scholarly journals Application of concrete slurry waste in cement screeds

Author(s):  
Pavel Reiterman ◽  
Martin Keppert

Sedimented concrete slurry waste (CSW), containing cement, mineral additives, fine fillers, admixtures and water, is currently a waste without an additional use and has to be fully landfilled. Current CSW management is very expensive and introduces number of environmental risks due to its high pH, exceeding 11.5. This paper deals with the application of two types of CSW as cement replacement in cement screed. The evaluation was carried out in terms of workability and basic mechanical performance of the obtained composites. The applied cement replacement was up to 10 wt.% due to the negative impact on the rheology of fresh mixtures. Reduced workability consequently caused higher content of air in the fresh mixture. It was reflected by lower values of bulk density in hardened state for both studied CSW. These aspects were the reasons of decreased mechanical performance by approximately 15% per 5 wt.% of replacement. Conducted experimental program declared significant limits of CSW application in cement based composites, however additional processing of CSW could significantly modify its properties.

Author(s):  
Jan Fořt ◽  
Petr Hotěk ◽  
Martin Mildner ◽  
Robert Černý

The risk of crack propagation and autogenous shrinkage pose a significant weakness for concrete structures and substantially limits its lifespan. To overbridge related issues, the smart superabsorbent polymers (SAP) can be utilized to mitigate autogenous shrinkage and promote self-healing ability. However, incorporation of highly swelling particles struggles with the workability of the fresh mixture and thus final mechanical performance. Within this paper, the effect of SAP particle size is studied and correlated with the results of flow table test to propose an optimal relationship between the amount of SAP dosage, water/cement ratio and mechanical properties in the hardened state. The reference cement mortar mixture is modified by 0.25, 0.5 and 0.75 wt.% admixture of different 3 grades of SAPs thus the fresh mixture workability, basic material properties, compressive and flexural strength parameters are determined. The obtained results provide guidelines for the efficient design of SAP modified cement mortars mixtures with desired functional properties.


2021 ◽  
Vol 2021 (23) ◽  
pp. 237-250
Author(s):  
Anatolii Morozov ◽  
◽  
Tetiana Morozova ◽  
Inessa Rutkovska ◽  
◽  
...  

