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The cracking of plastic concrete remains a problem in the construction industry due to its complexity and incomplete understanding. One of the reasons for this is the lack of knowledge regarding the tensile material properties of the plastic concrete. This paper describes and builds the appropriate test setup needed for the challenging tensile testing of plastic concrete as well as discusses the measured tensile properties. The tensile strength and Young's modulus increase exponentially near the final setting time and initial setting time respectively. The strain capacity and initial fracture energy decrease significantly between the initial and final setting times. The tensile properties develop faster and with higher values the greater the ambient temperature. Plastic concrete proved to be resilient and capable of withstanding multiple loading and ceased loading cycles, while a solid but still weak concrete could not. The tests also highlighted the need for further research regarding the influence of hydrostatic pressure and the relaxation of stresses in plastic concrete.

The advancement of concrete technology such as 3D concrete printing has rekindled research interest in the early-age mechanical properties of concrete. However, the non-adaptability of early-age (plastic) concrete to classical mechanical measurements causes the quest for alternative approaches. This study is a new and unique approach, using rheological methods, aimed at investigating the early development of shear and viscoelastic properties of concrete from the time of mixing up to the initial setting time. Dynamic shear rheometry (coupled with rotational tests), taking advantage of the normal stress measurement, was used to evaluate the shear and viscoelastic properties. Viscosity modifying agent (VMA), superplasticiser (SP) and increased water content were incorporated to achieve a robust test program. The Mohr-Coulomb shear parameters, shear yield parameters, shear modulus, creep and stress relaxation properties were evaluated from rheometry tests. Theoretical and experimental analyses of a vane-in-cup rheometry reveal that the resultant normal stress, during an elastic response, originates from the self-weight of the sample and is dependent on the sample's weight distribution. The results, therefore, show that it is not sufficient to estimate the self-weight of the concrete for normal stress evaluation and that the shear and creep properties of concrete mainly develop within half-time of the initial set while stress relaxation is inherent and remains fairly unchanged. Challenges and prospects of this approach were also discussed.

Plastic shrinkage cracking (PSC) in concrete is related to the amount and rate of free pore water loss due to evaporation. This study investigates the influence of solar radiation on evaporation, the concrete temperature, plastic shrinkage and cracking. Literature suggests that exposure to solar radiation can either: increase the concrete temperature and, consequently, increase the rate of tensile strength gain resulting in less severe PSC or can increase the concrete temperature, resulting in a higher amount and rate of pore water loss to produce more severe PSC. The results of this study indicate that exposure to solar radiation significantly increases the amount and rate of pore water loss as well as plastic shrinkage and severity of PSC. To study PSC, many authors have estimated the evaporation rate from wind speed, air and concrete temperature and humidity which would result in significantly underestimating the actual evaporation rate if the concrete is exposed to moderate or high solar radiation. The accuracy of several radiation-related evaporation estimation models was evaluated by comparing the models to the actual rate of evaporation from specimens placed in the sun. A more accurate model was identified to estimate the evaporation in concrete specimens when exposed to solar radiation.

Sugarcane bagasse ash (SCBA) has been pitched as a feasible supplement that can ease the sustainability issues associated with cementitious materials. In this respect, SCBA has been well researched with over 100 journal publications. However, there is a scarcity of comprehensive reviews detailing the research developments so far. Therefore, this study is a holistic review with a large scope, content and coverage that emanated from a comprehensive dissection of the literature. The study systematically reviewed the SCBA's origin of pozzolanicity, processing approaches, sustainability potentials, and performance in cementitious materials. The performance entailed characterisation, pozzolanic activity, microstructure refinement, fresh and rheological properties, mechanical and durability properties. SCBA processing is key to its reactivity and performance; hence, recommendations were made on the best processing approach. Performance ranging from 80 to 160% of the control (without SCBA) exist in the literature. Such performance emanates from a conservative use of about 20–25% or further processing that yields optimum contents up to 50%. This study serves as an up-to-date appraisal of data and researches related to the use of SCBA in cementitious materials.