No description available.

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 66-68.

Avhandling--Tekniska högskolan, Stockholm. / Stamped on cover: K.T.H. Avh. 14.

No description available.

Thesis (M.S.)--Ohio University, August, 1997. / Title from PDF t.p.

Early plastic shrinkage cracking of concrete is an important factor affecting the durability of modern concrete structures. Early cracking (within 24 hours after pouring) may become a problem for any concrete structure. It will promote the entry of harmful materials, destroy the beauty of concrete members, and reduce their durability and performance. In addition, due to long-term shrinkage and/or load, these cracks may gradually expand in the service life of components. Scientific research and engineering technicians often have to face the difficulties caused by early plastic shrinkage cracking of concrete. From the aspects of shrinkage mechanism, measurement method, prediction model and strength development, this paper reviews the scientific and technological status of plastic shrinkage and strength development of early-age concrete, and based on this, summarizes the important conclusions in existing research and establishes the relevant concrete strength prediction model.:1 Introduction 2. Shrinkage in concrete 2.1 Classification and mechanism of concrete shrinkage 2.2 Main factors causing concrete shrinkage 2.3 Concluding remarks 3. Plastic shrinkage in early age concrete 3.1 Method for determining the time of initial and final setting 3.2 Mechanism of plastic shrinkage 3.3 Evaporation 3.4 Capillary pressure 3.5 Main factors affecting plastic shrinkage cracking 3.6 Concluding remarks 4. Different methods for determining the resistance to plastic shrinkage cracking 4.1 Rectangular mould test setup 4.2 ASTM C 1579 4.3 Ring test method (NT BUILD 433) 4.4 Capillary pressure test 5. Development of early age strength of concrete 5.1 Mechanical properties 5.1.1 Compressive strength 5.1.2 Tensile strength 5.1.3 Early-age shrinkage of concrete 5.2 Test and prediction model evaluation 6. Test and quantitative model 6.1 pullout tests on early-age concrete 6.1.1 Tests principle 6.1.2 test result 6.2 Compilation of existing pullout capacity prediction models 6.2.1 Strength and pullout force model based on 𝒉𝒆𝒇 6.2.2 Strength and pullout force model based on 𝒉𝒆𝒇 and ∅𝒉 6.2.3 Tensile strength and pullout force model 6.3 Application of existing prediction model in early age concrete 7. Conclusions 8. Literature

Strength of concrete is the major parameter in the design of structures and is represented by the 28-day compressive strength of concrete. Many earlier studies proved that the compressive strength of concrete is not only related to w/c ratio but also rely on proportion of other constituent materials. Application of recently developed new generation admixtures for the production of high performance concrete, has made the concrete strength prediction complex and highly nonlinear challenging the research engineers and data scientists. Development of early accurate prediction model for concrete strength provides the mix designer a tentative idea to proportionate the mix ingredients accordingly reducing the number of trial mixes ultimately saving a lot of cost and time associated with it. In this study, we have proposed SVM regression tool to create the model for the prediction of concrete strength. Support vector machine (SVM) is a supervised machine learning technique based on statistical learning theory developed by Vapnik in 1995. SVM employs a kernel function to transform the data into high dimensional feature space and linear modeling is performed in the feature space to overcome the complexity related to highly nonlinear datasets. A dataset containing 425 observations of high performance concrete mix design with nine attribute variables from University of California, Irvine Repository are considered for this study. 395 datasets were used to train the model and 30 samples were taken as a test set by random sub sampling to test the model. Five-fold cross-validation technique was used to select the parameters of SVM. The metaparameter values ε = 0.001, C = 29.47 and γ = 10 are selected for creating the model. The model performance measures correlation coefficient (R), root mean square error (RMSE) values and residual plots suggest that the proposed SVM model is competent enough to predict the strength of concrete. The performance measures of proposed SVM model was compared with RVM model.

