Influence of calcined kaolin on mortar properties

The use of calcined clay, in the form of metakaolin (MK), as a pozzolanic material for mortar and concrete has received considerable attention in recent years. The present paper describes the results of a research project initiated to study the calcination of local kaolin at various temperatures (650–950 °C) and durations (2, 3 and 4 h) to produce MK with a high pozzolanic activity. The pozzolanic activity was assessed by 28-days compressive strength and hydration heat methods. The maximum identified activity was obtained at 850 °C for 3 h duration. An increase of both hydration heat and compressive strength was obtained when ordinary Portland cement was replaced by 10% MK. The use of ternary blended cement improves the early age and the long-term compressive strength. The durability was also enhanced as better acidic resistance was observed.     

Chemical and structural optimization of ZnCl2 activated carbons via high temperature CO2 treatment for EDLC applications

Development of biomass based activated carbon materials for electrical double layer capacitor (EDLC) usage has gained attention as a result of requesting efficient and low cost energy storage device production. In this study, pine cone based activated carbons were produced with a combined chemical and physical activation route. ZnCl₂ and CO₂ were used for chemical and physical activation of the material, respectively. Activation parameters are adjusted to give different chemical and textural characteristics. FTIR and Raman spectroscopies were used for functional group identification and structural order characterization, respectively. As a result, efficient active materials for EDLC usage were obtained, with as high as 87 F/g specific capacitance in organic electrolytes.     

Sensory Profiles and Seasonal Variation of Black Walnut Cultivars

Black walnut (Juglans nigra L.) is a North American hardwood tree valued for producing nuts and wood. Black walnut cultivars were evaluated by a trained panel over 2 growing seasons to determine the seasonal variation in the sensory profile. Results showed that cultivars were significantly different on 3 appearance (skin color, nutmeat color, and kernel roughness), 1 aroma (black walnut ID), 5 flavor (black walnut ID, banana‐like, piny, rancid, and overall nutty), and 2 texture attributes (surface roughness and hardness). These profiles were compared to results collected in 2011 to determine differences between growing seasons. Results showed 4 flavor attributes (black walnut ID, overall nutty, fruity‐dark and rancid) had an interaction effect of year and cultivar, while 6 attributes (brown, caramelized, floral/fruity, piny, musty/dusty, and oily) showed a main effect of year. In general, flavor attributes had higher intensities in 2011 than in 2013. These results suggest that seasonal variation may influence flavor profile more than cultivar. Thus, using samples from only 1 growing season when testing agricultural products may not provide adequate information for the long term.     

Investigation of SPECT/CT cardiac imaging using Geant4

The purpose of this paper is to propose a friendly computational framework able to investigate particles tracking through different compartments of the human being using dedicated numerical techniques.The main building blocks of this framework are:(i) convenient X-ray spectra calculator for different filter/anode combination,(ii) realistic voxelized computational human phantom,(iii)validated Geant4-based Monte Carlo simulation,and(iv)extendable and free image processing software.We studied the multimodality SPECT/CT cardiac imaging using specific spectrum of the ~(99m)Tc and 120 kVp X-ray beam,for internal and external exposure,respectively.The application of the framework to quantify the loss of information between combined and simultaneous coregistration was carried out.Two main objectives were addressed:(i) an ideal geometry was simulated for educational purposes(ii) a realistic case study was carried out,for research purposes,concerning the modeling of the GE Infinia II 3/800 Gamma Camera.We compared the effect of using a Na I(Tl) and CZT crystal detector,and a LEHR and MEGP collimator with different uptake values of the heart organ(1:1,5:1 and 50:1) for both simultaneous andcombined SPECT/CT images.We confirmed the usefulness of the Na I(Tl) crystal with the LEHR collimator for such kind of study.     

Hydration heat kinetics of concrete with silica fume

The objective of this study was to evaluate the influence of silica fume on the hydration heat of concrete. Portland cement was replaced by silica fume in amounts from 10 % to 30 % by mass in concrete with w/(c+sf) ratios varying between 0.25 and 0.45. A superplasticizer was used to maintain a fluid consistency. The heat of hydration was monitored continuously by a semi-adiabatic calorimetric method for 10 days at 20 °C. The calorimetric study indicated that the hydration was modified by the presence of silica fume. In the early stages, the silica fume showed a high activity and accelerated the hydration rate as compared to that of the reference concrete. The fine silica fume particled provided nucleation sites for hydrates growth. Then the pozzolanic activity took over and increased both strength and the hydration heat. A substitution of Portland cement by 10% with silica fume produced greater strength and cumulative heat of hydration as compared to that of the reference concrete.     

