Role of casting and curing conditions on the strength and drying shrinkage of greener concrete

The shrinkage of cement-based materials is a critical dimensional property that needs proper attention as it can influence the corresponding characteristics especially when the preparation of such cement-based material is done in hot weather. Studies have shown that the casting or curing conditions influence the performance of concrete. However, there is limited understanding of the combined role of casting temperature and curing conditions, especially for concrete made with unconventional binders. In this study, five supplementary cementitious materials (SCMs) were utilized as the substitute of the ordinary Portland cement (OPC) at different ratios to produce greener concrete and improve its characteristics and sustainability. The influence of four casting temperatures (i.e., 25 °C, 32 °C, 38 °C, and 45 °C) and two curing regimes (i.e., covering of samples using wet burlap and applying curing compound on the surface of samples) on the corresponding compressive strength and drying shrinkage at various ages was studied. The outcomes of this research revealed that the composition of the binders has a substantial impact on the characteristics of concrete. In addition, the casting temperature and curing regimes also have a huge role on the compressive strength of concrete produced with binary binders. For example, the compressive strength at 3 days of concrete made at 25 °C made with binary binders was reduced up to 31% compared to that made with only OPC as the binder when cured using wet burlap. Nonetheless, less than 38 ℃ was suitable to minimize the durability issues in the studied blended cement mixes.

     

Determination of metal accumulation in deposited street dusts in Amman, Jordan

Street dust samples (120 in total) were collected under stable weather conditions during the hot, dry season (August and September) of 2004 from six different localities (industrial, heavy traffic, medium traffic, light traffic, low traffic and rural) in greater Amman, the capital of Jordan. The concentrations of Fe, Cu, Cd, Pb, Zn and Ni in the dusts were determined by atomic absorption spectrophotometry. The high concentrations of Pb, Fe and Zn in the street dust samples were related to both anthropogenic (industrial sources combined with traffic sources) and natural sources. Surprisingly, the concentrations of Cd in the dusts were low. Correlation coefficient analysis and principle component analysis identified three main sources of these elements and the corresponding distributions. The elements Pb, Zn, Cd, Fe, Cu and Ni were mainly derived from industrial sources, with Pb and Zn additionally derived from traffic sources. The street dusts were found to have highly elevated levels of Zn, particularly along the main trunk roads, indicating that the Zn in the street dusts may be derived from traffic sources, especially vehicle tyres. The concentrations of metals in the different street dust samples were found to vary depending on the density of traffic.     

Vaquita Bycatch in Mexico's Artisanal Gillnet Fisheries: Driving a Small Population to Extinction

Abstract: The world's most endangered marine cetacean, the vaquita (   Phocoena sinus ), continues to be caught in small-mesh gillnet fisheries throughout much of its range. We monitored fishing effort and incidental vaquita mortality in the upper Gulf of California, Mexico, from January 1993 to January 1995 to study the magnitude and causes of the incidental take. Of those factors studied, including net mesh size, soaktime, and geographic area, none contributed significantly to the incidental mortality rate of the vaquita, implying that the principal cause of mortality is fishing with gillnets per se . The total estimated incidental mortality caused by the fleet of El Golfo de Santa Clara was 39 vaquitas per year (95% CI = 14, 93), over 17% of the most recent estimate of population size. El Golfo de Santa Clara is one of three main ports that support gillnet fisheries throughout the range of the vaquita. Preliminary results indicate that fishing effort for San Felipe, Baja California, is comparable to that of El Golfo de Santa Clara, suggesting that this estimate of incidental mortality of vaquitas represents a minimum. We strongly recommend a complete and permanent ban on gillnets in the area. Alternative or supplemental mitigation strategies include (1) a maximum annual allowable mortality limit of vaquitas; (2) mandatory observer coverage of all boats fishing within the Upper Gulf of California and Colorado River Delta Biosphere Reserve; (3) extension of the Upper Gulf of California and Colorado River Delta Biosphere Reserve to encompass all known vaquita habitat; (4) rigorous enforcement of new and existing regulations; and (5) development of alternative sources of income for gillnet fishers.     

Effects of oxidants on soybean growth and yield in the Pakistan Punjab.

Plants of soybean (Glycine max L.) were grown with and without the ozone protectant EDU (N-[2-(2-oxo-1-imidazolidinyl)ethyl]-n2 phenylurea) at a suburban site, a remote rural site and a rural roadside site around the city of Lahore, Pakistan. The development and yield of the plants was determined in two experiments--one immediately post-monsoon and one in the following spring (pre-monsoon). Concentrations of nitrogen dioxide and photochemical oxidants were measured at each site. The effect on yield of EDU at the suburban site (47 and 113% increase in seed weight per plant relative to the untreated plants in the post- and pre-monsoon experiments, respectively) was similar to the effects of filtration on yield on soybean in a parallel open-top chamber study at the same site (77% increase relative to plants subjected to unfiltered air for the pre-monsoon experiment). Effects of EDU on yield were greater at both rural sites than at the suburban site in both experiments, and greater in the spring experiment (182% at the remote rural site and 285% at the rural roadside site) than in the post-monsoon experiment (94% at the remote rural site and 170% at the rural roadside site); oxidant concentrations were also greater at the rural sites than at the suburban site, and greater in the spring experiment than the post-monsoon experiment. The results imply that ozone may be causing significant crop losses in rural areas around Lahore; however, the geographical extent of the problem, and the implications for peri-urban agriculture around other cities of south Asia are uncertain.     

