A Paolini

Optimization of the solidification/stabilization process of MSW fly ash in cementitious matrices.

The solidification/stabilization (S/S) process of municipal solid waste (MSW) fly ash in cementitious matrices was investigated in order to ascertain the feasibility of a washing pretreatment of fly ash with water as a means of maximizing the ash content of cementitious mixtures. Four types of fly ash resulting from different Italian MSW incineration plants and ASTM Type III Portland cement were used in this study. Ash-cement mixtures with different fly ash/cement (FA/C) ratios were made using untreated and washed fly ash. Washing of fly ash with water was realized by a two-stage treatment (liquid/solid=25; mixing time=15 min for each stage). The cementitious mixtures were characterized for water demand, setting time, mechanical strength, and heavy metals leachability. Comparison between the above properties of mixtures incorporating untreated and washed fly ash (particularly, setting characteristics), coupled with economical evaluation of the S/S process when applied to untreated and washed fly ash, proved the feasibility of washing pretreatment as a means of maximizing the incorporation of MSW fly ash in cementitious matrices (ash content up to 75%-90% by weight of total solid).

Total gastrectomy in the treatment of adenocarcinoma of the cardia: Review of the results in 73 resected patients

Between January 1, 1971, and December 31, 1978, 73 patients with adenocarcinoma of the cardia were treated by total gastrectomy with distal esophagectomy. The continuity of the alimentary tract was restored by esophagojejunostomy using a Roux-Y procedure in 32 patients and jejunal loop interposition in 41 patients. The early postoperative mortality rate was 18 percent. The overall 5 year survival rate was 26.7 percent, and the 5 year survival rate for stage I and II disease was 91.6 percent and 25 percent, respectively, whereas none of the stage III and IV patients survived more than 4 years. Fifty-eight percent of the patients without nodal involvement lived more than 5 years. The 5 year survival rate was only 9.3 percent in the presence of nodal metastases. Our 5 year survival rates suggest the value of elective total gastrectomy for stage I or II adenocarcinoma of the cardia. Jejunal loop interposition is a time-consuming but functionally superior procedure in comparison to other reconstructive procedures after total gastrectomy.

Belsey and Nissen operations for gastresophageal reflux

From 1972 to 1985, 37 consecutive patients underwent primary Belsey repair and 40 consecutive patients underwent primary Nissen fundoplication because of reflux disease. The operative procedures were performed by a single surgeon in each group. For the purpose of comparison, both groups were divided into two subsets: (1) patients with proved reflux, and (2) patients with different indications. The first subset consisted of 30 patients in the Belsey series and 32 in the Nissen series. The remaining patients were included in the second subset. One death occurred in the Belsey series; morbidity consisted of minor pulmonary complications in the Belsey series (10.8%) and spleen injuries requiring splenectomy (5%) in the Nissen series. In patients with proved reflux good-to-excellent results were achieved in 89.3% of subjects of the Belsey series and 86.6% of patients of the Nissen group. The failures rates were 7.1% and 10%, respectively. Inability to vomit and/or belch was reported in 7.1% of patients with proved reflux of the Belsey group and 10% of patients with proved reflux of the Nissen group. In patients with different indications there were no failures after either operation. Finally 82.2% of subjects in the Belsey group and 73.3% of patients in the Nissen group declared that they were satisfied with the operative results. In conclusion the Belsey and the Nissen procedures are equally able to achieve long-term control of reflux disease in comparable groups of patients. Failures and gastrointestinal symptoms are equally frequent after either procedure and do not affect the overall patient acceptance of antireflux surgery.

