Mean Compressive Strength Research Articles

In vitro evaluation of the compressive strength of glass ionomer cement modified with propolis in different proportions

Background: Antibacterial additives are frequently added in an effort to enhance the antibacterial properties of glass ionomer cement (GIC). GIC modified with ethanolic extract of propolis (EEP) has been proven to improve GIC’s antibacterial properties, but this modification is suspected to have detrimental impacts on its compressive strength. Objectives: To evaluate the compressive strength of GIC incorporated with different proportions of propolis extracts from Trigona spp. from Garut, Indonesia. Methods: This experimental in vitro laboratory study comsisted of 20 cylindrical glass ionomer specimens divided into four groups according to the proportions of propolis added to the GIC liquid: Group A: conventional GIC (control), Group B: 25% EEP added (% w/w), Group C: 30% EEP added (% w/w), and Group D: 35% EEP added (% w/w). A universal testing machine was used to assess compressive strength after the samples were immersed in artificial saliva and incubated for 24 h. Data were analyzed with one-way analysis of variance and Tukey’s test (P < 0.05). Results: The addition of EEP decreased the compressive strength of the GIC liner. Mean compressive strength values were 118.06 ± 24.1 MPa (Group A), 103.17 ± 10.26 MPa (Group B), 79.18 ± 9.99 MPa (Group C), and 77.03 ± 6.13 MPa (Group D). In comparison to the control group, a nonsignificant difference was observed when 25% EEP was added (P > 0.05), whereas both 30% EEP and 35% EEP resulted in significant decreases in compressive strength (P < 0.05). Conclusion: GIC modified with 25% EEP might be a promising restorative material for cavity linings.

An Investigation into the Local Production Technology of Burnt Bricks in Nigeria

The acceptability of fundamental features of burnt clay bricks is a control course obtained during the production process. The applied knowledge and skills in production technology of burnt clay bricks were subjectively evaluated and quantified. Multi-method research approaches were adopted which included questionnaire instruments and experimental analysis. Assessing the source of knowledge and skill, the experience of labour and team capacity showed that most of the participants have been in the burnt brick production business for 6-10 years (37.3%) through the tutelage of their friends (72.9%) and participated in the groups of 4-5 people (25.4%). There was a deficiency in knowledge and skills needed for forming and firing stages for standard quality burnt clay brick but only effective in the extraction and preparation stage but deficient in shaping, drying, building the field kiln and firing the field kiln. The independent-sample t-test showed that the mean of the measured water absorption value of the locally produced burnt clay brick was statistically higher (mean ± SD = 29.51±0.58) than the minimum allowable standard water absorption value (mean ± SD = 20.00±0.0) significant at p = 0.00. A similar observation was made for compressive strength as the measured mean compressive strength value for the locally produced burnt clay brick was 3.98±0.30 N/mm² which was statistically higher than 3.5 N/mm². However, the dimensions of the burnt clay bricks were with the tolerance of approximately 5% for locally produced bricks. Considering the importance of good quality burnt clay bricks in construction local producers need a training.

Assessment of fire exposure on the load bearing capacity of basement storey walls

This paper presents the numerical modelling of the fire exposure on structural element and its static analysis taking account of the material properties reduction due to elevated temperature.&#x0D; The reinforced concrete wall of basement storey was subjected to one side fire exposure.&#x0D; Advanced calculation methods were used to assess the fire exposure on the structural element as most reliable and approximate to fire test results. Thermal analysis was performed with LIRA-CAD software by the simulating of three main heat-transfer ways: thermal conductivity, convection and radiation. As a result of the thermal analysis, temperature distribution in the concrete and reinforcement parts of the structural element cross-section was obtained. The thermal analysis of the wall structural element was performed for 120 minutes in standard fire exposure. Reduction factors for the strength of concrete and reinforcement steel were determined based on the temperature distribution in the wall structural element cross-section. The cross-section is divided into a number of parallel zones of equal thickness where the mean temperature and the corresponding mean compressive strength is assessed according to the Zone method procedure. The fire damaged zone of thickness az at the fire exposed sides and reduced cross-section were obtained.&#x0D; Static analysis of the wall load-bearing capa-city was performed using the procedure applicable for normal temperature design. The Deformation method for normal temperature design taking to account concrete deformation was used. The Deformation method for normal design taken to account concrete deformation at every step of iteration was used. The reduced load-bearing capacity of the fire damaged wall taking into account residual concrete strength was calculated and relevant load-bearing capacity diagrams were determined.

