Lime Calcium Research Articles

Pre‐treatment of Waste Foundry Sand Via Solidification/Stabilization

AbstractThis study was performed to propose a suitable treatment for waste foundry sand (WFS) before persistent disposal. It was observed that solidification/stabilization (S/S), which is the common pre‐treatment method because of its comparatively easy and inexpensive applicability, can treat WFS including dissolved organic carbon (DOC) above hazardous landfilling limits. Regular sand was partially replaced with WFS with a ratio of 0–90 wt% in order to prepare three different kinds of mortar samples, where Portland limestone cement (PLC) alone, calcium lime (CL) alone, and PLC together with CL were contained as binders. Leaching behaviors of all S/S products were analyzed according to the TS EN 12457‐4 leaching test. The treatment efficiency was assessed to reduce the DOC content to the levels under the European landfill acceptance criteria. Furthermore, heavy metals (Ni, Zn, Cr), fluoride (F−), total dissolved solids leachability, and total organic carbon content were analyzed in order to investigate the pre‐treatment ability and to determine whether S/S products can be disposed of in a landfill site with municipal wastes or in a separate landfill site. The results showed that S/S of WFS is an efficient pre‐treatment technique before its disposal in a landfill and provides economical advantages compared to hazardous waste landfilling.

Preparation and Characterization of Calcium Silicate Slag Based Lightweight Wall Materials

Potassium feldspar (KAlSi3O8) can be used to extract potassium to solve the shortage of water soluble potash resources in China, but it will produce large amount of calcium silicate slag. Resource recycling from calcium silicate slag can be realized by synthesising wall materials. In this research， calcium silicate slag based lightweight wall materials have been successfully prepared by calcium silicate hydrates (CSH), lime and fly ash through autoklave process. Furthermore, the wall materials are charactered by strength determination, X-ray diffraction (XRD) analysis, and Scanning electron microscopy (SEM) analysis. The results show that the compressive strength is mainly influenced by the lime/fly ash mass ratio (L/F), CSH content and water/solid ratio (W/S). The compressive strength of 21.1-23.9 MPa and density of 0.87-0.91 g/cm3 are achieved respectively with the L/F value of 0.82-1.00, CSH content of 70 % and W/S of 0.9. The main hydrate product of wall materials is 11Å tobermorite [Ca5(OH)2Si6O16•4H2O], which is partly formed from the phase transformation of CSH, and partly produced by the reaction among raw materials during the process of autoclaving. The tobermorite is easy formed at low L/F value and it has a contribution to the low density for its flake-like structure that make the materials porous.

Effects of minimal-flow sevoflurane anesthesia combined with Amsorb Plus calcium lime on hepatic and renal functions

Objective To investigate the effects of minimal-flow sevoflurane anesthesia combined with a new CO2 adsorbent Amsorb Plus calcium lime on the hepatic and renal functions in patients.Methods Seventytow ASA Ⅰ or Ⅱ patients,aged 20-60 yr,scheduled for gastrointestinal surgery under general anesthesia,were randomized into 2 groups (n =36 each):middle-flow anesthesia group (group G1 ) and minimal-flow anesthesia group (group G2 ).Amsorb Plus calcium lime was added into the CO2 absorption canister and the core temperature of the calcium lime was continuously monitored and recorded.The patients were tracheal intubated after anesthesia induction and mechanically ventilated.The initial sevoflurane concentration was set at 4％ and the fresh gas flow of oxygen was set at 4 L/min.After the end-tidal concentration of sevoflurane reached 2.6％,the fresh gas flow of oxygen was adjusted to 2 L/min in group G1 or 0.5 L/min in group G2.The end-tidal concentration of sevoflurane was maintained at 2.4％-2.8％ during operation.Venous blood samples were taken 24 h before and 24 h after operation for determination of the serum concentrations of total bilirubin (TBIL),direct bilirubin (DBIL),blood urea nitrogen (BUN) and creatinire (Cr) and activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST).Urine samples were obtained at 24 h before and after operation to detect the concentration of glucose and protein.The urine glucose and protein positive patients were recorded.Results There was no significant difference in the core temperature of calcium lime at different time points between the two groups ( P ＞ 0.05 ).Compared with that at 24 h before operation,AST activity,TBIL and DBIL concentrations were significantly increased,BUN concentration was significantly decreased,but no significant change was found in the Cr concentration and the number of urine glucose and protein positive patients at 24 h after operation in group G1,and DBIL concentration was significantly increased,while BUN concentration was significantly decreased at 24 h after operation in group G2 ( P ＜ 0.05 ).There was no significant difference in the parameters of hepatic and renal functions between the two groups ( P ＞ 0.05).Conclusion The combination of minimal-flow sevoflurane anesthesia and Amsorb Plus calcium lime exerts no effect on the hepatic and renal functions,the effect is similar to that of middle-flow anesthesia,and it can be safely used in patients. Key words: Anesthetics,inhalation; Anesthesia,inhalation; Liver function tests; Kidney function tests

