scholarly journals Effect of Different Types of Recycled Concrete Aggregates on Equivalent Concrete Strength and Drying Shrinkage Properties

2018 ◽  
Vol 8 (11) ◽  
pp. 2190 ◽  
Author(s):  
Sungchul Yang
Keyword(s):  
Compressive Strength ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Concrete Strength ◽  
Drying Shrinkage ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Test Results ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates

Residual mortar attached to recycled concrete aggregate (RCA) always leads to a decrease in Young’s modulus and an increase in the drying shrinkage of RCA concrete, mainly due to an increase of total mortar volume. To overcome this inherent problem, the modified and equivalent mortar volume (EMV) methods were proposed by researchers. Despite the comparable test results, both models are still subject to the slump loss problem. Thus, under the same W/C (water to cement ratio) ratio and slump condition, this study assessed the influence of the modified EMV mix method on RCA concrete properties. A total of six mixes were proportioned using the modified EMV method with three different RCAs. Test results show that the concrete mixed with RCA produced from old PC concrete sleepers exhibited compressive strength, Young’s modulus, and flexural strength values within 2% variation, equivalent to those values of the companion natural aggregate concrete. In other mixes, compressive strength was found to decrease to 11–20%. It was observed that for 100% replacement of RCA mix, Young’s modulus increased to 10% and drying shrinkage increased to 8% only, while for 50% replacement of RCA mix, Young’s modulus decreased to 8% and drying shrinkage dropped to 4%.

scholarly journals Natural aggregate totally replacement by mechanically treated concrete waste

2015 ◽  
Vol 10 (1) ◽  
pp. 83-90
Author(s):  
Jozef Junak ◽  
Nadezda Stevulova
Keyword(s):  
Compressive Strength ◽  
Concrete Strength ◽  
Reference Sample ◽  
Average Density ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregates ◽  
Recycled Material

Abstract This paper presents the results obtained from the research focused on the utilization of crushed concrete waste aggregates as a partial or full replacement of 4/8 and 8/16 mm natural aggregates fraction in concrete strength class C 16/20. Main concrete characteristics such as workability, density and compressive strength were studied. Compressive strength testing intervals for samples with recycled concrete aggregates were 2, 7, 14 and 28 days. The amount of water in the mixtures was indicative. For mixture resulting consistency required slump grade S3 was followed. Average density of all samples is in the range of 2250 kg/m3 to 2350 kg/m3. The highest compressive strength after 28 days of curing, 34.68 MPa, reached sample, which contained 100% of recycled material in 4/8 mm fraction and 60% of recycled aggregates in 8/16 mm fraction. This achieved value was only slightly different from the compressive strength 34.41 MPa of the reference sample.

scholarly journals Towards Better Understanding of Concrete Containing Recycled Concrete Aggregate

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Hisham Qasrawi ◽  
Iqbal Marie
Keyword(s):  
Concrete Strength ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
Normal Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Air Content ◽  
Significant Difference

The effect of using recycled concrete aggregates (RCA) on the basic properties of normal concrete is studied. First, recycled aggregate properties have been determined and compared to those of normal aggregates. Except for absorption, there was not a significant difference between the two. Later, recycled aggregates were introduced in concrete mixes. In these mixes, natural coarse aggregate was partly or totally replaced by recycled aggregates. Results show that the use of recycled aggregates has an adverse effect on the workability and air content of fresh concrete. Depending on the water/cement ratio and on the percent of the normal aggregate replaced by RCA, the concrete strength is reduced by 5% to 25%, while the tensile strength is reduced by 4% to 14%. All results are compared with previous research. As new in this research, the paper introduces a simple formula for the prediction of the modulus of elasticity of RCA concrete. Furthermore, the paper shows the variation of the air content of RAC.

scholarly journals Effect of River Indus Sand and Recycled Concrete Aggregates as Fine and Coarse Replacement on Properties of Concrete

2019 ◽  
Vol 9 (1) ◽  
pp. 3832-3835 ◽  
Author(s):  
A. R. Sandhu ◽  
M. T. Lakhiar ◽  
A. A. Jhatial ◽  
H. Karira ◽  
Q. B. Jamali
Keyword(s):  
Tensile Strength ◽  
Coarse Aggregate ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Compressive Strength Of Concrete ◽  
River Indus ◽  
Concrete Materials

