Recycled powder as filler admixture in cementitious systems : production and characterization

In concrete production, aggregate represents almost 75% of the materials used. The exploitation of natural sources for this purpose also causes an environmental impact, while deposition of wastes from construction industry pollutes soil and water. The feasibility of recycled coarse aggregate used as component of concrete has been amply proved. Fine recycled aggregate is a by-product derived from the processing of recycled coarse aggregate, but there are some technological difficulties for its use in concrete, because of the high water absorption and powder content. The aim of this study is to propose and analyse the alternative use of milled recycled fine aggregate as mineral admixture. For this purpose, dry recycled fine aggregate was processed in a laboratory ball mill for cement, with the aid of cylpebs. Grinding was carried out for 2:00, 2:45 and 3:30 hours, and the sampling of ground recycled fine aggregate (GRFA) was done after each period. For the three grindings periods, the characterization of GFRA was performed for assessing its suitability as mineral filler. Tests included determinations of contents of material < 45 μm and < 75 μm by wet sieving, density, particle size distribution by laser diffraction, chemical composition and Blaine specific surface. Additionally, water demand for standard consistency paste with ordinary Portland cement (OPC) was prepared as reference, and also determined for pastes with replacement of 15% and 30% of cement by GRFA for each grinding period. Also, setting times and strength were measured. Results showed limited filler effect from GRFA when incorporated in cementitious materials, with the consideration of the grinding period as an important factor. Thus, further feasibility studies are necessary in order to investigate different potential applications of this ground material

Improving the quality of various types of recycled aggregates by biodesposition

Demand for construction materials has been rising in recent decades in many countries around the world, placing a heavy burden on the environment in terms of both the natural resources consumed and the enormous flow of waste generated. In order to obtain a more sustainable construction, it is often suggested to reintroduce the industry’s own waste as input for the manufacture of new materials. In this study, the use of construction and demolition waste of concrete or mixed concrete/ceramic nature is investigated as a replacement of natural aggregates in concrete. The greater affinity of recycled aggregates for water directly affects the workability and/or the concrete strength and durability. One possible solution to reduce the aggregates water absorption is to apply a biogenic treatment with calcium carbonate-precipitating bacteria that consolidate the aggregate surface or the adhering mortar. Experimental results show that the biodeposition treatment reduced the recycled aggregate water absorption by generating precipitation in the pores and an impermeable outer layer, most effectively on the roughest particle surfaces. The largest decrease happened in the aggregates with the highest porosity. The biogenic layer had a good cohesion with the aggregates. The results of sonication indicated that the most effective treatment was on recycled concrete aggregates (RCA) instead of mixed aggregates (MA). Therefore, the treated RCA was used to make concrete for further investigation. The concrete made with bio-treated RCA had a denser structure, a decreased water absorption (around 1%) and an improved compressive strength (25%)

Carbonation of concrete with construction and demolition waste based recycled aggregates and cement with recycled content

Durability is a major concern in concrete (particularly recycled concrete) structures exposed to carbonation-induced corrosion, given the social, economic, environmental and safety implications involved. This article explores carbonation performance in concrete with 25% or 50% mixed recycled construction and demolition waste aggregate, alone or in conjunction with cement containing 25% fired clay construction and demolition waste. Irrespective of cement type, the mean carbonation depth was slightly greater in materials with 25% or 50% recycled aggregate than in concretes with 100% natural aggregate, although the difference was not statistically significant for the 25% replacement ratio. In all the concretes studied, the carbonation coefficient was below the 4 mm/yr0.5 indicative of good quality. Based on the prediction model proposed in Spain’s concrete code, reinforcement passivity was guaranteed in all these types of concrete when exposed to class XC1 to XC4 carbonation environments for substantially longer than their 100 year design service life.This study was funded under research projects BIA 2013-48876-C3-1-R, BIA2013-48876-C3-2-R and BIA2016-76643-C3-1-R awarded by the Ministry of Science and Innovation and grant GR 18122 awarded to the MATERIA Research Group by the Regional Government of Extremadura and the European Regional Development Fund, ERDF. In 2016 University of Extremadura teaching and research personnel benefitted from a mobility grant (MOV15A029) awarded by the Regional Government of Extremadura and in 2018 from a José Castillejo (CAS17/00313) scholarship granted by the Spanish Ministry of Education, Culture and Sport. Philip Van den Heede is since October 2017 a postdoctoral fellow of the Research Foundation—Flanders (FWO) (project number 3E013917) and acknowledges its support.Peer reviewe