Dolomitic Lime in the US

This paper presents the findings of a comparative study of the physical and chemical properties of dolomitic (magnesian) and high calcium lime mortars with respect to their use for the construction and repair of buildings. Dolomitic hydrated lime has been widely used in the United States as a binder in masonry mortar for over 70 years. Investigation of the curing process of dolomitic lime and how the chemistry affects the physical properties of the mortar has yielded new information. Dolomitic lime mortar behaves differently than mortar containing high calcium lime, yet in the US often no distinction is made between them. With the advent of new machinery for hydrating dolomitic lime in the 1940s, it could be more easily hydrated, packaged and sold. This product enjoyed great popularity during the second half of the twentieth century, particularly as a binder in repointing mortars.

Effect of Dewatering on the Strength of Lime and Cement Mortars

This paper investigates the effects of dewatering on the strength and microstructure of mortars manufactured from Portland cement, hydrated calcium lime (CL90), and natural hydraulic limes of classification 2, 3.5, and 5 with binder/aggregate/water ratios of 1:2:0.78. Dewatering was achieved by placing the mortars on a high porosity brick. Dewatered and nondewatered specimens were exposed to an atmosphere containing 400 ppm carbon dioxide with a relative humidity of 65%, at 20°C for periods of 14, 28, and 56 days. Following hardening for these periods, compressive strengths were compared with evaluate the mechanical performance. The structural morphology of the samples was determined using scanning electron microscopy and chemical composition by Raman spectroscopy. Results showed CL90 mortars are unaffected by dewatering. However, dewatering resulted in an increase in the compressive strength for the hydraulic limes and cement mortars tested.

The measurement of water transport in porous materials using impedance spectroscopy

This paper describes the application of electrical measurements to monitor the extraction (movement of water from the mortar) of water from calcium lime, natural hydraulic lime and Portland cement mortars placed on an adsorbent brick substrate. Impedance measurements were used to identify the changes in bulk resistance of the mortar. A model has been developed combining sharp front theory and Boltzmann's distribution law of statistical thermodynamics to identify the point at which no further absorption of water into the brick occurs. A linear relationship was found between the exponential of bulk resistance and the square root of time during dewatering. A change in gradient was attributed to the end of dewatering.

Influence of cement kiln dust on the physical properties of calcium lime mortars

This work investigates the influence of cement kiln dust (CKD) on the properties of mortars made with a non-hydraulic binder of high available-lime content (calcium lime—CL), in order to further recycle industrial waste. Physical properties of CKD-CL90 mortars with increasing CKD content were compared to those of feebly-hydraulic lime (NHL2) and CL90 mortars. This paper concludes that, despite the CKD in this study being partially inert, the abundant reactive, free lime provided by the CL90 binder has enabled formation of hydration products. The strength development, rising proportionally to the amount of CKD when addition is over 5%, and the reduction in porosity/suction of the CKD/CL90 mixes, support the occurrence of hydraulic set. The high alkalinity of the CKD/CL90 system; the high specific surface of the CKD particles and the presence of amorphous reactive silica further support the presence of hydraulic set. Results evidenced that CKD addition significantly increased the mortar’s water demand simultaneously enhancing compressive strength and bulk density, and decreasing porosity and capillary suction. These effects can be ascribed to both the gain of packing density induced by the CKD particles, and the formation of hydration phases within pores and the space originally filled with water. Finally, this work concludes that the physical properties of CKD/CL mortars including at least 20%CKD are comparable to those of feebly hydraulic lime mixes, however, fracturing by shrinkage (due to high water demand) and damage related to sulphur, chlorine and alkali content need to be investigated before CKD/CL mixes are advised for application.

