Unhydrated Cement Particles Research Articles

The Effect of Calcium Sulfate on the Hydration and Properties of Red Mud-Based Calcium Ferroaluminate Cement Clinker.

The hydration of high-alkali red mud-based ferroaluminate cement (RCFA) clinker with calcium sulfate needs to be regulated. This study explored the effects of the calcium sulfate type and dosage on the hydration and properties of high-alkali RCFA clinker. The research results show that when 4% gypsum was added, the 3 d compressive strength of cement was 39.1 MPa, and the 28 d compressive strength was 63.2 MPa. The 28 d strength increased by 61.6% compared with the 3 d strength. The properties of cement paste can be adversely affected by excessive anhydrite content. The exothermic hydration of clinker was accelerated by calcium sulfate at the beginning, but the rate declined as the process progressed. Sufficient sulfur supply can enhance the hydration of ye'elimite, thereby increasing the AFt content in the hydration product. The mass loss of the hydration product is mainly caused by the dehydration of ettringite, monosulfoaluminate, and AH3. In addition, the Na element in the RCFA hydration product is mainly present in monosulfoaluminate and unhydrated cement particles.

Evaluating dynamic modulus of cold in-place recycling mixture with foamed bitumen using field core samples

This study evaluates the dynamic modulus of Cold In-Place Recycling with Foamed Bitumen (FB-CIR) pavements, focusing on the influence of various recycled materials—reclaimed asphalt pavement (RAP), reclaimed inorganic binder stabilized aggregate (RAI), and their combination (RAP+RAI). Core samples from three representative FB-CIR projects in China were tested using the MTS-130 system across temperatures of −10°C, 5°C, 20°C, 35°C, and 50°C, and frequencies ranging from 25 Hz to 0.1 Hz. Statistical analysis and the Sigmoidal model were employed to analyze the viscoelastic behavior and establish the master curve for the FB-CIR dynamic modulus. The dynamic modulus of the three FB-CIR mixtures showed pronounced frequency-dependence, decreasing with reduced frequencies, and exhibited temperature sensitivity, with lower values at elevated temperatures. FB-RAI consistently demonstrated higher modulus values due to the hydration of previously unhydrated cement particles, while FB-RAP and FB-RAP+RAI displayed lower values, as RAP behaves similarly to unbound granular material. The construction of the master curve, based on the time-temperature superposition principle, enhanced our understanding of FB-CIR mixtures' mechanical behavior and enabled accurate extrapolation of dynamic modulus values across diverse conditions. Furthermore, FB-RAI's narrow phase angle variation indicates its superior mechanical stability and reduced sensitivity to external changes, making it ideal for areas with extreme climate fluctuations or heavy traffic. The study also identified three distinct phase angle variation patterns in FB-CIR mixtures, underscoring the importance of nuanced pavement design strategies that consider temperature, frequency, and material composition to optimize the performance and durability of FB-CIR pavements.

Polyimide strengthened cement mortar

Abstract This study examined the effects of silane-modified polyimide polymer (PIS) on cement mortar. The PIS was added to replace cement in a specified ratio. Obtained results revealed that the PIS caused retardation on setting time, and accelerated UPV mostly by encapsulating unhydrated cement particles, filling pores, or reacting with C–S–H and Ca(OH)2 with shifting to Si–O vibrations. SEM results showed a good compact interface without forming considerable agglomeration and voids on the microstructure, and this improved flexural and compressive strength properties. In conclusion, silane-modified polyimide as an admixture or cement replacement can be recommended for construction industries to enhance the properties of cement mortar.

Analytical Solution for Predicting the Elastic Modulus of a Cement Slurry System with the Effect of Calcium Dissolution.

The dissolution of calcium ions in concrete in a low-alkalinity environment is an important factor causing a significant increase in the porosity of internal concrete, leading to a deterioration in its mechanical properties and affecting the durability of the concrete structure. In order to improve the reliability of concrete durability design and significantly increase the service life of concrete structures located in soft water environments, it is crucial to establish an analytical method to predict the elastic modulus (Edc) of cement slurry systems suffering from calcium dissolution. Firstly, the hydrated cement particles are regarded as a three-phase composite sphere composed of unhydrated cement particles (UC), a high-density hydrated layer (H-HL), and a low-density hydrated layer (L-HL). By introducing the equivalent inclusion phase (EQ) composed of UC and H-HL, the three-phase composite sphere model can be simplified into an equivalent hydrated cement particle model composed of EQ and L-HL. Finally, the Edc of the two-phase composite sphere composed of the equivalent hydrated cement particles and the porosity of the dissolved cement slurry system are solved by using elasticity theory. The effectiveness of the developed analytical method is verified by comparing it with third-party numerical results. Based on this method, the effects of hydration degree, volume ratio of calcium hydroxide (CH) to hydrated calcium silicate (C-S-H), and volume ratio of inner C-S-H to outer C-S-H on the Edc of the dissolved cement slurry system are analyzed. The parameter analysis indicates that among the three influencing parameters, the hydration degree has the greatest effect on the Edc of the dissolved cement slurry system. This study provides an analytical method for predicting Edc, which can provide some references for the durability design of concrete after calcium dissolution.

