Partial Replacement of Limestone and Silica Powder as a Substitution of Cement in Lightweight Aggregate Concrete

With increasing trends towards the broader usage of concrete and warning depletion of natural resources of aggregates, it seems reasonable to find mineral additives or binding materials of different types as ingredient of concrete.  Accordingly, wide usage of light weight concrete lies on some main structural applications as reduction of total dead, seismic loads, environmental pollution, and labour cost. This paper tries to investigate the properties of light weight blended concrete containing lime stone powder (LP), micro-silica (MS), pumice, and leca in various proportioning rateing as a partial replacements of cement. Utilization of these additives on the compressive strength, tensile strength, water absorption coefficient, acid resistance, and impact resistance examined experimentally in various curing conditions at the ages of 7 and 28 days to evaluate the combined effect of micro-silica and lime stone incorporation on strength and durability properties of light weight concrete, along with introduction of optimum replacements. For this purpose, 10 lime-stone based concrete mixtures were prepared with proportions from 0 to 20%, and constant values of 10% micro-silica and w/c ratio. From the results, it was indicated that addition of lime stone powder in concrete reduces short-term properties as well as the compressive strength. Optimum levels of powder replacements can serve as sustainable and durable concrete, also environmental and economic benefits

Experimental Evaluation of Eco-friendly Light Weight Concrete with Optimal Level of Rice Husk Ash Replacement

Concrete is a versatile and cost-effective building material whose properties are influenced by age, curing condition, and installation. A number of studies deduced that there should be an association of benefits encouraged the use of partial replacements of cement seems to improve strength and durability properties of concrete. This paper presents a framework for feasibility assessment and determination of optimum percentage of rice husk ash (RHA) replacement. Five mix plans with RHA replacing ratio of 0-20% and constant micro- silica value by 10% were prepared. Tests results indicated that compressive strength increased by 20% with an increase in RHA up to 15%. The similar trend was observed in mix designs made of cement replaced by RHA up to 20% in water absorption coefficient measurement. Higher chloride ion penetration was observed in mix designs containing 25% RHA compared to that of conventional concrete. Mixes developed a slightly higher impact resistance than the control mix

Applying a basic development needs approach for sustainable and integrated community development in less-developed areas: Report of ongoing Iranian experience

Introduction: Despite considerable achievements in the provision of basic developmental facilities in terms of drinking water, access to primary healthcare services, high-quality and nutritious food, social services, and proper housing facilities, there are many rural and slum communities in Iran where these essential needs remain unfulfilled. Lack of equity is prominent, as large differences exist in underprivileged provinces. New policies developed in the past two decades have resulted in substantial achievements in meeting population needs and reducing the socio-economic gap; nevertheless, poverty levels, unemployment due to a large increase in the birth rate in the early 1980s, and lack of community participation are matters yet to be addressed. To overcome these deficiencies, a basic development needs approach was adopted to promote the concept of community self-help and self-reliance through intersectoral collaboration, creating an environment where people could take an active part in the development process, with the Iranian government providing the necessary support to achieve the desired level of development. Description of the project: Following firm commitment from the Iranian government and technical support from the World Health Organization Regional Office, basic development needs was assigned a high priority in health and health-related sectors, reflected in the third National Masterplan (2001-2005). A comprehensive intersectoral plan was designed, and pilot projects were commenced in three villages. Each village elected a representative, and committee clusters were formed to run and monitor projects identified by a process of local needs assessment and priority assignment. In each region, a variety of needs were elicited from these assessments, which were actively supported by local authorities. Lesson learned: A basic development needs approach was found to be a reliable discipline to improve community participation, needs-led resource allocation and intersectoral co-operation in community development, particularly in underprivileged areas. Iran's initial experience of basic development needs has gained widespread public support but will require periodical evaluation as it is introduced into other rural and urban regions across the country. © 2004 The Royal Institute of Public Health. Published by Elsevier Ltd. All rights reserved

Toxicity assessment of chemical contaminants;transition from in vitromethods to novel in vitro methods

