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ABSTRACT The chemical constituents of precursor materials, the composition and concentration of alkaline activators, volume of free water, and curing conditions are some of the mix design variables that influence [...]

ABSTRACT Silicomanganese (SiMn) fume is an industrial waste whose potency in the synthesis of alkaline activated mortar is yet to be explored. The major constituents of SiMn fume are Si[O.sub.2], [...]

The influence of varying contents of supplementary cementitious material, namely silica fume (SF), on the transport properties of ultra-high performance concrete containing polyethylene therephthalate (PET) fibers under a steam curing regime has been investigated in this study. SF was used as a supplementary binder as a partial replacement of the ordinary portland cement (OPC) in different proportions (5, 10, 15, 20, 25, 30, and 35 %), whereas shredded waste plastic PET bottles were used as fiber reinforcements at 1 % of the total mass binder to produce ultra high performance PET reinforced concrete (UHPPRC). The presence of SF between (5 % and 30 %) in UHPPRC increases compressive strength at all ages of 3, 7, and 28 days; the greatest compressive strength achieved was 146.6 MPa by the SF25-UHPPRC mix, but the compressive strength reduced at higher SF contents, in particular for the SF35-UHPPRC. Besides, the SF inclusion improved the transport properties of PET-fiberized concrete. The greatest improvement was seen with SF25-UHPPRC, which showed increases of 75.2 % in porosity, 92.6 % in water permeability, and 95.8 % in rapid chloride permeability relative to the control mix at 28 days. This could indicate that the incorporation of SF and PET fiber increases the possibility of using PET fibers in the production of ultra-high performance PET fiber reinforced concrete with superior engineering and transport properties.

The corrosion of steel reinforcement by chloride is commonly recognized as a key factor that contributes to the degradation of durability in reinforced concreae structures. Using supplementary cementitious materials, such as industrial and agricultural waste materials, usually enhances the impermeability of the concrete and its corrosion resistance, acid resistance, and sulfate resistance. This study’s primary purpose is to examine the effects of replacing ordinary Portland cement (OPC) with ultrafine palm oil fuel ash (U-POFA) on the corrosion resistant performance of high-strength green concrete (HSGC). There were four HSGC mixes tested; the first mix contained 100% OPC, while the other mixes replaced OPC mass with 20%, 40%, and 60% of U-POFA. The performance of all HSGC mixes containing U-POFA on workability, compressive strength, porosity, water absorption, impressed voltage test, and mass loss was investigated at 7, 28, 60, and 90 days. Adding U-POFA to mixes enhances their workability, compressive strength (CS), water absorption, and porosity in comparison with mixes that contain 100% OPC. The findings clearly portrayed that the utilization of U-POFA as a partial alternative for OPC significantly enhances the corrosion-resistant performance of the HSGC. In general, it is strongly advised that a high proportion of U-POFA be incorporated, totaling 60% of the OPC content. This recommendation is the result of its significance as an environmentally friendly and cost-effective green pozzolanic material. Hence, it could contribute to the superior durability performance of concrete structures, particularly in aggressive environmental exposures.

ABSTRACTThe study reports the influence of Al[(OH).sub.3] as alumina source on the compressive strength of POFA alkaliactivated mortar (POFA AAM). The synthesis of the developed POFA AAM stems from the [...]

ABSTRACTThe strength gain of alkali-activated binders (AAB) when cured at room temperature is delayed due to the slow polymerization process. This is the major impediment in the utilization of this [...]

ABSTRACT Development of alkali-activated binder (AAB) is fast becoming a viable alternative to ordinary portland cement (OPC). However, key engineering properties of such a binder depend strongly on the chemical [...]

ABSTRACT Global warming due to high greenhouse gasses emission coupled with excessive energy involved in concrete manufacturing process is indeed an alarming threat. To overcome the problem, numerous researches have [...]

ABSTRACT The stringent conditions are being imposed by the global community to reduce greenhouse gas emissions, will push the search for low carbon footprint alternative binders to ordinary Portland cement. [...]

ABSTRACT This paper presents an investigation into the durability performance of Palm Oil Fuel Ash-based Engineered Alkaline-activated Cementitious Composite (POFA-EACC) mortar exposed to sulfate environment. Cube specimens measuring 50 mm [...]

ABSTRACT Efficiency in energy-utilization in the adoption of curing methods and effects of NaOHaq concentration towards achieving a better strength performance in the synthesis of alkaline activated ground-steel-slag (GSS) with [...]

