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Statement of Problem: Mechanical strength and durability of dental composites are the main topics studied in this field of science today. This study examined fumed silica-based composite as a strong and durable restorative material through flexural and cycling test methods. Objectives: The purpose of this study was to evaluate the effect of silanization, ageing, cycling and hybridizing on mechanical properties of fumed silica-based resin composite. Materials and Methods: Composites were made of light-cured copolymer based on Bisphenol A glycolmethacrylate (Bis-GMA) and Triethylene glycoldimethacrylate (TEGDMA) at proportion of 50:50 which reinforced by fumed silica filler. For each composite sample, 5 specimen bars were made using Teflon mould (2 x 2 x 25 mm3). The samples with 12 wt% fumed silica (FS) were considered as a base line group. The samples were exposed to cyclic cold water (FS-CCW) and hot water (FS-CHW). The effect of silanization and adding more filler was studied together with samples containing 12 wt% (FS-S (12), 16 wt% (FS-S (16) and 20 wt% (FS-S (20) fumed silica filler. The filler was silanized with (γ-MPS). The degree of conversion was assessed with Fourier Transform Infra-Red spectroscopy. Flexural properties were evaluated with the Three-Point Bending test. Flexural data were analyzed with Excel software. Hardness was measured with an Atomic Force Microscope (AFM). Results: The degree of conversion of the resin reached 74% within 24 hrs. Salinization allowed more filler to be wetted by resin. Addition of silanized particles from sample FS-S (12) to sample FS-S (20) improved the mechanical strength. Hybridizing fumed silica with nano-silica (FS-N) had no significant effect on the strength, but nano-hardness improved greatly. Ageing and cycling had adverse effects on the strength of the sample FS. The flexural strength of FS-CHW was 72% less than FS sample. Conclusions: Sample FS-N with low diluent and filler percentage complied with the requirements of flexural strength was established by ISO 4049/2009 and may be cost benefit to be used as a dental composite for clinical application.

Polymer concretes are particle composites of polymers which are filled by aggregates. Polyesters, epoxies and acrylics have been used as binders in these materials which polyesters due to their suitable properties and acceptable cost are considered by the most of industries. One of the most considered issues about polyester polymer concretes is their weak performance and the low durability against acids and alkaline solutions. In this research, fracture mechanics (CMOD and K 1c ) and flexural strength ( σ ) of a polyester polymer concrete after 1, 3, 6 and 12 months of exposure to sulfuric acid 0.5 and 1 mol lit and carbonate/bicarbonate alkaline solution 0.0622 and 0.1245 mol lit were investigated. Results showed that both of aggressive solutions degraded polymer concrete samples. However acids caused more decrement in flexural strength and alkaline had more destructive effect on fracture mechanics. Furthermore, the concentration was more important in destructive effects especially for alkaline solution. The highest decrease in flexural strength, fracture toughness and CMOD were 37%, 36.1% and 59% respectively. SEM analysis was used to assess morphological changes accrued at fractured surfaces of the samples. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of hydrophilic polyvinyl alcohol (PVA) fiber’s content (1.2–2.0% volume of composite) on the flexural behavior of engineered cementitious composites (ECC) materials. Different parameters of flexural behavior such as strength at first-cracking and post-cracking stages, deflection at ultimate load, toughness indices according to ASTM 1018, flexural modulus, and energy absorption were determined. Test results showed that the flexural strength and flexural modulus of composites significantly increases by increment in fiber content. However, flexural strength of composites varies from 8.5 to 14 MPa depending on amount of PVA fibers. The toughness indices, deflection at max load and energy absorption were decreased by further increase in the fiber content from 1.6 to 2%. It was indicated that there was an indirect relationship between flexural strength and ductility of composite in higher amount of fiber content. [ABSTRACT FROM AUTHOR]

