Use of Nanomaterials in the Stabilization of Expansive Soils into a Road Real-Scale Application

Stabilization is a traditional strategy used to improve soils with the main objective of ensuring that this base is compliant with the technical specifications required for the subsequent development of different infrastructures. This study proposes the use of commercial nanomaterials, based on a solution of silicates, to improve the technical characteristics and bearing capacity of the expansive soil. A physical–chemical property study was carried out on the additive nanomaterial. Subsequently, different mixtures of expansive soil, selected soil and artificial gravel with quicklime and commercial nanomaterials were developed to evaluate the improvement obtained by the use of nanomaterials in the technical characteristics of the soil. Compressive strength and the Californian Bearing Ratio index were considerably increased. A full-scale study was carried out in which the nanomaterial product was applied to two different sections of stabilized road compared to a control section. The results obtained showed that the use of nanomaterial led to the possibility of reducing the control section by 30 cm, thus achieving less use of quicklime and a mechanical means for preparing the road section. The use of commercial nanomaterial improved the behavior of the stabilized sub-base layer. Through life cycle assessment, this study has shown that the use of nanomaterials reduces the environmental impact associated with soil stabilization.FEDER/Ministerio de Ciencia, Innovacion y Universidades-Agencia Estatal de Investigacion/Ecaryse RCT-2017-6202-

Life Cycle Assessment of natural and recycled masonry mortars

1. Introduction \u2013 The life cycle assessment (LCA) is a methodological tool to measure the environmental impact of a product, process or system throughout its life cycle. It is based on the collection and evaluation of the inputs, outputs and the potential of a system of product to produce environmental impacts through their life cycle [1,2]. LCA has already been applied to the environmental impact assessment of construction and demolition waste (C&DW), both in the production of recycled aggregate [3] and the application of these aggregates in the manufacture of concrete [4,5] or for the formation of base and sub-base of roads [6]. Simion et al. [3] concluded that the production of recycled aggregates generates less environmental impact than natural aggregate processing, with up to 7 times less global warming potential. Knoeri et al. [4] found in their study that the environmental impact of recycled concrete reduced up to 70% compared to conventional concrete. Similar results have been obtained by Mroueh et al. [6], since the use of crushed concrete decreased environmental loads of road construction. This research aims to quantify and assess the environmental impact associated with the manufacture of masonry mortar made of different replacement of fine natural aggregate (FNA) by fine recycled aggregate (FRA). These mortars have been previously characterized [7] according to the specifications of the reference standard for masonry mortar EN 998-2 [8]. 2. Methods \u2013 According to ISO 14040-14044 [1,2], the LCA application is based on four stages: defining the goal and scope, analyzing the inventory, assessing the impact and interpreting the results. The goal of this study is to determine the environmental impact associated with the production of masonry mortars made with different replacement of FNA by RFA. This goal determines the system boundaries: the LCA includes production and transport of aggregates, cement, filler and plasticizer, and manufacture of dry mortar in mortar plant. The considered functional unit is 1 ton of dry mortar. Inventory analysis involves data collection and calculation procedures to quantify relevant inputs and outputs for each unit process of the product system. As data source were used direct measures, Environmental Product Declaration and Ecoinvent database. Environmental impact was assessed through SimaPro software tool and Impact 2002+ was the methodology applied for impact assessment. This method relates all types of life cycle inventory results via fourteen midpoint impact categories (human toxicity, respiratory effects, ionizing radiation, ozone layer depletion, photochemical oxidation, aquatic ecotoxicity, terrestrial ecotoxicity, terrestrial acidification/nitrification, aquatic acidification, aquatic eutrophication, land occupation, global warming, non-renewable energy, mineral extraction) to four damage categories (human health, ecosystem quality, climate change and resources). 3. Results and Discussion \u2013 Taking into account the production of the aggregates, the results show that the impacts generated by the production of FNA are important in terms of human health, ecosystem quality, climate change and resources. FRA production generates negative values on impact categories such as human health, ecosystem quality and resources, and positive values on climate change but it is about 34% of the impacts generated by the production of FNA. These negatives values mean environmental benefits due to the avoided loads of the recovered materials, as the avoided impact by C&DW recycling is higher than the generated impact by the processing of FNA. On the other hand, the cement production is for both natural and recycled mortar the largest contributor to all impact categories. According to others authors [5] this is due to the high CO2 emission during the calcination process in the clinker production. The 25% replacement of FNA by FRA in masonry mortar causes benefits for most of the impact categories, specially the value of land occupation is reduced 38% respect to natural mortar. 4. Conclusions \u2013 In this study, a LCA approach was used in order to quantify the environmental impacts of manufactured masonry mortars with FNA and FRA. The comparison between evaluated mortars shows that total impacts of recycled mortar are lower than total impacts of natural mortar because of avoided landfilling of C&DW. Therefore, the use of FRA involves not only environmental benefits increasing recycling rates that reduce the volume of waste disposed in landfills, but it can generate economic benefits seeking new applications that expand the recycling market of these materials. References [1] EN ISO 14040. Environmental management. Life cycle assessment. Principles and framework. European Committee for Standardization. Brussels, Belgium. [2] EN ISO 14044. Environmental management. Life cycle assessment. Requirements and guidelines. European Committee for Standardization. Brussels, Belgium. [3] Simion I, Fortuna M, Bonoli A, Gavrilescu M. Comparing environmental impacts of natural inert and recycled construction and demolition waste processing using LCA. Journal of Environmental Engineering and Landscape Management, 2013; 21:4, 273-287. [4] Knoeri C, Sany\ue9-Mengual E, Althaus H. Comparative LCA of recycled and conventional concrete for structural applications. Int J Life Cycle Assess, 2013; 18:909\u2013918 [5] Marinkovi\u107 S, Radonjanin V, Male\u161ev M, Ignjatovi\u107 I. Comparative environmental assessment of natural and recycled aggregate concrete. Waste Management 2010; 30(11), pp. 2255-2264. [6] Mroueh U, Eskola P, Laine-Ylijoki J. Life-cycle impacts of the use of industrial by-products in road and earth construction. Waste Management 2001;21: 271-277. [7] Cuenca-Moyano GM, Mart\uedn-Morales M, Valverde-Palacios I, Valverde-Espinosa I, Zamorano M. Influence of pre-soaked recycled fine aggregate on the properties of masonry mortar. Construction and Building Materials 2014; 70:71-79. [8] EN 998-2. Specification for mortar for masonry. Part 2: Masonry mortar. European Committee for Standardization. Brussels, Belgium

Environmental assessment, mechanical behavior and new leaching impact proposal of mixed recycled aggregates to be used in road construction

Several types of mixed recycled aggregates (MRA) from construction and demolition waste (C&DW) treatment plants in Córdoba and Malaga, Spain, and a sample of natural aggregate (NA) were studied to evaluate the viability of their use in the construction of road layers. The physicochemical properties, mechanical behavior and environmental impact of all samples were determined. The life cycle analysis of road sections manufactured with the materials studied was also determined. All samples of MRA showed a mechanical behavior suitable for use in the formation of road layers. In addition, it was determined that these materials, when they come from C&DW with selective collection at origin, cause less environmental impact than the impact caused by the use of natural aggregates in the formation of road layers. © 2020 Elsevier Lt