Lack of vibrations on fresh concrete negatively in uences the compaction and thus the quality of concrete. This is particularly concerning with geopolymer concrete (GPC) containing sodium silicate (Na 2 SiO 3 ), which is viscous in nature. In this study, self-compacting geopolymer concrete (SCGC) containing y ash (FA) and ultra ne slag (UFS) with copper slag aggregates (CSA) was proposed and investigated. CSA were used as a substitute to sand (by weight) in SCGC at different percentages up to 60%. In the fresh state, slump, T500 slump ow, V-funnel, L-box, U-box, and sieve aggregation ratio tests were performed to investigate owability, passing ability, and viscosity. At the hardened state, the compressive strength, water absorption, chloride ion resistance and sorptivity tests were examined. The owability of SCGC improved when CSA were added, and the highest slump of 735 mm was achieved for the mix with 60% CSA. Substitution of up to 20% of CSA enhanced the properties of SCGC at all ages. Mix having 20% CSA (20CSA-SCGC) was superior to other mixes, exhibiting the highest compressive strength (47 MPa) at 365 days while possessing the lowest water absorption, sorptivity, and the highest chloride ion resistance. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses also con rmed the improved microstructure of Mix 20CSA-SCGC. Meanwhile, X-ray diffraction (XRD) analysis con rmed the presence of quartz and calcium silicate hydrate (CSH) products, which were the main contributors to properties enhancement. HighlightsUtilization of copper slag aggregates as partial substitution to sand. SCGC with improved mechanical and durability properties.Microstructure of SCGC studied using SEM, XRD and EDS analyses.Correlations between different properties were established.
This study examines the suitability of alternate binders and crumb rubber (CR) to produce light weight alkali-activated concrete (AAC). For this, strength, and durability performance of AAC incorporating CR by partially replacing fine aggregate was studied. To produce AAC, four different binders, including fly ash, rice husk ash (RHA), metakaolin, and bottom ash were used.Fine aggregates were substituted with CR at 0%, 10%, 20%, and 30% for each AAC mix (with different binders). Furthermore, the mixes were prepared using 12 M sodium hydroxide (NaOH) solution, and the ratio of sodium silicate (Na 2 SiO 3 ) to NaOH was taken as 2.5. The samples were cured at ambient temperature. Strength and durability properties, including permeability through water absorption and acid attack (hydrochloric acid [HCl] and sulfuric acid [H 2 SO 4 ]), were also checked. Results of this study revealed that the strength decreased with the increase in CR content. Further, this decrease was high at 30% replacement but strength was satisfactory. AAC showed good relationships among compressive, flexural, and split tensile strengths. Similar footprints were observed for permeability results. However, highest water absorption was observed for bottom ash binder (with 30% substitution of CR).Mixes with fly ash and metakaolin binders outperformed the other mixes while comparing the compressive strength of acid exposed samples. Overall, a sustainable and durable light weight AAC can be prepared using 20% CR.
Utilization of industrial by‐products in concrete is an effective way to reduce the exhaustion of raw materials for concrete production, but it can lead to degradation in concrete properties. Therefore, research efforts are required to achieve a balance between waste utilization and concrete performance. This study examined the strength and durability performance of geopolymer concrete (GPC) developed from fly ash (FA) and fine rice husk ash (FRHA) as main binders (50/50), with partial OPC substitution at different levels (0%–30%). Various properties like workability, compressive strength, water absorption, chloride penetration resistance, carbonation depth, electrical resistivity (ER), and acid attack resistance were experimentally investigated. Results indicated that there was a noticeable improvement in the workability with 20% OPC substitution, achieving the highest slump of 110 mm. The highest compressive strength (50 MPa) was attained with 15% OPC substitution after 90 days. Mix FR85C15 (15% OPC replacement) showed the highest durability performance at all ages through various indicators, that is, water absorption, charge passed, carbonation depth, and ER. Scanning electron microscopy and energy dispersive spectroscopy analyses also validated the enhanced microstructure of FR85C15 compared with other mixes. When exposed to sulfuric acid (H2SO4), Mix FR85C15 showed a minimal loss of 14% in compressive strength. It was concluded that GPC produced using FA and FRHA substituting OPC (up to 15%) can potentially be utilized for structural applications.
This study aimed at investigating the durability characteristics of the ambient-cured geopolymer concrete (GPC) developed using recycled coarse aggregate (RCA) and ultrafine slag (UFS). Two series of mixes were prepared. Natural aggregates (NAs) were replaced by RCA at different volume levels of 0, 25, 50 and 100% in both series. Meanwhile, UFS was added as a replacement by volume of fly ash at varying levels of 0, 15, and 30% in the first series, while UFS was used in addition to fly ash by percentage weight of fly ash at the levels of 0, 15, and 30% in the second series. The compressive strength, water absorption, chloride ion penetration, and carbonation depth of the developed ambient-cured GPC were studied. In addition, creep and drying shrinkage of the specimens were also examined. It was found that the compressive strength increased with the UFS content, while the opposite trend was observed with increasing RCA%. The highest compressive strength obtained with 100% RCA was 40.21 MPa (at 90 days), when 30% UFS was used in addition to fly ash. The addition of UFS not only helped in improving the strength characteristics but also provided an alternative to heat curing, which is a major drawback of GPC. Furthermore, the negative effects of RCA can also be minimised by adding UFS, which can be used as a compensator to RCA to improve the durability characteristics. The experimental results prove that susceptibility to chemical, water and chloride attacks can be mitigated by incorporation of UFS, and durable GPC can be produced by using RCA and UFS.
Lack of vibrations on fresh concrete negatively influences the compaction and thus the quality of concrete. This is particularly concerning with geopolymer concrete (GPC) containing sodium silicate (Na 2 SiO 3 ), which is viscous in nature. In this study, self-compacting geopolymer concrete (SCGC) containing fly ash (FA) and ultrafine slag (UFS) with copper slag aggregates (CSA) was proposed and investigated. CSA were used as a substitute to sand (by weight) in SCGC at different percentages up to 60%. In the fresh state, slump, T500 slump flow, V-funnel, L-box, U-box, and sieve aggregation ratio tests were performed to investigate flowability, passing ability, and viscosity. At the hardened state, the compressive strength, water absorption, chloride ion resistance and sorptivity tests were examined. The flowability of SCGC improved when CSA were added, and the highest slump of 735 mm was achieved for the mix with 60% CSA. Substitution of up to 20% of CSA enhanced the properties of SCGC at all ages. Mix having 20% CSA (20CSA-SCGC) was superior to other mixes, exhibiting the highest compressive strength (47 MPa) at 365 days while possessing the lowest water absorption, sorptivity, and the highest chloride ion resistance. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses also confirmed the improved microstructure of Mix 20CSA-SCGC. Meanwhile, X-ray diffraction (XRD) analysis confirmed the presence of quartz and calcium silicate hydrate (CSH) products, which were the main contributors to properties enhancement.
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