Effects of Recycled Coarse Aggregates on the Carbonation Evolution of Concrete

2009 ◽  
Vol 417-418 ◽  
pp. 697-700
Author(s):  
Jian Zhuang Xiao ◽  
Bin Lei ◽  
Chuan Zeng Zhang
Keyword(s):  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Test Results ◽  
Coarse Aggregates ◽  
Cover Concrete ◽  
New Information ◽  
Carbonation Resistance ◽  
Environmental Actions ◽  
Corrosion Of Steel

Concrete exposing to atmosphere suffers from changes in its internal structure, for instance loss of alkalinity of the cover concrete and corrosion of steel rebar due to carbonation, which in extreme cases affect the safety, the reliability and the durability or the service life of the structure. Carbonation is one of the key environmental actions that may cause structural failure. This study aims to gain some new information on the carbonation resistance when recycled coarse aggregates are used to mix new concrete. The concrete’s resistance to carbonation is determined by measuring the carbonation depth of 100mm×100mm×300mm concrete prisms in according to GBJ 82-85. Two series of tests including 9 groups of recycled aggregate concrete specimens are carried out, in which the effects of the quality and replacement of recycled coarse aggregates on the carbonation behavior of recycled concrete are evaluated. The essential test results are presented and discussed in this paper. Based on the findings of the present study, in order to reduce the unfavorable effects of recycled coarse aggregates on the recycled concrete, limiting the compressive strength grade of original concrete and the replacement of recycled coarse aggregate is a good option under the condition of using recycled concrete in considered projects.

Study on the Basic Mechanical Properties of Recycled Concrete Hollow Block Masonry

2013 ◽  
Vol 438-439 ◽  
pp. 749-755 ◽  
Author(s):  
Tong Hao ◽  
Dong Li
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Shear Behavior ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Test Results ◽  
Aggregate Concrete ◽  
Mortar Strength ◽  
Hollow Block

By the experimental studying on the basic mechanical properties of recycled concrete hollow block masonry, the compressive and shear behavior of recycled aggregate concrete hollow block masonry under different mortar strength were analyzed. Research indicated that the compressive and shear behavior of recycled aggregate concrete hollow block masonry was similar to that of ordinary concrete hollow block masonry. The normal formula was recommended to calculate the compressive strength of the masonry. The shear strength of the masonry was affected by the mortar strength. The shear strength calculation formula of recycled concrete hollow block masonry was proposed according to the formula of masonry design code. The calculating results were in good agreement with the test results.

scholarly journals Reliability-Based Analysis of Recycled Aggregate Concrete under Carbonation

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Flora Faleschini ◽  
Mariano Angelo Zanini ◽  
Lorenzo Hofer
Keyword(s):  
Prediction Models ◽  
Probabilistic Method ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Replacement Ratio ◽  
Carbonation Depth ◽  
Aggregate Concrete ◽  
Carbonation Resistance ◽  
Environmental Actions ◽  
Experimental Works

Durability represents a crucial issue for evaluating safety and serviceability of reinforced concrete structures. Many studies have already focused on carbonation-induced corrosion of natural aggregate concrete (NAC) structures, leading to several prediction models to estimate carbonation depth. Less research is devoted instead on recycled aggregate concrete (RAC), about which limited experimental works exist aimed at assessing the carbonation coefficient in accelerated tests. Additionally, deteriorating processes are subject to uncertainty, when defining materials, geometry, and environmental actions during the service life of structures. This work presents a reliability-based analysis of carbonation resistance of RACs, using experimental carbonation coefficients derived from the literature, and applied in the full-probabilistic method prosed in fib Bulletin 34. Results demonstrate how aggregates replacement ratio and w/c ratio influence the reliability of RAC carbonation resistance.

scholarly journals Study on interface characteristics and frost resistance of recycled concrete

2019 ◽  
Vol 79 ◽  
pp. 02004
Author(s):  
Ying Liu ◽  
Peng Peng
Keyword(s):  
Frost Resistance ◽  
Coarse Aggregate ◽  
Structural Characteristics ◽  
Damage Mechanism ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Test Results ◽  
Resistance Property ◽  
Interface Characteristics

The structural characteristics of recycled aggregate concrete and its damage mechanism have been analyzed in this paper. The recycled aggregate has been classified into three types through particle shaping and then frost resistance property of recycled concrete with different cement volume has been analyzed through the test. According to the test results, frost resistance property of the recycled concrete is C >B >A, therefore, particle shaping can obviously improve quality and durability of the recycled coarse aggregate.

