Mixture Optimization of Concrete Paving Blocks Containing Waste Silt

open3noMost of the waste materials recycled for the production of new construction materials are by-products of various manufacturing processes, such as the aggregate washing process. Recycling such materials is of paramount importance since it could reduce the adverse environmental impacts resulting from landfilling. Various studies have attempted to recycle different types of waste materials and by-products into concrete paving blocks. However, the availability of literature on concrete paving blocks containing waste silt is quite scarce. Thus, the current paper focuses on mix design optimization and production of concrete paving blocks containing high amounts of waste silt resulting from the aggregate production process. Using the mixture Design of Experiments (DOE), 12 sets of concrete paving blocks with different aggregate blends were produced to optimize the mix design. Once the final mix design was achieved, the physical and mechanical properties of the concrete paving blocks were investigated following the EN 1338 standard. Shape and dimension measurements and various tests, including water absorption, tensile splitting strength, abrasion resistance, and slip/skid resistance were conducted on the experimental concrete paving samples. Overall, the produced concrete paving blocks showed promising properties for future applications in pedestrian walking paths.This paper was written for the SAFERUP! Project, which received funding from the European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant agreement No. 765057.openSolouki, Abbas; Tataranni, Piergiorgio; Sangiorgi, CesareSolouki, Abbas; Tataranni, Piergiorgio; Sangiorgi, Cesar

Waste Silt as Filler in Hot Mix Asphalt: A Laboratory Characterization

Several studies aimed to improve both the performance and environmental impact of asphalt pavements using waste and recycled materials as fillers. This study focused on the effect of untreated and thermally treated silt as a filler in hot mix asphalt (HMA). The silt used in the study was a byproduct from a local aggregate production plant in Bologna, Italy. Mineral and chemical analyses revealed that the waste silt required thermal treatment at 750 C for 2 h. The study compared the use of calcined silt, untreated silt, and a common limestone filler in the production of asphalt mastics and HMA specimens. The rheological properties of the mastics were analyzed using frequency sweep and multiple stress creep recovery tests. The physical and mechanical characteristics of the HMAs were evaluated through the air voids content, Marshall stability and indirect tensile strength tests. Additionally, the water susceptibility and thermal sensitivity of the HMAs were evaluated through the indirect tensile strength ratio and indirect tensile stiffness modulus at different testing temperatures. The results showed that the addition of calcined silt had no significant effect on the rheological properties of the mastic or the optimal binder content. However, the samples produced with thermally treated silt showed the highest stiffness and resistance to rutting compared with the other samples. On the other hand, the addition of untreated silt slightly decreased the stiffness value of the samples. In conclusion, the use of waste silt as a filler has potential as a sustainable and eco-friendly solution for HMAs

Preliminary Evaluation of Cement Mortars Containing Waste Silt Optimized with the Design of Experiments Method

Every year, up to 3 billion tons of non-renewable natural aggregates are demanded by the construction sector and approximately 623 million tons of waste (mining and quarrying) was produced in 2018. Global efforts have been made to reduce the number of virgin aggregates used for construction and infrastructure sectors. According to the revised waste framework directive in Europe, recycling at least 70% of construction and demolition waste materials by 2020 was obligatory for all member states. Nonetheless, quarries must work at full capacity to keep up with the demands, which has made quarry/mining waste management an important aspect during the past decades. Amongst the various recycling methods, quarry waste can be included in cement mortar mixtures. Thus, the current research focuses on producing cement mortars by partially substituting natural sand with the waste silt obtained from the limestone aggregate production in S.A.P.A.B.A. s.r.l. (Italy). A Design of Experiments (DOE) method is proposed to define the optimum mix design, aiming to include waste silt in cement mortar mixtures without affecting the final performance. Three cement mortar beams were produced and tested for each of the 49 randomized mixtures defined by the DOE method. The obtained results validate the design approach and suggest the possibility of substituting up to 20% of natural sand with waste silt in cement mortar mixtures

An overview of the emerging warm mix asphalt technology

The asphalt industry is constantly attempting to reduce its emissions as concerns are growing on global warming. This is done by decreasing the mixing and compaction temperatures of asphalt mixtures without affecting the properties of the mix which is possible through numerous available technologies in the industry. The production of asphalt mix is done by warm mix asphalt (WMA) technology at considerably lower temperatures (120°C or lower). Less energy consumption, lower mixing and compaction temperatures, early site opening, reduced ageing, fewer emissions, cool weather paving, better workability and, finally, an extended paving window could be mentioned as some of the benefits obtained by using the WMA. This paper presents the WMA techniques and technologies such as foaming techniques, wax and chemical additives techniques. Additionally, the performance of WMA popular technologies such as Sasobit®, WAM®-Foam, Evotherm®, Low energy asphalt, Rediset® WMX and REVIX™ are fully described