Introduction.The main environmental risks posed by roads are population depletion (deaths on roads) and barrier effects (habitat fragmentation). Barrier effects - animals avoid crossing roads, which leads to a decrease in the size and quality of habitat, optimal population size, reduced ability to find food and partner, increased genetic structuring and local extinction (Forman et al. 2003; Andrews et al. 2015; van der Ree et al. 2015). These risks against the background of other stressors, in particular the presence of invasive species, pollution, pesticide use, climate change, plant and animal diseases, may threaten the survival of populations.This issue is especially relevant for herpetofauna due to their biological characteristics. In particular, reptiles and amphibians move slowly, are too small (for drivers to see), do not avoid roads, and in cold periods roads attract amphibians (thermoregulation) because the coating absorbs and retains heat (Case and Fisher 2001; Jochimsen et al. 2004).The principle of ensuring ecological continuity is to identify priority efforts to mitigate environmental risks for animals and reduce the negative impact of the transport complex as a spatial barrier and source of pollution by introducing a number of technical means (eco-crossings, screens, embankments, landscaping). As it is not possible to change the environmental risks on all roads and for all species at present, it is necessary to identify the most vulnerable species, assess the risks to populations and the need for mitigation based on analysis of road density and traffic intensity.Problem Statement. With the advent of land transport there was a progressive environmental problem - the transformation of landscapes, it first appeared in countries with developed road infrastructure in Western Europe and the United States, and quickly spread around the globe (Ellenberg, et al., 1981; Fetisov, 1999; Zagorodnyuk, 2006, Ilyukh, Khokhlov, 2012). Numerous publications by both foreign and domestic authors are devoted to the study of the impact of transport infrastructure. Special attention of European authors is paid to the study of the phenomenon of fragmentation of natural ecosystems. In Europe, there is a network of experts and institutions of IENE, which is studying the possibility of implementing preventive measures for landscape fragmentation, promotes the development of transport infrastructure in accordance with environmental requirements, by creating a safe, environmentally sustainable European transport infrastructure.The ecological trail of the road network significantly exceeds its length (Vozniuk, 2014). This is due to the effects of, in particular, mortality on the roads of mammals, reptiles, reptiles (Forman et al. 2003), landscape fragmentation (roads divide the area into isolated areas, with low populations (sometimes below the minimum), so such populations lose genetic diversity and may become extinct locally), the loss of habitats of species and a decrease in the level of connectivity. In addition to these obvious effects, noise and vibration pollution are added, which inhibit the ability of reptiles, birds and mammals to detect prey or avoid predators (Forman et al. 2003), disturbed light regime (Rich and Longcore 2006). Roads contribute to the development of soil erosion processes, the spread of invasive and introduced species (300-800 seeds/m2 per year are transported to roadside ecotones by vehicles (Von der Lippe and Kowarik 2007), which contributes to the formation of local pseudo-populations), create obstacles and sources. (Forman et al. 2003).Purpose. Substantiation of the principle of ecological continuity regarding the negative impact of transport infrastructure on natural ecosystems and search for possible ways to minimize and prevent such impact.Materials and methods. The main research methods are the application of theoretical general scientific approaches to study: analysis and synthesis of international and domestic scientific and theoretical works, EU documentation (charters, design requirements), Ukrainian legal framework, literature sources; collection and analysis of statistical data to identify the dangers of the impact of road infrastructure on biodiversity and determine the value of the natural landscape.Results. The result is an analysis of the scientific literature on the negative impact of transport infrastructure on animals, systematization of the main impacts for the preparation of methodological documents for organizations planning and designing transport infrastructure in Ukraine to reduce the negative impact.Conclusions. The principle of ensuring ecological continuity is to minimize the negative consequences for the environment. In particular, by leveling the spatial barrier of the public highway. When laying a road through natural ecosystems, it is necessary to build transitions and passages for animals. In this case, their density and type must correspond to the natural rank of the territory. The construction of crossings for animals should be mandatory for all types of roads that cross ecological corridors. This is especially true for smaller roads, completely devoid of any transitions for animals, noise shields (on such roads are more likely to hit animals). An important point is the need to plan preventive methods at the planning stage of road construction. The analysis of the European experience shows that the negative impact of transport infrastructure on biota can be solved by consolidating the efforts of road transport specialists and specialists in the field of nature protection.Keywords:motor road,wildlife crossing, biodiversity, road infrastructure, ecological continuity


2019 ◽  
Vol 51 (1) ◽  
pp. 39-56 ◽  
Author(s):  
Anja Terzic ◽  
Lato Pezo ◽  
Ljiljana Milicic ◽  
Nevenka Mijatovic ◽  
Zagorka Radojevic ◽  
...  

Mineral additives are extensively applied as cement replacement materials in both construction concrete and mortar. Fly ash is one of the most commonly utilized additives which improve rheological properties, as well as thermal and mechanical behavior of mortar, and as such it has been widely investigated. This industrial byproduct comprises heavy metals in its composition; therefore further research is needed to optimize its effective dosage. Moreover, certain sorptive clays, such as natural zeolite and bentonite, can prevent migration of toxic elements from fly ash by immobilizing them in their structure. Ten experimental mortars are prepared with Portland cement, river sand and addition of fly ash, zeolite and/or bentonite in accordance with chemometric experimental design rules. The aim of the study was to investigate the effect of mineral additives on thermal and mechanical performances of mortar. Thermal characteristics were monitored via dilatometric analysis and DTA method. Principal component analysis was used on the results of physico-mechanical testing (workability, bulk density, water absorption, shrinkage, compressive and flexural strength) to enable the divisions of the observed samples into groups in the factor space. The performance of Artificial Neural Network was compared with the experimental data in order to develop rapid and accurate method for prediction of mechanical parameters of mortar. The ANN model showed high overall prediction accuracy (r2 = 0.989, during training cycle). The test results indicate that incorporation of the mineral additives gave cost effective mortars with sufficiently good properties. However, tools of analytical modeling highlighted mortar with zeolite and fly ash as the optimal composition regarding its mechanical performance.