Investigation of the freeze-thaw deterioration behavior of hydraulic concrete under various curing temperatures

To address the issue of damage and deterioration of hydraulic concrete materials in cold regions, experiments were conducted to investigate the microstructural and mechanical properties of concrete under the combined effects of various curing temperatures and freeze-thaw (F‒T) cycles. The results indicate that as the curing temperature decreases, the peak compressive strength of concrete decreases, while the peak strain increases and the elastic modulus decreases. These trends become more pronounced with the progression of F‒T cycles. Additionally, during the compression failure process of concrete, the amplitude of the acoustic emission exhibits a more significant and rapid increase as it approaches the critical state, indicating a stronger brittle characteristic of concrete after F‒T damage. Microscopic test results demonstrate that the influence of curing temperature on the pore structure of concrete after F‒T primarily manifests in the mesopores and large pores. Moreover, the reduction in curing temperature increases internal defects in concrete, deteriorates the crystallinity of hydration products, and leads to the aggregation of unhydrated cement particles. Insufficient curing temperatures slow the hydration rate of cementitious materials, affecting the density and overall performance of concrete. Finally, damage prediction models based on the Weibull distribution were established, using the relative dynamic modulus of elasticity, compressive strength loss rate, and mass loss rate as damage factors. The model based on the relative dynamic modulus of elasticity was more sensitive to the number of F‒T cycles. All models exhibited a goodness of fit exceeding 0.89, indicating that they accurately reflect variations in the observed data and can be used to predict the service life of concrete under F‒T cycles. This provides theoretical references for the degradation and damage of hydraulic concrete in cold regions.

Mix and measure II: joint high-energy laboratory powder diffraction and microtomography for cement hydration studies.

Portland cements (PCs) and cement blends are multiphase materials of different fineness, and quantitatively analysing their hydration pathways is very challenging. The dissolution (hydration) of the initial crystalline and amorphous phases must be determined, as well as the formation of labile (such as ettringite), reactive (such as portlandite) and amorphous (such as calcium silicate hydrate gel) components. The microstructural changes with hydration time must also be mapped out. To address this robustly and accurately, an innovative approach is being developed based on in situ measurements of pastes without any sample conditioning. Data are sequentially acquired by Mo Kα1 laboratory X-ray powder diffraction (LXRPD) and microtomography (µCT), where the same volume is scanned with time to reduce variability. Wide capillaries (2 mm in diameter) are key to avoid artefacts, e.g. self-desiccation, and to have excellent particle averaging. This methodology is tested in three cement paste samples: (i) a commercial PC 52.5 R, (ii) a blend of 80 wt% of this PC and 20 wt% quartz, to simulate an addition of supplementary cementitious materials, and (iii) a blend of 80 wt% PC and 20 wt% limestone, to simulate a limestone Portland cement. LXRPD data are acquired at 3 h and 1, 3, 7 and 28 days, and µCT data are collected at 12 h and 1, 3, 7 and 28 days. Later age data can also be easily acquired. In this methodology, the amounts of the crystalline phases are directly obtained from Rietveld analysis and the amorphous phase contents are obtained from mass-balance calculations. From the µCT study, and within the attained spatial resolution, three components (porosity, hydrated products and unhydrated cement particles) are determined. The analyses quantitatively demonstrate the filler effect of quartz and limestone in the hydration of alite and the calcium aluminate phases. Further hydration details are discussed.

Study on the Effect of Additives on the Performance of Cement-Based Composite Anti-Corrosion Coatings for Steel Bars in Prefabricated Construction.

