This study attempted to develop a model for the stress-strain relationship in compression of frost-damaged concrete subjected to fatigue loading. Concrete specimens were prepared and exposed to freeze-thaw cycles followed by application of static and fatigue loading. The strains induced during the freeze-thaw test were carefully measured as well as during a mechanical loading test. It was found that the static strength and the fatigue life of concrete decreases as increasing irreversible tensile strain was induced by frost action. A stress-strain model for frost-damaged concrete under application of static and fatigue loading based on the degradation of initial stiffness caused by frost damage was presented. The degradation of initial stiffness for damaged concrete was empirically formulated as a function of remaining expansion caused by freeze-thaw cycles. The plastic strain under the application of mechanical static and fatigue loading for frost-damaged concrete is higher than that for original concrete...

Mesoscale constitutive models of frost-damaged concrete are developed in this study through numerical simulation using a two-dimensional rigid body spring model (RBSM). The aim of the simulation is to predict the macrobehavior of frost-damaged concrete subjected to mechanical loading. The models also clarify the difference in failure behavior of concrete with and without frost damage. Zero strength elements and the concept of mesoscale plastic tensile strain are introduced into the normal RBSM springs to consider the experimentally observed cracking and plastic deformation caused by frost damage. The difference in the effect of frost damage on compression and tension behavior as found in the experiments is clearly predicted. Finally, analysis of a notched beam subjected to bending after different degrees of frost damage is carried out. The resulting load-deflection curves agree well with those obtained in the experiments. These good correlations confirm the applicability of the mesoscale model for predict...

This study aimed to determine the mechanical properties and absorption of high-strength fiber-reinforced concrete (HSFRC), using sustainable natural fibers. In this analysis, two types of fibers were used, namely, ramie and abaca. Two different HSFRC mixtures were also designed, where one composition emphasized ordinary Portland cement (OPC) as a binder, and the other prioritizing calcined diatomaceous earth (CDE) as a mineral additive to replace 10% weight of OPC. Furthermore, ramie and abaca fibers were separately added to the mixtures at three different volumetric contents. Based on the results, the addition of these fibers in the concrete mixtures improved the mechanical properties of HSFRC. The improvements of compressive strength, splitting tensile strength, and flexural strength, due to the addition of ramie fiber were 18%, 17.3%, and 31.8%, respectively, while those for the addition of abaca fiber were 11.8%, 17.2%, and 38.1%, respectively. This indicated that the fibers were capable of being used as alternative materials for sustainable concrete production. The effects of ramie and abaca fibers on the absorption of HSFRC were also not significant, and their presence for the same amount of superplasticizer reduced the flow speed of fresh reinforced concrete mixtures.

This paper presents the flexural and splitting tensile strength of high strength concrete (HSC) with diatomite micro particles (DMP) as a mineral additive. In order to have micro particles, the diatomite from Aceh Besar District was ground and sieved with sieve size of 250 mm. The particles were then calcined at the temperature of 600 °C for 5 hours. Four mixtures were designed with different DMP to binder ratio (DMP/b). The ratio was 0%, 5%, 10% and 15%, and the water to binder ratio was 0.3. Four beam specimens with a size of 10 cm × 10 cm × 40 cm and four cylinder-specimens with 10 cm diameter and 20 cm high were prepared for each mixture. Flexural and splitting tensile tests were conducted based on ASTM C78 and ASTM C496/496M. The maximum flexural strength was reached at DMP/b of 5% while the maximum splitting tensile strength was reached at DMP/b of 0%.