Author(s):  
F. Longo ◽  
A. Cascardi ◽  
P. Lassandro ◽  
M. A. Aiello

AbstractAll over the world, a large part of existing buildings is not adequate to satisfy the safety requirement and the thermal comfort criteria. For this reason, the interest in structural and energy retrofitting systems has steadily grown in the last decades. In this scenario, an innovative thermal resistant geopolymer mortar has been developed and used for Inorganic Matrix Composite (IMC) systems aimed to a combined seismic and energy new retrofitting technique. The geopolymer-based IMC is able to ensure competitive mechanical properties with respect to the traditional lime-based IMCs and, at the same time, a significant reduction in thermal conductivity. In this paper, an experimental program is reported considering small-scaled masonry panels with double-side IMC-retrofitting and determining both the in-plane shear strength and the thermal resistance. The experimental shear tests are aimed to compare the mechanical performance of the geopolymer innovative systems with those of the traditional lime-based ones. Moreover, the thermal resistance gain of the innovative solutions was measured and compared with traditional systems. The results evidenced the effectiveness of the proposed technique that significantly improved the performances of masonry walls from both the thermal and the mechanical point of view.


Author(s):  
H. Haruna

Land use changes from forest into cultivated ecosystems result in negative impact on soil structure and quality. The purpose of this study was to determine effect of land use on soil quality in Afaka forest northern guinea savannah of Nigeria. Land use systems, including natural forest and cultivated land were identified. Eighteen (18) composite disturbed and undisturbed samples were collected from depth of 0-5 and 5-10 cm for analysis of pertinent soil properties in the laboratory using grid procedure. Most physical and chemical properties show relative variations in response to land use types and geomorphic positions. Results  indicate  that the soils had  high degree of weathering potentials, low  to moderate  bulk density at 0-5cm depth values between 1.42 to 1.49 Mg m-3 in  forest and  cultivated land, bulk density of  1.34 and 1.46 1.Mg m-3at 5 -1ocm depth   for forest and  cultivated land respectively. The soil water at 0-5cm depth is from 4.20 to 2.63 cm3/cm3, while at 5-10 cm depth these values vary from 4.32 to 2.13 cm3/cm3 under forest and cultivation land use. The pH (H2O) is 6.9 to 7.16 with low electrical conductivity of 0.13 dS/m(forest) and 0.12 dS/m (cultivation). The CEC of soils is recorded as 8.60 cmol kg-1 (forest) to 8.54 cmol kg-1 (cultivated)whereas  total nitrogen content of 1.21 g kg-1 and 1.11 g kg-1 and available phosphorus of 8.78 mg kg-1 (cultivated) and 5.47 mg kg-1 (forest).. Results indicate that soil fertility parameters were moderate to low for cultivated land and at all slope positions, suggesting that soil fertility management is required in order to make agriculture sustainable on Afaka area.


Author(s):  
Ali Abdulhussein Shubbar ◽  
Ali Al-Shaer ◽  
Rasha Salah AlKizwini ◽  
Khalid Hashim ◽  
Hayder Al Hawesah ◽  
...  

2019 ◽  
Vol 292 ◽  
pp. 108-113 ◽  
Author(s):  
Josef Fládr ◽  
Petr Bílý ◽  
Roman Chylík ◽  
Zdeněk Prošek

The paper describes an experimental program focused on the research of high performance concrete with partial replacement of cement by fly ash. Four mixtures were investigated: reference mixture and mixtures with 10 %, 20 % and 30 % cement weight replaced by fly ash. In the first stage, the effect of cement replacement was observed. The second phase aimed at the influence of homogenization process for the selected 30% replacement on concrete properties. The analysis of macroscopic properties followed compressive strength, elastic modulus and depth of penetration of water under pressure. Microscopic analysis concentrated on the study of elastic modulus, porosity and mineralogical composition of cement matrix using scanning electron microscopy, spectral analysis and nanoindentation. The macroscopic results showed that the replacement of cement by fly ash notably improved compressive strength of concrete and significantly decreased the depth of penetration of water under pressure, while the improvement rate increased with increasing cement replacement (strength improved by 18 %, depth of penetration by 95 % at 30% replacement). Static elastic modulus was practically unaffected. Microscopic investigation showed impact of fly ash on both structure and phase mechanical performance of the material.


