nano-SiO 2 alone after immersed in saturated lime solution was also studied.

In vitro calcium phosphate growth over surface modified PMMA film

In vitro nucleation of calcium phosphate phase was studied over functionalized polymethyl methacrylate (PMMA) films using Fourier transform infrared spectroscopy, electron spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis. PMMA films were prepared by dissolving commercial grade pellets in chloroform and cast into thin sheets. The films were immersed in a methanol solution of sodium hydroxide before treating with 1.5% solution of adenosine triphosphate (ATP) at a pH of 5.2 for 24 h. ATP treated films were then soaked in saturated lime solution for 4 days to initiate formation of calcium phosphate precursor phase over their surface. The above films immersed in simulated body fluid solution (1.5×SBF) for more than 5 days led to the nucleation of apatitic calcium phosphate phase all over the film surface. The ATP coupled film not subjected to lime treatment did not show calcium phosphate nucleation behaviour upon immersion in SBF solution. The Ca/P ratio of the calcium phosphate phase increase with increase in soaking time in SBF solution.