Search

A 14-week study was conducted to examine the dietary effects of Saccharomyces cerevisiae on growth performance, hematological response and, resistance of Oreochromis niloticus juveniles to Aeromonas hydrophila as a pathogenic organism. The study had 5 treatments and 3 replicates in a complete randomized design. The growth study which was run for 12 weeks, with the fish fed twice per day at 3% body weight. The experimental diets contained Saccharomyces cerevisiae at 0, 20, 25, 30 and 35 ml/kg, represented as T1 (control diet), T2, T3, T4 and T5, respectively. The study had growth parameters monitored, after which the fish were challenged with Aeromonas hydrophila through intramuscular injection and, kept for another 2 weeks to monitor the clinical signs and the mortality rate. The study revealed that diet T5 supported better fish growth and survival rates. All the challenged fish were sluggish after being challenged. The highest relative percentage survival was obtained in treatments T4 and T5, while T1, T2 and T3 had the least relative percentage survival. Higher values of hemoglobin packed cell volume, red blood cell, and white blood cells were recorded in the treated diets with the highest recorded in T5, while the least was obtained in T1. In conclusion, diet T5 was observed to support growth rate, improved blood constituents and increased the resistance of Nile Tilapia exposed to Aeromonas hydrophila. Therefore, diet containing S. cerevisiae at 35 ml/kg could be recommended to the fish farmers for the production of disease resistant and fast growth Oreochromis niloticus.

A comprehensive review of the durability and microstructural properties of alkali-activated materials (AAMs) made with waste glass as a precursor is presented in this paper. AAMs are potentially sustainable alternatives that can be utilized to replace Portland cement (PC) materials due to the total elimination of PC as the binder. The traditional precursors utilized in the production of AAMs are fly ash and slag. However, other waste products such as glass powder (GP) can be applied as a precursor in the production of AAMs. Due to the limited research and application of waste glass as a precursor in AAMs, a thorough analysis was made to investigate current studies where the durability and microstructural characteristics of AAMs made with waste glass were evaluated. The durability properties explored are permeability properties, shrinkage, alkali-silica reaction and resistance to aggressive environments. Microstructural properties discussions were also made to support the corresponding physical properties of GP-based AAMs.

The evolution of sustainable binders for various construction applications has resulted in the development of various geopolymer binders using various materials as aluminosilicate precursors. Geopolymer binders can be utilized as an alternative to Portland cement in the production of various materials such as mortar and concrete. In this study, geopolymer binders were synthesized using metakaolin (MK) and meta-halloysite (MH) as the aluminosilicate precursors and activated with an alkali solution having a silica modulus of 1.3 and 1.5. The resulting geopolymer binders were assessed in terms of the mechanical, permeability and durability properties. The findings from this study showed that the use of MH as the precursor resulted in better performance compared to when MK was used due to its higher reactivity and fineness. It was also found out that the use of a silica modulus of 1.5 is favourable to the hardened properties of the geopolymer binders. Geopolymer binders synthesized with MH and an activator with a silica modulus of 1.5 exhibited an increase in compressive and flexural strength of approximately 9 MPa and 1 MPa, respectively compared to when a silica modulus of 1.3 was used. Also, the corresponding porosity and water absorption is 14.5% and 10.9%, respectively lower.

The significant sustainability awareness in the construction industry coupled with the need for the industry to reduce its negative environmental impacts has resulted in the use of various ‎industrial wastes in construction ‎applications such as in the production of concrete. Various industrial wastes can be utilized as ‎partial or total replacements for some components in concrete. Such industrial waste that ‎can be utilized as fine aggregate in the production of concrete is coal bottom ash (CBA). Various studies have utilized CBA as fine aggregate in various types of concrete including high-strength concrete and there has been significant interest in the continuous use of CBA in concrete. To propel more application of CBA in various concrete types and to increase the understanding of the effect of the CBA on the properties of concrete, this comprehensive review was carried out. The properties explored are fresh, mechanical, durability and microstructural properties of concrete incorporating varying proportions of CBA. Findings from the existing studies indicate there exists a significant variation in the impact of CBA on the properties of various concretes. Nonetheless, numerous studies showed that CBA can be utilized as a sustainable alternative to the conventional natural fine aggregates to produce normal and high-strength concrete. Hence, this study recommends carrying out additional studies in this area to evaluate the effect of the physical and chemical properties of CBA on the resulting properties of concrete.‎

