Decrease In Sorptivity Research Articles

Effects of incorporating silica glass powder as a supplementary cementitious material on selected properties of portland cement mortar

The use of waste glass powder as a partial replacement for cement is an emerging practice for sustainable cement-based construction. Several studies have demonstrated that finely ground-powdered glass could be an interesting supplementary cementitious material (SCM). However, the performance of such material is influenced by the chemical composition of glass and its pozzolanic reactivity. In this context, the goal of this study is to investigate the use of silica-glass powder (SGP), which is characterized by a high content of silica (>96%), as a partial replacement of Portland cement in mortar. In this research work, mortars containing 7.5%, 10, 12.5, 15 and 20% SGP in replacement of an amount of cement, with three different water-to-binder ratios of 0.55, 0.60 and 0.65 are studied. Selected properties have been investigated at both fresh and hardened stages, which include workability, air content, flexural and compressive strengths estimated by destructive and non-destructive methods, water absorption by capillarity, permeability to chlorides and chloride ions diffusion. The experimental results confirm that incorporating SGP improves the mechanical strength of the mortar, notably in the long-term, and can considerably enhance its durability properties, especially by a decrease in sorptivity of the mortar and by an increase of its resistance to chloride ions diffusion. Correlations between selected physical and mechanical properties and certain durability indices are also established and discussed in this study.

Investigation of two different water-dispersed graphene on the performance of graphene/cement paste: Surfactant and superplasticizer effect

• The compressive strength of graphene-based cement paste with 0.1% SP was increased by 82.05%. • Surfactants did not show better performance in the hydration process due to their hydrophilicity. • The optimized concentration of graphite and dispersing agents is determined. • The graphene produced by the superplasticizer has the lowest level of defects. • The microstructure results are in accordance with compressive resistance results. The excellent performance of graphene-based materials to use in concrete has recently attracted the attention of civil engineering researchers. However, the application of graphene faces obstacles due to the high cost of graphene and agglomeration phenomena in cementitious composites. As a result, research into the production of water-dispersed graphene, a combination of graphite and a dispersing agent, is a particularly cost-effective alternative. In this regard, it is essential to select a dispersing agent capable of effectively separating graphene layers while also improving mechanical properties and impermeability. In this study, the influence of two different dispersive agents, surfactant (S) and superplasticizer (SP), on mechanical properties, permeability, and microstructure of cement paste was investigated. SEM, TEM, and Raman spectroscopic analyses demonstrate that multilayer graphene sheets made using superplasticizer have higher quality and fewer defects than surfactant-based sheets. After 3 days of aging, the compressive strength of graphene-containing cement paste with 0.1 % superplasticizer increased by 82.05 % compared to the control paste. On the other hand, a decrease in sorptivity by 54 % compared to the control paste is observed by graphene-containing cement paste with 0.56 g/l surfactant. The microstructure investigation revealed that graphene accelerates the CH and C-S-H productions due to the nucleation effect in the composite cement matrix; however, the effect of SP is more significant than S in cementitious composites. This research suggests that water-dispersed graphene generated by 0.1 % SP and 0.56 S g/l has the potential to be used as an innovative admixture in cement-based composite materials.