2012 ◽  
Vol 2290 (1) ◽  
pp. 161-167 ◽  
Author(s):  
Somayeh Asadi ◽  
Marwa M. Hassan ◽  
John T. Kevern ◽  
Tyson D. Rupnow

Self-cleaning, air-purifying pervious concrete pavement is a promising technology that can be constructed with air-cleaning agents with superhydrophilic photocatalyst capabilities, such as titanium dioxide. Although this technology has the potential of supporting environment-friendly road infrastructure, its effectiveness depends on a number of design and operational parameters that need to be evaluated. The objective of this study was to evaluate the mechanical, environmental, and mix design parameters that influence the performance and effectiveness of photocatalytic pervious concrete pavement. To achieve this objective, an experimental program was conducted in which the effects of relative humidity level, pollutants' flow rate, and mix design parameters, including void ratio and depth of the photocatalytic layer, were investigated. Mechanical performance tests included porosity, unit weight, permeability, and compressive strength. The environmental efficiency of the samples to remove nitrogen oxides (NOx) from the atmosphere was measured in the laboratory. Results of the experimental program showed that increasing the depth of the photocatalytic layer increased NOx reduction efficiency. In addition, NOx removal efficiency decreased with the increase in the pollutant flow rate and increased with the increase in ultraviolet light intensity.


2019 ◽  
Vol 11 (20) ◽  
pp. 5652 ◽  
Author(s):  
Yao Lu ◽  
Hankun Lin ◽  
Siwei Liu ◽  
Yiqiang Xiao

This study investigated the potential of using a nonuniform woven panel with nonuniform strips—thick sticks and thin battens—as an external solar shading screen that addressed daylighting, shading, and mechanical performance factors. The sustainable material, namely, bamboo, was used as the demonstration material for the screen. An on-site experiment and ANSYS simulation were carried out to investigate the basic solar optical performance and structural strength of the proposed screen, respectively. Then, a series of daylighting simulations were conducted to optimize the configuration of the screen. The results showed that the nonuniform woven solar shading screen reduced up to 80.3% of the solar radiation gain in a room during summer months while ensuring a relatively even distribution of useful daylight during the year. Moreover, the screen effectively reduced the negative impact of glare to a level below “imperceptible” and enabled a relatively clear view through the window and shading. Regarding the structural strength, the screen with a size smaller than or equal to 1 × 1 m withstood a wind load of 12 m/s. Furthermore, this study proposed two optimal configurations: a screen woven of square sticks and battens with a distance of 10 mm between them, and a screen woven of round sticks and battens with a distance of 8 mm between them. This study illustrated the superiority of the nonuniform woven solar shading screens, which supports a wider application of solar shading screens made of other materials with similar structures and reflectance values.


2020 ◽  
Vol 868 ◽  
pp. 32-38
Author(s):  
Valéria Gregorová ◽  
Zuzana Štefunková ◽  
Miriam Ledererová

In this paper, the selected properties of lightweight composites based on the different kinds of binder and recycled waste plastics aggregate were studied. Plastic waste e.g. foamed polystyrene, polypropylene, polyurethane foam or ethyl vinyl acetate (EVA) as an aggregate in these composites was used. Cement CEM II B/S 32.5 R and an organic-based adhesive with the business name Conipur 360 were used as a binder. The cement composites consisted of constant water to cement ratio 0.50 and dose of cement 175 kg/m3. Mixtures of adhesive composites were prepared with constant dose of adhesive 100 kg/m3. The kind of recycled waste aggregate was only changed. The physical properties, such as bulk density, compressive strength and thermo-technical properties were verified. The application of organic-based adhesive resulted in a significant decreasing values of the bulk density (100 kg/m3 - 230 kg/m3) and the thermal conductivity coefficient (0.0511 W/m.K - 0.0686 W/m.K) of lightweight composites. The negative impact of this type of binder resulted to a decreasing value of the compressive strength (0.15 MPa - 0.32 MPa). Use of cement binder caused to an increasing of bulk density (290 kg/m3 - 375 kg/m3) and worsening of the thermal conductivity coefficient of these composites (0.0660 W/m.K - 0.0799 W/m.K). The compressive strength values of cement composites ranged from 0.24 MPa to 0.50 MPa.


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