Use of a reference limestone fine aggregate to study the fresh and hard behavior of mortar made with recycled fine aggregate

Abstract

Recycled fine concrete aggregates (RFA) are not enough used in the construction sector, mainly because of their high water absorption capacity. These fine particles are composed of crushed natural aggregate and adherent hardened cement paste. The main goal of this research is to compare the behaviors of mortars made either with RFA or with a model limestone fine natural aggregate (LFA). The LFA is prepared in order to obtain physical properties as close as possible to those of the RFA. A specific characterisation is carried out to compare the density, water absorption, morphology of grains, size distribution and packing density of both aggregates. Mortars are then manufactured with same composition and same volume of LFA and RFA. Different states of moisture of the RFA are studied. The fresh behaviour of the mortar made with saturated RFA is very close to that of the mortar made with LFA which confirms that the latter is a good reference compared to the RFA. Comparison of fresh behaviours of mortars made with RFA of different state of moisture to that of mortar made with saturated sand allows then to determine the water absorbed in the different moisture conditions. Afterwards, a mechanical study is realised, taking into consideration the exact quantity of absorbed water of the RFA in dry or saturated conditions. Knowing the exact effective water value allows us to study both the strength of mortar made with RFA, the strength of the matrix and the adherence between the fine aggregate and the paste. Response to Reviewers:The authors declare that they have no conflict of interest.

Internal sulfate attack in mortars containing contaminated fine recycled concrete aggregates

“…4 is a typical image found with recycled materials: the recycled aggregate is a cluster of natural aggregates in the original cement paste. The new cement paste, surrounding the recycled aggregates, had a notably higher air content, which has been observed before by Bouarroudj et al [32] for the same material. This air content can be explained by the surface roughness of the recycled aggregates [33], which captures more air into the mixture than a round (natural) aggregate.…”

Use of grinded hardened cement pastes as mineral addition for mortars

“…The coarse fraction of RCA is easier to valorize than the finer one in the construction sector. Up to now, research on RCA has been more focused on using RCA as aggregates in concrete production [6][7][8] than for manufacturing cement [9,10] or as a mineral addition in concrete production [11,12].…”

Statistical Approach for the Design of Structural Self-Compacting Concrete with Fine Recycled Concrete Aggregate

“…Table 16 shows the characteristic strength according to the normal distribution and the best-fit distribution (Weibull or gamma) for each mixture. In addition, this table also shows the normalized value according to the Spanish Instruction of Structural Concrete EHE-08 [29], calculated by approximating the value obtained to the standard series (20,25,30,35,40,45,50,55,60,70,80,90, and 100 MPa). Figure 10 shows the calculation of the 5% percentile for each mixture in the best-fit distribution (Weibull or gamma).…”

“…Limestone filler-with a size below 0.063 mm and high purity (CaCO3 content above 98%), to provide the finest particle size fraction [45].…”