The grain size distribution was measured according to EN 933-2 in order to simulate a similar gradation of aggregates to that of natural aggregates. The mineralogical compositions of CR and HR raw materials are given in Figures 7 and 8.
Conclusions
Impact of using recycled concrete aggregates from different sources in structural concrete. Study on the influence of adhesive mortar content on the properties of recycled concrete aggregate.
Effect of Different Types of Recycled Concrete Aggregates on Equivalent Concrete Strength and
- Introduction
- Experimental Program
- Experimental Tests 1. Mix Design
- Experimental Test Results
- Conclusions
Test results in Figure 6d indicate that the compressive strength of the ERR mix is superior to that of the control CNC mix. Test results in Figure 9d show that the ERR3 blend exhibited 90% relative tensile strength to the control blend.
Analysis and Modelling of Shrinkage and Creep of Reactive Powder Concrete
Materials and Mix Proportions 1. Raw Materials
37 RPC samples were prepared for compressive strength, modulus of elasticity, shrinkage and creep testing. To minimize the impact of mixing. process, all mixtures were made using the same planetary mixer.
Experiments
In each group, two of the same samples were stacked on top of each other. For each self-resisting load frame, the total loads of the two specimens were measured and their average was reported.
Results and Discussion
Effect of the axial stress ratio on the stress-dependent strain, specific creep and creep coefficient of RPC: (a) Stress-dependent strain; (b) Specific creep;. Effect of the steel fiber content on the stress-dependent strain, specific creep and creep coefficient of RPC: (a) Stress-dependent strain; (b) Specific creep; (c) Creep coefficient.
Residual Properties Analysis of Steel Reinforced Recycled Aggregate Concrete Components after
- Experimental Work
- Test Results 1. Surface Change
- Residual Properties Analysis
- Future Research
(c) beams;. d) The influence of temperature on various components; (e) The influence of replacement percentage on various components. According to Figure 10, the shape of the load-displacement curve for RAC exposure to elevated temperature is similar to that of plain concrete. According to the degradation trend, the stiffness degradation rate of SRRAC components under axial compression is greater than that of the flexural components after exposure to elevated temperature.
And the failure mechanism of RAC after exposure to elevated temperature is essentially similar to that of ordinary concrete. This research focuses on the influence of parameters (percentage of recycled coarse aggregate replacement and exposure to different temperatures) on the residual properties of SRRAC components.
Using Neural Networks to Determine the Significance of Aggregate Characteristics Affecting the Mechanical
Methodologies
These factors, along with mix ratio and concrete curing time, were selected as input variables for the ANN for modeling compressive strength and modulus of elasticity. In this study, the mean absolute percentage error (MAPE), root-mean-square error (RMS) and fractional absolute variance (R2) calculated using Equations (2)-(4) were used to access the accuracy of the developed ANN model. After the construction of the ANN models, the sensitivity analysis was then performed according to Figure 2.
The factors affecting the properties of RAC and used as input variables of the networks in the two cases are quite different. The details of the mixtures and the corresponding hardening properties of the prepared concrete are shown in Tables 2 and 3, respectively.
Results and Discussion
For the compressive strength, Figure 6 shows that the predicted error of the networks (ANN6-fc) using only "collaterals" as inputs was about 8.11%, and that the performance of the networks could be improved by adding each aggregated property to the inputs. As shown in Table 5, the performance of the networks (ANN8) with the combinations of two aggregated attributes added as inputs to ANN6-fc was not necessarily better than those with only one aggregated attribute added to the input. Moreover, the further combinations of these factors were no longer useful to reduce the prediction error of the networks (Table 7).
To summarize, the addition of one of the eight aggregate characteristics to ANN6-f can help achieve a better prediction of the compressive strength of RAC. As shown in Figure 5, the error in the networks (ANN6-Ec) with only mixing ratio and curing age as input was approx. 6.73%.
Analysis of Life Cycle Environmental Impact of Recycled Aggregate
- Literature Review
- Analysis of Life Cycle Impact Assessment (LCIA) 1. Method
- Comparison of Life Cycle Impact Assessment 1. Method
- Discussion
This study assessed the life cycle environmental impact of recycled aggregate using life cycle assessment (LCA). The study also compared and analyzed the environmental impact of recycled aggregate with artificial lightweight aggregate and slag. This study assessed the environmental impact of recycled aggregate using LCA as defined by ISO standards.
This shows that the LCIA of recycled aggregate (wet) was greater than that of recycled aggregate (dry), and that GWP and ADP of recycled aggregate (wet) were 30% higher than for recycled aggregate (dry). As shown in Table 5, the environmental impact of recycled aggregate was compared with that of natural aggregate and artificial lightweight aggregate, slag aggregate.
