The specimens capsule that was attached to the direct shear machine to initiate the shearing Figure 2c,d. The were densified with the use of loads of 1, 2 and 4 kg, which resulted in normal stresses of Figure Figure 2. Moldingofofthe 2. Molding the specimens specimens for forthe thedirect shear direct test. The analysis of the results was based on the analysis of the shear strength soil parameters cohesion and internal friction angle and the stress-displacement curves taking into account the soil, the soil-cement, and the soil-cement-strip.
Results and Discussion 3. Compaction Tests 3. Compaction Tests in Soil-Strip Mixtures Table 2 shows the optimal compaction parameters obtained for soil-strip composites, with strip inclusions in different sizes and percentages.
Table 2. Proctor test results performed soil-strip. The decrease in the maximum dry density ranged from 3. The highest specific mass was obtained for inclusions of strips in lower percentages 0. The lowest values were obtained for inclusions of longer length strips and in the highest percentages evaluated 20 and 30 mm long strips in additions of 2.
Given that the specific mass of PET 1. Future evaluation of soil or if it occurs due to the addition of a reduced specific mass material. Future evaluation of soil and and soil-strip permeability is indicated to obtain more specific results. Compaction 3. The The addition addition of cement of cement to the to the soilsoil showed showed no relevant no relevant variations variations in in the the soil soil compaction compaction parameters, parameters, culminating culminating in a small in a very very small variation variation in the in the maximum maximum dry density dry density and in and in a small reduction of de optimum moisture a small reduction of de optimum moisture content.
Table 3. Proctor Proctor test test results results performed performed soil-cement. Unconfined 3. Compressive Tests Unconfined Compressive Tests UCS UCS The medium The medium values values of of unconfined unconfined strength strength average average from from three three tests tests for for each each combination combination ofof length and strip content obtained by the inclusion of PET strips in the soil are shown in Table length and strip content obtained by the inclusion of PET strips in the soil are shown in Table 4 4 and Figure and 3.
Figure Table 4. Values Table 4. Figure Figure 3. UCSresults 3. Results show that the unconfined strength of the samples varies for all sizes and percentages of added strips. In all analyzed cases there is an increase in strength due to the inclusion of strips, regardless of the length and percentages in which they were included.
The result is in an increase of Analyzing Sustainability the , 12, behavior of the soil Figure 3 for different types of strips either in length 8 ofor 19 quantity , there is a tendency to increase soil strength the longer the length of the added strips.
Figure 4 shows the stress-strain curves obtained in the test considering the natural lateritic sandy parameter, soil and thethat is, thesandy lateritic inclusion of strips soil with in which the the inclusion of thesizeoptimum and percentage soil-stripresulted parameterin greater stripsstrength 20 mm long and 1.
It is noted that the inclusion of thistostrip increase, was found for the inclusion of strips with 20 mm in length and 1. The result the increases is inload an increase capacity of of Figure 3 for different types of strips either in length or quantity , there is a tendency to increase soil strength the longer the length The strength of strip-reinforced soil increases with the increasing aspect ratio AR of fibers.
TheseFigure results4 areshows the stress-strain in accordance curves with the obtained literature, inShukla e. It is noted the increase inthat UCS the inclusion might of this to be related strip theparameter bridging not only effect increases of the fiber, the whichloadcan capacity of the efficiently soil, but avoid the also laterthe ductility, increasing development of failurethe deformation planes and strainsof the in soil before the soil.
Stress-strain curves obtained: obtained: natural natural lateritic lateritic sandy sandy soil soil and and lateritic lateritic sandy sandy soil soil with the inclusion of the optimum parameter soil-strips strips 20 mm long and 1.
The strength 3. Direct shear testsof strip-reinforced soil increases with the increasing aspect ratio AR of fibers. These results are in accordance with the literature, e. The shear strength of soil increased with increased 3. As discussed by Tang et al. The inclusion of strips in the evaluated parameter was effective in increasing the 3. The the lowest stresses.
Table 5. Shear strength parameters of soils obtained in direct shear tests for lateritic sandy soil with and without the inclusion of strips. Shear strength parameters of soils obtained in direct shear tests for lateritic sandy soil with and without Sustainability the , 12, inclusion of strips. These curves are very similar Soil with 1. Direct Directshear sheartest testresults: results The soils applied.
The with strips presented a slightly higher variation when compared to soil without soils with strips presented a slightly higher variation when compared to soil without strips.
