Effect of curing conditions on cement based self-compacting mortar produced with mortar waste aggregate.

Concrete and mortar wastes, which have a large volume and economic value among construction demolition wastes, are the most targeted demolition waste group to be recycled. An important area where construction demolition waste can be utilized is self-compacting mortar (SCM) systems. SCMs are innovative and economical systems designed to minimize the labor requirements that are difficult to meet in the production process. In this study, mortar waste aggregate (MWA) obtained by mechanical crushing and grinding was used in SCM elements by substituting different ratios (5-10-20-30-40 %) by mass to aggregate. In this way, it was aimed to evaluate both the sustainability of MWAs and the usability of MWAs in SCMs, which are considered as a new production technology. The fresh and hardened mortar tests performed in the study are presented comparatively. The physical (dry unit volume weight, porosity), durability (capillary water absorption) and mechanical properties (flexural tensile, compressive strength) of the hardened SCM elements are based on the determinations made at 3, 7 and 28 test days and according to different curing conditions (water curing, air curing and heat curing). In addition, X-ray Diffractometer (XRD) analysis was performed on specimens obtained from 0 %, 10 %, 20 % and 40 % MWA substituted specimens after heat curing (after 7 days water curing) and 28 days water curing. In the light of the data obtained, it is reported that SCM production with 10 % MWA substitution is feasible in terms of sustainability and engineering properties evaluated in this study.

A study on the bond strength and durability characteristics of high-performance concrete modified with toughened glass waste aggregates.

Amidst rising natural aggregate consumption, recycling dumped waste for structural concrete effectively addresses resource scarcity and environmental contamination. Nevertheless, the adoption of toughened glass waste aggregate (TGWA) in construction remains relatively limited. This study explores the potential use of toughened glass waste (TGW) as a substitute for natural coarse aggregate (NCA) in high-performance concrete (HPC). This paper assesses the bond strength of deformed bars embedded in toughened glass waste high-performance concrete (TGW-HPC), considering different steel reinforcement diameters (8 mm and 12 mm) and various levels of TGW replacement (ranging from 0 % to 100 %). Various durability properties, including water absorption, water permeability, chloride ion penetration, and acid attack were examined. The study also investigated the microstructural characteristics of acid attacked specimens using techniques such as XRD, FTIR, and FESEM. Several important parameters, such as chloride diffusivity (D), hydraulic diffusivity (D (θ)), and permeability coefficients (K), were derived from the experimental data. The study found TGW50-HPC resulted in the highest bond strength, about 13.1 % more than the control mix. However, TGW100-HPC bond strength decreased by 17.51 % compared to the control mix. Notably, TGW100-HPC exhibited superior durability properties and showed the lowest coefficient of permeability, indicating reduced chloride ion, and water molecule transport through the interconnected pore structure. At 90 days, the TGW100-HPC mixture exhibited a strength reduction of 42.29 %, which closely resembled the 41.20 % reduction observed at 56 days. The formation of thenardite and basanite mitigate damage to the interfacial transition zone (ITZ) led to fewer micro-cracks and reduced acid ingress through the matrix. Incorporating TGWA in engineering projects can lead to cost savings through reduced raw material expenses and disposal fees, resulting in significant economic benefits and social well-being.

Sustainable development of concrete through treated and untreated plastic waste aggregates.

This study focused on sustainable and novel development of concrete through treated and untreated plastic waste aggregates. In this study, the surface of Elec-waste coarse aggregates was treated with sulfuric acid, marble dust coating, silica fume coating, and alkaline bleach. Elec-waste aggregates were used in concrete by replacing natural coarse aggregates in amounts of 10%, 20%, and 30%. The 10%, 20%, and 30% Elec-waste replacement ratios resulted in the compressive strength reduction of 8.97%, 27.99%, and 42.01%, respectively. The same percentage of Elec-waste aggregates reduced the splitting tensile strength by 21.77%, 35.89%, and 47.89%, respectively. However, the slump was observed to increase by 41.4%, 52.1%, and 68.8%, respectively. All the considered treatments enhanced the performance of Elec-waste aggregate concrete (E-WAC). Overall, the best improvement in the performance of E-WAC was imparted by silica fume coating, irrespective of the quantity of Elec-waste aggregates. The present study proposed an expression to estimate the reduction of the compressive strength of E-WAC. It was demonstrated that the equation by JCI-08 predicted splitting tensile strength of E-WAC close to experimental results.

Potential of Reusing 3D Printed Concrete (3DPC) Fine Recycled Aggregates as a Strategy towards Decreasing Cement Content in 3DPC.

