A Study on Cement Made by Partially Replacing Cement Raw Materials with Municipal Solid Waste Ash
The use of Municipal Solid Waste incinerator bottom ash (MSWI) and Calcium Carbide Waste (CCW) as a part of cement raw material was investigated. The purpose was not only to dispose of the wastes, but also to alleviate some environmental problems, by reducing resources usage, CO 2 emissions and energy consumption in cement manufacturing. The replacement of MSWI and CCW in raw meal was 5 and 10 percent. Chemical composition and general characteristics, as well as setting times and compressive strength, of the MSWI cements and CCW cements were tested and compared with conventional cement. The chemical compositions of MSWI cements and CCW cements were similar to the control cement, except that the SiO 2 component in MSWI cements was higher than that in control cement but the CaO component was lower. Setting times of cement pastes were slightly different when MSWI and CCW were used as raw materials in cement. The longer setting times of these cement pastes than those of control cement is due to lower C 3 S and higher C 2 S levels than in CC. Compressive strength of CCW cement mortars was closed to that of the CC cement, whereas compressive strength of mortar produced from MSWI cements was rather smaller than the control cement mortar, especially at higher MSWI percentags.
Properties of cement made by partially replacing cement raw materials with municipal solid waste ashes and calcium carbide waste
Abstract An investigation on using municipal solid waste incinerator bottom ash (MSWI) and calcium carbide waste (CCW) as a part of the cement raw materials was performed. Cement raw meals were replaced by 5% and 10% of MSWI and CCW to study properties of the laboratory produced MSWI and CCW cements. Chemical composition, setting times, compressive strength and expansion in sulfate solution of the pastes and mortars made of MSWI cements and CCW cements were tested and compared with these made of conventional cement. It was found from the study that the chemical compositions of MSWI cements and CCW cements were similar to that of the control cement. However, SiO 2 content of MSWI cements was higher than that of the control cement, whereas CaO content was lower. Setting times of cement pastes were slightly delayed when MSWI or CCW were used to replace a part of raw meal in cement production. The longer setting times of these cement pastes were observed due to the lower C 3 S but higher C 2 S content than those in the control cement. Compressive strength of CCW cement mortars was close to that of the control cement. However, compressive strength of the mortars produced from MSWI cements was smaller than that of the control cement mortar, especially when the percentage of MSWI in the raw meal was increased. When compared to the control cement, the performance of MSWI cement and CCW cement in sodium sulfate solution was superior due to the lower C 3 S and C 3 A.
An Ultrasensitive Analytical Method Based on Chemiluminescence Sensing Electrochemical Parallel Catalytic Reaction Event
An ultrasensitive electrochemiluminescence (ECL) method on the combination of electrochemical parallel catalytic reaction and chemiluminesence signal sensing was proposed for improving ECL analytical characteristics using vanadate(V) as a representative. Vanadate(V) could be electrochemically reduced to generate vanadate(II) which could be chemically oxidized by potassium periodate to regenerate vanadate(V) and give parallel catalytic wave effect. Then, the reduced product of potassium periodate could react with butyl-rhodamine B to emit a sensitive chemiluminescence signal. The chemiluminescence intensity was correlative with vanadate(V) concentration. The investigation on the electrochemical reaction rate constant (k0) confirmed that the speed of electrochemical reaction was faster than that of the subsequent chemiluminescence reaction. The possibility of the combination of electrochemical parallel catalytic reaction with chemiluminescence signal sensing was proved. The similar ECL behaviors could be observed at zirconia nanowires-Nafion modified electrode. Because of the separation and enrichment effect of the modified electrode on vanadate(V), the selectivity and sensitivity was further improved greatly. Based on these findings, a new concept on the combination of electrochemical parallel catalytic reaction and chemiluminesence signal sensing was proposed and an ultrasensitive ECL method for the determination of vanadate(V) was developed at zirconia nanowires-Nafion modified electrode. Under the optimum experimental conditions, the ECL intensity was linear with the concentration of vanadate(V) in the range of 2.0×10−12 mol/L–2.0×10−10 mol/L. The detection limit was 8.0×10−13 mol/L, which was more than 6 orders of magnitude lower than that observed by electrochemical current transduction for electrochemical parallel catalytic reaction at zirconia nanowires-Nafion modified electrode.