Rammed Earth Construction: A Proposal for a Statistical Quality Control in the Execution Process

Unlike other common contemporary construction materials such as concrete, mortars, or fired clay bricks, which are widely supported by international standards and regulations, building with rammed earth is barely regulated. Furthermore, its quality control is usually problematic, which regularly encourages the rejection of this technique. In the literature, many authors have suggested ways to safely build a rammed earth wall, but only a few of them have delved into its quality control before and during the construction process. This paper introduces a preliminary methodology and establishes unified criteria, based in a statistical analysis, for both the production and the quality control of this constructive technique in cases dealing with both samples and walls

KARAKTERIZACIJA CEMENTOM STABILIZIRANIH NOSIVIH SLOJEVA KOLNIČKIH KONSTRUKCIJA METODOM ULTRAZVUKA

Performance of ultrasonic pulse velocity (UPV) in hydraulically bound mixtures is examined as a non-destructive testing, in order to estimate its potential for pavement material characterization. Test results show that an increase in cement content results in an increase in UPV values. Increase in steel slag aggregate content results in a decrease in UPV values. Analyses of relationship between UPV values and strengths have shown strong polynomial relationship. For UPV values ranging 2 ÷ 3,2 km/s cement stabilized material can be classified as appropriate for usage in road construction. Test results have shown good potential for UPV measure as non-destructive method in cement stabilized material characterization.U radu je ispitana mogućnost primjena metode mjerenja brzine ultrazvučnog impulsa kao nerazorne metode pri karakterizaciji hidraulički vezanih materijala kolničkih konstrukcija. Rezultati ispitivanja su pokazali da povećanje količine cementa rezultira povećanjem vrijednosti brzine ultrazvuka. Povećanje udjela čeličanske zgure u agregatu rezultira smanjenjem vrijednosti brzine ultrazvuka. Analiza odnosa brzine ultrazvuka i čvrstoće materijala pokazala je jaku polinomnu vezu. Za vrijednosti brzine ultrazvuka u rasponu od 2 ÷ 3,2 km/s cementom stabilizirani materijal može biti klasificiran kao prikladan za uporabu u cestogradnji. Rezultati ispitivanja pokazali su moguću uporabu metode mjerenja ultrazvuka kao nerazorne metode pri karakterizaciji cementom stabiliziranih materijala kolničke konstrukcije

ASSESS MATERIAL PROPERTIES OF CONCRETE USING COMBINED NDT METHODS

The aim of this research is to assess the material properties of concrete like modulus of elasticity, compressive strength, and Poisson’s ratio using various nondestructive Testing (NDT) methods like Ultrasonic Pulse Velocity (UPV) and Rebound Hammer (RH). Assessment of material properties of concrete is very important as they are used for structural design process. Various NDT methods are applied to ensure the quality of concrete specimens but they can also be used to find material properties. UPV is a NDT method which is used to test the internal condition of the concrete specimen. RH is a surface hardness testing method and can be used to test the homogeneity of the specimen. For this study, several batches of concrete samples with three different design strengths of 6000 psi, 8000 psi, and 12000 psi were casted. Modulus of elasticity and Poisson’s ratio were calculated from UPV P-wave and S-wave velocities. A Nomogram was developed by combining the longitudinal ultrasonic pulse velocities, rebound numbers, and compressive strengths measured from UPV, RH, and compressive strength tests respectively. This combined NDT correlation curve (Nomogram) can be used to estimate compressive strength of concrete if UPV and rebound values are known. The accuracy of these NDT methods were determined by comparing estimated strength to the actual strength. Furthermore, the effect of moisture content on UPV and rebound values was reviewed and also studied dynamic modulus of elasticity and its relation with static modulus of elasticity of the concrete was investigated for better understanding

