scholarly journals Study on the Microstructure of the New Paste of Recycled Aggregate Self-Compacting Concrete

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2114
Author(s):  
Kheira Zitouni ◽  
Assia Djerbi ◽  
Abdelkader Mebrouki
Keyword(s):  
Mercury Intrusion Porosimetry ◽  
Strength Loss ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Self Compacting Concrete ◽  
Mercury Intrusion ◽  
Concrete Mixtures ◽  
Binder Ratio ◽  
Water To Binder Ratio ◽  
Different Levels

Previous literature indicates a decrease in the mechanical properties of various concrete types that contain recycled aggregates (RA), due to their porosity and to their interface of transition zone (ITZ). However, other components of the RA concrete microstructure have not yet been explored, such as the modification of the new paste (NP) with respect to a reference concrete. This paper deals with the microstructure of the new paste of self-compacting concrete (SCC) for different levels of RA. The water to binder ratio (w/b) was kept constant for all concrete mixtures, and equal to 0.5. The SCC mixtures were prepared with percentages of coarse RA of 0%, 30%, 50% and 100%. Mercury intrusion porosimetry test (MIP) and scanning electron microscope (SEM) observations were conducted on the new paste of each concrete. The results indicated that the porosity of the new paste presents a significant variation for replacement percentages of 50% and 100% with respect to NP0 and NP30. However, RA contributed to the refinement of the pore structure of the new paste. The amount of macrospores the diameter of which is in the 50–10,000 nm range was reduced to 20% for NP50 and NP100, while it was about 30% for NP0 and NP30, attributed to the water released by RA. Compressive strength loss for SCC50 and SCC100 concretes are both influenced by porosity of RA, and by the NP porosity. The latter is similar for these two concretes with the 26% increase compared to a reference concrete.

scholarly journals Effect of the Key Mixture Parameters on Shrinkage of Reactive Powder Concrete

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Shamsad Ahmad ◽  
Ahmed Zubair ◽  
Mohammed Maslehuddin
Keyword(s):  
Empirical Equation ◽  
Cementitious Materials ◽  
Reactive Powder Concrete ◽  
Test Results ◽  
Total Period ◽  
Concrete Mixtures ◽  
Binder Ratio ◽  
Reactive Powder ◽  
Water To Binder Ratio ◽  
Different Levels

Reactive powder concrete (RPC) mixtures are reported to have excellent mechanical and durability characteristics. However, such concrete mixtures having high amount of cementitious materials may have high early shrinkage causing cracking of concrete. In the present work, an attempt has been made to study the simultaneous effects of three key mixture parameters on shrinkage of the RPC mixtures. Considering three different levels of the three key mixture factors, a total of 27 mixtures of RPC were prepared according to 33factorial experiment design. The specimens belonging to all 27 mixtures were monitored for shrinkage at different ages over a total period of 90 days. The test results were plotted to observe the variation of shrinkage with time and to see the effects of the key mixture factors. The experimental data pertaining to 90-day shrinkage were used to conduct analysis of variance to identify significance of each factor and to obtain an empirical equation correlating the shrinkage of RPC with the three key mixture factors. The rate of development of shrinkage at early ages was higher. The water to binder ratio was found to be the most prominent factor followed by cement content with the least effect of silica fume content.

Rheological Behavior of Self-Compacting Geopolymer Concrete Containing Recycled Aggregates: Effect of Na2SiO3/NaOH and Molarity of NAOH

2021 ◽  
Vol 872 ◽  
pp. 79-84
Author(s):  
Koran Salihi ◽  
Khaleel H. Younis
Keyword(s):  
Sodium Hydroxide ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Geopolymer Concrete ◽  
Fresh Properties ◽  
Self Compacting Concrete ◽  
Sustainable Concrete ◽  
Coarse Aggregates ◽  
Concrete Mixtures ◽  
Fresh State

To develop a sustainable concrete and to minimize the depletion of the natural resources, an attempt was made to develop sustainable concrete mixtures benefiting from the geopolymer technology and the use of recycled aggregate in self-compacting geopolymer concrete (SCGC). This study aim to examine the effects of sodium hydroxide (SH) molarity and sodium silicate (Na2SiO3)/ sodium hydroxide (SS/SH) ration the fresh properties of SCGC mixtures containing recycled coarse aggregates (RCA) Mixes were prepared with three different molarity (8M, 10M and 12M) of) and four SS/SH ratios (1.5, 2.0, 2.5 and 3.0). Six mixes were examined in this study. The results were compared with the EFNARC limits for self-compacting concrete (SCC). It was found that the SS/SH ratio and the molarity of SH affect the fresh properties of (SCGC). However, the results showed that, SCGC mixtures containing RCA can be developed and satisfy the requirements of EFNARC for fresh state of SCC.

