Papers by Keyword: Cement-Based Material

Abstract: At present, the products of polycarboxylate superplasticizer (PCE) mainly present liquid state. Compared with liquid PCEs, solid PCEs have not only high storage stability, but also high water-reducing rate. Based on acrylic acid (AA) and isobutenyl polyethylene glycol (IPEG) as the main materials, a series of solid PCEs were synthesized under anhydrous condition by employing ammonium persulfate (APS), benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN) and azobisvaleronitrile (ABVN) as initiators, and the effects of different initiators on the application performances of these solid PCEs were also investigated. The molecular characteristics of the synthesized products were determined by Infrared Spectroscopy (IR) and molecular weight measurements to confirm the expected structure. The fluidities, dispersions and micro-observations of cement pastes containing solid PCEs were evaluated. For both liquid PCE and PCE-ABVN, the average particle size reduced from 2373nm to 1147nm. The results showed that the paste fluidity, concrete slump and retentions were significantly enhanced when using ABVN as initiator, with the initial slump up to 225mm. This initiator had high initiating efficiency, exhibiting broad application prospects.

Abstract: Nano-size fillers (ultrafine silica fume (USF) or/and multi-walled carbon nanotube (MWCT)) were incorporated into cement matrix to fabricate nano-fillers reinforced cementitious materials (NFRCs) with surfactant ultrasonic dispersion and subsequently mix cast process. The flexural and compressive strengths of four groups NFRCs with varied nano-filler loading were comprehensively investigated. Results show, there are positive effects on the flexural and compressive strength of NFRCs with nano-fillers loading, especially when USF and MWCT are incorporated simultaneously, and the correspondent maximal flexural and compressive strength can increase by above 17%, 28% with respect to the baseline, respectively. The pozzolan infilling effect of USF and the crack-bridging effect of dispersed MWCT result in the dense and integrated network microstructures of cured NFRC.

Abstract: Nowadays, interest in developing environmental friendly construction material was increased. As the result, many researches have been done to make use of waste material for engineering purposes. This paper present the results of laboratory experiments on the potential of raw rice husk (RH) cement mortar with addition of foam as drainage material. Mechanical properties which are compressive strength, density, water absorption and porosity have been investigated in order to identify the potential of this material to function as drainage material. Total of eight set of sample were tested to determine those properties. Aqueous foam generated from chemical based foaming agent was used in this study to enhance the drainage ability and also reducing the density of the cement based mixture. More over to simulate the real application at site, an infiltration model was developed to determine the drainage and infiltration characteristic of this material. The permeability of the sample used in the infiltration model has been tested using constant head test to verify the validity of the infiltration model. From the result obtained, it can be concluded that the compressive strength and density of sample decreases with percentage of raw rice husk used while the additional of foam has further reducing the compressive strength and density. Both water absorption and porosity showing the opposite trend compared to the compressive strength. This drainage material can be pre-designed between 1.60N/mm² – 10.12 N/mm² for compressive strength, 1392kg/m³ - 1841kg/m³ for density, 21% - 34% for water absorption and 31% - 42% for porosity. From the result of infiltration model, it was observed that this material having good drainage ability with the permeability of 15% foamed rice husk sample is 1.57x10^-3.

Abstract: Waste tyre caused disposal problem in country all over the world. A lot of research has been done to make use of recycled tyre rubber to minimize waste tyre disposal problem. Recycled tyre rubber has been widely used for civil engineering application such as lightweight concrete and asphalt pavement. However only a few study focused on the development of material using recycled tyre rubber as drainage material for geotechnical purposes. This paper presents the experimental on properties of cement-based material consisting recycled tyre rubber. Specimens were prepared by incorporating different percentage of shredded rubber tyre with mortar. Summation of ten (10) mixes has been investigated to determine the compressive strength, density, porosity and water absorption. From the results, it is concluded that the higher percentage of shredded tyre rubber used, will decreased the compressive strength and increased the porosity and of the material.