Alkali-activated materials (AAMs) are promising materials that can be used as alternatives for conventional Portland cement (PC) materials. In this paper, the fresh properties, and mechanical properties of AAMs made with glass powder (GP) as the precursor were explored and discussed. The discussions presented in this paper showed that the incorporation of GP as the precursor in AAMs resulted in an improvement in the workability and extension of the set times. However, the use of GP especially at early ages could result in a detrimental impact on the mechanical performance of AAMs due to the lower reactivity of GP compared to other precursors. Nonetheless, AAMs with acceptable mechanical performance for non-structural and structural applications can still be produced with the use of GP as the precursor.

Brazil is a country of continental dimensions and characteristics with enormous biodiversity of fauna and flora which confers a prominent role in the sector of extraction of agricultural products. However, one of the current challenges is the increasing amounts of agricultural solid wastes generated by different local production processes which end up resulting in enormous environmental liabilities. One way to effectively manage these agro-industrial wastes is by their application in the development of alternative cementitious materials such as mortars and concretes. Thus, the objective of this paper is to discuss the recent advances, challenges and future perspective of the application of some solid agro-industrial wastes generated specifically in Brazil and some other parts of the world in cementitious materials. The application of wastes from pineapple, sugar cane, açai, coconut and rice were explored and discussed. The discussion presented in this paper is anticipated to strongly contribute to the advancement of public policies that enable the real application of these wastes in the development of eco-friendly cementitious materials for civil construction.

Steam curing at atmospheric pressure is a method used to raise concrete strength at early ages. The steam curing method is based on the application of hot water vapor at a temperature between 40 °C and 100 °C for a limited period. The highest temperatures and the longest curing period are determined based on the characteristics of the target concrete, the cost, and the production cycle. This study presents the effect of steam curing regime application on concrete properties. Steam curing has a negative effect on the microstructure of concrete, and this effect increases with higher temperatures. The curing period and the precuring period in addition to the cooling period influence the properties and the strength of concrete. This study summarizes the previous literature related to the effect of steam curing regime application on the properties of concrete. Previous studies confirm that concrete exposed to steam curing regime at low temperatures ranging between 45 °C and 80 °C and a longer period within a 24-hour cycle achieve better concrete properties. In addition, raising the steam curing temperatures above 80 °C has a negative effect on concrete microstructure and other concrete properties in general. This study also concludes that adding pozzolanic or complementary cement materials contributes to reducing the damage resulting from the application of steam curing regime on concrete at later ages. Such verification is required to clarify the behavior of concrete under the influence of steam curing systems, understand their effect on the properties of concrete, and look for ways to reduce the damage from degrees of application of steam curing regime.

This study presents the results from the microbiological induction of bacterial biomass (i.e. biocementation) in concrete mixtures to enhance the mechanical and durability properties. Bacteria isolated from manufactured sand (i.e. bacillus megaterium) were incorporated into concrete mixtures and the corresponding effects on the mechanical and durability properties were investigated. The influence of the bacteria concentration was assessed in terms of compressive strength, split tensile strength, flexural strength, acid resistance, chloride ion penetration and water permeability. In addition, microstructural investigations were also carried out. Findings from this study indicated that the compressive strength, split tensile strength and flexural strength of concrete made with 105 cells/ml of bacteria is 11.3%, 97.5% and 10.7%, respectively. Similarly, concrete made with 105 cells/ml of bacteria exhibited lower permeability (i.e. lower chloride ion penetration and water permeability) and higher resistance to acid attack compared to the plain concrete without any induced bacteria. The improvement in the properties of the concrete with the incorporation of bacillus megaterium was associated with the precipitation of calcite and the presence of bacterial biomass within the pores of the concrete matrix. Microstructural investigations also showed that concretes made with bacteria at a concentration of 105 cells/ml have more calcite formation as evident in the scanning electron microscopy images and elemental composition of the concrete. Hence, it was concluded that the use of the bacillus megaterium at a concentration of 105 cells/ml is optimum to achieve enhanced performance of the concrete.

