International Concrete Abstracts Portal

This is a Reference Specification that the Architect/Engineer can apply to any construction repair and rehabilitation project involving structural concrete by citing it in the Project Specifications. Mandatory requirements and optional requirements checklists are provided to assist the Architect/Engineer in supplementing the provisions of this Specification, as required or needed, by designating or specifying individual project requirements. The first section covers general construction requirements for repair Work. The second section covers shoring and bracing of the structure or member to be repaired, and addresses sequencing of repair Work as the structure is unloaded and reloaded. The third section covers concrete removal and preparation of the concrete substrate for repair and defines common equipment and methods. The next five sections cover materials and proportioning of concrete; proprietary cementitious and polymer repair materials; reinforcement; production, placing, finishing, and curing of repair materials; formwork performance criteria and construction; treatment of joints; embedded items; repair of surface defects; mockups, and finishing of formed and unformed surfaces. New sections included in this edition of the Specification includes waterproofing cracks by chemical grout injection, architectural concrete repair, structural precast concrete repair, unbonded post-tensioned concrete repair, overlays, protective membranes, and cathodic protection by galvanic anodes. Provisions governing testing, evaluation, and acceptance of repair materials as well as acceptance of the repair Work are included. Sections 16, 17 and 18 incorporate by reference other ACI specifications into this ACI Standard: ACI SPEC-503.7 for crack repair by epoxy injection, ACI SPEC-506.2 for shotcrete, and ACI SPEC-440.12 for wet-layup FRP. Keywords: bracing; cold weather; compressive strength; consolidation; curing; durability; epoxy injection; finish; formwork; grouting; hot weather; inspection; joints; mockups; placing; precast; rehabilitation; repair; reshoring; shoring; shotcrete; slab; steel reinforcement; surface preparation; testing; tolerance; welded wire.

This Specification provides requirements for circular precast polymer-concrete manholes for use in sanitary and storm sewer systems. It includes ordering information, minimum physical and chemical requirements for the polymer concrete mixture, criteria for designing the manhole components, manufacturing and quality control requirements, and documentation to certify the adequacy of the design. Keywords: absorption; chemical resistance; compressive strength; dimensional tolerances; design loads; polymer concrete; precast manhole; structural design.

Several studies have revealed that slabs with cast-in-place over precast, prestressed panels (CIP-PCP) behave differently from traditional concrete slabs because of the panel joints between the PCP components. While high-strength reinforcing bars can improve load capacity or reduce reinforcing bar quantity in traditional slabs, limited research has focused on their application in CIP-PCP slabs. This study addressed this gap by conducting four-point bending tests on CIP-PCP slabs with normal- and high-strength reinforcing bars. Two configurations of high-strength steel were used: one with the same reinforcing bar layout as normal-strength reinforcing bars and another with increased reinforcing bar spacing to reduce the reinforcing bar quantity. Additionally, slab specimens were designed to replicate real-world bridge deck conditions, including longitudinal and transverse joints, for detailed analysis. The results indicated that reducing reinforcing bar quantity by adjusting reinforcing bar spacing based on the specified yield strength ratio between normal- and high-strength steels maintained a comparable load capacity, with crack widths magnitude similar to those in normal-strength steel layout in the service state.

The deformability of reinforced concrete walls with staggered lap splices was studied through tests of six cantilevered walls under constant axial load and cyclic reversals of lateral displacement. The height-to-length aspect ratios of the walls were approximately 3.2. Four walls had staggered laps, one wall had non-staggered laps, and one wall had mechanical couplers. Laps were detailed to yield the spliced reinforcement. Test walls with staggered laps lost lateral-load resistance at smaller drift ratios (1.0% to 2.1%) than both the test wall with non-staggered laps (2.3%) and the test wall with mechanical couplers (3.5%). Staggered lap splices resulted in larger strain concentrations than non-staggered lap splices. It was concluded that both staggered and non-staggered lap splices a) can have reduced strain capacity relative to continuous bars (leading to bond failure before or after yield) and b) alter inelastic strain distributions, causing large reductions in effective plastic hinge length.

Ultra-high-performance concrete (UHPC) is increasingly gaining attention for structural applications, with structural fire safety being a key design factor. It is evident from recent research that UHPC structural members are prone to fire-induced spalling and have lower fire resistance than traditional concrete members. Currently, there are no specific guidelines for the fire design of UHPC members, and extending existing fire design provisions developed for conventional concrete members may not be appropriate, considering the unique challenges posed by UHPC. This paper outlines the critical factors contributing to the lower fire performance of UHPC structural members, discussing these factors in detail, using data from both numerical and experimental studies. Based on the results from parametric studies, as well as observations from published data, a set of design guidelines for mitigating spalling and enhancing the fire resistance of UHPC beams is proposed.