A new study of Brazilian concrete strength conformance

Abstract

A new study of Brazilian concrete strength conformance Um novo estudo da conformidade da resistência do concreto produzido no Brasil Abstract ResumoThis paper presents a new evaluation of the strength compliance of concretes produced in Brazil. It is based on experimental results of over twenty-seven thousand concrete samples from different parts of the country. Results show that a significant part of Brazilian concrete do not reach the characteristic strength (fck) specified in design, and the percentage of nonconforming samples tend to be higher than 5%. This study also reveals the concrete produced in the South and Midwest regions have less variability than the ones produced in the other regions of the country. These results emphasize the importance of a rigorous control in manufacturing and reception of concretes in order to reduce the nonconforming cases.Keywords: concrete strength compliance, concrete structures, structural safety.Este artigo apresenta uma nova avaliação da conformidade dos concretos atualmente produzidos no Brasil. Ela está pautada em resultados de ensaios de resistência à compressão axial de mais de vinte e sete mil corpos de prova de concretos moldados in loco, no ato de seu recebimento, em diferentes obras do país. Os resultados mostram que parte do concreto produzido no Brasil não alcança a resistência característica (fck) prevista em projeto, e que o percentual de amostras não conformes tende a ser superior a 5%. Este estudo também evidencia que os concretos produzidos nas regiões Sul e Centro-Oeste apresentam menor variabilidade que aqueles produzidos nas demais regiões do país. Estes resultados reforçam a importância de um controle rigoroso na fabricação e no recebimento do concreto visando diminuir a ocorrência de não conformidades.Palavras-chave: conformidade da resistência do concreto, estruturas de concreto, segurança das estruturas.

Study of brazilian structural concrete block conformity

“…Although Class A blocks tend to have a smaller estimated strength and a lower average strength, Figure 3 makes clear that these same blocks have less dispersion in their results indicating that there is less variability among them. Stewart and Laerence [16] obtained coefficients of variation (C.V.) around 0.19, which are in line with the values found in this study and in studies about the conformance of concretes manufactured in Brazil [17,18,19,20]. Table 5 presents results obtained for the concrete blocks dimensions, at regional and national level.…”

Reliability-based calibration of main Brazilian structural design codes

“…The characteristics of the random variable resistance f c were derived from results of axial compression tests, performed at 28 days, in more than 39 thousand cylindrical specimens of concrete, molded "in loco" all over Brazil, between 2011 and 2016, as reported by Santiago and Beck (2017a), Santiago and Beck (2017b) and Santiago and Beck (2018). Table 1 presents the results concerning this variable, where the mean (µ) is expressed as a function of the characteristic strength of concrete (f ck ).…”

Reliability-based calibration of Brazilian structural design codes used in the design of concrete structures

“…A summary of the results concerning these variables is shown in Table 1; it is important to notice that the means are expressed as a function of their respective characteristic or nominal values. Statistics in Table 1 were obtained from results of axial compression tests at 28 days performed in more than 39 thousand cylindrical specimens of concrete molded in loco all over Brazil, between 2011 and 2016, as reported by Santiago and Beck [15,16,17]. As in the work of Nowak et al [8], the parameters of the probability distribution functions of the variables were ob-Reliability-based calibration of Brazilian structural design codes used in the design of concrete structures tained from the adjustment of probability density function ( Figure 1).…”