Mechanical Characteristics and Water Absorption Properties of Blast-Furnace Slag Concretes with Fly
Materials and Methods
The concrete with slag and fly ash in total replacement of sand and rubble was realized with a calibrated percentage of the aggregates. Composition of slag and fly ash (FA) concrete mix per unit volume and proportions of the components. Table 5 shows the average values of the fracture stresses obtained after 7, 28 and 90 days of curing for slag and fly ash concrete.
Table 6 shows the average values of the breaking stresses after 7, 28 and 60 days of curing for slag and microsilica concrete. This is probably due to the discontinuous composition of the aggregates used in the mix design and to the greater amount of mortar.
Conclusions
Effect of steel and carbon fiber additions on the dynamic properties of concrete containing silica fumes. Mater. Durability performance of high performance concrete made with recycled aggregates, fly ash and fused silica fumes.Cem. Mechanical characterization of high performance concrete prepared with recycled aggregates and silica fume from precast industry.J.
Combined effect of silica fume and steel fiber on the mechanical properties of high strength concrete.Constr. Compare the performance of fine fly ash and silica fumes in improving the properties of concrete containing fly ash.Constr.
Material Characterization for Sustainable Concrete Paving Blocks
Experimental Program 1. Materials
Both crumb rubber (CR) and crushed glass (CG) were hardly used as aggregates in the concrete paving blocks. Similar to RCCA, crushed glass was also used to replace the coarse aggregates in the blocks. The replacement levels of RCFA in the experiment were determined as 10%, 20% and 30%, labeled as RCFB-X.
Before the casting phase, all materials used in the experiments were completely dried in the oven for 24 hours. For one batch of the concrete mix, the total mass was 60 kg for casting 20 concrete paving blocks.
Results and Discussion 1. Aggregates’ Properties
Figure 9 shows the relationships between the replacement levels and the tensile splitting strength of concrete pavers for different types of waste materials. The slip resistance of blocks mixed with RCFA also had a significant reduction when the replacement level was 10%. With replacement levels ranging from 10% to 40%, all concrete pavers mixed with crushed glass had higher strength and lower water absorption than the blocks mixed with natural aggregates.
When the replacement rate of crushed glass is 20%, concrete pavers have the highest compressive strength and the lowest water absorption. The tensile splitting strength of concrete blocks mixed with crushed glass reached the maximum value when the replacement level was 40%.
Crushing Performance of Ultra-Lightweight Foam Concrete with Fine Particle Inclusions
Mixture Design and Sample Preparation
Detailed information on mix design is given in Table 1, where the mix naming convention is "sand ratio_sand size". As part of the water was used for foaming, the water available for mixing the paste varied between samples. As such, a superplasticizer was used to maintain the same fluidity of the fresh paste for further mixing.
Therefore, much of the cement was replaced with fly ash to obtain a more fluid paste mixture. Since the density of the river sand is higher than that of the paste, the effective bulk density of the pure foam paste decreases as the sand ratio increases (see Table 1).
Testing methods
Results and discussion 1. Elastic Modulus of the Samples
There is a noticeable rise in the curve slopes of the controlled sample and that of a 0.15 sand ratio. To study the influence of the inclusion size, the samples of Samples of 0.5 sand ratio, together with the control sample were further scanned using micro-CT. This study investigated the influence of sand size and sand content on the mechanical properties of a group of 0.55 g/cm3 foamed concrete mixtures, for which higher sand ratio corresponds to less cement use and lower density of the foamed paste.
The results of the modulus of elasticity test from the vibration frequency test and the load response from the penetration test indicate a strong influence of the material modulus on the crushing of the foam-sand composite. Because of this direct effect of sand size on foam stability, particular attention must be paid to particle size and foam void size during mix design when using particle inclusions in foam concrete.
Effect of Nylon Fiber Addition on the Performance of Recycled Aggregate Concrete
Experimental Section 1. Materials
In addition, a polycarboxylate (SP)-based superplasticizer was used to improve the initially low workability of the fresh concrete. Average values of split compressive and tensile strengths of at least three samples for each concrete mix were obtained and the standard deviation of the test results was calculated. A rapid chloride ion permeability test was used to evaluate the permeability of the concrete samples.
The current flowing through the concrete disk and the temperature of the solution in the chambers were recorded at an interval of 30 min. The highest level of total load passed represents the highest permeability of the concrete, as shown in Table 4.
Results and Discussion 1. Compressive Stregnth
As expected, the splitting tensile strength values of concrete were significantly dependent on the added NF content. Distributed values of tensile strength of concrete mixes with different NF contents (standard deviation in parentheses). In the case of sample CAC1 (Figure 9), it was found in the image that, in addition to a small amount of ettringite (AFt) and monosulfate (AFm), crystals of calcium hydroxide (CH) and C-S-H gel were present.
The strengthening of the ITZ bond results in the microstructural integrity of the cement matrix. This may be due to the increased density of materials and the bridging effect of NF.
