•POFA with and without heat treatment was utilized to produce HSGC.•Heat treatment reduced the LOI and carbon content of POFA.•Heat-treated POFA produced HSGC with superior engineering.•POFA improved ...the HSGC fluid transport properties.•Proper curing improved the strength and durability properties of HSGC.
The primary focus of this work was to utilize the waste of palm oil industry as a supplementary binder for producing high strength concrete (HSC) whose strength reached 116MPa. The treatment of ground POFA (GPOFA) to produce ultrafine or treated POFA (UPOFA) changed its fineness, unburned carbon composition and percentage of pozzolanic minerals (SiO2+Al2O3+Fe2O3) and led to the production of high strength concrete dubbed HSCg and HSCu, respectively. The characteristics of HSCu indicated UPOFA positive contributions towards workability, strength and permeability (gas and water, chloride penetration and migrations). At the age of 180days, HSCu containing 20, 40 and 60% of UPOFA resulted in the compressive strength of 108.6, 114.4 and 112.4MPa, respectively as against the maximum of 106.5MPa and 105.1MPa in HSCg and POFA-free high strength concrete (HSC-OPC), respectively. HSCu samples also have the best fluid transport properties when compared to HSCg and HSC-OPC.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
The interfacial bond characteristics between normal concrete substrate as old concrete and ultra high performance fiber concrete as repair material have been investigated. Normal concrete substrates ...were first subjected to different surface preparation methods prior to bonding the ultra high performance fiber concrete to form repair composites. The interfacial mechanical bond of the composites was assessed using slant shear and tensile splitting strength tests. In addition, rapid chloride permeability test was performed to ascertain the potential chloride resistance of the composites. The microstructure of the transition zone between the normal concrete and ultra high performance fiber concrete was also studied using scanning electron microscope. The results generally indicate that surface preparation of the substrate is very much required to obtain superior mechanical bond of the composites; whereby the composites with the sand-blasted substrate providing the most superior mechanical bond. The excellent bond of the composite is also evident through the rapid chloride permeability test, as well as confirms by the scanning electron microscope image of the interface. Hence, the ultra high performance fiber concrete exhibits significant potential as an excellent material for repair and rehabilitation of concrete structures.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
► Newly overlay UHPFC is able to achieve high bond strength with the NC substrates. ► Sand blasted surface give the best interfacial mechanical bonding in comparison to other surface preparation ...methods. ► UHPFC overlay significantly improves the impermeability characteristics of the repaired NC substrate.
As a rule of thumb, the interfacial bonding between deteriorated concrete structures with a newly overlay repair material is one of the most important factors for structural functionality and safety as well as durability performance. In order to acquire an enhanced resistance against penetration of harmful substances, a good and effective bonding is necessary at the concrete interfaces. The objective of this study is to examine experimentally the mechanical properties and permeability characteristics of the interface between normal concrete (NC) substrate which represents old concrete structures and an overlay of ultra high performance fiber concrete (UHPFC) as a repair material. The mechanical interfacial bond characteristics were assessed using the slant shear and splitting tensile tests to quantify the influence of the differently roughened substrate surfaces. On the other hand, the permeability characteristics were evaluated by means of the rapid chloride permeability, gas and water permeability tests. The results show that the newly overlay UHPFC achieves high bond strength and bonds efficiently with the NC substrates. The specimens with sand blasted substrate surface give the best interfacial mechanical bonding in comparison to other types of surface preparation. The permeability tests proved that the interfacial bonding is very good and efficient which significantly improve the impermeability of the composites, and this was clearly shown by the SEM micrograph of the interface. Hence, it is envisaged that the use of UHPFC concomitant with appropriate surface preparation of the substrate should be able to provide effective and durable concrete repair.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
► POFA–HSGCs exhibit improved workability. ► Inclusion of ultrafine POFA retards setting times. ► POFA–HSGCs have higher 28-days strength at POFA contents of up to 60%. ► The POFA–HSGCs have superior ...transport properties. ► The ultrafine POFA proves to be an efficient mineral admixture.