Microscopic Mechanism Study on Carbonation Resistance of Recycled Aggregate Concrete

2011 ◽  
Vol 194-196 ◽  
pp. 1001-1006 ◽  
Author(s):  
Hai Feng Yang ◽  
Zhi Heng Deng ◽  
Xue Liang Li
Keyword(s):  
Fly Ash ◽  
Coarse Aggregate ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Replacement Rate ◽  
Aggregate Concrete ◽  
Recycled Coarse Aggregate ◽  
Concrete Carbonation ◽  
Carbonation Resistance

24 100mm × 100mm × 300mm recycled concrete prisms and 96 150mm × 150mm × 150mm cubes are completed in this paper.The relationships of the carbonation depth in each carbonation age with replacement rate of recycled coarse aggregate and fly ash is studied; The SEM is used to observe the interface structure of recycled coarse aggregate concrete and compared with ordinary concrete, and finally,a recycled concrete carbonation model is proposed. The results showed that: the substitution of recycled coarse aggregate and fly ash cut down the recycled concrete carbonation resistance significantly, which are related with the replacement rate; the content of Ca(OH)2 in the recycled aggregate concrete decreased ,also there are obvious interface transition zone between the recycled coarse aggregate and the new cement;obvious cracks and large voids are exist before the recycled aggregate concrete is loaded, which lead directly to lower carbonation resistance of the recycled concrete.

scholarly journals Impact of the Content Variation of the Different Recycled Wastes to the Properties of Concrete Paving Block

2018 ◽  
Vol 206 ◽  
pp. 02004 ◽  
Author(s):  
X Wang ◽  
C S Chin ◽  
J Xia
Keyword(s):  
Water Absorption ◽  
Coarse Aggregate ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Coarse Aggregates ◽  
Content Variation ◽  
The Impact

Recycled concrete aggregates have been widely studied and used in concrete products nowadays. However, other recycled wastes, such as glass, have not been involved too much in recycled aggregate concrete studies. This paper aims to study the impact of the content variation of the different recycled wastes to the properties of the concrete paving block. In this paper, not only recycled coarse concrete aggregates, crushed glass are also used as the recycled aggregate in the concrete paving block in different replacement levels. According to test the properties of blocks mixed with different recycled wastes, the experimental results indicate that: (1) adding recycled concrete coarse aggregate (RCCA) in the blocks can decrease the blocks’ strength, and increase the water absorption. The suggested replacement levels for RCCA is 60%; (2) mixing crushed glass (CG) in the concrete paving blocks as a type of coarse aggregates can obviously improve the blocks’ strength and decrease the blocks’ water absorption.

scholarly journals Utilization of Demolished Waste as Coarse Aggregate in Concrete

2019 ◽  
Vol 5 (3) ◽  
pp. 540 ◽  
Author(s):  
Abdulsamee M Halahla ◽  
Mohammad Akhtar ◽  
Amin H. Almasri
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Recycled Concrete ◽  
International Standards ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Test Results ◽  
Aggregate Concrete ◽  
Natural Aggregate ◽  
Concrete Building

Demolishing concrete building usually produces huge amounts of remains and wastes worldwide that have promising possibilities to be utilized as coarse aggregate for new mixes of concrete. High numbers of structures around the world currently need to be removed for several reasons, such as reaching the end of the expected life, to be replaced by new investments, or were not built by the local and international standards. Maintaining or removal of such structures leads to large quantities of concrete ruins. Reusing these concrete wastes will help in saving landfill spaces in addition to more sustainability in natural resources. The objective of this study is to investigate the possibility of using old recycled concrete as coarse aggregate to make new concrete mixes, and its effect on the evolution of the compressive strength of the new concrete mixes.  Core samples for demolished concrete were tested to determine its compressive strength. The core test results can be thought of as aggregate properties for the new concrete. Then, the compressive strength and splitting tensile strength of the new recycled aggregate concrete (RAC) were determined experimentally by casting a cubes and cylinders, respectively. It was found that the evolution of compressive strength of recycled aggregate concrete is similar in behavior to the concrete with natural aggregate, except that it is about 10% lower in values. It was also seen that water absorption for recycled aggregate is noticeably higher than that for natural aggregate, and should be substituted for in the mix design.

Effects of Recycled Aggregate Replacement Rate on Compression Mechanical Behavior of Concrete Based on Base Force Element Method

2021 ◽  
Vol 894 ◽  
pp. 121-126
Author(s):  
Li Ping Ying ◽  
Yi Jiang Peng
Keyword(s):  
Failure Process ◽  
Strain Curve ◽  
Simple Algorithm ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Concrete Aggregate ◽  
Test Results ◽  
Force Element ◽  
Element Method

A meso-analysis method which is derived from the base force element method (BFEM) was proposed for recycled aggregate concrete (RAC). A simple algorithm was used to generate the convex recycled concrete aggregate (RCA) model. Uniaxial compression numerical simulations were carried out on the numerical specimens with different replacement rates of RCA. The model predictions were in a good agreement with the test results. The proposed method is very promising. It can totally predict the full stress-strain curve of RAC, as well as the failure process and failure mode, including strain softening and strain localization.