Physical properties of magnesian lime mortars

Magnesian lime is made from dolomitic limestone. The properties of magnesian lime mortars are not yet clearly established: some authors claim that Mg-lime has no hydraulicity and produces poor quality mortars that fracture, while others state that it produces quality hydraulic mortars. Here, Mg-lime was produced by burning magnesium limestone in a traditional limekiln. Mortars were made with increasing proportions of Mg-lime and calcium lime (CL90), and tested according to both European and ASTM Standards, and RILEM recommendations. Shrinkage, compressive and flexural strengths, absorption, capillary suction, density and porosity were evaluated, and the relationships between workability (measured as initial flow), water demand and strength investigated. The process of lime production evidenced that fabrication parameters are instrumental on the quality of Mg-lime and the subsequent mortar’s performance. Temperatures over 900°C induced over-burning resulting in clinker formation and a lack of reactivity. The choice of kiln fuel and burning arrangement proved essential in order to reach a homogeneous calcination; and sieving of unslaked and over/underburnt particles as well as trials to determine raw feed proportions, were needed in order to avoid poor quality lime. Testing evidenced that the higher the Mg content, the greatest the mortar’s shrinkage. However, shrinkage did not reach unacceptable values and cracking didn’t occur. It was also evidenced that the Mg-lime possessed a lower water demand than the CL; and that Mg mortars behave well towards fluids (their capillary suction was lower and their porosity and absorption similar to those of CL90 mortars). The results also suggest that Mg-lime mortars possess compressive and flexural strengths equivalent to those of some feebly-hydraulic lime mortars: Mg-lime strength falls within the EN459-1 strength requirements for natural feebly-hydraulic lime. This research concludes that, providing production is correct, Mg-limes produce reliable masonry mortars which will shrink further but will possess a lower water demand and a slightly higher mechanical strength than CL mortars.

Calcium Sulphate versus Lime as Fertilizer Filler: Effects on Ammonium and Nitrate Uptake by Perennial Ryegrass

The recovery of 15N‐labelled nitrogen (N) by perennial ryegrass can be significantly increased by mixing gypsum (CaSO4 · 2H2O) into soil rooting medium at rates equivalent to 0.7 t ha−1. Similar improvements in fertilizer N efficiency might be achieved, at less cost and more conveniently, by applying smaller amounts of CaSO4 anhydrite more strategically to fertilizer microsites as a fertilizer filler or diluting agent, in calcium ammonium nitrate (CAN), in place of CaCO3. With this in mind, two complementary pot experiments were conducted under simulated spring conditions in a controlled environment chamber. Use of CaSO4 as diluting agent, in place of CaCO3, appreciably enhanced (>30%) the uptake of labeled N by perennial ryegrass plants within the second week of regrowth, but thereafter, because losses of 15N‐labeled NO3 −‐N from pots by denitrification or leaching had been minimal, plants in both treatments eventually recovered equal amounts of this N form from the soil.

Groundnut Response to Ash, Phosphorus, Lime and Tillage in Southern Cameroon

ABSTRACT Groundnut (Arachis hypogaea L) is an important intercrop in southern Cameroon. Two on-farm experiments were undertaken to determine if soil fertility constraints, varieties and tillage practices were major limiting factors in groundnut production. In Experiment I, combinations of P and K fertilizers and ash were applied to local groundmtt. and ash to improved groundnuts (var. A-26). In Experiment 2, ash and dolomitic lime were tested with a local variety, combined with ridging or no ridging, and ash applied to a variegated Virginia (VV) groundnut variety. The experiments were conducted in six villages in southern Cameroon. Soil analytical variables were covariates in the analysis of variance. Groundnut yields were affected by significant ash × calcium saturation (Ca sat'n) and lime × Ca sat'n interactions. Where ash or lime was applied, yields were improved where Ca sat'n levels were below 0.62, but decreased at higher Ca sat' n levels. Significant village × variety interactions (p < 0.05) showed that varieties A-26 and VV yielded less than the local variety in several villages. P, K or tillage did not improve yields over the control. Both liming and ash applications increased soil pH, exch. Ca and Mg, and decreased exch. AI, while P + K applications increased exch. K and extractable P. The results show that ash application significantly influences several soil chemical variables. While yield increases in local groundnut yields can be realized at sites where Ca sat'n is low from either lime or ash applications, such increases are relatively minor. Alternative varieties tested offered no advantage over local varieties already grown in the area.