The main objective of this article is to utilize the response surface method (RSM) for optimizing and predicting the compressive strength, flexural strength, and splitting tensile strength with minimum cement content for Ultra High Performance Green Concrete (UHPGC) at 28 days. To harness sustainability, ultra-fine Palm Oil Fuel Ash (UPOFA) was employed as a substitute binder at 0%, 15%, 30%, and 45% of the cement mass of UHPGC production. Besides, Silica Fume (SF) substituted from the remaining cement mass with several percentages of 0%, 10%, 15%, and 20%. The experimental results showed the UHPGC (M13) mixture exhibited the greatest compressive, flexural, and splitting tensile strengths, registering 154.8 MPa, 32.18 MPa, and 11.1 MPa, respectively. For the RSM approach, there was a high degree of agreement between the model-predicted values and the actual. Thereby, the models developed had statistical significance and demonstrated a satisfactory correlation value (R2) of 98.11, 96.08, and 98.21 for compressive, flexural, and splitting tensile strength at 28 days, respectively. Hence, an effective strategy for enhancing the mix design of UHPGC could involve the application of the RSM method as an optimization technique. Based on this innovation, SF could extend UPOFA use in green concrete manufacturing, lowering waste volume disposal and costly power consumption for cement manufacture, thereby fostering concrete sustainability.

ABSTRACT In this study, combinations of ultrafine palm oil fuel ash (UPOFA) and ground blast furnace slag (GBFS) have been used to study the compressive strength and microstructure of the [...]

ABSTRACT Effects of Al[(OH).sub.3] content on the compressive-strength of alkaline activated ground blast furnace slag (GBFS)-ultrafine palm oil fuel ash (UPOFA) based mortar (AAGU) were investigated. The mortar was activated [...]

This study aims to examine the failure behaviour of damaged reinforced concrete (RC) beams retrofitted using externally bonded ultra-high-performance fibre-reinforced cementitious composites (UHPFRCCs) systems at different levels of damage levels. To overcome the sudden failure in shear at supports, one strip of UHPFRCCs was bonded on the tension face with four short strips on vertical sides covering the tension strip supports and ends of damaged RC beams. The results show that an increment in the average failure capacity over that of control beams was in the range of 24.37 to 38.39%. Moreover, the serviceability of RC beams showed a marked enhancement in failure mode, crack development and deflection capacity. 0.0% of the retrofitted beams failed in shear mode. It can be concluded that, the externally bonded UHPFRCCs technique can be used for improving the RC flexural members.

The optimized use of nanomaterials in concrete for developing resilient and eco-friendly infrastructure is vital for our built environment. Therefore, the current study aims to optimize the dosages and particle sizes of colloidal nano-silica in developing high-performance, sustainable cement mortar. For this purpose, compressive strength, water absorption, porosity, and microstructure tests were performed on mortars containing different dosages and particle sizes (NS80, NS250, NS250Al, NS500) of colloidal nano-silica. For comparison, tests were also performed on control mortars and mortars containing metakaolin and silica fume. The microstructure of cement pastes was examined through SEM-based BSE imaging with elemental mapping through EDS and FTIR analyses. Additionally, global warming potential (GWP) as well as embodied energy (EE) were also analyzed for all mortar mixtures. The results demonstrated that smaller nano-sized particles (NS500) at a lower dosage (3%) showed improved compressive strength and densified microstructure compared to all other mixes. However, larger nano-sized particles (NS80) at medium (5%) and high dosages (10%) had the highest impact on compressive strengths due to the formation of low and medium Ca-based C-S-H and C-A-S-H phases. Furthermore, the results of greater compressive strength of NS80 mortars under medium and high dosages were supported by their lowest water absorption and apparent porosity. When compared with the control and all other mixes, the mortar mixes containing medium and high doses of NS80 had lower embodied energy/MPa and CO2-eq intensity/MPa, indicating their significant contribution to producing green concrete with a lower environmental impact.

