Papers by Keyword: Setting Time

Abstract: Concrete innovation in terms of changing some of its properties to improve quality and workability cannot be separated from the use of chemical additives, one of the admixtures that was used in this research was a type of superplasticizer with the brand Naptha Belide E121 Series. In this research the author wanted to examine the setting time admixture of Naptha Belide E121 Series in the application of 24-hour fast-track concrete K-500, the use of admixture doses in this research was 0%, 0.4%, 0.6% 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2% of the weight of cement, while the cement used was OPC Cement (ordinary Portland cement) Type 1. This research aimed to determine the cement setting time in K-500 high-quality fast-track concrete applications with dose variations. The results of the setting time test of this research were that at a dose of 0%, the initial setting time was 117.01 minutes, while 0.4% - 1.0% of the initial setting time of cement increased or slowed down starting from 178.25 minutes - 240.71 minutes. At the same time, at doses of 1.0% to 1.8% doses, the initial setting time decreased or accelerated from 165.21 minutes to 92.86 minutes.

Abstract: Lignin is the largest component of biomass and the second most abundant natural polymer. Lignin-based products are commonly applied as binders, and are utilized for polymer applications. The purpose of this study is to use lignin as an admixture in mortar. The lignin dissolved in 1M NaOH solution, and the ratio was 1:5 by weight. The lignin contents utilised in this study were 1%, 2%, 3% by weight of cement and a cement water rasio of 0.4. Lignin as an admixture in mortar increased the flowability value. The flowability value increased as the lignin content rose. the highest compressive strength and flexural strength occured at 1% lignin content. They were 35.71 MPa and it was 5.49 MPa, at the age of 28 days. The longest setting time was obtained at 3% lignin content for initial setting time of 285 minutes, and final setting time of 540 minutes. Based on the results of the setting time test, it has been determined that the more lignin was mixed in, the longer the setting time will be. Therefore lignin as an admixture to the mortar makes changes its characteristics.

Abstract: This paper explores the production and properties of geopolymer cement mortar using laterite soils. The aim was to evaluate the laterite-based geopolymer mortars for masonry bedding applications. The testing programme encompassed three series of mixes tested to determine setting times, flowability, flexural strength and compressive strength. Two types of sands were used including standard sand and natural sand. The effect of water-to-laterite ratios, activating agent concentration, and cement-to-sand ratio were established. The properties of standard cement paste, and mortar were used as a reference. The study found that geopolymer mortar made from laterite meets the requirements for masonry bedding.

Abstract: This research investigated the influence of phosphogypsum (PG) addition to mortar mixture and determined the possibility of utilizing PG in soil stabilization. Originally, the chemical composition and mineralogy of the PG were determined using X-ray fluorescence (XRF) and X-ray diffraction (XRD) tests. The principal constituent of PG becomes calcium sulfate hemihydrate with the presence of some impurities. A total of 9 mixes have been developed: A plain mortar mix is a comparative base, and the other 4 mixes are with 5, 10, 15, and 20 % cement replacement with PG for each type (fresh and stockpiled PG called PGF and PGS, respectively). The experimental program focuses on analyzing the effects of PG on setting time, hardened density, compressive strength, and water expansion of mortar mixtures before its soil stabilization application. Test results indicate that with higher PG, the setting time of the mortar mix is delayed except for the mixture with 20% PG, which experienced an early false set. The results of the compressive strength tests revealed that the 5% PG mixes exhibited higher values compared to the control mix, starting from the 28-day curing period, regardless of PG type. Although the higher PG content and compressive strength lowered, the expansion levels were very low based on the ASTM C 1260 limits for all mixtures, excluding heaving risks.

Abstract: Generally, the setting time and early strength of the cementitious materials are good indications to identify their suitability to be employed as binding materials. Due to the high surface area of nanomaterials, it is considered one of the optimal solutions to modify these properties. Accordingly, this work is focused on comparing the impact of laboratory-prepared tungsten oxide nanoparticles (WO₃-NP) on two cementitious materials: OPC and alkali-activated slag (AAS). The initial/final-setting time and early compressive strength up to 28-days of the OPC and AAS specimens, modified with 1, 2 wt.% WO₃-NP, were investigated. The results displayed that WO₃-NP has a significant impact on the acceleration of the initial/final-setting time of both binding materials. Moreover, the optimal dosage from WO₃-NP (1 wt.%) upgraded the compressive strength by 19.5 and 15.1% for OPC and AAS, respectively after 7 days. The nucleation-seeds and nano-filler effect of WO₃-NPs are the focal explanations behind improving these properties via the formation of strength-giving phases and then obtaining a compact microstructure as proved by XRD and SEM.

