Use of Glass Powder and Sand Dune in Concrete: Characterization and Performance

Cement and alluvial sand are very essential materials in concrete preparation. The first material production contributes to the emissions of greenhouse gases, in particular carbon dioxide (CO2), and the extensive exploitation of second material constitutes a danger on the extinction of its deposits. The use of waste glass powder (WGP) to partially replace cement and dune sand as a replacement for a small amount of alluvial sand appears as a potential solution that solves several problems at once (disposal of glass waste, reduction of emissions gas and preservation of construction sand deposits). The objective of this study is to verify the effects of these partial replacements on concrete properties, their cost, and the CO2 emission reduction in the atmosphere. For this, three types of concrete are prepared: a control (0% of WGP); mixture 1 (10% WGP); and mixture 2 (20% WGP). In all three types, 5% of alluvial sand is replaced by dune sand. Obtained results show that these partial replacements do not affect the porosity (less than 20%), they give good indices as to the speed of sound propagation in the concrete (up to 3500 m/s), especially for the case of the second mixture after 56 days but this does not increase the concrete performance concerning compressive strength and performance of concrete with glass is less than that of control concrete. Economically, the reduction of 10% in cement saves 5 € per ton and environmentally, it reduces the emission of CO2 from cement industry by 0.5 to 0.7% of total anthropogenic CO2 emissions.

Germination and growth of the tree Handroanthus chrysanthus (Bignoniaceae) under nursery conditions

Introduction: Selective logging of forests has significantly diminished the densities of Handroanthus chrysantha Jacq. in Colombia. Therefore, there is a need for studies that contribute to its management. Objective: We aimed to evaluate seed germination and the growth of seedlings under nursery conditions. Methods: Four pre-germinative, four organic substrates and two luminosity conditions were tested. We used a random multifactorial experimental design composed of 32 controlled factors. The main components were immersion of seeds in water at room temperature at different times, combinations of organic substrates and exposure of the factors to shade and sun. Results: We recorded 395 and 290 germinated seeds, corresponding to 51 and 38% of the total sown under shade and sun, respectively. The factors with the best germination values were immersion for 24 hours with alluvial sand and immersion for 24 hours with river sand of mixed with ant soil (2:1) under shade and, without immersion with alluvial sand+ground of ant 2:1 and immersion for 24 hours with chicken manure+ant soil 2:1 under sun. The highest growth in height, vigour and survival was observed in seedlings exposed to full sunlight in any of the combinations of organic substrates. Conclusion: The propagation of H. chrysantha should germinate the seeds under shadow and then expose them to the sun to stimulate their growth..

Microstructure and Mechanical Behavior of Concrete Based on Crushed Sand Combined with Alluvial Sand

The aim of this work is to reduce the overexploitation of river sand by proposing a combination of crushed sand and river sand to develop an optimal mix design for concrete. The approach used consisted of a physical, chemical, and mineralogical characterization of aggregates from three quarries located in Yaoundé (Cameroon), followed by the formulation of concrete by substituting 100%, 90%, 80%, 70%, 50%, and 0% of the river sand with crushed sand. A physical and mechanical characterization of the concrete was carried out, as well as a microstructural characterization using SEM/EDS. The results showed that the concrete made of crushed sand only had a higher drying shrinkage at a young age compared to the river sand concrete. Compared to conventional concrete (made using 100% of river sand), the concrete with 50% crushed sand reduces its slump value, has a lower porosity, and has a compressive strength value of 26.3 MPa at 28 days, which is very similar to that of conventional concrete (26.7 MPa). Moreover, it was found that the strength of the concrete increased by 14.4% and 20.6%, respectively, for concrete without crushed sand (BSR0) and concrete with 50% crushed sand (BSR50) by increasing the curing age from 28 to 90 days. The static modulus of elasticity for conventional concrete BSR0 and BSR50 concrete with 50% crushed sand at 90 days was 23.7 and 21.8 GPa, respectively. Thus, combining crushed sand with alluvial sand is a good method to reduce the depletion of alluvial sands in Cameroon.

The End of Sand

This chapter focuses on how sand, the second most used natural resource on earth after water, is facing one of the greatest environmental challenges of the new millennium. Sand is a crucial material used in all sorts of building projects, from asphalt, concrete, and glass. Globally, construction accounts for the largest portion of the 15 billion tons of sand consumed annually. Yet, sand is a finite resource and the depletion of alluvial sand used in construction is destroying the ecosystem of riverbeds, sea beds, and coastal beaches, and is contributing seriously to climate change. This chapter will discuss how these threats have developed, including coastal construction and erosion, river dredging, and sand “mafias” whereby illegal sand miners strip beaches and use sand in inferior concrete that has led to building collapses and deaths. The authors then discuss potential solutions to this crisis, including regulation and enforcement of environmental and construction standards, as well as materials substitution such as desert sand, sand created from sandstone, and recycled glass.

Dynamics of grass stand formation in poplar plantations on different types of reclamations of disturbed lands of Western Donbass

The purpose of our research was to study the long-term dynamics of the herbage cover at different stages of growth and development of poplar plantations on the types of artificial soils of the forest reclamation area. The object of research is flora phytotoxic dumps of «Blagodatna» coal mine, where imported substrates such as sand-clay, clay loam, red-brown earth and humic soil in various combination were applied to create reclamations layer on the surface of the mine dumps (Dnipropetrovsk region, Pavlograd region). Type 1: 30 cm of soil mass of typical chernozem (SMTC), 50 cm of red-brown earth, 80 cm of alluvial sand-clay and sand, and deeper there is the coal mine solid; type 2: 30 cm of SMTC, 80 cm of sand, and mine solid deeper; type 3: 30 cm of SMTC, 60 cm of alluvial sand-clay, 60 cm of clay, and deeper there is mine solid; type 4: 40 cm of SMTC, 30 cm of red-brown earth, 40 cm of sand and mine solid deeper; type 5: 55 cm of alluvial sand-clay, deeper there is mine solid. Stationary observations were carried out in poplar plantations of 8-, 16-, 27- and 34-year-old age on permanent trial plots. They were presented with a black poplar and seven hybrid poplars. The research has established that climatic conditions, influence of surrounding phytocenoses of undisturbed lands, inheritance by pedozems of seed material of grass plants with a fertile layer of the soil set the direction of succession on the way of formation of zonal herbal group. The long-term growth of the role of the arid element indicates the formation of a structure close to the zonal flora. The formation of the flora of technical soils in poplar plantations occurs in four stages: the first is pioneer plant communities, which begins with the completion of the technical phase of reclamation and confined to the stages of forest formation; the second is a simple grouping that is associated with the development of the stand until the closure of canopy and inter-row soil cultivation; the third is a complex grouping that is fraught with pole wood stage of stand development and partial getting sparse; the fourth in our studies, is partially closed when gradually tree plants disappear and their influence disappears. In addition to the influence of tree vegetation, its age and stage of development, the formation of lower layers of biogeocenoses is significantly influenced by the conditions stipulated by the stratigraphy and the power of artificial substrates, as well as the elements of the landscape, both created initially and formed as a result of the fragmentary subsidence of the dump territory. These factors, depending on their dynamic changes, regulate correlation between various groups of biomorphs, climamorphs, trofomorphs, hygromorphs, heliomorph and zenomorphs in the grass cover. Created forest vegetation conditions on the plateau and the upper third of the dump do not meet the needs of hybrid poplars under conditions of acute shortage of moisture, which are characteristic of the steppe zone. Fast-growing poplar hybrids can be used as a pioneer culture up to 15–20 years of age.