Concrete manufacture with un-graded recycled aggregates

Purpose – The purpose of this paper is to investigate whether concrete that includes un-graded recycled aggregates can be manufactured to a comparable strength to concrete manufactured from virgin aggregates. Design/methodology/approach – A paired comparison test was used to evaluate the difference between concrete made with virgin aggregates (plain control) and concrete including recycled waste. Un-graded construction demolition waste and un-graded ground glass were used as aggregate replacements. With regard to concrete, compressive strength is widely used as a measure of suitability as being fit for purpose. Therefore compressive strength was mainly used to compare the different concrete batches; however density was measured across the range of samples. Findings – The findings show that a lower average compressive strength is achieved when compared to the plain control sample manufactured with virgin aggregates. Correct particle packing may not be achieved and grading of aggregates is essential prior to mix design. The recycled aggregate was highly variable in terms of the fine particle content, which affected the water demand of the concrete. Practical implications – This manufacturing practice is considered necessary because of the current trend in using waste products in concrete to replace binders and aggregates; thus reducing the impact on the environment and use of finite natural resources. The research shows the risk of mixing concrete using a simple aggregate replacement without careful aggregate grading and adjustments to the mix design. Originality/value – The paper examines 100 per cent ungraded aggregate replacement with glass and demolition waste

Multi-criteria decision analysis to assess the environmental and economic performance of using recycled gypsum cement and recycled aggregate to produce concrete: the case of Catalonia (Spain)

The production of virgin raw materials used in construction and the generation of construction and demolition waste (CDW) are key environmental issues in the construction industry. Portland cement and concrete are used extensively in the construction sector. Processing of CDW to produce recycled gypsum cement and recycled aggregates (RA) and their use in the production of structural and non-structural concrete are one way of slowing natural resource depletion and reducing the amount of CDW landfilled. This study proposes the application of multi-criteria decision analysis (MCDA) to compare the production of “green” concretes made from recycled gypsum cement (RGC) and RA with the production of conventional concrete made from natural aggregate and ordinary Portland cement. The VIKOR MCDA method was employed to determine the best or a set of good alternative(s) for concrete production, considering environmental and economic criteria. The life cycle assessment method was used to select the environmental evaluation criteria, and the reference cost of producing concrete alternatives in Spain was used to determine economic criteria. The results of this study, in which environmental and economic criteria were considered of equal weight, or one of the two criteria was given greater weight, showed that the best option for structural and non-structural concrete was the use of RGC and RA. In both cases, the worst alternative was conventional concrete. In conclusion, we found that the use of RGC and RA in concrete production is positive because it replaces the original raw material, reduces the environmental impact, and lowers the economic costs.Postprint (published version

Construction waste in hot mix asphalt

Este 16.º encontro tivo lugar en Lisboa do 25 ao 28 de maio de 2010.[Abstract:] This paper analyzes the effect of water on the durability of hot asphalt mixtures made with recycled aggregates from construction and demolition waste. To design the asphalt mixtures Marshall tests were carried out. Indirect Tensile tests were carried out to evaluate stripping behavior. The mixtures tested were fabricated with 0%, 20%, 40% and 60% recycled aggregates. The hot asphalt mixture specimens made with different percentages of recycled aggregates from construction and demolition waste and of natural quarry aggregates showed poor stripping behaviour. This poor stripping behaviour has a negative effect on the durability of hot asphalt mixtures containing this type of recycled aggregate

Thermal Conductivity of Crumb Rubber as Partial Sand Replacement and Recycled Aggregates as Partial Coarse Aggregate Replacement in Concrete

Disposal of waste tire rubber has become a major environmental issue worldwide and is increasing day by day, especially in Malaysia where carbon emission is among the highest in the world. Therefore, recycled waste materials are being used as construction materials in order to create new innovative products that are able to mitigate environmental pollution, reduce the cost of construction and improve the properties of concrete. This study discusses the utilisation of crumb rubber and recycled aggregates in concrete construction and the objective of this study is to determine the thermal conductivity of crumb rubber and compare the optimum strength of concrete materials. 12 cube samples measuring 200 200 100 mm containing different percentages of crumb rubber (0, 1, 2, 3, 4, and 5%) as fine aggregate substitute and 50% of recycled aggregates as coarse aggregate substitute were produced. The concrete grade used for these specimens is grade 35. The curing process was conducted on the samples to achieve the standard strength of concrete in 7 and 28 days. Therefore, the real strength of concrete was measured after the curing process. A slump test was conducted to determine the properties of crumb rubber. In addition, the samples were examined using the guarded hot box method to obtain the optimum percentage of crumb rubber as partial sand replacement in concrete for thermal conductivity. The results show that thermal conductivity (k-value) decreased slightly with the increase in crumb rubber content. However, the quality of concrete also slightly increased as the percentage of crumb rubber content increased. Lastly, based on the results, 5% of crumb rubber and 50% of recycled aggregates were suggested as the optimum percentages to be used in concrete as it achieved the lowest thermal conductivity compared to conventional concrete

Performance of Aggregate Subgrade Layers in Low Volume Roads Constructed with Unconventional Recycled Aggregates

