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Environmental and technical evaluation of cement reduction and test methods for fibre reinforced shotcrete in tunnelsBrodd, Elin, Östlund, Lina January 2022 (has links)
The dominating support method for hard rock tunnels today is use of fibre reinforced shotcrete in combination with rock bolts. The fibre reinforced shotcrete secures smaller blocks, while rock bolts are used to support larger blocks in the rock. Application of shotcrete is done by spraying against the rock surface using compressed air. The use of accelerators result in fast strength development and adhesive properties, which are two characteristics of great importance when constructing tunnels. This thesis aims at increasing the understanding of climate impact from fibre reinforced shotcrete in tunnel construction. The focus is on reducing the climate impact with two methods: reducing the share of cement in the shotcrete mixture through substitution with addition materials and using better test methods for fibres. Cement is one of the most important ingredients in concrete, however also the largest contributor to CO2 emissions. Reducing the cement amount is therefore a way of reducing the emissions of concrete. In addition, when testing the performance of fibres, different methods can lead to a spread in the results, causing an overuse of fibres in the shotcrete. First, the thesis investigated the use of alternative binder materials, especially Ground Granulated Blast Furnace Slag (GGBS), as a substitute for cement. Experimental testing was performed in a laboratory to evaluate the compressive strength for shotcrete with different amounts of GGBS. Testing was performed after one and seven days in order to evaluate the early strength. Second, the thesis investigated the use of fibre reinforcement and the possibilities of reducing the fibre dosage when changing fibre type and test method. Numerical modelling was performed for two test methods, beam and panel testing, based on experimental data. The thesis evaluated the environmental performance in terms of Global Warming Potential for both fibres and binder. The results show that substituting cement with GGBS has the largest potential to lower the CO2 emissions from fibre reinforced shotcrete. In addition, the fibre dosage can be lowered by changing fibre type, but also test method. Also this lowers the emissions, however the main emissions origins from the binder part. / Den dominerande förstärkningsmetoden för tunnlar i hårt berg idag är fiberarmerad sprutbetong i kombination med bergbultar. Den fiberarmerade sprutbetongen säkrar mindre block, medan bergbultar säkrar större block från att falla ner. Sprutbetongen appliceras genom sprutning direkt mot bergytan men hjälp av tryckluft. Användning av acceleratorer medför snabb hållfasthetsutveckling och vidhäftande egenskaper, vilka är av stor vikt vid tunnelkonstruktion. Syftet med examensarbetet är att öka förståelsen för klimatpåverkan från fiberarmerad sprutbetong i tunnelkonstruktion. Fokus är att undersöka minskningar i klimatpåverkan med två metoder: minska andelen cement i betongblandningen genom ersättning med alternativa material och använda bättre testmetoder för fibrer. Cement är en av de viktigaste ingredienserna i betong, men också den största bidragande faktorn till koldioxidutsläpp. Minskning av andelen cement är därför ett sätt att reducera utsläppen från betong. Dessutom kan valet av testmetod ha stor påverkan på vilken dosering av fibrer som krävs. Examensarbetet undersökte först användningen av alternativa bindemedelsmaterial, speciellt granulerad masugnsslagg, i sprutbetong som ett ersättningsmaterial till cement. Experiment i labb utfördes för att utvärdera tryckhållfastheten för gjuten sprutbetong med olika andelar granulerad masugnsslagg. Testning genomfördes efter en respektive sju dagar för att utvärdera hur slagg påverkar den tidiga hållfastheten. Användningen av fiberarmering och möjligheten att reducera fiberinnehållet vid byte av fibersort och testmetod undersöktes sedan. Numerisk modellering genomfördes för två testmetoder, balk- och plattest, baserat på experimentell data. Examensarbetet utvärderade klimatpåverkan i termer av Global Warming Potential, GWP, för både fibrer och bindemedel i sprutbetong. Resultaten visar att ersättning av cement med granulerad masugnsslagg har den största potentialen att minska koldioxidutsläppen från fiberarmerad sprutbetong. Dessutom kan fiberdoseringen minskas genom ändrad fibertyp samt ändrad testmetod, vilket också minskar utsläppen. Emellertid härstammar de största utsläppen från bindemedlet.
