Decrease In Setting Time Research Articles

Analysis of Different Early Strength Agents on the Performance of Prefabricated UHPC.

Precast ultra-high-performance concrete (UHPC) has emerged as indispensable in the engineering sector due to its cost-effectiveness and superior performance. Currently, precast UHPC grapples with challenges pertaining to slow setting times and insufficient early strength, largely attributed to its high water-reducing agent content. Effective utilization of early strength agents to augment UHPC's early strength is pivotal in addressing this issue. This study investigates the efficacy of two distinct concrete early strength agents, namely calcium formate (Ca(HCO2)2) and aluminum sulfate (Al2(SO4)3). A UHPC system with a water/cement ratio of 0.17 was used; both single and compound doping experiments were conducted using varied dosages of the aforementioned early strength agents. Our results show that both early strength agents significantly reduce setting time and enhance early strength at appropriate dosages. Specifically, the addition of 0.3% Ca(HCO2)2 led to a 33.07% decrease in setting time for UHPC. Moreover, the incorporation of 0.3% Ca(HCO2)2 and 0.5% Al2(SO4)3 resulted in a strength of 81.9 MPa at 1.5 days, representing a remarkable increase of 118.4%. It is noteworthy that excessive use of Ca(HCO2)2 inhibits the hydration process, whereas an abundance of Al2(SO4)3 diminishes the early strength effect. Simultaneously, this article provides recommendations regarding the dosage of two distinct early strength agents, offering a novel solution for expediting the production of prefabricated UHPC with a low water/cement ratio and high water-reducing agent content.

Implementasi Metode Single Minute Exchange of Dies Untuk Optimasi Setting Time Mesin Flexo B1 Grup C Pada Carton Box Departement PT. A

PT. A is a company engaged in the production and sale of paper, cardboard boxes, and other similar products in Indonesia. The products it offers include paper, tissue, packaging, and other products. The Carton Box Department, from the results of observations made, the average actual setting time on the Flexo B1 Group C machine is 47 minutes/order, this is one of the weaknesses that causes a 32-minute gap from the target set by the company which is 15 minutes/order. The research objectives are to analyze, improve, and obtain improved setting time results on the Flexo B1 Group C machine and the production process time carried out. The SMED (Single Minute Exchange of Dies) method is one approach that can be pursued in improving setting time. The influence of the SMED (Single Minute Exchange of Dies) method in optimizing the setting time of the Flexo B1 Group C machine results in a decrease in setting time with a setup duration of 49.11 minutes, normal time of 59 minutes, and standard time 66 minutes to a setup duration 25.36 minutes, normal time 27 minutes and standard time 34 minutes and the percentage obtained is 51.8%. Keywords: Lean Manufacturing, Productivity, Single Minute Exchange of Dies

Drying shrinkage characteristics and mechanism primary exploration of MgO-slag mortars

In this work, seven groups of MgO-slag mortars and pastes were prepared with different MgO types and MgO contents. The setting time, compressive strength and drying shrinkage were characterized. The mechanism of drying shrinkage was discussed by means of microscopic test XRD, FT-IR, MIP and SEM-EDS. The results show that the setting time decrease with the increase of MgO activities and contents. The high-activity MgO only shows a higher compressive strength advantage in the early stage, and the higher content of S-MgO, the higher the compressive strength advantage in the later stage. The 120d drying shrinkage first increases and then decreases with the increase of S-MgO contents, and the maximum drying shrinkage is obtained when the S-MgO content is 15%. The drying shrinkage of the mortar mixed with M-MgO is about half of the mortar mixed with S-MgO; the mortar mixed with R-MgO shows expansion change. Intraparticle porosity, interparticle porosity, and MgO particle size are important factors that affect the drying shrinkage of MgO-slag mortars. This study will provide the theoretical basis for the preparation of cementing materials with no length change by using a MgO activator.

Effect of different manipulations on the physical, chemical and microstructural characteristics of Biodentine

