Engineering properties of self-compacting concrete incorporating PET fibres and recycled fine concrete aggregates

Concrete is currently the most frequently used material in the building sector due to its favourable properties. However, the proliferation of waste poses a significant environmental problem. Over the past three decades, researchers have explored the use of construction and demolition waste (CDW) as well as plastic waste as aggregates, binders, and fibres in construction materials. This approach has emerged as a notable solution to address environmental and economic challenges. The objective of this research is to assess the impact of polyethylene terephthalate fibres (PETF) on the behaviour of self-compacting concrete (SCC) with recycled fine concrete aggregates (RFCA). Natural fine aggregates (NFA) were used as a substitute for RFCA at different mass fractions (0–100%). Additionally, four volumetric fractions (Vf) of PETF (ranging from 0.3% to 1.2%) were added, and the findings revealed an improvement in the flexural strength and modulus of elasticity of the composite material obtained. However, as the Vf content of PET fibres and RFCA increased, the compressive strength decreased, negatively affecting water absorption by immersion and capillary water absorption. Using 100% RFCA and 1.2% PETF enhanced the modulus of elasticity and flexural strength of recycled self-compacting concrete (RSCC) by up to 25% and 9%, respectively

Effect of the fineness of mineral additions on the behavior of low impact environment self-compacting mortars

The aim of this experimental work is to analyze the effect of mineral additions fineness on the hydration of self-compacting mortars, as well as their behavior in the fresh and hardened states. To do this, cement was partially replaced with a fixed rate of 20% for natural pozzolan and 30% for slag. The additions were ground to three different fineness. The results showed that the use of slag is favourable to the formulation of self-compacting mortars, the workability has been considerably improved, the increase in its fineness, meanwhile, reduces the dosage of superplasticizer up to 46%. For the pozzolan, on the other hand, not only was the workability reduced, but the increase in fineness implies an additional demand for superplasticizer up to 16%. Mortars based on additions release less heat, nevertheless, this reduction is accompanied by a drop in compressive strength at a young age. However, the increase in fineness lets to accelerate the initial hydration, inducing additional strength, and to generate heat comparable to that of the reference mortar. Nonetheless, in the case of excessive grinding, the heat release must be taken into account in order to avoid the thermal cracking

Performance of compressed earth blocks reinforced with natural fibers

In contemporary times, governments prioritise the construction of structures that are both durable and cost-effective. Compressed earth blocks (CEB), known for their low environmental impact, excellent thermal insulation, and water resistance, have consistently met these criteria while seamlessly blending modernity with tradition. This study aims to investigate the mechanical and thermal properties of CEB stabilised with cement, compressed at 3 MPa, and reinforced with fibres derived from alfa and vine shoots. The fibres underwent chemical treatment, employing an alkali-acrylic process, to enhance their bond with the matrix, thereby bolstering the mechanical strength of the CEB. Results indicate a notable reduction in water absorption for treated alfa and vine shoot fibres, with reductions of 45% and 33%, respectively, compared to untreated fibres. Optimal compression resistance was achieved with a composition of 1.5% vine shoot fibres and 2.5% alfa fibres. Moreover, surface treatment of fibres led to a 5% and 20% increase in compressive strength for alfa and vine shoot fibres, respectively. Additionally, employing both fibre types resulted in decreased thermal conductivity and density, albeit with a slight adverse effect on thermal conductivity in CEBs containing treated fibres of both types

Effect of the fineness of mineral additions on the behavior of low impact environment self-compacting mortars

The aim of this experimental work is to analyze the effect of mineral additions fineness on the hydration of self-compacting mortars, as well as their behavior in the fresh and hardened states. To do this, cement was partially replaced with a fixed rate of 20% for natural pozzolan and 30% for slag. The additions were ground to three different fineness. The results showed that the use of slag is favourable to the formulation of self-compacting mortars, the workability has been considerably improved, the increase in its fineness, meanwhile, reduces the dosage of superplasticizer up to 46%. For the pozzolan, on the other hand, not only was the workability reduced, but the increase in fineness implies an additional demand for superplasticizer up to 16%. Mortars based on additions release less heat, nevertheless, this reduction is accompanied by a drop in compressive strength at a young age. However, the increase in fineness lets to accelerate the initial hydration, inducing additional strength, and to generate heat comparable to that of the reference mortar. Nonetheless, in the case of excessive grinding, the heat release must be taken into account in order to avoid the thermal cracking