Details

Autor(en) / Beteiligte

• Roberto da Silva, Sérgio
• de Brito, Jorge
• Andrade, Jairo José de Oliveira

Titel

Synergic effect of recycled aggregate, fly ash, and hydrated lime in concrete production

Ist Teil von

• Journal of Building Engineering, 2023-07, Vol.70, p.106370, Article 106370

Ort / Verlag

Elsevier Ltd

Erscheinungsjahr

2023

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The use of construction and demolition waste (CDW) as recycled aggregate (RA) and fly ash (FA) in the composition of cementitious materials can make the resulting concrete more sustainable. However, RA is more heterogeneous, porous, and less dense than the natural aggregate (NA), influencing the mechanical strength. On the other hand, the reaction of FA with hydration products of Portland cement is slow, delaying the strength development at an early age. An alternative to increase the strength of concrete with FA at an early age is using the hydrated lime (HL). This research intends to evaluate the efficiency of adding HL in concrete with RA and FA. In this way, this research intends to evaluate the efficiency of adding HL in concretes with RA and FA and comprises two stages. First, a w/c ratio of 0.55 and a replacement of 50% natural coarse aggregate by concrete recycled aggregate (CRA) and mixed concrete aggregate (MRA) was established, considering similar compressive strengths. In the second stage, the properties of concretes with 20% FA in partial replacement of Portland Cement (PC), adding HL at 5% and 10% (by mass) were evaluated. The results showed that concretes with CRA present performance better than concretes with MRA, and the effect of HL was significant for all properties investigated. Concretes with CRA, FA, and 10% HL improved the compressive strength by 12.47%, reduced water absorption and porosity by 9.87% and 23.82%, respectively, and increased apparent density by 8.77% compared to the mixture without HL. The SEM analysis showed the beneficial effect of HL in concretes with RA, due to the high availability of calcium hydroxide. For concretes with RCA, a reduction in the mean equivalent diameter of 62.29% was verified; for concretes with MRA, this reduction was 23.25%. A reduction of carbonation depth was observed when concretes with MRA, FA and 10% HL showed a carbonation coefficient 44.5% lower than concrete without HL after 35 days of exposure to CO2, while concretes with CRA presented a carbonation coefficient of 87.7% lower. •The effect ofCDW types used with cement replacement by fly ash (20%), and two levels of hydrated lime (5% and 10%) were investigated.•The addition of hydrated lime in concrete with fly ash and recycled aggregate anticipated the pozzolanic reaction.•Was verified change in microstructure in concretes as a function of the refinement of the pore diameter.•The carbonation depth in concretes with CDW was reduced by adding hydrated lime due to an early pozzolanic reaction.