Papers by Keyword: Water Reducer

Abstract: Based on the low-field NMR, this study inveitigated bleeding property of the fresh cement pastes mixed with various gypsum dosage, specific area of cement and water reducers. Results showed that the gypsum dosage between 3 % and 5 % will cause an decrease bleeding and a lower bleeding velocity, while a 1 % gypsum dosage will increase the bleeding as a function of time. The increase of the cement surface will lead to a less bleeding rate. This can be explained that the finer particle will contribute to the packing which will form a low permeability of the cement paste, as a result less bleeding water is observed. The PCEs-made sample has smaller hot zone area which indocated the PCEs has good bleeding stability when varing water cement ratio. Furthermore, bying comparing with the NPE, it was found the ACS type water reducer has higher bleeding sensitivity when high water cement ratios were used.

Abstract: To study the strength of cement mortar with different particle size of waste glass powder, grinding and screening the colorless waste glasses to 38-53,53-75,75-150,150-300,300-600μm, and as supplementary cement materials replacing the cement of cement mortar at 5,10,15,20,25,30%, respectively. Meanwhile divide the experiment into two parts:containing water reducer or not and add fly ash as comparison at the same time, measuring the flexural and compressive strength of cement mortar for 28 days. It is concluded that the flexural and compressive strength of cement mortar are decreased when mix with water reducer with maintaining the dosage of water;The optimum size and amount of waste glass powder in the cement mortar keep the same whether it is mixed water reducer or not; The flexural and compressive strength for 28days of the cement mortar reach the best value and differ with the baseline group very few whether it's mixed water reducer or not.

Abstract: As urbanization level of our country improves constantly, urban population will increase dramatically. Then industrial and civil buildings and other facilities will be multiplied, which leads to use plenty of high-performance concrete materials. i.e. China's building materials, especially the use of concrete will be increased year by year^[. And the chemical admixtures is an essential fifth component of concrete^[2-. It has been nearly 50 years since the chemical admixtures were researched,expolited and used in large scale^[.But the water reducer are used most widely, its characteristics is to reduce the water consumption of concrete, and minimize the porosity of concrete. Thereby which enhances its intensity and durability.

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: During the technology development of modem concrete, concrete structure crack (especially early-age crack) becomes more and more serious and has been one of main research directions of civil engineering. This paper aims at the seriousness of concrete structure crack and presents one of main cause is that concrete early-age (especially autogenous shrinkage) become large through the experimental study. autogenous shrinkage are mainly belongs to temperature cracks and desiccation cracks. Analyses the affection of ash and water reducing agent on the hydration heat, under the optimum proportion experiment which aims at reducing he hydration heat of cement. The best program are obtained that double mix with 20% fly ash and 1.5% water reducing agent .Design mortar’s early anti-crack experiment, and study crack-resistance and other mechanical properties based on different ages & different mix proportion. From the experiment, analyses early cracking under the influence of admixtures. The mix proportion of 20% fly ash, 10% slag and 1.2% water reducing agent can minimize the creation of cracks.

Abstract: In this work, the adsorption of naphthalene-based water reducer (FDN) on slag ground with or without the composite retarder YP-3 and PN (YP) in alkali-activated slag cement (AASC) activated by water glass (WG) has been studied in detail. The results show that the effect of the adsorption of water reducer on AASC depends directly on the dosage of the water reducer and on the composite retarder used. For example, mixed slag particles adsorb thrice as much water reducer FDN than pure slag particles at 1% mass of the slag, and the absolute value increment of the zeta potential of the AASC suspension containing the composite retarder is 8.61 mV, compared with 1.99 mV in the system without the composite retarder. Moreover, the AASC pastes activated by WG containing the retarder YP show better rheological properties and lower fluidity loss over time.

Abstract: The properties of polycarboxylate superplasticizers(PCs) are related to their structures. For better understanding the different properties between PCs, their structures should be examined. In this paper, three kinds of PCs are synthesized by radical copolymerization method. The structure and property of PCs are studied by means of high performance liquid chromatography, zeta potential, water reducing rate and fluidity of cement paste. The results show that the conversion rate of reaction monomers is over 97%, and the reaction monomers are fully in the polymerization. The ester-type PCs has a higher water reduction capacity than the ether-type. At the same dosage, the adsorption and dispersion ability of ester-type PCs are stronger than that of ether-type PCs, yet the ether-type PCs has better slump retention performance in the cement pastes.

Abstract: Concrete admixture is a kind of addition agents, which can improve the performance of concrete. Adding a certain amount of concrete admixture can enhance the early strength, the age strength, and the anti-permeability strength of concrete. Also, concrete admixtures can improve the workability and adjust the setting time of concrete, so as to reduce the dosage of concrete and save the cost of concrete. This paper describes the types of concrete admixture and their functions, studies the functions of water reducers, and analyzes their effects to concrete, so as to improve the concrete performance and save materials in actual operation.

Abstract: A two-step fermentation procedure for maize straw hydrolysis by Phanerochaete chrysosporium, Trichoderma and Aspergillus niger were investigated in this study. 2 mL of P. chrysosporium (10⁷spores/mL) was added to 50 mL medium for the first fermentation stage. The optimal culture conditions were 28°C of culture temperature, 4.0 of pH, 8 days of culture time, 2 mL of Trichoderma suspensions (10⁷spores/mL) and 1 mL of A. niger suspensions (10⁷spores/mL) of the inoculums size on the second fermentation stage. Under the optimal conditions, the crude degradation rate achieved 48.2%. Via sulfonation, oxidate-lignosulfonate alkali lignin (OLAL) was achieved from maize straw hydrolysate(MSH).OLAL and MSH can be partial substitution for common water reducers and OLAL was more efficient compared to that of MSH.

Abstract: The ultrafine grinding of white cement and its hydration were studied. The ultrafine grinding parameters, such as crushing pressure and feeding pressure of jet mill in a lab scale were optimized. The influence of the particle size distribution of ultrafine white cement and the usage of water reducer on the standard thickness and early age strength of white cement paste was investigated. The results indicated that the ultrafine white cement with d₅₀=4.62 µm and d₉₀=10.48 µm can be obtained when the crushing pressure was 0.7 MPa and the feeding pressure was 0.4 MPa. The standard thickness of white cement paste decreased from 30.5 % of the raw material to 26.0% of the ultrafine white cement (d₅₀=4.42 µm, d₉₀=10.26 µm). The use of 2% naphthalene-based water reducer can reduce 15.4% water consumption. The 3d compressive strength of pure ultrafine white cement sample reached 174% of that of raw white cement. The 28d compressive strength of ultrafine white cement with 3% naphthalene-based water reducer added was 22.9% of that of pure ultrafine white cement. A large number of needle-shape nanometer ettringite (AFT) was generated in the early stage of hydratration and layered C-H-S was formed with the decreasing of the amount of AFT in the later stage of hydratration. It’s supposed that the formation of the large number of needle-shape nanometer AFT was related to the reducing of the particle size of C₃A during the ultrafine grinding and the no adjustment of the amount of the added gypsum, which resulted in the faster hydration of C₃A.