Does Multi-Fiber-Reinforced Composite-Post Influence the Filling Ability and the Bond Strength in Root Canal?

The purpose of the present in vitro study was to investigate the bond strength of root canal dentin and the filling ability of a new multi-fiber-reinforced composite post (mFRC) compared to a conventional single fiber-reinforced-composite post (sFRC). Twenty-eight freshly maxillary first permanent single-rooted premolars were instrumented and divided into groups (n = 14). Group 1: single-fiber-reinforced composite (sFRC), group 2: multi-fiber-reinforced composite (mFRC). Bonding procedures were performed using a dual-cure universal adhesive system and resin cement. All specimens were sectioned so that seven discs of 1 mm of thickness were obtained from each root. An optical microscope was used before the push-out test to measure the total area of the voids and to determine the length of the smaller/bigger circumferences. The push-out bond strength (PBS) test was performed using an Instron universal testing machine. Data were then compared by one-way ANOVA on ranks (α = 0.05). The dentin–cement–post interface was observed using scanning electron microscopy (SEM). At the coronal third, a significantly higher bond strength (p < 0.05) was obtained in the sFRC group (44.7 ± 13.1 MPa) compared to the mFRC group (37.2 ± 9.2 MPa). No significant difference was detected between the groups at the middle third (sFRC group “33.7 ± 12.5 MPa” and mFRC group “32.6 ± 12.4 MPa”) (p > 0.05). Voids were significantly lower in the mFRC compared to those observed in the sFRC group (p < 0.05) at the coronal third. Whereas, no significant difference was found at the middle third (p > 0.05) between the tested groups. Filling ability was overall improved when employing mFRC, although such technique might have characteristic limitations concerning the bond strength to dentin.

Effects of Induction-Furnace Slag on Strength Properties of Self-Compacting Concrete

Indiscriminate waste disposal poses a severe environmental challenge globally. Recycling of industrial wastes for concrete production is currently the utmost effective way of managing wastes for a cleaner environment and sustainable products. This study investigates the strength characteristics of self-compacting concrete (SCC) containing induction furnace slag (IFS) as a supplementary cementitious material (SCM). The materials utilized include 42.5R Portland cement, induction furnace slag as an SCM ranging from 0 to 50 % by cement weight at 10 % interval, river sand, granite, water and superplasticizer. The fresh properties were tested for filling ability, passing ability and segregation resistance, the strength characteristics measured include compressive strength, splitting tensile strength, flexural strength and Schmidt/rebound number. The oxide compositions and microstructural analysis of SCC were investigated using x-ray fluorescence analyser (XRF) and scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy (SEM-EDS), respectively. Empirical correlations were statistically analyzed using MS-Excel tool. The filling ability characteristic was determined via both the slump flow test and the T50cm slump flow time test. Moreover, the passing ability characteristic was determined using L-Box test. The segregation resistance characteristic was determined using V-funnel at T5minutes test. The results of the fresh properties showed a reduction in the slump flow with increasing IFS content. On the other hand, the T50cm slump flow increased with increasing IFS content. Furthermore, the L-Box decreased with higher IFS content. On the contrary, the V-funnel at T5minutes increased considerably with greater IFS content. The strength test results revealed that the strength properties increased to 20 % IFS, with a value of 66.79 N/mm2 compressive strength at 56 days, giving a rise of 12.61 % over the control. The SCC microstructural examinations revealed the amorphous and better interface structures with increasing IFS content in the mix. The empirical correlations revealed that linear relationships exist among the measured responses (fresh and strength properties). Ultimately, IFS could be utilized as a sustainable material in producing self-compacting concrete.

Research on Pressure Loss and Filling Ability of Semi-Solid Rheological Behavior in Squeeze Casting

The filling ability of alloy fluid under pressure is of great significance to improve the dimensional integrity and mechanical properties of thin-walled and slender rods formed by squeeze casting. Insight into the rheological behavior of squeeze casting is beneficial to improve the formability of complex structural parts by optimizing the squeeze casting process. In this work, the Archimedes spiral sample prepared by indirect squeeze casting was applied to investigate the variation of filling length with squeeze pressure and filling speed during the rheological process in squeeze casting. According to the temperature distribution characteristic during the alloy melt filling process, the alloy fluid state was discussed and the spiral filling was confirmed as a semi-solid rheological behavior. The calculation models of pressure loss and filling length were established respectively based on steady-state rheological behavior. Pressure loss is mainly affected by the melt viscosity which is determined by temperature distribution and filling speed of alloy melt in the channel. According to the agreement between the theoretical calculations and the experimental results, the pressure loss and filling length models have been confirmed to be used to quantitatively characterize the filling ability of the aluminum alloy melt in the squeeze casting process.

