Leaching Behaviour of Construction and Demolition Wastes and Recycled Aggregates: Statistical Analysis Applied to the Release of Contaminants

Construction and demolition wastes represent a primary source of new alternative materials which, if properly recovered, can be used to replace virgin raw materials partially or totally. The distrust of end-users in the use of recycled aggregates is mainly due to the environmental performance of these materials. In particular, the release of pollutants into the surrounding environment appears to be the aspect of greatest concern. This is because these materials are characterized by a strong heterogeneity which can sometimes lead to contaminant releases above the legal limits for recovery. In this context, an analysis of the leaching behaviour of both CDWs and RAs was conducted by applying a statistical analysis methodology. Subsequently, to evaluate the influence of the particle size and the volumetric reduction of the material on the release of contaminants, several experimental leaching tests were carried out according to the UNI EN 12457-2 and UNI EN 12457-4 standards. The results obtained show that chromium, mercury, and COD are the most critical parameters for both CDWs and RAs. Moreover, the material particle size generally affects the release of contaminants (i.e., finer particles showed higher releases), while the crushing process does not always involve higher releases than the sieving process.

Alternative Remediation for Raw Petroleum Sludge by Using Solidification/stabilization Method

In Malaysia, the current practise in treatment of petroleum sludge (PS) is by using incineration and the ash produce required further treatment for safely disposal into landfill. This process require high cost and treatment of raw sludge by using solidification/stabilization method was introduce. In this study, ordinary Portland cement was used as binder. This study focuses on physical properties (compressive strength, density test and water absorption) of S/S matrices and leaching behaviour (SPLP). Results shows adds up to of 30% PS gives results on strength which comply with minimum landfill dispose limit. Correlation between strength and density in regression coefficient of 80.99% and correlation between strength and water absorption shows strong regression of 93.12%. Leaching behaviours on 28 th day of curing showed the similar trend as on 7th day of curing. All heavy metals concentration in leaching test were below the USEPA standard except for Nickel and Chromium. Even though these two metals were exceeded the standard, Portland cement was capable to encapsulate Ni and Cr in mixture and reduce the concentration of 87% and 69% (PS 40%), respectively, compare to concentration in raw sludge. As, conclusion S/S method can be an alternative disposal method for raw sludge.

Use of Treated Non-Ferrous Metallurgical Slags as Supplementary Cementitious Materials in Cementitious Mixtures

This research investigated the possibility of using metallurgical slags from the copper and lead industries as partial replacement for cement. The studied slags were fayalitic, having a mainly ferro-silicate composition with minor contents of Al2O3 and CaO. The slags were treated at 1200–1300 °C (to reduce the heavy metal content) and then granulated in water to promote the formation of reactive phases. A full hydration study was carried out to assess the kinetics of reactions, the phases formed during hydration, the reactivity of the slags and their strength activity as supplementary cementitious material (SCM). The batch-leaching behaviour of cementitious mixtures incorporating treated slags was also investigated. The results showed that all three slags have satisfactory leaching behaviour and similar performance in terms of reactivity and contribution to the strength development. All slags were found to have mediocre reactivity and contribution to strength, especially at early ages. Nonetheless, they passed the minimum mechanical performance requirements and were found to qualify for use in cement.

A comparative analysis of heavy metals present in cigarette and cigarette leachate

Smoked cigarette and butts are the most common forms of litter globally. The local water bodies and their compartments have been severely polluted by the accumulation of these litters and the cumulative effect of many cigarette butts littered in a centralised area may present a significant threat to the living organisms. It is essential to study the leaching behaviour of cigarettes to understand how the heavy metals are leached out into the aquatic ecosystem. In this context, we determined the concentration of different metals (such as Cd, Cu, Fe, Pb, Sn, Zn & Hg) leached from the different brands of unsmoked and smoked cigarette and cigarette butts by using Atomic Absorption Spectrometry. The results revealed that the amounts of heavy metal are higher in butt samples (USB and SB) of both cigarette and leachate irrespective of brands, compared to the tobacco part of the cigarette and the concentrations of certain toxic heavy metals in cigarettes were significantly different between cigarette brands tested. These results suggest that cigarette litter was found to be one of the major sources of metal contamination in the aquatic ecosystem and apparent leaching may increase the risk of toxicity to aquatic organisms.