Comparing test methods for the mechanical characterization of fiber reinforced concrete

Abstract

Different tests are proposed by international standards for the evaluation of the mechanical properties of fiber reinforced concrete (FRC); among them, either beams or round determinate panels are generally used. However, different tests are accepted by design codes if reliable correlation factors between standard parameters are provided (fib Model Code 2010). Within this context, a broad experimental program on both beams and round determinate panels was carried out in order to provide a critical discussion on material characterization and to evaluate possible correlation factors. Beam tests according to European (EN 14651), American (ASTM 1609), and Japanese (JCI‐SF4) standard, as well as small round panels and large round panels (according to ASTM 1550) were studied within an experimental program comprising 189 beams and 90 round panels. Unlike previous researches, mainly focused on steel fibers, two types of macro‐synthetic fibers were considered. Based on these experimental results, a comparison between test methods is presented, along with correlation approaches are proposed and critically discussed.

Influence of steel, glass and polymer fibers on the cracking behavior of reinforced concrete beams under flexure

“…Figure shows the influence of fibers on the maximum crack width (a) and on the mean crack spacing (b) as a function of f R,1 ; the latter is the postcracking parameter of EN 14651 related to SLS. It is worth mentioning that the crack width associated to f R,1 at the notch tip is around 0.36 mm, which is greater than the measured crack width on RC beams at SLS (between 0.07 and 0.22 mm, Table ). It appears that the maximum crack opening, significant for SLS, is reduced by the presence of fibers.…”

Evaluación de una modificación en la norma ASTM C1609 para el estudio de concreto reforzado con fibras sintéticas sometido a flexión

“…El comportamiento en la probeta BAS2 fue distinto ya que sí es clara su capacidad residual siendo que la viga resistió alrededor de unos 5 kN aún después de alcanzado su MOR. Este comportamiento es totalmente aleatorio y puede estar relacionado con condiciones específicas en esa viga en cuanto a la distribución de agregados y fibras así como su orientación (Conforti, Minelli, Plizzari, & Tiberti, 2018). Con las relaciones dadas en la norma ASTM C1609 se puede determinar la razón de resistencia a flexión equivalente para esta viga:…”

“…En todos los ensayos se observó el reblandecimiento caracterizado por la caída rápida de la carga después de alcanzado el esfuerzo del primer pico y seguida por un aumento en la resistencia residual, en este tipo de materiales también es característica la formación de una sola grieta que se expande. El fenómeno de reblandecimiento está presente cuando no existe una carga pico que sea mayor a la carga del primer pico en los gráficos (Conforti et al, 2018;Li, Niu, Wan, Liu, & Jin, 2017). En los gráficos obtenidos por método ASTM el comportamiento residual presenta un máximo cerca de los 1,5 mm de deflexión y luego cae al final del ensayo, por otro lado, para EN14651 la resistencia residual es constante en todo el rango de análisis o bien tiene una ligera tendencia al aumento.…”

Strength prediction models for steel, synthetic, and hybrid fiber reinforced concretes

“…24,[26][27][28][29][30][31][32] Since the use of a single type of fiber has a limited effect on mechanical properties of FRC, the use of different fiber combinations (synthetic fibers with or without steel fibers) has become increasingly widespread. 18,[33][34][35][36][37][38] According to the test results obtained from these investigations, the use of hybrid fibers to enhance mechanical properties of FRC is more effective than that of either steel or synthetic fibers separately. Furthermore, as steel fibers have higher elastic modulus and tensile strength than synthetic fibers, they are found to be more effective in sharing tensile forces in mortar matrix.…”

“…However, although many studies have been performed on synthetic and hybrid FRC, there are very few strength models covering synthetic and hybrid fibers in the literature. 33,35 Therefore, it has become a necessity to develop new strength models for steel, synthetic and hybrid FRC.…”