The development and application of fibre-reinforced cementitious composites (FRCC) have evolved significantly over the last decade. However, there is a need to find innovative ways to improve the sustainability of composites. The production and transportation of the major binder (i.e. Portland cement) and aggregates used for FRCC consumes high energy and natural resources. Therefore, finding ways to incorporate recycled materials to replace these conventional components can be used to improve the sustainability of the FRCC. Also, the special micro silica sand used to produce certain types of FRCC is a major concern due to its limited availability and higher cost. On the other hand, there exist various waste materials that can be incorporated into FRCC as a replacement of either the binder or aggregate. Hence this current paper aims to investigate the performance of FRCC made with high volume fly ash as partial replacement of Portland cement, and reclaimed asphalt pavement/crumb rubber as replacement of the natural aggregates. The performance of the FRCC incorporating these recycled materials was evaluated in terms of its crack properties, toughness and sorption. Results from this study showed that the use of recycled crumb rubber is beneficial in terms of crack properties and lower sorption. The sorption of FRCC incorporating crumb rubber as the only aggregate was reduced by 31.8%. However, FRCC made with reclaimed asphalt pavement exhibited higher sorption and lower toughness.

In this study, an ecofriendly binder was developed by using rice husk ash (RHA) and sodium hydroxide as the activator alongside fly ash (FA) as the aluminosilicate precursor at ambient conditions. The developed binder was used in the production of mortars with varying proportions of sand. A total of three mortar mixtures were developed with sand to binder ratios of 0.55, 0.83 and 1.11. The corresponding behaviour of the mortars and influence of the sand proportions was assessed in terms of the compressive strength, water absorption, density, porosity. Microstructural investigations such as scanning electron microscopy, energy dispersive x-ray spectroscopy, infrared spectrum analysis and mercury intrusion porosimetry were also used to validate the physical properties. The findings from this study demonstrated that RHA can be used successfully as an activator component in the production of mortars. In terms of the sand content, it was found out that increasing the sand to binder ratio has detrimental effects on the performance of the mortars due to the reduction in the binder content primarily. The microstructure analysis of the mortars made with sand to binder ratio of 0.55 showed a compact and strong structure justifying the higher compressive strength achieved. The MIP analysis confirmed that the formation of C-A-S-H gel at the advanced ages allowed the pores refinement with a significant decrease in the fraction of the capillary and macroscopic pores within the geopolymer mortars.

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.

In this study, sugarcane bagasse fibres (SBF) were used as a sustainable alternative to reinforce laterite-based geopolymers. As geopolymers can be deemed an eco-friendly construction material, the sustainability of geopolymers can be further improved with the use of SBF which is an agricultural by-product as reinforcement. In addition, the use of natural fibres has been known to improve insulation properties resulting in more energy conservation when such materials reinforced with natural fibres are used for the construction of building elements. Thus, the influence of SBF at various dosages (i.e. 1.5%, 3%, 4.5%, 6% and 7.5%) on the properties of laterite-based geopolymer was evaluated in this study. The outcome of this study indicated that incorporating SBF into the laterite-based geopolymers resulted in a decrease in density and increase in the sonic rate which is beneficial to the acoustic and thermal insulation enhancement. In addition, it was found out that the use of SBF at a dosage of 3% improved the resistance of the geopolymers to wet-dry cycles. However, the presence of SBF in the geopolymers resulted in a decrease in the compressive strength and an increase in the permeability properties with higher content of SBF.