RAPID EVALUATION OF THE THRESHOLD ALKALI LEVEL FOR ALKALI-REACTIVE SILICEOUS AGGREGATES IN CONCRETE

Abstract A modified version of the ultra-accelerated concrete prism expansion test in alkaline solutions at 150°C (testing concrete mixes at varying alkali content of concrete) was investigated in order to ascertain the reliability of this test method for evaluating the threshold alkali levels (TAL) of alkali-reactive siliceous aggregates in concrete. Five natural sands of known field performance were tested and their TAL values determined by the ultra-accelerated test were compared with those obtained from concrete prism expansion tests at 38°C and 100% RH. A correlation between the threshold alkali level of the sands and their microstructural disorder coefficient, Cd, as measured by infrared spectroscopy, was also attempted. The modified ultra-accelerated concrete prism test proved to be a rapid and reliable method for evaluating the threshold alkali level of reactive siliceous aggregates in concrete, provided that an expansion limit of 0.11% at 3 weeks was taken as the reactivity judgement criterion for this test. The threshold alkali level proved to be an appropriate reactivity parameter for the selection of alkali-reactive siliceous aggregates. Also, the existence of a straight-line relationship between TAL and Cd suggested the possibility of developing a new test methodology for estimating TAL, based on Cd measurements by infrared spectroscopy.

APPLICATION OF THE NAOH BATH TEST METHOD FOR ASSESSING THE EFFECTIVENESS OF MINERAL ADMIXTURES AGAINST REACTION OF ALKALI WITH ARTIFICIAL SILICEOUS AGGREGATE

Abstract The use of the mortar bar expansion test in a 1 M NaOH solution at 80°C as a means of assessing the effectiveness of fly ash and silica fume against alkali-silica reaction was investigated using fused quartz as reactive aggregate. Long-term ASTM C227 test results were utilized for comparative purposes. The NaOH bath test provides reasonable results about the minimum contents of fly ash and silica fume needed to prevent deleterious expansion in mortars containing fused quartz. Particularly for silica fume, agreement between the minimum admixture contents predicted by the two test methods is found only when the expansion limits of 0·25% at 12 days and 0·10% at 1 year or, alternatively, 0·15% at 14 days and 0·05% at 1 year are used for the NaOH bath and ASTM C227 test methods, respectively. A consistent relationship exists between the expansion of mortar bars and the Na + ion concentration in the pore solution after 14 days immersion of the specimens in the NaOH solution. With both test methods there is no direct correlation between the performance of fly ashes and their total and available alkali contents.

Evaluation of the leachability of heavy metals from cement-based materials

A new leaching test on comminuted (0.125-2.0mm gradation) cementitious matrices, designated as Modified-Pore Water (M-PW) test, was developed to evaluate the effect of varying leachate pH (4-12.8) and/or liquid-to-solid, L/S, ratio (0.6-50 dm(3)/kg) on the availability factor, F(AV), of heavy metals. The M-PW test was applied to leaching of lead and zinc ions from ground Portland cement mortar incorporating Municipal Solid Waste Incinerator (MSWI) fly ash. Correlation of M-PW test results (F(AV)-L/S data) allowed the determination of the pore-liquid availability factor, F(AVP), at different leachate pHs. These F(AVP) values were utilized, in conjunction with a kinetic pseudo-diffusional model, to evaluate the leaching behavior of monolithic mortar specimens subjected to dynamic leaching tests (constant leachant pH 4 or 6).A good agreement was found between the effective diffusion coefficients, D(e), of lead and zinc ions calculated by such a methodological approach and those obtained from recognized microstructural models. In contrast, no satisfactory agreement was found when these D(e) values were compared with the ones calculated from the results of other availability tests on granular solid samples (NEN 7341 and AAT tests).