The Use of Pozzolans in Lime Mortars

In the conservation and restoration of old buildings, a great deal of time and effort is spent on matching the old materials (perhaps centuries old) using modem chemicals and products. Consideration has also to be given to the techniques and skills of the old craftsmen, which in most cases reflected the materials available at the time. Modem materials are much more tightly specified and react much more predictably than the materials manufactured 100 years ago and while modem craftsmen are still highly skilled, there is a higher expectation both of predicted performance and economics than there was centuries ago. Materials have also changed and high calcium lime is typical of such a material. Over the years, this has changed from being an impure raw material into a tightly controlled ‘chemical’ due to pressure, firstly, from the chemical industry and, secondly, from the steel industry. The same changes have not been so apparent in the materials used as pozzolans. While efforts have been, and are being made, to characterize the effects of some of the traditional pozzolans, newer materials are being considered because of their pozzolanic effects. By and large, there is very little specific documented information regarding their properties and performance characteristics to which the specifier, producer or user can refer.

Quality analysis/quality control tests for field stabilization/solidification — 1. Dry cementing additives

As part of a field validation study of their proposed protocol for solidified waste evaluation, which will correlate laboratory test results with field behaviour, the Wastewater Technology Centre investigated the applicability of several rapid tests for quality analysis and control of the field solidified waste. A pilot-scale landfill was constructed and 63 m 3 solidified arc furnace dust placed in it using a cementing system consisting of blast furnace slag, lime, silica fume and sodium metasilicate. The ground blast furnace slag, hydrated high calcium lime and silica fume were pre-blended before being trucked to the field site and the sodium metasilicate was added in the mixing water. Available lime index using the rapid sugar method (ASTM C-25) and measurement of specific gravity were used to determine the effect of mixing procedures and transportation on the homogeneity of the blended dry additives. Experimental results indicate that the rapid sugar method can give an accurate analysis of lime content in the pre-blended additives. There is a good linear relationship between the slag content and specific gravity because the lime and silica fume have a similar specific gravity. However, the agglomeration of the blended additives affects the accuracy and precision of the method.

Influence of topsoil removal and fertilizer application on peanut yields from an Indonesian Ultisol

Experiments were conducted on a tropical Ultisol in west central Sumatra, Indonesia, to evaluate the effects of topsoil removal and the subsequent application of phosphorus and potassium fertilizers, and calcium lime, on crop productivity. Peanut ( Arachis hypogaea L.) yields and total above-ground biomass production were determined in field plots and potted soils from which 0, 3, 7 and 15 cm of topsoil had been removed. The removal of 3 cm of topsoil, which was equivalent to the entire A-horizon resulted in a significant reduction in peanut yields and above-ground biomass in both field and potted soils. No significant yield differences in peanut yields or biomass were observed between] treatments from which ⩾3 cm of topsoil had been removed. The application of fertilizers and lime restored peanut yields to levels observed in unfertilized soils from which topsoil had not been removed. However, the use of off-farm inputs was economically unfeasible for most hillside farmers in the research area.

Mechanism of Pozzolanic Reactions and Control of Alkali-Aggregate Expansion

Abstract The mechanism of pozzolanic reactions and their control of expansion caused by alkali-aggregate reaction was investigated. Mixtures of tricalcium silicate, opal, sodium hydroxide, and water having calcium oxide to silica mole ratios from 1.07 to 3.0 were prepared and reacted from seven days to four years before filtering. The solids (precipitates) were studied by X-ray diffraction to determine the phases present, and the alkali content of filtrates was obtained by chemical analysis. Results suggest that pozzolans reduce or eliminate alkali-aggregate expansion by producing additional calcium silicate hydrate and low lime calcium silicate hydrate. These hydrates can retain additional alkali, thus reducing the amount of alkali available for reaction with reactive aggregate. In order to control alkali-aggregate expansion by the addition of pozzolan, such as fly ash, results indicate that about 30% low lime fly ash is required. However, this amount could be reduced considerably, to a level as low as 20% (cement basis), if the concrete contains reactive siliceous aggregate.

Alleviation, by a formulation containing calcium peroxide and lime, of microbial inhibition of cereal seedling establishment

Some microorganisms can prevent seed germination and retard the extension growth of seedlings roots by providing a sink for available oxygen and by producing phytotoxic metabolites. These effects have been alleviated in the laboratory by dressing cereal seed with a formulation containing calcium peroxide and lime.

