Papers by Keyword: Alkali Activator

Abstract: This paper presents the development of a binder from coal ash and rice husk ash for manufacturing hollow blocks. Experiments were conducted to determine the compressive strength of the coal ash and rice husk ash as binders using cylindrical specimens at different curing periods. The mixture proportion with the highest compressive strength in the experiment was adopted in making the 4” hollow blocks. The compressive strength of the hollow blocks with the coal ash and rice husk ash binder was also determined at different curing periods.Cylindrical specimens with four different alkali activators were made and subjected to compression testing on the 3rd, 5th, and 7th day of curing. The mean compressive strength of the cylindrical specimen with all sodium hydroxide activator (RS0CS0) after 7 days curing is 2.54 MPa as compared to 3.05 MPa with the 2.5 sodium silicate to sodium hydroxide ratio (RS1CS0). As the amount of sodium silicate from rice husk was doubled (RS2CS0), the average compressive strength of the 7 days old cylindrical samples increased from 3.05 MPa to 3.49 MPa. Meanwhile, the 7th-day compressive strength of the cylindrical specimen with commercial silica (RS0CS1) was 5.5 Mpa.Hollow blocks were also manufactured based on the material proportion that utilizes RHA with the highest compressive strength or the design mixture RS2CS0. These blocks have a mean compressive strength of 1.22 MPa on the 3rd day, 1.88 MPa on the 7th day, and 2.7 MPa on the 14th day of the curing period.

Abstract: Lightweight materials applied in construction field were prepared using waste iron mine tailings (WIMT) as raw materials, the commercial silicate cement (CSC) as cementing agent, NaOH as the alkali activator, and triethanolamine lauryl sulfate (TLS) as foaming agent via foam-gelcasting method. The effects of water/cement (W/C) mass ratio (0.6-1.0), addition of NaOH (0-0.15wt%) and foaming agent (0-0.3vol%) on the porosity, bulk density, and mechanical properties of the iron mine tailing-based lightweight materials were studied. The results showed that the mechanical properties of iron mine tailing-based lightweight materials were improved by adding NaOH, the as-prepared materials had a 7-day compressive strength of 5.18 MPa, porosity of 51.40%, bulk density of 1.73 g/cm³ and thermal conductivity of 0.193 W・(m^-1 K^-1) when the W/C ratio was 0.8, the mass ratio of WIMT/CSC/NaOH 1.85:1:0.15, and foaming agent content 0.3vol%.

Abstract: The rheological behaviour of alkali-activated materials prepared by activation of a brick powder by alkaline solution (alkali + water glass) is described. The influence of the composition of activation solution (NaOH vs. KOH, varied silicate modulus) on the flow properties (yield stress, consistency coefficient, fluidity index) and the evolution of the elastic modulus (G ́) and the viscous modulus (G ́ ́) over time were studied. The rheological characterization was completed by frequency sweep tests with the aim of investigating the material behaviour more in detail. The results show that the pastes are thixotropic suspensions with very low yield stress. The potassium activator decreases the yield stress and viscosity of the pastes and retards the polymerization kinetic. The brick pastes become more rigid and more viscous with increasing silicate modulus. This also leads to an acceleration of gel formation in brick pastes.

Abstract: Geopolymer is an aluminosilicate material that can be prepared from thermal activation of solid material containing alumina and silica as precursor and alkali activator solution. The precursor is an eco-friendly material and has a potency to replace Portland cement (cementless material). In this work, cementless geopolymer mortar was prepared by mixing fly ash as main precursors, red mud, and electric arc furnace dust slag, followed by addition of activator solution containing sodium hydroxide solution and waterglass. X-ray diffraction and Fourier transform infra-red spectroscopy demonstrated the formation of albite in geopolymer mortars, indicating that geopolymer mortars have been successfully formed. The best compressive strength of mortars was 72.80 MPa achieved by using fly ash and red mud with NaOH 12M under ambient curing.

Abstract: According to the recent community-based structures enlargement, specification, and diversification. It needs appropriate construction materials in terms of intensity and environmental aspects. Thus, in manufacturing the cement using micro limestone powder that is main material. It is also expected to save energies and reduces CO₂, by using the blast furnace slag and fly ash which are mitigated environmental load construction materials that emerged. In this research, the durability aspect tries to be grasped considering the chemical property according to the coherence of the hydration product. Consequently, the compressive strength was measured over 30Mpa on 3rd. In addition, according to the content of the limestone powder, the setting time is promoted. It has the feature expanded in the length change. And it is determined because the possibility of replacing the existing for construction material such as it is measured compared with the time to use the portland cement usually that flexural strength is high with the age 7 days ago, so it is sufficient.

Abstract: The cement-free binding material, namely geopolymer, is a novel binding material made from solid waste such as fly ash and slag activated by the alkali. In this research, orthogonal tests were carried out on 20 x 20 x 20mm cube paste specimens cured at room temperature to explore the rules of influence factors according to the compressive strength for 3d, 7d and 28d. The results revealed that the ratio of fly ash/slag is the most significant factor, the ratio of water/ (fly ash+ slag), the modulus of alkali activator and the dosage of desulfurized gypsum also play great role in strength development of the binder. The compressive strength of the specimens can be obtained to 65.0 MPa and 51.21MPa at maximum for 28d when the ratios of fly ash/slag are 30/70 and 40/60 respectively.

Abstract: The paper studied effect of blast-furnace slag on rheology and hydration properties of blended cement paste. Rheology of blended cement paste with polycarboxylic series (PCS) and sulphamate series (SMS) superplasticizer is tested, appraised effect degree of the dosage and fineness of slag in blended cement by saturation dosage of superplasticizer, fluidity and gradual loss of fluidity. For hardened paste, the study tested development of strength and hydration products, activation effects of gypsum and sodium sulfate, analyzed macro mechanical behavior and micro structure of blend cement made from slag.

Abstract: As a basic stage for developing new construction material utilizing sewage sludge ash, this study is identified by specific material characteristics through XRD, SEM, uniaxial compressive strength, porosity, and the drying shrinkage by manufacturing mortar with sewage sludge ash. The average drying shrinkage of sewage sludge ash mortar aged 7 days showed 88% of the strain of the one aged 28 days. The porosity of sewage sludge ash mortar was about 7~10%. The more quick lime and blast furnace slag were added, the less porosity appeared.