This article presents the effect of the cementitious material Silica Fume (SF) as a replacement binder with ordinary Portland cement (OPC) on the compressive strength of Green Ultra High Strength Concrete (GUHSC) containing Ultrafine Palm Oil Fuel Ash (UPOFA) at 28 and 90 days. UPOFA was utilized as a replacement binder by (0%, 25%, and 50%) of the cement mass in GUHSC production. While SF was replaced by (0%, 10%, 15%, 20%, and 25%) from the remaining cement mass. The Response Surface Method (RSM) was utilized for experiment design and statistical analysis of experimental results. Based on the results obtained, the compressive strengths of GUHSC were lost with a high UPOFA replacement level and gained back significantly by incorporating SF. The statistical findings from the ANOVA model using RSM analysis were empirically verified with an error less than 5%; thereby, the predicted and actual results were in acceptable agreement. Thus, using SF as a substitute binder significantly improved the compressive strength of GUHSC containing a high UPOFA volume. Thereby, SF could employ widening POFA utilization in green concrete production, which lessens environmental harm by reducing waste volume and intensive energy for cement production and somehow contributes to cost savings and concrete sustainability.

AbstractThis study aimed to investigate the feasibility and advantages of utilizing ternary blended binders consisting of Ordinary Portland Cement (OPC), Densified Silica Fume (DSF), and Ultrafine Palm Oil Fuel Ash (UPOFA) on the engineering and transport properties of Green High Strength Concrete (GHSC). A variable proportion of silica fume (5, 10, 15, and 20%) and up to 50% of UPOFA was incorporated as a partial replacement material from the total volume of cement binder into the GHSC. For fresh concrete, the results showed that the DSF inclusion increases water demand and reduces GHSC workability. Whereas for harden concrete, a considerable improvement in early strength and transport properties of GHSC with ternary binder inclusion. The highest relative strength was achieved at the early age of 1 day, which was up to 139.7% at 15%DSF content in (OPC-UPOFA-DSF15) GHSC. Meanwhile, the greatest improvement in the transport properties; water absorption, porosity, permeability and rapid chloride permeability of the GHSC was realized with 20% of DSF at 28 days in (OPC-UPOFA-DSF20) GHSC. Thus, in current study the results indicate that the combination of up to 65% (UPOFA and DSF) as a substitution binder with cement could produce GHSC with superior engineering and transport properties.

ABSTRACTThe paper reports the outcome of the research work on mechanical and microstructural changes to palm oil fuel ash engineered alkali-activated cementitious composite (POFA-EACC) mortar exposed to different levels elevated temperatures (300–900°C) for 2 h. POFA-EACC mortar utilised in the study was prepared from POFA activated with liquid sodium silicate and sodium hydroxide and reinforcement was provided by 2% volume fraction of polyvinyl alcohol fibres. The changes in the POFA-EACC mortar microstructure were investigated by means of SEM/EDS, XRD and FTIR. After exposure, the compressive strength of mortar specimens exposed to 300°C and 900°C temperatures for all alkali-activated ratios reduced while specimens exposed to 600°C temperature recorded improved strength for all AA ratios. The increase in strength of the specimens exposed to 600°C is due to the microstructural strengthening aided by post-heating solidification of the molten phase of the POFA-EACC mortar. The highly manifested changes in the phase composition were revealed in the POFA-EACC morphology and residual compressive strength after exposure.

The strength, pore structure, morphology and mineralogical composition of hydration products of natural pozzolan (NP) and nanosilica (nSiO2) based alkali activated binder (AAB) were examined. It was noted that AAB without nSiO2was relatively porous with the presence of micro-, meso- and macro-level pores. In contrast, as the proportion of nSiO2increased in the mixture, the pore structure started to refine with a reduction in the pore volume due to transformation of source material to polymeric compound, such as C-A-S-H with a higher Al absorption in the binder structure. The incorporation of 5% and 7.5% nSiO2resulted in the refinement of the pore structure due to enhanced polycondensation. Consequently, there was considerable improvement in the mechanical properties. The experimental data indicated that the pore structure evaluation through NMR has served as a tool to understand the relation between the micro- and macro-level performance of the developed AAC.