This paper explores the new potential strategy of using fine recycled aggregates (fRA) derived from waste 3D printed concrete (3DPC) as a substitute for cement in additive manufacturing. This study hypothesizes that fRA can optimize mixture design, reduce cement content, and contribute to sustainable construction practices. Experimental programs were conducted to evaluate the fresh and hardened properties, printability window, and buildability of 3DPC mixes containing fRA. Mixes with replacement rates of cement with fRA by 10 vol%, 20 vol%, 30 vol%, 40 vol%, and 50 vol% were produced. A comprehensive experimental protocol consisting of rheological studies (static and dynamic yield stress), dynamic elastic modulus determination (first 24 h of hydration), flexural and compressive strengths (2 d and 28 d), and an open porosity test was performed. The obtained results were verified by printing tests. In addition, an economic and environmental life cycle assessment (LCA) of the mixes was performed. The results indicate that up to 50 vol% cement replacement with fRA is feasible, albeit with some technical drawbacks. While fRA incorporation enhances sustainability by reducing CO2 emissions and material costs, it adversely affects the printability window, green strength, setting time, and mechanical properties, particularly in the initial curing stages. Therefore, with higher replacement rates (above 20 vol%), potential optimization efforts are needed to mitigate drawbacks such as reduced green strength and buildability. Notably, replacement rates of up to 20 vol% can be successfully used without compromising the overall material properties or altering the mixture design. The LCA analysis shows that reducing the cement content and increasing the fRA addition results in a significant reduction in mix cost (up to 24%) and a substantial decrease in equivalent CO2 emissions (up to 48%). In conclusion, this study underscores the potential of fRA as a sustainable alternative to cement in 3D printed concrete.

Cracking Behavior and Deflections in Recycled-Aggregate Beams Reinforced with Waste Fibers Subjected to Long-Term Constant Loading.

This report presents the results of long-term tests on concrete beams reinforced with steel cord. In this study, natural aggregate was wholly replaced with waste sand or with wastes from the production of ceramic products and ceramic hollow bricks. The amounts of individual fractions used were determined in accordance with guidelines for reference concrete. A total of eight mixtures were tested; these differed in terms of the type of waste aggregate used. Elements with various fiber-reinforcement ratios were made for each mixture. Steel fibers and waste fibers were used in amounts of 0.0%, 0.5%, and 1.0%. Compressive strength and modulus of elasticity were determined experimentally for each mixture. The main test was a four-point beam bending test. Beams with dimensions of 100 mm × 200 mm × 2900 mm were tested on a stand, which was specially prepared so that three beams could be tested simultaneously. Fiber-reinforcement ratios were 0.5% and 1.0%. Long-term studies were conducted for 1000 days. During the testing period, beam deflections and cracks were measured. The obtained results were compared with values calculated using several methods, considering the influence of dispersed reinforcement. The results enabled the best methods for calculating individual values for mixtures with different types of waste materials to be determined.

A study on the applicability of scoria gravel an alternative base course material through blending with marble waste aggregate.

This study aims to evaluate the applicability of Scoria gravel as an alternative base course material in flexible pavements through blending with marble waste aggregate (MWA) by modifying the physical and mechanical engineering properties of scoria. Non-Probabilistic sampling techniques and experimental methods were used. To achieve the objectives of the study, the laboratory tests were passed in three steps. First, the Engineering properties of materials were independently tested; the result proves the marginality of scoria gravel. Second, scoria gravel was mechanically stabilized by 20% percentages by weight increments of MWA. The obtained engineering properties test results at 20:80 Scoria to MWA mix ratios are 2.56%, 21.38%, 18.59%, 19.27%, 17.45%, 13.77%, Non-Plastic, 1.21%, and 73.4%, for Specific Gravity, Aggregate Crushing Value, Aggregate Impact Value, Loss Angeles Abrasion, Flakiness Index, Elongation Index, Atterberg's limit, Water Absorption, and California Bearing Ratio (CBR) respectively. These test results fulfilled the ERA standard specification for GB2 and GB3 base course materials. However, the CBR test results showed a failure to meet the standard spécification. Thus, 20:80 Scoria to MWA percentage by weight ratio was selected as a control mixture. So, Crushed Stone Aggregate was added at 5% percentage by weight to improve the CBR of scoria gravel. Therefore, the CBR value of 82.13% attained the ERA standard Specification limit for base course materials at 15:60:25 percentages by weight ratio of scoria gravel, MWA, and CSA respectively. Finally, Based on this study it was recommended to use scoria gravel as an alternative base course construction material, when it was found abundantly near construction vicinity.