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Betondruckfestigkeit unter zweiaxialer dynamischer BelastungQuast, Matthias 27 May 2020 (has links)
Zur Beantwortung der Frage, wie sich die festigkeitssteigernden Effekte aus mehraxialer und dynamischer Druckbelastung in Beton überlagern wurde ein weltweit einzigartiger zweiaxialer Split-Hopkinson-Bar entwickelt. Es wurden umfangreiche Versuchsserien mit insgesamt mehr als 2500 Einzelversuchen durchgeführt. Ermittelt wurden dabei die ein- und zweiaxialen statischen und dynamischen Betondruckfestigkeiten zweier Betone der Druckfestigkeitsklassen C20/25 und C40/50.
Die Versuchsergebnisse wurden hinsichtlich der Festigkeitsentwicklung in Abhängigkeit vom Spannungsverhältnis und der Dehnrate ausgewertet. Die Ergebnisse aus den zweiaxialen dynamischen Betondruckversuchen konnten als dreidimensionale Abhängigkeit der Spannungen in beiden Belastungsachsen von der Dehnrate für jede der beiden Betonsorten abgebildet werden. Aus den Ergebnissen wurde ein Ingenieurmodell für jede Betonsorte entwickelt, welches die Betondruckfestigkeitsentwicklung in Abhängigkeit vom Spannungsverhältnis und der Dehnrate beschreibt. Mit zunehmender Dehnrate wird die zweiaxiale Ergebniskurve um einen zusätzlichen, dynamischen Anteil der Festigkeitssteigerung vergrößert. Dabei kommt es aber nur zu einer teilweisen Überlagerung der beiden betrachteten festigkeitssteigernden Einflüsse. Eine Abschätzung der Größenordnung der jeweiligen Einflüsse aus Mehraxialität und hoher Belastungsgeschwindigkeit konnte durch eine entsprechend differenzierte Auswertung vorgenommen werden.
Die Untersuchung der Bruchstücke der zerstörten Probekörper zeigte, dass die Verteilung der Partikelgröße stark von der Dehnrate abhängig ist. Im Gegensatz dazu hängt die Partikelgeometrie und die Form und Masse der entstehenden Kernbruchstücke vom Spannungsverhältnis ab.
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Rheology of grout for preplaced aggregate concrete. Investigation on the effect of different materials on the rheology of Portland cement based grouts and their role in the production of preplaced aggregate concrete.Ganaw, Abdelhamed I. January 2012 (has links)
Preplaced aggregate concrete (PAC) is produced by grouting high workability cement
based grouts among the voids of compacted coarse aggregate mass. Because of its low
shrinkage, PAC has been used for many repair jobs like; tunnel lines, dams and bridge
piers. Moreover, it has been used for underwater construction.
Grout has a major effect on the properties of produced PAC and well defined grout
controls the properties of resulted PAC. The effect of types and amount of powder
materials, admixtures, sand and water content on the properties of fresh and hardened
grout for the production of PAC have been investigated. Tests on hardened grout and
PAC properties have also been carried out to investigate the most important effects. A
correlation between hardened properties of grout and PAC has also been analyzed.
Grout rheology using four different gradation sands at two different cement-sand and at
different w/c ratios ratios has been identified experimentally; no added chemical
admixtures or mineral additives had first employed, then superplasticizer (SP) was
added at 2% and 1%, and finally a combination of 1% SP and pulverized fuel ash (Pfa)
at 20% of the cement weight was employed for all mixes. Grout tests have included two
point workability tests by the Viskomat NT, flow time funnel test, Colcrete flow meter
test, and water bleeding test. After that, eighteen grout mixes with high workability were
produced using three different sands at three w/c ratios and two c/s ratios with 1% SP
and Pfa at 20% of the cement weight were designed. Eighteen hardened grout and PAC
then produced and their compressive strength and sorptivity were tested.