ObjectiveThe water to powder ratio and method of mixing is important for the properties of hydraulic cements. For this purpose a number of clinicians prefer premixed materials. Dental manufacturing companies provide predosed materials, however the manufacturer instructions are not always adhered to. The aim of this research is to investigate physical and chemical alterations of the tricalcium silicate‐based cement Biodentine when manipulated according to the manufacturer’s instructions (control) or changing the doses and mixing of the material components. Methods6 groups were constituted according to different mixing and dosing of powder and liquid. The hydrated cements were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Calcium ion concentration of the leachate was also investigated. Assessment of the physical characteristics included setting time and microhardness. ResultsMicrostructural differences were visible only in the Biodentine mixed manually with water, in which early hydration rate was also affected, with lower calcium ion release. Increase of Biodentine liquid increased the calcium ion release, but also increased the setting time. Manual manipulation required more liquid (both water and Biodentine liquid) added to the mixture to guarantee a similar consistency to the control. A decrease in setting time was also noted. All groups showed higher values of microhardness at 24 h compared to the freshly set materials. In the freshly set materials, there was an overall decrease in microhardness in all groups when compared to group control, particularly significant when increasing the dosage of Biodentine liquid. SignificanceWhen mixing Biodentine, altering the mixing procedure in terms of type and amount of liquid added to the powder and mixing device chosen has an effect on the physical, chemical and mechanical characteristics and surface topography of the material, when compared to Biodentine mixed according to the manufacturer’s recommendations. Hence, the manufacturer’s instructions should be strictly followed.

Circuit Design Method to Improve Cryogenic Buffer Amplifiers Dynamic Parameters on CJFETs

We consider a circuit design method to increase a slew rate increase and transient process setting time decrease in buffer amplifiers (BAs), intended for operation in analog interfaces of physical values sensors and automatic devices at low temperatures. Differentiating transient correction circuits are introduced into the classical circuits of the BAs on complementary field-effect transistors (CJFETs) to improve these dynamic parameters. We investigated two buffer amplifier’s topologies: single-ended and balanced ones. The article shows the practical use of the proposed BA in the output and input stages of the high-speed operational amplifiers.

MECHANICAL PROPERTIES OF BREWERS DRIED GRAIN ASH-HYDRATED LIME IN CONCRETE

Ordinary Portland cement (OPC), the world most used binder in concrete production is adjudged a non - environmental friendly material due to the CO2 gas that is emitted into the atmosphere during its production process. Also, with the future generation in mind, limestone resource needs to be adequately preserved and managed. Previous studies on the search for alternative binders had centred mostly on the use of Agro - waste pozzolans in concrete, with little emphasis on the use of the pozzolans with additives that may further enhance reaction in concrete. Hence, this paper explores the possibility of using OPC with brewers dried grain ash-hydrated lime (BDGA-HL) in concrete. Prior to testing for initial and final setting time, compressive, flexural and tensile strength; cubes, beams and cylindrical specimens containing BDGA-HL at 5, 10, 15 and 20 % cement replacement were cast (in a ratio of 1:1.5:3.2 and w/c of 0.61) and cured in water for 7, 14, 28, and 56 days. Based on the findings, a decrease in setting time of the paste was noticed when OPC was partially replaced with BDGA-HL. Also observed was an improvement in flexural and tensile strength up to 10 %; while the maximum compressive strength was attained at 15 %. The results obtained for BDGA-HL concrete were higher than that of plain concrete. It was concluded that BDGA-HL has an excellent pozzolanic potentials improving the properties of concrete

MECHANICAL PROPERTIES OF BREWERS DRIED GRAIN ASH-HYDRATED LIME IN CONCRETE

Ordinary Portland cement (OPC), the world most used binder in concrete production is adjudged a non - environmental friendly material due to the CO2 gas that is emitted into the atmosphere during its production process. Also, with the future generation in mind, limestone resource needs to be adequately preserved and managed. Previous studies on the search for alternative binders had centred mostly on the use of Agro - waste pozzolans in concrete, with little emphasis on the use of the pozzolans with additives that may further enhance reaction in concrete. Hence, this paper explores the possibility of using OPC with brewers dried grain ash-hydrated lime (BDGA-HL) in concrete. Prior to testing for initial and final setting time, compressive, flexural and tensile strength; cubes, beams and cylindrical specimens containing BDGA-HL at 5, 10, 15 and 20 % cement replacement were cast (in a ratio of 1:1.5:3.2 and w/c of 0.61) and cured in water for 7, 14, 28, and 56 days. Based on the findings, a decrease in setting time of the paste was noticed when OPC was partially replaced with BDGA-HL. Also observed was an improvement in flexural and tensile strength up to 10 %; while the maximum compressive strength was attained at 15 %. The results obtained for BDGA-HL concrete were higher than that of plain concrete. It was concluded that BDGA-HL has an excellent pozzolanic potentials improving the properties of concrete

