BITS Faculty Publications

Permanent URI for this communityhttp://localhost:4000/handle/123456789/1867

Browse

Author: search.filters.author.Barai, Sudhir KumarSubject: search.filters.subject.Recycled aggregate concrete

Search Results

Now showing 1 - 10 of 20
  • No Thumbnail Available
    Item
    Green concrete : a sustainable construction material
    (Springer, 2025) Barai, Sudhir Kumar
    This book explores recycling and reusing construction wastes as alternative coarse aggregates and presents this as a possible solution for the major challenge of making sustainable concrete. It explores the reduction of cement use and the overcoming of some inferiorities in recycled coarse aggregate through the partial substitution of cement with supplementary cementitious materials (SCMs). The book evaluates the effect of low-volume SCMs (mainly fly ash) in 100% recycled coarse aggregate based concrete and comprehensively investigates this sustainable concrete for strength, safety, serviceability and sustainability. More specifically, this book discusses macro and microstructure properties, environmental impact assessment and performance of structural components. It explores the use of the particle packing mix design method (PPM) for concrete proportioning as it compensates lesser modulus of elasticity of RAC and is beneficial in lowering the environmental impact of concrete. Necessary modifications in mix design, mixing and design of concrete mixes are suggested to make this concrete safe for construction practice. It illustrates different mechanisms and results through figures, histograms, tables and experimental test pictures showing the failure pattern of structural elements and microstructure of concrete. Readers can get a clear understanding of the performance of this SCM incorporated RAC at various scales like micro, macro and structural components.
  • No Thumbnail Available
    Item
    Production and characterization of materials
    (Springer, 2025-10) Barai, Sudhir Kumar
    In the previous chapter, we have discussed the pressing need for a durable and green concrete. Use of recycled concrete aggregates as coarse aggregate replacement and other SCMs as partial cement substitute can become potential alternative constituents in concrete. Aggregates constitute 75–80% of the volume of concrete. In this chapter, we will mainly discuss the production of coarse recycled concrete aggregates which are obtained by recycling, sorting, and processing of the construction demolition wastes at the end-of-life of a concrete structure. Thus, waste collection, segregation, and processing methods to prepare them for use as coarse aggregates in concrete are discussed. While aggregates are mostly inert materials which do not participate actively in chemical reactions, their qualities can still impact the fresh and hardened properties of concrete. Thus, it is crucial to understand the properties of recycled aggregates in contrast to natural aggregates. When we fully substitute recycled coarse aggregates for natural coarse aggregates, it is interesting to see how the characteristics of the coarse aggregates impact the performance of concrete at macro-level. This chapter also discusses the properties of commonly available SCMs, like fly ash, slag, and silica fume, which can be utilized to positively modify the performance of RAC.
  • No Thumbnail Available
    Item
    Microstructure properties
    (Springer, 2025-10) Barai, Sudhir Kumar
    Concrete comprises of three different phases such as (1) aggregate, (2) hardened cement matrix and (3) interfacial transition zone (ITZ) between the aggregate and matrix. Heterogeneity in concrete at the microstructural level is caused mainly due to the non-uniform distribution of water in the zone near an aggregate edge and that farther from the aggregate that is in the matrix region. Phenomena which occur closer to an aggregate surface in concrete are: (1) availability of more water which facilitates formation of larger size capillary voids after hydration (2) growth of preferentially oriented layer of crystalline hydrated products (mainly calcium hydroxide) and (3) development of microcracks even prior to loading. Moreover, the microstructure rather than being fundamentally constant, varies with curing ages. Presence of aggregates in general (due to wall effect) and types of aggregate such as recycled coarse aggregate in particular result in a complicated and inhomogeneous microstructure than the plain cement paste. The layer of adhered mortar on the surface of recycled coarse aggregate makes the interface more complex. In this chapter, we will try to find out answer to the following questions: How does incorporation of supplementary cementitious materials alter the aggregate-matrix interface in recycled aggregate concrete? How do the microstructural properties affect the macro behaviour of concrete?
  • No Thumbnail Available
    Item
    Environmental impact of concrete
    (Springer, 2025-10) Barai, Sudhir Kumar
    Sustainable concrete production demands satisfaction of the two most important criteria such as optimization of resources and minimization of end-of-life wastes. As discussed in the previous chapters, one of the important ways in which this can be achieved is by using coarse recycled concrete aggregates (RCAs) as an alternative to natural coarse aggregates and other industrial wastes as supplementary cementitious materials (SCMs). In this regard, the role of a suitable mix design method for obtaining an optimum combination of concrete constituents is also significant. In this chapter, sustainability of 100% recycled coarse aggregate concrete (RAC) along with SCMs in concrete is explored through performing life-cycle assessment, especially focusing on concrete with coarse RCA and low-volume fly ash as cement substitute (denoted as FARAC) in concrete. The effect of particle packing method (PPM) of mix proportioning on the environmental impact of FARAC is assessed for a case study of India.
  • No Thumbnail Available
    Item
    Behaviour of reinforced concrete slabs under punching shear
    (Springer, 2025-10) Barai, Sudhir Kumar