Grout rheology can be defined by the rheology of cement paste employed and the
internal distance between sand particles. The effect of sand surface texture on grout
rheology is important at very low internal distances. Fresh grout yield stress is the most
important property which gives the same degree of sensitivity for all grouts regardless
the material type and content used in the mix. There are strong relations between
compressive strength of grout and PAC, but less correlation between them in sorptivity
test because of the effect high quantity of coarse aggregate of PAC. Sorptivity of PAC is
low comparing with different kinds of concrete suggesting its advantage for underwater
construction. / Libyan High Education Ministry
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Novel Acoustic Sensing Method for In-situ Concrete Mechanical Properties MonitoringZhihao Kong (17499687) 30 November 2023 (has links)
<p dir="ltr">In this research, a novel acoustic sensor with a waveguide is made to induce the local volumetric resonance of concrete material. The sensor is embedded in fresh concrete and monitors the in-place elastic modulus and strength development of the concrete. The resonant peak of the EMI spectrum of the sensor is governed by the concrete material in the proximate area of the sensor. The sensor itself does not affect the position of the resonant peak.</p><p dir="ltr">This research covers theoretical demonstration, sensor design and prototyping, remote testing systems, experimental study, and machine learning. Current work demonstrated the sensor successfully produced the resonant peaks that are related to the concrete curing process (R-square=0.86 for lab testing and R-square=0.64 for field testing); however, the sensitivity (S=1.00 Hz/psi) of the resonant frequency is not sufficient for practical application.</p><p dir="ltr">Machine learning algorithms were employed to map the EMI spectra to concrete strength profile. Several existing architectures were explored and evaluated. A novel machine learning scheme was proposed and successfully improved the accuracy of prediction. The algorithm is also able to handle real-time data with decent generalization among diverse concrete mixtures.</p><p dir="ltr">The integration test for the sensing system, including the sensor, the data collection device, the data pipeline, and the trained machine learning models, was performed in field testing of eight States. The averaged MAPE of the field prediction results is 23.43% for field structures and 16.13% for companion beam samples.</p><p dir="ltr">The knowledge produced during this study further advanced the application of EMI sensors in the NDE of concrete material. The EMI resonator tailored for local structural resonance is reported in this study for the first time. The EMI data processing algorithm using machine learning that is generalizable among various concrete mixtures is employed in this study for the first time. This study would be helpful for the real-world application of the EMI technique in the NDE of concrete and other phase-changing materials.</p>
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Framtidens klimatvänliga bindemedel i betong : En analys av naturliga puzzolaner som tillsatsmaterial / Future climate-friendly binders in concrete : An analysis of natural pozzolans as supplementary cementitious materialsSjödin, Sabine, Fredin, Elsa January 2023 (has links)
Betong är ett av världens mest använda byggnadsmaterial, men kan också vara en stor miljöbov. Cementklinker är en betydande beståndsdel i betong som vid tillverkning frigör stora mängder koldioxid, av den anledningen optimeras betongrecept idag genom att ersätta en del av cementen med flygaska som är en restprodukt från kolkraftsindustrin. I takt med att samhället rör sig mot en fossilfri produktion beräknas tillgången till flygaska att avta och material med liknande egenskaper undersöks som alternativa bindemedel i betong. Syftet med studien är att, genom litteraturstudier och laboratoriska tester, undersöka huruvida naturliga puzzolaner kan ersätta mängden flygaska i en cementsammansättning utan att försämra betongens hållfasthetsegenskaper. Tryckhållfastheten samt hållfasthetsutvecklingen har undersökts hos 150x150x150 mm provkuber med varierande mängd flygaska samt vulkanaska av isländsk pimpsten respektive jordanska tuffer. Målet med studien är att minska mängden, eller helst ersätta hela andelen flygaska i en klimatförbättrad betongsammansättning. De laboratoriska testerna har utförts enligt svensk standard där totalt 48 provkroppar gjutits. Referenskuben i undersökningen består av 80% portlandkalkstencement och 20% flygaska. Totalt har 6 olika kombinationer av provkuber gjutits där andelen flygaska ersätts med 20%, 15% eller 10% vulkanaska. Vardera provkub har utsatts för tryckhållfasthetsmätning efter 2, 7 samt 28 dygn. Resultatet av provtryckningen visade att provkuberna innehållande isländsk pimpsten gav en ökad eller oförändrad hållfasthet vid samtliga mätningar, jämfört med referenskuben. Provkuberna innehållande jordanska tuffer medförde däremot en reducering av hållfastheten vid samtliga mätningar, jämfört med referenskuben. Provkuberna innehållande vulkanaska från isländsk pimpsten gav högst