Study on the Compression Capacity of the Wall of Recycled Aggregates Self-Compacting Rock-Filled Concrete

2013 ◽  
Vol 438-439 ◽  
pp. 719-723
Author(s):  
Hai Chao Wang ◽  
Yi Long Gao ◽  
Xue Hui An
Keyword(s):  
Bearing Capacity ◽  
Testing Machine ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Wall Material ◽  
Self Compacting Concrete ◽  
Concrete Wall ◽  
Mortar Strength ◽  
Deformation Properties

The goal of the paper is to make good use of solid wastes. The aggregates of ordinary self-compacting concrete are changed for the large size of recycled aggregate, which are randomly put into the mold before self-compacting concrete are poured into to form the new type of concrete specimens, and a freestone aggregate specimen is also made for a comparison. 500 tons of electro-hydraulic servo testing machine is used for the test, to measure the strength of this new wall material, bearing capacity, deformation properties and damage form, etc. Test results show that the average compressive strength of the wall of recycled aggregate rock-filled concrete is 6.42MPa, which is far greater than 2.03MPa specified in standard under same mortar strength. Therefore, the recycled aggregate concrete wall of self-compacting has higher bearing capacity, and can meet the requirment of the project.

scholarly journals Self-Compacting Concrete with Recycled Coarse Aggregate and Manufactured Sand

2019 ◽  
Vol 9 (1) ◽  
pp. 3868-3873
Keyword(s):  
Coarse Aggregate ◽  
Recycled Aggregate ◽  
Fine Aggregate ◽  
Fresh Properties ◽  
Self Compacting Concrete ◽  
Manufactured Sand ◽  
Recycled Coarse Aggregate ◽  
Recycle Coarse Aggregate ◽  
Binder Ratio ◽  
Water Binder Ratio

This article mainly focused on the influence of recycle coarse aggregate and manufactured sand on the properties of self compacting concrete (SCC). The main purpose of this research is reuse of recycled aggregate in SCC and also to reduce use of fine aggregate by replacing manufactured sand. The SCC mixtures were prepared with 0, 25, 50, 75 and 100% replacement of recycle coarse aggregate in natural coarse aggregate and M-Sand in fine aggregate with a Water/Binder ratio of 0.36. Different test covering fresh properties of these SCC mixtures were executed the results were compared with EFNARC guidelines and IS 10262:2019. The feasibility of utilizing recycled aggregate and M-Sand in self compacting concrete has been examined and found that it is suitable for concrete.

scholarly journals Evaluation of the physical-mechanical properties of cement-lime based masonry mortars produced with mixed recycled aggregates

2020 ◽  
Vol 70 (337) ◽  
pp. 210 ◽  
Author(s):  
R. L.S. Ferreira ◽  
M. A.S. Anjos ◽  
E. F. Ledesma ◽  
J. E.S. Pereira ◽  
A. K.C. Nóbrega
Keyword(s):  
Mechanical Properties ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Demolition Waste ◽  
Long Run ◽  
Lime Mortars ◽  
Binder Ratio ◽  
Mechanical Strengths ◽  
One Way Anova

This study investigated the physical-mechanical effects of cement-lime mortars containing recycled aggregate of construction and demolition waste (CDW). The natural aggregate (NA) was replaced by volume at 25%, 50%, 75% and 100% by mixed recycled aggregate (MRA) obtained from the CDW crushing. Five types of mortars were prepared with a volumetric ratio of 1:1:6 (cement, lime and aggregate) and water/binder ratio based on the fixed consistency of 260 mm. The effects of MRA on fresh and hardened mortars’ properties were analyzed. The results were analyzed using a one-way ANOVA. MRA incorporation improved most of the physical-mechanical properties of mortars tested, except for hardened bulk density, water absorption and porosity. In the long-run, mechanical strengths significantly increased in all compositions, especially those with higher percentages of MRA. The results obtained showed that the use of MRA in masonry mortars is an alternative to reduce the generation of waste and consumption of natural resources.

scholarly journals Evaluation of Concrete Strength Made with Recycled Aggregate

Buildings ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 56 ◽  
Author(s):  
Haitham Al Ajmani ◽  
Ferass Suleiman ◽  
Ismail Abuzayed ◽  
Adil Tamimi
Keyword(s):  
Construction Industry ◽  
Coarse Aggregate ◽  
Concrete Strength ◽  
Recycled Aggregate ◽  
Penetration Test ◽  
Binder Ratio ◽  
Hardened Properties ◽  
Water To Binder Ratio ◽  
Micro Silica ◽  
Good Workability

