Ferdi Cihangir

Utilization of industrial waste products as pozzolanic material in cemented paste backfill of high sulphide mill tailings.

In this study, the potential use of the industrial waste products including waste glass (WG), fly ash (FA), granulated blast furnace slag (GBFS) and silica fume (SF) as pozzolanic additive for the partial replacement of ordinary Portland cement (OPC) in cemented paste backfill (CPB) of sulphide-rich mill tailings was investigated. The influence of these industrial waste products on the short- and long-term mechanical performance of CPB was demonstrated. The rate of development of strength of CPB samples tended to slow down when the pozzolanic wastes were incorporated or increased in dosage in the binder phase. Severe losses (by 26%) in the strength of CPB samples produced from exclusively OPC occurred after an initial curing period of 56 days. The addition of WG (10-30 wt%) as a partial replacement of OPC was observed to aggravate further the strength losses of CPB samples. GBFS, FA and SF appeared to improve the long-term performance of CPB samples; albeit, only GBFS and SF could be incorporated into the binder phase only at certain levels i.e. up to 20 wt% GBFS and 15wt% SF in order to maintain a threshold strength level of 0.7MPa over 360 days. SEM studies have provided further insight into the microstucture of CPB and confirmed the formation of deleterious gypsum as the expansive phase. These findings have demonstrated that the industrial waste products including GBFS and SF can be suitably used as mineral additives to improve the long-term mechanical performance of CPB produced from sulphide-rich tailings as well as to reduce the binder costs in a CPB plant.

Effect of natural pozzolans as mineral admixture on the performance of cemented-paste backfill of sulphide-rich tailings

This paper presents the effect of the natural pozzolans as mineral additives on the short- and long-term strength and stability performance of cemented paste backfill (CPB) samples. Prior to their use in CPB studies, the natural pozzolans — the volcanic tuffs (Akkus Trass [AT] and Fatsa Trass [FT]) and pumice (KP) — were tested for their pozzolanic characteristics. These tests revealed that the pozzolanic activity of the natural pozzolans is closely inter-related with their content of reactive silica and, accordingly, KP has the highest pozzolanic activity. The addition, or increasing the amount, of natural pozzolans in the binder phase resulted in a slower rate of strength development of CPB samples. The deterioration in stability of CPB samples prepared from Portland cement (PC) alone (i.e. a strength loss of 24.6%) occurred following 56 days. The replacement of PC with FT and AT led to even higher losses in strength. However, the addition of KP (up to 30 wt%) mitigated, to a certain extent, long-term strength and stability problems with the losses in strength of CPB samples consistently lower than 20%. It can be inferred that the performance of the natural pozzolans as a mineral additive in CPB is dependent intimately on their pozzolanic characteristics.

Mechanical, hydrological and microstructural assessment of the durability of cemented paste backfill containing alkali-activated slag

Abstract The durability of full (FT) and deslimed sulphide-rich tailings (DT) cemented paste backfill (CPB) of alkali-activated slag (AAS; LSS–S: activated slag with aqueous sodium silicate and SH–S: activated slag with sodium hydroxide) was investigated based on the mechanical (strength), hydraulic and microstructural properties. DT and AAS improved the strength gain rate by decreasing the total- and macro porosity. DT and LSS–S configuration had a profound effect on strength development and produced 4.3–9.9-fold strengths than ordinary Portland cement (OPC) samples. DT also favoured the degree of cementation with dense packing matrix, decreased the permeability and thus, limited the adverse effects of acid and sulphate. DT hindered the decalcification of C–S–H leading to higher Ca/Si ratios for OPC while AAS samples exhibited approximately similar ratios over the curing period. SH–S led to drying shrinkage due to the greater amount of threshold pores. LSS–S/DT combination provided better durability performance in case of aggressive environments by improving the microstructure of CPB.

Core size effect on the dry and saturated ultrasonic pulse velocity of limestone samples.

