This research investigated the effect of fly ash content on the compressive strength development of ultra-high-performance concrete (UHPC) at different curing conditions, i.e., the standard curing condition and the heat curing. A total of 20 mixtures were prepared to cast specimens to measure the compressive strength at different ages from 3 days to 180 days. Additionally, 300 specimens were prepared to estimate the appropriate heat curing period at the early ages in terms of enhancing the 28-day compressive strength of UHPC with high content of fly ash (FA). From the regression analysis using test data, empirical equations were formulated to assess the compressive strength development of UHPC considering the FA content and maturity function. Test results revealed that the preference of the addition of FA for enhancing the compressive strength of UHPC requires the early heat curing procedure which can be recommended as at least 2 days under 90 °C. Moreover, the compressive strength of UHPC with FA under heat curing mostly reached its 28-day strength within 3 days. The proposed models based on the fib 2010 model can be a useful tool to reliably assess the compressive strength development of UHPC with high-volume fly ash (HVFA) (up to 70% fly ash content) under a heat curing condition that possesses a different performance from that of normal- and high-strength concrete. When 50% of the cement content was replaced by FA, the embodied CO₂ emission for UHPC mixture reduced up to approximately 50%, which is comparable to the CO₂ emission calculated from the conventional normal-strength concrete.

This study examined the effectiveness of zeolite addition to reduce the autogenous shrinkage of high-performance cement-based concrete (HPC). The zeolites were replaced up to 15% of the cement content by weight and their mean particle size varied from 5.6 to 16.7 µm. To evaluate the crack resistance of HPC containing zeolites, the ring tests and internal relative humidity measurements were performed at different ages. The compressive strengths were determined at 3, 7, 28 and 90 days of curing. Test results confirmed that the addition of zeolite was promising and favourable in enhancing the compressive strength, crack resistance and reducing the autogenous shrinkage of HPC due to synergistic pozzolanic and internal curing effects. The autogenous shrinkage tended to decrease with the increase in zeolite content and its particle size. In addition, the extent of the autogenous shrinkage development at the early ages decreased with higher zeolite content replaced. Furthermore, to predict the autogenous shrinkage of HPC containing zeolite, an improved model has been proposed, in which the conventional ultimate autogenous shrinkage strain and time function were modified by introducing new parameters accounting for the zeolite content and its particle size. It appeared that the proposed model was able to capture the autogenous shrinkage behaviour of HPC with or without zeolite, while the fib 2010 model underestimated the autogenous shrinkage of HPC containing less than 10% zeolite replacement.

Expanded Polystyrene based Lightweight concrete (EPS-C) is a lightweight material with low compressive strength and high energy absorption capacity. This type of concrete is mainly applied for heat and sound insulation, towards energy saving and sustainable development. In terms of composition, EPS-C is made from a mixture of cement, mineral additives, water, chemical additives, and Expanded Polystyrene Beads (EPS) which are small hollow spherical, impermeable, and non-toxic balls. In this paper, the EPS particles were replaced with recycled polystyrene particles as aggregates for lightweight concrete. Besides, carbon nanotube (nCNT) was added to improve the properties of the concrete. The experimental results show that (i) it is possible to use recycled EPS aggregate in making lightweight concrete with a density of less than 1200 kg/m³; (ii) the combination of nCNT improved significantly the properties of lightweight concrete, i.e. reducing the water absorption, increasing compressive strength; (iii) lightweight concrete with a very low thermal conductivity, corresponding to 0.152 W/m.°C for a sample with a density of 600 kg/m³.

This paper presents a fracture behavior modeling of Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) slabs under contact blast loading using the finite element method. The UHPFRC is supposed to be brittle material and follow the Johnson–Holmquist-II(JH-2) model. The steel rebar is modeled using the elasto-plastic model. The Emulsion Explosive has been used and modeled by the SPH method. UHPFRC slabs with the dimensions 1000mm of length, 800mm of width and 120mm of thickness is considered. The steel fibers with a volume fraction of 2% is used. The UHPFRC material is fabricated in laboratory using the material available in Vietnam. The concrete crater and spall damage of UHPFRC slab under contact blast loading are considered. The numerical results are compared with experiment. These results allow to evaluate the resistance against blast load of UHPFRC fabricated in lab.