Durability of Mortar Incorporating Ferronickel Slag Aggregate and Supplementary Cementitious Materials Subjected to Wet–Dry Cycles

This paper presents the strength and durability of cement mortars using 0–100% ferronickel slag (FNS) as replacement of natural sand and 30% fly ash or ground granulated blast furnace slag (GGBFS) as cement replacement. The maximum mortar compressive strength was achieved with 50% sand replacement by FNS. Durability was evaluated by the changes in compressive strength and mass of mortar specimens after 28 cycles of alternate wetting at 23 °C and drying at 110 °C. Strength loss increased by the increase of FNS content with marginal increases in the mass loss. Though a maximum strength loss of up to 26% was observed, the values were only 3–9% for 25–100% FNS contents in the mixtures containing 30% fly ash. The XRD data showed that the pozzolanic reaction of fly ash helped to reduce the strength loss caused by wet–dry cycles. Overall, the volume of permeable voids (VPV) and performance in wet–dry cycles for 50% FNS and 30% fly ash were better than those for 100% OPC and natural sand

Three decades of monitoring in the Rio Cordon instrumented basin: Sediment budget and temporal trend of sediment yield

This paper investigates nearly 30 years of monitoring of sediment fluxes in an instrumented Alpine basin (Rio Cordon, Italy). The collected bedload and suspended sediment transport data allows sediment dynamics to be analyzed at different time scales, ranging from short- (single event) to long-term (three decades). The Rio Cordon monitoring station has been operating since 1986, continuously recording water discharge, bedload and suspended load. At the flood event scale, a good relationship was found between peak discharges (Qpeak) and sediment load (bedload and suspended load). The inter-annual sediment yields were analyzed, also assessing the contribution of the single floods to the total sediment budget. The annual suspended load ranges from 10 to 2524 t yr− 1, while the bedload varies from 0 to 1543 t yr− 1. The higher annual yields were recorded in the years when large floods occurred, highlighting that the sediment budget in the Rio Cordon is strongly controlled by the occurrence of high magnitude events. Investigation of the seasonal suspended load contribution demonstrated that from 1986 to 1993 most fine sediments were transported during the snowmelt/summer seasons, while autumn and snowmelt were the dominant seasons contributing to sediment yield in the periods 1994–2002 and 2003–2014, respectively. The mean annual sediment yield from 1986 to 2014 is equal to 103 t km− 2 yr− 1, and overall, bedload accounts for 21% of the total sediment yield. The ratio between the sediment transport and the effective runoff of the events allowed the temporal trends of transport efficiency to be inferred, highlighting the existence of periods characterized by different sediment availability. In particular, despite no significant changes in the hydrological variables (i.e. rainfall), nearly a decade (1994–2002) with high transport efficiency appears to have occurred after an exceptional event (recurrence interval > 100 years). This event affected the sediment availability at the basin and channel bed scales, and provided a legacy influencing the sediment dynamics in the basin over the long-term by increasing the transport efficiency for approximately a decade. This work benefits from the long-lasting monitoring program undertaken in the Rio Cordon and is the product of long-term data series. The quasi-unique dataset has provided detailed evidence of sediment dynamics over about three decades in a small Alpine basin, also enabling the effects triggered by an exceptional event to be analyzed