This paper presents the results of investigation carried out to improve the mechanical toughness of cement mortar. Toughness is a basic parameter which has to be improved in brick walls, concrete roads, machine foundations, dams etc. Materials fails due to an impact force and vibrations resulting in minor cracks and bonding failure between bricks, it leads to failure of the structure. In order to avoid the failure toughness has to be enhanced and this can be done by modifying the cement mortar. In this project recycled glass is used in the form of powder less than 45 μ m as replacement of cement. Also natural rubber latex is added as 20% replacement of water. Three mortar mix are considered, namely 1: 3, 1: 4, 1: 5. The compressive strength of mortar cubes, and flexural strength are done to determine the strength and toughness of the mortar. Results showed that fracture toughness increased to considerable amount.

In the present study, the effect of curing procedure on the compressive strength development of cement mortar and concrete incorporating ground granulated blast furnace slag is studied.The compressive strength development of cement mortar incorporating 20, 40 and 60 percent replacement of GGBFS for different types of sand and strength development of concrete with 20, 40 and 60 percent replacement of GGBFS on two grades of concrete is investigated. The compressive strength of cement mortar and concrete obtained at the ages of 3, 7, 28, 56, 90, 150 and 180 days. Tests results show that the incorporating 20% and 40% GGBFS is highly significant to increase the compressive strength of mortar after 28 days and 150 days respectively. The magnitude of compressive strength of mortar for standard sand is higher than the magnitude of river sand. Incorporating 60% BFS replacement is showing lower strength at all ages and water-cement ratio for both types of sand. The compressive strength of OPC concrete shows higher strength as compare to the GGBFS based concrete for all percent replacement and at all ages. Incorporating 40% GGBFS is highly significant to increase the compressive strength of concrete after 56 days than the 20 and 60% replacement. Among GGBFS based concrete 40% replacement is found to be optimum.

Cement concrete continues to be the pre-eminent construction materials for use in any type of civil engineering structure. Performance of these structures in terms of their strength and stability has withstood the test of time but the life span of the structures has become a matter of concern. This is on account of the environment becoming chemically ever more aggressive. The atmosphere is found increasingly laden with higher percentages of Sulfur Dioxide, Carbon Dioxide and Chlorides. Oxides of Sulfur are injurious to concrete while Chlorides are harmful to the reinforcing steel. As a consequence of these, the life-span of the reinforced concrete structures have got compromised significantly from its original estimated life of about ninety years. The role of Sulphate ions in causing deterioration of concrete has been investigated intensively. Based on the literature available, the present paper discusses this aspect with particular attention to the use of blended cement in recent times with the influences of the parameters related to the Sulphate resistance of cement concrete and mortar.

In the last decades, the development of nanotechnology has been rising and nanomaterials have been widely used in combination with many traditional materials. The prominent chemical and physical properties of nanomaterials enable them to play an important role in various applications such as modifying the structure of materials, improving the properties of composites, and manufacturing new multifunctional products. Many studies have been carried out on the effect of nanoparticles on concrete performance and most of them demonstrated the improvement of concrete properties. There are a lot of studies on the effect of nanoclay on cement composites. However, there are little researches on the halloysite nanotube (HNT) effect, as subcategories of nanoclay, on the properties of cement composites. Halloysites are a kind of mineral clay which are often produced by air-induced erosion or by thermal transformation of ultramafic rocks, volcanic glasses, and pumice. They are chemically similar to kaolinite but, unit layers in halloysites are separated by a monolayer of water molecules. In general, halloysites have different shapes and exist in the plate, spherical, and tubular forms. The tubular structure is the dominant form of halloysite in nature. Chemically, the outer surface of the HNTs has properties similar to SiO2 while the inner cylinder core is related to Al2O3. Due to the tubular geometry, HNTs like carbon nanotubes could be classified as one-dimensional nanoparticles. Halloysite can grow into long multi-walled tubules, which morphologically resemble to multi-walled carbon nanotubes. In terms of dimensional characteristics, HNTs have an external diameter of about 30 to 190 nm, an inner diameter of about 10 to 100 nm and a length between 3 to 30 μ m. Halloysite characteristics could be sum up as high length to diameter (L/D) ratio, high specific surface, large pore volume, low density in surface, and pozzolanic properties. Mechanical properties of HNTs could make them an ideal reinforcing additive to improve the mechanical properties of cement composites. In addition, due to the nano scale size of HNTs, they can play the role of filler and make a denser and stronger microstructure. Therefore, in this research, the effect of HNTs on the performance of cement mortar was evaluated and the workability and permeability of mortar samples containing 3% halloysite nanotubes were presented. The results indicated an increase of more than 28% of electrical resistance, a decrease of approximately 26% of water absorption rate, 23% reduction in water repellent, a decrease in the workability, and an increment in the rate of hydration of cement mortar due to the incorporation of 3% halloysite nanotube. These results indicate that halloysite nanotubes can be used as an appropriate nanoparticle to improve the properties of cementitious composites. The pozzolanic properties of HNTs enable them to decrease the permeability of cementitious matrices. This could lead to an enhancement in the durability of cementitious matrices.

