ABOUT THE INTERNATIONAL CONCRETE ABSTRACTS PORTAL

  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

Showing 1-5 of 226 Abstracts search results

Document: 

SP-346_03

Date: 

January 1, 2021

Author(s):

Abheetha Peiris and Issam Harik

Publication:

Symposium Papers

Volume:

346

Abstract:

Following an over-height truck impact, Carbon Fiber Reinforced Polymer (CFRP) fabric was used to retrofit the exterior girder in a four-span Reinforced Concrete Deck on Girder (RCDG) Bridge on route KY 562 that passes over Interstate 71 in Gallatin County, Kentucky. The impacted span (Span 3) traverses the two northbound lanes of Interstate 71. While the initial retrofit was completed in May 2015, a second impact in September 2018 damaged all four girders in Span 3. The previously retrofitted exterior girder (Girder 4) suffered the brunt of the impact, with all steel rebars in the bottom layer being severed. Damage to Girders 1, 2, and 3 was minor and none of the bars were damaged. A two-stage approach for the containment and repair of the damaged girders following an over-height truck impact was implemented when retrofitting the bridge. The repair and strengthening of all the girders using CFRP fabric was the economical option compared to the alternative option of replacing the RCDG bridge. The initial CFRP retrofit was found to have failed in local debonding around the impact location. The CFRP retrofit material that was not immediately near the impact location was found to be well bonded to the concrete. The removal of this material and subsequent surface preparation for the new retrofit was time consuming and challenging due to traffic constraints. In Girder 4 all but one of the main rebars were replaced by removing the damaged sections and installing straight rebars connected to the existing rebars with couplers. One of the rebars could not be replaced. A heavy CFRP unidirectional fabric, having a capacity of 534 kN (120,000 lbs.) per 305 mm (1 ft.) width of fabric, was selected for the flexural strengthening and deployed to replace the loss in load carrying capacity. A lighter unidirectional CFRP fabric was selected for anchoring and shear strengthening of all the girders, and to serve as containment of crushed concrete in the event of future over-height impacts. The retrofit with spliced steel rebars and CFRP fabric proved to be an economical alternative to bridge replacement.


Document: 

SP-340-05

Date: 

April 1, 2020

Author(s):

Nakin Suksawang and Hani Nassif

Publication:

Symposium Papers

Volume:

340

Abstract:

For many decades, latex-modified concrete (LMC) overlays have been successfully used in the United States, inclusive of providing protection for many bridge decks and their steel reinforcements. LMC remains one of the most desirable rehabilitation materials for concrete bridge decks because it is easier to place and requires minimal curing. Nevertheless, as is the case with any cement-based material, LMC overlays are susceptible to plastic shrinkage and delamination. These problems are often solved by proper curing and better surface preparation. Yet, despite these solutions, many questions have been raised regarding the best practices for placing LMC overlays and the proper curing and placement conditions. The current curing practice for LMC in most states simply follows the latex manufacturer’s recommendation because very little information on the proper curing methods is available. There is a need to establish detailed technical specifications regarding curing and placement conditions that will provide more durable LMC overlays. This paper provides an in-depth laboratory-based experimental study of the effect of curing methods and duration on the mechanical properties and durability aspects of LMC. Four different curing methods were examined: (1) dry curing, (2) 3 days of moist curing, (3) 7 days of moist curing, and (4) compound curing. Based on the results from the laboratory tests, technical specifications were developed for field implementation of LMC. Various types of sensors were installed to monitor the behavior of the LMC overlays on bridge deck. Results show that extending the moist-curing duration to a minimum of 3 days (and a maximum of 7 days) significantly improves both the mechanical properties and durability of LMC.