    Flat slab supported by an interior column is a complicated problem due to the most likely phenomenon of punching shear failure. This chapter discusses the punching shear behaviour of recycled aggregate concrete with coarse RCA. In the context of using SCMs in concrete, we address the following question: How does low-volume fly ash as a cement substitute alter the punching shear of RAC flat slabs? Another aspect while using any recycled material is maintaining the level of structural safety as that of the already existing material. The punching shear resistance design equation, available for the standard reinforced concrete slabs, may not yield a safe design for RAC slabs due to greater uncertainties. The reliability of standard punching shear models is assessed and modified to ensure equivalent safety for RAC and NAC flat slabs. It is crucial to conduct this reliability analysis in order to confidently establish fly ash and 100% coarse RCA as alternative concrete constituents in practice.
  • No Thumbnail Available
    Item
    Fresh concrete properties
    (Springer, 2025-10) Barai, Sudhir Kumar
    Concrete constituted of coarse recycled concrete aggregate and supplementary cementitious materials must display technical properties similar to or within an acceptable range of deviation when compared to the existing conventional concrete. This enables reliable adoption of the new materials as alternative concrete constituents in practice. This chapter explores the material level concrete properties in the fresh state focusing on the role of coarse recycled concrete aggregates (coarse RCA) and challenges associated with it. Then the synergistic effects of SCMs and coarse RCA in concrete are explored. Fresh concrete properties focused here are workability, segregation, and bleeding, and setting time. The roles of SCMs discussed in this chapter are limited to the widely available materials such as fly ash, slag, and silica fume.
  • No Thumbnail Available
    Item
    Recent advances, recommendations, and way forward
    (Springer, 2025-10) Barai, Sudhir Kumar
    The use of concrete construction has never been so rampant before and the demand is continuously rising. As a result, the environment is overburdened with the increased CO2 emissions associated with cement and exploitation of limited natural resources to produce other constituents of concrete such as coarse or fine aggregates. This book has mainly focussed on the recycling and reuse of construction demolition wastes as alternative coarse aggregates and partial cement substitution by other supplementary cementitious materials (SCMs) to produce sustainable concrete. This combination not only helps in managing construction and demolition waste but also enhances the performance and durability of concrete. The inclusion of SCMs has proven to compensate some of the inherent inferiorities associated with coarse RCA based concrete which is discussed previously in other chapters. However, their practical application presents several challenges that need to be addressed to maximize their potential. This chapter explores concerns associated with this recycled concrete and available recent studies to address these issues.
  • No Thumbnail Available
    Item
    Behaviour of reinforced concrete beams
    (Springer, 2025-10) Barai, Sudhir Kumar
    In the preceding chapters, we have discussed the properties of concrete, specifically focussing on the material behaviour of SCM and recycled coarse aggregates. The primary challenge in incorporating this sustainable recycled material is to fulfil the performance requirements of structural elements subjected to flexural, shear, and compression. The behaviour of reinforced concrete RAC beams under bending and shear is discussed in this chapter. Load carrying capacity, failure pattern and effects of material parameters are examined for fly ash incorporated 100% RAC beams. We evaluate the suitability of current code provisions for natural aggregate concrete to be used in RAC with fly ash beams. Furthermore, reliability of structural elements is evaluated, considering the variabilities associated with these recycled materials. Necessary modifications are suggested to achieve the same level of safety as conventional concrete.
  • No Thumbnail Available
    Item
    Mixing and mix proportioning methods
    (Springer, 2025-10) Barai, Sudhir Kumar
    Concrete performance depends not only on the constituent materials but also on the proportions in which the materials are mixed and the order of mixing during casting. So, the constituents of known qualities need to be proportioned accordingly to achieve concrete of desired performance. This chapter explores the utilization of the particle packing method for mix design, specifically for determining the appropriate proportions of fly ash and coarse recycled concrete aggregate (RCA) in concrete. The effects of mixing methods such as two-stage and triple mixing are also discussed in this context.
  • No Thumbnail Available
    Item
    Hardened concrete properties
    (Springer, 2025-10) Barai, Sudhir Kumar
    Concrete made with coarse recycled concrete aggregate and supplementary cementitious materials must display technical properties similar to or in an acceptable range of deviation as compared to the existing conventional concrete. This enables reliable adoption of coarse RCA and SCMs as an alternative concrete constituents in practice. In the previous chapter, we have discussed the effect of SCMs on fresh properties of recycled aggregate concrete. This chapter discusses the hardened concrete properties of concrete comprising of coarse RCA and challenges associated with it. Then the synergistic effects of SCMs and coarse RCA in concrete are explored. The mechanical properties focused here include compressive strength, tensile strength, and modulus of elasticity. The roles of SCMs discussed in this chapter are limited to the widely available fly ash, slag, and silica fume. Introduction of SCMs also has an influence on hardened concrete properties, and the degree depends on percentage of replacement, physical properties like fineness, chemical and mineralogical composition, chemical reactivity, and curing age and conditions. In this chapter, let us discuss first, the mechanical properties of concrete comprising of coarse RCA and then the effect of SCMs on coarse RCA-based concrete, specifically focusing on the influence of fly ash on 100% coarse RCA-based concrete.