Open Access

In order to reduce the carbon footprint, biochar can be used as CO2 negative concrete constituent.The paper shows results of experiments with cement paste and mortar mixtures with 5%, 15% and 30% of cement volume replaced by biochar. The density of the char is measured with a pycnometer I dried and wet conditions, workability is assessed using a spread flow test, and hydration characteristics are measured using isothermal heat flow calorimetry. In addition strength results are presented. The results show that char does not interfere with the cement hydration at early ages, but the water entrapped in the particles can have a slight retarding effect. In general workability and strength were negatively affected by the presence of biochar. However, small amounts of biochar can even have a positive effect on strength without negatively affecting the other properties of the material. The fact that at dosages above 5% the performance specifications of paste and mortar deteriorated has a detrimental effect on the use of biochar as carbon sink in structural concrete.

Chemical admixtures are an integral component of modern concrete and enable the careful tailoring of fresh and hardening properties. Herein we investigate candidate materials from the bioeconomy in idealized system and discuss the methodology as a possible rapid evaluation technique to categories the role of the candidate biopolymers at selected dosages.

With growing environmental impacts over the construction of and lifetime of built infrastructure, tools are needed to guide emissions reduction strategies. Herein, the EDGE Application by the International Finance Corporation (IFC) is investigated via case studies to understand hidden assumptions in the system and potential gaps in early efforts such as the EDGE tool. This work highlight questions around how baselines are selected, what are appropriate and feasible mitigation strategies, and if the quantified impacts lead to meaningful improvement.

As future populations are projected to boom, cement and concrete consumption in Africa is expected to explode. With increasing interest in the socio-economic development of this region tied to recent investment in production capacity by development banks, we investigate the current state of production, consumption and the related environmental impacts for cement in Africa. Trade and production statistics are used to map the source of production and understand regional material fluxes. A harmonized environmental impact model is assembled that represents the technology and energy sources of each area to model the production emissions from each unit of material. Herein, greenhouse gas (GHG) emissions as well as water demands, water consumption, particulate matter, and other notable air pollutants are modeled to provide information on climate related impacts as well as those directly related to human health. Median 2022 import reliance by country or area was ~37% with 15 areas fully reliant on imports. While GHG-related impacts are similar, there were shifts in particulate matter and water related impacts between imported and domestically produced materials. Together this model enables the exploration of potential impact shifting and raises important question about material sovereignty and the ability for local areas to regulate the embodied environmental impacts of the building material that are critical to future socio-economic development in their regions.

3DCP introduces monitoring demands absent in cast concrete: the material is simultaneously being deposited, self-loading, and hardening, with failure modes — collapse, inter-filament cracking, interfacial voids — that are invisible to any external sensor. This presentation reported preliminary results from an embedded PZT sensor system addressing this gap through two complementary modalities operating from the same array. The electromechanical impedance (EI) modality tracks local elastic property development through resonance frequency shift and conductance decrease. Paste-level validation across four mix designs (w/c = 0.32, 0.36, 0.40, and 0.36 + 0.5% NaP retarder) demonstrated sub-10-minute sensitivity to early hydration and a clear quantitative correlation between normalised conductance decrease and independently measured shear modulus. In full printed beam specimens (68 × 30 × 17 cm), three embedded sensors tracked EI evolution through 700 hours, corroborated by thermal kinetics, Vicat set behaviour, and external wave velocity measurements. The wave propagation modality used the same array in actuator-receiver configuration to measure time-of-flight and signal energy between sensor pairs. A key finding was directional asymmetry: longitudinal pairs stiffened faster than the transverse pair crossing the inter-layer interface, providing direct in-situ evidence of deposition-induced mechanical anisotropy. Energy inflection points at approximately 100–200 hours were interpreted as the transition from stiffening-dominated to damage-dominated regimes, consistent with post-hardening XCT observations of drying shrinkage cracking along inter-filament contacts. The presentation closed with an honest challenge: even with a functioning sensor system, four embedded sensors cover less than 1% of the element's information field. The sensing density problem was posed as an open question to the committee, framing it not as an instrumentation failure but as a geometric inevitability of the sequential deposition process demanding new thinking on distributed sensing architectures.