Evaluation of the pozzolanic activity of fluid catalytic cracking catalyst residue (FC3R). Thermogravimetric analysis studies on FC3R-Portland cement pastes

Spent fluid catalytic cracking catalyst (FC3R) from a petrol refinery has shown a great pozzolanic activity in lime pastes as have been demonstrated in previous studies. Based on these results, the pozzolanic activity of the FC3R in Portland cement pastes has been investigated. This evaluation has been carried out by means of thermogravimetry (TG) of cured FC3R-Portland cement pastes. The influence of water/binder ratio and the replacement percentage of FC3R on the pozzolanic reaction were investigated. Due to the chemical composition of FC3R that is similar to metakaolin (MK), and knowing that MK has a high pozzolanic activity, the latter was used as a material of comparison in the study of the water/binder ratio influence. The scope of this study is the determination of pozzolanic activity of FC3R when incorporated to Portland cement, and the evaluation on amount and nature of pozzolanic products. FC3R has shown a similar reactivity to MK, yielding similar pozzolanic products: CSH, CAH and CASH. The optimum replacing percentage in Portland cement pastes was in the 15-20% range.     

Study of ancient mortars from Sagalassos (Turkey) in view of their conservation

Since 1990, regular archeological excavations are done in the Roman city of Sagalassos (southwestern Turkey) by the Catholic University of Leuven (Belgium). The mineralogy and petrography of the lime mortars at Sagalassos have been studied in detail as part of an investigation of the provenance of mineral raw materials present in the territory of Sagalassos. The samples were analysed with optical microscopy on thin sections followed by XRD analyses to design a suitable repair mortar. The lime used as binder was burnt from local Triassic limestones and prepared by dry slaking. Three main types of aggregates have been identified: limestone from local Mesozoic limestones, crushed ceramics from locally produced coarse wares and volcanic tuff from a nearby volcanic region. To preserve the excavated remains in very harsh climatic winter conditions, experimental mixtures of restoration mortar have been tested for strength and frost resistance using similar raw materials as in ancient times. The proposed mortar for further on-site conservation and restoration consists of a mix of lime with crushed volcanic rock from the region of Isparta. This composition is very similar to the original Roman material and shows a high frost resistance in freeze-thaw testing.     

Supplementary cementing materials in concrete: Part II: A fundamental estimation of the efficiency factor

For comparing the relative performance of various supplementary cementing materials (SCMs: silica fume, fly ash, slag, natural pozzolans, etc.) as regards Portland cement, the practical concept of an efficiency factor may be applied. The efficiency factor (or k value) is defined as the part of the SCM in an SCM-concrete that can be considered as equivalent to Portland cement. In the present work, an alternative procedure for experimental determination of the k value is proposed, using the concept of the pozzolanic activity index. For the first time, also, the k value for equivalent strength was correlated with the active silica content of the SCM through analytical expressions. Artificial pozzolanic materials of various compositions and some natural pozzolans were studied. It was found and verified by experimental comparison that these expressions are valid only for artificial SCMs (fly ash, slag), whereas in the case of natural SCMs the k value is overestimated. Thus, knowing primarily the active silica content of the SCM, a first approximation of the k value can be obtained and, further, the strength of a concrete incorporating artificial SCM can be predicted.     

Effect of grinding of low-carbon rice husk ash on the microstructure and performance properties of blended cement concrete

The effectiveness of unground low-carbon rice husk ash (URHA) as a pozzolan and the effect of grinding the URHA to finer fractions for use in portland cement system were investigated. The properties investigated include the setting time and calcium hydroxide depletion of rice husk ash (RHA) pastes; microstructure and flow behavior of RHA mortars; strength and durability of RHA concretes. Results from this investigation suggested that the URHA and ground RHA (GRHA) mixtures performed better than the control mixtures in all tests conducted except water demand and setting time. The URHA mixture revealed denser microstructure compared to the control mixture. The internal porosity created by the coarse RHA grains in the matrix and their inability to completely participate in pozzolanic reaction may be the reasons for the poorer performance of the URHA mixture than compared to the GRHA mixture. The effect of grinding the RHA to finer fractions either substantially or slightly improved all properties except final setting time. With the performance of the GRHA concrete somewhat similar to that of the SF concrete, the use of ground RHA can be concluded to provide acceptable performance in portland cement systems.     

Volcanic ash and pumice as cement additives: pozzolanic, alkali-silica reaction and autoclave expansion characteristics

This study reports the results of investigation to assess the suitability of volcanic ash (VA) and pumice (VP) powder to be used as cement additives. Pozzolanic activity of VA and VP was tested according to the Italian standard and found to be acceptable. The strength activity index with Portland cement and the effectiveness of VA and VP admixture in controlling alkali-silica reaction and autoclave expansion were tested according to ASTM standards. Mortar cubes were specially prepared as per ASTM standards for these studies using different mixes with varying percentages of VA and VP (0-40%) as cement replacement. The results are then compared with ASTM requirements to assess the suitability of VA or VP as cement additives.     

Application of burnt clay shale as pozzolan addition to lime mortar

Burnt Czech clay shale of different grain fineness is applied as a new pozzolan addition to lime mortar. Experimental results show that the new lime-pozzolan mortars have significantly better mechanical properties and frost resistance than the reference lime mortar. The fineness of burnt Czech clay shale is a very important parameter affecting the properties of lime-pozzolan mortars; the best results are achieved with an average particle size of 4 μm. In a comparison with a lime-metakaolin mortar of the same composition, the frost resistance of the new lime-pozzolan mortars is significantly better, the mechanical, fracture-mechanical, hygric and thermal properties are either comparable or slightly better. Therefore, it can be concluded that the burnt Czech clay shale has a good potential to be used in lime-pozzolan mortars for renovation of historical buildings.     

Mineralogical and microstructural studies of mortars from the bath complex of the Roman villa rustica near Mošnje (Slovenia)

This study deals with the characterization of mortars collected from bath complex of the Roman villa rustica from an archeological site near Mošnje (Slovenia). The mortar layers of the mosaics, wall paintings and mortar floors were investigated. A special aggregate consisting of brick fragments was present in the mortars studied. The mineralogical and petrographic compositions of the mortars were determined by means of optical microscopy, X-ray powder diffraction and FTIR spectroscopy. Analysis of aggregate–binder interfaces using SEM-EDS revealed various types of reactivity rims. In order to assess the hydraulic characteristics of the mortars, the acid-soluble fractions were determined by ICP-OES. Furthermore, the results of Hg-porosimetry and gas sorption isotherms showed that mortars with a higher content of brick fragments particles exhibited a higher porosity and a greater BET surface area but a lower average pore diameter compared to mortars lacking this special aggregate.