International Concrete Abstracts Portal

This Specification describes the work of repairing defects in hardened portland-cement concrete with an epoxy mortar. Included are controls for epoxy resin system labeling, storage, handling, surface evaluation and preparation, mixing and application, inspection, quality control, and testing.. Keywords: adhesion to concrete; aggregate; concrete construction; epoxy; epoxy mortar; hardened concrete quality control; repairs; resurfacing.

ACI CODE-440.13 was developed to provide design professionals a code for the design of strengthening strategies for concrete structures using fiber-reinforced polymer (FRP) systems. Keywords: buildings; carbon fiber; fiber-reinforced polymer; glass fiber; rehabilitation; repair; strengthening; structural design.

The use of parametric/natural fires in the design of reinforced concrete structures in fire conditions requires an accurate definition of the temperature-induced evolution of the thermal and mechanical properties. Within this context, the characterization of four normal-strength concretes (f_c²⁰ = 4220-7000 psi [29-47 MPa]), with siliceous and carbonate aggregates are studied here as concerns the thermal diffusivity D (between 68 and 1644°F [20 and 900°C]) and under uniaxial compression after different thermal cycles, with reference maximum temperatures of 392, 752, and 1112°F [200, 400, and 600°C]. The results show that thermal diffusivity exhibits mostly irreversible behavior after exposure to temperatures over 1382°F [750°C]. As concerns the compressive strength, the hot and residual values (when TT_test = 68°F [20°C]) are, overall, in line with the most common standard provisions. Quite interestingly, the tests carried out at intermediate temperatures (with T_test does not = T_max and T_test > 68°F [20°C]) highlighted a strength decay, which is not simply an interpolation between hot and residual values.

This paper proposes new procedures for determining allowable loads for power-actuated fasteners that are consistent with ASCE/SEI 7-22. Thirty new load test datasets for single fasteners in shear and tension, and fastener groups in shear, are analysed statistically. The current ICC-ES AC70-2021 procedure yields allowable loads that are quite variable, even negative, and very sensitive to “reject-as-outlier” decisions. In addition, ICC-ES AC70-2021 procedures to determine allowable loads can currently not be clearly linked to the reliability requirements per ASCE/SEI 7-22. Monte Carlo simulation demonstrates that the proposed Simplified Method, derived from the described Detailed Method, is robust for sample sizes as small as ten specimens. It yields Allowable Fastener Loads that are 10 to 25% greater than those obtained using the current ICC-ES AC70-2021 procedure, yet are typically 60 to 90% of the actual Allowable Fastener Loads, derived from the described Detailed Method to assess allowable loads in line with ASCE 7 reliability requirements. The new provisions are extended to cases where the coarse aggregate hardness in the test specimens differs from that in the structure, which is not addressed in ICC-ES AC70.

This paper presents the implications of variable bond for the behavior of concrete beams with glass fiber-reinforced polymer (GFRP) bars alongside shear-span-dependent load-bearing mechanisms. Experimental programs are undertaken to examine element- and structural-level responses incorporating fully and partially bonded reinforcing bars, which are intended to represent sequential bond damage. Conforming to published literature, three shear-span-to-depth ratios are taken into account: arch action, beam action, and a transition from arch to beam action. When sufficient bond is provided for the element-level testing, the interfacial failure of GFRP is brittle against a concrete substrate. An increase in the shear-span-to-depth ratio from 1.5 to 3.7, aligning with a change from arch action to beam action, decreases the load-carrying capacity of the beams by up to 40.2% and the slippage of the partially bonded reinforcing bar dominates their flexural stiffness. Compared with the case of the beams under beam action, the mutual dependency of the bond length and shear span is apparent for those under arch action. As far as failure characteristics are concerned, the absence of bond in the arch-action beam prompts crack localization; by contrast, partially bonded ones demonstrate diagonal tension cracking adjacent to the compression strut that transmits applied load to the nearby support. The developmental process of reinforcing bar stress is dependent on the shear-span-to-depth ratios, and, in terms of using the strength of GFRP, beam action is favorable relative to arch action. Analytical modeling suggests design recommendations, including degradation factors for the calculation of reinforcing bar stresses with bond damage when subjected to arch and beam actions.