For strips. For higher normalnormal higher stresses,stresses, there isthere a trend is aoftrend decrease in volume of decrease in variation. The volumetric volume variation. Maher andMaher behavior. Gray [37] andandGrayConsoli [37] andet al. Many authors have reported that the addition of fibers tends to increase inhibiting action of the fibers. Many authors have reported that the addition of fibers tends to increase the ductility and strength the of the ductility andsoil-fiber strengthcomposite as well, of the soil-fiber e.
Direct 3. Table 6 shows the shear strength parameters of the soil and the soil-cement composites of compaction. Table 6 shows the shear strength parameters of the soil and the soil-cement composites found for found for each each shear shear strength strength envelope, envelope, and and Figure Figure 66 presents presents the the shear shear strength strength envelopes envelopes with with and and without inclusions without inclusions of of cement cement for for comparison comparison purposes.
Table 6. Shear strength parameters obtained for the soil with cement content. Figure Failure envelopes 6. Failure envelopes with with the the cement cement addition. In all In all the the cases cases evaluated evaluated herein,herein, thethe addition addition of of cement cement was was mostly mostly effective effective in in increasing increasing soil soil shear strength via the increase in both the cohesion and friction shear strength via the increase in both the cohesion and friction angle parameters angle parameters in large proportions, in large even in caseseven proportions, where smallwhere in cases contents of contents small cement were added.
Most of the shear strength making its application interesting in granular soils. Most of the shear strength of this type of of this type of matrix is matrix due to friction between the particles, which also showed considerable increases.
Figure 77shows Figure showsthe thestress-displacement stress-displacement curves curves obtained obtainedin direct shearshear in direct tests of soilof tests and soil-cement.
Analyzing the curves, it is possible to notice that the rupture of the specimens withspecimens with the addition of cement the occurs after greater displacement than that of the soil without the cement addition of cement occurs after greater displacement than that of the soil without the cement addition.
However, there is a trend for greater However, there isloss of strength a trend afterloss for greater the of peak. This behavior strength is clearly after the peak. Thus, Thus, it can be concluded that it canthe be addition concluded of that cement alters theofrupture the addition cementofaltersthe material, the rupture making of thethe rupture material, fragilethe making so that the rupture material fragile sostrength that thedecreases sharply as material strength the deformation decreases sharply as increases.
In materials the deformation that present increases. These results These results obtained obtainedherein hereinare areininaccordance accordance with withthethe literature literature[11—13,38]. Also, thethe Also, results are results in agreement of the conclusions of Festugato et al.
In this In this sense, sense, a a good good alternative alternative to to avoid avoid this this behavior behavior is is the the addition addition of of strips strips in in soil-cement soil-cement composite. In order to evaluate the influence of the strips on the composite. In order to evaluate the influence of the strips on the strength, ductility, and mainly strength, ductility, and mainlyon on the residual post-peak strength of the soil-cement composites, the residual post-peak strength of the soil-cement composites, a new composite was tested: the a new composite was tested: soil- the soil-cement-strip.
The tests The tests on this on this composite composite were performed were performed with theofinclusion with the inclusion PET strips ofinPET strips different in different lengths 10, 15, 20, and 30 mm and percentages 0.
As previously 1. This expedient seeks to assess how much strength can be increased with the addition of the strips in order to maximize their use and minimize the use of cement. Sustainability , 12, 11 of 19 material with high strength, ductility, and a highly sustainable alternative. Stress-displacement curves 7. Stress-displacement curves obtained obtained in in soil soil and and soil-cement.
Direct Shear Tests in Soil-Cement-Strip Composite Figures 8—11 show the shear stress-displacement curves regarding the soil-cement-strip composite.
Figures 8—11 show the shear stress-displacement curves regarding the soil-cement-strip Results from Figures 8—11 showed that the inclusion of strips provides, in general, a ductile behavior composite. The inclusion sandy soil. This behavior is more pronounced for inclusions of larger strips, 30 mm long, and in larger of 10 mm strips had a greater effect in decreasing the drop in the post-peak strength of the material, quantities.
The inclusion of strips of 15 and 20 mm presented greater however, the drops in strength after the peak were more pronounced in these types of inclusions. Finally, in relation to the stress-displacement behavior of the material, amounts of 1. Figure 8. Figure Direct shear 8. Figure 9. Figure Direct Figure shear The benefits of the addition of strips in increasing the ductility of the composite can be seen in The benefits of the addition of strips in increasing the ductility of the composite can be seen in terms ofThe the benefits variation ofof the the secant elasticity addition of strips inmodulus increasing Epsthe.
