Curing of concrete involves maintaining satisfactory moisture content during early stages to develop the desired properties. Properly cured concrete has improved durability and surface hardness, and is less permeable. Prevention of loss of moisture is important not only for strength development but also to prevent plastic shrinkage, for decreased permeability and to improve resistance to abrasion. Good and complete curing is not always practical for several reasons, particularly in higher grade concretes. Using self-curing agents can solve this problem. The concept of self-curing agents is to reduce water evaporation from concrete, and hence increase its water retention capacity compared to conventional curing. Several materials, including polymeric glycol and paraffin wax, can act as selfcuring compounds. This study investigates the role of paraffin wax as a self-curing agent and compares this with the effect of different curing regimes simulating traditional methods of curing. The parameters include grade of concrete, type and dosage of paraffin wax, curing conditions and age of curing. Weight loss and compressive strength are determined as a performance benchmark for the investigated curing compounds. It is found that the lower dosage (0 . 1%) liquid paraffin wax compounds act as the best curing compounds in higher grade concretes.

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The role of hydrophilic (polyethylene glycol) and hydrophobic (light liquid paraffin wax) chemicals as self-curing compounds to improve the curing efficiency of self-compacting concrete (SCC) was investigated in terms of performance and microstructure. The parameters considered in the investigation were the concrete grade, dosage of self-curing compound, curing regime, temperature and duration of curing. Performance investigations included water retention tests, compressive strength test and durability studies (porosity, sorptivity, rapid chloride permeability and accelerated corrosion permeability tests). Microstructural analyses studies (X-ray diffraction analysis and scanning electron microscopy) were conducted to confirm the results obtained from the macrostructural studies. Two grades of concretes, with compressive strengths of 70 MPa and 50 MPa, were used. Based on experimentation and microstructural studies, it was concluded that the addition of optimum dosages of hydrophilic and hydrophobic chemicals arrested loss of moisture, resulting in improved water retention and progressive hydration of SCC.

Internal curing can be adopted to ensure the availability of water for the hydration of cement, mitigating the adverse effect of water loss to surroundings. The use of self-curing compounds is increasing in the context of the widespread use of self-compacting concrete (SCC) owing to its superior performance in both fresh and hardened states. This paper addresses the effect of using paraffin wax as a self-curing compound in SCC mixes. The variable parameters of the study include curing type, concrete grade (mix proportions), molecular weight and dosage of paraffin wax. Water retention, sorptivity and compressive strength tests were conducted on hardened concretes. The weight loss after 90 d was found to be less in specimens with a self-curing agent than in specimens without. The compressive strengths of the self-cured specimens closely matched those of conventional water-cured specimens. The optimum dosages of light and heavy molecular weight liquid paraffin wax were determined to be 0·1% and 1·0% by weight of cement respectively. It is this concluded that the use of self-curing compounds in SCC facilitates better hydration and thus enhancements in strength and durability properties.

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