Resistance of concrete to carbonation and chloride penetration assessed on site through nondestructive test

This paper investigates the fresh and durability properties of the high-performance concrete by replacing cement with 15% Silica fume and simultaneously replacing fine aggregates with 25%, 50%, 75% and 100% copper slag at w/b ratio of 0.23. Five mixes were analysed and compared with the standard concrete mix. Fresh properties show an increase in the slump with the increase in the quantity of copper slag to the mix. Sorptivity, chloride penetration, UPV and carbonation results were very encouraging at 50% copper slag replacement levels. Microstructure analysis of these mixes shows the emergence of C-S-H gel for nearly all mixes indicating densification of the interfacial transition zone of the concrete.

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The Effect of Cassava Starch on the Durability Characteristics of Concrete

The Open Civil Engineering Journal ◽

10.2174/1874149502014010289 ◽

2020 ◽

Vol 14 (1) ◽

pp. 289-301

Author(s):

Daniel Oni ◽

John Mwero ◽

Charles Kabubo

Keyword(s):

Cement Hydration ◽

Research Work ◽

Cassava Starch ◽

Chloride Penetration ◽

Hardened Concrete ◽

Sulphate Attack ◽

Marine Structures ◽

Durability Properties ◽

Chloride Attack ◽

Starch Gel

Background: Concrete is a common material used in the construction of marine structures, such as bridges, water treatment plants, jetties, etc. The use of concrete in these environment exposes it to attack from chemicals like sulphates, chlorides and alkaline, thereby causing it to deteriorate, and unable to perform satisfactorily within its service life. Hence, the need to investigate the durability properties of concrete has become necessary especially when admixtures are used to modify some of its properties. Objective: This research work investigates the effect of Cassava Starch (CS) on the durability characteristics of concrete. Methods: The durability properties investigated in this work are water absorption, sorptivity, resistance to sulphates, sodium hydroxides and chloride penetration. The specimens were prepared by adding CS by weight of cement at 0.4, 0.8, 1.2, 1.6 and 2.0% respectively. The concrete specimens were cured for 28 days, tested for compressive strength before ponding in ionic solutions of sodium hydroxide, sulphuric acid and sodium chloride. Six (6) concrete mixes were prepared, five of which were used to evaluate the effect of CS on the durability characteristics of concrete. Results: The slump values reduced with the increasing dosage of CS due to the viscous nature of the CS paste. Generally, the addition of CS in concrete tends to improve the resistance of concrete to sulphate and chloride attack due to the ability of the muddy-like starch gel to block the pore spaces of hardened concrete, hence, reduces the rate at which water and other aggressive chemicals penetrate the concrete. In addition, the retarding ability of CS impedes the formation of mono-sulphate aluminates during cement hydration, thereby making the concrete less susceptible to sulphate attack. Conclusion: The addition of CS to concrete by weight of cement generally improved the durability characteristics of concrete, while the relative performances of the concrete mixes showed that CS 2.0 gave a better resistance to chloride penetration and sulphate attack.

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Performance of self‐compacting rubberized concrete against carbonation and chloride penetration

Structural Concrete ◽

10.1002/suco.202000687 ◽

2021 ◽

Author(s):

Jihen Mallek ◽

Atef Daoud ◽

Othman Omikrine‐Metalssi ◽

Amara Loulizi

Keyword(s):

Chloride Penetration ◽

Rubberized Concrete

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The Rapid Chloride Migration Test in Assessing the Chloride Penetration Resistance of Normal and Lightweight Concrete

Applied Sciences ◽

10.3390/app11167251 ◽

2021 ◽

Vol 11 (16) ◽

pp. 7251

Author(s):

Jorge Pontes ◽

José Alexandre Bogas ◽

Sofia Real ◽

André Silva

Keyword(s):

Lightweight Concrete ◽

Chloride Transport ◽

Penetration Resistance ◽

Chloride Penetration ◽

Migration Test ◽

Simple Method ◽

Chloride Migration ◽

Binder Ratio ◽

Chloride Penetration Resistance ◽

Water Binder Ratio

Chloride-induced corrosion has been one of the main causes of reinforced concrete deterioration. One of the most used methods in assessing the chloride penetration resistance of concrete is the rapid chloride migration test (RCMT). This is an expeditious and simple method but may not be representative of the chloride transport behaviour of concrete in real environment. Other methods, like immersion (IT) and wetting–drying tests (WDT), allow for a more accurate approach to reality, but are laborious and very time-consuming. This paper aims to analyse the capacity of RCMT in assessing the chloride penetration resistance of common concrete produced with different types of aggregate (normal and lightweight) and paste composition (variable type of binder and water/binder ratio). To this end, the RCMT results were compared with those obtained from the same concretes under long-term IT and WDT. A reasonable correlation between the RCMT and diffusion tests was found, when slow-reactive supplementary materials or porous lightweight aggregates surrounded by weak pastes were not considered. A poorer correlation was found when concrete was exposed under wetting–drying conditions. Nevertheless, the RCMT was able to sort concretes in different classes of chloride penetration resistance under distinct exposure conditions, regardless of the type of aggregate and water/binder ratio.

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Investigation of Grouted Coupler Connection Details for Accelerated Bridge Construction

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198121999393 ◽

2021 ◽

pp. 036119812199939

Author(s):

Brent Phares ◽

Yoon-Si Lee ◽

Travis K. Hosteng ◽

Jim Nelson

Keyword(s):

Crack Width ◽

High Performance ◽

Static Load ◽

High Performance Concrete ◽

Precast Concrete ◽

Chloride Penetration ◽

Load Testing ◽

Test And Evaluation ◽

Load Tests ◽

Precast Elements

This paper presents a laboratory investigation on the performance of grouted rebar couplers with the connection details similar to those utilized on the precast concrete elements of the Keg Creek Bridge on US 6 in Iowa. The testing program consisted of a series of static load tests, a fatigue test, and evaluation of the chloride penetration resistance of laboratory specimens. The goal of this testing was to evaluate the ability of the grouted rebar couplers to develop flexural capacity at the joint between the precast elements as well as the durability of the connection. For structural load testing, seven full-scale specimens, each with #14 epoxy-coated rebars spliced by epoxy-coated grouted couplers, were fabricated and tested in three different loading cases: four-point bending, axial tension plus bending, and a cyclic test of the system in bending. The static load testing demonstrated that the applied axial load had a minimal effect on the formation of cracks and overall performance of the connection. When ultra-high performance concrete was used as a bedding grout, the initiation of crack was slightly delayed but no considerable improvement was observed in the magnitude of the crack width during loading or the crack closure on unloading. The results of the seventh specimen, tested in fatigue to 1 million cycles, showed little global displacement and crack width throughout the test, neither of which expanded measurably. No evidence of moisture or chloride penetration was detected at the grouted joint during the 6-month monitoring.

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