Demolition Waste Aggregates Research Articles

The Influence of Crushed Concrete Demolition Waste Aggregates on the Hardening Process of Concrete Mixtures

Concrete – complex structure composite material consisting of the components with various structure and size. Not only coarse and fine aggregates are used in concrete production, but also filler aggregates. Aggregates of natural, man-made origin or aggregates, produced from recycled materials, can be utilised in concrete production. Aggregates can be produced from recycled materials by reprocessing of concrete and reinforced concrete waste. The influence of the filler aggregates produced from the crushed concrete waste on the characteristics of binder’s paste, when part of the binder (5; 10; 15; 20; 25; 30 %) is replaced by such filler aggregate, is analysed in the research. Concrete mixtures with natural aggregates and crushed concrete waste were selected and concrete mixtures of required consistence were produced during the research. Exothermic reactions take place during the hardening of concrete mixture, at that time the heat is dissipated, which increases the temperature of the concrete sample. Thus the exothermic processes were investigated during the concrete’s mixture hardening period and the temperatures of exothermic reactions were determined.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3833

Use of Recycled Construction and Demolition Waste Aggregate for Road Course Surfacing

The need to manage construction and demolition waste (CDW) has led to environmentally-friendly actions that promote the reuse and recycling of this type of waste and other forms of waste valorization. The main priority is to foment sustainable construction work, which has the advantage of avoiding the deposit of large quantities of construction waste at landfills and greatly reducing the use of borrow material in construction projects. In this sense, the reuse of CDW materials significantly lessens the impact of construction work on the surrounding environment. The aim of this research study is to verify the technical viability of using construction waste as material for the base pavement layers of road surfaces. For this purpose, a field study was carried out, which included testing the performance of pavement composed of concrete, asphalt mix, and ceramic waste aggregate. This was done by analyzing the characteristics of the recycled material on a section of an actual road under real vehicle traffic conditions. It was observed that the load-bearing capacity of the recycled artificial CDW aggregate was satisfactory.

On the classification of mixed construction and demolition waste aggregate by porosity and its impact on the mechanical performance of concrete

The properties of recycled aggregate produced from mixed (masonry and concrete) construction and demolition (C&D) waste are highly variable, and this restricts the use of such aggregate in structural concrete production. The development of classification techniques capable of reducing this variability is instrumental for quality control purposes and the production of high quality C&D aggregate. This paper investigates how the classification of C&D mixed coarse aggregate according to porosity influences the mechanical performance of concrete. Concretes using a variety of C&D aggregate porosity classes and different water/cement ratios were produced and the mechanical properties measured. For concretes produced with constant volume fractions of water, cement, natural sand and coarse aggregate from recycled mixed C&D waste, the compressive strength and Young modulus are direct exponential functions of the aggregate porosity. Sink and float technique is a simple laboratory density separation tool that facilitates the separation of cement particles with lower porosity, a difficult task when done only by visual sorting. For this experiment, separation using a 2.2 kg/dm³ suspension produced recycled aggregate (porosity less than 17%) which yielded good performance in concrete production. Industrial gravity separators may lead to the production of high quality recycled aggregate from mixed C&D waste for structural concrete applications.