Comparative study of compressive strength of novel steel fiber reinforced geopolymer concrete and conventional concrete

The main aim of this study is to quantify the influence of steel fiber on the compressive strength of the geopolymer concrete. There were 2 groups taken for this study and a total of 18 samples were prepared per group. Many samples were calculated using clinical software by adopting the values from the old research papers. Different types of materials and apparatus were used during the preparation and testing of the samples. SPSS software, version 21 has been used to carry out the independent sample T-test. The mean compressive strength of geopolymer concrete with novel steel fibre sample is 32.2 N/mm2and the mean compressive strength of conventional concrete sample is 28.15 N/mm2. Independent samples t-test is performed to analyse the results. The significance(p) of the events was 0.115 (p > 0.05). It doesn't show any significant difference. The standard deviation of steel fiber reinforced geopolymer concrete was 75.73658. From this experimental study, it is concluded that the steel fiber reinforced M20 grade geopolymer concrete has a greater compressive strength than conventional concrete.

Coal Ash and Rice Husk Ash Binder for Manufacturing Hollow Blocks

This paper presents the development of a binder from coal ash and rice husk ash for manufacturing hollow blocks. Experiments were conducted to determine the compressive strength of the coal ash and rice husk ash as binders using cylindrical specimens at different curing periods. The mixture proportion with the highest compressive strength in the experiment was adopted in making the 4” hollow blocks. The compressive strength of the hollow blocks with the coal ash and rice husk ash binder was also determined at different curing periods.Cylindrical specimens with four different alkali activators were made and subjected to compression testing on the 3rd, 5th, and 7th day of curing. The mean compressive strength of the cylindrical specimen with all sodium hydroxide activator (RS0CS0) after 7 days curing is 2.54 MPa as compared to 3.05 MPa with the 2.5 sodium silicate to sodium hydroxide ratio (RS1CS0). As the amount of sodium silicate from rice husk was doubled (RS2CS0), the average compressive strength of the 7 days old cylindrical samples increased from 3.05 MPa to 3.49 MPa. Meanwhile, the 7th-day compressive strength of the cylindrical specimen with commercial silica (RS0CS1) was 5.5 Mpa.Hollow blocks were also manufactured based on the material proportion that utilizes RHA with the highest compressive strength or the design mixture RS2CS0. These blocks have a mean compressive strength of 1.22 MPa on the 3rd day, 1.88 MPa on the 7th day, and 2.7 MPa on the 14th day of the curing period.

Dynamic Mechanics and Energy Dissipation of Saturated Layered Phyllite

This paper is a study of the dynamic mechanics and energy dissipation of saturated layered phyllite. Using the Split-Hopkinson pressure bar system, the mechanical properties and energy dissipation law of the sample during dynamic loading in the test were analyzed. The results show that the weakening effect of water on the phyllite rock body will have a great impact on its mechanical properties, strain rate sensitivity damage mode, and fracture energy dissipation. The values of mechanical parameters such as the modulus of elasticity and compressive strength of the specimens in the test varied with the dip angle of the layer with 0° &gt; 90° &gt; 30° &gt; 60°, and the mechanical parameters of the specimens in the saturated state were smaller than those of the dry specimens. The damage of the sample is mainly in the form of crushing damage at 0° dip angle, shear damage along the laminar surface at 30° and 60°, and destabilization damage of the compression bar at 90° dip angle, with higher fragmentation of the sample in the saturated state. The energy dissipation densities of different inclination samples in the saturated state of schist are greater than those in the dry state, with the highest energy dissipation density in the 0° inclination sample and the lowest in the 90° inclination sample. Both the mean strain rate and compressive strength of the samples showed a multiplicative power relationship with the crushing energy dissipation density of the samples, showing a strong strain rate correlation. These results indicate that the use of rock crushing energy dissipation density can better reflect the strength characteristics of phyllite samples under dynamic loading.

