Impact of Length and Percent Dosage of Recycled Steel Fibers on the Mechanical Properties of Concrete

The global rapid increase in waste tyres accumulation, as well as the looming social and environmental concerns, have become major threats in recent times. The use of Recycled Steel Fiber (RSF) extracted from waste tyres in fiber reinforced concrete can be of great profitable engineering applications however the choice of suitable length and volume fractions of RSF is presently the key challenge that requires research exploration. The present experimental work aims at investigating the influence of varying lengths (7.62 and 10.16 cm) and dosages (1, 1.5, 2, 2.5, 3, 3.5, and 4%) of RSF on the various mechanical properties and durability of concrete. Test results revealed that the varying lengths and dosages of RSF significantly affect the mechanical properties of concrete. The improvements in the compressive strength, splitting tensile strength, and Modulus of Rupture (MOR) of RSF reinforced concrete observed were about 26, 70, and 63%, respectively. Moreover, the RSF reinforced concrete showed an increase of about 20 and 15% in the yield load and ultimate load-carrying capacity, respectively. The durability test results showed a greater loss in compressive strength and modulus of elasticity and a smaller loss in concrete mass of SFRC. Based on the experimental findings of this study, the optimum dosages of RSF as 2.5 and 2% for the lengths 7.62 and 10.16 cm lengths, respectively are recommended for production of structural concrete. Doi: 10.28991/cej-2021-03091750 Full Text: PD

Vegetation Pattern and Regeneration Dynamics of the Progressively Declining Monotheca buxifolia Forests in Pakistan: Implications for Conservation

Monotheca buxifolia (Falc.) A. DC., a wild edible fruit-yielding tree species, has economic and ecological importance, yet there is a lack of studies concerning its distribution pattern and regeneration dynamics at a larger-scale. This study aims to produce the first country-level classification of Monotheca forests based on their unique floristic composition and influential abiotic factors, besides their natural regeneration dynamics, across the environmentally diverse landscapes in Pakistan. For this purpose, floristic inventory was carried out in 440 plots where environmental variables, stand dendrometric characteristics and woody-species regeneration were recorded. During this survey, 3789 individuals of 27 woody tree species belonging to 25 genera and 22 families were sampled. These native and exotic tree species were mostly dicot (73%) with predominately mega-phanerophytic (88%) lifeforms, which largely reflect strong chorological differentiation and distinct linkage (55%) to the Sino-Japanese phytogeographical region. M. buxifolia and co-occurring species exhibiting similar environmental affinities were grouped into four ecologically distinct communities by Ward’s cluster analysis. Ordinations further highlight the special effects of topographic and edaphic factors besides anthropogenic interference on the sampled plots. Generally, Monotheca stands were moderately dense, with the average density varying considerably, ranging from 296 to 325 individuals/ha, with basal area ranging from 41.26 to 93.35 m2 ha−1. In the understory stratum, natural regeneration of Monotheca was mostly scant and mainly covered by Dodonaea shrubs. Size class structure of the dominant species shows pronounced effect of anthropogenic intervention as reflected by the presence of fewer individuals of juveniles and larger trees. Overall, the cut stump frequency was higher at juvenile and mature stages, which may be attributed to over-harvesting and extraction of fuelwood apart from the adverse effect of climate change in the region. We concluded that both topographic and edaphic factors coupled with biotic interventions are more influential in the distribution and persistence of M. buxifolia and co-occurring woody species and might be considered in its restoration and conservation. Thus, we recommend an urgent management plan to favor Monotheca regeneration for allowing the renewal of these rapidly declining remnant stands in Pakistan

Vegetation Pattern and Regeneration Dynamics of the Progressively Declining <i>Monotheca buxifolia</i> Forests in Pakistan: Implications for Conservation

Monotheca buxifolia (Falc.) A. DC., a wild edible fruit-yielding tree species, has economic and ecological importance, yet there is a lack of studies concerning its distribution pattern and regeneration dynamics at a larger-scale. This study aims to produce the first country-level classification of Monotheca forests based on their unique floristic composition and influential abiotic factors, besides their natural regeneration dynamics, across the environmentally diverse landscapes in Pakistan. For this purpose, floristic inventory was carried out in 440 plots where environmental variables, stand dendrometric characteristics and woody-species regeneration were recorded. During this survey, 3789 individuals of 27 woody tree species belonging to 25 genera and 22 families were sampled. These native and exotic tree species were mostly dicot (73%) with predominately mega-phanerophytic (88%) lifeforms, which largely reflect strong chorological differentiation and distinct linkage (55%) to the Sino-Japanese phytogeographical region. M. buxifolia and co-occurring species exhibiting similar environmental affinities were grouped into four ecologically distinct communities by Ward’s cluster analysis. Ordinations further highlight the special effects of topographic and edaphic factors besides anthropogenic interference on the sampled plots. Generally, Monotheca stands were moderately dense, with the average density varying considerably, ranging from 296 to 325 individuals/ha, with basal area ranging from 41.26 to 93.35 m2 ha−1. In the understory stratum, natural regeneration of Monotheca was mostly scant and mainly covered by Dodonaea shrubs. Size class structure of the dominant species shows pronounced effect of anthropogenic intervention as reflected by the presence of fewer individuals of juveniles and larger trees. Overall, the cut stump frequency was higher at juvenile and mature stages, which may be attributed to over-harvesting and extraction of fuelwood apart from the adverse effect of climate change in the region. We concluded that both topographic and edaphic factors coupled with biotic interventions are more influential in the distribution and persistence of M. buxifolia and co-occurring woody species and might be considered in its restoration and conservation. Thus, we recommend an urgent management plan to favor Monotheca regeneration for allowing the renewal of these rapidly declining remnant stands in Pakistan