sluthållfasthet då ingen flygaska förekom i sammansättningen och något sämre värden vid inblandning av flygaska, till skillnad från provkuberna innehållande vulkanaska från jordanska tuffer som utan flygaska i princip stannade av i sin hållfasthetstillväxt efter 7 dygn. Skillnaden i resultatet mellan vulkanaska av pimpsten respektive tuffer antyder att vilken typ av material det är samt dess ursprung har betydelse för hur det presterar som bindemedel i betong. / Concrete is one of the most widely used building materials in the world, but it can also be a major environmental culprit. Cement clinker is a significant component of concrete that releases large amounts of carbon dioxide during production. For this reason, concrete recipes are now optimized by replacing some of the cement with fly ash, which is a byproduct from the coal power industry. As society moves towards fossil-free production, the availability of fly ash is expected to decrease, and materials with similar properties are being investigated as alternative binders in concrete. The purpose of the study is to investigate, through literature review and laboratory tests, whether natural pozzolans can replace the amount of fly ash in a cement composition without deteriorating the strength properties of the concrete. The compressive strength and strength development have been studied on 150x150x150 mm test cubes with varying amounts of fly ash and volcanic ash from Icelandic pumice and Jordanian tuffs. The goal of the study is to reduce the amount, or preferably replace the entire portion, of fly ash in a climate-improved concrete composition. The laboratory tests have been performed according to Swedish standards, where a total of 48 test specimens have been cast. The reference cube in the study consists of 80% Portland limestone cement and 20% fly ash. A total of 6 different combinations of test cubes have been cast, where the proportion of fly ash is replaced with 20%, 15%, or 10% volcanic ash. Each test cube has been subjected to compressive strength measurement after 2, 7, and 28 days. The results of the compression testing showed that the test cubes containing Icelandic pumice provided increased or unchanged strength at all measurements, compared to the reference cube. However, the test cubes containing Jordanian tuffs resulted in a reduction of strength at all measurements, compared to the reference cube. The test cubes containing volcanic ash from Icelandic pumice provided the highest final strength when no fly ash was present in the composition, and slightly lower values when fly ash was added, unlike the test cubes containing volcanic ash from Jordanian tuffs which essentially plateaued in their strength development after 7 days without fly ash. The difference in results between volcanic ash from pumice and tuffs suggests that the type and origin of the material are significant factors in how they perform as a binder in concrete.
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Jämförelser av tryckhållfasthet och uttorkning av betong med lägre klimatpåverkanGustavsson, Elias, Dahlberg, Axel January 2024 (has links)
Betong är ett av de vanligaste byggnadsmaterialen och har goda egenskaper som hög beständighet, god formbarhet och lång livslängd. Huvudbeståndsdelen cement orsakar däremot en negativ klimatpåverkan där tillverkningen av bindemedlet cement står för cirka 8 procent av världens koldioxidutsläpp. För att minska de stora koldioxidutsläppen finns det alternativa bindemedel där de vanligaste är flygaska och masugnsslagg, vilket är restprodukter från kolkraft- och stålindustrin. Alternativa bindemedel är det mest effektiva sättet på kort sikt att minska klimatpåverkan. Däremot kan inte de alternativa bindemedlen ersätta cement helt utan att tryckhållfastheten försämras, vilket gör att upp till 20 procent vanligtvis ersätts. För att byggbranschen i en större utsträckning ska tillämpa betong med lägre klimatpåverkan är det viktigt att egenskaperna är minst lika bra som hos traditionell betong. Uttorkningsegenskaperna är av stor vikt då uttorkningstiden är styrande för applicering av golvmaterial. När det kommer till hållfasthet tillverkas idag komponenter med överkvalité, vilket gör att en onödigt stor mängd cement används. Ett klimatsmart alternativ skulle vara att ändra nuvarande norm på klassificeringen av hållfastheten. Dagens norm klassificerar hållfastheten vid 28 dygn efter gjutning. Betong fortsätter dock att öka i hållfasthet efter 28 dygn, men ökningen är inte stor hos traditionell betong, medan betong med alternativa bindemedel fortsätter att härda i en högre grad efter 28 dygn. Skulle en klassificering av hållfastheten hos betong med lägre klimatpåverkan bestämmas i ett senare skede som 56 eller 91 dygn, skulle konstruktionens krav fortfarande uppfyllas samtidigt som mängden cement kan reduceras. Idag behöver byggprojekt vänta på uttorkningstiden, vilket medför att ett projekt sällan är färdigt redan vid 28 dygn. Det gör att byggnaden inte belastar betongplattan fullt ut vid 28 dygn och den potentiella hållfastheten behöver inte uppfyllas förrän i ett senare skede. Om hållfasthetsklassen sänks tillkommer dock ett högre vattencementtal, vilket gör att krav på uttorkningsegenskaperna ökar. Tillsammans med Skanska