Performance of Rice Husk Ash - Calcium Carbide Waste in Concrete

This paper examines and present the findings of the physical and mechanical properties of concrete containing rice husk ash (RHA), and the blend of rice husk ash with calcium carbide waste (RHA-CCW). Concrete cubes, cylindrical and beam specimens containing different percentages of RHA and RHA-CCW by weight of cement (5, 10, 15 and 20 %) were cast. Compressive strength test was carried out after the specimens were cured in water for 7, 14, 28 and 56 days. Test for tensile and flexural strength was carried out after 28 days curing. Initial and final setting time test was carried out on mortar specimens with the same percentage of RHA and RHA-CCW. Bogues model was used to determine the elemental and compound composition of cement when blended with the RHA and RHA-CCW. From the results obtained, the compressive strength of RHA-CCW concrete increases as cement is partially replaced with RHA-CCW content, with the maximum strength attained at 5 % replacement. RHA concrete attains it maximum strength at 10 % replacement. The maximum compressive strength results obtained for both RHA and RHA-CCW concrete were higher than the strength of plain concrete (0 % replacement) by 1.1 % and 14.7 % respectively. Interestingly, results obtained for the tensile strength also shows a similar pattern of strength development with that of compressive strength. The flexural strength properties of concrete was improved upon when RHA-CCW was used in concrete compared to RHA. The results of setting time test for RHA mortar showed a decrease in setting time, while the reverse was the case for RHA-CCW mortar. In conclusion, provided adequate curing is maintained, the used of RHA-CCW gives a better performance in concrete than RHA. However, they both perform better in concrete than the plain, and can be used as additives in concrete production.

Effect of calcium hydroxide on fresh state behavior of sodium carbonate activated blast furnace slag pastes

This study represents the fresh state behavior of Na2CO3-activated ground granulated blast furnace slag (GGBS) pastes. Sodium carbonate (NC) is a suitable activator, though with an extended setting time. To accelerate the hydration process, NC was replaced with sodium hydroxide (NH), then, slaked lime (CH) was used as a carbonate binding agent. This replacement improved the rheological properties, but increased the setting time. The use of 3% CH with GGBS caused a significant decrease in setting time, enabled to set within 6.5 h. The decrement was attributed to the removal of a large amount of dissolved carbonate ions from the fresh state pastes. The NH replacement did not effectively enhance the fresh properties. In the pore solution, the CO32− ion concentration is one of the major parameter that affects the reaction besides other ions released from raw material.

A novel, doped calcium silicate bioceramic synthesized by sol-gel method: Investigation of setting time and biological properties.

The aim of the current study was to synthesize a fast-setting ion-doped calcium silicate bioceramic by the sol-gel method and to characterize its in vitro apatite-forming ability and cell viability. Calcium silicate (CS), doped calcium silicate with zinc and magnesium, with Ca/Zn molar ratios of 6.7:1 (DCS1), and 4.5:1 (DCS2), were synthesized by the sol-gel method. Matreva white MTA (WMTA, Matreva, CA, Egypt) was used as a control. The synthesized powders were characterized by x-ray diffraction. Setting time was measured using the Gilmore needle indentation technique. The in vitro apatite-forming ability of the materials was evaluated by scanning electron microscope and energy dispersive X-ray. NIH3T3-E1 cells viability was tested using MTT assay. The ion release of Ca, Si, Zn, and Mg was measured using inductive coupled plasma-optical emission spectroscopy (ICP-OES). One-way ANOVA was used to analyze setting time results. The Tukey's HSD post hoc test was used to establish significance (p < 0.001). For nonparametric data, the Kruskal-Wallis H test with Dunn's correction for post hoc comparison was used (p < 0.05). CS, DCS1, and DCS2 showed a significant decrease in setting time 33 ± 1.63 min, 28 ± 1.63 min, and 41.75 ± 2.87 min, respectively, compared to WMTA 91 ± 3.16 min (p < 0.001). DCS1 showed the highest apatite-forming ability and cell viability compared to the other groups. Ca and Si ions release decreased in both DCS1 and DCS2. The physical and biological properties of CS can be successfully improved by the sol-gel synthesis and ions doping. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:56-66, 2020.

Influences of bacteria-based self-healing agents on cementitious materials hydration kinetics and compressive strength