The objective of this study is to explore the feasibility of developing environmentally friendly green roller-compacted concrete (RCC) by utilizing locally available materials. The research investigates the behavior of RCC properties when different amounts of solid waste materials (brick powder, glass powder, and steel slag) are added as substitutes for cement content. To accomplish this, four laboratory tests were conducted: compressive strength, flexural strength, X-ray diffraction analysis, and scanning electron microscope imaging. These tests aimed to identify the changes in concrete properties resulting from the inclusion of waste construction materials as cement replacements. The study employed an approach that involved adding waste materials to the concrete mixture, with replacement percentages ranging from 10.0 to 40.0% in increments of 10.0%. Consequently, 12 concrete mixtures were prepared to examine the effects of adding waste materials (10.0–40.0%) as substitutes for cement content. In addition, one reference mixture was designed without any inclusion of waste materials for comparison purposes. In general, the results indicate that as the percentage of waste construction materials increases in the mixtures, there is a corresponding decrease in compressive strength. However, it is noteworthy that the strength activity index (SAI) exceeded 75% according to ASTM C618 standards. This indicates that the waste construction materials possess pozzolanic properties, making them suitable for use as cement replacements in RCC mixtures.

High-performance concrete is an excellent choice for modern engineering structures due to its superior performance, low maintenance costs, and long service life. Therefore, this study was aimed to produce high-performance concrete by incorporating a high volume of basaltic volcanic ash along with metakaolin (MK), micro-silica (MS), and nano-silica (NS). An investigation was performed in regard to the mechanical and durability properties, autogenous and drying shrinkage, and microstructural and pore-structure properties. A control mix, binary mixes, and ternary mixes were examined. The binary mixes contained fine (VA) and ultra-fine (VAF) volcanic ashes, and the ternary mixes contained combinations of VA with MK, MS, and NS. Test results show that ternary mixes with 30% and 40% cement substitution demonstrated better strength development and higher resistance to chloride penetration and water absorption. All binary and ternary mixes displayed lower autogenous shrinkage, as well as lower or comparable drying shrinkage than the control mix. Moreover, the combination of VA with MK, MS, and NS up to 40% resulted in micro and pore structure refinement by forming high-density gels. The findings indicate that VA in combination with MK, MS, and NS, can effectively substitute cement at up to 40% for the production of sustainable high-performance concrete.

As industrial globalisation and waste output continue to grow, solid waste management is one of the most pressing worldwide environmental challenges. Solid wastes include both the heterogeneous mass of urban throwaways and the homogeneous accumulations of agricultural, industrial, and mineral wastes. Clinical waste (CW) has a significant negative influence on both human health and the environment. To dispose hazardous CW, a proper waste management system should be necessary, and incineration should be the best possible option for reducing the volume of this hazardous waste. Incineration is being developed in Malaysia as a means of disposing clinical and hazardous waste. Currently, 170 common CW treatment facilities with 140 incinerators are accessible around the country. The combustion procedure kills pathogens and reduces waste volume and weight, but it leaves a solid residue known as clinical waste ash (CWA), which raises heavy metal, inorganic salt, and organic compound levels in the environment. Because metals are not eliminated during incineration, dumping CWA in a landfill could contaminate groundwater. Leachate is the liquid created when waste decomposes in a landfill and water filters through it. The most common method of disposing of CW ashes is to transfer them to a landfill. Landfills should install a top cover after closure for hazardous waste landfills. Due to a lack of space and the high expense of land disposal, recycling technologies and the reuse of ash in various systems have developed. Clinical waste incineration fly ash (CWIFA), a solid waste substance from CW incineration, typically includes mobile heavy metals and can cause significant pollution when reused. The standard requirement for removing CWIFA in dumpsites should be below the metal limit stated by the U.S. Environmental Protection Agency (USEPA). Much recent research on the usage of CWIFA has concentrated on mitigating their effects on the environment. Several studies have confirmed the utilisation of CWIFA in the construction field and agriculture to reduce the leaching of its hazardous components into the environment. Compressive strength decreased with the percentage amount of CWIFA due to the substitution of cement with CWIFA. CWIFA mix with 20% cement is the broad-scale application of CWIFA for geotechnical constructions. Heavy metals (Cd, Cu, Ni, Pb, and Zn) are strongly immobilised by the cementitious matrix. Solidification/stabilisation (S/S) materials can be dumped in landfills with less environmental protection than untreated waste. When utilising a CWIFA in mortar, the primary environmental concern is if any harmful materials leach out during the initial curing process or throughout the life of the mortar. Toxicity characteristic of leaching procedure (TCLP) analysis of all CWIFA specimens found amounts of heavy metals below regulatory limits. Solidification of waste with cement and solidified waste has become a popular way of minimising the atmosphere's emissions. The amount of CWIFA generated is expected to increase nationally and globally. There is an immediate need for further evaluation of ash leachate investigations for proper disposal and usage of ash in construction materials.