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In this study, the potency of volcanic pumice powder (VPP) as a supplementary cementitious material at varied levels (0%, 10%, 20%, and 30%) in high strength concrete (HSC) was investigated for its pozzolanic reactivity as a basis for strength and durability enhancement. Workability, transport properties and mechanical properties were tested in addition to the characterization of the products. X-ray florescence and strength activity index established the VPP oxides (SiO2 + Al2O3 + Fe2O3 = 76.01%) and pozzolanicity while diffraction techniques revealed the presence of anorthite (Al2CaO8Si2), and clinopyroxene (AlCaMgSiO6). Despite the paucity of calcium oxide and the excess of silica and alumina in VPP in contrast to OPC, yet it contributes significantly to the microstructural density and tortuosity of HSC pores thereby improving the strengths and transport properties as evidenced in the reduction of rapid chloride ions penetration (RCPT), and low initial surface (water) absorption (ISA) values. The maximum 180-day tensile, flexural and compressive strengths of the HSC-VPP sample were 6.22, 10.5 and 78.9 MPa, respectively. In this study, the potency of volcanic pumice powder (VPP) as a supplementary cementitious material at varied levels (0%, 10%, 20%, and 30%) in high strength concrete (HSC) was investigated for its pozzolanic reactivity as a basis for strength and durability enhancement. Workability, transport properties and mechanical properties were tested in addition to the characterization of the products. X-ray florescence and strength activity index established the VPP oxides (SiO2 + Al2O3 + Fe2O3 = 76.01%) and pozzolanicity while diffraction techniques revealed the presence of anorthite (Al2CaO8Si2), and clinopyroxene (AlCaMgSiO6). Despite the paucity of calcium oxide and the excess of silica and alumina in VPP in contrast to OPC, yet it contributes significantly to the microstructural density and tortuosity of HSC pores thereby improving the strengths and transport properties as evidenced in the reduction of rapid chloride ions penetration (RCPT), and low initial surface (water) absorption (ISA) values. The maximum 180-day tensile, flexural and compressive strengths of the HSC-VPP sample were 6.22, 10.5 and 78.9 MPa, respectively.

The urgent need to find green alternatives to cement concrete in order to reduce the consumption of fossil fuels and non-renewable resources that are used to produce cement. This research aims to study the possibility of using volcanic pumice dust (VPD) waste with cement kiln dust (CKD) or Ordinary Portland cement (OPC) to produce alkaline activated green concrete (HAC). VPD was used to improve the mechanical performance, strength, and engineering properties of HAC. CKD and OPC were used as a partial replacement for VPD in different proportions of 0, 5%, 10%, 20%, and 30% by weight. Na2SiO3 and NaOH were used as alkaline activator solutions to realize the alkaline reaction process in geopolymer paste. Workability, compressive strength, and engineering properties, such as bulk density, porosity, and water absorption, were studied. Results of this research indicated that increasing the replacement rates of CKD or OPC decreased slump flow but increased the strength of HAC and enhanced the values of its engineering properties. Geopolymer concrete with OPC and CKD as partial replacement of 30% by weight of VPD achieved an increase of 23% and 8%, respectively, in compressive strength at a test age of 90 days. Meanwhile, 20% VPD replacement by CKD achieved 11% higher compressive strength for the VPD–CKD samples compared with the control mixture. In addition, water absorption rate decreased by 25% and 20%, respectively, compared with the control samples.

The global sustainable construction aimed to minimize the ecological impacts of constructed facilities’ lifetime. In construction, concretes are the major materials utilized in South East Asia. Thus, it makes environmental and economic sense to utilize recycled materials in the production of new concretes for diverse uses. This review indicated that the practical implementations of the recycled aggregate concretes (RAC) in the area is greatly lacking, even though there are reasonable studies on RAC, particularly because of lack awareness and economic viability of such uses at the present period. This research aims to establish an interdisciplinary consortium with researchers, policy makers, practitioners, and social scientists in Southeast Asia to investigate the development of sustainable, durable, cost-effective, green concrete by utilizing recycled aggregates. Concentrating on waste resource recovery, this research presents an integrated modeling method. The approaches track and forecast a variety of values across technical, economic, social, and environmental areas linking these to the material flow and therefore integrating and building upon one-dimensional models like life cycle assessments (LCAs) and material flow analyses (MFAs). Additionally, the analysis of this study supported the recycling of cement for general use in construction, emphasizing the feasibility, reliability, and longevity of a project at the same time. However, the analysis also demonstrated that although there is fair progress on recycled concrete, there is still a severe lack of appropriate development in particular because of the lack of economic sustainability and knowledge of such applications at present. Raw material conservations were recorded; carbon dioxide costs and footprint were also reduced. Considering the RAC economic, technical, and environmental parameters, frameworks were applied for sustainable selections with target compressive strengths as the major goal.

