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14 Recycled Concrete Aggregates are highly porous and may therefore absorb more water . 15 than natural aggregates. Several methods allow for the measurement of water …
Owing to the high absorption capacity of recycled aggregate (RA), it is crucial to accurately measure its saturated-surface-dried water absorption …
Finally, it should be noted that recycled concrete aggregate has a water absorption coefficient seven times higher than natural aggregate, this has a negative impact through the demand for a ...
4.2.1 Review Points. The basic idea of NAC mix proportion design in China [] is that the concrete mix proportion design depends on three parts: the w/c ratio, water amount, and sand- aggregate ratio.According to the preparation of the concrete strength and the actual strength of cement, the w/c ratio is obtained by calculations using the …
Recycled aggregates should be composed mainly of concrete waste and the content of asbestos, metals, floating materials, gypsum materials, wood and plastics should be minimum; • The water absorption should comply with a maximum value (e.g., 7% (LNEC-E471, 2009)) and density should be above a minimum value (e.g., 2200 kg/m 3 (LNEC …
The high water absorption of recycled concrete aggregates (RCA) can cause a significant reduction in the flow properties of cement-based materials in relation to mixes produced with natural aggregate. In order to compensate for this adverse effect, two extreme and simple approaches based on the water absorption of RCA in pure water …
The adhered mortar on the recycled aggregates is highly porous which leads to high permeability and water absorption and has less density and resistance to fragmentation . The untreated recycled aggregates when mixed with concrete make it harsh and affect both the mechanical and durability properties of recycled aggregate …
The recycled material was recovered by crushing of concrete rubble and had high absorption values. The results showed that it is possible to achieve good resistance to carbonation and chloride penetration with up to 50% replacement of recycled coarse aggregate for 0.5 water/cement ratio.
The high absorption of fine recycled aggregates is indicated as the main difference with respect to fine natural aggregates. This property determines the extra …
However, recycled aggregate concrete (RAC), which utilizes recycled coarse aggregate (RCA) derived from waste concrete, tends to exhibit rapid slump loss [8]. This is attributed to the higher water absorption (WA) of RCA during the early stage, caused by the presence of old attached mortar on its surface [9], [10].
Due to the higher water absorption capacity of RA (see Table 1), the RA was oversaturated by 1% by which we mean that the water content of the recycled aggregate for mixing was equal to its water
The main physical properties of aggregates were measured as per the standards [31, 32], the results of which are given in Table 1, indicating that RAs have a lower density and higher water absorption than NAs. Carbonation treatment enhanced the apparent density and reduced water absorption of RAs.
Besides, the water absorptions of two RCA, between 4.3 % and 10.86 %, are much higher than that of natural aggregates. Water absorption of RCA is strongly influenced by the particle size and ...
irrespective of their size. Water absorption emerged as a key parameter for evaluating the purity and quality of these materials. The statistical analysis revealed that when the water absorption of recycled aggregates and sand falls below 5%, the compressive strength may, at most, decrease by 15% (97.5% confidence) at any replacement level.
In summary, although recycled aggregates are characterized by high water absorption, recycled aggregates in fresh concrete are possibly unable to absorb …
For conventionally produced recycled aggregates, higher substitution rates typically result in compressive strength reduction [41,42], which needs to be compensated by lowering the w/c ratio and hence impairing the workability and/or use of more cement. The effect is more pronounced for fines as their water absorption is higher .
Crushing waste concrete and using it directly as RAs has the disadvantages of high porosity and high water absorption. To achieve the reuse of resources, the researchers use microbial mineralization methods to further reinforce RAs. ... Recycled aggregates between 4.75 and 19.0 mm were taken for testing, water was taken from the laboratory …
Recycled concrete aggregate shows high porosity, low density, high water absorption and low strength than normal aggregate concrete (Casuccio et al. 2008). The recycled aggregates generally show densities slightly less than the normal aggregate. Self-cured concrete is a kind of concrete which is able to cure itself by retaining its …
The high water absorption and low strength of recycled fine aggregates limit its resource utilization in building materials. Microbial induced calcium carbonate precipitation (MICP) is an environmentally friendly method to improve recycled fine aggregates. ... The old cement mortar, attached to the recycled aggregates, leads to …
It is also observed that smaller size RCA are carbonated rapidly than larger ones due to the increase in the specific surface area. Kou et al. observed an increase in the density and decrease in the water absorption of CO 2 recycled mortar aggregates (CI-RMA) compared to untreated recycled mortar aggregates (RMAs). However, the strength of …
Recycled concrete aggregates (RCA), during their carbonation, can uptake CO2. Carbonation is described also as a treatment for RCA, to improve water absorption. The aim of this article is to ...
However, the replacement of natural aggregates (NA) with recycled fine aggregates (RFA) or recycled mixed aggregates (RMA) is often challenging. The attached mortar (AM) on the aggregate surface results in high water absorption and porosity of RCA . Also, the content of non-cement-based materials such as masonry bricks …
The quality control of aggregates for concrete involves determining their water absorption and apparent density, indicators of the material's porosity. The standard methods were developed for natural aggregates and are less appropriate for construction and demolition waste recycled aggregates (RAs), which have greater porosity and …
The high water absorption of recycled concrete aggregates (RCA) can cause a significant reduction in the flow properties of cement-based materials in relation to mixes produced with natural aggregate. ... A method to determine water absorption of recycled fine aggregate in paste for design and quality control of fresh mortar. Constr. …
In this paper, we show that the drying of recycled aggregates for temperatures above the ambient temperature (>30 °C) and at low relative humidity (<20%) removes some bounded water contained in hardened cement paste and increases …
in mix-design leading to a higher effective water/cement ratio. If absorption and water . 23. ... cracking, the water absorption of the recycled aggregate after the drying cycle would . 352.
Recycled aggregate is aggregate prepared from construction waste. With the development of a global economy and people's attention to sustainable development, recycled aggregate has shown advantages in replacing natural aggregate in the production of concrete due to its environmental friendliness, low energy consumption, …
Owing to the high absorption capacity of recycled aggregate (RA), it is crucial to accurately measure its saturated-surface-dried water absorption (W SSD), which largely affects an effective water-to-binder ratio of recycled aggregate concrete.In this study, existing measurement methods for the W SSD of RA are extensively reviewed, …
The water absorption standard values are slightly higher than hydrostatic weighing approach; the elimination of adsorbed water using the cloth is less accurate for aggregates with small size which can increase the exchange surface with water, and for aggregates with irregular shape such as recycled aggregates. The water absorption …
Water absorption of recycled aggregate is a function of size, strength of original concrete, adhered mortar content and density. In a study by BCSJ, it was ascertained that the water absorption was 3.6–8% and 8.3–12% for recycled coarse and fine aggregates, respectively. Hasaba et al. had observed similar results and it was …
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