The controlled release, bioactivity and osteogenic gene expression of Quercetin-loaded gelatin/tragacanth/ nano-hydroxyapatite bone tissue engineering scaffold

In this study, a Gelatin/Tragacanth/Nano-hydroxyapatite scaffold was fabricated via freeze-drying method. A highly porous scaffold with an average pore diameter of 142 µm and porosity of 86% was found by the micro-computed tomography. The mean compressive strength of the scaffold was about 1.5 MPa, a value in the range of the spongy bone. The scaffold lost 10 wt.% of its initial weight after 28 days soaking in PBS that shows a fair degradation rate for a bone tissue engineering scaffold. Apatite formation ability of the scaffold was confirmed via scanning electron microscopy, X-ray diffraction and Fourier transforming infrared spectroscopy, after 28 days soaking in simulated body fluid. The scaffold was able to deliver 93% of the loaded drug, Quercetin, during 120 h in phosphate-buffered solution, in a sustainable manner. The MTT assay using human bone mesenchymal stem cells showed 84% cell viability of the Quercetin-loaded scaffold. The expression of the osteogenic genes including Col I, Runx-2, BGLAP (gene of osteocalcin), bFGF, SP7 (gene of osterix) and SPP1 (gene of osteopontin) were all upregulated when Quercetin was loaded on the scaffold, which indicates the synergetic effect of the drug and the scaffold.

Biocomponents Based on Hydroxiapatite: Influence of Sterilization on the Mechanical Resistance.

Objective This study aimed to evaluate the influence of sterilization on the compressive and flexural mechanical strength of hydroxyapatite-based biocomponents obtained through freeze-dried bovine bone, and its association with chitosan. Methods Freeze-dried bovine bone was processed into 100 μm particles and mixed with 50% of its weight in chitosan. The mixture was packed in metallic molds for preparing the specimens, and sterilized at 127°C using an autoclave for subsequent experimentation. The specimens were subjected to compression and flexion tests following norm 5833 of the International Organization for Standardization (ISO), with 6 × 12 mm cylindrical blocks (for compression tests) and 75 × 10 × 3.3 mm plates (for flexion tests) as samples. The samples were divided into four groups of 20 specimens each, with 10 for compression and 10 for flexion tests. Three groups were sterilized (autoclave, gamma rays, and ethylene oxide), whereas the fourth group (control) was not. The mechanical tests obtained from the different sterilization processes were compared using analysis of variance (ANOVA, p < 0.05), followed by the Tukey multiple comparison test of means, with a 95% confidence interval. Results The specimens presented mean compressive strengths of 10.25 MPa for the control group and 3.67 MPa, 9.65 MPa, and 9.16 MPa after ethylene oxide, gamma ray, and autoclave sterilization, respectively. Flexion test results showed an average resistance of 0.40 MPa in the control group, and 0.15 MPa, 0.17 MPa, and 0.30 MPa after ethylene oxide, gamma ray, and autoclave sterilization, respectively. There were statistically significant differences observed in the maximum compression of the ethylene oxide-sterilized group compared with that of the control group ( p = 0 . 0002), gamma ray-sterilized ( p = 0.0003), and the autoclaved ( p = 0.0006) groups. There was a statistically significant difference in maximum flexion of the specimens sterilized by gamma rays when compared with the control group ( p = 0.0245). However, low flexural strengths were observed in all specimens. Conclusion The autoclave sterilization group did not result in statistically significant differences in either compression or flexion strength tests. Thus, the autoclave proved to be the best sterilization option for the hydroxyapatite-based biocomponents in this study.