Study on Adaptability of Test Methods for Workability of Fresh Self-Compacting SFRC

To ensure the quality of concrete construction, the workability of fresh mix measured by rational test methods is critical to be controlled. With the presence of steel fibers, whether the test methods and evaluation indices of fresh self-compacting concrete (SCC) are adaptable for self-compacting steel fiber reinforced concrete (SFRC) needs to be systematically verified. In this paper, seven groups of self-compacting SFRC, referenced with one group SCC, were prepared by using the mix proportion design method based on the steel fiber-aggregates skeleton packing test. The main factors included the volume fraction and the length of hooked-end steel fiber. Tests for filling ability, passing ability, and stability of fresh self-compacting SFRC and SCC were carried out. Results indicate that the adaptability was well for the slump-flow test with indices of slump flow and flow time T500 to evaluate the filling ability, the J-ring flow test with an index of PA level to evaluate the passing ability, and the static segregation test with an index of static segregation resistance to evaluate the stability of fresh self-compacting SFRC. By the repeated tests and measurements, the slump cone should be vertically lifted off to a height of 300 mm within 3 s at a constant speed, the spacing of the rebar in the J-ring test should be adjusted to be two times the fiber length. If the table jumping test is used, the dynamic segregation percent should be increased to 35% to fit the result of the static segregation test. Good workability of the self-compacting SFRC prepared in this study is presented with the general evaluation of test results.

Self-Compacting Concrete Properties of Recycled Coarse Aggregate

Self-compacting concrete, which is characterized by its capacity to flow, can also consolidate under its weight. Hardened concrete from concrete building demolition can be used to partially replace natural coarse aggregate in self-compacting concrete. The current study compares the properties of self-compacting concrete with 0 percent, 25%, 50%, 75%, and 100% substitution of recycled coarse aggregate in the fresh and hardened states. The evolution of passing ability properties using the L-box test, filling ability properties using the slump cone test, and segregation properties using the V-funnel test are also included. Compression, tension, and flexural strength are all checked for hardened properties. Rapid chloride permeability and sorptivity tests are used to assess durability. The experimental program revealed that at RCA utilization levels of 25% to 50%, little to no negative impact on power, workability, or durability properties was observed.

Utilization of Iron Filings as Partial Replacements for Sand in Self-Compacting Concrete

The use of industrial by-products in concrete production is part of concerted efforts on the reduction of environmental hazards attributed to the mining of conventional aggregates. Consideration of iron filings (IF), a by-product from steel production process, is an environmentally friendly way of its disposal which is expected to yield economic concrete production. Six self-compacting concrete (SCC) mixes were made by partially substituting river sand with IF at 5%, 10%, 15%, and 20% and the mix without IF (0% IF) served as the control. The water-binder (w/b) ratio of 0.45 was adopted for all mixes. The fresh state properties of SCC evaluated include: filling ability determined using slump flow and T500 mm slump flow tests, passing ability determined using L-box test and segregation resistance determined using V-funnel tests. The strength properties of SCC considered were compressive and tensile strengths. All the SCC mixes met the fresh properties requirements for filling capacity, passing ability, and segregation resistance. The 28-day compressive and tensile strengths of SCC increased by 3.46% and 8.08%, respectively, with IF replacement up to 15% compared to the control SCC. However, there was reduction in compressive and tensile strengths of SCC with IF replacement beyond 15%. The strength properties of SCC is considerably enhanced with the addition of up to 15% IF. Hence, the optimum content of 15% IF is considered suitable as a replacement for river sand in SCC. Keywords: Self-compacting concrete; iron filings; fine aggregates; filling ability; passing ability

Flow Characteristics of Recycled Coarse Aggregates (RCA) based Self-Compacted Concrete (SCC)

