Sustainable deployment of crushed concrete aggregates strengthened with cement and sand

Purpose: Paper assessed the feasibility of crushed concrete aggregates (CCA), a subsidiary of construction and demolition (C&D) waste, blended with cement and sand to form a composite for civil engineering field applications. Design/methodology/approach: The compaction and strength characteristics of CCA were observed by conducting Proctor compaction and California Bearing Ratio (CBR) tests. Different proportions of CCA, sand and cement were used. Moreover, the effect of curing period (0, 4, 7, 14 and 28 days) was also studied. In addition, regression analyses were performed to develop empirical expressions to predict the compaction and strength characteristics of the CCA composite. Findings: Increasing the CCA content up to 50% increases the maximum dry unit weight (MDUW) and decreases the optimum moisture content (OMC). However, on further increasing its content the MDUW decreases and OMC increases. Percent increase in the CBR value can go up to 412% if the CCA content is increased up to 50%. However, the percent reduction in CBR of about 20% can take place if 100% CCA content is used. Moreover, multiple regression shows that the experimental results are in good agreement with the predicted values. Research limitations/implications: The results obtained are purely dependent on the type of material. However, they are in favour of the used material as a probable option for road sub-base layer, and also for reducing burden on available natural resources. Therefore, it is recommended to conduct some initial tests to confirm the feasibility of the material. Practical implications: The proposed study will guide the design Engineers to choose CCA as one of the potential materials for road construction. Originality/value: It was observed that there is a need to maximize the utilization of C&D waste without making any compromise with its mechanical properties. So keeping that in view, the present study was conducted.

Static Load Test on Trapezoidal Filling Structure of Crushed Concrete Particles Reinforced with Waste Tire Slices

In this paper, a series of model tests about the trapezoidal filling structures filled with tire reinforced concrete particles has been conducted to study their stability and the ultimate bearing capacity. The effects of the reinforcing tire slices on the global stability and ultimate bearing capacity of the model were investigated, the results show that the tire slices reinforcement can reduce the total settlement of the trapezoidal filling structure, and the ultimate bearing capacity of the reinforced trapezoidal filling structure with tire slices is obviously improved. Among them, the settlements of crushed concrete particles reinforced with bottom layer, top layer, and two layers (both bottom layer and top layer) waste tire slices are 11.5%, 37.7%, and 46.2% less than that of unreinforcement, respectively. Compared with unreinforcement, when the top layer of the model is reinforced with tire slices, the Earth pressure values at the top layer and the bottom layer are reduced by 21.1% and 22.7%, respectively; the Earth pressure values at the top layer and the bottom layer are reduced 6.3% and 14.3%, respectively, when the bottom layer of the model is reinforced with tire slices, and the Earth pressure values at the top layer and the bottom layer are reduced 23.4% and 32.9%, respectively, when the two layers of the model are reinforced with tire slices. The sliding surface of the pure concrete particles filled trapezoidal structure is continuous and runs through the whole trapezoidal filling structure slope; the sliding zone of reinforced trapezoidal filling structure with tire slices decreases with the laying of tire slices.

Development of Concrete Incorporating Recycled Aggregates, Hydrated Lime and Natural Volcanic Pozzolan

Recycling of construction and demolition waste is a central point of discussion throughout the world. The application of recycled concrete as partial replacement of mineral aggregates in concrete mixes is one of the alternatives in the reduction of pollution and savings in carbon emissions. The combined influence of the recycled crushed concrete, lime, and natural pozzolana on the mechanical and sustainable properties of concrete materials is firstly proposed in this study. In this research, unconventional construction materials are employed to produce concrete: the recycled crushed concrete is used as coarse aggregate, while lime and natural pozzolana are used as a partial replacement for cement. Substitutions of 10%, 20%, 50% of gravel are made with recycled aggregates, and 2%, 5%, 10% of cement with lime and natural pozzolan. Tests on the fresh and hardened properties, destructive (compressive strength) and non-destructive tests (sclerometer rebound and ultrasound) of mixtures are carried out. It is shown that the use of recycled materials can provide an increase in compressive strength of up to 34% with respect to conventional concrete. Life cycle cost and sustainability assessments indicate that concrete materials incorporating recycled aggregate possess good economic and environmental impacts.

Development of structural-heat-insulating lightweight concrete composition using production of aerated concrete waste as a porous aggregate

Annually enterprises in the field of manufacturing of products from aerated concrete generate from 5000 to 10000 m3 of solid production waste. One of the perspective and under-investigated direction is the practical application of solid waste using a porous aggregate in structural-heat-insulating lightweight concrete in the production of construction materials. The aim of this study was to evaluate the possibility of using crushed aerated concrete as a large aggregate in lightweight concrete for structural and thermal insulation purposes and to establish optimal conditions for obtaining products with the best characteristics. There were defined the qualitative indicators of crushed aerated concrete, analyzed factors influencing on the preservation of the properties of concrete in time, selected the composition of concrete aggregates from crushed concrete, studied the structure and properties of the obtained samples in the research. It has been found that to obtain effective constructive insulating lightweight concrete using waste production of aerated concrete as an aggregate is possible due to the fractionated pre-treatment of the aggregate with water dispersion of deep-penetration acrylic copolymers, insertion excess sealing water to concrete mixture, including optimization of the rheological properties of the concrete mix due to insertion of polycarboxylate hyperplasticizer.