Since diminishing the consumption of cement has many benefits, ongoing research on the incorporation of the industrial/agricultural wastes as an alternative or partial substitution for cement is of paramount significance. This study aims to examine the effect of steam curing regimes (SCRs) on the chloride resistance and microstructure of high-strength green concrete (HSGC). To this end, palm oil fuel ash, a type of waste from the palm oil industry, was treated so that ultrafine palm oil fuel ash (U-POFA) could be obtained. U-POFA was utilized as a partial substitute of the mass of cement at 0%, 20%, 40%, and 60% to produce HSGC. Varying steam curing temperatures (50 °C, 65 °C, and 80 °C) and varying periods (6, 11, and 16 h) were applied to the HSGC. Moreover, a steam curing cycle that did not exceed 24 h was applied. The tests performed on the HSGC samples included compressive strength (CS), rapid chloride permeability, and rapid chloride migration. The evaluation of the microstructure of the HSGC samples was undertaken via Mercury Intrusion Porosimetry (MIP) in addition to scanning electron microscopy with energy dispersive x-ray. The results showed that the application of SCRs with a high volume with UPOFA resulted in enhanced CS, chloride resistance, and microstructure properties of HSGC at an early age of 3 days and a later age of 360 days. Such enhancement in the concrete properties mainly depends on the cement replacement rates by U-POFA, temperature, and the steam curing period. It was, therefore, concluded that U-POFA played a key role in reducing the negative impact, which might have been caused by the utilization of varying SCRs. Since diminishing the consumption of cement has many benefits, ongoing research on the incorporation of the industrial/agricultural wastes as an alternative or partial substitution for cement is of paramount significance. This study aims to examine the effect of steam curing regimes (SCRs) on the chloride resistance and microstructure of high-strength green concrete (HSGC). To this end, palm oil fuel ash, a type of waste from the palm oil industry, was treated so that ultrafine palm oil fuel ash (U-POFA) could be obtained. U-POFA was utilized as a partial substitute of the mass of cement at 0%, 20%, 40%, and 60% to produce HSGC. Varying steam curing temperatures (50 °C, 65 °C, and 80 °C) and varying periods (6, 11, and 16 h) were applied to the HSGC. Moreover, a steam curing cycle that did not exceed 24 h was applied. The tests performed on the HSGC samples included compressive strength (CS), rapid chloride permeability, and rapid chloride migration. The evaluation of the microstructure of the HSGC samples was undertaken via Mercury Intrusion Porosimetry (MIP) in addition to scanning electron microscopy with energy dispersive x-ray. The results showed that the application of SCRs with a high volume with UPOFA resulted in enhanced CS, chloride resistance, and microstructure properties of HSGC at an early age of 3 days and a later age of 360 days. Such enhancement in the concrete properties mainly depends on the cement replacement rates by U-POFA, temperature, and the steam curing period. It was, therefore, concluded that U-POFA played a key role in reducing the negative impact, which might have been caused by the utilization of varying SCRs.

Recycled concrete aggregates (RCA) are used in existing green building composites to promote the environmental preservation of natural coarse aggregates (NCA). Besides, the use of RCA leads to potential solutions to the social and economic problems caused by concrete waste. It is found that insufficient information on the longevity and sustainability of RCA production is a serious issue that requires close attention due to its impact on changing aspects of the sector. However, more attention has been paid to explaining the effect of RCA on concrete durability, as well as the properties of fresh and hardened concrete. Therefore, this study aims to provide a critical review on the RCAs for the production of high-performances concrete structures. It begins by reviewing the source, originality, types, prediction of service life, features and properties of RCA, as well as the effect of RCA on concrete performance. In addition, this literature review summarizes the research findings to produce complete insights into the potential applications of RCA as raw, renewable, and sustainable building materials for producing greener concrete composite towards industrializing ecofriendly buildings today. Further, it has also highlighted the differences in the current state of knowledge between RCAs and NCAs, and offers several future research suggestions. Through this critical and analytical study, it can be said that RCA has the possible use in the production of high-performance structural concrete depending on the source and type of recycled aggregate while the RCA can be used widely and safely to produce traditional green concrete.

