Papers by Keyword: Initial Setting Time

Abstract: Mortar is another construction medium made of cement, which is mixed with sands and water, and lime is applied to increase the product's longevity. The gypsum renders workability to make mortar or concrete by keeping the cement in plastic state at early age of hydration. The gypsum is called the retarding agent of cement because the gypsum which is mainly used for regulating the setting time of cement. To get the optimal setting time for optimum compressive strength, gypsum in the cement needs to be control. Cement setting time when it hydrates and renders cement paste when combined with water. The objective of this research is to analyze the effect of different amount in Ordinary Portland Cement (OPC). Vicat apparatus was used to analyze the initial setting time of cement paste. Gypsum and clinker were used in production of mortar with the size 50 mm x 50 mm x 50 mm. This research deals with observation of the cement setting time to point out some differences that would effect to strength of mortar. The results reveal that control gypsum with 4% of gypsum has the highest strength as compared to 0% of gypsum and 8% of gypsum. The setting time of cement paste are discussed with respect to their influence on the strength of mortar.

Abstract: Usage of mineral admixture and chemical admixture in concrete or mortar is a usual solution to reach full compaction, particularly where reinforcement blockage and lack of skilled labor happen. In this paper effect of mineral admixtures (Carbon-free fly ash, hereafter CfFA, and normal fly ash) on fresh properties and rheology of mortar have been investigated. As a result, it was confirmed that CfFA increased significantly the fluidity and air content of mortar in comparison to normal fly ash, both in 15% and 30% replacement; however, the flow loss and air stability within one hour were almost equal. In addition, the initial setting time has also been affected by variation of materials. The two mixing of 30% and 15% of CfFA had a shorter setting time in comparison to the mortar with normal fly ash. Furthermore, CfFA based mortar had a great influence on rheology of mortar. Compared to normal fly ash, CfFA Considerably decreased the plastic Viscosity and increased the productivity of the mortar, both in non-vibrated and vibrated condition, particularly those with 30% replacement.

Abstract: This study used a sodium hydroxide (NaOH) solution to activate a mixture of water treatment sludge, fly ash, and slag, in order to produce a new alkali-activated controlled low-strength material (CLSM). Fresh properties of this new CLSM were investigated through the tests of workability, setting time, and ball drop time. Test results show that the addition of water treatment sludge (WTS) decreased workability. In addition, the addition of such WTS increased initial setting time and ball drop time, whereas the alkali equivalent (AE) shortened the initial setting time and ball drop time. At a liquid-to-solid ratio (L/S) of 0.9, a WTS content of 10%, and an alkali equivalent of 9%, the fresh properties for the CLSM conforms to the design principles and provisions of the Public Works Department, Taipei City Government, and is ideal for road construction in order to reduce traffic impact.

Abstract: In order to save the costs of the rapid hardening and repair sulphoaluminate cement and improve its working performance, the effects of slag, fly ash, silica fume in different contents and different adding ways on the initial setting time and working performance of sulphoaluminate cement are studied. The results show that the initial setting time of single-doped slag and fly ash both meet the requirements of repair materials, but silica fume significantly cuts the cement’s initial setting time short, which does not meet the construction conditions for rapid hardening and repair. Ultimately it is determined that the mechanical properties of sulphoaluminate cement are the best when slag and fly ash are compound added by the content of 30% at 4:1 mass ratio and simultaneously the initial setting time meets the conditions for rapid hardening and repair.

Abstract: The effect of cement replacement materials on hydration of solidified waste in ordinary Portland cement has been investigated based on initial setting time. Five cement replacement materials namely, rice husk ash, condensed silica fume, activated carbon, fly ash and meta kaolin were selected for solidified organic waste in the cement. The initial setting time was conducted with incorporation of 5 to 15 percent cement replacement materials at water to cement ratio of 0.45. The initial set of cement involves mainly the development of ettringite fibers and portlandite. Additions of CSF, FA and AC have delayed the initial setting time. The governing factors contributed to the delayed in setting time are the cement replacement materials, particle size and composition, which significantly retard development of ettringite fibers. 5 % MK and RHA tend to accelerate the setting with 138 and 150 minutes, accordingly as these binders have larger particle size.