The engineering and transport properties of high-strength green concrete (HSGC) containing up to 60% of ultrafine palm oil fuel ash (POFA) have been studied. POFA obtained from a palm-oil industry was treated via heat treatment to remove excess carbon and ground to a median particle size of about 2μm. The ultrafine POFA obtained was then utilized in the production of HSGCs with POFA replacement levels of 0%, 20%, 40% and 60% by mass of ordinary Portland cement. The results show that the treatment processes undertaken results in a highly efficient pozzolan. For fresh concrete, the inclusion of the ultrafine POFA tends to increase the workability of the HSGCs, and retards the setting times in particular at higher POFA contents. In the case of compressive strength, the inclusion of the ultrafine POFA reduces early age strength of the HSGCs at 1, 3 and 7days, but enhances the strength at 28days for all HSGCs containing POFA, where strength exceeding 95MPa was achieved for all the POFA–HSGCs. Whereas the transport properties as assessed via porosity, initial surface absorption, rapid chloride permeability, gas permeability and water permeability tests are significantly improved with the inclusion of the ultrafine POFA, with the HSGC containing 60% POFA exhibiting the greatest improvement at 28days. Thus, the overall results show that the ultrafine POFA possesses significant potential as an efficient pozzolanic mineral admixture for the production of HSGC with promisingly superior engineering and transport properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
► The influence of different supplementary cementitious materials (SCMs) on engineering properties of HSC was assessed. ► Workability, strength and pore structure of HSC were significantly affected ...with the inclusion of the different SCMs. ► The accuracy of standard prediction models in estimating elastic modulus of HSC containing SCMs was evaluated.
The influence of supplementary cementitious materials (SCMs), namely silica fume, metakaolin, fly ash and ground granulated blast-furnace slag, on the engineering properties of high strength concrete (HSC) has been investigated in this study. Workability, compressive strength, elastic modulus, porosity and pore size distribution were assessed in order to quantify the effects of the different materials. The results show that the inclusion of the different SCMs has considerable influence on the workability of HSC. Silica fume and metakaolin significantly enhanced the strength of HSC. Fly ash reduced the early-age strength; however, it enhanced the long-term strength of the HSC. Likewise, ground granulated blast-furnace slag impaired the early-age strength, but marginally improved the long-term strength at low replacement levels. The general effect of the different SCMs on the elastic modulus of HSC is rather small compared to their effect on strength. There are good correlations between both static and dynamic moduli and compressive strength. The EC 2 and ACI 209 provide a good estimate of static modulus of elasticity from compressive strength, while the BS8110 gives a good estimate of static modulus of elasticity from dynamic modulus of HSC containing the different SCMs. Porosity and pore size were reduced with the addition of the different SCMs. The volume of mesopores in the ranges of <15
nm and 15 – 30
nm was notably increased for HSC containing SCMs, whereas the percentage of macropores was significantly reduced.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
•We examine the bond characteristics between NC substrate and GUSMRC repair material.•The bond strength increases as the age of the NC/GUSMRC composite increases.•The sand blasting surface treatment ...enhances the bond strength more than the grinding treatment.•GUSMRC seems to be a very promising material for the repair and rehabilitation of RC structures.
This study investigated the interfacial bond strength between a new Green Universiti Sains Malaysia Reinforced Concrete (GUSMRC) as a repair material and the existing normal concrete substrate (NC) using two methods of surface treatment: grooving and sandblasting. The bond strength was evaluated via the slant shear, splitting tensile, and pull-off strength tests at 7, 28, and 90 days. The results showed that the bond strength of the NC/GUSMRC composite was extremely high, especially with the sandblasting surface treatment. The slant shear results showed that the specimens with sandblasting surface treatment showed almost 1.5 times higher slant shear strength than the strength of those with the grooving surface treatment at the three tested ages. The splitting strengths of the sandblasted samples were 8.3%, 20.7%, and 18.5% higher than the strengths of the grooved samples at 7, 28, and 90 days, respectively. Similarly, the pull-off strengths of the sandblasted specimens were 2.3%, 10%, and 14.5% higher at 7, 28, and 90 days, respectively. The bond strength increased as the age of the composite increased. Therefore, GUSMRC has great potential in the rehabilitation of RC structures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
•FRP bars lost up to 55% of their tensile strength at a critical temperature of 325°C.•Concrete-FRP bond was significantly reduced upon exposure to high temperatures.•FRP bars lost up to 81.5% of ...their bond strength at critical temperature of 325°C.•The analytical model, proposed in this study, showed good predictability.
