Slope deposits in semiarid regions are known to be very sensitive environments, especially those that occurred during the minor fluctuations of the late Holocene. In this paper we analyse Holocene colluvium genesis, composition, and paleoenvironmental meaning through the study of slope deposits in NE Spain. Two cumulative slope stages are described during this period. In the study area, both slope accumulations are superimposed and this has enabled an excellent preservation of the aggregative sequence and the paleosols corresponding to stabilisation stages. 14C and TL dating, as well as archaeological remains, provide considerable chronological precision for this sequence. The origin of the accumulation of the lower unit is placed around 4295–4083 cal yr BP/2346–2134 cal yr BC (late Chalcolithic) and it developed until the Iron Age in a cooler and wetter climate (Cold Iron Age). Under favourable conditions, a soil A-horizon was formed on top of this unit. A new slope accumulation was formed during the Little Ice Age. Within the slope two morphogenetic periods ending with A-horizons are distinguished and related with two main cold–wet climatic events. The study of these slopes provides a great amount of data for the paleoenvironmental and geoarchaeological reconstruction of the late Holocene in NE Spain.

No abstract

This study analysed the fine particle (<5 mm) waste generated during siliceous or calcareous (depending on the composition of the original aggregate) concrete waste crushing. In the absence of industrial applications, such waste is amassed in open-air stockpiles on construction and demolition wastes (CDW) management plant grounds. The aim pursued was to find an outlet for that material in the cement industry. The starting waste, sourced from six Spanish management facilities, was characterised for its chemical and mineralogical composition, physical properties and pozzolanicity. The mineralogical phases in the CDW/lime system and their variations during the pozzolanic reaction were likewise identified. The findings showed that the fine waste consisted primarily in quartz, calcite, micas and feldspars, with smaller fractions of kaolinite and cement anhydrous phases. No portland cement hydration phases were identified. All six types analysed exhibited medium to low pozzolanicity, with the highest values recorded for the siliceous waste. Ettringite, C–S–H gels and calcium aluminate hydrates (C4AH13, C4AcH12) were identified during the pozzolanic reaction in CDW/lime system. Therefore, this type of waste can be reused as supplementary cementitious material with low-medium pozzolanic activity.

Abstract:The generation of enormous volumes of mine-tailing waste is standard practice in the mining industry. Large quantities of these tailings are also sources of kaolinite-rich materials that accumulate in slag heaps, causing significant environmental degradation and visual impacts on the landscape. The consequences of coal refuse dumped in slagheaps calls for the study of eco-innovative solutions and the assessment of waste types. Moreover, the environmental benefits of reusing large amounts of contaminated waste are also evident. Hence, the objective of this investigation is to expand current knowledge of new siliceous-aluminium minerals and their pozzolanic activity. Four raw tailing samples are characterized to determine their chemical (by ICP/MS analysis), morphological (by SEM/EDX analysis), and mineralogical (by XRD analysis) compositions prior to their thermal activation that transforms the inert wastes at various temperatures into materials with cementitious properties. The results of XRD analysis following activation confirmed that the kaolinite content is fully transformed into metakaolinite. The coal refuse samples presented sufficiently reliable levels of pozzolanic activity for use as additives in industrial cements.

No abstract