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International Concrete Abstracts Portal

Showing 1-5 of 455 Abstracts search results

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-337_06

Date: 

January 23, 2020

Author(s):

Edward (Ted) Moffatt, Michael Thomas and Andrew Fahim

Publication:

Symposium Papers

Volume:

337

Abstract:

In 1978, the Canadian Centre of Mineral and Energy Technology (CANMET) initiated a longterm study to determine the performance of concrete in a marine environment. Between 1978 and 1994, over three hundred prisms as part of 14 different experimental phases were placed at the mid-tide level at the Treat Island exposure site. Treat Island is an outdoor exposure site operated by the U.S. Army Corps of Engineers, and lies in the Passamaquoddy Bay, part of the Bay of Fundy, near the town of Eastport in Maine. Following 25 years of exposure, the blocks were retrieved after being exposed to tidal conditions representing approximately 18,250 cycles of wetting and drying, and 2,500 cycles of freezing and thawing. This paper presents the durability performance of concrete from several phases of the CANMET study. This includes concrete incorporating various levels of supplementary cementing materials (up to 80% by mass of cementing material in some cases), with normal density and light-weight aggregate. The paper also compares output from the service-life model Life-365 with experimental chloride profile data. The results indicate the efficacy of SCMs in increasing the concrete resistance to chloride penetration. However, use of very high levels of these materials was found to render the concrete more susceptible to surface scaling. The results also showed that Life-365 model can predict chloride penetration adequately with very simple inputs.


Document: 

SP-336_04

Date: 

December 11, 2019

Author(s):

Yu Jiang, Gang Xu, Zhipeng Li, and Xianming Shi

Publication:

Symposium Papers

Volume:

336

Abstract:

In this study, we tested compressive strength, rheology, initial setting time and transport properties of mortar samples mixed with green corrosion-inhibiting admixtures were tested. Four types of green corrosion inhibitors were adopted, which were extracted from peony leave, Kentucky blue grass, sugar beet leave and dandelion. All of them affected the compressive strength adversely but improved other properties of mortar samples. Resistance of mortar to chloride induced corrosion was evaluated using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. The results indicated that these green corrosion-inhibiting admixtures provided promising inhibiting performance under chloride environment. The results also suggested these green corrosion-inhibitors have the potential to be used as multifunction corrosion inhibitors for concrete, such as serving as water reducer and set retarder. Future work would focus on chemical mechanism of green corrosion inhibitors and the comparative evaluation of these green corrosion inhibitors with other commercially available corrosion inhibitors.


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.


Document: 

SP-329-23

Date: 

September 26, 2018

Author(s):

Fei Xiao, Yongwei Wang, Jinhuan Lv, Jie Zhang, and Tongwei Lu

Publication:

Symposium Papers

Volume:

329

Abstract:

In many parts of the world, the lowest temperature in winter is less than -20 degrees Celsius. It is an important problem in the field of construction engineering to improve the quality of concrete engineering and improve the durability of the structure under extreme climate. This paper introduces the development of ultralow temperature anti freezing pumping admixture. In the experiment, the concrete cured at -4°F (-20 °C) or -13°F (-25°C) for 7 days. And then the specimens were maintained in standard condition for different ages. Mechanical and durability properties of concrete were test in different curing conditions and different ages were studied. Mechanical properties include “negative temperature” compressive and flexural strength. Durability includes anti-permeability performance, dry shrinkage and chloride ion penetration resistance. The experimental data shows that the concrete have good mechanical and durability properties in ultra-low temperature because of the addition of an anti-freezing pumping agent. Compared with ordinary antifreeze, the negative temperature strength of concrete mixed with this ultralow temperature anti freezing pumping agent can be increased by more than 100%. By means of scanning electron microscopy (SEM) and pore size analysis were carried out. The action of this super low temperature anti freezing pumping agent and the frost resistance mechanism of concrete are analyzed.


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