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Earth is probably the most eco-friendly building material. However, since earthen materials dissolve in water easily their application is limited. The presented manuscript aims to verify the usefulness of a one-part geo- polymer developed at BAM as a stabilizing agent for earthen mortars. The experimental study encompasses water-resistance, compressive strength, linear shrinkage, water vapour permeability and microstructural anal- ysis of the reference and the modified earthen plaster. The presented results show that the modification visibly affects the properties of the initial material providing its water-resistance.
Earth is probably the most eco-friendly building material. However, since earthen materials dissolve in water easily their application is limited. The presented manuscript aims to verify the usefulness of a one-part geopolymer developed at BAM as a stabilizing agent for earthen mortars. The experimental study encompasses water-resistance, compressive strength, linear shrinkage, water vapour permeability and microstructural analysis of the reference and the modified earthen plaster. The presented results show that the modification visibly affects the properties of the initial material providing its water-resistance.
Hydrophobic agents are one of the most commonly used means of prolonging the lifespan of cement-based materials. However, when water-repellent is added to the batch water it can interfere with cement hydration leading to deteriorated mechanical properties of the hardened material. To eliminate this drawback, a novel methodology of indirectly applying hydrophobic agents to cement-based materials is introduced. The presented approach uses super absorbent polymers (SAPs) as a delivery medium. SAP containing water-repellent is added to the fresh cement mixture, which ensures a gradual release of the admixture. The release is driven either by drying which generates moisture gradient or by compression of polymer particles by hydrates arising in their vicinity. Such mechanisms lead to a delayed dosage of the hydrophobic agent, which is when the partially hardened cement matrix is less vulnerable to interference compared to the fresh mixture. The effectiveness of the proposed methodology was verified in the extensive experimental program. Cement mortars of two water-to-cement ratios (0.4, and 0.5) were tested in terms of compressive strength, capillary absorption, and contact angle among others. Based on the obtained results it is concluded that the proposed methodology limits the negative impact of the hydrophobic agent on cement hydration. The mechanical performance of the samples modified with the indirectly dosed admixture is improved compared to the conventionally hydrophobized material in each analysed case. The results of isothermal calorimetry support the thesis. Additionally, the effectiveness of imparting hydrophobic characteristics to the cement matrix was as good as in the case of the conventional dosing. The mercury intrusion porosimetry, as well as thermogravimetric tests, were run to provide a deeper insight into the microstructure and composition of the modified material. Scanning electron microscopy was used to give a better insight into samples’ morphology. The novel methodology presented can also potentially be used
to dose other types of admixtures that can interfere with cement hydration.
Cementitious materials are often exposed to aggressive environments, which have a significant impact on their durability. Proper prediction of concrete corrosion helps to apply the right measures and technologies, to extend the service life of structures. Carbonation and cyclic freezing are recognized among the most common corrosive factors for concrete. Their progress is linked to the penetration of CO2 and water into the concrete structure. Due to the random arrangement of aggregates and cement paste, concrete is an inhomogeneous material. Therefore, the progress of carbonation and frost-induced damage should be treated as random variables with appropriate probabilistic parameters. Experimental studies on concrete carbonation and freezing were conducted in accordance with the standards EN 12390–12 and EN 12390–9. As observed in the experiments, the progress of carbonation and frost damage of concrete could be described by zigzag, not necessarily monotonic functions. Stochastic differential equations (SDE) were employed to predict the behavior of concrete exposed to elevated CO2 concentrations and cyclic freezing. The stochastic model consisted of a drift term, which described the general trend of concrete durability exposed to carbonation and frost cycles, as well as a diffusion term, which accounted for the stochastic features of inhomogeneous concrete microstructure. The Euler–Maruyama approximation with Milstein improvement was applied to model the realization of the stochastic changes in concrete microstructure/durability. The proposed approach predicted experimental results with high accuracy. The application of the Monte Carlo (MC) method with 100,000 SDE realizations allowed to calculate the statistical parameters of the processes, such as concrete carbonation and freezing cycles. The probabilistic parameters, such as expected values and standard deviations, calculated using the SDE_MC approach, were in good agreement with experimental results for both problems, i.e. decelerating concrete carbonation and accelerating concrete scaling.