Invasive Milk Thistle (<i>Silybum marianum</i> (L.) Gaertn.) Causes Habitat Homogenization and Affects the Spatial Distribution of Vegetation in the Semi-Arid Regions of Northern Pakistan

Global biodiversity management is of concern due to invasive plant species that dramatically disturb the native communities causing biological homogenization. Therefore, the present research investigated the impacts of Silybum marianum, an aggressive invasive alien species, on communities’ diversity and environmental variables in Khyber Pakhtunkhwa, Pakistan. Phytosociological characteristics and diversity indices of the communities were sampled in seventy-five sites using the quadrate method. These sites were categorized based on invasion intensities, i.e., fully invaded sites with a 100% importance value index of the selected species, severely invaded sites with >60% of IVI, and partially invaded sites with >30% of the chosen species. The community composition significantly changes with changes in invasion intensity. Similarly, S. marianum invasion has a pronounced impact on the community’s diversity showing significant differences among the three categorized groups (p S. marianum dominated well-established communities in the existing soil and environmental variables; therefore, it was found to be influential in disturbing the native communities and may severely harm the crop plant and agricultural system in the future

Invasive Species as Rivals: Invasive Potential and Distribution Pattern of Xanthium strumarium L.

Xanthium strumarium L. is a globally successful invasive herb that has had significant negative ecological, economic and social impacts in many world regions. The present study was therefore conducted to evaluate the invasive potential and spatial distribution patterns of X. strumarium in heavily invaded plant communities of the semiarid regions of northern Pakistan. Investigations were based on data from 20 plants grown in the Herbarium at the University of Malakand, and from observations in 450 plots distributed across 45 stands representing habitats across Northern Province including open fields, hillocks and abandoned areas in both urban and rural areas. Multivariate analysis identified elevation, organic matter and organic carbon as the environmental variables most associated with communities invaded by X. strumarium. Increased soil silt was positively associated and available water was negatively associated with X. strumarium–invaded communities. These key environmental characteristics allowed us to identify four main associations: Group I: X. strumarium-C. sativa, Group II: X. strumarium-P. hysterophorus, Group III: X. strumarium-A. aspera and Group IV: X. strumarium-C. sativa. Other invasive species were observed, either exotic, such as P. hysterophorus, or indigenous, such as C. sativa and D. inoxia, often co-occurring and responding similarly to these factors. The results suggest that high temperature with drought stress could be a determinant of increasing population at lower elevations, whereas colder climates with adequate moisture are related to reduced populations at higher elevations, near the species’ upper range limits. It is recommend that the inclusion of appropriate, additional soil and climatic variables in species distribution models be implemented in order to better explain species’ ecological niches and help guide conservation and protection plans for native plant communities.Arts, Faculty ofGeography, Department ofReviewedFacult

Plant Species Classification and Diversity of the Understory Vegetation in Oak Forests of Swat, Pakistan

The forest ecosystem has understory vegetation that plays a vital role in sustaining diversity, providing nutrients, and forming a useful association for developing a balanced ecosystem. The current study provides detailed insights into the plant biodiversity and species classification of the understory vegetation of Swat, Pakistan. The floral diversity of the area was comprised of 58 plant species belonging to 32 families. The physiognomy of the studied area was dominated by herbaceous growth form with 47 species. The dominant life-form class was hemicryptophytes with 19 species (33%), followed by nanophanerophytes with 15 species (26%) and therophytes with 13 species (22%). Of the 58 species, 43 plant species were associated with group III clustered by applying Ward&rsquo;s agglomerative clustering that indicated wide sociability of the species in the studied oak-dominated forests. Group III had higher species richness (10.3), &alpha;-diversity (2.74) and &beta;-diversity (9.85), and Margalef index values (3.95). While the group I had maximum Pielous and Simpson index values of 0.97 and 7.13, respectively. Redundancy analysis revealed that seven variables (i.e., latitude, elevation, clay, wilting point, bulk density, saturation, and electric conductivity) were significantly influential concerning the understory vegetation of oak-dominated forests. The understory vegetation of these forests plays an important role in the forest ecosystem of the region. The present study reveals floral divergence and physiognomic scenario of the unexplored study area, which could be an important reference for future ethnobotanical, phytosociological, and conservational endeavors. Moreover, this information is important to the success of efforts intended to prevent the loss of species diversity in these forests by destroying their natural habitats

Utilization of waste marble powder as partial replacement of cement in engineered cementitious composite

AbstractThe current study focuses on the utilization of Marble Waste Powder (MWP) as a partial substitution of cement along with local sand instead of microsilica sand in Engineered Cementitious Composite (ECC). The aim was to reduce the environmental concerns of ECC by reducing the cement content without adversely affecting the desired properties. Four mixes were evaluated; the control mix which has no MWP and three test mixes having cement replacement with MWP by 10%, 15%, and 20% were used, respectively. The properties of ECC mixes were found in terms of compressive, tensile, and flexural characteristics. The trend of change in the basic properties of ECC with an increased percentage of MWP as partial substitution of cement was found along with the hypothesis test on the experimental data. From this study, it was concluded that the increased percentage of MWP reduces on the compressive strength of ECC. The maximum reduction in compressive strength of ECC was recorded as 49% with 20% replacement of cement with MWP, as compared to the control sample at 91 days of test age. The tensile strain of ECC increases with the increase in MWP content, while the tensile stress increases only with the increase of MWP content up to a specified limit. The ultimate load in the force–deflection curve first increases with the increase in MWP content up to a certain percentage, while upon further increase in MWP content from 15% to 20%, the ultimate load decreases. The study suggests that the properties do not vary significantly for the modified ECC samples containing MWP, especially the 10% and 15% MWP samples, and can be utilized instead of normal ECC, thus mitigating environmental concerns without compromising the ECC’s performance