Worldwide consumption of cement must be reduced because of the serious pollution created from its manufacturing process. This study aims to solve this problem and assess efficiency of quarry dust of volcanic pumice as partial alternative to ordinary Portland cement. Investigations on the area of utilization of by-products from pumice industry with different granule sizes are still lacking. Thus, volcanic pumice dust (VPD) with three different VPD granule diameters of 64.1 (VPD60), 11.6 (VPD11), and 4.96 (VPD4) μm was used as 10%, 20%, and 30% partial replacement of cement mass. Flow, strength activity, compressive strength, water absorption, porosity, and initial surface absorption tests were performed to evaluate VPD efficiency at 7, 28, and 90 days. Results showed that the increase in VPD content in the mixtures increased flowability. Mixtures containing VPD4 demonstrated optimal results in strength activity index and compressive strength. The application of VPD as a partial substitute contributed to increasing concrete efficiency, absorption resistance, and porosity reduction in various mixtures. Thus, the results of this study indicated the possibility of using pumice quarry dust after a pass from a 150-μm sieve as a partial substitute to cement to improve workability and reduce the absorption and porosity of concrete.

The effect of partial replacement of coarse aggregate by plastic waste on the performance of concrete under impact three-point bending loading was investigated experimentally and numerically. Specimens were prepared for 5%, 10% and 20 % replacements by volume of coarse aggregate. For each case, three beams of 100 mm wide, 50 mm deep and 400 mm long were loaded to failure in a drop-weight impact machine by subjecting it to 30 N weight from 400 mm height, while another three beams of the same size were tested under static load. The load-displacement of beams of concrete with plastic waste subjected to static and impact loads were studied. The dynamic beam behaviour was also analysed numerically using the finite-element method (FEM) based LUSAS software. In general, the experimental results reveal that the impact tup, inertial load and bending load increase with the increase in the percentage of coarse aggregate replacement by plastic waste, while the static peak bending load always decreases. The concrete with plastic waste is stronger and more energy-absorbing under impact loading, than under static loading. The predicted load against displacement behaviours of both ordinary concrete and concrete with plastic waste, are well matched with the experimental results. The effect of partial replacement of coarse aggregate by plastic waste on the performance of concrete under impact three-point bending loading was investigated experimentally and numerically. Specimens were prepared for 5%, 10% and 20 % replacements by volume of coarse aggregate. For each case, three beams of 100 mm wide, 50 mm deep and 400 mm long were loaded to failure in a drop-weight impact machine by subjecting it to 30 N weight from 400 mm height, while another three beams of the same size were tested under static load. The load-displacement of beams of concrete with plastic waste subjected to static and impact loads were studied. The dynamic beam behaviour was also analysed numerically using the finite-element method (FEM) based LUSAS software. In general, the experimental results reveal that the impact tup, inertial load and bending load increase with the increase in the percentage of coarse aggregate replacement by plastic waste, while the static peak bending load always decreases. The concrete with plastic waste is stronger and more energy-absorbing under impact loading, than under static loading. The predicted load against displacement behaviours of both ordinary concrete and concrete with plastic waste, are well matched with the experimental results.

The environmental aspects of sustainable development in the construction industry consist of the utilization of secondary raw materials and materials which can be recycled in the design and construction of new structures. The preliminary and inevitable interest in the use of full or partial replacements of by-products as complementary pozzolanic materials was mostly induced by the enforcement of the reduction/elimination of the greenhouse gas emission from the production of Portland cement. With the significant evolution of geopolymer concrete as an alternative for Portland cement in the past decade, it is necessary to explore possible construction applications in which geopolymer concrete can be utilized. Hence, this review paper was carried out to explore various elements such as the precursors used in geopolymers concrete and their corresponding applications. The environmental impacts of various geopolymer concrete are also discussed. This paper also presents an overview of the real applications of geopolymer concrete for the construction of various infrastructures. Recommendations and prospects for geopolymer concrete are also provided. The environmental aspects of sustainable development in the construction industry consist of the utilization of secondary raw materials and materials which can be recycled in the design and construction of new structures. The preliminary and inevitable interest in the use of full or partial replacements of by-products as complementary pozzolanic materials was mostly induced by the enforcement of the reduction/elimination of the greenhouse gas emission from the production of Portland cement. With the significant evolution of geopolymer concrete as an alternative for Portland cement in the past decade, it is necessary to explore possible construction applications in which geopolymer concrete can be utilized. Hence, this review paper was carried out to explore various elements such as the precursors used in geopolymers concrete and their corresponding applications. The environmental impacts of various geopolymer concrete are also discussed. This paper also presents an overview of the real applications of geopolymer concrete for the construction of various infrastructures. Recommendations and prospects for geopolymer concrete are also provided.

