Effects of SCMs and nano- and ultrafine-materials on mechanical properties and carbon footprint of recycled aggregate concretes
By: Shaikh, Faiz Uddin Ahmed
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Description: 55-64p.Subject(s): Construction Engineering and Management (CEM)Online resources: Click here
In:
Indian Concrete JournalSummary: This paper presents the effects of supplementary cementitious materials (SCMs) (Fly ash, slag and silica fume) and emerging nano- and ultrafine-materials (nano silica and ultrafine fly ash) on mechanical properties of concrete containing 50% recycled coarse aggregate (RCA) as partial replacement of natural coarse aggregate. The RCA are mixed construction and demolition (C&D) waste consisted of concrete, masonry and other materials. In the first part, the effects of 50% slag or 50% fly ash as partial replacement of ordinary Portland cement (OPC) in concrete containing 50% RCA is evaluated, while in second part the effects of 5, 10 and 15% silica fume on above recycled aggregate concrete containing 50% slag or 50% fly ash are evaluated. In third part, the effects of 2% nano silica (NS) and 10% ultrafine fly ash (UFFA) on concrete containing 50% RCA are evaluated. The above results are compared with control concrete containing 100% and 50% natural coarse aggregate. Water-to-binder ratios of all concrete are kept constant, however, superplasticizer is added in the mixes containing silica fume, nano silica and ultra fine fly ash to improve the workability. The compressive and indirect tensile strengths of all concrete are measured at 7, 28, 56 and 91 days. The results show that due to addition of 50% RCA the compressive strength of concrete at all ages is reduced significantly compared to control concrete containing 100% natural coarse aggregates. The addition of high volume fly ash and slag further reduced the compressive strength of recycled aggregate concrete at all ages, where high volume fly ash shows more reduction in compressive strength than high volume slag. The addition of silica fume is, however, recovered the compressive strength reduction of both high volume fly ash and slag concretes containing 50% RCA. The addition of nano silica and ultrafine fly ash also improved the compressive strength of recycled aggregate concrete. Similar results are also observed in the case of indirect tensile strength. The carbon footprint of recycled aggregate concrete is slightly higher than the control concrete. However, the addition of SCMs reduced the carbon footprint significantly.
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Articles Abstract Database
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School of Engineering & Technology (PG) Archieval Section | Not for loan | 2020382 |
This paper presents the effects of supplementary cementitious materials (SCMs) (Fly ash, slag and silica fume) and emerging nano- and ultrafine-materials (nano silica and ultrafine fly ash) on mechanical properties of concrete containing 50% recycled coarse aggregate (RCA) as partial replacement of natural coarse aggregate. The RCA are mixed construction and demolition (C&D) waste consisted of concrete, masonry and other materials. In the first part, the effects of 50% slag or 50% fly ash as partial replacement of ordinary Portland cement (OPC) in concrete containing 50% RCA is evaluated, while in second part the effects of 5, 10 and 15% silica fume on above recycled aggregate concrete containing 50% slag or 50% fly ash are evaluated. In third part, the effects of 2% nano silica (NS) and 10% ultrafine fly ash (UFFA) on concrete containing 50% RCA are evaluated. The above results are compared with control concrete containing 100% and 50% natural coarse aggregate. Water-to-binder ratios of all concrete are kept constant, however, superplasticizer is added in the mixes containing silica fume, nano silica and ultra fine fly ash to improve the workability. The compressive and indirect tensile strengths of all concrete are measured at 7, 28, 56 and 91 days. The results show that due to addition of 50% RCA the compressive strength of concrete at all ages is reduced significantly compared to control concrete containing 100% natural coarse aggregates. The addition of high volume fly ash and slag further reduced the compressive strength of recycled aggregate concrete at all ages, where high volume fly ash shows more reduction in compressive strength than high volume slag. The addition of silica fume is, however, recovered the compressive strength reduction of both high volume fly ash and slag concretes containing 50% RCA. The addition of nano silica and ultrafine fly ash also improved the compressive strength of recycled aggregate concrete. Similar results are also observed in the case of indirect tensile strength. The carbon footprint of recycled aggregate concrete is slightly higher than the control concrete. However, the addition of SCMs reduced the carbon footprint significantly.
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