The Carbonation Depth of Fine Recycled Aggregate Concrete

2016 ◽  
Vol 722 ◽  
pp. 228-232 ◽  
Author(s):  
Magdaléna Šefflová ◽  
Tereza Pavlů
Keyword(s):  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Partial Replacement ◽  
Concrete Durability ◽  
Test Results ◽  
Carbonation Depth ◽  
Natural Sand ◽  
Conventional Concrete ◽  
Concrete Mixtures ◽  
Carbonation Resistance

This paper is focused on carbonation resistance of fine recycled aggregate (FRA) concrete. Durability of FRA concrete is connected with uncertainties and doubts. One of the most unknown aspects of FRA cocnrete is carbonation resistance. This paper presents results of carbonation depth of FRA concrete. The FRA was originated from crushed construction and demolition (C&D) waste. There were prepared a total four concrete mixture. The first mixture was reference, did not include the FRA. In other concrete mixtures, natural sand was replaced by the FRA in various replacement ratios, specifically 10%, 20% and 30%. All prepared concrete mixtures were designated with the same parameters for clear comparison. From the test results it is possible to say that the use of the FRA as partial replacement of natural sand in concrete influences carbonation resistance of concrete. The carbonation depth was higher for concrete samples with the use of FRA. However it is possible to say that according to the carbonation resistance, the FRA concrete is possible to be used in the same applications as conventional concrete but it is necessary to verify this results.

Fire Damage and Residual Strengths of Recycled Aggregate Concrete

2007 ◽  
Vol 348-349 ◽  
pp. 937-940 ◽  
Author(s):  
Jian Zhuang Xiao ◽  
Chuan Zeng Zhang
Keyword(s):  
Thermal Cycle ◽  
Elevated Temperatures ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Fire Damage ◽  
Aggregate Concrete ◽  
Failure Patterns ◽  
Damage And Failure ◽  
Coarse Aggregates

In this paper, recycled aggregate concrete subjected to severe fire or high temperature loading condition is investigated. Special attention of the study is devoted to analyze the fire-induced damage and the residual strengths of recycled aggregate concrete. For this purpose, 160 cube specimens are heated under a single thermal cycle of 20oC (ambient temperature), 200oC, 300oC, 400oC, 500oC, 600o, 700oC and 800oC, respectively. Different replacement percentages of the recycled coarse aggregates (RCA) with 0, 30%, 50%, 70% and 100% are considered. Damage and failure patterns of the recycled aggregate concrete specimens are analyzed systematically based on experimental observations. The residual compressive strengths of the recycled aggregate concrete (RAC) at elevated temperatures are studied and evaluated in details. Some differences between the recycled aggregate concretes with different replacement percentages of the recycled coarse aggregates are observed. On the basis of the experimentally measured residual compressive strengths of the recycled concrete, relationships between the residual compressive strengths of the recycled aggregate concrete and the elevated temperature are derived. The results presented in this paper have direct applications in the design and structural analysis of reinforced concrete structures consisting of recycled aggregate concrete.

scholarly journals Coefficient of Thermal Expansion of RCA Concrete Made by Equivalent Mortar Volume

2021 ◽  
Vol 11 (17) ◽  
pp. 8214
Author(s):  
Sungchul Yang ◽  
Hyewon Lee
Keyword(s):  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Relative Increase ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Concrete Aggregate ◽  
Test Results ◽  
Replacement Ratio ◽  
Aggregate Concrete

The present study was conducted to experimentally verify if the coefficient of thermal expansion (COTE) of recycled aggregate concrete is proportional to the volume of the original virgin aggregate in the total recycled aggregate concrete mix. Three types of recycled concrete aggregate (RCA) were crushed from: railroad concrete sleepers; precast (PC) culverts; commercial recycling plant. RCA concretes were mixed using two concrete mixing methods: conventional mix method and equivalent mortar volume (EMV) method. And by varying the replacement ratio, three test series were made. Test results showed that at the same RCA replacement ratio of 68%, the COTE of RCA concrete prepared by the EMV mix design was over 6–7% lower than that of RCA concrete made with the conventional mix method. It was also similar to or 1–2% lower than that of the natural coarse aggregate concrete. This may be because the conventional mix method does not take into account the residual mortar content attached to RCA. This results in a decrease in the volumetric ratio of the original virgin aggregate and a relative increase in the volumetric ratio of the mortar (or cement paste).

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