Comparative study on the using of PEG and PAM as curing agents for self-curing concrete

There are many factors, which may affect on concrete quality. One of those is concrete curing. Self-curing concrete is the solution. It may produce by using chemical curing agents. The concept of those agents is to reduce the water evaporation from concrete. This research aims to study the effect of chemical curing agents on the behavior of self-curing concrete. Two different chemical curing agents were used to study the main mechanical properties of concrete. The main variables are; the type of curing agent (Polyethylene glycol "PEG400"–Poly Acrylamide "PAM") and its dosages. The results obtained in terms of compressive, tensile and flexure strength values. Test results showed that the self-curing concrete cured by each agent performed better in hardened properties compared to none cured concrete. Also, curing using the both agents together perform better than using each one individually

Recycled Aggregate Self-curing High-strength Concrete

The use of recycled aggregates from demolished constructions as coarse aggregates for concrete becomes a need to reduce the negative effects on the environment. Internal curing is a technique that can be used to provide additional moisture in concrete for more effective hydration of cement to reduce the water evaporation from concrete, increase the water retention capacity of concrete compared to the conventionally cured concrete. High strength concrete as a special concrete type has a high strength with extra properties compared to conventional concrete. In this research, the combination of previous three concrete types to obtain self-curing high-strength concrete cast using coarse recycled aggregates is studied. The effect of varying water reducer admixture and curing agent dosages on both the fresh and hardened concrete properties is studied. The fresh properties are discussed in terms of slump values. The hardened concrete properties are discussed in terms of compressive, splitting tensile, flexure and bond strengths. The obtained results show that, the using of water reducer admixture enhances the main fresh and hardened properties of self-curing high-strength concrete cast using recycled aggregate. Also, using the suggested chemical curing agent increased the strength compared to conventional concrete without curing

Behavior improvement of self-compacting concrete in hot weather

The main aim of this research is studying the effect of hot weather on the properties of self-compacting concrete and conventional concrete in both fresh and hardened state. Also, this research extends to improve the behavior of self-compacting concrete in hot weather. The main parameters were surrounding weather temperature (5°C, 20°C and 35°C), concrete materials temperatures’ (25°C, 50°C), curing temperatures (25°C and 50°C) and admixtures (using a retarder). Two stages were carried out to achieve the research aim. The behavior of self-compacting concrete compared to conventional concrete was evaluated in the first stage. Based on the first stage, attempts to enhance the concrete properties were evaluated in the second stage. Precautions on mixing and placing concrete in these climates are considered. Results are a drive in terms of; workability tests, compressive strength, splitting tensile strength, and flexural strength. Test results showed that self-compacting concrete behavior and strengths were better than conventional concrete. Slump test, J-ring and V-funnel test were used to evaluate the fresh properties of the self-compacting concrete. Drying shrinkage of self-compacting concrete in hot weather were also evaluated

Effect of self-curing admixture on concrete properties in hot climate conditions

Hot climates prevail in many regions of the globe. The average summer temperature of hot arid areas is in the range of 40-50°C with temperatures exceeding these values under direct solar radiation. Curing concrete in these regions may be challenging due to limited availability of suitable water for curing and/or rapid loss of curing water by evaporation. For many years self-curing admixtures were recommended as an alternative to water curing, however, limited studies have been conducted on their performance in hot weather conditions. In this investigation, the effects of a hot climate on the fresh and hardened properties of self-curing (SC) concrete and normal conventional concrete (NC) in hot weather were studied. A water- soluble polymer self-curing agent, polyethylene glycol (PEG 400), was added to the SC mixes. The testing parametersOwere concrete dry materials (25 or 50OC) and/or mix water temperatures (5, 20 or 35 C) at the time of mixing. NC samples were continuously water cured at 25 or 50 OC, whereas the SC ones were air cured at the same temperatures. The tested properties were workability, compressive strength, splitting tensile strength, and flexural strength. It was found that SC outperformed NC under varying conditions. The results could not be simply attributed to the retention of mix water by the self-curing admixture. A more comprehensive explanation for the observations is proposed

Flexural Strengthening of Reinforced Concrete Beams Using Valid Strengthening Techniques

This study aims to evaluate the efficiency of strengthening reinforced concrete beams using some valid strengthening materials and techniques. Using concrete layer, reinforced concrete layer and steel plates are investigated in this research. Experiments on strengthening beam samples of dimensions 100x150x1100mm are performed. Samples are divided in to three groups. Group “A” is strengthened using 2cm thickness concrete layer only (two types). Group “B” is strengthened using 2cm thickness concrete layer reinforced with meshes (steel and plastic). Group “C” is strengthened using steel plates. The initial cracking load, ultimate load and crack pattern of tested beams are illustrated. The experimental results show that for group A and B, the ultimate strength, stiffness, ductility, and failure mode of RC beams, with the same thickness strengthening layer applied, will be affected by the mesh type, type of concrete layer. While for group C, these parameters affected by the fixation technique and adhesion type

Performance of self-curing concrete at elevated temperatures

93-104Self-curing concrete (SCC) can cure without using any external curing methods. Polyethylene glycol (PEG) is one of the chemical agents which minimizes the loss of water and also attracts moisture from the atmosphere and helps in continuous curing of concrete. In this investigation, the effects of the coupled effect of elevated temperature levels of 200oC, 400oC and 600oC and heating periods of 2 h and 4 h as well as air and water cooling action on the compressive strength and splitting tensile strength of conventional-curing concrete and SCC are studied, respectively. Results show that self-curing concrete can be used at elevated temperatures considering its loss of strength. Air cooling is better for ordinary concrete but that may differ for SCC which may cool using water-cooling up to 400oC. Increasing elevated temperature and heating time decreases the values of residual strengths

Economical Reactive Powder Concrete Cast Using Available Materials in North Sinai, Egypt

In this research reactive powder concrete (RPC) was prepared using sand from North Sinai. The mechanical properties of locally cast RPC were investigated and evaluated by studying the effects of using different cement and silica fume contents and new steel fibers’ aspect ratios as reinforcement for RPC. Specimens’ preparation, curing regimes and testing procedures to evaluate the compressive strength, the modulus of elasticity, the indirect tensile strength and the flexural strength were discussed. A compressive strength of 154.5MPa, indirect tensile strength of 11.98MPa, modulus of elasticity of 45.1GPa and flexural strength of 30.26MPa have been achieved for reinforced RPC contains 800 kg/m3 cement content and silica fume content 30% of cement weight. The test results showed some improvements by increasing cement and silica fume contentsas well as adding steel fibers on the compressive strength, modulus of elasticity and indirect tensile strength

Effect of strengthening materials on the behavior of curved beams with openings

This study investigates the impact of openings on the behavior of arched beams and the effectiveness of different strengthening materials in enhancing their performance. The study involves three stages. The first stage focuses on the effect of openings on the behavior of curved beams. The second stage examines the effect of different strengthening materials, including carbon fiber sheets, glass fiber sheets, and steel plates, on the deflection and failure load in the presence of openings. In the third stage, Finite Element models are used to simulate the tested beams with different strengthening materials, and the differences between beams with and without openings are analyzed. The results show that the presence of openings negatively affects the ultimate load, deflection, and ductility ratio of arched beams. Regarding strengthening, beams strengthened with steel plates demonstrate a higher ultimate load, approximately 5.6% and 21% higher than beams strengthened with carbon fiber and glass fiber sheets, respectively. Moreover, the deflection of beams strengthened with steel plates is 6.4% and 8.9% higher than beams strengthened with CFRP and GFRP. The presented work is introduced to offer a valuable solution to some developed systems for controlling, repairing, and supporting structures