Calcium oxide

About: Calcium oxide is a research topic. Over the lifetime, 7600 publications have been published within this topic receiving 66104 citations. The topic is also known as: caustic lime & quicklime.

Influence of time between mixing and compaction on properties of a lime-stabilized expansive clay

Abstract: THE EFFECTIVENESS OF 4% DOLOMITIC HYDRATED LIME AS A STABILIZER FOR AN ORGANIC EXPANSIVE CLAY SOIL HAS BEEN INVESTIGATED. SAMPLES OF TREATED AND UNTREATED SOIL WERE COMPACTED TO 90% OF MAXIMUM DENSITY FOR EACH MIXTURE, AS OBTAINED BY MODIFIED AASHO COMPACTIVE EFFORT, OVER A RANGE OF WATER CONTENTS. THE EFFECTIVENESS OF STABILIZATION WAS MEASURED, IN MOST CASES, BY TRIAXIAL COMPRESSION TESTS AT VARIOUS AGES AFTER COMPACTION FOR BOTH SOAKED AND UNSOAKED SAMPLES. IT WAS FOUND THAT THE TIME INTERVAL BETWEEN MIXING (OF THE SOIL, WATER AND LIME) AND COMPACTION COULD HAVE A PRONOUNCED EFFECT ON THE PROPERTIES OF THE TREATED SOIL. FOR SAMPLES PREPARED USING CONSTANT COMPACTIVE EFFORT, A DELAY OF 24 HR BETWEEN MIXING AND COMPACTION LED TO AS MUCH AS 8% DECREASE IN DENSITY AND 30% DECREASE IN AS-CURED STRENGTH FROM THE VALUES FOR SAMPLES COMPACTED IMMEDIATELY AFTER MIXING. THE EXPANSION AND SOAKED STRENGTH CHARACTERISTICS OF TREATED SAMPLES WERE ALSO ADVERSELY AFFECTED BY A DELAY BETWEEN MIXING AND COMPACTION. THE PRINCIPAL FACTOR RESPONSIBLE FOR THIS BEHAVIOR WAS FOUND TO BE THE DECREASE IN DENSITY (AT CONSTANT COMPACTIVE EFFORT) ACCOMPANYING DELAYS BETWEEN MIXING AND COMPACTION. THE UNSOAKED AND SOAKED STRENGTH AND THE SWELL VALUES FOR SAMPLES COMPACTED IMMEDIATELY AFTER MIXING AND 24 HR AFTER MIXING WERE ESSENTIALLY THE SAME IF THE SAMPLES WERE PREPARED TO THE SAME DENSITY. A 4% LIME TREATMENT WAS FOUND TO BE AN EFFECTIVE STABILIZER OF THE ORGANIC EXPANSIVE CLAY. STRENGTH IMPROVEMENT IN THE AS-CURED SAMPLES WAS NOT GREAT. HOWEVER, THE EFFECTIVENESS OF LIME IN REDUCING THE SWELL OF SAMPLES SOAKED UNDER A SURCHARGE PRESSURE OF 0.1 KG PER SQ CM WAS VERY MARKED AND RESULTED IN SOAKED STRENGTHS OF TREATED SAMPLES UP TO SEVEN TIMES GREATER THAN FOR UNTREATED SAMPLES. PEAK COMPRESSIVE STRENGTH WAS DEVELOPED AT CONSIDERABLY LOWER STRAINS FOR TREATED THAN FOR UNTREATED SAMPLES. A CONSIDERATION OF THE DATA AND THE RESULTS OF CHEMICAL ANALYSES SUGGESTS THAT, FOR THE SOIL STUDIED, THE BENEFICIAL EFFECTS OF LIME TREATMENT ARE CAUSED PRIMARILY BY FLOCCULATION OF THE SOIL STRUCTURE AND A DECREASE IN THE WATER SENSITIVITY OF THE CLAY MINERALS. CEMENTATION EFFECTS ARE BELIEVED TO BE OF MINOR IMPORTANCE IN THIS SOIL. /AUTHOR/

Reactions between calcium oxide and flue gas containing sulfur dioxide at lower temperatures

Abstract: An experimental study has been performed of the reactions occurring when the reactive particles of calcium oxide are exposed to sulfur dioxide bearing flue gas. Using a differential, fixed-bed reactor, kinetic measurements have been made in the temperature range of 170 and 580C. A relatively simple correlation based on the amassed data has been proposed. This correlation allows the estimation of the reaction rate as a function of temperature, conversion of the solids and concentration of sulfur dioxide in the gas phase. The proposed rate law equation makes it possible to predict in a straightforward manner the rate of sorption which would be required to design the performance of a desulfurization unit.

Studies on the Acid Resistance of E Glass

Abstract: The acid resistance of E glass was studied by treating the material in HC1. During the acid treatment, nonsiliceous ions were leached out from the glass structure, due to ion exchange. The parameters which govern the removal are the concentration of the acid, time of contact, and acid temperature. At lower acid concentrations (<2N), calcium oxide and aluminum oxide could not be removed completely. By increasing the concentration of the acid to 4N, most of the nonsiliceous ions were leached out. The number of ions removed increases with the increase in treatment time and temperature. When the glass was treated with 4N HCI for a long time, there was a fluctuation in the total number of ions removed. The teachability of E glass is explained using the Muggins formula and the R2O/SiO2 ratio.

Method for increasing the rate of compressive strength gain in hardenable mixtures containing fly ash

Abstract: The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention provides a method for increasing the rate of strength gain of a hardenable mixture containing fly ash by exposing the fly ash to an aqueous slurry of calcium oxide (lime) prior to its incorporation into the hardenable mixture. The invention further relates to such hardenable mixtures, e.g., concrete and mortar, that contain fly ash prereacted with calcium oxide. In particular, the fly ash is added to a slurry of calcium oxide in water, prior to incorporating the fly ash in a hardenable mixture. The hardenable mixture may be concrete or mortar. In a specific embodiment, mortar containing fly ash treated by exposure to an aqueous lime slurry are prepared and tested for compressive strength at early time points.

Method and means for capture and long-term sequestration of carbon dioxide

Abstract: The invention teaches a practical method of recovering CO 2 from a mixture of gases, and sequestering the captured CO 2 from the atmosphere for geologic time as calcium carbonate and provides a CO 2 scrubber for carbon capture and sequestration. CO 2 from the production of calcium oxide is geologically sequestered. A calcium hydroxide solution is produced from the environmentally responsibly-produced calcium oxide. The CO 2 scrubber incorporates an aqueous froth to maximize liquid-to-gas surface area and time-of-contact between gaseous CO 2 and the calcium hydroxide solution. The CO 2 scrubber decreases the temperature of the liquid and the mixed gases, increases ambient pressure on the bubbles and vapor pressure inside the bubbles, diffuses the gas through intercellular walls from relative smaller bubbles with relative high vapor pressure into relative larger bubbles with relative low vapor pressure, and decreases the mean-free-paths of the CO 2 molecules inside the bubbles, in order to increase solubility of CO 2 and the rate of dissolution of gaseous CO 2 from a mixture of gases into the calcium hydroxide solution. The CO 2 scrubber recovers gaseous CO 2 directly from the atmosphere, from post-combustion flue gas, or from industrial processes that release CO 2 as a result of process. CO 2 reacts with calcium ions and hydroxide ions in solution forming insoluble calcium carbonate precipitates. The calcium carbonate precipitates are separated from solution, and sold to recover at least a portion of the cost of CCS.