Preparation, Characterization and Performances of Powdered Polycarboxylate Superplasticizer with Bulk Polymerization

Strength, durability, and economic analysis of GGBS-based geopolymer concrete with silica fume under harsh conditions

Geopolymer concrete (GPC) offers a sustainable alternative by eliminating the need for cement, thereby reducing carbon dioxide emissions. Using durable concrete helps prevent the corrosion of reinforcing bars and reduces spalling caused by chemical attacks. This study investigates the impact of adding 5, 10, and 15% silica fumes (SF) on the mechanical and durability properties of GPC cured at 60 °C for 24 h. In the research, concrete specimens were submerged continuously for 62 days in four different chemicals: 6% sodium sulfate, 6% sodium chloride, 2% sulfuric acid, and 2% hydrochloric acid. The study assessed the effects of chemical exposure on concrete properties by examining water absorption, sorptivity, and compressive strength loss in GPC specimens. Maximum compressive strength, split tensile strength, and flexural strength of about 48.35 MPa, 4.91 MPa, and 5.01 MPa are achieved after incorporation of 10% SF in GPC after 28 days of curing. Results indicated that GPC with a significant dosage of SF (10%) improves its mechanical and durability properties. The maximum rebound number and ultrasonic pulse velocity are achieved after 90 days of curing with a 10% dosage of SF. Moreover, an economic analysis was conducted to confirm the economic viability.

Effect of Density of Acrylic Acid Ester on Sulfonate-Modified Polycarboxylate Superplasticizers on Cementitious Systems

To tackle high viscosity in fresh concretes, especially high-performance concrete, the research of polycarboxylate superplasticizers (PCEs) is relevant. By designing the molecular structure of PCEs, problems such as pumping difficulties in high viscosity of high-performance concrete can be solved. Therefore, in this paper, a suite of novel viscosity reducing PCEs containing sulfonic acid groups and different acrylate densities were synthesized on the basis of inventive molecular structure design, and characterized to determine the predicted structure. The maximum adsorption, the best fluidity, and the Minimum zeta potential value can be seen for PCEs with a small number of ester groups (PCE-MA0.5) due to the combination of the rigidity of its backbone and the density of the adsorption groups. Moreover, the investigation of working mechanism showed the introduction of ester groups can significantly reduce viscosity, but also reduces the adsorption capacity. This research aims to propose a feasible method for synthesizing PCE with superior processability and viscosity reduction capability in cement and concrete.

Technical optimization and life cycle assessment of environment-friendly superplasticizer for concrete engineering

With the rapid development of the construction industry, it is necessary to synthesize environment-friendly functional polymers, especially when developing "green" construction industry types. Herein a novel solid-state polycarboxylate superplasticizer (PCE) with low energy-consumption was designed and synthesized. In industrial application, solid-state PCE has exhibited better cement paste fluidity and concrete slump compared to liquid-state PCE. A life cycle assessment (LCA) of the PCE synthesis, the packaging materials used, and the transportation of the PCE were conducted based on the ReCiPe method. The results indicated that liquid-state PCE has a far greater environmental impact at >60% than solid-state PCE, which is less significant at <40%. The inventory data that are associated with the production of the new polymer are disclosed for the first time to enrich the related database in this field. This study demonstrates the optimization of the state and synthesis technique of a functional polymer, improving the performance and lowering the environmental impacts involved in producing the polymer, while reducing the risks to human health and protecting the ecosystem at the same time.

Reduction of Fractionation of Lightweight Slurry to Geothermal Boreholes

When designing the cement slurry for casing string cementing in geothermal boreholes, the appropriate thermal conductivity is selected. In the zone of geothermal water, where thermal energy is collected, cement slurry is used, from which the cement sheath has high thermal conductivity. On the other hand, the remaining part of the opening is sealed with slurry, from which the cement sheath will reduce thermal energy losses through appropriate thermal insulation. Cement slurry with appropriate thermal insulation includes light insulating materials. However, the use of such additives is very problematic as they are fractionated due to their low density. Therefore, measures should be taken to prevent fractionation of the cement slurry for sealing geothermal boreholes. This article presents the results of research on fractionation of cement slurries for sealing geothermal boreholes. 12 slurries were used for the tests. Six of them are based on class A cement, and six based on class G cement. This action shows the differences in fractionation depending on the binder used. However, the main area of research is determining the effectiveness of counteracting fractionation by the means used for this purpose. As a result of the conducted works, a very good improvement of the cement slurry stability is obtained after the introduction of xanthan gum, as well as filtration perlite. These measures prevent fractionation, so that the cement slurry has a homogeneous structure, and the cement sheath provides the required thermal insulation in the geothermal well.

Performances and working mechanism of a novel polycarboxylate superplasticizer synthesized through changing molecular topological structure

A novel star-shaped polycarboxylate superplasticizer (SPCE) was synthesized through a simple two-step method. ¹H Nuclear Magnetic Resonance (¹H NMR) and Infrared Spectroscopy (IR) measurements were used for structural characterization. SPCE and comb-shaped polycarboxylate superplasticizer (CPCE) with same molecular weights were designed and synthesized. The cement paste containing SPCE exhibited better fluidity, fluidity retention, water reduction, 25% lower saturated dosage of PCE, 10% longer setting time, lower hydration heat, more delayed hydration heat evolution and lower amount of hydration products at early ages. Furthermore, the adsorption behavior of SPCE and CPCE in cement pastes and the zeta potential were investigated, and then the working mechanism of SPCE was theoretically explained. It is interesting that changing topological structure from comb-shape to star-shape can achieve the optimization of dispersion effect, and further improve the working effectiveness. The aims of this study are to provide a new avenue to synthesize superplasticizer with novel structure achieving the chemical diversity of superplasticizer structure, and to verify the contribution of optimizing molecular shape. This new type of superplasticizer can be used as a rheology modifying agent in fresh cement-based materials.