OPTIMIZATION OF AGGREGATE TESTING USING POLYNOMIAL REGRESSION

Recycled Aggregate(RA)has only been used as sub-grade applications,roadwork and unbound materials because it is believed that RA has lower strength and poorer quality than normal aggregate.This paper assesses RA quality by propos-ing a new testing procedure.The new procedure is developed by using correlation information among the standard twenty three tests commonly employed in the construction industry.Samples of RA from ten demolition sites were ob-tained with service life ranging from ten to forty years.One additional set of samples was specifically collected from the Tuen Mun Area 38 Recycling Plant,Hong Kong for testing.The characteristics of these eleven sets of samples were then compared with normal aggregate samples.A Vandermonde matrix for interpolation polynomials coefficient estimation is employed to yield detailed mathematical relationships between results of two particular tests,from that redundant tests can be identified.Different orders of interpolation polynomials are used for comparison,hence the best-fit equations with lowestfitting errors from different orders of polynomials can be found.This paper shows that four out of twenty three tests are required in the new testing procedure.

THE EFFECTIVENESS OF ELECTRICAL AND ELECTRONIC WASTE RECYCLING AND ITS IMPLICATIONS TO GREEN BUILDING:Empirical Studies in India and Switzerland

The life of consumer electrical and electronic(E&E)devices is relatively short,and decreasing as a result of rapid changes in equipment features and capabilities.This creates a large waste stream of obsolete E&E equipment.Even though there are conventional disposal methods for E&E waste,these methods have disadvantages from both economic and environmental viewpoints.This paper examines the existing recycling situations and collection methods of E&E waste in India and Switzerland.Questionnaire survey,interview discussions and case studies are conducted.Their E&E waste scenario and technologies applied for E&E waste are investigated.It is found that India performs better in E&E intensity per service unit and employment potentials,while Switzerland performs better in occupational hazards and emissions of toxics.Recommendations to improve the existing E&E waste recycling situations and its implications to green building are also given.

PREDICTING ENVIRONMENTAL PERFORMANCE OF CONSTRUCTION PROJECTS BY USING LEAST-SQUARES FITTING METHOD AND ROBUST METHOD

Recently,an Environmental Management System(EMS)has been used to promote effective environmental protection.Environmental Performance Assessment(EPA)is a critical tool of the EMS in checking,reviewing,monitoring and evaluating environmental performance of organizations.To implement EPA,the relations between Environmental Operational Indicators(EOIs)used in EPA and Environmental Performance Indicators(EPIs)are required,which,however,are lacking in the construction industry.This paper attempts to develop a series of EOIs and EPIs of individual construction projects for EPA and to measure their relations by using least-squares fitting and robust fitting methods.The results show that the defined EOIs correlate strongly with EPIs.Therefore,EPA can be used to identify areas for continuous improvement,and also can provide an early indication of the environmental performance for an organization.

Behaviors of recycled aggregate concrete-filled steel tubular columns under eccentric loadings

The paper investigates the behaviors of recycled aggregate concrete-filled steel tubular(RACFST)columns under eccentric loadings with the incorporation of expansive agents.A total of 16 RACFST columns were tested in this study.The main parameters varied in this study are recycled coarse aggregate replacement percentages(0%,30%,50%,70%,and 100%),expansive agent dosages(0%,8%,and 15%)and an eccentric distance of compressive load from the center of the column(0 and 40 mm).Experimental results showed that the ultimate stresses of RACFST columns decreased with increasing recycled coarse aggregate replacement percentages but appropriate expansive agent dosages can reduce the decrement;the incorporation of expansive agent decreased the ultimate stresses of RACFST columns but an appropriate dosage can increase the deformation ability.The recycled coarse aggregate replacement percentages have limited influence on the ultimate stresses of the RACFST columns and has more effect than that of the normal aggregate concretesteel tubular columns.

Effect of fly ash and slag on concrete:Properties and emission analyses

Recycled concrete is a material with the potential to create a sustainable construction industry.However,recycled concrete presents heterogeneous properties,thereby reducing its applications for some structural purposes and enhancing its application in pavements.This paper provides an insight into a solution in the deformation control for recycled concrete by adding supplementary cementitious materials fly ash and blast furnace slag.Results of this study indicated that the 50%fly ash replacement of Portland cement increased the rupture modulus of the recycled concrete.Conversely,a mixture with over 50%cement replacement by either fly ash or slag or a combination of both exhibited detrimental effect on the compressive strength,rupture modulus,and drying shrinkage.The combined analysis of environmental impacts and mechanical properties of recycled concrete demonstrated the possibility of optimizing the selection of recycled concrete because the best scenario in this study was obtained with the concrete mixture M8(50%of fly ash+100%recycled coarse aggregate).