jämfördes i föreliggande arbete betongrecept med lägre klimatpåverkan i tryckhållfasthet och uttorkning. Det var två Portlandkompositcement av typen CEM II/B-M, med cirka 20 procent slagg eller flygaska. De jämfördes även mot en referensbetong av typen CEM II/A-LL. Provkropparna gjöts vid Skanskas betonglabb i Farsta och testades sedan för uttorkning och hållfasthet av auktoriserade företag. Studien tyder på att det inte finns någon anledning att välja bort slagg eller flygaska när det kommer tilltryckhållfasthet och uttorkning. Det går att argumentera för att betong med alternativa bindemedel har högre hållfasthet vid 7 och 28 dygn i jämförelse med traditionell betong i föreliggande arbete, där slaggbaserad betong är cirka 16 procent högre och betong med flygaska är cirka 5 procent högre. Hållfasthetsutvecklingen från 28 till 91 dygn tyder på att betong med alternativa bindemedel ökar med cirka 12 procent medan traditionell betong nästan stannar av, där hållfasthetsutvecklingen är cirka 4 procent. Det går att argumentera för att slaggbaserad betong har cirka 2 och 5 procent snabbare uttorkning vid 35 och 85 dygn i jämförelse med traditionell betong, medan betong med flygaska tenderar att torka ut minst lika bra vid 35 dygn och cirka 3 procent snabbare vid 85 dygn. Resultaten tyder på att vid en minskad hållfasthetsklass skulle betong med lägre klimatpåverkan inte medföra samma förlängda uttorkningstid som en traditionell betong. En klassificering i ett senare skede som 56 eller 91 dygn för betong med lägre klimatpåverkan indikerar på att konstruktionens krav fortfarande skulle uppfyllas, cementanvändningen reduceras och klimatpåverkan minskas. / Concrete is one of the most common building materials and possesses favorable properties such as high durability, good workability, and long lifespan. However, its main component, cement, has a negative climate impact, with cement production accounting for approximately 8 percent of the world's carbon dioxide emissions. To reduce these CO2 emissions alternative binders can be used. The most common being fly ash and blast furnace slag, which are by-products of the coal power and steel industries. Alternative binders are the most effective way to reduce climate impact. Alternative binders cannot completely replace cement without lose strength, which means that up to 20 precent is usually replaced. For the construction industry to more widely adopt concrete with lower climate impact, it is important that the properties are at least as good as those of traditional concrete. Drying properties are crucial since drying time dictates the application of flooring materials. In terms of strength, components are currently manufactured with high qualities, leading to unnecessary large amounts of cement being used. A climate-smart alternative would be to change the current norm for strength classification. Today strength classifies at 28 days after casting. Concrete continues to gain strength beyond 28 days, but the increase is not significant in traditional concrete, whereas concrete with alternative binders continues to cure to a greater extent after 28 days. If the strength classification were determined at a later stage, such as 56 or 91 days, the construction's requirements would still be met while reducing the amount of cement used. Today construction projects need to wait for the drying time, meaning a project is rarely completed at 28 days. This means the building does not fully load the concrete slab at 28 days, and the potential strength does not need to be achieved until a later stage. However, if the strength class is lowered the demands on drying increases. In collaboration with Skanska, concrete with lower climate impact was compered in terms of strength and drying. Two Portland composite cements of the type CEM II/B-M, around 20 percent of slag or fly ash, were compared to a reference concrete of the type CEM II/A-LL. The test specimens were cast at Skanska's concrete lab in Farsta and tested for strength and drying by authorized companies. The study suggests that there is no reason to avoid slag or fly ash concerning compressive strength and drying. It can be argued that concrete with alternative binders has higher strength at 7 and 28 days compared to traditional concrete, with slag-based concrete being approximately 16 percent stronger and fly ash concrete about 5 percent stronger. The strength development from 28 to 91 days indicates that concrete with alternative binders increases by about 12 percent, while traditional concrete almost levels off, with a strength development of about 4 percent. It can also be argued that slag-based concrete has about 2 and 5 percent faster drying at 35 and 85 days compared to traditional concrete, while fly ash concrete tends to dry at least as well at 35 days and about 3 percent faster at 85 days compared to traditional concrete. The results indicate that with a reduced strength class, concrete with lower climate impact would not entail the same extended drying time as traditional concrete. Classification at a later stage, such as 56 or 91 days, for concrete with lower climate impact indicates that the construction's requirements would still be met, cement usage would be reduced, and climate impact minimized.