As the demand for concrete rises, the concrete materials demand increases. Aggregates occupy 75% of concrete. A vast amount of aggregates is utilized in concrete while aggregate natural resources are reducing. To overcome this problem, River Indus sand (RIS) and recycled concrete aggregate (RCA) were utilized as fine and coarse aggregate respectively. The aim of this experimental investigation is to evaluate the workability, and compressive and tensile strength of concrete utilizing RIS and RCA. Concrete samples of 1:2:4 proportions were cast, water cured for 7, 14, 21 and 28 days, and tested for compressive and tensile strength. The outcomes demonstrate that concrete possessed less workability when RIS and RCA were utilized. It was predicted that compressive strength of concrete would reduce up to 1.5% when 50% RIS and 50% RCA were utilized in concrete and 11.5% when natural aggregate was fully replaced by RIS and RCA, whereas the tensile strength decreased up to 1.60% when 50% by 12% respectively.

Review of Studies concerning Effects of Unbound Crushed Concrete Bases on PCC Pavement Drainage

1996 ◽  
Vol 1519 (1) ◽  
pp. 51-58 ◽  
Author(s):  
Mark B. Snyder ◽  
James E. Bruinsma
Keyword(s):  
Drainage System ◽  
Field Studies ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Drainage Systems ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Crushed Concrete ◽  
Pavement Structures ◽  
Natural Aggregates

Recycled concrete aggregate (RCA) products are sometimes used as replacements for virgin aggregate products in concrete pavement structures. Recent concerns have centered on the deposit of RCA-associated fines and precipitate suspected of reducing the drainage capacity of RCA base layers and associated drainage systems. Environmental concerns have focused on the relatively high pH of the effluent produced by untreated RCA base layers. Several studies have examined these concerns and others; the results of some of these studies have not been published or publicized. The most relevant of these studies are summarized herein. These research efforts demonstrate that calcium-based compounds are present in most recycled concrete aggregates in quantities sufficient to be leached and precipitated in the presence of carbon dioxide. Precipitate potential appears to be related to the amount of freshly exposed cement paste surface. Thus, selective grading or blending with natural aggregates can reduce, but not eliminate, precipitate problems. It was also noted that insoluble, noncarbonate residue makes up a major portion of the materials found in and around pavement drainage systems. Washing the RCA products before using them in foundation layers appears to reduce the potential for accumulation of dust and other fines in the drainage system, but probably has little effect on precipitate potential. Field studies have shown that precipitate and insoluble materials can significantly reduce the permittivity of typical drainage fabrics but that attention to drainage design details can minimize the effects of these materials on pavement drainage.

scholarly journals Mechanical Behavior of a Composite Lightweight Slab, Consisting of a Laminated Wooden Joist and Ecological Mortar

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2575
Author(s):  
Carmelo Muñoz-Ruiperez ◽  
Francisco Fiol Oliván ◽  
Verónica Calderón Carpintero ◽  
Isabel Santamaría-Vicario ◽  
Ángel Rodríguez Sáiz
Keyword(s):  
Laboratory Test ◽  
Mechanical Behavior ◽  
Failure Load ◽  
Full Scale ◽  
Recycled Concrete ◽  
Test Results ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Laboratory Test Results ◽  
Lightweight Mortar

The investigation reported in this paper is an evaluation of the mechanical behavior of full-scale ecological mortar slabs manufactured with a mixture of expanded clay and recycled concrete aggregates. The composite mortars form a compressive layer over laminated wooden joists to form a single construction unit. To do so, full-scale flexural tests are conducted of the composite laminated wood-ecological mortar slabs with different types of mortar designs: reference mortar (MR), lightweight mortar dosed with recycled concrete aggregates (MLC), and lightweight mortar dosed with recycled mixed aggregates (MLM). The test results showed that the mortar forming the compression layer and the laminated wooden joists worked in unison and withstood a higher maximum failure load under flexion than the failure load of the wooden joists in isolation. Moreover, the laboratory test results were compared with the simulated values of the theoretical model, generated in accordance with the technical specifications for structural calculations contained in the Spanish building code, and with the results calculated by a computer software package. From the analysis of the results of the calculation methods and the full-scale laboratory test results, it was concluded that the safety margin yielded by the calculations validated the use of those methods on this type of composite slab. In this way, a strong mixed wood–mortar slab was designed, contributing little dead-load to the building structure and its manufacture with recycled aggregate, also contributes to the circular economy of construction materials.