The detrimental impact of Portland cement (PC) which is the primary binder in the production of cementitious materials such as concrete has called for a need to use alternative binders to produce concrete. Of such promising sustainable alternative to the conventional PC concrete (PCC) are alkali-activated concrete (AACs) which are produced by using a binder composed of an aluminosilicate precursor and alkali activator. In this study, blast furnace slag (BFS) was used as the primary precursors in the production of AACs. Amorphous raw rice husk ash (RRHA) was used at various dosages to partially replace BFS as the precursor. The corresponding influence of the RRHA content and curing conditions on the performance of AACs were evaluated. The two curing conditions utilized are ambient temperature curing and thermal curing for 24 h at 60 °C followed by ambient temperature curing. Findings from this study showed that the use of RRHA as a 10% replacement of the BFS is optimum as it yielded enhanced mechanical and durability performance. It was also found out that the thermal curing of AACs for 24 h before curing at ambient temperature is beneficial to improving the performance.

The type of aluminosilicate precursor used in the synthesis of geopolymer binders plays a huge role in the resulting performance. Thus, it is critical to understand the properties of precursors and how they influence the corresponding performance of geopolymer binders. In this study, metakaolin and meta halloysite are used as the aluminosilicate precursor in the synthesis of geopolymer binders. These precursors are obtained locally in order to propel the sustainable development and application of geopolymers. The precursors were characterized and the corresponding influence on the reactivity, rheology and setting times of geopolymers was investigated. In addition to the influence of precursor type on the properties of the geopolymers, the effect of two silica moduli (i.e. 1.3 and 1.5) was also evaluated. The results from this study indicated that increasing the activator silica modulus from 1.3 to 1.5 extended the setting times and increased the stress strain of the geopolymer binders. Characterization of the precursors indicated that metakaolin has a higher amorphous content compared to that of meta halloysite. However, the finer particles of meta halloysite embodied it with the ability to participate in a faster geopolymerization and result in more formation of activation products.

Generally, the absence of coarse aggregate coupled with high binder content in engineered cementitious composites (ECC) mixtures subjects it to high shrinkage despite the presence of fibres. The weak interfacial bond between the fibres and cementitious matrix at early ages results in the ineffectiveness of these fibres to provide restraint in the matrix. On the other hand, there is an imminent need to find alternative aggregate to the conventional aggregate used for ECC mixtures due to its limited supply, high cost and high embodied carbon as a result of its transportation. Recent studies have shown that glass aggregates can be used in ECC mixtures without any detrimental effect on mechanical properties. However, the effects of the glass aggregates on the shrinkage properties of the ECC mixtures are unknown. Therefore, this study was carried out to investigate the shrinkage properties of ECC mixtures made with glass aggregates as the replacement of ultrafine silica sand up to 100%. A total of five mixtures with varying content of glass aggregates were made and the corresponding autogenous, drying and plastic shrinkage was evaluated. Results from this study showed that the use of glass aggregates in ECC mixtures led to a decrease in the shrinkage of the mixtures as the glass aggregate content increases. It is also shown that glass aggregate can be used as a total replacement of the ultrafine silica sand without any detrimental effect on the shrinkage properties of ECC mixtures.

This paper present the results from a comprehensive study undertaken to investigate and develop alkali-activated binders (AABs) with laterite soil as the aluminosilicate precursor. In this study, the effect of the silica modulus (SiO2/Na2O) of the activator on the setting time, rheological properties and strength development were investigated. Iron-rich laterite sourced from West Africa was used as the aluminosilicate precursor alongside sodium silicate and sodium hydroxide for the production of the activator. The activators were prepared to have varying silica modulus of 1.3, 1.5, 1.7 and 2. The findings from this study showed that the silica modulus of the activator used in the synthesis of the laterite-based AABs has a significant influence on the resulting properties of the binders. It was found out the optimum silica modulus is 1.3 and increasing the silica modulus of the activator results in detrimental effects on the hardened properties of the AABs. In the same context, increasing the silica modulus of the activator from 1.3 to 2.0 extended the final setting of the binder time by 56.1% while the compressive strength at 56 days reduced by 57%. Microstructural investigation on the binders showed that the main products of alkali activation of the calcined laterite are quartz, ilmenite, hematite and maghemite. It was concluded that laterite-based AABs with good performance can be produced with a silica modulus of 1.3 and used as a possible alternative for Portland cement as a binder.