The construction industry consumes enormous quantities of concrete, which subsequently produces large amount of material waste during production and demolishing. As a result, the colossal quantity of concrete rubble is disposed in landfills. This paper, therefore, evaluated the feasibility of reusing waste concrete as recycled aggregate (RA) to produce concrete. The replacement levels were 20, 50, and 80% RA of normal coarse aggregate. Micro silica (MS) and fly ash (FA) were used as cementitious replacement material, however, the water-to-binder ratio (w/b) was kept constant at 0.31. A total of 44 specimens were used to evaluate the fresh and hardened properties. Concrete with 80% RA showed good workability and mechanical properties. The compressive strength of the concrete with 80% RA was 60 MPa at 28 days and 77 MPa at 56 days. Rapid chloride penetration test (RCPT) was also conducted, where the concrete with 80% RA had the lowest permeability.

scholarly journals Shrinkage and porosity in concretes produced with recycled concrete aggregate and rice husk ash

2019 ◽  
Vol 12 (3) ◽  
pp. 694-704
Author(s):  
V. CECCONELLO ◽  
B. R. C.SARTORI ◽  
M. P .KULAKOWSKI ◽  
C. S. KAZMIERCZAK ◽  
M. MANCIO
Keyword(s):  
Rice Husk ◽  
Rice Husk Ash ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Concrete Aggregate ◽  
Supplementary Cementitious Material ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Binder Ratio ◽  
Water To Binder Ratio

Abstract The admixture of recycled concrete aggregates (RCA) in new concretes is an interesting alternative in the efforts to mitigate environmental impacts. RCA may increase porosity and change properties of concretes. Rice husk ash (RHA) is employed as supplementary cementitious material may improve concrete properties. The present study investigated the shrinkage of concrete prepared with RCA and RHA, proposing a mathematical model to explain the phenomenon. Concretes were produced with 25% and 50% of coarse recycled aggregate as replacement of natural aggregate, 0%, 10%, and 20% of RHA as replacement of cement, and a water-to-binder ratio of 0.64. Water absorption and capillary and total porosities were analyzed on day 28. Shrinkage tests were conducted on days 1, 4, 7, 14, 28, 63, 91, and 112. The results point to a significant interaction between RHA and RCA.

scholarly journals Effect of Design Parameters on Compressive and Split Tensile Strength of Self-Compacting Concrete with Recycled Aggregate: An Overview

2021 ◽  
Vol 11 (13) ◽  
pp. 6028
Author(s):  
P. Jagadesh ◽  
Andrés Juan-Valdés ◽  
M. Ignacio Guerra-Romero ◽  
Julia M. Morán-del Morán-del Pozo ◽  
Julia García-González ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Design Parameters ◽  
Fine Aggregate ◽  
Self Compacting Concrete ◽  
Split Tensile Strength ◽  
Coarse Aggregates ◽  
Fine Aggregates

One of the prime objectives of this review is to understand the role of design parameters on the mechanical properties (Compressive and split tensile strength) of Self-Compacting Concrete (SCC) with recycled aggregates (Recycled Coarse Aggregates (RCA) and Recycled Fine Aggregates (RFA)). The design parameters considered for review are Water to Cement (W/C) ratio, Water to Binder (W/B) ratio, Total Aggregates to Cement (TA/C) ratio, Fine Aggregate to Coarse Aggregate (FA/CA) ratio, Water to Solid (W/S) ratio in percentage, superplasticizer (SP) content (kg/cu.m), replacement percentage of RCA, and replacement percentage of RFA. It is observed that with respect to different grades of SCC, designed parameters affect the mechanical properties of SCC with recycled aggregates.

Research on Self-Compacting Concrete Made with Recycled Aggregate

2013 ◽  
Vol 639-640 ◽  
pp. 399-403
Author(s):  
Ai Guo Zhou ◽  
Jian Yin ◽  
Wei Min Song ◽  
Yi Chi
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Coarse Aggregate ◽  
Recycled Aggregate ◽  
Self Compacting Concrete ◽  
Recycled Coarse Aggregate ◽  
Coarse Aggregates ◽  
Mineral Additive ◽  
Binder Ratio ◽  
Water Binder Ratio

It is studied the effect of binder quantity, water binder ratio on properties of self-compacting concrete made with recycled coarse aggregates. It can be prepared C50 self-compacting concrete made with recycled coarse aggregate by adjusting send proportion, binder quantity, and mixing mineral additive. For example, when the binder quantity is 600 kg/m3, water binder ratio is 0.28, the flexural strength and compressive strength at 28 days of self-compacting concrete made with recycled coarse aggregates are 9.07 MPa and 68.47 MPa respectively.

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