Ultrasound wave propagation in retaining system for soil works

Orientadores: Raquel Gonçalves, Cinthya Bertoldo PedrosoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia AgrícolaResumo: Com o crescente aumento de obras civis em áreas de difícil acesso e topografia irregular no Brasil, a utilização de aterros e de contenção de encostas, associados a peças pré-fabricadas de concreto como elemento estrutural, vem ganhando cada vez mais espaço. O Lock and Load é um sistema de contenção formado pela união de dois elementos, um painel e um contraforte, podendo ser pré-moldado ou fabricado in loco. O conjunto tem sido largamente utilizado em situações de corte e de aterro, porém não há metodologia de inspeção e de acompanhamento da qualidade das peças (placas e contraforte) após sua desmoldagem e instalação. Técnicas não destrutivas, baseadas em propagação de ondas de ultrassom, vêm sendo cada vez mais utilizadas para avaliação da homogeneidade do concreto, para inferência de propriedades mecânicas e para inspeção de descontinuidades ou defeitos não visíveis externamente. Sendo assim, o objetivo dessa pesquisa foi avaliar a viabilidade de serem definidos parâmetros ideais para o uso do ensaio de ultrassom no acompanhamento e na inspeção de peças do sistema Lock and Load e, com o uso desses parâmetros, avaliar a viabilidade de inferir a qualidade das peças por meio do ensaio aplicado diretamente nas mesmas. Para atingir os objetivos incialmente foi avaliada a metodologia de inspeção, por ultrassom, considerando o tipo de medição (direta e indireta), o tipo de transdutor (plano e exponencial), o acoplamento e a frequência dos transdutores (25, 45 e 80 kHz). Para a análise de modelos de inferência da qualidade do material por meio do ensaio de ultrassom, foram moldados corpos de prova produzidos com agregados graúdos de quatro diferentes origens mineralógicas (basalto, calcário, gnaisse e granito), os quais foram ensaiados por ultrassom e de forma destrutiva em compressão, para a determinação da resistência e da rigidez, parâmetros adotados para representar a qualidade do material. Por fim foi testada a aplicabilidade do uso do ensaio de ultrassom diretamente nas peças pré-moldadas do sistema na inferência da qualidade do concreto. Os resultados permitiram definir o transdutor de faces planas e de frequência 45 kHz como mais adequado para uso na classificação e nas inspeções visando o controle de qualidade do sistema Lock and Load antes da instalação (ensaio direto) ou após instalado (ensaio indireto). Os modelos de predição da resistência e da rigidez foram estatisticamente significativos para os agregados de todas as origens mineralógicas e o ensaio mostrou viabilidade para ser utilizado na classificação e na inspeção das placas e dos contrafortes, considerando a rigidez e a resistênciaAbstract: The increasing civil works in areas with difficult access and irregular topography in Brazil are producing the use of embankments and slope containtion, associated with prefabricated concrete parts as a structural element. Lock and Load is a containment system formed by the union of two elements, a panel and a buttress, which can be prefabricated or manufactured on site. The set has been widely used in cutting and landfill situations, but there is no methodology for inspection and quality monitoring of its components (plates and buttress) after its demoulding and installation. Nondestructive techniques based on ultrasonic wave propagation are increasingly being used to evaluate concrete homogeneity, to infer mechanical properties and to inspect discontinuities or defects not externally visible. Thus, the objective of this research was to evaluate the feasibility of defining ideal parameters for the use of the ultrasound test in monitoring and inspecting the components of the Lock and Load system and, using these parameters, to evaluate the feasibility of inferring the quality of its components using the test applied directly to them. To reach the objectives, initially the ultrasound inspection methodology was evaluated, considering the type of measurement (direct and indirect), the type of transducer (flat and exponential), the coupling and the transducers frequency (25, 45 and 80 kHz). For the models analysis, aiming the inference of the material quality using the ultrasound test, specimens were molded with coarse aggregates from four different mineralogical origins (basalt, limestone, gneiss and granite), which were test with ultrasound and with static method (compression) to determine the strength and stiffness, which are parameters adopted to represent the material quality. Finally it was tested the applicability of the ultrasound test applied directly on the prefabricated system to infer concrete quality. The results allowed us to define the 45 kHz frequency flat transducer as the most suitable for use in classification and inspections aiming at quality control of the Lock and Load system before installation (direct test) or after installation (indirect test). The prediction models of strength and stiffness were statistically significant for aggregates of all mineralogical origins and the test showed feasibility to be used in the classification and inspection of plates and buttresses, considering stiffness and strengthDoutoradoMétodos não Destrutivos Aplicados a Materiais, Estruturas e ÁrvoresDoutor em Engenharia Agrícol

Structure, strength and defect characterisation of cement based materials.