Compressive Strength Of Fiber Reinforced Composite After Immersion In Citric Acid Of Energy Drink

Background: Energy drink consumption has been popular in people age 18-35 years old. A few literature showed that this drink can cause damage to teeth and composite due to its acidity. The use of fiber reinforced composite has been increasing due to its good mechanical properties and aesthetic. Fiber reinforced composite has fiber shaped fillers that can withstand mastication forces. A restoration material has to face the complex oral environment to succeed clinically. Compressive strength test is needed to predict the durability of restoration materials against mastication forces. Purpose: To determine the effect of energy drink citric acid immersion to fiber reinforced composite compressive strength. Methods: 32 cylinder shaped fiber reinforced composite samples with 8mm tall and 4mm diameter were divided into two groups. The first group was immerse in distilled water (K1) as control, and the second group (K2) was immerse in energy drink citric acid. The samples were immersed in an incubator at ±37⁰C for 7 days. After 7 days, samples were washed in water, dried with tissue, and then undergo compressive strength test with Autograph machine at crosshead speed of 10mm/minute. The data were then analyzed using Independent t-test. Results: The mean compressive strength of K1 group was 1469.63 MPa and K2 group 1439.57 MPa. The mean value of K2 group was slightly lower than K1 group, but statistically, there was no significant difference between the 2 groups. Conclusion: Energy drink citric acid immersion has no effect on fiber reinforced composite compressive strength.

COMPARATIVE EVALUATION OF COMPRESSIVE STRENGTH OF CENTION N AND TYPE IX GLASS IONOMER CEMENT – AN INVITRO STUDY

BACKGROUND: This study aimed to compare the compressive strength of glass-ionomer cement (GIC) Type IX and Cention N. METHODS: Five samples each of GIC Type IX and Cention N were prepared for testing the compressive strength. Cylinders of the samples measuring 1 cm diameter and 6 mm height were prepared for compressive strength. Testing was done by mounting the samples in a universal testing machine with a crosshead speed of 1 mm/min. RESULTS: The mean compressive strength of Type IX GIC (n=10) was 94.010 with standard deviation ±15.654 while the mean compressive strength of Cention V (n=10) was 125.567 with standard deviation ± 7.890. The values of the compressive strength Cention N were statistically significant (P &lt; 0.5) as compared to GIC Type IX. CONCLUSION: The results suggest significantly higher values for mechanical properties of Cention N as compared to GIC Type IX.

Comparison and Advanced Antimicrobial Strategies of Silver and Copper Nanodrug-Loaded Glass Ionomer Cement against Dental Caries Microbes.

Caries lesions during cement repairs are a severe issue, and developing a unique antimicrobial restorative biomaterial can help to reduce necrotic lesion recurrence. As a result, Thymus vulgaris extract was used to biosynthesize copper nanoparticles (TVE-CuNPs) exhibiting different characteristics (TVE). Along with TVE-CuNPs, commercial silver nanoparticles (AgNPs) and metronidazole were combined with glass ionomer cement (GIC) to test its antibacterial efficacy and compressive strength. FTIR, XRD, UV-Vis spectrophotometry, and TEM were applied to characterize the TVE-CuNPs. Additionally, AgNPs and TVE-CuNPs were also combined with metronidazole and GIC. The modified GIC samples were divided into six groups, where groups 1 and 2 included conventional GIC and GIC with 1.5% metromidazole, respectively; group 3 had GIC with 0.5% TVE-CuNPs, while group 4 had 0.5% TVE-CuNPs with metronidazole in 1.5%; group 5 had GIC with 0.5% AgNPs, and group 6 had 0.5% AgNPs with metronidazole at 1.5%. An antimicrobial test was performed against Staphylococcus aureus (S. aureus) and Streptococcus mutans (S. mutans) by the disc diffusion method and the modified direct contact test (MDCT). GIC groups 4 and 6 demonstrated a greater antimicrobial efficiency against the two tested strains than the other groups. In GIC groups 4 and 6, the combination of GIC with two antimicrobial agents, 1.5% metronidazole and 0.5% TVE-CuNPs or AgNPs, enhanced the antimicrobial efficiency when compared to that of the other groups with or without a single agent. GIC group specimens combined with nanosilver and nanocopper had similar mean compressive strengths when compared to the other GIC groups. Finally, the better antimicrobial efficacy of GIC boosted by metronidazole and the tested nanoparticles against the tested strains may be relevant for the future creation of more efficient and modified restorations to reduce dental caries lesions.