The primary aim of this study is to examine the influence of incorporating volcanic pumice powder (VPP) and various steel fibers on the fracture toughness parameters of self-compacting concrete (SCC). Twenty-one notched SCCs with fiber (SCFs) beams and SCC beams (100 mm × 100 mm × 500 mm) are cast and then investigated via a three-point bending test. Five fiber types with different shapes and aspect ratios, namely, the hook-end fiber (60 and 30 mm), long straight fiber (21 and 13 mm), and flat-end fiber (six different concrete mixtures produced with the addition of 1% of the volume fraction), are examined. VPP is utilized at the replacement rate of 30% of cement mass. The other aim of the study is to examine the mechanical and fresh properties of concrete. Results show that steel fiber decreases the fresh properties of SCC. The inclusion of steel fiber leads to an increase in peak loads and deflection at the failure besides the mouth opening displacement of the crack. The parameters of fracture toughness of the concrete mixtures are also affected.

This study investigates the effect of curing regimes generally used for self-curing concretes (SC) on the engineering properties of normal strength concrete (NSC) and high-strength concrete (HSC). This study also examines the effect of exposing SC concrete to high temperatures up to 800 °C. This study applies five types of curing regimes. The first type is immersing concrete samples in a water tank. The second type is placing concrete samples in the air under lab conditions without curing. The third type is using different polyethylene glycol (PEG) doses by 1%, 2%, 3% and 4% of cement mass. The fourth type is using porous ceramic wastes aggregate (PCWA) as a course aggregate replacement by 10%, 15%, 20% and 25%. The fifth type is combining PEG doses by 1% and 2% with 10% of PCWA. Tests were conducted to investigate the mechanical properties of compressive, splitting, and flexural strength. The durability tests such as water absorption, water sorptivity, water permeability, chloride ion penetrability, carbonation depth and drying shrinkage were investigated. Weight loss and residual compressive strength tests were performed after exposure to high temperatures. The study recommends three self-curing regimes for NSC AND HSC based on a) compressive strength achieved, b) durability and c) mechanical and durability performance of concrete subjected to high temperatures. First: SC regime with a combination of 2% PEG and 10% PCWA achieved the maximum compressive strength of concrete that was reported to be 14.7% and 19.3% higher for NSC and HSC, respectively, compared to water immersion curing technique. Second: SC regime with a dose of 3% PEG (NCP3) achieved the optimum durability properties of NSC and HSC that were studied in this research. Third: SC regime, replacing coarse aggregate by PCWA up to 25%, that reduced the deleterious effects of high temperature on density loss and compressive strength. This study investigates the effect of curing regimes generally used for self-curing concretes (SC) on the engineering properties of normal strength concrete (NSC) and high-strength concrete (HSC). This study also examines the effect of exposing SC concrete to high temperatures up to 800 °C. This study applies five types of curing regimes. The first type is immersing concrete samples in a water tank. The second type is placing concrete samples in the air under lab conditions without curing. The third type is using different polyethylene glycol (PEG) doses by 1%, 2%, 3% and 4% of cement mass. The fourth type is using porous ceramic wastes aggregate (PCWA) as a course aggregate replacement by 10%, 15%, 20% and 25%. The fifth type is combining PEG doses by 1% and 2% with 10% of PCWA. Tests were conducted to investigate the mechanical properties of compressive, splitting, and flexural strength. The durability tests such as water absorption, water sorptivity, water permeability, chloride ion penetrability, carbonation depth and drying shrinkage were investigated. Weight loss and residual compressive strength tests were performed after exposure to high temperatures. The study recommends three self-curing regimes for NSC AND HSC based on a) compressive strength achieved, b) durability and c) mechanical and durability performance of concrete subjected to high temperatures. First: SC regime with a combination of 2% PEG and 10% PCWA achieved the maximum compressive strength of concrete that was reported to be 14.7% and 19.3% higher for NSC and HSC, respectively, compared to water immersion curing technique. Second: SC regime with a dose of 3% PEG (NCP3) achieved the optimum durability properties of NSC and HSC that were studied in this research. Third: SC regime, replacing coarse aggregate by PCWA up to 25%, that reduced the deleterious effects of high temperature on density loss and compressive strength.