Abstract: Most of the rice husk is disposed with no further concern and this has caused waste disposal problems. Burning rice husk can cause health and environmental problem. Rice husk ash has been widely used for concrete technology application as additive in concrete mixture. However there is lack of study on the usage of raw rice husk. This paper presents the experimental on the properties of cement mortar consisting raw rice husk which focused on the porosity and density. Specimens were prepared by incorporating different percentage of rice husk with mortar. Summation of 10 mixes has been investigated to determine the compressive strength, density, porosity and water absorption. As the main purpose of the rice husk cement mortar is for drainage material, the main characteristics needed are porosity and lightweight. From the results, it is concluded that the higher percentage of rice husk used, will decreased the compressive strength and density and increased the porosity of rice husk cement mortar.

Abstract: The volume deformation test, differential scanning calorimetry and chemical titration technique were used to experimentally research the interventions of retarders on the free autogenous volume deformation of cement paste doped with CaO expansion clinker at different ages systematically, as well as the hydration rate and hydration process of CaO expansion clinker. Two types of retarders were used as following: sodium gluconate and sodium citrate. The experimental results show that the two retarders can delay the hydration process of CaO expansion clinker, slow down its hydration rate both in pure water and cement paste. At the same time, the free autogenous volume deformation of cement paste was increased. In this sense, the use of retarders is favorable to improve the expansion efficiency of CaO expansion clinker.

Abstract: PVA fiber reinforced cement-based composite is a new high-performance cement-based composite material, which usually manufactured with PVA short fibers (does not exceed 2.5% vol.) and cement-based matrix. It has a significant strain-hardening characteristic and excellent crack controlling ability. Its ultimate tensile strain is up to 3% and crack width is not exceed 100μm. PVA fiber reinforced cement-based composite can be utilized to fabricated high energy absorption opponents, such as protective shield, seismic joint, impact-resistant site, etc. In this paper, the basic mechanical properties of PVA fiber reinforced cement-based composite has been tested and verified first. Then the impact resistance of PVA reinforced cement-based composite has been investigated via drop weight impact test, and compared with ones of plain concrete and steel fiber reinforced concrete with the same strength grade. Through analyzing the test results, it is concluded that PVA reinforced cement-based composite’s impact energy absorption is 48 times than plain concrete, and 9 times than steel fiber reinforced concrete respectively. The impact numbers of PVA reinforced cement-based composite is slightly lower than steel fiber reinforced concrete, but its impact absorption energy after initial cracking is 15 times than steel fiber reinforced concrete. In conclusion, PVA reinforced cement-based composite is an excellent impact material.

Abstract: For the volume expansive of cement-based materials subjected to sulfate attack, based on microporous mechanics, the model of representative volume element (RVE) is established to analyze the distribution of microcosmic expansive stress in RVE. By homogenization method, the macroscopic equivalent stress of RVE is analyzed. The results show: on the microcosmic scale, the stress of internal sphere in RVE in all directions is compressive, and the radial stress of spherical shell is compressive, but the hoop stress is tensile; on macroscopic scale, the radial equivalent stress is compressive, the hoop equivalent stress is tensile.

Abstract: Carbonation is a common influence of cement-based material. And the accelerated carbonation is used in material property modify. With the reaction in the material when carbonating, the carbon dioxide will be solidifying in the material, in the shape of precipitation of calcium carbonate filled the pore. But the ability of the carbon absorbing is unknown, in this paper, some cement-based building materials are took in test, including the aerated brick, cement tile, concrete, and cement mortar. In according to the results, it has found that the carbon absorbing ability is different, and with the carbon absorbing, the strength also increasing. The aerated brick is greatest and the condition of temperature, pressure and reaction time is lowest, which give a reference on the way of the greenhouse gas transform and reduced.

Abstract: The absorbing performance have been tested and analyzed by taking cement as matrix, blending material silica fume and culver zed fuel ash, graphite and carbon fibers, nanoTiO₂ and steel fibers for absorbing agent trial Sample, in the 8 ~ 18 GHz frequency band, the results indicate that silica fume and culver zed fly ash, nanoTiO₂ and steel fiber and composite cement which made of Absorbing material has good absorbing property. Graphite and carbon fiber and cement composite made of the effectiveness of absorbing materials. Blending material absorbing properties of cement-based materials, the impact must be considered together, not the more the better, when blending material exceeding a certain threshold, its ability of wave-transparent enhance while absorbing property will be reduced finally.