Papers by Keyword: Water Retention

Abstract: In this study, the utilization of two types of spongilites in various addition in cement mortars has been investigated with the purpose of exploring a new application of this natural pozzolans as cement mortar additives. The influence of the addition of spongilites on the physico-mechanical properties, frost-resistance, and microstructure of cement mortars as a function of time was studied. The results revealed that the rising proportion of spongilites in cement mortars causes increase in water retention of mortars, reduction of their bulk density, increase in porosity of mortars due to the growing predominance of capillary pores maintaining sufficient mortars strengths, and slightly increase in the frost-resistance of mortars. After initial tests, partial replacement of cement in fine-grained cement mortars with hitherto unexploited spongilites seems to be very promising. Based on the achieved results, a 20% cement replacement can be recommended as optimal.

Abstract: Cellulose ethers (CEs) are widely used as viscosity enhancing, water retaining additives in cement based mortars. Nevertheless, studies about the effect of cellulose ethers on the properties of aerial lime-based mortars are very lack. The use of water retaining additives in lime mortars can influence not only their fresh state properties but also the pore structure and strength of hardened mortars. In this work, four different commercial cellulose ethers were added to lime mortars in order to test their influence on properties of mortars in the fresh state. Mortar rheological parameters (relative yield stress, consistency coefficient and fluidity index) were correlated with flow table tests, relative density measurements, water retention and air content in the mortars. It was found that CEs reduce the spread of lime mortars and increase air content in the mortars. The CEs are not so effective in water retention compared with other types of water retention agents. Most dosages of CEs change the behaviour of mortars from pseudoplastic to dilatant. In contrast to the effect of CEs in cement-based materials, their viscosity enhancing behavior in lime mortars is denied, due to the presence of large amounts of calcium hydroxide. From this point of view, the CEs are not so suitable to use as viscosity enhancing admixtures in lime mortars like derivatives of chitosan or guar gum.

Abstract: In this paper, the behaviour of fresh lime mortars modified by etherified derivatives of guar (hydroxypropyl guar (HPG), carboxymethyl hydroxypropyl guar (CMHPG) and native guar gum (GG)) is assessed with the purpose of exploring a new application of such derivatives as lime mortar admixtures. The rheological parameters (relative yield stress, consistency coefficient and fluidity index) and viscoelastic properties were correlated with flow table tests, relative density measurements, water retention abilities of mortars and air content in mortars. Results were seen to be strongly dependent on substituents of the guar. Non-ionic derivative (HPG) exhibited the biggest impact on the yield stress and elastic properties of the mortars. The ionic CMHPG showed the thickening effect. GG had low impact on water retention, while HPG and CMHPG displayed high water retention capability.

Abstract: This paper reports studies to investigate the relationships between hydrophobicity of biochar surface and soil water retention. The studied biochars were produced from acacia wood, cashew wood and bamboo. The resulting materials were oxidized via liquid oxidation to generate hydrophilic biochars containing oxygenated functional groups on the surface. All biochars were characterized and their ability as soil additives to enhance water retention was assessed. Our results suggest that hydrophobicity/hydrophilicity of biochars is not the major factor governing water retention ability of this particular soil. However, hydrophilicity of biochar helps improve soil permeability by providing better wettability to the soil.

Abstract: Pure cement mortar and concrete possess disadvantages such as brittleness, low bonding or adhesion strength, low tensile strength, large drying shrinkage, low chemical resistance. In order to overcome these disadvantages, polymer concrete is used as a construction material in Singapore as the properties of polymer-modified (or polymer cement) mortar and concrete are superior to conventional cement mortar. In Singapore, new products or technologies can be found through distributers, agents, etc. Singapore is able to afford and try high quality products to maintain the quality of a building and structure. The importance of applying polymer to protect, repair, coat and strengthen concrete structures in Singapore have grown in the last two decades. To ensure and maintain the standards of construction and building quality, polymer concrete are used extensively in new developments in Singapore. In this paper, the mechanical properties and its corresponding testing methods for several types of polymer concrete used in Singapore are discussed. These products include mortar used to repair concrete spalling, acrylic polymer cementitious coating, waterproofing membrane, epoxy mortars and grouts, fibre reinforced plastic (FRP) and epoxy resin. In addition, the specifications for the above products used in Singapore’s Housing Development Board (HDB) are discussed in the paper as it’s a requirement for suppliers to test their products in accredited laboratories before it can be used.