The secant ductility of modulus of elasticity the composite can be was seen in terms of the variation of the secant elasticity modulus Eps. The secant modulus of elasticity was calculated terms offromthe the strain at variation of peak strength the secant Eps.
The secant modulus of elasticity was elasticity calculated from the strain at peak strength Eps. The values calculated presented from the strainin at Table peak 7 strength and Figure Eps The values It can be notedinthat presented the 7secant Table modulus and Figure 12 decreases show the with the increase variation of the of Eps with stripcontent strip contentand cement content.
It can be noted that the secant modulus decreases with the increase of the strip as well cementas with the increase content. It can be of noted the cement content. This is because extensible fibers require an deformation to initiate strength mobilization, resulting in the reduction of fiber-reinforced content as well as with the increase of the cement content.
This is because extensible fibers require an cemented initial deformation to initiate strength mobilization, resulting in the reduction of fiber-reinforced soilinitial stiffness. Moreover, to deformation theinitiate addition of higher strength fiber contents mobilization, into the in resulting cemented soil matrix the reduction may lead to of fiber-reinforced cemented soil stiffness.
Moreover, the addition of higher fiber contents into the cemented soil matrix a significant drop in stiffness [43]. Moreover, the addition of higher fiber contents into the cemented soil matrix may lead to a significant drop in stiffness [43]. Table 7. Figure Variationofofsecant DSI isTable the destruction strain 8 presents the index.
DSI values showed Table 8. A small initial decrease considering the strip L mm content of 0. However, in general, the value of the DSI increased for the different contents 0 and 10 lengths. The DSI shows the ductile response0. DSI values Tables showed 9 and an increase 10 present the shearwith the strip stresses content at the peakas well as with obtained the specimen for each length when andcompared the shear to the value of the soil with 2. A small initial decrease strength parameters found for each soil-cement-strip envelope, respectively.
Comparing the considering thevalues strip content obtainedofin0. Comparing the values obtained in Table 10 with Table the shear 9. Only three of the analyzed inclusions presented a reduction in the cohesion parameters, whereas InIngeneral, general,thetheinclusion inclusionofof2.
The cohesions values The cohesions obtained values werewere obtained Results Results from Table9 9show from Table show an an important important characteristic characteristic of theofsoil-cement the soil-cement composite. This This material material may become may heterogeneous.
In some In some cases, cases,strips adding adding to astrips cementedto a matrix cemented madematrix made theof the behavior behavior of the the material material unpredictable.
The failureThe failure of envelopes envelopes some of of thesome of the specimens specimens molded with molded with the lateritic the lateritic sandy soil,sandy addedsoil, withadded cement withandcement strips,and werestrips, not were not consistent consistent with thewith the expected expected increaseincrease in shear instrength.
This may be related to a certain increase in the confining This may be related to a certain increase in the confining tension, as can be seen tension, as can be seen in in the the envelopes envelopes of the of the soilsoil composites-strip-cement composites-strip-cement for for inclusions inclusions of mm of 10 10 mm strips strips in amounts in amounts of 0.
Additionally, Additionally,the thematerial materialpresented presentedanan altered alteredrupture rupture plain plain Figure Figure14a. At the 14a. Atfailure, the the failure, cemented the cementedmatrix aggregates matrix aggregatesthe the strips in order strips in orderto create to createa heterogeneous a heterogeneous material, material,forforwhich whichtensile tensile strength strengthandandthetherupture ruptureplane planewill willdepend dependon onthe thedistribution distributionofofthe thestrips, strips,especially especiallyon onthe thenumber number ofofstrips stripsthat thatwill willbe berequested requestedduring duringthe therupture ruptureand andthetheway wayininwhich whichthe theefforts effortswill willbebedistributed.
The Theanalysis analysisofofthe thesamples samplesafterafterthe therupture ruptureindicated indicatedthat thatonly onlyaasmall smallpercentage percentageofofthe theincluded included strips strips deformed definitively showing folds , which occurred due to the efforts applied during during deformed definitively showing folds , which occurred due to the efforts applied loading loading or during or during compaction compaction of the specimens of the specimens Figure Figure 14b. Figure Figure Direct Directshear sheartests.
In a more detailed analysis of the shear strength parameters, it can be seen that the friction angles and cohesions are not consistent with the expected values of a soil, so that the cement added to the analyzed composites leads to characteristics of cemented matrices, which is why the parameters obtained are so high. These factors are manifested in a more evident way for greater additions of cement or in cases in which the addition of strips occurred.