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Estudio de la resistencia a la compresión y permeabilidad en unidades de albañilería de tierra reforzada con estiércol de Equus asinus y estearato de calcioCampos Manayay, Ernesto Alonso January 2024 (has links)
La Tierra es uno de los recursos constructivos más empleados globalmente. Sin embargo, su aplicación en áreas propensas a terremotos y su susceptibilidad a la erosión por agua son aspectos que generan inquietud entre los ingenieros.
La investigación se enfocó en integrar estiércol de Equus asinus en la producción de unidades de tierra reforzada con el fin de aumentar su resistencia a la compresión y tracción, además de explorar el efecto de aplicar estearato de calcio en su superficie para disminuir su permeabilidad.
Se llevaron a cabo pruebas tanto en campo como en laboratorio para elegir la cantera de suelo y el agua a emplear. Se analizaron las características mecánicas (compresión y tracción) de los bloques de tierra reforzada según lo estipulado en la norma E.080. Además, se sugirieron pruebas de absorción e inundación simulada para evaluar la permeabilidad.
Los resultados indicaron un aumento del 19% en la resistencia a la compresión y un 50% en la resistencia a la tracción a nivel de unidades, y del 20% y 22% respectivamente a nivel de muros. El uso de estearato de calcio como recubrimiento permitió que las muestras absorbieran temporalmente agua sin desintegrarse, retrasando su deterioro. Por último, se determinó un aumento del 19.20% del precio de asentamiento con unidades de tierra reforzada y recubrimiento con estearato de calcio.
En conclusión, la adición de estiércol de Equus asinus al 6% y el recubrimiento de estearato de calcio mejoran tanto las propiedades mecánicas como las hidrofóbicas de las unidades de tierra reforzada, con un pequeño aumento en su costo de producción. / Earth is one of the most commonly used construction materials. However, its application in earthquake-prone areas and susceptibility to water erosion are concerns for engineers.
This research aimed to enhance the compression and traction resistance of earth units by integrating Equus asinus manure into their production. Additionally, it explored the effectiveness of applying calcium stearate to the surface to reduce permeability.
Field and laboratory tests were conducted to select the soil quarry and water source.
Mechanical properties (compression and traction) of the reinforced earth blocks were analyzed according to the E.080 standard. Furthermore, absorption and simulated flooding tests were suggested to evaluate permeability.
Results indicated a 19% increase in compression resistance and a 50% increase in traction resistance at the unit level, and 20% and 22%, respectively, at the wall level. Coating with calcium stearate allowed samples to temporarily absorb water without disintegration, thus delaying deterioration. Lastly, a 19.20% increase in settlement price was observed with reinforced earth units and calcium stearate coating.
In conclusion, the addition of 6% Equus asinus manure and calcium stearate coating improve both the mechanical and hydrophobic properties of reinforced earth units, albeit with a slight increase in production cost.
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Predicción de la resistencia a la compresión del concreto usando redes neuronales artificialesBernilla Rodriguez, David Henry January 2024 (has links)
El concreto es el material de construcción más ampliamente utilizado en la actualidad debido a su excepcional capacidad para resistir fuerzas de compresión, comúnmente denominadas como f'c. La obtención del valor de f'c del concreto involucra la realización de diversos ensayos, siendo el ensayo a compresión simple o uniaxial en probetas de concreto el más comúnmente empleado, evaluando la resistencia a diferentes intervalos de tiempo. Lamentablemente, estas probetas suelen ser desechadas al aire libre, contribuyendo a la contaminación ambiental. En esta investigación, se enfoca en la predicción del valor de f'c del concreto a los 28 días mediante un modelo predictivo basado en redes neuronales artificiales. Los datos de entrada comprenden propiedades de los agregados, tipo de cemento y las proporciones de sus componentes, como agua, cemento y agregados. El único dato de salida es el valor real de f'c obtenido en el ensayo de compresión simple. Estos datos se recopilaron de varios laboratorios en el norte de Perú. La red neuronal se construyó utilizando TensorFlow de Google, con dos capas ocultas que constan de 16 y 8 neuronas respectivamente, y se entrenó durante 450 épocas. Se obtuvo una exactitud en la predicción mayor al 90% en el rango de 210 a 335 kg/cm². / Concrete is currently the most widely used construction material due to its exceptional ability to withstand compressive forces, commonly referred to as CS. Determining the CS value of concrete involves conducting various tests, with the uniaxial or simple compression test on concrete specimens being the most employed, assessing resistance at different time intervals. Unfortunately, these test specimens are often discarded outdoors, contributing to environmental pollution. This research focuses on predicting the CS value of concrete at 28 days using a predictive model based on artificial neural networks. Input data include aggregate properties, cement type, and their component proportions such as water, cement, and aggregates. The only output data is the actual CS value obtained from the simple compression test. This data was collected from multiple laboratories in northern Peru. The neural network was constructed using Google's TensorFlow, with two hidden layers consisting of 16 and 8 neurons, respectively, and trained for 450 epochs. Prediction accuracy exceeded 90% in the range of 210 to 335 kg/ cm².