In cement based systems, the residual stresses are created by internal expansion. This provides toughening by the release of the residual stresses as the macro-crack propagates. While circumstantial evidence of the residual stresses exist (e.g. micro-crack formation leading to permanent deformation in flexural tests), it is very difficult to observe the mechanism in action. The quantitative estimate of the changes occurring in such cement-based systems is challenging due to the anisotropy and complexity of the material. Non-Destructive Testing (NDT) techniques were used in this research to observe the mechanism in action. An ultrasound technique is used to examine strength development and an acoustic emission (AE) technique is used to examine micro-structural changes, micro-cracks, crack initiation, crack propagation, crack arrests and crack bridging in plain concrete samples including samples containing admixtures and waste materials. The NDT techniques were found to be accurate in being able to measure compressive strength, with good correlation between both standard mechanical testing and NDT techniques. It was shown that admixtures could be effectively used to alter the properties of a curing cement mortar. This work has also demonstrated that ultrasound can be successfully used to determine the compressive strength of concrete from an early age. The ability to pre-determine the strength of concrete through correlation with NDT test parameters may reduce the time spent waiting on concrete to set and to obtain results using standard mechanical testing methods. The findings in this research present the effect admixtures had on the curing process of the cement based material. The introduction of certain additives into mortars have demonstrated an increase in both the rate of initial hardening and the magnitude of the compressive strength attained over the curing period depending on the mixture specification. The additives considered have been shown to actively alter and enhance the chemical process of curing from the start of hydration. Some additives that accelerate the curing process (accelerators) were found to lower the compressive strength of concrete using the ultrasound technique. Additives that caused an increase in the final strength of mortar also increased its toughness. The significant contributions in this research enabled observation of micro-structural changes and failure behaviour under compressive and flexural loading conditions on an on-line basis. The results obtained are encouraging and lead to increased understanding of cracking mechanisms in concrete containing various types of additives and aggregates. The application of the AE technique allowed the failure of interfacial bonding to be observed. The variation of the aggregate size and its effect on the monitored waveforms was established and the parameters in the AE signals are directly related to crack propagation (grain bridging/micro-mechanism) and strength of interfacial bonding. These findings have greatly contributed to the understanding of the concrete behaviour under complex conditions where no other technique could provide such valuable information on an online basis

New non-destructive testing techniques based on mechanical waves: Development and application to damage characterization on non-homogeneus materials

