M.V. Borrachero

EVALUATION OF THE POZZOLANIC ACTIVITY OF FLUID CATALYTIC CRACKING CATALYST RESIDUE (FC3R). THERMOGRAVIMETRIC ANALYSIS STUDIES ON FC3R-PORTLAND CEMENT PASTES

Abstract 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.

Mechanical treatment of fly ashes. Part I: Physico-chemical characterization of ground fly ashes

Physico-chemical characteristics of mechanically treated fly ashes are investigated. An original fly ash was ground, using a laboratory mill, for several times (from 10 to 60 minutes). Respect to physical characterization, fineness increasing of samples with grinding time was observed, but loss of effectiveness occurred for grinding time longer than 20 minutes. Ground samples showed higher specific gravity probably due to the presence of cenospheres in the original fly ash. Only a little change in mineralogical composition of fly ashes was observed when grinding: calcium carbonate formation by reaction of calcium oxide with carbon dioxide. Chemical behavior (pH and conductivity) of fly ash/water suspensions were studied and acid neutralization capacities measured.

Mechanical treatment of fly ashes part II: Particle morphologies in ground fly ashes (GFA) and workability of GFA-cement mortars

Abstract Mechanical treatment (by grinding) effects on particle morphology and specific gravity of fly ashes, and workability of ground fly ash (GFA) cement mortars have been studied. Different shape morphologies of GFA particles have been established: shell shaped and irregular solid fragments. Real and bulk specific gravity values were measured, proving that grinding process increased the content of poor shape particles. Particle Packing Factor (PPF) for GFA decreased below 50%. Workability of GFA-cement mortars is negatively affected, but it is still greater that only cement mortar one. Good correlations between flow table spread (FTS) values per water volume unit and fly ash replacing percentage have been obtained, and a relative workability factor W r is established. Determination of W r value permits to compare the effect of grinding or other fly ash processing methods on workability of mortars. Finally, good linear relationships between W r values and the inverse of mean diameter particle or calculated specific surface area were found.

Reuse of sewage sludge ashes (SSA) in cement mixtures: the effect of SSA on the workability of cement mortars

The influence of sewage sludge ash (SSA) on workability of cement mortars has been studied. The irregular morphology of SSA particles produced a decrease of mortar workability. A nonlinear reduction of workability in mortars containing SSA was observed, but when SSA content in mortars was increased the workability reduction was less significant. A superplasticizer is used in order to compensate the decrease of workability produced by SSA. When SSA sized fractions were used, only significant differences in workability for mortars prepared with high water volumes or with the presence of superplasticizer were observed.

Mechanical treatments of fly ashes. Part III: Studies on strength development of ground fly ashes (GFA) — Cement mortars

Abstract Early and medium-term strength developments for mortars containing ground fly ashes (GFA) were studied and compared with the behaviour of mortars containing non-mechanically treated fly ash. Linear correlations between mechanical properties and the logarithm of curing time for mortars containing 15–60% fly ash replacing percentages were established. Compressive Strength Gain (SGi) and Pozzolanic Effectiveness Ratio (PER) were calculated, suggesting the increasing of pozzolanic activity with grinding of fly ash. A new mathematical model has been proposed for mechanical properties of mortars containing high replacing percentages and for a wide curing time range. Optimums for mechanical properties were calculated for mortars containing GFA.

DETERMINATION OF AMORPHOUS SILICA IN RICE HUSK ASH BY A RAPID ANALYTICAL METHOD

A rapid analytical method for evaluating amorphous silica in rice husk ash (RHA) is provided and therefore an assessment of its potential pozzolanic activity. The method is based on bringing the siliceous non-crystalline fraction of the pozzolan into solution as glycerosilicate by treating the test material with glycerol. The titration of the resulting solution is performed with an aqueous glycerol solution of barium hydroxide. Data are compared to those obtained using a standard method and a good concordance is achieved. It is demonstrated that the proposed method can be a useful tool for evaluating amorphous silica in RHA.

Use of sewage sludge ash (SSA)-cement admixtures in mortars

Abstract The chemical composition of sewage sludge ash (SSA) and their sized fractions are studied, some differences in chemical composition are observed. SEM studies show irregular shape of SSA particles and sized fractions, this shape has a decisive influence on workability of mortars. The effect of replacing 15% of portland cement by SSA and their sized fractions: coarse (SSAC) and medium (SSAM) obtained by sieving on compressive (Rc) and flexural (Rf) strength of mortars was investigated. The study reveals an enhancement of strength when ashes are used, due to probably, pozzolanic properties of SSA.

Determination of the pozzolanic activity of fluid catalytic cracking residue. Thermogravimetric analysis studies on FC3R–lime pastes

Abstract Spent fluid catalytic cracking catalyst (FC3R) from a petrol refinery played a pozzolanic role in portland cement system as revealed by previous experimental data. In the present study, the pozzolanic activity of FC3R was investigated by means thermogravimetry (TG) of cured lime–FC3R pastes. The influence of pozzolan/lime ratio on the pozzolanic activity was investigated. Due to the chemical composition of FC3R is similar to metakaolin (MK), and knowing that MK has a high pozzolanic activity, the latter was used as a material of comparison in this study. The scope of the study is the determination of the pozzolanic activity of FC3R and the evaluation of amount and nature of pozzolanic products. The products obtained from the reaction between FC3R components (SiO2/Al2O3) and calcium hydroxide (CH) have been characterized, finding that the main pozzolanic reaction product was similar to hydrated gehlenite (calcium aluminosilicate hydrate) CSH and CAH were also formed in the reaction. FC3R showed higher pozzolanic reactivity than metakaolin, for low-lime content pastes and early curing age. Thermogravimetry, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) became very useful techniques for evaluation of reactivity.

Mechanical behavior of mortars containing sewage sludge ash (SSA) and Portland cements with different tricalcium aluminate content

The influence of sewage sludge ash (SSA) on cement mortars strength has been studied. To evaluate better the increase of strength compared to control mortar, relative compressive strength gain (CSGr) and flexural strength gain (FSGr) were calculated. The experience shows that SSA behaves as an active material, producing an increase of compressive strength compared to control mortar, probably due to pozzolanic properties of SSA. It can be emphasized that high sulfur content of SSA (12.4%) does not seem to have influence on compressive strength of mortars containing SSA. When CSGr of mortars containing different types of cements are compared, no clear correlation is observed between CSGr and C3A content in cement.

Physical, chemical and mechanical properties of fluid catalytic cracking catalyst residue (FC3R) blended cements

Abstract The use of fluid catalytic cracking catalyst residue (FC3R) as a cement replacement material has been studied. Four FC3R-blended cements were prepared by the replacement of Portland cement by FC3R in the 6–20% range by mass. Chemical, physical and mechanical properties of the FC3R-blended cements were compared to those of ordinary Portland cement (OPC). Chemical and mechanical tests suggested important pozzolanic activity of FC3R-replacing material. An increase in the compressive strength of the FC3R-blended cements was observed, yielding equal or greater compressive strength than mortars prepared with OPC.