Effect of using limestone fines on the chemical shrinkage of pastes and mortars

Environmental Science and Pollution Research - The main aim of this study is to examine the effect of incorporating limestone fine (LF) on chemical shrinkage of pastes and mortars. For this...     

Numerical integration of chemical ODE problems arising in air pollution models

The numerical treatment of a regional air pollution model (such models are, as a rule, described mathematically by systems of partial differential equations) leads to the solution of very large computational problems. The chemical submodel of an air pollution model is normally the most timeconsuming part of the computational work. The application of appropriate discretization and splitting procedures reduces the chemical submodel to a large number of relatively small ODE systems (one such system per gridpoint). In the process of searching for efficient numerical algorithms for the chemical submodels one can carry out experiments by using only one such ODE system in order to facilitate the work. This approach has been used in connection with a particular chemical scheme, the condensed CBM IV scheme, which is used in several large air pollution models. Six integration algorithms have been tested on a set of typical scenarios (consisting of different starting concentrations and/or of different values of the emissions). The advantages and the disadvantages of the algorithms tested are discussed. The final decision about the most efficient algorithm, among the algorithms tested, should be made after a second series of experiments. The coupling of the chemical process with the transport of air pollution (on, at least, a twodimensional domain) together with the application of highspeed computers has to be studied in the second series of experiments, which will be performed in a subsequent paper.     

Hydrostratigraphy and hydrogeology of the western part of Maira area, Khyber Pakhtunkhwa, Pakistan: a case study by using electrical resistivity

Hydrostratigraphy and hydrogeology of the Maira vicinity is important for the characterization of aquifer system and developing numerical groundwater flow models to predict the future availability of the water resource. Conventionally, the aquifer parameters are obtained by the analysis of pumping tests data which provide limited spatial information and turn out to be costly and time consuming. Vertical electrical soundings and pump testing of boreholes were conducted to delineate the aquifer system at the western part of the Maira area, Khyber Pakhtun Khwa, Pakistan. Aquifer lithology in the eastern part of the study area is dominated by coarse sand and gravel whereas the western part is characterized by fine sand. An attempt has been made to estimate the hydraulic conductivity of the aquifer system by establishing a relationship between the pumping test results and vertical electrical soundings by using regression technique. The relationship is applied to the area along the resistivity profiles where boreholes are not drilled. Our findings show a good match between pumped hydraulic conductivity and estimated hydraulic conductivity. In case of sparse borehole data, regression technique is useful in estimating hydraulic properties for aquifers with varying lithology.     

Industrial hygiene and toxicity studies in unorganized bone-based industrial units

A large variety of ornamental and decorative items are manufactured from bone waste by various unorganized sectors in India. An initial survey indicated that workers were exposed at various phases of final product. The subjects (12 industrial units) were tested for total suspended particulate matter (TSPM), particulate matter <10  $\upmu $ m (PM₁₀), and particulate matter <2.5  $\upmu $ m (PM_2.5). Prevalent levels of TSPM ranged between 2.90 and 5.89 mg m^???3. Respirable fractions of occupational dust as PM₁₀ and PM_2.5 were found in the range of 0.30?C2.08 and 0.26?C0.50 mg m^???3, respectively. Cytotoxicity study was conducted using hemolysis as a sensitive marker. In an in vitro study, rat RBCs were exposed to the concentration of 25?C1,000  $\upmu $ g/ml for 15?C120 min. A considerable variation was observed in the hemolytic activity of samples collected from different areas. At 500  $\upmu $ g/ml concentration, the hemolytic activity (12 h) was found to be in the range of 18?C25%. Due to limitation in sample mass of respirable fractions, only one concentration (100  $\upmu $ g/ml/2 h) was used for comparative study on hemolysis of RBCs caused by PM₁₀ and PM_2.5. Interestingly, the hemolytic activity was more at PM_2.5 than PM₁₀ and TSPM. These results suggest that the respirable particles are capable of reaching deep into the respiratory system. The finding is significant notably when there are no standards available in occupationally exposed populations. This is the first such study. Data could be of importance to policy makers and regulators.     

Degradation of Polyethylene Designed for Agricultural Purposes

For many years now, scientific articles have been published on the potential biodegradability of polyethylene. Polyethylene (PE) with peroxidant additives, in the form of agricultural films, is sold by various suppliers as biodegradable mulch. Even though, the photo-chemical and thermal degradation of these products under artificial laboratory conditions is highlighted, several extrapolation on the biodegradation and, moreover, on the neutral environmental impact of PE are made. In this study, three different commercial mulch films have been submitted to standardised biodegradation tests and the results are discussed. The first conclusions are that a very low degree of biodegradation of the commercial PE films is achieved from these tests and that crosslinked PE micro-fragments are found in soil after a very long period of time.     

Investigating mechanical properties and durability of concrete containing recycled rubber ash and fibers

This article investigates the suitability of utilizing end of life rubber tyre particles in concrete as fine aggregate. Rubber ash and rubber fibers were used to develop two series of rubber ash concrete (series I) and hybrid concrete (series II) mixes. The natural fine aggregate was replaced by rubber ash (by volume of 5%, 10%, 15% and 20%) in series I; whereas in series II, the amount of rubber ash was kept constant at 10% and rubber fiber was introduced as replacement of fine aggregate (by volume of 5%, 10%, 15%, 20% and 25%). The concrete mixes were evaluated for compressive strength, flexural strength, resistance to impact loading, fatigue loading, water penetration and shrinkage strain was evaluated. It was observed that inclusion of rubber ash resulted in the improvement of impact resistance of concrete. The results also show that up to 10% rubber ash and rubber fibers can be utilized as fine aggregate to develop feasible and durable rubberized concrete pavements, crash barriers and paver blocks.

     

Flyash-based bricks: an environmental savior—a critical review

Journal of Material Cycles and Waste Management - The extraction of unsustainable natural resources like sand and topsoil for construction is disturbing ecological balance, affecting local...     

Mechanical,durability and microstructural assessment of geopolymer concrete incorporating fine granite waste powder

Journal of Material Cycles and Waste Management - This research investigation has mainly focused on the development of cementless concrete, i.e., geopolymer concrete, along with the reutilization...     

Rice straw ash extract, an efficient solvent for regioselective hydrothiolation of alkynes

Environmental Chemistry Letters - Herein, we describe a simple and inexpensive protocol for the hydrothiolation of alkynes. In this context, water extract of rice straw ash (WERSA) has been proven...     

Properties of concrete containing scrap-tire rubber--an overview

Solid waste management is one of the major environmental concerns in the United States. Over 5 billion tons of non-hazardous solid waste materials are generated in USA each year. Of these, more than 270 million scrap-tires (approximately 3.6 million tons) are generated each year. In addition to this, about 300 million scrap-tires have been stockpiled. Several studies have been carried out to reuse scrap-tires in a variety of rubber and plastic products, incineration for production of electricity, or as fuel for cement kilns, as well as in asphalt concrete. Studies show that workable rubberized concrete mixtures can be made with scrap-tire rubber. This paper presents an overview of some of the research published regarding the use of scrap-tires in portland cement concrete. The benefits of using magnesium oxychloride cement as a binder for rubberized concrete mixtures are also presented. The paper details the likely uses of rubberized concrete.