Effect of fine aggregate replacement with desert dune sand on fresh properties and strength of self-compacting mortars

This paper presents the results of an experimental study that investigated the rheological and mechanical properties of self-compacting mortars incorporating fine dune sand (DS), which has a tight Particle size distribution. Mortar mixtures were prepared with crushed sand (CS) or river sand (RS) in which the fine aggregates were replaced partially by different percentages of DS of 0, 25, 50, 75 and 100%. The effect of DS on the fresh mortars properties was studied using the mini-slump flow, V-funnel flow time and viscosity measurements tests. Compressive strength and flexural strength were determined at age of 3, 7 and 28 days. Experimental results indicate an improvement in fresh rheological without reducing in mechanical properties of self-compacting mortars when fine aggregates were replaced partially with DS (50%). However, at high-level DS replacement (75%) the slump flow decreases. The replacement of the DS to the CS or to the RS shows an increase in the mixture viscosity. In general, the compressive and flexural strength were not significant affected with an increase in DS replacement. Finally, based on the results obtained in this investigation, DS may provide a readily available alternative material as fine aggregates in mortar application.     

Quantification and analysis of heat hydration of blended cement at different temperature

The study of the hydration kinetics appears as a prerequisite for understanding the physical and mechanical phenomena that control the behavior of cementitious materials. This research is based on monitoring the evolution of the degree of hydration for ordinary cement and those containing 10% of limestone powder, 20% of natural pozzolana or 30% of the blast furnace slag under high temperatures. The results provide a better understanding the effect of cure temperature on the hydration kinetics and understand the contribution of mineral additions on improving the cement properties. A new model proposed gives the satisfaction results for predicting in later age the heat of hydration of cements blended kept under constant temperatures. The latter has a wider appreciation of the results, where it gives correlation coefficients very close of unity. This justifies the reliability of this new model proposed.     

Combined effect of chemical nature and fineness of mineral powders on Portland cement hydration

This paper focuses on the influence of the chemical nature and the fineness of the fillers on the hydration process and on the compressive strength development. Four different types of fillers are considered in combination with Portland cement: quartzite filler, alumina filler, limestone filler, and silica fume. The study deals with blended mortars having a 0.45 water to powder (cement and filler) ratio with a 10% substitution of cement by filler. Quartzite fillers do not seem to accelerate the hydration process in a significant way. No positive effect is noticed on the strength development either. The presence of a fine inert alumina powder increases the rate of early hydration of Portland cement. The greater the fineness, the faster the rate of hydration heat development. This reactivity leads to an increase in the compressive strength at early age for mortar containing the finest alumina powders. In case of coarse alumina powder, no acceleration effect is obtained. Finely ground limestone (calcite) fillers promote heterogeneous nucleation of hydrates which significantly accelerates hydration. At early age, this also results in an increased mortar compressive strength in comparison with the control mortar. From the obtained results, it is clear that both chemical natures as well as fineness are important with regard to the accelerating effect of the hydration process. With increasing fineness, the accelerating effect increases. For powders with comparable fineness, it is clear that limestone powder has a more significant accelerating effect than silica fume and alumina filler. Quartzite filler seems to have no significant effect.     

Effects of experimental ternary cements on fresh and hardened properties of self-compacting concretes

Self-compacting concrete (SCC) is a concrete that flows alone under its dead weight and consolidates itself without any additional compaction and without segregation. As an integral part of a SCC, self-compacting mortars (SCMs) may serve as a basis for the mix design of concrete since the measurement of the rheological and viscosity properties of SCC is often impractical due to the need for complex equipment. This paper discusses the properties of SCM and SCC with mineral additions. ordinary Portland cement (OPC), natural pozzolana (PZ), and marble powder (MP) are used in ternary cementitious blends system following the cement substitution with PZ and MP in ratio 1/3. Within the framework of this experimental study, a total of 12 SCM and 6 SCC were prepared having a constant w/b ratio of 0.40. The fresh properties of the SCM were tested for mini-slump flow diameter, mini-V-funnel flow time, and viscosity measurement. Slumps flow test, L-box, J-ring, V-funnel flow time, and sieve stability were measured for SCC. Moreover, the development in the compressive strength was determined at 3, 7, 28, 56, and 90 days. Test results have shown that using ternary blends improved the fresh properties of the mixtures. The combination of natural pozzolana and marble powder increase the slump flow test up to 826 mm for the mixture prepared with 10% of mineral additions. Moreover, the use of mineral addition reduced the time flow to 4.27 s for SCC with 20% mineral addition, thus reducing the viscosity of all mixtures. Addition of MP increases the capacity of the passage through the plates between 88.75 and 93.50% for SCC with 7.5 and 15% of MP, respectively. The ternary system (PZ and MP) improve the sieve stability with the value for 4.07% of SCC with 50% of substitution compared for SSC without additions. The compressive strength of SCC at 90 days with 40% of PZ and MP was similar to that of OPC.