Comparative evaluation of compressive strength of three different core build up materials on fiber reinforced composite post after 24 hours and 1 week- an in vitro UTM study

Background: A core build-up is a restoration placed in a badly broken down tooth to restore the coronal portion of the tooth. This facilitates subsequent restoration of the broken down tooth by means of extra-coronal restoration. Compressive strength of core materials is thought to be important because core usually replaces the large bulk of the tooth structure and must resist multidirectional forces. In this study compressive strength of three different core materials was investigated on Fiber Reinforced Composite post at different time intervals. Objective: The purpose of the study undertaken was to determine the compressive strength of self-cured, photo cured and dual cured core build up materials on Fiber Reinforced Composite post after 24 hours and 1 week. Methodology: Cylindrical specimens measuring 6mm in height and 4mm in diameter were prepared using a machined plexiglass mold and core build up was done around the fiber post. Ten specimens were prepared in each group (n=30); Group A: Restorative Glass lonomer Cement-GC Gold, Japan; Group B: Light-cured composite-Magma NT, Prevest Denpro, USA and Group C: Dual-cure core-build up composite resin-Para Core, Coltene whaledent, USA, which were further subdivided into five specimens per group according to the time intervals of 24 hours and 1 week. Compressive strength was determined using a universal testing machine. The maximum load applied to fracture the specimens was recorded and compressive strength calculated in MPA. The data obtained was analyzed using parametric one way ANOVA test and Bonferroni post-hoc procedure. Results: The mean compressive strength was significantly higher (p

Experimental and Numerical Mechanical Characterization of Unreinforced and Reinforced Masonry Elements with Weak Air Lime Mortar Joints

This paper deals with the results of an experimental and numerical campaign aimed at characterizing the mechanical response of masonry components and panels made of limestone units kept together by weak air lime mortar joints. The selected air lime mortar, typical of ancient masonry buildings but difficult to be built-up artificially, was specifically prepared for the experimental analyses, with the aim of obtaining a laboratory compression strength of 0.25–0.50 MPa. In the first part of the paper, the performed tests concerning the strength of the units (mean compression strength of 80 MPa) and of the mortar (mean compression strength after 28 days of 0.30 MPa), are described for different curing periods. Moreover, tests of masonry triplets in shear (shear strength of 0.11 MPa for null axial forces) are shown and used in order to establish the main parameters of the Mohr–Coulomb failure criterium. Then, the calibration of a continuous numerical micro-model implemented in Kratos Multiphysics is presented. The model is used for reproducing the behavior of an unreinforced panel in shear made of the studied masonry and to appraise the effectiveness of a FRCM- (Fiber Reinforced Cementitious Matrix) based reinforcement intervention applied. The obtained results proved that FRCM allows to increase the strength of the considered masonry type by about eight times and the ductility by about thirteen times.

Effect of Fine Aggregate Sources on Compressive Strength of Cement Concrete

The cause of failure of structure made from cement concrete is due to use of low-quality ingredient which is used directly without testing its properties and without studying its suitability in production of different grade of concrete mix. The aim of this study is to presents that the effect of fine aggregates from different sources on compressive strength of cement concrete. For this study four fine aggregate sources were taken. Altogether 48 concrete cubes of M20 grade were prepared from different sixteen combinations of these four fine aggregate sources. The different properties were founded by conducting different laboratory tests for fine aggregates from different sources and the compressive strength test of 48 cubes was conducted.The test results showed that properties of fine aggregate sources such as fineness modulus, loose bulk density, specific gravity, water absorption and Materials Finer than 75 μm were founded in the range of (3.17-3.88), (1508.33-1604.17) kg/m3, (2.57-2.66) %, (1.60-1.92) % and (2.74-7.47) respectively. Compressive strength test of all 48 samples were cross the minimum strength provided by M20 grade and it is ranges from 20.64 N/ mm2 to 32.47 N/ mm2. Different value of mean compressive strength was obtained for all sixteen combinations of aggregates form each other. The fine aggregate from Chisang source achieved more value of average compressive strength when mix with other four different coarse aggregate sample than other three sources. Significance difference in mean compressive strength of concrete made from different fine aggregates source was concluded by the Two-way ANOVA test results. This research work concluded that all four fine aggregate sources used in this study and concrete made from these sources can be used for residential building construction propose and other construction work which required strength provided by M20 grade of nominal mix concrete.