Modified recycled concrete aggregates for asphalt mixture using microbial calcite precipitation

RSC Advances ◽  
2015 ◽  
Vol 5 (44) ◽  
pp. 34854-34863 ◽  
Author(s):  
Zhong-Yao Pan ◽  
Gengying Li ◽  
Cheng-Yu Hong ◽  
Hui-Ling Kuang ◽  
Yu Yu ◽  
...  
Keyword(s):  
Bonding Strength ◽  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate ◽  
Calcite Precipitation ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Porosity And Permeability

Recycled concrete aggregate (RCA) was pretreated by microbial calcite precipitation. The surface treatment reduced the porosity and permeability of RCA by 32% and 86.5%, respectively. The treatment improved the bonding strength of RCA–asphalt binder by 55%.

The Research of Green High Performance Recycled Construct Materials

2011 ◽  
Vol 71-78 ◽  
pp. 4471-4475
Author(s):  
Xiao Xiong Zha ◽  
Kai Zhang
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Experimental Studies ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Large Water

Recycled concrete aggregates have large porosity, large water absorption and high crush index. Mechanical properties of recycled concrete aggregates could be improved by adding activated water instead of ordinary water. On the basis of the experimental studies, this paper analyzes the influences on recycled concrete compression strength when using activated water. There are many different factors such as the kinds and amounts of alkali and the water slag ratio affecting the compressive strength of recycle geopolymer. The results show that activated water has a high enhancement on compressive strength of recycled aggregate concrete, and the highest compressive strength of recycled geopolymer is 57.3MPa.

Experimental Study on Fundamental Characteristic of Recycled Concrete

2010 ◽  
Vol 146-147 ◽  
pp. 1925-1929
Author(s):  
Yuan Xu ◽  
Ru Heng Wang ◽  
Hua Chuan Yao
Keyword(s):  
Fly Ash ◽  
Maximum Size ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Fundamental Characteristic ◽  
Recycled Concrete Aggregate ◽  
Application Process ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Rock

First, the fundamental characteristic of recycled concrete aggregate wasstudied. Then, the recycled concrete spiciemen with different maximum size was tested. The results showed that: the apparent density and bulk density of recycled concrete aggregates was smaller than the natural rock, but the moisture content, crushed index, water absorption was higher. The workability of recycled concrete improved with increase of water and fly ash, but its strength decreased as the increase of water and fly ash. The research on performance and strength of recycled concrete aggregate will provide certain theoretical basis in the application process.

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.

Potential water pollution from recycled concrete aggregate material

2021 ◽  
Vol 72 (1) ◽  
pp. 58
Author(s):  
K. Purdy ◽  
J. K. Reynolds ◽  
I. A. Wright
Keyword(s):  
Water Contamination ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate ◽  
Water Pipe ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Road Base ◽  
Final Treatment ◽  
Aggregate Material

Recycled concrete aggregates (RCA) are a widely used recycled building material. RCA materials have many uses such as a road base or backfilling trenches. Our study investigated the potential water-contamination risks of water exposed to RCA materials. We recirculated water for 60min through four different treatments. Two treatments were a PVC gutter filled with different size grades of RCA material (20mm and 45mm), the third treatment was a clean PVC gutter and the fourth and final treatment was an unused concrete water pipe. Results showed that RCA material exposed to water released a suite of contaminants that could be ecologically hazardous to aquatic species. RCA leached metals over the 60-min recirculation (aluminium, arsenic, barium, chromium, lead, manganese, molybdenum, titanium, lithium and strontium). Water exposed to RCA material exceeded aquatic ecosystem guidelines for aluminium by 50 times and lead by up to 12 times. RCA materials increased pH by up to 4.35 pH units and electrical conductivity (EC) by up to 11 times the starting EC (mean 27.9 µs cm–1). We suggest that RCA materials need to be used with caution in settings that could be exposed to water and flow to waterways of conservation value.

Sign in / Sign up

Export Citation Format

Share Document