Experimental and Environmental Analysis of High-Strength Geopolymer Based on Waste Bricks and Blast Furnace Slag

The rationalization of material flows, together with the utilization of waste raw materials for the production of alternative binders, became a very attractive topic during the last decades. However, the majority of designed materials can be used as a replacement for low-performance products. In this work, the waste materials (brick powder and blast furnace slag) are valorized through geopolymerization to design high-performance material as an alternative to high-performance concrete. Designed mixtures activated by sodium silicate and waste-originated alkali solution are characterized by the meaning of the chemical and mineralogical composition, evolution of hydration heat, and mechanical strength test. To contribute to the understanding of the environmental consequences and potential benefits, the carbon footprint and embodied energy analysis are provided. Obtained results highlight the potential of end-of-life bricks for the design of high-performance composites if mixed together with more reactive precursors. Here, even values over 60 MPa in compressive strength can be achieved with the dominant share of low-amorphous brick powder. The higher crystalline portion of brick powder may lead to the reduction of drying shrinkage and preservation of flexural strength to a greater extent compared to used slag. Performed environmental analysis confirmed the CO₂ emission savings; however, the embodied energy analysis revealed a huge impact of using alkaline activators.

Evaluating the Feasibility of Using Brick Powder and Clay Powder in Cement Replacement

The cement industry generates very large amounts of CO₂ into the atmosphere. In recent years, there has been a search for alternative cementitious materials and micro-fillers that could partially or fully replace cement in cement composites without compromising their durability. This paper investigates the possibility of using brick powder (BP) and clay powder (CP) as a partial replacement for cement (up to 20% by weight) in cement paste. The raw materials were characterized, and the physical and mechanical properties of the modified cement pastes were studied, as well as their resistance to a short-term thermal shock at 250 °C. The study was supplemented by intelligent modelling of compressive strength using the support vector machine (SVM) algorithms. The results indicated a significant increase in tensile strength (up to 100%) and an increase in thermal resistance of cement pastes modified with BP and CP. The proposed SVM model had high accuracy (R² = 0.90), indicating its suitability to predict the compressive strength of the modified cement matrix. This study complements the knowledge in the field of inter alia, the effect of a short-term thermal shock at elevated temperature on the properties of BP and CP modified cement paste, and the effect of BP, which, due to its grain size, plays more the role of a microfiller than a pozzolanic additive.

A comparative study of red brick powder and lime as soft soil stabilizer

Background: The role of soil in building construction is to support the loads above it. Different types of soil with poor mechanical properties require more attention. Therefore, more effort is needed to stabilize the soil by improving its properties. These improvements are intended to modify soil properties to improve engineering performance, such as strength, decrease in compressibility and permeability. This study aimed to compare the potential of lime and brick powder as stabilizers based on the California Bearing Ratio (CBR) values. Soil stabilization can be defined as modifying the soil properties by chemical or physical means to improve its engineering efficiency. The main objectives of stabilizing soil are increasing its bearing capacity, resistance to weathering processes, and permeability. Methods: This work did laboratory tests with disturbed and undisturbed soil samples. The proportions of lime or red brick powder additives are 0%, 5%, 10%, and 15% of the soil sample. From the results of the laboratory tests, the soil type obtained is MH (low plasticity silt) as per the Unified Soil Classification System (USCS). Results: This study showed that soft soil could be improved by adding lime and red brick powder as a soil stabilizer. In both soaked and unsoaked CBR tests, there was an increase in the CBR value for each proportion of the mixed additives. However, the red brick powder addition (15%) has significantly increased the CBR value. Conclusions: The soil sample mixed with 15% red brick powder had the highest Maximum Dry Density (MDD), about 5.5% over untreated soil. The increment of lime to 15% has increased the CBR soaked by 61% in relation to untreated soil. The increment of red brick powder to 15% has increased the CBR unsoaked by 73% in relation to untreated soil.

Properties and Strength Prediction Modeling of Green Mortar with Brick Powder Subjected to a Short-Term Thermal Shock at Elevated Temperatures

The cement industry is responsible for 8% of global CO₂ production. Therefore, a clear trend has been observed recently to replace to some extent the main binder of cement composites with environmentally friendly or recycled materials with a lower carbon footprint. This paper presents the effect of brick powder (BP) on the physico-chemical and mechanical properties of cement mortars. The effect of a short-term thermal shock on morphology and strength properties of green mortars was investigated. BP addition caused increase in porosity and decrease in compressive and flexural strength of mortars. The best results were obtained for samples with 5% wt. BP addition. Above this addition the strength decreased. The mechanical performance of the samples subjected to thermal loading increased compared to the reference samples, which is the result of a process called as the “internal autoclaving”. The BP addition positively affects the linear shrinkage, leading to its reduction. The lowest linear shrinkage value was achieved by the mortar with the highest BP addition. An intelligent modeling approach for the prediction of strength characteristics, depending on the ultrasonic pulse velocity (UPV) is also presented. To solve the model problem, a supervised machine-learning algorithm in the form of an SVM (support vector machines) regression approach was implemented in this paper. The results indicate that BP can be used as a cement replacement in cement mortars in limited amounts. The amount of the additive should be moderate and tuned to the features that mortars should have.

The Effect of a High Amount of Micro-Fillers on the Long-Term Properties of Concrete

Concretes in which a large portion of fine natural aggregate is replaced with inert mineral powders would offer both economic and ecological benefits for the concrete industry, and they represent eco-friendly materials. Moreover, using the powders having potential pozzolanic effect could have positive extra effect on the properties of concrete. This paper analyses the impact of a high dosage of three kinds of micro-fillers (brick, concrete and glass powders) on the properties of concrete over a three-year period. Microfillers were applied as 40% replacement of 0/4 aggregate by volume. Samples having high dosage of micro-fillers and thus a higher binder volume achieved excellent values of both compressive (from 31 to 48 MPa in 28 days, and from 67 to 93 MPa in three years) and flexural strength (from 6.3 to 8.4 MPa in 28 days, and from 7.1 to 11.1 MPa in three years). Both samples with brick powder and concrete powder achieved the biggest strength values; however, due to better performance in durability parameters (capillary water absorption coefficient and density), sample prepared with glass powder can be identified as having the biggest potential for intended use.