Synthesis and characterization of ionomer-type cements from alkaline-activated kaolinite

The objective was to synthesize ionomer-type cements from alkaline-activated kaolinite and describe their setting characteristics, compressive strength and fluoride ion releasing properties. Aluminosilicate phases were visible on XRD spectra with minimal difference between raw and alkaline-activated kaolin. D50 range of sieved powders was 8.10–9.07 μm. Characteristic bands of polyacrylates and tartrates were identifiable in the cements on FTIR. Cements were hydrolytically stable with mixing and setting times of 60s and 135–240 s, respectively. Mean compressive strength increased over time, highest value 3.24 MPa recorded for Kaolin100 after 28 days, and significantly different within the group (F = 76.64, p = 0.000). Cement containing fly ash (FA) exhibited fluoride ion release capabilities with Kaolin80FA20 having the highest 0.69 mmol/L at 60 min. Mechanically weak but hydrolytically stable ionomer cements can be formulated from alkaline-activated kaolin geopolymers. • Alkaline-activated kaolinite reacted with poly (acrylic) and tartaric acids. • The reaction produced hydrolytically stable ionomer-type cements. • The compressive strength increased over time but did not exceed 5 MPa after 28 days. • Addition of fly ash resulted in diffusion-controlled fluoride release.

Antimicrobial Efficacy of Glass Ionomer Cement in Incorporation with Biogenic Zingiber officinale Capped Silver-Nanobiotic, Chlorhexidine Diacetate and Lyophilized Miswak.

In the present study, Zingiber officinale is used for the synthesis of Zingiber officinale capped silver nanoparticles (ZOE-AgNPs) and compares the antimicrobial efficacy and compressive strength of conventional glass ionomer cement (GIC) combined with ZOE-AgNPs, lyophilized miswak, and chlorhexidine diacetate (CHX) against oral microbes. Five groups of the disc-shaped GIC specimens were prepared. Group A: lyophilized miswak and GIC combination, Group B: ZOE-AgNPs and GIC combinations, Group C: CHX and GIC combination, Group D: ZOE-AgNPs + CHX + GIC; Group E: Conventional GIC. Results confirmed the successful formation of ZOE-AgNPs that was monitored by UV-Vis sharp absorption spectra at 415 nm. The X-ray diffractometer (XRD) and transmission electron microscope (TEM) results revealed the formation of ZOE-AgNPs with a mean size 10.5–14.12 nm. The peaks of the Fourier transform infrared spectroscopy (FTIR) were appearing the involvement of ZOE components onto the surface of ZOE-AgNPs which played as bioreducing, and stabilizing agents. At a 24-h, one-week and three-week intervals, Group D showed the significantly highest mean inhibitory zones compared to Group A, Group B, and Group C. At microbe-level comparison, Streptococcus mutans and Staphylococcus aureus were inhibited significantly by all the specimens tested except group E when compared to Candida albicans. Group D specimens showed slightly higher (45.8 ± 5.4) mean compressive strength in comparison with other groups. The combination of GIC with ZOE-AgNPs and chlorhexidine together enhanced its antimicrobial efficacy and compressive strength compared to GIC with ZOE-AgNPs or lyophilized miswak or chlorhexidine combination alone. The present study revealed that The combination of GIC with active components of ZOE-AgNPs and chlorhexidine paves the way to lead its effective nano-dental materials applications.

Comparative Evaluation of Compressive Strength and Flexural Strength of GC Gold Hybrid, GIC Conventional and Resin-modified Glass-ionomer Cement.

Purpose:The aim of the study was to emphasize the compressive strength and flexural strength of glass-ionomer cement (GIC)–gold hybrid, conventional GIC, and resin-modified GIC (RMGIC).Methodology:Three GIC materials were used in the study: group A: GC–gold hybrid (Gold Label hybrid Universal Restorative), group B: type II conventional GIC, and group C: RMGIC. A total of 120 cylindrical test specimens of dimensions 4 mm diameter × 6 mm height were prepared from a custom-made Teflon mold according to respective study groups. The specimens prepared were then stored in 20 mL of deionized water at 37°C for 3 h daily for 30 days, and the solutions were changed every week, after which they were tested for compressive strength and flexural strength by using a universal force testing machine. All the results were analyzed by SPSS software and were subjected to statistical analysis using ANOVA followed by the Bonferroni post-hoc test.Results:The mean compressive strength was the highest for group A and lowest for group B. Similarly, the mean flexural strength was the highest for group A and lowest for group B.Conclusion:The conclusions can be drawn from this in-vitro study that the compressive strength and flexural strength of GC–gold hybrid were greater than those of RMGIC and conventional GIC.