Bacterially induced calcium carbonate precipitation has been proposed as an alternative and environmental technique to develop self-healing cementitious materials system in recent years. This study investigated the influences of bacteria-based self-healing agents on the rheology, hydration kinetics and compressive strength of cementitious materials to further verify the feasibility of bacteria-based self-healing agents for crack repairing. The results showed that the rheology of cement mortar was significantly improved by the addition of bacteria-based self-healing agents. Incorporation of bacteria-based self-healing agents in cement greatly influenced the hydration kinetics. The self-healing agent RB could delay the hydration of cement resulting in final setting time increase, however the self-healing agents JB and NB accelerated the hydration resulting in initial and final setting time decrease. In addition, compressive strength test results showed that incorporation of RB in cement mortar resulted in early age compressive strength decrease, but the 28d compressive strength increased compared to control. Incorporation of JB in cement mortar enhanced compressive strength, however incorporation of NB in cement mortar could result in unwanted compressive strength loss. Furthermore, MIP test results indicated that the pore size distributions were different between cement paste samples with and without bacteria-based self-healing agents. The addition of bacteria-based self-healing agents increased the porosity between 100 and 1000nm. The porosity between 100 and 1000nm of the sample with NB increased the most compared to the samples with RB and JB. The incorporation of JB increased the porosity between 100 and 1000nm, but at the same time the small pores with a diameter under 10nm increased. These results could be used to explain the compressive strength development.

Effect of Adding (SBR) on Concrete Properties and Bond Between Old and New Concrete

The effect of adding cempatch SBR ( Styrene- Butadiene – Rubber) emulsion to the following was studied: Cement mortar with different dosages of SBR ( 10 %, 25%, 35% ) by volume of water. Compressive strength of this mortar was tested at ages ( 7, 28, 60 ) days. Initial and final setting time were also recorded. SBR also added to concrete mix 1 : 2 : 4 with 0.45 water to cement ratio by weight, and SBR in dosages of ( 10 %, 2 5%, 35 % )by volume of water . Compressive strength in ages ( 7, 28, 60 ) days was tested, also absorption, slump loss with time and flexural strength were also measured. And SBR was also used as bonding mortar layer between old and new concrete layers, the compressive strength and flexural strength of bonded samples were tested. The results of adding SBR emulsion to cement mortar affects compressive strength negatively at all age. Initial and final setting time decrease with increasing the dosage of SBR. The using of SBR emulsion as admixture for concrete mix affects compressive strength negatively at early ages ( 7 days ) and positively at later ages. It also reduces; the absorption of concrete and slump loss with time and increase the flexural strength. The use of SBR as bonding layer showed increasing in compressive and flexural strength of the bonded samples compared with samples having old and new concrete without bond layer.

Effects of slag and limestone powder on the hydration and hardening process of alite-barium calcium sulphoaluminate cement

For the existence of C2.75B1.25A3S¯ mineral, alite-calcium barium sulphoaluminate cement has dual priming action of alkali-activated effect and sulfate-activated effect on mixed material. When the total amount of added mixed material is unchanged, the effects for ratio of slag to limestone powder on water requirement, setting time, mechanical performance, hydration products and hydration heat of alite-barium calcium sulphoaluminate cement are investigated. The experimental results show that the water requirement and setting time decrease with the decrease of the ratio of slag to limestone powder. The compressive strength of specimen cured for 90days with 50% cement, 30% slag and 20% limestone powder is higher than that of pure cement. Slag and limestone powder prompt the second exothermic peak to appear early and shorten induction period. Furthermore, slag and limestone decrease rapidly hydration calorimetric of cement, especially for its early hydration calorimetric. Meanwhile, it is concluded that alite-calcium barium sulphoaluminate cement has dual priming action of alkali-activated effect and sulfate-activated effect.

Optimization of calcium chloride content on bioactivity and mechanical properties of white Portland cement

This research investigates the optimization of calcium chloride content on the bioactivity and mechanical properties of white Portland cement. Calcium chloride was used as an addition of White Portland cement at 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10% by weight. Calcium chloride was dissolved in sterile distilled water and blended with White Portland cement using a water to cement ratio of 0.5. Analysis of the bioactivity and pH of white Portland cement pastes with calcium chloride added at various amounts was carried out in simulated body fluid. Setting time, density, compressive strength and volume of permeable voids were also investigated. The characteristics of cement pastes were examined by X-ray diffractometer and scanning electron microscope linked to an energy-dispersive X-ray analyzer. The result indicated that the addition of calcium chloride could accelerate the hydration of white Portland cement, resulting in a decrease in setting time and an increase in early strength of the pastes. The compressive strength of all cement pastes with added calcium chloride was higher than that of the pure cement paste, and the addition of calcium chloride at 8 wt.% led to achieving the highest strength. Furthermore, white Portland cement pastes both with and without calcium chloride showed well-established bioactivity with respect to the formation of a hydroxyapatite layer on the material within 7 days following immersion in simulated body fluid; white Portland cement paste with added 3%CaCl 2 exhibited the best bioactivity.