The influence of polymer emulsion, pigment filler, and dispersant on the corrosion resistance of polymer cement-based composite anti-corrosion coatings were investigated in this study. Adhesion loss rate tests and electrochemical tests were conducted on samples. The research results show that optimal corrosion resistance can be achieved with a 45 wt% dosage of emulsion, a 6 wt% dosage of pigment filler, and a 0.30 wt% dosage of dispersant. The bonding properties of bare steel bars, epoxy-coated steel bars, and polymer cement-based composite anti-corrosion coated steel bars with grout were compared. The results show that the polymer cement-based composite anti-corrosion coating can enhance the bonding properties of the samples. Furthermore, the microscopic analysis was conducted on the samples. The results demonstrate that the appropriate addition of emulsion can fill internal pores of the coating, tightly bonding hydration products with unhydrated cement particles. Moreover, incorporating a suitable dosage of functional additives enhances the stability of the coating system and leads to a denser microstructure.

An investigation of the source of calcium carbonate from the carbonated Portland cement: Based on the transformation of hydrates

In this work, two PC pastes were used to carry out accelerated carbonation experiments, and phase assemblages of paste samples collected at different sampling depths were analyzed. The source of CaCO3 originating from the carbonation reaction of hydrates in cement was quantitatively determined by a novel method based on the transformation of hydrates. Experimental results indicated that the phase assemblages in the carbonated zone of two PC pastes showed minor differences. C(A)SH, ettringite, AFm-CO3, and unhydrated cement particles in the complete carbonation zone of two cement pastes were carbonated and transformed into other phases. For the surface of two PC pastes (0–3 mm), calculations showed that the CaCO3 originating from the carbonation of calcium hydroxide and C(A)SH accounted for 75.3% and 72.6% of the total CaCO3, respectively. A concentration of 20% CO2 was not beneficial for the diffusion of CO2 and the subsequent precipitation of CaCO3 at the later period of carbonation.

Influence of oil well cement on the structure and properties of thermosetting resin cementing fluids

Oil well cement was added as an admixture to the waterborne epoxy resin cementing fluid to form a resin-cement slurry system, and its properties were discussed in depth. It was found that the mechanical properties of the resin cement stone were best when the dosage of oil well cement was 10%. And the measurements of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that the addition of oil well cement did not affect the curing properties of the epoxy resin, and the epoxy resin did not affect the hydration process of cement and its products. According to data from the mercury-in-pressure porosity (MIP) method and scanning electron microscopy (SEM), it was obtained that the polymer film formed after the curing of epoxy resin was connected between the hydration products or wrapped around the unhydrated cement particles, which results in a denser structure within the resin cement stone. Overall, this resin-cement slurry system has the potential to enhance cementing quality.

Effect of vehicle-induced vibration on the strength, nano-mechanical properties, and microstructural characteristics of ultra-high-performance concrete during hardening process

Ultra-high-performance concrete (UHPC) has been rapidly accepted in accelerating bridge construction attributed to its superior workability and mechanical performance. However, the unavoidable vehicle-induced vibration in construction site may cause the performance degradation of UHPC, and the influencing mechanisms have not been well-documented. In this study, the effects of various vibration parameters (amplitudes, frequencies, and phases) on the macroscopic properties, nano-mechanical properties and microstructure evolution of unhardened UHPC were investigated. Results demonstrated that the microstructural evolution and strength development of UHPC differed at different introduced vibration energy, although the vibration during the hardening process can disperse the unhydrated cement particles, decrease the Ca/Si values and form additional C–S–H gels. The low-energy vibration (low-amplitude vibration and vibration before initial setting) refined the pore structure and optimized the fiber orientation in UHPC, leading to a volume increase of gel nano-pores (<10 nm) and a higher fiber orientation coefficient (ηθ). This improvement results in an increase in its compressive and flexural strength by 0.6%–3.8% and 6.8%–24.5%, respectively. In contrast, however, the high-energy vibration (high-amplitude vibration and vibration after initial setting) coarsened the large capillary pores (100–5000 nm) and macro-pores macro-pores (>5000 nm). Furthermore, the interaction (adhesion and friction) between the aggregate and matrix in UHPC was also disrupted under this condition, as confirmed by SEM. This leads to the evolution of interfacial transition zone (ITZ) in UHPC from a dense framework to a framework with microcracks.