The high energy consumption by buildings has called for a need to use energy-efficient material for future construction applications. Cementitious composites in various forms are the most used building material for the construction of buildings. Therefore, in order to ensure these buildings made with cementitious composites are energy-efficient, it is imperative to find innovative and sustainable ways to improve the thermal properties of these cementitious composites. One of the sustainable and effective ways to improve the thermal properties of cementitious composites is with the incorporation of various waste. Therefore, this paper aims to discuss different types of wastes that can be recycled into cementitious composites to improve the thermal properties (i.e. reduce thermal conductivity) based on existing experimental studies. Discussion from this paper showed that recycled materials such as rubber and plastics can be used to reduce the thermal conductivity of cementitious composites when used as a replacement of up to 50% of natural aggregates. It was also concluded that there is a good relationship between density and thermal conductivity of cementitious composites and waste/recycled materials can be incorporated as aggregate/filler in cementitious composites to improve the thermal performance. However, there is a need for the limitations associated with the use of these waste/recycled materials to be resolved before they are incorporated into cementitious composites.

The production of Portland cement (PC) which is the main binder in conventional cementitious materials contributes about 7% to the world’s anthropogenic carbon dioxide emission. As the demand for PC is expected to increase significantly in the coming years, it is imperative to find other environmentally friendly alternatives. Alkali-activated binders (AABs) obtained by alkali activation of aluminosilicate precursors are viable alternatives for PC as they possess lower embodied carbon and energy compared to PC. However, the conventional activators (i.e. sodium silicate and sodium hydroxide) are corrosive, expensive and have a high environmental footprint. These limitations have resulted in impractical and expensive applications of such binders on a large scale. On the other hand, sodium carbonate, which is less corrosive, cheaper and available naturally in the environment can be used as a sustainable alternative to sodium silicate and sodium hydroxide. In a quest to propel the application of sustainable binders, this study was undertaken to explore the properties of slag activated with sodium carbonate at ambient temperature. The effect of sodium carbonate dosage on the fresh, mechanical and durability properties are discussed. A simplified sustainability assessment of concrete made with different binders was also carried out and the results showed that the sodium carbonate activated slag concretes are a sustainable alternative to PC concrete to achieve a cleaner environment.

Increasing sustainability awareness has put the concrete industry in the spotlight to reduce its carbon dioxide emissions. Most of the carbon dioxide emission from the concrete industry is from the production of Portland cement which is the main binder in concrete, and the transportation of materials. Also, the production of other components in concrete such as aggregates, admixtures, and construction processes contribute to the industry's emission. In addition, the concrete industry is one of the major consumers of natural resources, and the increasing production of concrete has posed a huge strain on the natural reserve of these resources. Nevertheless, the last decade has seen several promising initiatives taken by the industry to improve its sustainability in order to achieve a net-zero emission by 2050. These initiatives vary from using alternative materials such as waste materials, optimizing concrete production processes, use of alternative sources of energy, etc. In order to create more awareness within the construction industry and its stakeholders, this paper explored various ways in which the industry is tackling these sustainability issues. The prospects alongside the challenges for these initiatives are discussed.