Abstract: In order to broaden the utilization of desulfurization gypsum in China and achieve the direct usage of desulfurization gypsum, in this paper, citric acid (CA), sodium citrate (SCA), sodium tripolyphosphate (STPP), Sodium hexametaphosphate (SP) were selected as retarder to modify desulfurization gypsum. The experiment results are as follows: the effect of SP, STPP, CA, SCA on desulfurization gypsum initial setting time is obvious; the turn is STPP> CA> SCA> SP; when the retarder dosage of STPP in desulfurization gypsum reaches 0.5%, the initial setting time can be extended to 210 min, the final setting time to 240min, which fully meets the demand of gypsum-site construction; inhibiting gypsum particles dissolution and preventing the growth of crystal nucleus are the fundamental reasons of STPP.

Abstract: In order to broaden the utilization of desulfurization gypsum in China and achieve the direct usage of desulfurization gypsum, in this paper, Polycarboxylic acid water-reducer (HC), Naphthalene sulfonate formaldehyde polycondensate (NF) and Sulfonated melamine formaldehyde resin (SM) were selected as water reducer to modify desulfurization gypsum. The experiment results are as follows: SM water reducer has little effect on setting time of desulfurization gypsum, although it is helpful to increase the strength of the gypsum-sample, however, compared with HC and NF, it has no obvious effect. About HC water reducer, it has obvious effect on setting time of desulfurization gypsum, so does it to desulfurization gypsum strength, but, higher water using of normal consistency will do adverse effect on the whole with the increase of the dosage. NF water reducer has the similar effect on setting time and sample's strength on desulfurization gypsum with HC, but the dominant changes have no discipline among different mixing amounts with these two water reducer. Lower water using of normal consistency benefits the retention of the sample's strengths.

Abstract: The solvent that is used to make the gel is water which is widely applied on the oil-field. The solvent is actually inject water. The chromes receipt which were already used on the oil- field is listed in the experiment, The research is that according to the inject water which come from Zhuangxi and Feiyan Beach oil field to make the gel, then to observe whether the polymer system gelatinize, which one is more practical and economical. The comparison was carried out in the experiment, the gel that is made of distilled water contrast with the get which is made of Zhuangxi and Feiyan Beach inject water, then observe the affecting factor of gelatinization, such as pH, temperature, drug style, concentration. According to the experiment, the intensity of the gel which is made of the Zhuangxi oil field inject water with the HPAM of Changan Group is the largest, however initial setting time is the shortest, the intensity of Feiyan Beach gel is smallest, initial setting time is the second .HPAM from Japan which is made up by water from Zhuangxi can be gelatinized at the initial pH, but The gel which is made of distilled water and Feiyan Beach can’t be gelatinized, the adjustment of the pH and the increasing concentration can make the polymer gel.

Abstract: Additives will affect directly the clinic operational properties of investment materials, and finally affect the quality of castings. The relationship between additions and properties of the mullite-based investments has been studied. This paper describes effect of HBO3, Na5P3O10 and (NaPO3)6 on properties (including fluidity, initial setting time and compressive strength) of the mullite-based investment materials.It is found that with addition of HBO3, the fluidity of the mullite-based investment materials improves greatly, the initial setting time prolongs, and the compressive strength of investment materials changes little；with addition of Na5P3O10, the fluidity of mullite-based investments improves greatly, the compression strength increases, and the amount of silica gel decreases clearly；with addition of (NaPO3)5, the fluidity of mullite-based investments increases, the initial setting time prolongs, the compression strength decreases, and the amount of silica gel decreases clearly.

Abstract: The ethylene diamine, acetone and dibutyl phthalate are used as the curing agent, diluent and flexibilizer in the researches about epoxy mortar. But in fact these materials are difficult to be bought in market because of the toxicity. The influence of the additives on the workability and mechanical properties of epoxy mortar are investigated by using the orthogonal experimental design method in this work, and all the additives can be bought easily from the market. The results are as followings:(1) the influence of curing agent on the initial setting time, the toughness and the 1d, 3d compressive strength of epoxy mortar is significant; (2) the influence of diluent on the workability of epoxy mortar is significant; (3) the influence of flexibilizer on the 7d compressive strength is significant; (4) the interface bonding of epoxy mortar and cement mortar is good; (5) the optimum proportion by mass for epoxy mortar is, epoxy resin: curing agent: diluent: fumed silica =1:0.5:0.1:0.05:0.01.