Exposure to occupational and environmental contaminants is a major contributor to human health problems. Despite significant achievements in the risk assessment of chemicals, the toxicological database, particularly for industrial chemicals, remains limited. Considering there areapproximately 80, 000 chemicals in commerce, and an extremely large number of chemical mixtures, in vivo testing of this large number is unachievable from ethical, economical and scientific perspectives. Therefore, increasing the number of available industrial chemicals andnew products has created a demand for alternatives to animal methods for better safety evaluation. Recent toxicity studies have demonstrated that in vitro methods are capable of rapidly providing toxicity information. In this review, current toxicity test methods for risk evaluation of industrial chemical contaminants are presented. To evaluate the potential applications of  more recent test methods developed for toxicity testing of chemical contaminants are discussed. Although  to be considered more broadly for risk assessment of human chemical exposures. In vitro methods,in vitro toxicology methods cannot exactly mimic the biodynamics of the whole body, in vitro  relationships (QSARs) and physiologically based toxicokinetic (PBTK) models have a potentialtest systems in combination with the knowledge of quantitative structure activity

Rice husk ash as a partial replacement of cement in high strength concrete containing micro silica: Evaluating durability and mechanical properties

The preliminary and inevitable interest in the use of partial replacements or by – products as complementary pozzolanic materials was mostly induced by enforcement of air pollution control resulted from cement production industry. Rise husk is by- product taken from rice mill process, with approximately the ratio of 200 kg per one ton of rice, even in high temperature it reduces to 40 kg. This paper presents benefits resulted from various ratios of rice husk ash(RHA) on concrete indicators through 5 mixture plans with proportions of 5, 10, 15, 20 and 25% RHA by weight of cement in addition to 10% micro- silica (MS) to be compared with a reference mixture with 100% Portland cement. Tests results indicated the positive relationship between 15% replacement of RHA with increase in compressive strengths by about 20%. The optimum level of strength and durability properties generally gain with addition up to 20%, beyond that is associated with slight decrease in strength parameters by about 4.5%. The same results obtained for water absorption ratios likely to be unfavourable. Chloride ions penetration increased with increase in cement replacement by about 25% relative to the initial values (about less than one fifth)

A Two-Stage Stochastic Model for Maintenance and Rehabilitation Planning of Pavements

Pavement maintenance and rehabilitation (M&R) plan for maintaining the pavement quality in an acceptable level has direct influence on the required budget. Deterministic budgeting is an unrealistic assumption, so, in this study, a two-stage stochastic model using integer programming is developed to address uncertainty in budgeting. Another aim of this study is to develop an executive model that considers a broad range of parameters at network level maintenance and rehabilitation planning. While having too many details in planning problems makes them more complicated, some restrictions called “technical constraints” were considered to reduce solution time of solving procedure as well as improve M&R activities assignment efficiency. Comparing results of the stochastic model with a deterministic model for a case study revealed that the two-stage stochastic model led to increased total cost compared to the deterministic one due to considering probability in budgeting. However, the developed model provides several M&R plans that are compatible with budget variation

Cost-effectiveness analysis of lung cancer screening with low-dose computed tomography in an Iranian high-risk population

Objective: The results of recent studies have shown that using low-dose computed tomography (LDCT) for screening of lung cancer (LC) improves cancer outcomes. The objective of the current study was to evaluate the cost-effectiveness of LDCT in an Iranian high-risk population. Methods: A Markov cohort simulation model with four health states was used to evaluate the cost-effectiveness of LDCT from a healthcare system perspective in the people aged 55–74 who smoked 25 or more cigarettes per day for 10–30 years. Cost data were collected, reviewing 324 medical records of patients with LC, and utilities and transition probabilities were extracted from the literature. The Monte Carlo simulation method was applied to run the model. Probabilistic sensitivity analysis and one-way analysis were also performed. Results: LC screening in comparison to a no-screening strategy was costly and effective. The incremental cost-effectiveness ratio of screening versus no-screening was IRR (Iranian rials) 98,515,014.04 which falls below the Iranian threshold of three times GDP (gross domestic product) per capita. One-way and probabilistic sensitivity analyses demonstrated that the results of the economic analysis were robust to variations in the key inputs for both. Conclusions: Using LDCT for screening of LC patients in a high-risk population is a cost-effective strategy.</p