With transportation sector accounting for approximately 27% of total greenhouse gas emissions, transportation agencies all over United States have made sincere efforts to reduce such carbon footprint by incorporating more recycled materials in design mixes. In Illinois, recycled materials commonly include large sized unconventional aggregates used to stabilize weak subgrade soils that are abundantly found in wet of optimum conditions and prone to frost effects. To facilitate increased use of such “aggregate subgrade” materials, IDOT has recently introduced new gradation bands. However, performance of such recycled aggregate subgrade materials within the bounds of current design framework is largely unknown. To this end, a full scale accelerated pavement test study was undertaken to study six different aggregate subgrade materials involving construction of twelve full scale flexible pavement sections over weak engineered subgrade. Results of accelerated pavement testing on six test sections and performance of three different aggregate subgrade materials are highlighted in this paper including data from quality control tests such as nuclear density gauge, GeoGauge for composite layer modulus, and lightweight and falling weight deflectometers. Current pavement design framework was adequate when designing with two out of three aggregate subgrade materials that constituted different proportions of recycled materials. One noteworthy finding was that as-constructed hot mix asphalt thickness variation was found to be quite large due to reclaimed asphalt pavement subbase sinkage observed during paving operations

Recycling aggregate from concrete, properties and possibility for using in ready Mix Concrete

Many requests for different types of concrete, in general are depends of the aggregates. One of the aim of this paper is to analyses the possibilities of using the recycling aggregate, from part of existing concrete such a raw materials and during the technological process for production of aggregate. Recycling of concrete is a relatively simple process. It involves breaking, removing, and crushing existing concrete into a material with a specified size and quality. In this paper the main target is to compare the properties of fresh concrete and the hardening concrete for the mix design with crashed aggregate and recycling aggregate from parts of concrete after the demolition process.Nowadays large amount of demolished concrete are available on construction sites which are now posing a serious problem for transport in urban areas. Day by day this amount is larger and the reasons are that:- Many old buildings, concrete sidewalks, bridges and other structures have exceeded their age limit use due to structural deterioration.- Other possible structures for use are in ruin, because they are not serving the needs of today's society.- Structures have become waste resulting from natural disasters like cyclones, earthquakes,floods etc.As a result of greater demand for concrete, taking into account the fact that aggregate isthe component with the largest participation in concrete. Decreasing the source of natural aggregate we should explore the use of recycled aggregate. Recycled aggregate has goodquality especially in resistance to pressure when the content of brick is not more than 0.5%, it presents the potential for use in a wide range of applications, for the case when it meets the test and performance requirements. However the quality of the concrete which is made with recycled aggregate is lower compared to concrete which is made with natural aggregate.Nowadays, the application of recycled aggregate in construction areas is extensive. It's application is different from country to country, in the sense that each state sets the criteriafor use depending on it's quality.Based on the experience of use, recycled aggregate can be used for: production of concrete, in concrete roads, for production of concrete domes, as padding of the embankment,for construction of pipes, production of concrete blocks etc. Almost in all cases where natural aggregate is used.Based on laboratory analysis Recycled aggregate compared with natural aggregate: absorbsmore water, it has less density in many cases, it has lower specific weight, lower resistance to abrasion, it's more easily to destroy it, it contains more dust particles etc. Due to these results to gain the desired work ability of concrete obtained from the recycled aggregate is necessaryto add a certain amount of water to saturate recycled aggregate before or during mixing with other ingredients of concrete, if not previously used any additional reducing the rate of water absorption. On the other hand it is very important to use the concrete with recycling aggregate for the concrete which offer very good properties in thermo insulation, such a very important request in efficiency of energy

Analysis of the properties of masonry mortars made with recycled fine aggregates for use as a new building material in Cuba

This paper details the research work carried out on masonry mortars produced employing recycled aggregates in 100% substitution for natural sand aggregates. The main objective of the work being the validation of the resulting recycled aggregate mortar for use as a new construction material in Cuba. The recycled aggregates were acquired from the crushing of demolition material obtained from four different houses of distinct construction types. The work was carried out in two experimental stages. In stage 1, mortars with different percentages of recycled aggregates were produced and analysed. The analysis was carried out in order to achieve the optimal mix dosage, while employing the largest usable volume of recycled aggregates and in compliance with the functional requirements established by Cuban regulations. In stage 2, all mortars were produced employing the defined optimal mix proportion The fresh state properties (water retentivity) and hardened state (flexural, compression and bond strengths and capillary absorption capacity) were evaluated in the mortars produced with the other three mixed recycled aggregates of different compositions. It was concluded that the mortars produced with recycled aggregates needed less filler than that of the control mortar in order to obtain adequate properties in their fresh state. However, these recycled aggregate mortars obtained lower mechanical properties and higher capillary absorption that those of the control mortar. Nevertheless they were in compliance with the minimum requirements established in the Cuban regulation.Postprint (published version