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Evaluación del nivel de la resistencia a la compresión del concreto fabricado en obras por autoconstrucción en la ciudad de Chiclayo, provincia de Chiclayo, departamento de Lambayeque en el año 2020Guerrero Olano, Renzo Mauricio January 2023 (has links)
La autoconstrucción en el Perú es uno de los problemas más frecuentes de modo que mi investigación tiene como fin principal medir cual es la resistencia a la compresión del concreto realizado en obras autoconstruidas en la ciudad de Chiclayo y así determinar si el concreto elaborado en las autoconstrucciones cumple con criterios mínimos del RNE. Del total de 45 autoconstrucciones evaluadas, se tiene que el valor mínimo de resistencia a la compresión obtenido a los 28 días fue de 70.45 kg/cm2 y el valor más alto fue de 150.91kg/cm2, siendo comparadas con una resistencia de diseño de 210 kg/cm2 y 175 kg/cm2. También se evaluó la consistencia del concreto, obteniendo como asentamiento representativo 7.25’’ pulgadas siendo una mezcla demasiado fluida y no cumpliendo con el rango de asentamiento aceptable. En las autoconstrucciones en la ciudad de Chiclayo la baja resistencia a la compresión obtenidas y los altos valores de asentamiento del concreto se deben a que se verifico el uso de dosificaciones inadecuadas, elevada relación de agua/ cemento, tiempos de mezclado demasiado cortos, mano de obra inadecuada y finalmente una compactación incorrecta. / Self-construction in Peru is one of the most frequent problems so the main purpose of my research is to measure the compressive strength of the concrete made in self-built works in the city of Chiclayo and thus determine if the concrete made in self-construction meets minimum RNE criteria. Of the total of 45 self-constructions evaluated, the minimum value of compression resistance obtained after 28 days was 70.45 kg/cm2 and the highest value was 150.91kg/cm2, being compared with a design resistance of 210 kg/cm2 and 175 kg/cm2. The consistency of the concrete was also evaluated, obtaining a representative slump of 7.25'' inches, being a mixture that was too fluid and not complying with the acceptable slump range. In the self-constructions in the city of Chiclayo, the low compressive strength obtained and the high slump values of the concrete are due to the use of inadequate dosages, high water/cement ratio, too short mixing times, labor of inadequate work and finally incorrect compaction.
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Cement Reduction in Sustainable Building BlocksBogren, Linn January 2024 (has links)
The use of cement in the building industry accounts for a large part of the world's CO2-emissions. In the developing part of the world where materials are costly and labour is cheap, cement is expensive. In Nepal, a country which is frequently hit by earthquakes, low-cement-content building blocks are already being made and research on how to reduce the cement content further is currently going on. The manufacturing process for these blocks varies significantly, so a method to predict block strength easily and implement cost-effective quality control could substantially enhance production quality. The purpose of this study is to investigate how to predict the strength of building blocks using the water content, cement content and bulk density. Additionally, it examines whether bulk density could serve as a reliable indicator of strength, which could simplify quality control by allowing blocks to be weighed. This, together with an evaluation of the production site performance, is used to calculate the theoretical improvement potential and a proposed cement reduction. Through experiments, the compressive strength was measured for blocks of mixes with different cement percentages under various water content conditions, resulting in blocks with differing bulk densities. This data was used to create a model that predicts the compressive strength. Field visits to five sites were conducted to evaluate the current performance and this data was used to calculate the improvement potential. The results show the importance of water for the workability of the mix and in turn the compressive strength of the blocks. More water and more material into the mold lead to an increase in the strength and the theoretical improvement potential for cement reduction is 50\% by only these measures. The bulk density is a promising indicator of the compaction and compressive strength and weighing the blocks at creation could potentially reduce the variability in the strength of the blocks.
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