Tesis por compendioEsta tesis doctoral se encuentra desarrollada en los ámbitos de materiales, ensayos no destructivos y procesado de señal. Su propósito es aportar nuevas técnicas no destructivas centrándose tanto en su desarrollo como en su aplicación a sistemas reales. La evaluación de durabilidad y daño en materiales no homogéneos es el eje central de este documento, articulándolo en dos capítulos fundamentales. En primera instancia se evalúa el comportamiento del cemento reforzado con fibra de vidrio bajo esfuerzo de flexión. Múltiples señales ultrasónicas fueron adquiridas en todo el proceso de deformación de los elementos implementando una nueva técnica de adquisición multifrecuencia. En la fase posterior a la adquisición se determinaron parámetros lineales y no lineales de las señales ultrasónicas pulsadas correlacionando dichos parámetros con las curvas tensión - deformación descritas por los elementos ensayados. En el último bloque se expone el análisis de espectroscopía por impacto sobre probetas de mortero dañadas química y térmicamente. Se profundizó sobre el comportamiento dinámico no-lineal e histéretico de los elementos de mortero. El análisis del ablandamiento del módulo dinámico con el incremento de la amplitud de excitación es un tema de gran interés para la evaluación de daño, siendo la técnica actual dependiente de la adquisición de múltiples señales. En este contexto, se propone nueva técnica de procesado de señal capaz de extraer parámetros de esta naturaleza a partir de una única señal.Aquesta tesi doctoral està desenvolupada als àmbits de materials, assajos no destructius i processament de senyals. El seu propòsit és aportar noves tècniques no destructives, centrades tant en el seu desenvolupament com en la seua aplicació a sistemes reals. L'avaluació de durabilitat i dany en materials no homogenis és l'eix central d'aquest document, format per dos capítols fonamentals. En primer lloc s'avalua el comportament del ciment reforçat amb fibra de vidre sotmès a esforç de flexió. Diverses senyals ultrasòniques van ser adquirides durant tot el procés de deformació dels elements que implementa una nova tècnica d'adquisició multifreqüència. En la fase posterior a l'adquisició es van determinar paràmetres lineals i no lineals de les senyals ultrasòniques polsades que correlacionen aquests paràmetres amb les corbes de tensió-deformació descrites pels elements assajats. Al tercer bloc s'exposa l'anàlisi d'espectroscòpia per impacte en provetes de morter malmeses químicament i tèrmicament. Es va aprofundir en el comportament dinàmic no lineal i histerètic dels elements de morter. L'anàlisi de l'estovament del mòdul dinàmic amb l'increment de l'amplitud de l'excitació és un aspecte molt interessant per a l'avaluació de dany, tècnica que actualment depèn de l'adquisició de diverses senyals. En aquest context, es proposa una nova tècnica de processament de senyal capaç d'extraure paràmetres d'aquesta natura a partir d'una única senyal.This doctoral thesis is developed in materials, Non-Destructive Testing (NDT) and signal processing fields. Its purpose is to make a contribution in new non destructive techniques focusing in its development and application to real systems. Durability and damage evaluation in non-homogeneous materials is the keystone of this document, assembling the structure in two main chapters. In the first instance the behaviour of Glass-fiber Reinforced Cement under bending test is evaluated. Multiple ultrasonic signals during the deformation process of the specimens were acquired, implementing a new multi-frequency acquisition technique. After the acquisition stage, linear and non-linear parameters were calculated from the pulsed ultrasonic signals correlating those parameters with the stress strain curve described during the test. In the third chapter, the impact spectroscopy analysis applied to chemical and thermal damaged mortar samples is exposed. The non-linear histeretic behaviour of the mortar specimens was studied more in depth. The analysis of the dynamic modulus softening with increment of the excitation amplitude is a hot spot at this moment for damage evaluation, being the current technique depending on the multiple signals acquisition. In this context, a new technique is proposed which allows a non-linear parameters extraction from a single reverberation signal.Genovés Gómez, V. (2018). New non-destructive testing techniques based on mechanical waves: Development and application to damage characterization on non-homogeneus materials [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/114799TESISCompendi

Evaluation of non-destructive techniques for mechanical characterisation of earth-based mortars in masonry joints

In this paper, the use of non-destructive tests for the mechanical characterisation of earth-based mortars in masonry joints is discussed. Four testing methods, namely the penetrometer, Schmidt hammer, pendulum hammer and scratch test, originally developed for other types of mortar, are reviewed. The methods are applied to the earth-based mortars at the Wupatki Pueblo archaeological site, in Arizona, US. The outcomes of the experimental programme allowed to assess the reliability of the methods and to identify their limitations. Finally, the methods are compared in terms of six qualitative indicators, namely easy-of-use, consistency of results, range and granularity of results, respect towards cultural value, depth of investigation under the visible surface and versatility in application. Overall, the penetrometer test is recommended as the preferable method to characterise the mechanical performance of earth-based mortars.FCT - Fuel Cell Technologies Program(2022.09946

Nondestructive Condition Assessment of Civil Infrastructure Using Ultrasonic Technique

Civil Infrastructure controls the way people live by providing safe passage and shelter across the entire globe. Since safety leads the concern in infrastructure, it is essential to ensure that these structures have been adequately tested and analyzed periodically. Testing these structures can be extremely expensive when parts are required to be removed to capture the flaw, which is why nondestructive testing (NDT) continues to grow in demand since it can evaluate the structural component in-situ without causing any damage. Ultrasonic testing (UT) helps to adequately sustain and advance the safety in existing and future infrastructure across the globe. Continual advancement and use of UT methods for the application of condition assessment in the field of civil infrastructure can provide a cheaper alternative to other conventional practices. This report focuses on the UT methods of NDT and aims to provide an in-depth literature review of the different testing styles. Ultrasonic Pulse Velocity, Ultrasonic Pulse Echo, Semi-direct and Indirect testing, Time of flight Diffraction, Phased Array ultrasonic testing, are some of the NDT methods commonly used and discussed in the report. These techniques are routinely being applied to the condition assessment of concrete, steel, and timber structural members including the assessment of debonding between rebar cage and surrounding concrete in reinforced concrete structural members. With the techniques already established, the goals of the NDT industry are to make the techniques safer, cost effective, and modifying the systems to integrate a more accessible process