One of the latest and most significant topics in civil engineering, materials science, and rock mechanics is the use of natural and mineral aggregates as a partial replacement for cement or aggregates in cement mortar or concrete. This approach aims to enhance the properties of concrete or mortar by incorporating these materials. One such material that has recently gained attention is Expanded Vermiculite. Given its insulating properties against waves and heat, the use of mortar with expanded vermiculite additives has become increasingly common to improve efficiency. However, a comprehensive study on the mechanical properties of this type of mortar has not yet been conducted. The present study investigates the mechanical properties of cement mortar containing expanded vermiculite, including uniaxial compressive strength, cohesion, internal friction angle, tensile strength, water absorption, and P-wave velocity. This research was carried out in the Rock Mechanics Laboratory at Tarbiat Modares University. The results indicate that with increased vermiculite content, most mechanical parameters (except for water absorption) significantly decrease.

Microscopic studies has shown that adjacent to the interface between cement paste and aggregate, there exists an area with high porosity and low binding compounds that is referred to as interfacial transition zone (ITZ). ITZ in concrete and mortar imposes a number of negative effects, including flexural and compressive strengths reduction and permeability enhancement. That’s why many research attempts have been devoted to limit ITZ and its negative effects. The present study investigates the possibility of utilizing fine Portland cement (PC) clinker as a reactive aggregate in mortar for the same purpose. For this, natural quartz sand in normal mortar (NM) was totally replaced with PC clinker of the same particle size distribution and the most important engineering properties of the new mortar referred to as Reactive Aggregate Mortar (RAM) were measured and compared with NM as control. The results of compressive strengths measurements represented 65% and 21% increases at curing ages of 7 and 90 days, respectively, for RAM compared to NM. Chloride penetration depth in RAM displayed reductions by about 33% and 26% after 14 and 28 days of exposure, respectively. The effect of PC clinker reactivity on the microstructure and size of ITZ was studied by using scanning electron microscopy.

The role of cement fineness in the process of hydration and development of compressive strength in the early ages of cement-based materials is irrefutable and it requires that its effect be investigated by predicting models. Therefore, an extensive study including 640 cement composition (1920 cement mortar specimens) from a cement factory with different percentages of raw materials feeding to the cement kiln including SiO2, Al2O3, Fe2O3, CaO, MgO, SO3, K2O, and Na2O were used to predict the 7-day compressive strength of cement mortar by artificial neural network (ANN). To investigate the effect of cement fineness, two models have been developed in two states of with and without fineness effect. Results confirmed the significant role of cement fineness as an input parameter in the performance of predicting model. The findings of this research can be used in cement production facilities in order to reduce the laboratory costs.

The role of cement fineness in the process of hydration and development of compressive strength in the early ages of cement-based materials is irrefutable and it requires that its effect be investigated by predicting models. Therefore, an extensive study including 640 cement composition (1920 cement mortar specimens) from a cement factory with different percentages of raw materials feeding to the cement kiln including SiO2, Al2O3, Fe2O3, CaO, MgO, SO3, K2O, and Na2O were used to predict the 7-day compressive strength of cement mortar by artificial neural network (ANN). To investigate the effect of cement fineness, two models have been developed in two states of with and without fineness effect. Results confirmed the significant role of cement fineness as an input parameter in the performance of predicting model. The findings of this research can be used in cement production facilities in order to reduce the laboratory costs.

In many construction projects, cement mortar is affected by wetting-drying cycles, often due to factors such as varying rainfall, evaporation, changes in level of water in reservoirs. Alternative interactions between water and mortar affects the physical and mechanical properties of cement mortar and accelerates its erosion. Therefore, evaluating the effect of wetting-drying cycles on the physical and mechanical properties of cement mortar seems to be essential. For this purpose, a number of cylindrical and disc shaped samples were prepared. Samples were prepared for uniaxial compression test, Brazilian test, effective porosity test, and also determining longitudinal wave velocity. Samples were examined in cycles 0, 1, 5, 10, 15, 20 and 25. In each cycle, the samples were saturated in water for 24 hours and then dried at 105 ° C for 24 hours; then the samples were cooled at room temperature and finally examined. After cycle 25, uniaxial compressive strength, Brazilian tensile strength, modulus of elasticity and longitudinal wave velocity decreased by 37. 96, 36. 72, 35. 44 and 8. 1 percent, respectively; while porosity increased by 7. 6 percent.