**Abstract**

Thermal cracking in concrete members having large sections, namely *mass concrete*, continues to be a concern for designers and specifiers of concrete. These issues are common to both large structural components in buildings and in civil engineering infrastructure projects. The common issues is based on the large scale of concreting dimension; mean large cement content cause more thermal hydration of concrete extremely. There is often a conflict for concrete specifier or concrete structural designer, between requirement to form high strength concrete for structural durability and structural bearing load capacity, which needs higher binder content versus higher heat of hydration characteristic of concretes. The potential problem that may be occurred is concrete thermal crack. The reaction of cement with water is exothermic, therefore it produces heat. The more Portland cement in the mix, the greater is the heat produced. To control the thermal crack means to control the concrete hydration thermal. The research started by laboratory scale trial mix Fc'25 Low Heat Concrete Bioconc-based concrete Job Mix, from cement content reduction 20, 25, 30, and 40%. The attached result shows optimum jobmix is Fc'25 Low Heat Concrete Bioconc-based concrete Job Mix on 40% cement as binder content reduction, was chosen as Low Heat Concrete Mix Mock Up. Later on, based on the optimum concrete jobmix Fc'25 R = 40%, cement content reduction 40%, above mentioned trial mixed, the research developed to project scale on mock up for sampling mass concrete dimension 1000 × 1000 × 2500 mm3 compared with similar two mock-up of mass concrete thermal hydration control, i.e., Fc'25 + FA.20% + Ice Block (Pre-cooling with crushed ice block Mass Concrete Fc'25 with fly ash 20%) and Fc'25 + FA.40% (Low Heat Concrete Fc'25 with Fly Ash 40%). The attached Graph Thermal Monitoring Low Heat Concrete shows that the peak temperature occurred 63.5°C in 29.5 h after pouring and maximum thermal differential between LHC layers is 19.5°C. Another two Low Heat Concrete Method Statement, i.e.: Pre-cooling and Low Heat Concrete with Fly Ash 40%, Mock Up Graph Thermal Monitoring also attached for comparison study. The observation and analysis proof that, "Low Heat Concrete Hydration Thermal Reduction with Bioconc" is work simplifier and economically, for mass pouring. The most essential thing is that, the basic concept of Bioconc's Low Heat Concrete on reducing the mass concrete cement-binder content means reducing CO2 emission in every concrete production, without any hazard impact to the environment. Its mean Bioconc based Low Heat Concrete contribute to develop the green technology and eco-friendly technology on the concrete industry as sustainable green technology.

**Keywords:** mass concrete, concrete hydration thermal control, low heat concrete, pre-cooling, post cooling, Bioconc, green technology, eco-friendly