Colorectal liver metastases: Surgery versus thermal ablation (COLLISION) - a phase III single-blind prospective randomized controlled trial

Background: Radiofrequency ablation (RFA) and microwave ablation (MWA) are widely accepted techniques to eliminate small unresectable colorectal liver metastases (CRLM). Although previous studies labelled thermal ablation inferior to surgical resection, the apparent selection bias when comparing patients with unresectable disease to surgical candidates, the superior safety profile, and the competitive overall survival results for the more recent reports mandate the setup of a randomized controlled trial. The objective of the COLLISION trial is to prove non-inferiority of thermal ablation compared to hepatic resection in patients with at least one resectable and ablatable CRLM and no extrahepatic disease. Methods: In this two-arm, single-blind multi-center phase-III clinical trial, six hundred and eighteen patients with at least one CRLM (≤3cm) will be included to undergo either surgical resection or thermal ablation of appointed target lesion(s) (≤3cm). Primary endpoint is OS (overall survival, intention-to-treat analysis). Main secondary endpoints are overall disease-free survival (DFS), time to progression (TTP), time to local progression (TTLP), primary and assisted technique efficacy (PTE, ATE), procedural morbidity and mortality, length of hospital stay, assessment of pain and quality of life (QoL), cost-effectiveness ratio (ICER) and quality-adjusted life years (QALY). Discussion: If thermal ablation proves to be non-inferior in treating lesions ≤3cm, a switch in treatment-method may lead to a reduction of the post-procedural morbidity and mortality, length of hospital stay and incremental costs without compromising oncological outcome for patients with CRLM. Trial registration:NCT03088150 , January 11th 2017

Effect of blending process on rheological and volumetric properties of asphalt binder

The improvement of asphalt binder physical properties is possible through the addition of polymers. However, due to different physical and chemical properties of additives, each modifier requires its unique blending processing conditions. Despite these facts, not much attention has been paid to the effects of blending process on the rheological properties of asphalt binders. Therefore, it was hypothesized that different blending parameters could affect the rheological properties of asphalt binders, which in turns influence the overall performance of polymer modified blends and mixtures. As a result, three different objectives were set for the current study which were 1) to establish a blending matrix for asphalt binder modification, 2) to determine the effect of blending process on the rheological properties of asphalt binders, and 3) to determine the effect of blending process on the volumetric properties of asphalt mixtures. The blending matrix was established by selecting different parameters which potentially affected the blending outcome and the modified binders were prepared according to the established matrix. Different binder tests including softening point temperature, rotational viscosity, and dynamic shear rheometer (DSR) tests were conducted on EVA and Sasobit modified binders. Finally, the optimum asphalt content of mixtures was obtained for samples prepared at three different motor speed values of 400, 1200, and 1800 using the two mentioned polymers. The results indicated high binder stiffness for binders processed at higher blending speeds compared to binders blended at lower speeds. This was observable through higher softening point temperatures, higher viscosity values,and higher complex modulus measurements. Therefore, an increase in motor speed values increased the overall stiffness of the modified binders. Additionally,the stiffness of asphalt binders also increased with an increase in additive content. Likewise, the optimum asphalt binder content increased for mixtures containing stiffer binders. It was concluded that an increase in motor speed preaged the binder sample during the preparation process which led to its increased stiffness. It has to be mentioned that the pre-aging phenomena is undesirable since it will reduce the overall service life of pavements. The application of lower motor speed during blending is highly suggested

Thermally Treated Waste Silt as Geopolymer Grouting Material and Filler for Semiflexible Pavements

Considering the future shortage of natural aggregates, various researchers have promoted the recycling of by-products into various asphalt pavement types. This paper promoted a doublerecycling technique, where thermally treated waste silt was used as a filler for the bituminous skeleton and grouting material of a geopolymer-based semiflexible pavement. Semiflexible pavements (SFP) inherit the flexibility of common asphalt pavements and simultaneously benefit from the rigidity of cement concrete pavements. For this purpose, waste silt obtained from a local asphalt plant was thermally treated at 750 C and was used as the filler to produce the porous skeleton. Two different materials, including conventional cement-based and a geopolymer-based cement, were used as the grouting material. The geopolymer grout was produced by mixing metakaolin (MK), potassiumbased liquid hardener and calcined silt as filler. The porous and grouted samples were characterized in terms of indirect tensile strength (ITS), the indirect tensile strength modulus (ITSM) and moisture sensitivity. The use of thermally treated waste silt as filler in porous asphalt demonstrated promising results and was comparable to the control samples produced with limestone as the filler. However, the control samples grouted with cement-based material outperformed the geopolymer grout in all aspects. Moreover, the addition of calcined silt improved the low-temperature fatigue performance of porous and grouted asphalt pavements