Abstract: Calcium hydroxide (Ca(OH)₂ has been recently synthesized from natural Indonesian limestone to be used as an intracanal medicament for root canal infection. Ca(OH)₂ is applied into the infected root canal in a non-setting paste form to release calcium and hydroxyl ions which elevates the pH and provide an antimicrobial effect to pathogenic bacteria. To form an injectable paste, Ca(OH)₂ powder has to be mixed with a proper solvent to produce optimal consistency, ion dissociation, and maintain its property as a non-set material. Solvent is an important factor affecting ion dissociation and preserving its non-setting paste condition. The aim of this study is to synthesize Ca(OH)₂ powder from Indonesian limestone, and evaluate the setting time of Ca(OH)₂ paste from mixture of Ca(OH)₂ powder synthesized from Indonesian limestone (limestone Ca(OH)₂) with various solvent, to evaluate which solvent serve best to prevent the Ca(OH)₂ paste from setting, to form an ideal paste be used as an intracanal medicament. This study consists of 5 groups (n=5); commercially Ca(OH)₂ paste (Calcipex II) as positive control, Ca(OH)₂ powder (Merck) + distilled water as negative control, limestone Ca(OH)₂ powder + natrium carboxy methylcellulose (Na CMC) as group 1, limestone Ca(OH)₂ powder + propylene glycol (PG) as group 2, and limestone Ca(OH)₂ powder + polyethylene glycol (PEG) as group 3. Setting time evaluation was measured according to ISO 9917 by vicat needle in 37°C to mimic the physiological body condition. Results were analyzed by One Way Anova test and Post Hoc Tukey test. The result of this study showed that the setting time of Ca(OH)₂ paste mixed with Na CMC solvent was 1:04 hours, PG 72:15 hours, and PEG did not harden until 7 days of observation. PEG is a hygroscopic high viscosity solvent, resulting in low and steady molecule interaction, thus prolonged its setting time. From this study it can be concluded that PEG inhibit Ca(OH)₂ setting reaction up to 7 days and might be used as solvent for Ca(OH)₂ paste as intracanal medicament.

Abstract: In high pressure water-rich formation, the grout is diluted by groundwater, could not develop early strength as quickly as possible for the dissipation of cementing material, failed to fill effectively the space between the segment and formation, which is unhelpful to control segment floating. In this study, by adding a variety of organic and inorganic materials to reduce grout setting time, meanwhile ensure the low loss of fluidity, high anti-aqueous dispersions, low shrinkage, finally, to achieved better effect than Two-component grouting.

Abstract: The mould-ability of concrete into intricate forms and the versatility of its constituent materials has made concrete to be the most preferred construction material. However, in developing nations such as Nigeria, poor quality of concrete is listed among the common causes of building collapse. Thus, this study investigated the effects of chemical compounds of four commonly used local ordinary Portland cement brands on the compressive strength of normal concrete. The cement was labelled brands A, B, C, and D, respectively, while all the other constituent materials remained constant in this study. The HACH DR 200 direct reading spectrophotometer method was used to analyze the composition of the oxide in each of the cement samples, while the Bogue composition formula was used to estimate the compound compositions of the cement samples. A designed mix proportion of 1:2:4 (cement: sand: granite) at water-cement ratio (w/c) of 0.6 was used to produce the concrete with an expected target strength of 25 N/mm². Also, the initial and final setting time of the cement samples and the workability of the concrete mixes were determined. Forty-Eight (48) numbers cube samples were cast and tested for compressive strength at 3, 7, 14, and 28 curing days, respectively, using a 150 mm concrete cubes. The result shows the setting time of the cement samples to be within an acceptable period. Also, results indicated that the cement brands have a significant percentage of Tricalcium Silicate (C₃S) content and low percentage Dicalcium Silicate (C₂S) content responsible for faster hydration rate and higher early strength gain of the concrete. However, it was observed that a higher percentage of Tricalcium aluminate (C₃A) leads to higher strength gain from 7 to 28 days of curing age.

Abstract: Environmental degradation caused by deforestation activities for harvesting of limestone from the hills and its calcination process at cement factory along with disposal of cockle shell waste from fisheries industries is in need of resolution. In view of sustainable green environment, approach of utilizing cockle shell waste as partial cement replacement in cement production would reduce pollution caused by both industries. Thus, this research investigates the effect of cockle shell powder as partial cement replacement on setting time and compressive strength of mortar. A total of five types of mortar mixes consisting different percentage of cockle shell powder as partial cement replacement from 0%, 10%, 20%, 30%, and 40% by weight of cement were prepared. Setting time test were conducted on fresh paste. All specimens were subjected to water curing until the testing age. Compressive strength test were conducted on hardened mortar cubes at 3, 7 and 28 days. Finding shows that integration of cockle shell powder as partial cement replacement influences the setting time and compressive strength of mortar. Suitable combination of 10% cockle shell powder successfully enhances the compressive strength of mortar. Conclusively, success in transforming the cockle shell waste to be used as partial cement replacement in mortar production able to reduce cement consumption, save landfill usage for trash dumping and promote cleaner environment for healthier lifestyle of community nearby.

Abstract: In this paper, the effects of various components in alkali-free accelerator on the setting of cement paste were studied, and the morphology of the hydrates during hydration was investigated with SEM. The experimental results show that the aluminum sulfate, diethanolamine and hydrofluoric acid can effectively shorten the setting time of cement paste, while excessive dosage has minimal impacts on the setting time. The diethanolamine and hydrofluoric acid can not only shorten the setting time but also can improve the stability of the accelerator. It was evidenced by the SEM that the aluminum sulfate accelerates cement coagulation by quickly forming a large amount of ettringite in the cement paste. The results in this study suggest that the shortest setting can be achieved when the dosage of aluminum sulfate, diethanolamine and hydrofluoric acid in a liquid alkali-free accelerator is 57 %, 5 % and 5.7 % , respectively.