Few studies have evaluated the effects of the composite formed by soil, cement, and strips. However, the results obtained are in accordance with the results of Tang et al. Conclusions This study evaluated the effect of PET strips on the mechanical properties of a cement-treated lateritic sandy soil. Author Contributions: Conceptualization, M.
G; writing—original draft preparation, M. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Conflicts of Interest: The authors declare no conflict of interest. References 1. Parker, L. Fast facts about plastic pollution.
National Geographic, 20 December Sivakumar Babu, G. Stress-strain response of plastic waste mixed soil. Waste Manag. Soltani-Jigheh, H. Luwalaga, J. Analysing the Behaviour of Soil Reinforced with Polyethylene. Enter the email address you signed up with and we'll email you a reset link. Need an account? Click here to sign up. Download Free PDF. Zamzam Al Rawahi.
A short summary of this paper. Download Download PDF. Translate PDF. Engineering, P. This research addresses the issue of tire waste management and natural aggregate resource depletion. It investigates use of commercially produced recycled tire rubber as replacement for fine and coarse aggregate in non-structural concrete. The study employed a mix proportion of cement: fine aggregate: coarse aggregate with a water-to-cement ratio of 0.
The mixes were tested for their thermal conductivity, water absorption and compressive strength. The behavior of mixes exposed to and oC was also studied and the samples were later tested for compressive strength. The results showed improvements in compressive strength after exposure to heat. Thermal conductivity was reduced as the percentage replacement increased for both fine and coarse aggregate. During heat exposure, the temperature rise was faster in rubberized mixes, and the compressive strength of all mixes improved after the exposure to heat.
Water absorption and void content increased with increase in replacement percentage. The compressive strength did not show a clear trend with the replacement and this is due to the sensitivity of the stiff mix used in the study and its inherent lean nature.
The results indicate that the lean nature of the mix makes it insensitive to small replacement investigated in this research. Waste tires from vehicles are often improperly stored and disposed in Oman by either disposal into stockpiles or illegal dumping. The lack of proper management of these waste tires presents a potential threat to human health and environment [1]. On the other hand, saving natural resources utilized in form of aggregate is a concern.
Concrete could be one of the possible solutions for the utilization of this tire waste and conserve the natural resources. Several studies have been conducted to investigate use of tire rubber waste in concrete. This is an open access article distributed under the terms of the Creative Commons Attribution License 4. With super fine rubber micron [2], the crump rubber enhances sound insulation and thermal conductivity properties of the resulting concrete [3].
Also, the larger the rubber particle size, the higher the effect on compressive strength [4] and as the percentage replacement increased the compressive strength decrease [, ]. Water absorption increases as the percentage replacement increase [1, ]. In addition, the use of tire replacements in structural concrete is likely to face loss in strength, hence, its application to non- structural concrete is more suitable [2].
Therefore, this paper shall investigate the use of tire waste rubber in non-structural concrete as fine and coarse aggregate replacements with different replacement proportions, and study physical properties of the rubberized concrete including water absorption, thermal conductivity and compressive strength.
Also, it shall verify the conformance of the rubberized concrete with the specified standards for non- structural concrete. Oman Concrete Products [7] is one of the leading companies in Oman in the field of infrastructure construction. It has ISO certification. Materials produced by OCP are designed based on a combination of several international standards and also environmental, economical, and technical factors specific to construction in Oman [2].
Physical properties of aggregate and tire rubber are shown in Table 1. Figure 1 a shows the gradation curve of fine aggregate and fine tire rubber. Figure 1 b shows the gradation curve of coarse aggregate and coarse rubber. Coarse tire crumps varied between 2. Table 1.
Physical properties of aggregate and tire rubber. Particle size distribution of natural aggregate and tire rubber. A control mix CM will be produced with 2 sets of mixes. The experimental test scheme is summarized in Table 2. Table 2. Experimental test scheme. Despite the stiff mix produced, no segregation was observed as it can be observed in Figure 2. All the samples were cured for 28 days at room temperature. Heating test is a non-standard test where concrete is exposed to heat at 2 different temperatures, and oC.
The temperature was measured using thermocouples, 1 inside each cube and one in the oven to indicate the temperature at the surface of the cube. The cubes were then inserted in the furnace and the thermocouples were plugged into the data logger to take a reading of the temperature every 10 seconds.
Table 3 lists the investigated mechanical and physical properties of hardened concrete along with the standards used and cubes size. Three specimens were tested for each mix and the property is reported as the average of the three values. Setup for thermal conductivity test.
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