Comparative evaluation of bioactivity, fluoride release, shear bond strength, and compressive strength of conventional glass ionomer cement incorporated with three inorganic bioactive nanoparticles: An experimental analysis.

Over the course of four decades, the bioactive materials have changed. They have become more specialized, more manageable, possessing superior qualities. Thus, it should be encouraged to conduct ongoing research to improve these materials even further in order to meet the growing clinical and restorative needs. To evaluate and compare bioactivity, fluoride release, shear bond strength and compressive strength of conventional GIC incorporated with three inorganic bioactive nanoparticles. For the study, total of 160 samples were included. The samples were divided in four groups (40 samples per group) i.e. 3 wt% of forsterite (Mg2SiO4) (Group 2), wollastonite (CaSiO3) (Group 3) and niobium pentoxide (Nb2O5) (Group 4) nanoparticles incorporated into GIC (Group 1). The bioactivity (FEG-SEM and EDX analysis), fluoride release (ion-selective electrode), shear bond strength testing (UTM followed by evaluation under stereomicroscope) and the compressive strength (UTM) was checked for each group. Wollastonite nanoparticles (3wt %) incorporated to GIC showed maximum increase in the apatite crystal formation,Ca and P content and highest fluoride release. Mean shear bond strength was highest in niobium pentoxide nanoparticles (3wt %) incorporated to GIC while mean compressive strength was highest in forsterite nanoparticles (3wt %) added to GIC. Positive results were observed which showed increase in the bioactivity alongwith enhancement of the fluoride release, shear bond strength and compressive strength but further research on these materials is warranted before its use in clinical practice.

Statistical Characteristics of compressive strength of Normal &amp; High strength concrete and concrete made with recycled aggregate

The paper presents the statistical analysis on the compressive strength of concrete with strength ranging from 30 MPa to 130 MPa. To obtain these concrete strengths, concrete mixes with virgin aggregates were prepared with four different wate r to cementitious content (w/c) ratios i.e., 0.45, 0.36, 0.24, and 0.18. With w/c ratio of 0.45, a mix is also designed using recycled construction and demolition coarse aggregate to compare statistical characteristics with respect to concrete made using virgin aggregates. The presented statistical analysis includes measure of central tendency, dispersion of the data, distribution shape properties, and precision of the mean. A normal and a log-normal distribution has been established and validated for the experimental data set of all the mixes. A correlation has also been established for the compressive strength of 100mm cube and 150mm cube. Analysis shows an increase in dispersion of data with increase in the mean compressive strength of the mix. The mix with Construction and demolition waste aggregate shows a higher standard deviation than the mix with virgin aggregates at the same w/c ratio. The correlation curve for the compressive strength of 100 mm and 150 mm size cubes, shows a conversion factor of 1.04, suggesting an insignificant difference of the compressive strength values of 100 mm and 150 mm cubes for the mix studied.

Experimental study on flexural behavior of rebar concrete beams in industrial building exceeding 50 years

The flexural performance of six rebar-concrete beams from an industrial plant over 50 years in Northwest China is investigated. Firstly, the concrete cores are tested for carbonation depth and compressive strength. Moreover, the rebars extracted from crushing process are tested for yield, ultimate strength and ductility. Secondly, exceeding 50 years rebar-concrete beams are tested by three-point loading for flexural ultimate capacity, deflection and crack evolution process. The results show that sectional carbonization occurs in concrete, which is related to position, and the maximum reduction of mean compressive strength is 16.88%. Tensile yield, ultimate strength and plastic deformation capacity of rebar decrease. In addition, the new crack load and ultimate flexural capacity of specimen beams are reduced, and cracks and deflection develop rapidly. Finally, a comparison of experimental values and three previous models shows that calculated values of existing models are lower than experimental values, which is relatively conservative evaluation.