scholarly journals Testing recycled concrete aggregate suffering different levels of alkali-silica reaction for use in new structures

2021 ◽  
Author(s):  
Matthew Piersanti
Keyword(s):  
Service Life ◽  
Recycled Concrete ◽  
Alkali Silica Reaction ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate ◽  
Construction Work ◽  
Supplementary Cementing Materials ◽  
New Construction ◽  
Land Space ◽  
Different Levels

As concrete reaches the end of its service life, it is demolished and placed in landfills, which is not sustainable as this consumes land space. Many demolished structures are crushed into recycled concrete aggregate (RCA) and used in new construction work to reduce concrete waste. To be used in concrete, the effects of RCA on the new structures should be carefully examined. The RCA studied in this research is an alkali-silica reactive gravel from Sudbury, Ontario. The RCA was obtained from different elements of a 20-year old bridge that suffered different levels of deterioration. It was determined that the level of deterioration that affected the previous structure does not significantly affect the expansion that will occur in the new structure. It was also determined that the expansion could be mitigated through the use of supplementary cementing materials although higher levels are required compared those required for the virgin aggregate.

scholarly journals Testing recycled concrete aggregate suffering different levels of alkali-silica reaction for use in new structures

2021 ◽  
Author(s):  
Matthew Piersanti
Keyword(s):  
Service Life ◽  
Recycled Concrete ◽  
Alkali Silica Reaction ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate ◽  
Construction Work ◽  
Supplementary Cementing Materials ◽  
New Construction ◽  
Land Space ◽  
Different Levels

As concrete reaches the end of its service life, it is demolished and placed in landfills, which is not sustainable as this consumes land space. Many demolished structures are crushed into recycled concrete aggregate (RCA) and used in new construction work to reduce concrete waste. To be used in concrete, the effects of RCA on the new structures should be carefully examined. The RCA studied in this research is an alkali-silica reactive gravel from Sudbury, Ontario. The RCA was obtained from different elements of a 20-year old bridge that suffered different levels of deterioration. It was determined that the level of deterioration that affected the previous structure does not significantly affect the expansion that will occur in the new structure. It was also determined that the expansion could be mitigated through the use of supplementary cementing materials although higher levels are required compared those required for the virgin aggregate.

scholarly journals The use of lithium salts and supplementary cementing materials to control reactivity of recycled concrete aggregate

2021 ◽  
Author(s):  
Waleed Mikhaiel
Keyword(s):  
Preventive Measure ◽  
Calcium Content ◽  
Recycled Concrete ◽  
Alkali Silica Reaction ◽  
Alkaline Solutions ◽  
Concrete Aggregate ◽  
Second Phase ◽  
Lithium Nitrate ◽  
Recycled Concrete Aggregate ◽  
Supplementary Cementing Materials

This thesis covered the second phase of a study that focused on the reactivity of recycled concrete aggregate (RCA) produced from concrete affected by alkali-silica reaction (ASR). The first phase investigated the reactivity of ASR-affected RCA and the use of Supplementary Cementing Materials (SCM) as a preventive measure. The second phase was carried out to study the efficacy of lithium nitrate, when used individually and in combination with SCM, in suppressing the reactivity of RCA. The use of different dosages of lithium nitrate combined with SCMs reduced expansion due to ASR. However, the expansion results showed that increasing the dosage of lithium beyond a certain level does not help in suppressing the expansion. The high reacitivity of the tested RCA was attiributable to its relatively high alkalis and calcium hydroxide contents that fuel further ASR. The alkalis consumed or contributed from RCA were evaluated through leaching the aggregate particles in distilled water and alkaline solutions at different molarities with and without lithium nitrate. Alkalis consumption was found to decrease when lithium was presented in the leaching solutions. Examining RCA samples under scanning electron microscope (SEM) showed that the crushing process of the RCA exposes fresh surfaces of the reactive virgin aggregate and creates cracks within the particles that provide an easy path of alkalis to reactive sites within the RCA. Examination of the composition of ASR gel showed that exposing the RCA to lithium solution decreased the calcium content and Ca/Si of the gel. This could add to the suggested mechanisms by which the lithium mitigates ASR.

scholarly journals The use of lithium salts and supplementary cementing materials to control reactivity of recycled concrete aggregate