Reuse of Woody Biomass Fly Ash in Cement-Based Materials: Leaching Tests

The feasibility of using woody biomass fly ash (WBFA) as a mineral admixture in cement-based materials was investigated. This fly ash was characterized for chemical composition and used to prepare a cement blend with 70 wt% Portland cement and 30 wt% WBFA. Cubic specimens were cast from a blended cement paste (water-to-binder ratio 0.50) and, after 28 days of curing at 20°C and 100% relative humidity, these specimens were tested for heavy metal leachability through the use of a sequential leaching protocol, at a constant pH of leachant (deionized water; pH 6.0). It was found that, except for the chloride content, the WBFA is able to meet the European chemical requirements established for reuse of coal fly ash in cement-based materials. Although the WBFA is characterized by a significant content of heavy metals of particular environmental concern (Cd, Cr, Cu, Ni, Pb, Zn), the results of the monolith leaching test have shown a good immobilization capacity of such metals by the cementitious matrix and, consequently, a good environmental quality of the blended cement investigated.

Alkali Release from Aggregates in Long-Service Concrete Structures: Laboratory Test Evaluation and ASR Prediction

This paper proposes a simple model for predicting the development of deleterious expansion from alkali-silica reaction (ASR) in long-service concrete structures. This model is based on some composition and reactivity parameters related to ASR, including the long-term alkali contribution by aggregates to concrete structures. This alkali contribution was estimated by means of a laboratory extraction test, appositely developed in this study in order to maximize the alkali extraction within relatively short testing times and with low leaching solution/aggregate ratios. The proposed test is a modification of the Italian Standard test method UNI 11417-2 (Ente Nazionale Italiano di Normazione) and it consists of subjecting an aggregate sample to leaching with saturated calcium hydroxide solution in a laboratory autoclave at 105 °C. Nine natural ASR-susceptible aggregates (seven sands and two coarse aggregates) were tested and the following optimized test conditions were found: leaching solution/aggregate weight ratio = 0.6; solid calcium hydroxide/aggregate weight ratio = 0.05; test duration = 120 h. The results of the optimized alkali extraction tests were used in the proposed model for predicting the potential development of long-term ASR expansion in concrete dams. ASR predictions congruent with both the field experience and the ASR prevention criteria recommended by European Committee for Standardization Technical Report CEN/TR 16349:2012 were found, thus indicating the suitability of the proposed model.

Residual Capability of Alkali Binding by Hydrated Pozzolanic Cements in Long-Service Concrete Structures

An experimental procedure was developed and applied to cement pastes made with two different pozzolanic cements (CEM IV/B (P) and CEM IV/B (V)) in order to ascertain the existence of a residual capability of alkali binding by long-term hydrated pozzolanic cements and, at the same time, to evaluate the alkali retention capability and the concentration of OH− ions in the pore solution of such cementitious matrices. The developed procedure consisted of accelerated curing of cement paste specimens (150 days at 60°C and 100% RH), subsequent leaching tests at 60°C for 30 days by using deionized water or basic solutions (NaOH or KOH at different concentrations) as leaching media, and correlation of the leaching test results with a simple mass balance equation for sodium and potassium ions. The developed procedure was found to be appropriate for evaluating both the pore liquid alkalinity and the alkali retention capability by long-term hydrated pozzolanic cement pastes. A residual capability of alkali binding was also identified for both tested pozzolanic cements, thus indicating their potential ability to prevent (CEM IV/B (V)) or minimize (CEM IV/B (P)) the risk of deleterious expansion associated with alkali-aggregate reaction in long-service concrete structures, like concrete dams.

Esophagomyotomy with Antireflux Procedures for Achalasia of the Esophagus: Clinical Comparison of Nissen Fundoplication and Belsey Mark IV

Treatment of achalasia of the esophagus continues to be subject of debate. Modified Heller’s myotomy and forceful dilatation are widely accepted as the treatment of choice [4]. However, a definite incidence of esophagitis and stenosis have been observed following Heller’s operation [1, 3], suggesting the addition of reconstruction of the cardia and hiatal hernia repair to myotomy with the purpose of preventing postoperative reflux [2, 5]. In our institution antireflux procedures associated with myotomy have been performed since 1972. Therefore in this study we compare the clinical results of total fundoplication (Nissen procedure) and partial fundoplication (Belsey Mark IV) added to myotomy for treatment of achalasia of the esophagus.