Palm oil fuel ash (POFA) was utilized as a pozzolanic material in varied quantities to produce high-strength concretes (HSC x ) of above 90 MPa, with significant improvement in its engineering and fluid transport properties. The chemical and physical characteristics of ultrafine POFA (U-POFA) utilized in HSC x were investigated along with its concomitant fresh, strength and durability characteristics compared to ordinary Portland cement based type (OPC-HSC). The U-POFA had high surface area of (1.136 m 2 /g-Blaine), mean particle size (2.06 μm), and glassy phase (70.59%). The HSC x that had replacement level of 0, 20, 40 and 60% of U-POFA recorded the 90-day strength of 100.5, 105.2, 109.0 and 108.5 MPa. Utilizing high volume of POFA in HSC x is possible with improved fineness and heat-treatment at 500 ± 50 °C, and could retard water absorption/permeability, setting and chloride penetration/migration rates and achieve better strength. This makes HSC x a better choice in terms of strength and durability for hot weather and underwater concreting, and in corrosive or aggressive environment.

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 116 MPa. The treatment of ground POFA (GPOFA) to produce ultrafine or treated POFA (UPOFA) changed its fineness, unburned carbon composition and percentage of pozzolanic minerals (SiO 2 + Al 2 O 3 + Fe 2 O 3 ) and led to the production of high strength concrete dubbed HSCg and HSCu, respectively. The characteristics of HSC u indicated UPOFA positive contributions towards workability, strength and permeability (gas and water, chloride penetration and migrations). At the age of 180 days, HSC u containing 20, 40 and 60% of UPOFA resulted in the compressive strength of 108.6, 114.4 and 112.4 MPa, respectively as against the maximum of 106.5 MPa and 105.1 MPa 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.

This research investigates the possibility of grinding and burning bivalve clam seashells to produce seashell ash powder. This ash is used to partially replace cement by 5, 10, 15 and 20% by weight. These mixes are tested and compared with a SC0 that has 0% seashell ash powder (SC0). The fresh and hardened properties of all mixes are studied through a variety of tests, including: slump, unit weight, compressive strength and splitting tensile strength. The durability of seashell concrete cubic specimens is studied by immersion in 5% NaOH(aq) and MgSO4(aq) solutions. The addition of thermally treated seashells increased the calcium hydroxide content. The results also show that the compressive strength of the 5% replacement is slightly higher than the SC0 at 28 and 90 days of age, while the tensile strength is higher than the standard for the 5% and 10% of replacement at 7 and 28 days. Furthermore, the slump test value generally increases with increasing the percentage of replacement. The highest durability against sulfate and alkaline attacks is obtained with 5% replacement of cement with seashells which reported the lowest decrease in weight and the highest compressive strength after immersion in 5% NaOH(aq) and MgSO4(aq) solutions. The 5% replacement mix is the optimum percentage of replacement. Therefore, this study recommends replacing cement with 5% seashell cement. This research investigates the possibility of grinding and burning bivalve clam seashells to produce seashell ash powder. This ash is used to partially replace cement by 5, 10, 15 and 20% by weight. These mixes are tested and compared with a SC0 that has 0% seashell ash powder (SC0). The fresh and hardened properties of all mixes are studied through a variety of tests, including: slump, unit weight, compressive strength and splitting tensile strength. The durability of seashell concrete cubic specimens is studied by immersion in 5% NaOH(aq) and MgSO4(aq) solutions. The addition of thermally treated seashells increased the calcium hydroxide content. The results also show that the compressive strength of the 5% replacement is slightly higher than the SC0 at 28 and 90 days of age, while the tensile strength is higher than the standard for the 5% and 10% of replacement at 7 and 28 days. Furthermore, the slump test value generally increases with increasing the percentage of replacement. The highest durability against sulfate and alkaline attacks is obtained with 5% replacement of cement with seashells which reported the lowest decrease in weight and the highest compressive strength after immersion in 5% NaOH(aq) and MgSO4(aq) solutions. The 5% replacement mix is the optimum percentage of replacement. Therefore, this study recommends replacing cement with 5% seashell cement.

