Recycled concrete aggregates (RCAs) have been demonstrated as an alternative source to exhaustible natural aggregates. In this paper, we focus on the enhancement treatments for coarse and fine RCAs and the effect of these treatments on the durability of recycled concrete (RC) made from treated RCAs by the weakening and strengthening of the cement paste adhered to their surface. We conducted comparative analyses on the improvement of durability and mechanical properties. The results showed that the reduction of water absorption in RCAs increases the compressive strength of RC and that there is a strong linear trend of improvement in the carbonation depth, chloride ion penetration, and compressive strength of RC. For fine and coarse RCAs, the treatment mechanism and particle size are determinants in efficiently improving RC durability.

This study evaluates a binary mixture of fly ash and lime as a stabilizer for natural soils. A comparative analysis was performed on the effect on the bearing capacity of silty, sandy and clayey soils after the addition of lime and ordinary Portland cement as conventional stabilizers, and a non-conventional product of a binary mixture of fly ash and Ca(OH)₂ called FLM. Laboratory tests were carried out to evaluate the effect of additions on the bearing capacity of stabilized soils by unconfined compressive strength (UCS). In addition, a mineralogical analysis to validate the presence of cementitious phases due to chemical reactions with FLM was performed. The highest UCS values were found in the soils that required the highest water demand for compaction. Thus, the silty soil added with FLM reached 10 MPa after 28 days of curing, which was in agreement with the analysis of the FLM pastes, where soil moistures higher than 20% showed the best mechanical characteristics. Furthermore, a 120 m long track was built with stabilized soil to evaluate its structural behavior for 10 months. An increase of 200% in the resilient modulus of the FLM-stabilized soils was identified, and a decrease of up to 50% in the roughness index of the FLM, lime (L) and Ordinary Portland Cement (OPC)-stabilized soils compared to the soil without addition, resulting in more functional surfaces.

This research aims to improve the quality of recycled concrete fine aggregates (RFA) by using diammonium hydrogen phosphate (DAP). We aimed to understand the effect of DAP treatment on durability performance due to the carbonation action of mortars with the partial and total substitution of treated RFA. The results showed a maximum reduction in the RFA water absorption of up to 33% using a minimum DAP concentration due to a pore refinement as a consequence of the formation of calcium phosphates such as hydroxyapatite (HAP). The carbonation phenomenon did not have a significant effect on the durability of mortars with DAP-treated RFA, as we did not find a decrease in the compressive strength; the carbonation depth of the mortars with 100% treated RFA decreased up to 90% and 63% for a w/c of 0.45 and 0.50, in comparison with mortars with 0% treated RFA. An inversely proportional relationship was found between the accelerate carbonation and the compressive strength, showing that higher percentages of treated RFAs in the mortar promoted an increase in compressive strength and a decrease in the carbonation rate, which is behavior associated with a lower permeability of the cement matrix as one of the consequences of the microstructural densification by DAP treatment.

One aspect that affects the strength of Portland cement mortars is the correction of moisture in the mix. Thus, standard techniques are usually used to obtain the absorption value in fine aggregates; one of them is the standard ASTM C128. However, the ASTM C128 presents variability associated with the identification of the saturated surface dry state in the fine aggregates. This research compares the water absorption of four types of Colombian aggregates obtained using the ASTM C128 and an innovative instrumental and analytical technique with the thermogravimetric balance of halogen light (TBHL), coupled with a software that reads the retained water data in real time. The strength of mortars designed on the basis of moisture correction is also evaluated. The absorption results show that TBHL presents lesser dispersion results (not exceeding 10%) than the standard method ASTM C128, indicating greater precision and less uncertainty. Additionally, resources are optimized through TBHL implementation, requiring 25% less time, 86% less energy consumption, and 98% less fine aggregate for a test. Furthermore, the strength of the mortars varies depending on the method used to determine the absorption, as well as the morphology of the aggregates. The accuracy of TBHL allows better correction of the water–cement ratio in the mortars; thus, leading to higher performance.