Improvement of the Properties of Mineral Trioxide Aggregate by Mixing with Hydration Accelerators

Introduction Mineral trioxide aggregate (MTA) is used widely in endodontic therapy. This study examined the setting time, compressive strength, and pH of MTA mixed with several hydration accelerators (calcium chloride, low-dose citric acid, calcium lactate gluconate solution). Methods Group 1 (control) was obtained by mixing MTA with distilled water. In group 2, MTA containing 10% calcium chloride was mixed with distilled water. In group 3, MTA was mixed with 0.1% citric acid. In group 4, MTA was mixed with a calcium lactate gluconate solution. The setting time, compressive strength, and pH were examined. Results The setting time of MTA mixed with hydration accelerators was significantly shorter than that of MTA mixed with water ( P < .01). In particular, replacing distilled water with a calcium lactate gluconate solution provided a significant decrease in setting time. The compressive strengths of MTA mixed with hydration accelerators were significantly lower than that of MTA mixed with water ( P < .01), but those values increased with time. The pH of MTA mixed with hydration accelerators was significantly lower than that of MTA mixed with water ( P < .01) but stable at a high level (pH 11–12). Conclusions Hydration accelerators improved the setting time of MTA. Nevertheless, more study will be needed to improve MTA without impairing its preexisting advantages.

Chemical Modification of ProRoot MTA to Improve Handling Characteristics and Decrease Setting Time

Mineral trioxide aggregate (MTA) fulfills many of the ideal properties of a root-end filling material. However, the composition of this material often makes MTA difficult to use, a direct result of its granular consistency, slow setting time, and initial looseness. Additives used by the Portland cement (PC) industry to increase PC's plasticity and decrease its setting time were added first to PC and then to gray MTA in an attempt to improve MTA's handling characteristics, with the combination providing the best handling characteristics tested for its effect on compressive strength (for changes in the original material's properties) and decrease in setting time. An admix of 1% methylcellulose and 2% calcium chloride resulted in a mix of chemically modified MTA that, when compared with unmodified MTA, (1) handled similarly to a reinforced zinc oxide-eugenol cement, (2) gave an approximately equal compressive strength, and (3) set one third faster (57 +/- 3 minutes).

Influence of blended gypsum on the properties of Portland cement and Portland slag cement

The paper deals with studies on the effect of unprocessed phospho-(PG) and fluorogypsum (FG) added independently and in combination with natural gypsum (NG) on various properties of portland and portland slag cement (PSC). The results showed that the adverse effect of P 2O 5 and F impurities in PG and those of FG could be offset by blending NG. An increase in compressive strength and decrease in setting time of the cements was observed on using the blended gypsum. A mix of 40:60, PG/FG by weight gave maximum compressive strength. The properties of portland cement and PSC with blended gypsum conformed to the requirements of cement produced with NG. As compared to PG and FG, the power consumption for grinding cements was reduced on using the blended gypsum.

On‐machine measurement of workpieces with the cutting tool

A new system for on‐machine measurement of workpieces is described. The system is based on a fine touch sensor that enables the cutting tool itself to act as a contact probe to inspect the workpiece. The proposed measurement technology combines the Q‐setter with the fine touch sensor. This low cost measurement system is applied to automatic workpiece setup and improving workpiece dimensional accuracy on a CNC turning center. It is shown that using the proposed measurement system results in workpiece setting time decrease and workpiece machining accuracy improvement. The development of the on‐machine measurement system makes the fine touch sensor extremely attractive for CNC machine retrofitting.

Die stone disinfection: incorporation of sodium hypochlorite.

Previous research has shown that dental gypsum casts may be effectively disinfected by the substitution of 10% of the gauging water with 5.25% solution of sodium hypochlorite. The purpose of this investigation was to determine the properties of gypsum produced from such a solution as opposed to tap water alone. Tests included setting time, compressive strength, rigidity, diametral tensile strength, setting expansion, hardness, and detail reproduction. The addition of sodium hypochlorite to the gauging water resulted in a statistically significant increase in the compressive strength and rigidity, and a decrease in setting time (p < or = .5). All other properties remained unchanged. This substitution may be an effective and convenient method of disinfecting gypsum casts in the laboratory without adversely effecting physical and mechanical properties.

A comparison of properties for zinc phosphate cements mixed on room temperature and frozen slabs

The following conclusions may be drawn from this study: 1. More powder may be incorporated into the cement liquid when the cement is mixed on a frozen slab rather than a room temperature slab. 2. A dramatic increase in the working time and decrease in setting time occur with frozen-slab mixes. 3. No statistically significant difference in compressive strength was found for the room temperature and frozen-slab mixes. 4. Solubility and disintegration values for room temperature and frozen-slab mixes of the three cements not containing fluoride were below the maximum limit of ADA Specification No. 8.