Mix and measure - Combining in situ X-ray powder diffraction and microtomography for accurate hydrating cement studies

It is reported an innovative methodology based on in situ MoKα1 laboratory X-ray powder diffraction (LXRPD) and microtomography (μCT) avoiding any sample conditioning. The pastes are injected in 2.0 mm capillaries and the extremes are just sealed. The measurements take place in the same region of the hydrating paste. Thick capillaries are key to avoiding self-desiccation, which dictates the need of high-energy X-ray radiation for the diffraction study. This approach has been tested with a PC 42.5 R paste having w/c = 0.50. μCT data were collected at 12 h and 1, 3, 7 and 79 days. LXRPD data were acquired at 1, 3, 7 and 77 days. In this proof-of-principle research, the same paste was also cured ex situ. Portlandite contents obtained by thermal analysis, ex situ powder diffraction, in situ mass balance calculation and in situ powder diffraction were 13.8, 13.1, 13.1 and 12.5 wt%, respectively. From the μCT study, the grey value histogram evolution with time showed a crossing point which allowed us to distinguish (appearing) hydrated products from (dissolving) unhydrated cement particles. Segmentations were carried out by global thresholding and the random forest approach (one type of supervised Machine Learning). The comparison of the segmented results for the unhydrated cement fraction and the Rietveld quantitative phase analysis outputs gave an agreement of 2 %. The potential of this methodology to deal with more complex binders is also presented.

Experimental Study On Acoustic Emission Characteristics of SAP Mortar Self-Healing Process

Self-healing properties of super absorbent polymer (SAP) concrete can reduce the harmful effects of concrete cracking in structures. This study examines the self-healing process of mortars with different SAP content under dry and wet conditions through acoustic emission testing (AE) and elastic wave velocity testing. Findings indicate that the SAP mortar healing process has three stages: rapid water absorption, smooth water absorption, and drying. In a dry environment, increasing SAP content enhances AE activity, indicating internal crack self-healing via further hydration of unhydrated cement particles. In a wet environment, AE activity increases with increasing SAP content during the second healing cycle, indicating self-healing of the mortar matrix. These results suggest the use of SAP concrete could potentially mitigate future structural damage.

Repairing performance and bottleneck analysis of concrete with encapsulated oxygen-dependent microbial Agent: Simulation-Aided characterization

Microbial self-healing concrete has natural advantages because of its environmental harmlessness and compatibility. Appropriate nutrients, microbial composition, and carriers are critical for microbial repairing agents to maximize restoration effectiveness in the harsh environment of concrete. However, little attention has been paid to the evolution of the healing process and the underlying mechanisms of bottlenecks. In this study, the potential of calcium lactate as the main nutrient source for Bacillus alcalophilus (B. alcalophilus), an alkali-resistant spore-producing microorganism, has been demonstrated firstly. The repairing performances and bottlenecks of oxygen-dependent microbial agent were then explored. Considering the harsh environment of concrete, calcium sulphoaluminate (CSA) cement was introduced to form a protective shell through artificial aggregate technology. Simultaneously, to reduce the influence of un-hydrated cement particles and to stabilize the continuous supply of calcium ions, the matrix has a higher maturity through 60 days of hydration. The results show that the encapsulated microbial self-healing agent had good repairing effects on cracks introduced after 60 days of hydration. Moreover, the distribution of repairing products in cracks was observed by X-CT, and the microbial remediation ability based on aerobic decomposing organic compounds was verified by simulation. The bottlenecks, shallow restoration depth and uneven distribution of restoration products, are mainly caused by gas transport and microbial biochemical activity. Finally, increasing the oxygen content in the fracture zone is an effective means to promote carbonate production and fracture filling.

Comparative Study between Recycled Fine and Coarse Aggregate Used in Roller Compacted Concrete Pavement

To decrease the impact on the environment of building waste, the recycled aggregate may be used in various sustainable engineering applications, such as roller compacted concrete pavement (RCCP). This research examined how using recycled aggregate as a partial replacement for natural aggregate as coarse or fine affected the mechanical properties of roller-compacted concrete pavement. The recycled aggregate was crushed and sieved to coarse and fine aggregate before being used in the roller-compacted concrete pavement. Compressive strength, splitting tensile strength, and flexural strength were all evaluated after the samples were prepared at 28 and 90 days of curing. According to the study's findings, the partial replacement of coarse or fine aggregate with recycled aggregate by (10, 15 and 20%) by volume resulted in decreasing the mechanical properties and increasing the absorption and porosity of RCCP due to the contaminated cement paste on the surface of RCA when compared to the reference mix made with natural aggregate. Because the recycled aggregate contains un-hydrated cement particles, the results have improved after 90 days.