Relationship of Surface and Bulk Resistivity in the Case of Mechanically Damaged Fibre Reinforced Red Ceramic Waste Aggregate Concrete.

Electrical resistivity is an important physical property of concrete, directly related to the chloride-induced corrosion process. This paper analyses the surface resistivity (SR) and bulk resistivity (BR) of structural lightweight waste aggregate concrete (SLWAC). The studied concrete mixture contained waste material-red ceramics fine aggregate and artificial expanded clay coarse aggregate. Red ceramic is a frequent waste material remaining after the demolition of buildings or unsatisfactory building material production and is among the least used construction waste. Therefore, its use is desirable in terms of sustainability; in some cases, it can reliably replace the conventional aggregate in a concrete mixture. The relationship between SR and BR was determined in the case of standard specimens and mechanically damaged specimens (to 50% and 100% of ultimate strength capacity-USC). Two different instruments were utilised for the investigation-a 4-point Wenner probe meter and an RCON tester. The results of standard specimens support the theoretically derived correction ratio, but in the case of mechanically damaged specimens, the ratio is more scattered, which is related to the mechanical damage and the amount of fibre.

Evaluation of Stone Mastic Asphalt Containing Ceramic Waste Aggregate for Cooling Asphalt Pavement.

Construction and demolition waste material is of great potential for use in pavement engineering. This paper aims to investigate the feasibility of ceramic waste aggregate (CA) used in cooling asphalt pavement through a series of test methods and simulation techniques. Stone mastic asphalt (SMA) containing 10%, 20%, 30%, 40%, and 50% coarse ceramic waste aggregate (CASMAs) was first designed using the Marshall method. Afterward, the road performance and thermal insulation performance of the five different CASMAs were assessed by a comprehensive lab test, including a wheel rutting test, moisture susceptibility test, bending beam test, fatigue beam test, and indoor thermal insulation test. Finally, a 2D finite-element (FE) model was developed to investigate the transient thermal field and rutting deformation response of the cooling asphalt pavement with CASMAs. Results show that CASMAs experienced degradation of rutting resistance, moisture susceptibility, and anti-cracking performance while still meeting technical requirements with CA content of up to 40%. On the other hand, CASMAs can cool the pavement's temperature by 11.5 °C at the bottom of asphalt layers. The permanent rutting deformation of cooling asphalt pavement was 45.36% smaller than that of conventional asphalt pavement without CASMAs. Based on the test results and numerical simulation results, the optimum content of ceramic waste aggregate in stone mastic asphalt was recommended as 40%.

Analytical framework for value added utilization of glass waste in concrete: Mechanical and environmental performance.

This work was designed to incorporate glass waste as partial replacement of coarse aggregate in concrete through optimization of its amount by assessment of mechanical and environmental performances. Fresh and hardened properties of glass waste concrete were evaluated and compared with the conventional concrete. Moreover, compressive strength was evaluated experimentally as well as analytically at different ages. While, environmental performance was evaluated with an assessment of CO2 footprint and volume utilization of raw materials for both types of concrete; conventional and glass waste concrete. Consequently, a sustainable concrete was selected that possesses high workability and mechanical performance, minimum CO2 footprint and least utilization of conventional natural raw materials. For optimization, corresponding values of designed parameters were translated into a framework for glass waste management by application of analytical hierarchy process (AHP) and technique for order preference by similarity to ideal solution (TOPSIS). Similar prioritization for all types of mixtures was achieved through proposed framework by applying such multi criteria decision making techniques. Proposed framework may further be used for adjusting the priority weights for each criterion according to the requirement as well as for extended evaluation of additional criteria.

Environmental performance and mechanical analysis of concrete containing recycled asphalt pavement (RAP) and waste precast concrete as aggregate.

The overall objective of this research project was to investigate the feasibility of incorporating 100% recycled aggregates, either waste precast concrete or waste asphalt planning, as replacements for virgin aggregates in structural concrete and to determine the mechanical and environmental performance of concrete containing these aggregates. Four different types of concrete mixtures were designed with the same total water cement ratio (w/c=0.74) either by using natural aggregate as reference or by totally replacing the natural aggregate with recycled material. Ground granulated blast furnace slag (GGBS) was used as a mineral addition (35%) in all mixtures. The test results showed that it is possible to obtain satisfactory performance for strength characteristics of concrete containing recycled aggregates, if these aggregates are sourced from old precast concrete. However, from the perspective of the mechanical properties, the test results indicated that concrete with RAP aggregate cannot be used for structural applications. In terms of leaching, the results also showed that the environmental behaviour of the recycled aggregate concrete is similar to that of the natural aggregate concrete.