Abstract: The purpose of this research was to study water retention properties of superabsorbent hydrogel based on poly (acrylamide)/biofiller hydrogel and urea liquid fertilizer, by solution polymerization. Kenaf fiber (KF) was used as biofiller and the preparation of the poly (acrylamide)-grafted-kenaf fiber (PAAm-g-KF) hydrogel was carried out by polymerizing the monomer. Urea fertilizer was employed as polymerization media. N,N’-methylene bisacrylamide (MBA) was used as a crosslinker and ammonium persulfate (APS) as an initiator. Water retention of the hydrogel was studies in soil with three different samples (Controlled, PAAm Hydrogel, PAAm-g-KF). The PAAm-g-KF was also applied to agricultural field. The results show that PAAm-g-KF greatly improved water retention in the soil and agricultural field.

Abstract: The use of foundry waste in civil engineering is one of the most discussed issues by several environmental polities. This is caused by the excessive deposition of foundry waste on sanitary landfills. In order to find solutions to overcome this situation, this paper investigates the effect of the foundry powder concentration in the structure of mortars. Experiments were conducted with mortars processed at several concentrations of binders, aggregates and foundry powder. Results indicate that mortars built with foundry waste have water retention above to 75%. This observation indicates that mortars processed with foundry waste can be used in civil construction.

Abstract: This study is to investigate the potential of ENR to be incorporated with chitosan for slow release urea fertilizer. In this research, mixture of chitosan and epoxidized natural rubber (ENR) was used as binder to take advantage of their biodegradable and polar characteristics, respectively. The effect of mixing formulation to the properties of fertilizer was studied. Firstly, the chitosan and ENR were diluted in toluene with the presence of bentonite as filler. Then, urea powder was mixed and stirred for 20 minutes before left to dry overnight in an oven at 60°C. Water absorption and water retention analysis were carried out on compressed pellets. The increase of ENR loading was observed to contribute to the increase of hydrophobic properties of the fertilizer. The findings were supported by compositional analysis using Fourier Transform Infrared spectroscopy (FTIR).

Abstract: Recently, using ceramsite to treat wastewater has received wide attention. In this tudy, the ceramsite packing material was modified to make it more ready for bacteria attachment and improved its waste-water treatment efficiency by magnetic field. In addition, the optimal percentage of the additive was obtained through the wastewater treatment experiments in a contact aeration bioreactors. The results showed that the optimal percentage of magnetic powder, polyvinyl alcohol, amylum, sodium bicarbonate, and expanded perlite was 7%, 3%, 2%, 5% and 10% respectively. And the performance of the modified ceramsite in the contact aeration bioreactors was compared with the packing which without magnetic powder, polyvinyl alcohol and amylum showed that the modified ceramsitethe had obviously advantages in terms of time it took for the reactors to attain the stable treatment, organic reduction rate and water retention.

Abstract: This study combines hydrophilic and soft Tencel^® fibers and low-melting-point polylactic acid (LMPLA) fibers by needle-punching and hot press processes to form moisture-retentive and comfortable Tencel^®/LMPLA composite nonwoven fabrics. Air permeability, water vapor transmission rate, softness, water content rate, and water loss rate tests are performed on the composite nonwoven fabrics. The experiment results show that when hot pressed at 130 and 150 °C, the Tencel^®/LMPLA composite nonwoven fabrics have good water absorption, water retention, and softness, which can be concluded as successfully moisture-retentive and comfortable Tencel^®/LMPLA composite nonwoven fabrics.