Sulfur oxides (SOx) removal and acid neutralization with its by-product

A solid by-product from a new SO/sub 2/ removal process consists of a core of lime surrounded by a cracked shell of CaSO/sub 4/. Laboratory tests were conducted to compare the effectiveness of this by-product with that of high calcium lime in H/sub 2/SO/sub 4/ neutralization. The crystals formed with the by-product are rhombic and are adsorbed on the surface of the cracked CaSO/sub 4/ coating. The CaSO/sub 4/ coating serves as the nucleus for acceleration of the growth of particles to a size that settles rapidly, forming a compact sludge. Thus, the volume of sludge produced in the neutralization of a H/sub 2/SO/sub 4/ solution by the by-product was considerably less than that produced by high-calcium lime. The CaO dosage of the by-product was smaller than that of high-calcium lime, for the same degree of H/sub 2/SO/sub 4/ neutralization. Under laboratory conditions, the by-product did not produce scale in acid neutralization. The by-product can also be used effectively to neutralize H/sub 2/CO/sub 3/, H/sub 2/SO/sub 3/, and H/sub 2/SO/sub 4/ in SO/sub 2/ scrubbing.

EFFECTS OF SPRAY APPLICATIONS OF BORON, STRONTIUM AND CALCIUM ON BREAKDOWN DEVELOPMENT IN SPARTAN APPLES

Prebloom calcium chloride or lime sprays on Spartan apple (Malus pumila Mill.) trees did not increase fruit calcium levels or decrease breakdown incidence. Boron applied in summer with calcium sprays did not decrease breakdown incidence or increase fruit calcium levels beyond the effect of the calcium sprays alone. Strontium sprays did not affect the incidence of breakdown in Spartan apples.

An automated method for the determination of lead in calcareous materials utilising liquid ion exchange.

An automated method for the determination of lead in calcium carbonate, lime and limestone with the Technicon AutoAnalyzer is described. The method is based on the extraction of lead from an acidic chloride solution of the sample with a long-chain amine liquid ion exchanger, followed by re-extraction into an ammonia-ammonium citrate buffer at pH 9. Finally, the lead is extracted as the lead-dithizone complex into chloroform and the optical density of the complex measured at 510 nm. The separation of lead prior to formation of the lead-dithizone complex results in low background and blank readings. Lead levels of 0 to 20 p.p.m. can be determined at a rate of twenty samples per hour. Other trace metals which occur in calcareous materials do not interfere.

A note on the effect of lime and calcium carbonate supplementation on the nutritive value of paddy (Oryza sativa) straw

SUMMARYIn an experiment on nine Kumaoni bullocks, the effect of supplementing paddy straw rations with calcium carbonate or lime was studied. The digestion coefficients of dry matter, crude protein, ether extract and total carbohydrates and balances of nitrogen and phosphorus were not significantly affected by such supplementation; the calcium balances were significantly improved. It is concluded that supplementation of paddy straw rations with calcium carbonate (which is cheap and easier to handle), or with slaked lime, can be used with advantage in combating the problem of negative calcium balances frequently encountered on paddy straw rations. Incorporation of a small quantity of wheat bran (about 4 oz) helps in meeting the phosphorus requirement of adult animals.

Hydrothermal reactions in the lime-rich part of the system CaO-SiO2-H2O

Summary The mineralogy of autoclaved products from various forms of calcium silicate andfrom lime and silica has been investigated. The results are as follows. With a CaO/SiO2 ratio of 1, the product is always well crystallized tobermorite. With a CaO/SiO2 ratio of 2, the product varies: starting with lime and silica, dicalcium silicate alpha-hydrate is the first product; this eventually changes into dicalcium silicate beta-hydrate, the stable phase; starting with calcium silicate hydrate I and lime, the first product comprises Flint's CSH(A) and dicalcium silicate alpha-hydrate, and it seems likely that the Flint's CSH(A) will eventually convert to dicalcium silicate alpha-hydrate and the dicalcium silicate alpha-hydrate to dicalcium silicate beta-hydrate; if one starts with β-2CaO.SiO2, the product in the first place is dicalcium silicate gamma-hydrate; in the length of processing used in the experiments reported in this paper, no other phase was found, but it is considered that dicalcium silicate gamma-hydrate is only metastable. With a CaO/SiO2 ratio of 3, again the products vary with the starting minerals: with mixes of lime and silica and with mixes of 2CaO.SiO2 and lime, the first product is dicalcium silicate alpha-hydrate which is eventually converted to the beta-hydrate; with mixes of calcium silicate hydrate (1) and lime, the product is always Flint's CSH(A) with or without some dicalcium silicate alpha-hydrate; with 3CaO.SiO2 as the starting material, the product is always 3CaO.SiO2.1½H2O. It is clear from this work that the form of the starting material has a considerable influence on the nature of the metastable phases produced, and also that, in this part of the system CaO-SiO2-H2O, even prolonged processing up to 90 days is insufficient to produce true equilibrium phases.