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Oil shale ash (OSA) as a binder has air, pozzolanic or latent hydraulic properties depending on the combustion temperature and type of ash collection equipment. This paper focuses on the use of OSA as the main binder for low strength concrete. Impact of hardening conditions on the strength development and soundness of various concrete mixes made with two main types of OSA and their mixes was tested. Crushed limestone was used as aggregate. Concrete mixes were designed at an OSA:aggregate ratio of 3:1 and 1:1, using fresh concretes with the same workability. The results revealed differences in the strength development, 28-day compressive strength and durability properties between hardened concretes made with various OSA binders. The compressive strength of concretes made with various OSA was tested in different curing conditions. The durability properties of OSA based hardened concrete such as water absorption and resistance were tested. The results of expansion and water resistance tests indicated that by increasing the content of CFB ash in OSA binders, water resistance was improved and expansion diminished.

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The focus of the current study is to characterise the leaching behaviour of polycyclic aromatic hydrocarbons (PAHs) from oil shale ashes (OSAs) of pulverised firing (PF) and circulating fluidised-bed (CFB) boilers from Estonian Thermal Power Plant (Estonia) as well as from mortars and concrete based on OSAs. The target substances were 16 PAHs from the EPA priority pollutant list. OSA samples and OSA-based mortars were tested for leaching, according to European standard EN 12457-2 (2002). European standard CEN/TC 15862(2012) for monolithic matter was used for OSA-based concrete. Water extracts were analysed by GC-MS for the concentration of PAHs. Naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene were detected. Still, the release of PAHs was below the threshold limit value for inert waste. The amount of the finest fraction (particle size <0.045 mm), the content of the Al-Si glass phase and the surface characteristics were the main factors, which could affect the accessibility of PAHs for leaching. The mobility of PAHs from OSA of CFB and PF boilers was 20.2 and 9.9%, respectively. Hardening of OSA-based materials did not lead to the immobilisation of soluble PAHs. Release of PAHs from the monolith samples did not exceed 0.5 μg/m(2). In terms of leaching of PAHs, OSA is safe to be used for construction purposes.

Abstract:In this paper, concrete with limestone coarse aggregate was studied due to frost action in saline and nonsaline environments. The main focus is to explain the damaging formula of concrete with poor quality of limestone aggregate in frost actions. All investigated concretes fulfill the recommendations of the European standard EN 206, Concrete-Specification, Performance, Production and Conformity limiting values for composition and properties of concrete (maximum W/C (water/cement) ratio, minimal class of compressive strength, minimal mass of cement and minimal percentage of entrained air). The damaging formula of the frost resistant concrete is studied through scaling test of concrete during freeze/thaw process, frost resistant test of coarse limestone aggregate and chemical analysis of limestone. Experiments results showed that there is a correlation between CaO/MgO ratio and Al 2 O 3 of limestone and frost resistance of concrete, using chemical composition for determining potential ACR (alkali-carbonate reactivity) will indicate higher risk of damaging effect of concrete.