Compressive strength prediction of Portland cement concrete with age using a new model

Based on the existing experimental data for compressive strength values of different concrete mixes, a statistical analysis for the gathered data was conducted. The analysis revealed a model for predicting the compressive strength of concrete mixes at any age with the help of two constants (A) and (B) that are considered as a characteristic property for a concrete mix. The constant (A) is introduced as a rate of strength gain constant whereas, (B) is introduced as grade of strength constant. Once the values of constants (A) and (B) are defined for a concrete mix, the compressive strength at any age could be simply predicted without collecting data at that age. The values of (A) and (B) could be determined by one of two methods. Solving two simultaneous equations at two different ages while performing either design or trial concrete mix is a method that could be used to define the two constants. Other method is based on concrete strength at 28-day age. The proposed model was studied for different concrete mixes. The study covered some parameters including the influence of, mineral admixtures as a partial replacement of cement, metakaolin, nano silica fume, curing in water or lime and the effect of curing temperature. The analysis reveals that mixes containing no admixtures, mixes containing silica fume and cured at normal temperature, mixes containing nano silica and cured in water are following with high accuracy the proposed model

Fracture properties of self-compacting fiber-reinforced concrete

Self-compacting concrete (SCC) is an innovative concrete that does not necessitate vibration for placing and compaction. Nineteen concrete mixes were investigated including a control mix without fibers as well as eighteen SCC with fibers (SCFRC) mixes. Three types of fibers (polypropylene, glass and steel) were used. Slump flow, L-box, V-funnel as well as column segregation tests were conducted to assess the fresh properties. Whereas, compressive, splitting tensile and flexural strengths were measured to assess the hardened properties of SCFRC. Three point bending tests were performed for the purpose of assessing the fracture properties of SCFRC. Test results showed that the inclusion of fibers to produce SCFRC mixtures remarkably enhanced the fracture properties including fracture energy (Gf) and fracture toughness (K1c). Inclusion of steel fibers with 2% volume fractions showed an improvement with 26.9 times for Gf over the control mix. Whereas, 104% increase in K1c was recorded for the same mix over the mix without fibers. Adding fibers to SCC to produce self-compacting fiber reinforced concrete (SCFRC) will expand its advantages. However, the application fields still need to understand the properties of SCFRC

Properties of Portland cement concrete cast with magnetized water: a review

The water utilized in concrete manufacture plays an important role within the concrete mix, beginning from controlling the process of hydration of cement, besides appropriate curing to achieve the required strength, not to mention controlling the workability and durability of the concrete structure. The utmost significant challenge for concrete technology is to improve the properties of concrete. Nowadays, the engineering field needs to produce structures in harmony with the concept of sustainable development through the utilization of high-performance materials with an eco-friendly impact that is produced at a low-cost. The magnetic water (MW) provides one of the utmost towards this objective. The cost of magnetizing water is low because of the simple instruments used and the cost can be adapted to the scale of the work. In the last two decades, a new technology, so-called MW technology, has been extended to use in concrete manufacturing. Therefore, currently, the researchers are interested in the use of MW in the manufacture of cementitious materials helping to rationalize the cement usage and reducing reliance on chemical additives that have a negative environmental impact. Consequently, this paper presents the effect of the magnetization process in the structure of water molecules, the main properties of water. Additionally, the effect of using MW on the fresh and mechanical properties, as well as the durability characteristics and performance of cementitious materials have been reviewed. Moreover, the factors that affect the magnetization process of water, which highlighted discuss in this study. The results revealed that using MW significantly enhances the flowability and the characteristic strengths of cementitious materials as well as the durability properties