Effect of the Notch-to-Depth Ratio on the Post-Cracking Behavior of Steel-Fiber-Reinforced Concrete

Concrete barely possesses tensile strength, and it is susceptible to cracking, which leads to a reduction of its service life. Consequently, it is significant to find a complementary material that helps alleviate these drawbacks. The aim of this research was to determine analytically and experimentally the effect of the addition of the steel fibers on the performance of the post-cracking stage on fiber-reinforced concrete, by studying four notch-to-depth ratios of 0, 0.08, 0.16, and 0.33. This was evaluated through 72 bending tests, using plain concrete (control) and fiber-reinforced concrete with volume fibers of 0.25% and 0.50%. Results showed that the specimens with a notch-to-depth ratio up to 0.33 are capable of attaining a hardening behavior. The study concludes that the increase in the dosage leads to an improvement in the residual performance, even though an increase in the notch-to-depth ratio has also occurred

Splitting test experimental dataset of hollow concrete blocks

Masonry structures are widely used nowadays for their advantages like low-cost workmanship, efficiency and fast construction techniques. The compressive strength of the materials that compose masonry (block and mortar) is very important to the behavior of the system, but the tensile strength is even more significant for the standards and building codes. In this work, a dataset for indirect tensile tests of hollow concrete blocks is obtained. Splitting tests as described in ASTM C-1006-13 are applied. Two sets of blocks were tested, one with medium compressive strength and the other with high compressive strength. The first set was tested in three directions named A, B, and C; the second one was tested in two directions, A and B. The data was collected with a servo-hydraulic machine. The data is presented in tables and can be used by material researchers, as well as in numerical modelin

Flexural Stiffness and Crack Width of Partially Prestressed Beams with Unbonded Tendons

The original concept of “Total Prestress” consists of creating compressions in concrete without generating tension stresses for service load, while in "Partially Prestressed” elements, tensions are allowed in the service stage, which would produce some cracking depending on applied loads that will be taken with non-prestressed reinforcement. Using criteria and design recommendations can guarantee maximum flexural capacity and admissible serviceability requirements of partially prestressed elements; however, there is insufficient research for estimating more accurately the required parameters for the design and review of these types of elements. Because of this, the present investigation consisted in the realization of experimental studies in continuous partially prestressed beams with unbonded tendons for the evaluation of the flexural behavior for different stages of load determining the actual stresses and the strains taking into account the structural stiffness decrease and its effect on deflections. The dimensions of the specimens were selected based on common dimensions presented on slabs. The tested specimens considered variables such as the relationship between the length of the continuous spans, the cross-section, and the partial prestressing ratio. Afterward, equations were proposed to predict the decrease in the structural stiffness, depending on the degree of cracking, the type of cross-section, the partial prestressing ratio, and the magnitude of the applied load and the tension and compression stresses to estimate the probable deflections for a particular loading stage. The crack width equation presented a difference of −16% to +18% with respect to the experimental data, while the flexural stiffness equation showed a highly accurate correlation to the experimental data

Development of a Portland Cement-Based Material with Agave salmiana Leaves Bioaggregate

Depending on the morphology of the natural fibers, they can be used as reinforcement to improve flexural strength in cement-based composites or as aggregates to improve thermal conductivity properties. In this last aspect, hemp, coconut, flax, sunflower, and corn fibers have been used extensively, and further study is expected into different bioaggregates that allow diversifying of the raw materials. The objective of the research was to develop plant-based concretes with a matrix based on Portland cement and an aggregate of Agave salmiana (AS) leaves, obtained from the residues of the tequila industry that have no current purpose, as a total replacement for the calcareous aggregates commonly used in the manufacturing of mortars and whose extraction is associated with high levels of pollution, to improve their thermal properties and reduce the energy demand for air conditioning in homes. Characterization tests were carried out on the raw materials and the vegetal aggregate was processed to improve its compatibility with the cement paste through four different treatments: (a) freezing (T/C), (b) hornification (T/H), (c) sodium hydroxide (T/NaOH), and (d) solid paraffin (T/P). The effect of the treatments on the physical properties of the resulting composite was evaluated by studying the vegetal concrete under thermal conductivity, bulk density, and compressive strength tests with a volumetric ratio between the vegetal aggregate and the cement paste of 0.36 and a water/cement ratio of 0.35. The hornification treatment showed a 15.2% decrease in the water absorption capacity of the aggregate, resulting in a composite with a thermal conductivity of 0.49 W/mK and a compressive strength of 8.66 MPa, which allows its utilization as a construction material to produce prefabricated blocks