This study presents the effect of core length on the saturated (UPVsat) and dry (UPVdry) P-wave velocities of four different biomicritic limestone samples, namely light grey (BL-LG), dark grey (BL-DG), reddish (BL-R) and yellow (BL-Y), using core samples having different lengths (25-125mm) at a constant diameter (54.7mm). The saturated P-wave velocity (UPVsat) of all core samples generally decreased with increasing the sample length. However, the dry P-wave velocity (UPVdry) of samples obtained from BL-LG and BL-Y limestones increased with increasing the sample length. In contrast to the literature, the dry P-wave velocity (UPVdry) values of core samples having a length of 75, 100 and 125mm were consistently higher (2.8-46.2%) than those of saturated (UPVsat). Chemical and mineralogical analyses have shown that the P wave velocity is very sensitive to the calcite and clay minerals potentially leading to the weakening/disintegration of rock samples in the presence of water. Severe fluctuations in UPV values were observed to occur between 25 and 75mm sample lengths, thereafter, a trend of stabilization was observed. The maximum variation of UPV values between the sample length of 75mm and 125mm was only 7.3%. Therefore, the threshold core sample length was interpreted as 75mm for UPV measurement in biomicritic limestone samples used in this study.

Practical Importance of Tailings for Cemented Paste Backfill

Mineral processing methods, such as flotation, are used to treat low-grade ores from mining operations; however, a significant amount of tailings are then generated (typically 95–98% of the feed ore). Therefore, mineral processing must also be essentially regarded as a “waste/tailings management” project (Ercikdi et al. 2012). The disposal, stability and safety of tailings, and their effects on water and soil, are important technical and environmental problems. For example, sulphide (i.e. pyritic) tailings can lead to the generation of acid mine drainage (AMD) when they are disposed under atmospheric conditions. This results in the release/mobility of heavy metals, such as arsenic (As), copper (Cu) and zinc (Zn) with the concomitant pollution of water resources and soil (Fig. 2.1).

Yüksek Fırın Cürufu ve Perlit İkamesinin Çimentolu Macun Dolgunun Mekanik ve Mikroyapı Özelliklerine Etkisi

Son yillarda Portland cimentosu (PC) yerine belirli oranlarda dogal ve yapay puzolanlarin kullanilmasi, cimentolu macun dolgunun (CPB) dayanim ve durayliliginin iyilestirilmesi, asit ve sulfat etkisine karsi direncinin arttirilmasi ve baglayici maliyetlerinin azaltilmasi icin oldukca yaygin hale gelmistir. Bu calismada yuksek firin curufu (YFC) ve perlit (P) ikamesinin CPB’nin mekanik ve mikroyapi ozelliklerine etkisi arastirilmistir. PC yerine agirlikca %20 YFC ve P ikame edilerek hazirlanan 84 adet CPB numunesi 7, 14, 28 ve 56 gunluk kur sureleri sonunda tek eksenli basinc dayanimi ve gozeneklilik (porozite) testlerine tabi tutulmustur. YFC’li numuneler 7-14 gunde PC numunelerine gore daha dusuk dayanim uretirken 28-56 gunde bu numunelerin basinc dayanimini gecmistir. Gozeneklilik sonuclari incelendiginde, YFC’li numunelerin gozenekliligi kur suresinin artmasiyla daha fazla iyilesme gostermistir. Perlit katkili numuneler ise basinc dayanimi ve gozeneklilik gelisimi acisindan zayif kalmistir. Elde edilen bulgular YFC’nin CPB icerisinde belirli oranlarda kullaniminin mekanik ve mikroyapi ozellikleri acisindan faydali oldugunu gostermistir.

Effect of Tunnel Blasting Operation on the Surface Penstock Pipe

This paper presents the investigation of the effect of ground vibration components induced blasting events in Ordu-Mesudiye Highway Topcam tunnel on the penstock pipe (PP) having 35-400 slopping of Topcam Hydro-Electrical Power Plant (HEPP). Until the tunnel excavation passed under the PP of HEPP, a total of 37 shots (26 upper halves and 11 lower half) were monitored and the ground vibration components (peak particle velocity, acceleration, displacement and frequency) were measured in two different stations. It was also examined whether the concrete platform under this PP had a crack, damage or etc. As a result of these workings, a maximum of 220 kg total charge was used and the charge weight per delay varied between 1.0-18 kg in the shots. The distance of shots to measurement station was between 78.04 and 170.16 m. 6 PPVs, 11 accelerations and a displacement value exceeded the threshold values determined. However, the vibration values were taken under control with changing the blasting parameters and it was provided that the tunnel excavation passed under the PP of Topcam HEPP.