Architectural construction has experienced considerable improvements via the recent developments of colored self-consolidating mortars (C-SCM). It is significantly important to prevent strength reduction in colored mortars when aiming at specific color intensities. In this research, the effects of phthalocyanine and iron hydroxide pigments on SCM and SBR latex modified SCM (LM-SCM) were studied. The influence of using pre-milled colored paste was investigated, as well. Experiments included tests on compressive strength, compressive toughness, flexural strength and flexural toughness. It was found that incorporating SBR latex to C-SCM mix design improved flexural properties and color intensity but decreased purity and led to porosity augmentation. Results also indicated that using pre-milled colored paste considerably improved mechanical properties, color intensity and purity and decreased porosity. Preparing pre-milled colored paste was found as an effective way to use low contents of organic pigments to create brilliant, intense and uniform colors in cement-based materials. [ABSTRACT FROM AUTHOR]

Disposal of sewage sludge from waste water treatment plants is a serious environmental problem of increasing magnitude. Waste water treatment generates as much as 70 g of dry solids per capita per day. Although one of the disposal solutions for this waste is through incineration, still almost 30% of sludge solids remain as ash. This paper presents results related to reuse of sewage sludge ash in concrete. The sludge was characterised for chemical composition (X-ray flourescence analysis), crystalline phases (X-ray diffraction analysis) and pozzolanic activity. The effects of incineration on crystal phases of the dry sludge were investigated. Two water/cement (W/C) ratios (0.55 and 0.45) and three sludge ash percentages (5%, 10% and 20%) per cement mass were used as filler. The mechanical performance of sewage sludge ash concrete (SSAC) at different curing ages (3, 7, 28 and 90 days) was assessed by means of mechanical tests and capillary water absorption. Results show that sewage sludge ash leads to a reduction in density and mechanical strength and to an increase in capillary water absorption. Results also show that SSAC with 20% of sewage sludge ash and W/C = 0.45 has a 28 day compressive strength of almost 30 MPa. SSAC with a sludge ash contents of 5% and 10% has the same capillary water absorption coefficient as the control concrete; as for the concrete mixtures with 20% sludge ash content, the capillary water absorption is higher but in line with C20/25 strength class concretes performance. [ABSTRACT FROM PUBLISHER]

This article analyses the influence of acrylic fibers shape on the flexural behavior of cement composite. The fibers differ in their cross-sectional shapes due to the spinning process (wet-spun and dry-spun). The fibers were characterized by optical microscopy, and the shape factors were calculated on the basis of their geometric characteristics. Results showed that both types of acrylic fiber remarkably improved the flexural performance of the composites. Wet-spun acrylic fibers lead to high flexural strength and toughness. It was found that by increasing the fibers' shape factor by a factor of 10%, flexural strength and toughness increase to 26% and 23%, respectively. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

• Micro and nano filler containing epoxy adhesives were made for anchoring steel bar in concrete. • The mechanical/bonding properties of the adhesives to concrete base were studied. • Effect of hybrid of micro silica particles with different sizes on properties were studied. • Effect of humidity of micro silica on thermal/mechanical properties of adhesives were evaluated. In this study, effect of incorporating different sizes of silica microparticles (i.e. with mesh sizes of 100, 200, 400 and 600) and their hybrids on the properties of the epoxy composite adhesives was investigated. To determine the performance of the micro silica-based epoxy adhesives, their mechanical (i.e. the compressive, tensile and flexural) properties and adhesion to concrete and steel bar (i.e. pullout test) were evaluated. Meanwhile, the effect of surface humidity of micro silica particles on the mechanical properties of the epoxy adhesive were assessed. Hereafter, SiO2 and CaCO3 nanoparticles at 1, 3 and 5 wt% were applied to the micro silica-based composites and the mechanical and pull-out properties were determined. Results showed that moisture content were negligible in micro silica particles but it caused 7, 40 and 25% decline in the tensile modulus, flexural strength and flexural modulus of the epoxy samples compared to the samples with dried micro silica. Using micro silica particles with mesh 600 in epoxy binder caused the best performances in the epoxy composites and improved 266, 205, 60 and 102% the compressive strength, compressive modulus, tensile and flexural modulus, respectively. Hybridizing micro silica particles with different sizes had significant effect on the adhesive mechanical properties. Incorporating nano CaCO3 to the composites containing micro silica just improved compressive strength but had small impact on other properties. Finally, using nano SiO2 along with micro silica due to its incompatibility with epoxy resin caused considerable diminution in the mechanical and bonding properties especially at higher loading contents. [ABSTRACT FROM AUTHOR]