The desire of humans increasing day by day to build new and high quality structures and to demolish the old structures. The demolished concrete is supplies to direct land fills and provides serious risk to the environment. In recent years, using recycled aggregates (RCA) as a substitute for natural aggregates in concrete has become of great interest to researchers. In meantime the use of RCA becomes sustainable and environmental friendly. The application of concrete in slabs, beams, columns specially areas of congested reinforcement requires high degree of compaction that is impossible to achieve at the site. For this purpose the self-compacted concrete (SCC) is the better solution. SCC is one that can flow under its own weight and fill the formwork completely without any need of compaction or vibration efforts. In this regards this experimental study has undertaken to investigate the flow behaviour of RCA based SCC. The natural crushed coarse aggregates were replaced by RCA at 0%, 20%, 40%, 60%, 80% and 100%. The fresh properties were evaluated through filling ability, passing ability and segregation resistance tests. The results revealed that all the fresh properties of RCA based SCC is depends on the percentage of RCA. As percentage of RCA increases the workability of concrete decreases. The workability is adjusted by increasing the suitable dosage of SP. Furthermore, it is also noted that all the values of freshproperties lie within the required limits of EFNARC.

Effect of corrosion on the bond strength of self consolidated lightweight concrete

Self-consolidating lightweight concrete (SCLWC) is a concrete with excellent filling ability, good passing ability, and adequate segregation resistance. The use of SCLWC can be beneficial for structures due to significant reduction in dead loads as well as structures in seismic zone. In addition, economic impacts on construction industry by using SCLWC will be significant because of its benefits. Three SCLWC mixtures are developed by using two types of lightweight aggregates (LWA) (such as blast furnace slag and expanded shale), two supplementary cementing materials (such as fly ash and metakaolin). In addition to fresh and strength properties, the effect of different degrees of accelerated corrosion on bond characterists of deformed steel bars in SCLWC is investigated by analyzing pullout test results such as load-slip relationship, voltage versus time data, failure modes, aggregate of specimens and concrete material characteristics.

Effect of corrosion on the bond strength of self consolidated lightweight concrete

Self-consolidating lightweight concrete (SCLWC) is a concrete with excellent filling ability, good passing ability, and adequate segregation resistance. The use of SCLWC can be beneficial for structures due to significant reduction in dead loads as well as structures in seismic zone. In addition, economic impacts on construction industry by using SCLWC will be significant because of its benefits. Three SCLWC mixtures are developed by using two types of lightweight aggregates (LWA) (such as blast furnace slag and expanded shale), two supplementary cementing materials (such as fly ash and metakaolin). In addition to fresh and strength properties, the effect of different degrees of accelerated corrosion on bond characterists of deformed steel bars in SCLWC is investigated by analyzing pullout test results such as load-slip relationship, voltage versus time data, failure modes, aggregate of specimens and concrete material characteristics.

Durability Indicators for Sustainable Self-Consolidating High-Strength Concrete Incorporating Palm Oil Fuel Ash

This paper presents the durability indicators for sustainable self-consolidating high-strength concrete (SCHSC) including palm oil fuel ash (POFA) as a supplementary cementing material (SCM). SCHSC mixes were prepared by varying the water to binder (W/B) ratio and POFA content. The W/B ratio was varied in the range of 0.25 to 0.40, and the POFA content differed in the range of 10–30% to produce the desired SCHSC mixes. The tests conducted on the freshly mixed SCHSCs to evaluate their filling ability, passing ability, and segregation resistance were slump flow, J-ring flow, and sieve segregation, respectively. To evaluate the durability of the hardened SCHSCs, the compressive strength, water absorption, and permeable porosity were examined along with the ultrasonic pulse velocity (UPV). The correlations between different hardened properties were derived to ascertain the durability indicators for sustainable SCHSCs. It was observed that most of the SCHSCs possessed excellent filling ability and passing ability with adequate segregation resistance. The test results also revealed that the compressive strength and UPV increased, whereas the water absorption and permeable porosity decreased with a lower W/B ratio and a higher amount of POFA (up to 20% weight content). Moreover, strong correlations were found between the different hardened properties of SCHSC. These correlations were used to determine the durability indicators for sustainable SCHSC with respect to compressive strength, permeable porosity, and water absorption. In accordance with the derived durability indicators, the sustainable SCHSC mixes produced in this study had the durability levels varying from “high” to “outstanding”.