Document: 

SP-338_02

Date: 

March 1, 2020

Author(s):

Kenneth C. Hover

Publication:

Symposium Papers

Volume:

338

Abstract:

PCA researchers interested in the problem of evaporation of bleed water from concrete surfaces borrowed an equation developed by hydrologists to predict evaporation from Lake Hefner in Oklahoma. PCA’s graphical representation of that equation, subsequently modified to its present form by NRMCA, was later incorporated into multiple ACI documents, and is known by concrete technologists world-wide as the “Evaporation Rate Nomograph.” The most appropriate use of this formulation in concrete construction is to estimate the evaporative potential of atmospheric conditions (known as “evaporativity”). Since the difference between actual and estimated evaporation rate can be in the range of ± 40% of the estimate, best use of the equation as routinely applied is as a semi-quantitative guide to estimate risk of early drying and inform decisions about timing and conduct of concrete placing and finishing operations. Use of the “Nomograph” and related “Apps” in specifications is more problematic, however, given: 1.) the inherent uncertainty in its underlying equation, 2.) the difficulty in obtaining input data that appropriately characterize jobsite microclimate, and 3.) establishing a mixture-specific criterion for tolerable evaporation rate.


Document: 

SP-337_08

Date: 

January 23, 2020

Author(s):

Anthony Devito; Alex Krutovskiy and Leszek Czajkowski

Publication:

Symposium Papers

Volume:

337

Abstract:

The purpose of the LaGuardia Runway Extension Project is to extend existing runways 4-22 and 13-31 into Flushing Bay, at the inshore end of Long Island Sound, to support Engineered Material Arresting System (EMAS) - a crushable material installed at the end of each runway to reduce the risk of a plane overrun during takeoff.

The new runway deck extensions are marine concrete structures which utilize precast prestressed pile caps with a pre and post-tensioned composite precast deck and cast-in-place concrete topping slab. The concrete decks are supported by 250 ton (227 tonnes) 24 inch (61cm) diameter epoxy coated closed end concrete filled steel pipe piles with specialized wraps and sacrificial zinc anodes for corrosion protection. The piles are approximately 100 feet (30m) long and driven in about 30 feet (9m) of water through soft organic clay and dense glacial soils and founded on bedrock.

This paper provides an overall description of the runway extensions and a detailed account of both the technical and logistical challenges. Challenges included a prestressed composite deck design for both the aircraft impact and braking loads. Maintaining and replacing the lightbars of the Approach Lighting Systems (ALS) used to visually identify the runways was required, along with optimizing the pile hammer selection and driveability with wave equation analyses and dynamic pile driving PDA testing. Extensive coordination was necessary with the PANYNJ, FAA and various other stakeholders involved in this fast-paced design build project.


Document: 

SP-336_02

Date: 

December 11, 2019

Author(s):

Nidhi M Modha and Pratanu Ghosh

Publication:

Symposium Papers

Volume:

336

Abstract:

In this research, a natural pozzolanic cementitious material known as zeolite is being utilized to investigate the performance of High-Performance Concrete (HPC). Several binary (cement+zeolite) and ternary (cement+zeolite+other supplementary cementitious material) based concrete mixtures including a control mixture of Ordinary Portland Cement (OPC) with water - cementitious (w/cm) ratios of 0.40 and 0.44 are cast by replacing cement with different percentage level of zeolite material. The purpose of this study is to investigate effectiveness of zeolite material by means of long term compressive strength (7 to 91 days), tensile strength, modulus of elasticity and corrosion resistance in several concrete mixtures from 7 to 28 days. The compressometer is utilized for the measurement of the modulus of elasticity and Universal Testing Machine (UTM) is utilized to measure the compressive and tensile strength of concrete. In addition, a 4-point Wenner Probe resistivity meter is tested to determine the surface electrical resistivity of concrete, which provides an indirect indication of permeability and in turn, chloride induced corrosion durability in reinforced concrete structures. Overall, zeolite based concrete mixtures with 0.40 w/cm ratio and ¾ inch aggregate size provide promising results in terms of compressive strength, tensile strength and remarkable improvement on corrosion resistance in terms of achievement of surface resistivity data.


12345...>>

Results Per Page 




Please enter this 5 digit unlock code on the web page.