Introduction: Palm oil fuel ash in two various forms-ground (GPOFA) by heat-treated carbon-free ultrafine of a median particle size of 2 μm (UPOFA) were utilized to produce high strength concretes (HSC-GPOFA (HSCgx), HSC-UPOFA (HSCux), and HSC-OPC) at different levels ordinary Portland cement (OPC) partial replacements (x) of 20, 40 and 60%. Methods: The workability (slump, slump loss, and compacting factor), initial and final setting times and strength in both forms of concrete were investigated. Results and Conclusion: The results showed that HSCu had improved physical properties and chemical compositions, extended setting times, enhanced workability, better strength, and enhanced workability retention compared to HSCg and HSC-OPC. Further, POFA carbon content negatively influenced the workability and setting time, while its specific gravity had a positive influence due to the enhancement of paste volume and particles lubrication effects. However, carbon content and surface areas of POFA did not significantly influence the compressive strength of HSC at the level of partial OPC substitution not exceeding 40%.

The performance of any repaired concrete structure, and thus its service life, depends on the quality of the interfacial transition zone of the composite system formed by the repair material and the existing concrete substrate. In this work, the properties of the interfacial transition zone between normal concrete (NC) substrate as an old concrete and ultra-high performance fiber-reinforced concrete (UHPFC) as a repair material was investigated. Pull-off and splitting cylinder tensile tests were performed to quantify the bond strength in direct and indirect tensions, respectively. The microstructure of the interfacial transition zone was also studied using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDS). Different types of NC substrate surface preparation methods were used. An optical three-dimensional surface metrology device was used to estimate the substrate roughness parameters. Based on the results, high interfacial bond strength was achieved on the 3rd, 7th, and 28th ...

Ground treated ultrafine-POFA obtained from palm oil industry was heat-treated to remove excess carbon. The varied proportion (17%, 30% and 40%) of UPOFA was incorporated into the ultra-high strength concrete (UHSC) to study its effects on the UPOFA-UHSC (Ux-UHSC) in comparison with OPC-UHSC (U0-UHSC) engineering and transport prop- erties. The Ux-UHSC has an increasing workability tendency with a retarded setting times as compared to U0-UHSC. Besides, Ux-UHSC registered higher compressive strength than the U0-UHSC. The 90-d strength of 156 MPa was achieved in U17-UHSC which was 4.7%, 7.5% and 12.2% higher than the values obtained for U30-UHSC, U40-UHSC and U0-UHSC, respectively. The U40-UHSC exhibited the greatest improvement at 90 days in transport properties such as porosity, water absorption, initial surface absorption, rapid chloride permeability, gas permeability and water perme- ability while the highest strength was recorded with U17-UHSC. Thus, the pozzolanic UPOFA is capable of improving the engineering and transport properties of UHSC.