Sorptivity of water in enamel for categorizing caries lesions

ObjectiveThe aim of this research was to determine the association between sorptivity of water and the state of mineralization in carious enamel of different stages of severity. MethodsAs a preliminary work, water droplets of 1.5 μL were placed on the surfaces of hydroxyapatite (HA) discs of different densities. The water droplet profile was dynamically recorded every second over a period of 10 s using a contact angle meter to determine the relationship between sorptivity and density. To measure and calculate sorptivity on enamel surfaces, varnish was painted on the labial surface of 96 extracted caries-free human teeth, leaving two 1.4 ± 0.1 mm diameter circular exposed test sites. The specimens were randomly divided into 6 groups (n = 16) and subjected to 0(G0), 7(G7), 14(G14), 21(G21), 28(G28) and 35(G35) days of pH cycling, respectively. A 0.7 μL water droplet was placed on each exposed site and Optical Coherence Tomography was used to measure its height every 10 seconds for 2 min. Sorptivity was computed by considering sorption equations and Washburn's analysis of capillary kinetics and correction for evaporation was also performed. Micro-Computed Tomography scans of the specimens were obtained and delta Z (ΔZ) is the parameter used to measure mineral loss. ΔZ at 10 μm (ΔZ10) and 50 μm (ΔZ50) from the surface were calculated. One-way ANOVA and Post-hoc Tukey tests were used to compare sorptivity between groups and bivariate correlations were used to analyze the association between sorptivity and ΔZ. ResultsSorptivity was found to be inversely and linearly correlated with HA density with R2 value of 0.95. With enamel, there is a general trend of increase in mean sorptivity from G0 to G35, except for a decrease in G21. The same trends were observed for both ΔZ10 and ΔZ50. The decrease in sorptivity in G21 coincided with the presence of a surface hypermineralized layer in G21 samples. Post-hoc Tukey showed significant differences in mean sorptivity between G0 and G14, G0 and G21 as well as G14 and G21. Post-hoc Dunnett’s T3 showed significant differences for ΔZ10 between G0 and G14 as well as G14 and G21. Significant correlation between mean sorptivity and ΔZ10 was detected with Pearson correlation coefficient of 0.461. For ΔZ50, post-hoc Tukey showed significant differences between G0 and G14 but no significant difference was detected between G14 and G21. No correlations were detected between mean sorptivity and ΔZ50. SignificanceSorptivity was found to be inversely and linearly correlated with HA density with R2 value of 0.95. With enamel, there is a general trend of increase in mean sorptivity from G0 to G35, except for a decrease in G21. The same trends were observed for both ΔZ10 and ΔZ50. The decrease in sorptivity in G21 coincided with the presence of a surface hypermineralized layer in G21 samples.

31—THE SORPTION OF WATER BY CELLULOSE AND EIGHT OTHER TEXTILE POLYMERS: PART III—THE SORPTION OF WATER VAPOUR BY TEXTILE POLYMERS AT 120°C

Data on the absorption of water vapour (0—100% r.h.) at 120°C and 150°C are presented and analysed for cotton, viscose, cellulose triacetate, secondary cellulose acetate, drawn nylon 6.6 yarn and Terylene. The cotton and viscose rayon were severely degraded by the treatments in hot water vapour; the two cellulose acetates were, however, only slightly affected chemically during the time-scale of the measurements. All the samples (with the possible exception of the Terylene) showed an increase in crystaliinity and decrease in sorptivity as a result of the treatments. With the two celluloses and the nylon, the effect of temperature on the sorption was normal (i.e., a decrease in sorption with increase in temperature at all values of r.h.). With the two cellulose acetates, however, the 150°C-isotherm crossed over the 120°C-isotherm at high relative humidities. The sorption of water vapour by Terylene at 120°C and 150°C was slightly higher than at 30°—90°C, in agreement with the trend displayed by these low-te...

37—MOISTURE RELATIONS OF CELLULOSE. IV—THE EFFECT OF STABILIZATION OF COTTON CELLULOSE ON ITS SORPTIVITY AT DIFFERENT TEMPERATURES, AND ITS BEARING ON ISOSTERIC HEATS OF SORPTION

Adsorption–desorption cycles of water vapour from dryness to saturation are determined on unstabilized cellulose at 15°C, 30°C and 4O°C, and on stabilized cellulose from 0°C to 50°C. As well as bringing about rcproducibility of the sorption isotherms, which is particularly lacking on desorption paths on unstabilized cellulose, stabilization causes the same displacement of the isotherms whether it is achieved using water vapour at 18°C or liquid water at 60°C. Stabilization lowers the 15°C isotherms, particularly at higher humidities, and especially on the desorption path. At 40°C, the decrease in sorptivity is apparent only at high humidities, and the adsorption and desorption isotherms cross over the corresponding ones on unstabilized cellulose at lower humidities. Stabilization thus seems to lower the temperature above which the adsorption isotherms become closer together. This ‘optimum’ temperature is about 30°C for unstabilized cellulose and about 15°C for stabilized. The hysteresis loop on stabilized...