[pt] Neste trabalho é realizada uma pesquisa de campo sobre a resistência a compressão do concreto em estruturas reais, com o objetivo de se estabelecer a correlação entre resistência especificada em projeto (fck,especificada) e a resistência estimada (fck,estimada). Foram analisados os resultados obtidos nos ensaios de 6.312 corpos-de-prova moldados e extraídos, e também de ensaios de esclerometria. A pesquisa de campo se estendeu por um período de obras de até nove meses. No programa de ensaios foram estudados concretos produzidos por duas centrais dosadoras, com resistência a compressão especificada aos 28 dias de 35 MPa, fornecidos para quatro obras diferentes. Diversos parâmetros foram analisados: aumento da resistência com a idade do concreto; diferença entre os valores da resistência especificada e a resistência do concreto fornecido ao longo do tempo de execução das obras; correlação entre os valores da resistência obtida em corpos-de-prova moldados e extraídos. Os resultados mostraram que existe uma diferença entre os valores da resistência especificada e da resistência estimada no início da obra, e que essa diferença tende a diminuir ao longo da execução da obra. Os resultados mostraram ainda que o coeficiente de correção dos efeitos de broqueamento em testemunhos recomendado pela NBR 6118:2007 é adequado. Finalmente são dadas sugestões sobre o número adequado de testemunhos a serem extraídos quando há divergências a serem dirimidas. / [en] In this work is made a fieldwork about the compressive strength of concrete in real structures in order to establish the correlation between specified strength in project (fck, specified) and estimated strength (fck, estimated). The results from tests of 6.312 molded and extracted specimens were analyzed, as well as hammer rebound tests. The fieldwork lasted a construction period of up to nine months. In the test program was studied ready mixed concrete producers by two concrete plants with the compressive strength specified of 35 MPa in 28 days, provided for four different constructions. Several parameters were analyzed: increasing strength according to concrete age; difference between the specified strength values and concrete strength provided during the constructions; correlation between the strength values obtained in molded and extracted specimens. The results showed that there is a difference between the values of specified strength and estimated strength at the beginning of the construction. The results also showed that the correction coefficient of the drilling effects on core recommended by the NBR 6118:2007 is appropriate. Finally, suggestions are given on the appropriate number of core to be taken when there are differences to be settled.

In this study, relationships between aggregate shape parameters and compressive strength of concrete were investigated using digital image processing and analysis methods. The study was conducted based on three mix design parameters, gradation type, aggregate type and maximum aggregate size, at two levels. A total of 40 cubic concrete specimens were prepared at a constant water-cement ratio. After the compressive strength tests were performed, each specimen was cut into 4 equal pieces in order to obtain the digital images of cross sections using a digital flatbed scanner. A number of aggregate shape parameters were then determined from the digital image of the cross sections to investigate their relationships with the compressive strength. The results indicted that even though the aggregate type was found to give strong correlation with the compressive strength, weak correlations, however, exist between the compressive strength and the aggregate shape parameters. The study suggested that the analyses of relationships should be further investigated by including the effects of aggregate distribution within the specimen cross sections.

El río Rímac en épocas de avenidas suele socavar la ribera del río ocasionando deslizamientos del terreno que ponen en contante peligro a la población local. Para ello, se analizará dos propuestas de solución en un tramo de 150 metros en el talud del río Rímac, en el distrito de San Juan de Lurigancho. Las propuestas son una convencional y otra que por el momento no es muy conocida en nuestro país. La primera alternativa es la construcción de muros de concreto armado, debido a su alta efectividad en este tipo de problemática. La segunda alternativa, es la construcción de Muros Krainer, estos son un tipo de muro innovador, considerados como un método de bioingeniería que tiene como objetivo simular un muro de tierra armada. Se realizará un análisis estático y pseudoestático para cada tipo de muro en estudio. A su vez, el objetivo de dichos análisis es obtener el factor de seguridad, así como verificar el desempeño de este con los valores requeridos para cada muro con la ayuda de hojas de cálculos y herramientas computacionales. Por otro lado, se efectuará un análisis de costo con la conformación de análisis de precios unitarios para cada partida que requiere la elaboración de ambos muros. El producto del análisis estático y pseudoestático para los muros estudiados satisfacen los valores requeridos para su estabilidad. Sin embargo, el resultado del costo directo para la realización del muro Krainer resulto menor a comparación del costo directo del muro de contención de concreto armado. / The Rímac river in times of avenues usually undermines the riverbank causing landslides that endanger the local population. For this, two solution proposals will be analyzed in a 150-meter section on the slope of the Rímac river, in the San Juan de Lurigancho district. The proposals are one conventional and another that at the moment is not well known in our country. The first alternative is the construction of reinforced concrete walls, due to its high effectiveness in this type of problem. The second alternative is the construction of Krainer Walls, these are an innovative type of wall, considered as a bioengineering method that aims to simulate a reinforced earth wall. A static and pseudostatic analysis will be carried out for each type of wall under study. In turn, the objective of said analyzes is to obtain the safety factor, as well as verify its performance with the values required for each wall with the help of spreadsheets and computational tools. On the other hand, a cost analysis will be carried out with the formation of unit price analyzes for each item that requires the preparation of both walls. The product of the static and pseudostatic analysis for the studied walls satisfy the values required for their stability. However, the result of the direct cost for the realization of the Krainer wall was lower compared to the direct cost of the reinforced concrete retaining wall. / Tesis