The concrete industry has a plethora of negative impacts on the globe and environment. Also, with the depletion of natural resources that are used in concrete and cement production, many research attempts are focused on finding alternatives or incorporating waste materials into concrete mixes. Seashells are some of these waste materials that are rapidly accumulating on seashores and landfills, causing an environmental problem of their own. This review paper is focused on the utilization of various types of seashell waste materials in concrete as partial cement replacement. The utilization of seashells in concrete helps in seashell waste management and in producing cost-efficient concrete. The paper summarizes the previous research attempts to produce burnt seashell to partially replace cement in different proportions. It also presents the physical and mechanical properties of seashell ash and the produced concrete. The literature review has justified the use of seashell waste ashes for cement partial replacement in sustainable concrete. The study shows that incorporating seashell ash resulted in reduced early compressive strength of concrete. The strength increased with age due to hydration of calcium oxide, but it remained less than control samples, especially at high percentages of replacement. The flexural and splitting tensile strength was improved due to the development of good bonding between the binder matrix and aggregates and this increased the modulus of elasticity. However, some studies reported a decrease in splitting tensile strength. The absorption and porosity of concrete at low percentages of replacement are less than the standard. However, these values are increased with higher levels of replacement. Seashell ash generally reduces workability. The ash also reduces concrete permeability after long periods of curing. It can be established that there is a possibility for incorporating seashell in concrete as a binder material for sustainable construction purposes. The concrete industry has a plethora of negative impacts on the globe and environment. Also, with the depletion of natural resources that are used in concrete and cement production, many research attempts are focused on finding alternatives or incorporating waste materials into concrete mixes. Seashells are some of these waste materials that are rapidly accumulating on seashores and landfills, causing an environmental problem of their own. This review paper is focused on the utilization of various types of seashell waste materials in concrete as partial cement replacement. The utilization of seashells in concrete helps in seashell waste management and in producing cost-efficient concrete. The paper summarizes the previous research attempts to produce burnt seashell to partially replace cement in different proportions. It also presents the physical and mechanical properties of seashell ash and the produced concrete. The literature review has justified the use of seashell waste ashes for cement partial replacement in sustainable concrete. The study shows that incorporating seashell ash resulted in reduced early compressive strength of concrete. The strength increased with age due to hydration of calcium oxide, but it remained less than control samples, especially at high percentages of replacement. The flexural and splitting tensile strength was improved due to the development of good bonding between the binder matrix and aggregates and this increased the modulus of elasticity. However, some studies reported a decrease in splitting tensile strength. The absorption and porosity of concrete at low percentages of replacement are less than the standard. However, these values are increased with higher levels of replacement. Seashell ash generally reduces workability. The ash also reduces concrete permeability after long periods of curing. It can be established that there is a possibility for incorporating seashell in concrete as a binder material for sustainable construction purposes.

Palm oil fuel ash obtained from palm oil mill was treated via screening, grinding and heating to improve its pozzolanic reactivity. The characteristics of the palm oil fuel ash before and after treatment were monitored to assess the changes in the properties of the palm oil fuel ash. The resulting ultrafine palm oil fuel ash was then utilized to produce high strength concrete by replacing the ordinary Portland cement at 0, 20, 40 and 60% on mass-for-mass basis. The results show that the treatment process undertaken reduces the particle size, diminishes the unburned carbon content, while at the same time increases the glassy phases. The utilization of the ultrafine palm oil fuel ash in high strength concrete was observed to improve workability especially at higher ultrafine palm oil fuel ash content. In addition, the long-term compressive strength of the high strength concrete was significantly increased with the ultrafine palm oil fuel ash inclusion. Further, the long-term rapid chloride permeability was significant reduced especially at higher ultrafine palm oil fuel ash content of 60%, which could be translated into superior durability performance.

Palm oil fuel ash (POFA) was used to produce engineered cementitious composite (ECC) in this research where ECC mixtures containing different volume of POFA (up to 55% by weight) of cement, were prepared. Mechanical properties of the resulting ECC mixtures were assessed using the compression, flexural and uniaxial tensile tests. The findings of the study show that the use of POFA improves the mechanical properties of the ECCs. The ECC mix with 1.2 POFA/cement ratio achieved a compressive strength of 30 MPa at 28 days, which is within the normal range of concrete strength for many applications. Moreover, the results portray that the use of POFA should be helpful for achieving strain-hardening behaviour. The increase in the POFA content concomitantly increased the flexural deflection and tensile strain capacities of the POFA-ECC. Furthermore, crack width of the ECC was significantly decreased with an increase of POFA content. In addition, the resulting POFA-ECC is expected to enhance the material greenness and durability.

The weak interfacial transition zone between new and old concrete is always paid much attention and controls many properties of repaired concrete, The present work reports a study on the influence of the silica fume on the adhesion of reactive powder concrete (RPC), as a concrete restoration material, with the ordinary concrete (OC) substrate. The results showed that, the silica fume presence in the interfacial transition zone significantly enhances the adhesion strength between RPC and OC substrate. Furthermore, the silica fume particles consume calcium hydroxide, which is in attendance in the interfacial transition zone, and make the zone more dense, uniform and tough.

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 2 μm. 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 7 days, but enhances the strength at 28 days for all HSGCs containing POFA, where strength exceeding 95 MPa 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 28 days. 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.