Cenospheres are waste products generated from the production of power from coal combustions. These wastes can be incorporated into cementitious materials to produce lightweight materials. In addition, the incorporation of these wastes can be used to improve the thermal and acoustic properties of cementitious materials. However, the incorporation of these cenospheres alters other properties. Hence, it is critical to understand how the incorporation of cenospheres into cementitious composites affects various properties. This paper presents a critical review of the properties of cementitious materials incorporating cenospheres. A brief discussion on the source, physical properties and chemical properties of cenospheres were first made. The effect of cenospheres on the physical, mechanical and durability was also discussed. The discussion made in this paper showed that the cenospheres can be incorporated into cementitious materials to produce lightweight materials and enhance the thermal and acoustic properties.

A state-of-the-art review of advances in alkali activated slag (AAS) with respect to its behaviour is presented. The need for sustainable development of AAS, and factors that affect the fresh and hardened properties of AAS based composites were discussed. The fresh properties of AAS reviewed include flow, setting times and heat of hydration. While the hardened properties considered were compressive strength, shrinkage, and microstructure. Major limitation of using AAS and possible solutions were also highlighted. Overall, various studies showed that large scale application and commercialization of AAS is imminent in the coming years, as AAS is capable of exhibiting similar/higher properties compared to that of Ordinary Portland Cement (OPC). In addition, the viewpoint of this review will be useful for contractors and researchers to have more understanding about AAS. Grey areas for possible research exploit were also identified. Keywords: Alkali activated slag, Durability, Geopolymer, Hydration, Slag activator, Sustainability

As the global effort to eradicate hepatitis B continues, immune escape mutations (IEMs) and drug resistance mutations (DRMs) affecting its diagnosis, treatment, and prevention are compromising this goal. However, knowledge about the prevalence and circulation of these mutations in Nigeria is scarce. Serum samples (n = 199) from apparently healthy prospective blood donors, pregnant women, and individuals presenting with fever in southwestern Nigeria were analyzed for the presence of IEMs and DRMs by means of nested PCR in the HBV S (HBs) and HBV polymerase (Pol) genes, followed by phylogenetic and mutational analyses. In total, 25.1% (n = 50/199) of samples were positive for HBV, as measured by PCR. In 41 samples (20.6%), both fragments could be amplified, whereas the HBs gene and the Pol gene fragment alone were detected in 0.5% (n = 1/199) and 4% (n = 8/199) of samples, respectively. Sequences were successfully obtained for all 42 HBs gene fragments but for only 31/49 Pol gene fragments (totaling 73 sequences from 44 individuals). All sequences were identified as HBV genotype E. IEMs were present in 18.2% (n = 8/44) of the sequences of HBV-positive individuals with available sequences. IEM Q129H was detected in eight out of the 44 (18.2%) HBV isolates sequenced in this study; however, no DRMs were observed. This study confirms the circulation of HBV IEMs and reports the presence of Q129H IEM for the first time in Nigeria. Intensified research on the dynamics of IEM is necessary in order to enhance the elimination of HBV.

Fifty patients (18 males, 32 females) with malaria infection and 50 apparently healthy control subjects (22 males, 28 females) were recruited for the study. Hematocrit level (PCV) was determined using Heco C haematology analyzer. Plasma electrolytes (Na+, K+, HCO3 -, Cl-), and glucose were respectively analyzed by SM23A Spectrophotometer, using TECO DIAGNOSTICS and RANDOX enzymatic glucose methods respectively. The results showed a significant reduction in the mean values of PCV (30.04±5.31%), Na+ (131.56±6.63 mmol/L), and glucose (85.92±13.85 mg/dL) in the malaria-infected subjects compared with the mean values of PCV (38.74±3.12%), Na+ (134.14±5.95 mmol/L), and glucose (92.40±13.99 mg/dL) (P0.05. The mean (±standard deviation) of PCV, Na+, K+, HCO3 -, Cl- and glucose in malariainfected patients of different age groups were compared with the age-matched controls, and there were significant differences only in the age groups involving PCV and potassium in the 1-20 and >40 age brackets. This study has shown the importance of electrolyte management in patients with severe malaria to prevent attendant physiological failure during complications.