Hardened concrete properties and durability assessment of high volume fly ash concrete

Concrete is produced more than any other material in the world. Sustainable construction is extremely important in today\u27s industry and fly ash is the leading material for sustainable concrete design. The addition of fly ash improves many fresh and hardened concrete properties. However, the slow hydration process associated with fly ash makes the use of the material in large amounts undesirable in conventional construction. This study evaluated the hardened concrete and durability performance of several high-volume fly ash (HVFA) concrete mixes. The various HVFA concrete mixes evaluated within this study consisted of 70 percent replacement of portland cement by weight of cementitious material and water-to-cementitious ratios (w/cm) ranging from 0.30 to 0.45. Studies were conducted on hardened properties including: compressive strength, flexural strength, splitting tensile strength, and modulus of rupture. A shrinkage analysis was also performed to evaluate drying and free shrinkage. The durability performance of the HVFA concrete was also evaluated. Results obtained from the tests revealed that compressive strengths of HVFA concrete are comparable to portland cement concrete with a reduced w/cm. Also, a reduction in concrete shrinkage was observed for HVFA concrete. The durability testing showed HVFA concrete increased the corrosion resistance and decreased the chloride penetration. Finally, existing relationships for hardened material properties and durability of conventional concretes are applicable to HVFA concretes --Abstract, page iii

Twin Row vs. Single Row Spacing at Variable Seeding Rates

As corn production practices improve, row widths decrease. Although most producers plant in 30-in. rows, more and more acres are being planted to narrower row widths (15 in. to 20 in.). In addition, plant populations continue to increase every year with the introduction of more stress-tolerant hybrids. Wider row widths force more plants into a concentrated area, whereas narrower rows allow more equidistant spacing of plants

Corn Planting Date

Producers attempt to plant corn earlier every year. For example, in 2006, 50% of the statewide crop was planted by approximately April 25. Earlier planting dates are attributed to several causes: larger acreage per producer, less spring tillage, advancements in hybrids, and seed treatments. However, in contrast to this, Iowa producers in 2008 did not have half of Iowa’s corn acreage planted until May 13 due to weather. This is 18 days later than 2006. Planting the crop during the optimum window is one management practice that is generally important in achieving high yields

A comparative analysis of fuel price forecasts

A comparative analysis of four sets of fuel price forecasts is made for each of the four primary energy sources: coal, oil, natural gas and uranium. These forecasts, together with historical data over the period from 1960 to 1977, are presented in graphical and tabular form to the year 2000. A graphical summary is then made of a synthesized forecast considered most likely for each fuel, plotted in common units of 1977 cents per million BTU, showing relative trends among competing energy forms

Disparities in the distribution of municipal services

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering; and, (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 1971.Bibliography: leaves 148-151.by Robert Marlay.M.C.P.M.S

Regional Corn Re-plant Recommendations for Iowa

Each year in areas where corn (Zea mays L.) is grown, biotic and abiotic (living and nonliving) factors can prevent timely planting or reduce stands so severely that yield potential may be reduced to unsatisfactory levels. Once these threats are realized, producers must make quick and accurate decisions. Careful evaluation of the current situation in terms of projected yields and profitability is crucial. If projected profitability is not acceptable, replant options should be considered

Factores asociados a la persistencia de anemia en parturientas en el Instituto Nacional Materno Perinatal, marzo-abril 2017

Determina los factores asociados a la persistencia de anemia en parturientas atendidas en el Instituto Nacional Materno Perinatal. Desarrolla un estudio de casos y controles que tuvo una muestra de 120 parturientas, divididas en 60 parturientas con persistencia de anemia hasta el momento del parto (casos) y 60 parturientas que no presentaron diagnóstico de anemia en el momento del parto (controles). A las cuales se aplicó una encuesta donde se indagó sobre los factores personales, relacionados al sistema sanitario y obstétrico. Encuentra que los factores personales asociados a la persistencia de anemia fueron: apoyo de la familia, confianza en el tratamiento, adherencia al tratamiento, abandono por completo el tratamiento recetado. El factor obstétrico asociado fue el nivel de hemoglobina en el primer examen. Los factores relacionados al sistema sanitario asociados fueron: tiempo de consulta adecuado en la atención prenatal, si el personal explicó sobre los riesgos de la anemia en el embarazo, receta de algún antianémico, orientación nutricional, monitoreo del tratamiento, facilidad para adquirir el medicamento. Concluye que existen factores personales, obstétricos y relacionados al sistema sanitario asociados a la persistencia de anemia en las parturientas.Tesi

Understanding corn development: A key for successful crop management

The new publication, Corn Growth and Development, will be released January 2011 (Abendroth et al., 2011) and replaces How a Corn Plant Develops, Special Report 48 by Iowa State University (Ritchie et al., 1986). Corn Growth and Development (CGD) highlights include: Text based on new corn growth and development research; Images of the plant above- and below-ground; Timelines showcasing crop development across large periods of time; and Season-long nutrient and biomass accumulation curves derived from ISU research conducted during 2007 and 2008