Numerical parametric study of a new earth-air heat exchanger configuration designed for hot and arid climates

ABSTRACT

Thermal potential for cooling and heating can be achieved by new configuration of earth–air heat exchanger (EAHE). This paper presents a numerical investigation of thermal performance of a spiral-shaped configuration of EAHE intended for the summer cooling in hot and arid regions of Algeria. A commercial finite volume software (ANSYS FLUENT) has been used to carry out the transient three-dimensional simulations and the obtained results have been validated using the experimental and numerical data obtained from the literature. The agreement between our simulation results and those from literature is very satisfactory. A parametric analysis of the new geometry of (EAHE) has been performed to investigate the effect of pitch, depth, pipe length and of the flow velocity on the outlet air temperature and the EAHE’s mean efficiency as well as its coefficient of performance (COP). It has been shown that when the pitch space varies between 0.2 and 2 m the difference of outlet air temperature increases by 6 ^°C. When the air velocity increases from 2 to 5 m/s the mean efficiency decreases from 60 % to 33 % and the COP of the EAHE decreases from 2.84 to 0.46.     

COST COMPARISON BETWEEN CESSPOOL AND SANITARY SEWERAGE SYSTEMS IN SAUDI URBAN AREAS1

ABSTRACT: Extensive use is made of on-site wastewater disposal systems of cesspools due to the absence of a sanitary sewerage system in Saudi urban areas. This system has caused the groundwater table to rise to a public nuisance level. A health risk has also evolved. There are several infrastructural, environmental, and social impacts from this, resulting in great financial losses. Examples are: surface water flooding, damage to foundations of buildings and asphalt street pavements, flooded basements and added construction costs required for excavation, dewatering, insulation materials, and special cements. Most of these costs are indirectly being paid by the private and public sectors. This study compares the estimated costs of damage and losses with the estimated costs of building, operating, and maintaining sanitary sewerage systems in the cesspool-served areas. The annual cost of the cesspool system, depending on the severity of the adverse impacts, ranges from 2.2 to 4.4 times the annual cost of the sanitary sewerage system. Remedies for these impacts are very expensive, and delays in the implementation of the sanitary sewerage facility will make the damage recovery more expensive, and in some cases, impossible. Thus, it is recommended that highest priority to be given to the sanitary sewerage systems in Saudi urban areas.     

USE OF WATER FROM THE ANCIENT MAKKAH GALLERIES FOR IRRIGATION1

ABSTRACT: Due to the spread of Islam in the seventh century the number of pilgrims to the City of Makkah increased sharply, resulting in an acute water shortage. To solve this problem, galleries were built to collect water from the upstream of Wadi Naaman and transfer it to Makkah. Expansion of Makkah and the absence of any mapping of the galleries have resulted in the destruction of a part of the galleries. This caused a discontinuity of flow in the galleries and, consequently, the ground water table is rising at a rate of 0.48 m/yr, causing environmental problems. Research was conducted to rehabilitate the destructed part of the galleries, and to find an appropriate use for the ground water. The study found that the quality of the ground water is suitable for landscaping purposes, that is, for the irrigation of trees and ornamental plants.     

Use of Satellite Imagery as Environmental Impact Assessment Tool: A case Study from the Nw Egyptian Red Sea Coastal Zone

Knowledge and detecting impacts of human activities on the coastal ecosystem is an essential management requirement and also very important for future and proper planning of coastal areas. Moreover, documentation of these impacts can help in increasing public awareness about side effects of unsustainable practices. Analysis of multidate remote sensing data can be used as an effective tool in environmental impact assessment (EIA). Being synoptic and frequent in coverage, multidate data from Landsat and other satellites provide a reference record and bird’s eye viewing to the environmental situation of the coastal ecosystem and the associated habitats. Furthermore, integration of satellite data with field observations and background information can help in decision if a certain activity has caused deterioration to a specific habitat or not. The present paper is an attempt to utilize remote sensing data for assessment impacts of some human activities on the major sensitive habitats of the NW Egyptian Red Sea coastal zone, definitely between Ras Gemsha and Safaga. Through multidate change analysis of Landsat data (TM & ETM+ sensors), it was possible to depict some of the human infringements in the area and to provide, in some cases, exclusive evidences for the damaging effect of some developmental activities.     

Municipal solid waste landfill siting using intelligent system

Historically, landfills have been the dominant alternative for the ultimate disposal of municipal solid waste. This paper addresses the problem of siting a new landfill using an intelligent system based on fuzzy inference. The proposed system can accommodate new information on the landfill site selection by updating its knowledge base. Several factors are considered in the siting process including topography and geology, natural resources, socio-cultural aspects, and economy and safety. The system will rank sites on a scale of 0-100%, with 100% being the most appropriate one. A weighting system is used for all of the considered factors. The results from testing the system using different sites show the effectiveness of the system in the selection process.