Waste Mineral Filler Recycling in New Pavement Solutions

Società Azionaria Prodotti Asfaltico Bituminosi Affini (S.A.P.A.B.A. s.r.l.) is an asphalt/aggregate production plant located in Bologna, Italy. The resulting dirt and mud from the washing process is stored at specific sedimentation lakes close to the plant and are referred to as waste silt. The initiative and motivation of the current research follows the 12th objective of the sustainable development goals proposed by the United Nations. As a result, the overall aim of the current study was to reduce the impact of waste mineral fillers through recycling in new paving solutions. Considering three paving types of cement-bound, geopolymer-bound and asphalt pavements the following objectives were set: 1) To investigate the possibility of recycling waste silt in cement-bound paving solution; 2) To explore the feasibility of producing geopolymer-bound paving solutions containing waste silt; 3) To study the potential of using waste silt as fillers in different asphalt pavements. The first objective was achieved by utilizing waste silt into cement-bound materials. For this purpose, the by-product was introduced to cement mortars and was partially replaced (20%) with the natural sand. Moreover, statistical models were used to produce concrete paving blocks. The second objective was pursued by studying the feasibility of using the waste silt as a filler in geopolymer cement products. Following a comprehensive review, the silt was thermally calcined and used as filler in geopolymer cement and paving blocks. The third objective was achieved by evaluating the rheological and mechanical performance of hot mix, porous and semi-flexible asphalt containing waste silt. The limestone filler of a hot mix asphalt was replaced with thermally and untreated waste silt. To sum up, different paving blocks and asphalt pavements mixtures containing waste silt were proposed that presented acceptable performance when compared to different national and European standards

Thermally Treated Waste Silt as Geopolymer Grouting Material and Filler for Semiflexible Pavements

Considering the future shortage of natural aggregates, various researchers have promoted the recycling of by-products into various asphalt pavement types. This paper promoted a double-recycling technique, where thermally treated waste silt was used as a filler for the bituminous skeleton and grouting material of a geopolymer-based semiflexible pavement. Semiflexible pavements (SFP) inherit the flexibility of common asphalt pavements and simultaneously benefit from the rigidity of cement concrete pavements. For this purpose, waste silt obtained from a local asphalt plant was thermally treated at 750 °C and was used as the filler to produce the porous skeleton. Two different materials, including conventional cement-based and a geopolymer-based cement, were used as the grouting material. The geopolymer grout was produced by mixing metakaolin (MK), potassium-based liquid hardener and calcined silt as filler. The porous and grouted samples were characterized in terms of indirect tensile strength (ITS), the indirect tensile strength modulus (ITSM) and moisture sensitivity. The use of thermally treated waste silt as filler in porous asphalt demonstrated promising results and was comparable to the control samples produced with limestone as the filler. However, the control samples grouted with cement-based material outperformed the geopolymer grout in all aspects. Moreover, the addition of calcined silt improved the low-temperature fatigue performance of porous and grouted asphalt pavements

Quarry Waste as Precursors in Geopolymers for Civil Engineering Applications: A Decade in Review

Carbon footprint reduction of paving materials could be explored through recycling mining by-products into different applications, which will preserve natural resources and decrease environmental issues. One possible approach is to reuse quarry dust and mining ore waste as precursors in geopolymer applications. geopolymers are mineral polymers rich in aluminosilicates with an amorphous to a semi-crystalline three-dimensional structure. The current review aims to summarize the studies conducted during the past decade on geopolymers containing quarry dust and mine tailings. The first section discusses various precursors used for geopolymer cement production such as metakaolin, ground granulated blast furnace slag (GGBFS), fly ash, and quarry/mining ore wastes including silt, tungsten, vanadium, copper, gold, zinc, marble, iron, basalt, and lithium. Different calcination treatments and curing conditions have been summarized. In some cases, the precursors are required to be calcined to increase their reactivity. Both ambient temperature and elevated temperature curing conditions have been summarized. Less attention has been paid to room temperature curing, which is necessary for field and industrial implementations. Engineering properties such as compressive strength, density, durability and acid resistance, water absorption and abrasion of geopolymers containing mining waste were reviewed. One of the main barriers preventing the widespread use of waste powders, in addition to economic aspects, in geopolymers could be due to their unstable chemical structure. This was shown through extensive leachate of Na+ or K+ cations in geopolymer structures. The review of over 100 articles indicated the need for further research on different aspects of quarry waste geopolymer productions before its full industrial implementation