Related Experiment Video
Updated: Jan 28, 2026
10:00
Experimental Protocol to Determine the Chloride Threshold Value for Corrosion in Samples Taken from Reinforced Concrete Structures
Published on: August 31, 2017
16.0K
Microstructural Features of Recycled Aggregate Concrete: From Non-Structural to High-Performance Concrete
Diogo Pedro1, Mafalda Guedes2, Jorge de Brito1
1CERIS, Instituto Superior Técnico, Universidade de Lisboa,Av. Rovisco Pais, 1049-001 Lisboa,Portugal.
Summary
Recycled concrete aggregates (RCA) can produce high-performance concrete comparable to natural aggregates (NA). This study links microstructure analysis to mechanical properties, confirming RCA
Area of Science:
- Materials Science
- Civil Engineering
- Sustainable Construction
Background:
- Producing high-performance concrete using recycled concrete aggregates (RCA) is hindered by a lack of correlation between microstructure and mechanical performance reproducibility.
- Understanding the microstructural characteristics of concrete with RCA is crucial for optimizing its mechanical properties and ensuring consistent performance.
Purpose of the Study:
- To systematically analyze and characterize concrete microstructure using scanning electron microscopy.
- To correlate microstructural findings with concrete compressive strength and water absorption.
- To investigate the influence of replacing natural aggregates (NA) with RCA (from various source strengths), silica fume (SF) addition, and mixing procedures on concrete properties.
Main Methods:
- Systematic analysis and characterization of concrete microstructure via scanning electron microscopy.
- Correlation of microstructural data with mechanical performance indicators (compressive strength, water absorption).
- Experimental testing of concrete mixes with varying proportions of RCA, SF, and different mixing protocols.
Main Results:
- Microstructure development is dependent on concrete composition and the nature of aggregates (NA, high-strength RCA, low-strength RCA).
- Silica fume (SF) enhanced concrete densification only when a two-stage mixing approach was employed.
- Concrete with 100% RCA achieved a compressive strength of 97.3 MPa, comparable to conventional high-strength concrete using NA.
Conclusions:
- The study establishes a clear link between concrete microstructure and mechanical performance when using RCA.
- High-performance concrete utilizing significant amounts of RCA is achievable, meeting environmental objectives.
- RCA is a viable alternative to NA for producing high-performance concrete, demonstrating its sustainability and technical feasibility.
Related Concept Videos
01:29Preplaced Aggregate Concrete
378
Preplaced aggregate concrete is ideal for construction environments that are not easily accessible. The process begins by properly wetting the gap-graded coarse aggregates to remove the dirt, then placing it in the form and compacting it. Voids are filled with a mortar mix pumped under pressure through slotted pipes. This mortar typically consists of Portland cement, pozzolan, fine aggregates, water, and a fluidizing aid. The pozzolan helps reduce bleeding and segregation while improving the...
378
01:26Alkali Aggregate Reaction in Concrete
527
The alkali-aggregate reaction in concrete involves natural siliceous minerals in aggregates reacting with alkaline hydroxides derived from cement alkalis. This reaction forms an alkali-silica gel that absorbs water, swells, and increases in volume, which is confined by the surrounding cement paste, creating internal pressures that crack and disrupt the concrete. The extent of expansion and damage can be partly attributed to the alkali-silica reaction's osmotic hydraulic pressure and the...
527
01:28Types of Non-structural Cracks in Concrete
498
Non-structural cracks are primarily of three types: plastic, early-age thermal, and drying shrinkage cracks. Plastic cracks are further classified into plastic shrinkage cracks and plastic settlement cracks.
Plastic shrinkage cracks typically form within hours after the concrete is poured. The concrete's surface dries faster than the bottom, creating tensile stress that the still-plastic concrete cannot withstand, leading to diagonal or randomly patterned cracks on the concrete surface.
Plastic shrinkage cracks typically form within hours after the concrete is poured. The concrete's surface dries faster than the bottom, creating tensile stress that the still-plastic concrete cannot withstand, leading to diagonal or randomly patterned cracks on the concrete surface.
498
01:20Concrete
797
Concrete is a vital construction material extensively used worldwide, primarily valued for its strength, durability, and versatility, which it provides for various structural designs. Concrete generally comprises ingredients like Portland cement, coarse gravel, fine sand, and water. Concrete can be mixed by simple hand methods or industrially at computer-controlled plants. The mixture consists of aggregates and a paste made from water and Portland cement. This paste coats the aggregates and,...
797
01:25Workability of Concrete
421
The workability of concrete is a crucial property that affects its handling, placing, and finishing during construction. It describes the ease with which concrete can be mixed, placed, compacted, and finished. Workability is primarily concerned with the concrete's movement and its ability to resist internal friction and external resistance from molds and reinforcements during the application process.
Concrete's workability is determined by its resistance to internal forces that arise...
Concrete's workability is determined by its resistance to internal forces that arise...
421
01:25Reinforcements in Concrete
461
Reinforced concrete is a composite material used extensively in construction, combining the compressive strength of concrete with the tensile strength of steel. This synergy is essential as concrete, while excellent at resisting compression, is weak under tension. Steel bars, or rebars, are embedded in the concrete to handle these tensile forces. The choice of steel is strategic; it shares a similar coefficient of thermal expansion with concrete, which ensures uniformity in response to...
461