2021 ◽  
Author(s):  
Waleed Mikhaiel
Keyword(s):  
Preventive Measure ◽  
Calcium Content ◽  
Recycled Concrete ◽  
Alkali Silica Reaction ◽  
Alkaline Solutions ◽  
Concrete Aggregate ◽  
Second Phase ◽  
Lithium Nitrate ◽  
Recycled Concrete Aggregate ◽  
Supplementary Cementing Materials

This thesis covered the second phase of a study that focused on the reactivity of recycled concrete aggregate (RCA) produced from concrete affected by alkali-silica reaction (ASR). The first phase investigated the reactivity of ASR-affected RCA and the use of Supplementary Cementing Materials (SCM) as a preventive measure. The second phase was carried out to study the efficacy of lithium nitrate, when used individually and in combination with SCM, in suppressing the reactivity of RCA. The use of different dosages of lithium nitrate combined with SCMs reduced expansion due to ASR. However, the expansion results showed that increasing the dosage of lithium beyond a certain level does not help in suppressing the expansion. The high reacitivity of the tested RCA was attiributable to its relatively high alkalis and calcium hydroxide contents that fuel further ASR. The alkalis consumed or contributed from RCA were evaluated through leaching the aggregate particles in distilled water and alkaline solutions at different molarities with and without lithium nitrate. Alkalis consumption was found to decrease when lithium was presented in the leaching solutions. Examining RCA samples under scanning electron microscope (SEM) showed that the crushing process of the RCA exposes fresh surfaces of the reactive virgin aggregate and creates cracks within the particles that provide an easy path of alkalis to reactive sites within the RCA. Examination of the composition of ASR gel showed that exposing the RCA to lithium solution decreased the calcium content and Ca/Si of the gel. This could add to the suggested mechanisms by which the lithium mitigates ASR.

Microscopic assessment of recycled concrete aggregate (RCA) mixtures affected by alkali-silica reaction (ASR)

2021 ◽  
Vol 269 ◽  
pp. 121250
Author(s):  
Cassandra Trottier ◽  
Andisheh Zahedi ◽  
Rouzbeh Ziapour ◽  
Leandro Sanchez ◽  
Francisco Locati
Keyword(s):  
Recycled Concrete ◽  
Alkali Silica Reaction ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate

STRENGTH AND DURABILITY OF SELF CONSOLIDATING CONCRETE CONTAINING RECYCLED MATERIALS

2019 ◽  
Vol 7 (SI-TeMIC18) ◽  
Author(s):  
Mohd Afiq Mohd Fauzi Mohd Fauzi ◽  
Ahmad Ruslan Mohd Ridzuan ◽  
Mohd Fadzil Arshad ◽  
Nurliza Jasmi ◽  
Mohd Shafee Harun ◽  
...  
Keyword(s):  
Strength Characteristic ◽  
Strength Properties ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate ◽  
Chloride Permeability ◽  
Conventional Concrete ◽  
Self Consolidating Concrete ◽  
New Construction ◽  
Strength And Durability

Self-Consolidating Concrete (SCC) is developing class of concrete materials that offers great potential to improved ease of positioning and cost through reduced time and labor. Generally, amount of Construction and Demolition Wastes (C&DW) are increased daily. Therefore, it is beneficial to final usage of coarse recycled concrete aggregate that produced from crushed concrete waste as a new construction solution. Researchers have found that waste materials have unique properties that could help in improving the quality of self-consolidating concrete produced. Therefore, reuse of RCA generated as the supplemental material for the replacement of aggregate are significant in reducing the environmental impact. This research was focused on the strength characteristic and the chloride permeability level of SCC containing RCA. The influence of RCA content in the range from 0% to 100% of Natural Aggregate (NA) to the strength characteristic and the chloride permeability level of SCC was identified and compared with SCC containing normal mixes. In this research, three (3) series of concrete specimens were cast with different water cement ratios (0.53, 0.49 and 0.45). The concrete specimens were subjected to strength at the age of 3, 7, 14, 21, 28, 56 and 90 days and durability at the age of 28, 56 and 90 days. The result shown that the compressive strength and chloride permeability of SCC containing 100% RCA replacement give better performance than the 0% RCA replacement. Based on the finding, SCC containing 100% RCA replacement can be categorized similar to conventional concrete hence it can be utilized for construction purposes. RCA can also acts as an alternative replacement in concrete for replacing the NA. Keywords: Strength Properties; Rapid Chloride Permeability Test; Self Consolidating Concrete; Recycled Concrete Aggregate

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