International Concrete Abstracts Portal

There is a great demand in the world for low-cost and functional pipeline systems due to the renovation requirements of pipes in use and the continuous development of new settlements. Previously used pipeline systems made of steel reinforced concrete are economical and sufficiently resistant. However, due to the corrodibility of steel reinforcement and to enable sufficient crack reduction, large wall thicknesses and thus heavy constructions are required. Textile reinforced concrete (TRC) eliminates these disadvantages by enabling the production of light and thin-walled structures.

The aim of this research is the development of a concept for the realization of smart pipes made of sensory TRC by using the advantages of lightweight, thin-walled structures, focusing on the production process. Based on different warp knitted textile variations with different coating concentrations, preliminary tests were carried out using the fourpoint bending test. As a result of the preliminary tests, the textile variation of counterlaid tricot with a maximum coating concentration was selected as a suitable reinforcing material for the concept development. Concepts for the production of smart TRC pipes are developed accordingly. As a result, a casting mold and process were created which allowed a production with reduced diameter and depth of pores and concentric positioning of the reinforcement structure.

The mechanical behaviour of fibre reinforced concrete pipes (FRCP) is usually verified through three-edge bearing test (TEBT). More recent studies propose a design approach according to the fib Model Code 2010, involving the evaluation of mechanical behaviour in both service (SLS) and ultimate (ULS) limit states. The challenge consists in assessing with the proper accuracy and reliability the mechanical parameters by means of the TEBT method. This is generally performed using a hydraulic equipment with load control and without using devices to measure the diametric displacement. In this research program, TEBT was carried out using three different control systems. Two closed-loop controls, using pipe diametric displacement or actuator displacement, and an open-loop control by loading rate. The crack width development was also measured simultaneously with the diametric displacement, only for closed-loop control. An increase in the post-crack strength of the FRCP were observed when the closed-loop system was used. The results show significant differences between the mechanical performances of pipes tested in open or closed-loop control. Conversely, closedloop tests performed with actuator displacement control or pipe diametric displacement control show no significant differences. Crack opening measurement allows establishing a linear correlation with diametric displacement, this permitting to establish the values corresponding to the SLS and ULS deformation and respective loads. Consequently, the connection with the Model Code approach becomes possible as well as the design optimization of the FRCP.

Q: Our company was recently awarded the contract to build a post-tensioned parking structure. The construction documents include a typical detail showing that reinforcing bars are to be no closer than 1 in. from embedded pipes, ducts, or sleeves. This requirement creates a constructability challenge. Is it based on technical publications published by ACI? The specified maximum aggregate size is 3/8 in. Q: According to Table 19.3.2.1 in ACI 318-19,¹ a Type V cement is required for Exposure Class S2, while footnote [6] allows the use of a Type I or Type III cement with C₃A content of less than 5%. How about a Type II cement if it has a C₃A content of less than 5%?

The Hebron platform is the latest major offshore integrated oil drilling and production platform supported by a concrete gravity-based-structure (GBS). It was successfully installed in the Grand Banks (offshore Newfoundland) in June 2017. The design of the platform was challenged by arctic-like and extreme metocean conditions. This paper presents development of extreme loads on the GBS such as 10,000-year iceberg impact and wave loads. It also describes novel design and construction techniques used, which resulted in a capitalefficient platform.

From an analysis and design perspective, in addition to linear-elastic finite element analysis typically used in design of offshore concrete GBS, the innovative use of non-linear finite element analysis (NLFEA) technique to calculate internal forces is presented. Such analyses more accurately capture the structural behavior and result in more realistic internal forces. In addition, a new crack-width calculation method accounting for the effect of a significant number of layers of transverse reinforcement was implemented. Also, a novel method to assess the complex interactions between solid ballast, embedded pipes, and concrete structures was applied.

From a construction perspective, the use of slipforming panels that are taller than those used in past GBSs and a system to allow slipforming of the shaft wall with a complex geometry and curvature, that is much larger than that employed in the past GBS, are presented. A novel method to minimize the risk of concrete adhering to slipforming panels by cooling the panels with cold water is presented. An innovative method to ensure that highstrength grout completely filled the space underneath one of the largest Topsides footings is discussed. Full-scale constructability tests of various complex GBS components, which provided invaluable information for design, increased execution certainty, and improved construction safety, is presented.

This paper reports on the research developing the backfill mortar used for repairing construction of deteriorated concrete structures, such as sewage pipelines. The mortar should have high strength to satisfy the demand of pipe rigidity. And high filling ability is necessary to fill the unevenness on the renewal pipe surface. Also, low density of mortar can improve the work efficiency. Accordingly, the target values were that the compressive strength was 45.0 N/mm² (940000 psf) or more at 28 days, the mortar flow was 250 ± 20 mm (10±0.79 in.), and the density was 1.70 ± 0.15 g/cm3(110±10 lb/ft³). The applicability of this backfill mortar to repair work was studied.