Nanoindentation and nano-scratch testing on cement paste

Carbon nanotubes are an attractive reinforcement material for several composites. This is due to their inherently high tensile strength and high modulus of elasticity. This study focused on the nanomechanical characteristics of cement paste with and without short multi-walled carbon nanotubes (MWCNTs). The objective behind studying the nanomechanical properties of cement paste is to better understand the fundamental behaviour of cement at the nanoscale level. Cement paste is a complex material that consists of various phases, including cement hydrates, unhydrated cement particles and porosity. By studying the mechanical properties of cement paste at the nanoscale, researchers can gain insights into the mechanisms that govern the behaviour of this material. Following earlier tests, the amount of MWCNTs was kept constant (0.30% by weight of cement). The nanomechanical parameters explored included the localised Young's modulus and hardness. According to the test results, short MWCNTs increased the proportion of high-density calcium silicate hydrate in the cement paste. The nanomechanical properties (localised Young's modulus and hardness) of cement paste with short MWCNTs were found to be greater than those of cement paste without MWCNTs. According to nano-scratching experiments, the cement matrix with short MWCNTs was substantially more durable than the matrix without them.

A study on bacterial self-healing concrete encapsulated in lightweight expanded clay aggregates

Concrete is a widely used construction material susceptible to cracking due to internal and external stresses, affecting the long-term strength and durability of the structure. Self-healing concrete appears to be a promising solution to address this issue. For concrete, self-healing is naturally achievable to a certain extent by utilising unhydrated cement particles. However, to heal significant internal and external cracks over a long period, we need to develop new techniques to reach a practical level of self-healing. This study investigates autonomous self-healing concrete using Microbially Induced Calcite Precipitation (MICP). The concrete mix is created by incorporating Lightweight Expanded Clay Aggregate (LECA) encapsulated with Lysinibacillus sphaericus and Bacillus coagulans bacteria. Encapsulation is used to prolong the life of the bacteria and shield them from the highly alkaline environment of the concrete. A bacterial concrete mixture was made by replacing 20% coarse aggregate by volume with the bacteria-encapsulated LECA. The properties of self-healing concrete specimens were compared with conventional concrete specimens of grade M30. After curing, the cracked bacterial specimens underwent a 14-day wet and dry cycle to examine how well the bacteria healed the cracks. Then, the durability property was analysed based on water permeability and chloride penetration tests. The microstructure of concrete was examined using SEM and EDX analysis. Bacillus coagulans and Lysinibacillus sphaericus bacteria specimens showed favourable results compared to conventional concrete for hardened and durability tests performed. The two bacteria-encapsulated concrete also exhibited positive crack healing, and the macrocracks in the range of 0.1 to 0.5 mm were healed. A salt analysis confirmed the presence of Calcium Carbonate (CaCO3) in the healed portion of the concrete. Lysinibacillus sphaericus bacteria showed slightly better results than Bacillus coagulans, and both bacteria can be used for self-healing concrete applications.

Influence of recycled concrete aggregate enhancement methods on the change of microstructure of ITZs in recycled aggregate concrete

Recycled concrete aggregate (RCA) enhancement is an important method to improve the performance of recycled aggregate concrete (RAC). However, the quantitative studies on the change of microstructure of interfacial transition zones (ITZs) were few and far, especially after enhancement of RCA with different methods. This paper investigated the influence of carbonation enhancement (carbonation time, soaking in CH saturated solution and then carbonation) and chemical enhancement (respectively soaking in Na2SiO3 saturated solution and cement-silica fume (CEM-SF) slurries) of RCA on the change of microstructure of ITZs (including the ITZ between old aggregate-new paste (ITZ1) and ITZ between old paste-new paste (ITZ2)) in RAC. The porosity, the un-hydrated cement particles (UH) content, the volume fraction of hydration products (VFHP) in ITZs and the width of ITZs were obtained by backscattered electron imaging analysis (BSE-IA) and energy dispersive spectrometer (EDS) analysis. Results showed that the carbonation enhancement of RCA could not effectively strengthen ITZ1. However, soaking RCA in Na2SiO3 saturated solution and CEM-SF slurries could decrease the porosity and the UH content, develop the VFHP, and reduce the width of ITZ1, then strengthening ITZ1. Both carbonation and chemical enhancement could take obviously improvement on ITZ2. Additional calcium sources could be added to RCA by soaking in CH saturated solution, improving the effect of carbonation enhancement of RCA. Soaking in CEM-SF slurries had a better improvement effect on ITZs. After RCA was soaked in CEM-SF slurries, the porosity in ITZ1 and ITZ2 decreased by 36.8% and 44.0%, the UH content of ITZ1 and ITZ2 decreased by 22.6% and 53.6%, the VFHP of ITZ1 and ITZ2 increased by 22.6% and 20.9%, and the width of ITZ1 and ITZ2 decreased by 42.9% and 50%. EDS analysis showed that the Ca/Si atomic ratio of ITZs was reduced after RCA enhancement, which generated more hydration products and then decreased the porosity and the width of ITZs.

