M. Bonilla

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.

Properties of Portland cement mortars incorporating high amounts of oil-fuel ashes

Abstract The residue of oil-fuel burned at the electrical power plant of Grao de Castellon (Spain) has been incorporated in Portland cement mortar and concrete. The used oil-fuel ash (OFA) had a high percentage of magnesium compounds because of magnesium oxide addition for removing slag and ashes from boilers and pipes. Several studies had been carried out on stabilization of toxic metals also occurring in oil-fuel ashes (particularly vanadium and nickel), by mixing with coal fly ashes and cement. In this case, the presence of magnesium compounds in the composition of the studied oil-fuel ashes could alter the mechanical and chemical properties of the cement matrix in fresh and hardened mortar and concrete. We present here the chemical, physical and mineralogical characterization of oil-fuel ashes and the behaviour of Portland cement mortars incorporating high amounts of these oil-fuel ashes. The study includes workability, water demand, setting time, expansion and compressive strength developments. Preliminary results demonstrate a high absorption of water by oil-fuel ash particles, which promotes an increase in the water/cement ratio for a given workability. Acceleration of Portland cement/oil-fuel ash pastes setting times was observed, due to the presence of carbonates. On the other hand, no significant expansion in specimens due to the presence of magnesium compounds was detected and, consequently, mechanical properties of hardened mortars containing oil-fuel ashes did not decrease with curing time. Compressive strengths for mortars containing OFA were much lower, however, than control mortar samples.

Ternary Blended Cementitious Matrix for Vegetable Fiber Reinforced Composites

The present work analyses the behaviour of different binder matrices in order to implement the addition of paper pulp as reinforcement for cementitious composites and assesses the composites flexural properties with time. To prevent microfibers degradation in high-alkaline environments, lower alkaline matrices may be developed. In the present study ternary binder matrices containing ordinary Portland cement (OPC), gypsum (G) and fluid catalytic cracking catalyst residue (FC3R) are presented for that purpose. To assess the performance of the alternatives matrices, pH and conductivity evolution with time were monitored. Also flexural tests were carried out with the intention of evaluate the efficiency of the matrix to preserve fibres within the composite. According to pH and conductivity results is proved that this ternary system offers lower values at early stages (at 3 days) when compared to OPC systems. This inferior alkalinity might be associated to the better mechanical performance with time of the composites when the ternary matrix is used. After 10 months ageing, all the mechanical properties were higher when compared to composites using OPC. Particularly remarkable is the preservation after ageing of the specific energy and deflection at the modulus of rupture when the low-alkalinity matrices were employed, on the contrary what occurred with samples containing OPC where specific energy and deflection were nearly disappeared.

Study of pozzolanic properties of two sugarcane bagasse ash samples from Honduras

It is well known that the combustion of agricultural waste such as rice husk, bamboo leaf and bagasse among others, depending on the combustion process, may produce powders with pozzolanic properties. Two samples of sugarcane bagasse ash (SCBA) from Honduras were studied (from Ingenio Santa Matilde, close to the city of San Pedro Sula, and from Ingenio Los Mangos, close to the city of Choluteca). The samples were physico-chemically characterized and pozzolanic reactivity was checked. Both samples of ash have a chemical composition comprising mainly oxides of silicon, iron and aluminum and have similar values of the loss on ignition. Both ashes showed high ability for reacting towards hydrated lime. Moreover, the evolution of the mechanical compressive strength of mortar specimens incorporating these ashes (25% replacement of Portland cement by SCBA) was also studied. Compressive behavior revealed that for this dosage, the cementing efficiency of SCBA is similar to Portland cement.The results suggested that ashes from San Pedro Sula and Choluteca have very good pozzolanic properties. The cement and concrete industries in Honduras have a huge chance for reusing this type of waste in high quality construction materials. Keywords: pozzolan, sugarcane bagasse ash, agricultural waste, mechanical strength.