This paper presents the results of an experimental study on the effect of elevated temperatures on the mechanical properties of FRP bars and the bond behavior between FRP bars and concrete. Four types of reinforcement bars namely: basalt fiber reinforced polymer (BFRP), CARBON fiber reinforced polymer (CFRP), glass fiber reinforced polymer (GFRP), and steel bars of 10mm diameter were used. The results showed that the FRP bars suffered significant reductions in their mechanical properties upon exposure to high temperatures of up to 450°C at which the GFRP and BFRP melted and lost their total tensile strength capacity. At a critical temperature of 325°C, the FRP bars lost as high as (55% and 30%) of their tensile strength and elastic modulus, respectively. The percentage reduction in mechanical properties and bond strength was more pronounced in specimens with FRP bars than those with steel bars under elevated temperatures; the percentage reductions in bond strength between concrete and FRP bars reached as high as 81.5% after exposure to 325°C. Based on the experimental results, an empirical model was proposed to predict the post-heating bond stress-slip relationship between the FRP bar and the surrounding concrete: a good agreement was noticed between the experimental results and the proposed model.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
One of the major disadvantages in ultra-high-performance-fiber reinforced concrete (UHP-FRC) is its high ordinary Portland cement (OPC) content, which directly translates into an increase in OPC ...production. More OPC production results in increased emission of greenhouse gases, as well increased electrical energy consumption and concrete price. This study is aimed at adjusting the binder content (OPC and silica fume (SF) contents) of UHP-FRC using the response surface method. The present investigation shows that, for a given water/binder and superplasticizer/OPC, the compressive strength is independent of the binder content, whereas the flow depends on the binder content. Increasing the binder content does not enhance the strength compared with the required design strength because the capillary porosity increases with increasing OPC content; however, the workability increases. The final result is the production of a UHP-FRC with an OPC content of 720.49kg/m3, an SF content of 214.25kg/m3, a compressive strength of 181.41MPa, a direct tensile strength of 12.49MPa, a bending tensile strength of 30.31MPa, and a flow of 167mm.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
•Geopolymer was synthesized from high content of treated palm oil fuel ash.•TPOFA-based geopolymer mortar gained compressive strength of 47MPa at 7days.•The optimized TPOFA-geopolymer mortar mixture ...was analysed using XRD and FTIR.•The main binding phases consist of N–A–S–H and C–S–H gels.
The aim of this study was to synthesize geopolymers using a large amount of treated palm oil fuel ash (TPOFA). The efficiency of the TPOFA (as the source material) in producing geopolymer products was enhanced via six factors which were optimized using the Taguchi method L25. The six factors were divided into two different components: (i) additive materials i.e. Ca(OH)2, silica fume (SF), Al2(OH)3, and (ii) alkaline activators; i.e. NaOH concentration (moles), Na-silicate: NaOH ratio, and alkali-activator:solid-material ratio. Each of these factors was examined on five levels in order to obtain the optimum mixture. A total of 25 mixtures were prepared in accordance to the L25 array proposed by the method. The performance of the specimens was evaluated by compressive strength tests. The results show that the optimum mixture consisted of 65wt.% TPOFA and 35wt.% additive materials which achieved a compressive strength of 47.27±5.0MPa after 7days of curing. The properties of the optimized mixture were further analyzed via X-ray diffractography (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses. The results show that the main binding phases consist of aluminosilicate type gel “N–A–S–H” (Na2O–Al2O3–SiO2–H2O) and calcium silicate hydrate (C–S–H) gels, formed simultaneously, within the TPOFA-based geopolymer mortar.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
•We develop a new class of green UHPFRCCs, designated as (GUSMRC).•We examine the changes in the UPOFA content about properties of GUSMRC mixtures.•We optimize the binder content of GUSMRC mixtures ...using RSM.
This paper presents an ideal experimental design based on the response surface method (RSM) to develop a new class of Green Ultra-High Performance Fiber Reinforced Cementitious Composites (GUHPFRCCs), in which 50% of the volume contains ultrafine palm oil fuel ash (UPOFA). This green concrete is currently under development at the Universiti Sains Malaysia (GUSMRC). This could lead to the greater utilization of POFA in concrete and, subsequently, could be useful in protecting the environment by minimizing volume of waste disposed on the wasteland and minimizing emission of greenhouse gases that released during cement production, besides contribute to cost saving which could somehow contribute towards the sustainability of the concrete industry. The results showed that at 90days the optimum mix was achieved 158.28MPa, 46.69MPa and 13.78MPa of compressive strength, bending tensile strength and direct tensile strength, respectively, with 50% replacement levels of the total binder content by UPOFA, indicating the ability of using UPOFA as an efficient pozzolanic mineral admixture for the production of GUSMRC with promisingly superior engineering properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