Water-driven expansion of boron nitride nanosheets for self-healing tobermorite composite

The water-driven expansion of folded BNNSs on the surface of the tobermorite is studied by molecular dynamics simulation. It shows that the expansion of folded BNNSs is significantly dependent on the deterioration of water molecules on the interfacial interactions between the folded BNNSs and tobermorite and between interlayers of the folded BNNSs. The interface deteriorations allow the relative sliding between folded BNNSs and tobermorite and between interlayers of folded nanosheets. Afterward, the vibration of the monolayered BNNS induces expansion due to its flexibility. To quantify the deterioration of the adhesion between folded BNNSs and tobermorite and between interlayers of folded BNNSs, steered molecular dynamics simulations are performed to calculate the energy barrier between them. It indicates that the presence of water molecules significantly reduces the energy barrier, resulting in the release of strain energy in folded BNNSs and the expansion behavior of BNNSs. Due to the presence of water, the hydration of unhydrated cement particles occurs and releases heat. Hence, the effect of temperature on the expansion degree of BNNS is studied, which shows an acceleration in the expansion degree of BNNS and envisions the self-healing of cracks in the tobermorite composite when the temperature is increased.

The Influence of Rehydration on the Properties of Portland Cement-Based Materials with Low Water/Binder Ratios: A Review of Existing Research.

Cement-based materials with a low water/binder ratio contain a high number of unhydrated cement particles, which implies that a rehydration reaction occurs when they encounter water again. This study aimed to explore how rehydration influences the macroscopic and microscopic properties of cement-based materials. The key study findings included that rehydration could still occur in cement-based materials after one year of hydration, and that the capacity for rehydration-induced repair or damage to cement-based materials depended on whether their internal pores could accommodate rehydration products. During rehydration, the compressive strength and porosity of the specimens were found to first increase and then decrease. The capillary water absorption coefficient decreased continuously over a rehydration period of 120 days. As the water/binder ratio rose, the rehydration rate first increased and then decreased. First, the influence of temperature on the rehydration rate was more noticeable when the water/binder ratio was below 0.3; second, whereas adding large amounts of fly ash and silica fume did not prove to be conducive to repairing and enhancing cement-based materials undergoing rehydration, adding slag and small quantities of silica fume, or alternatively compounding small amounts of silica fume and fly ash could improve the repair and enhancement effects of rehydration.

A preliminary study of mechanical treatments’ effect on the reactivation of hydrated cement paste

More than 4.4 billion metric tons of cement were produced in 2021 [1], making it one of the most common building materials. Unfortunately, excessive cement use brings up several environmental concerns, one being the enormous volumes of CO2e (carbon dioxide equivalent) created as a by-product. CO2e is a standard unit for measuring carbon footprint and can be calculated for all greenhouse gases using global warming potential. Reducing CO2 and other greenhouse gas emissions is crucial in modern cement manufacturing, as 0.9 kg of CO2e is produced for every kg of cement. Cement manufacturing contributed by releasing 3.96 Gt of CO2e into the atmosphere in 2021. This issue is often remedied using recycled materials in the fresh concrete mix as supplementary or pozzolanic additives. Some researchers have focused on regaining the activity of hydrated cement paste by grinding and thermally activating it [2–5], but a low-strength binder would also work for many applications. A low-strength binder recovered with as little energy as possible (only grinding, no heat treatment) could be considered a more sustainable and less energy-intensive way of recovery of the cement binder matrix. This study investigated a technique for recycling hydrated cement paste by mechanical treatment to disintegrate the hydrated cement conglomerate to reveal the unhydrated cement particles [6] that can be used as a recovered cementitious binder from processing waste from the production of wood-cement boards. Processing waste is defined as cement particles containing hydrated and unhydrated cement [7] and spruce wood fibres. The partly hydrated cement in the waste stream was mechanically processed in a planetary mill to reactivate it and restore its cementitious characteristics. The binder was characterized by density and mechanical compressive strength.