Construction materials such as sand, gravel, clay, laterite, limestone, and hard rocks show distinct spatial patterns across the Republic of the Congo. Sand and gravel are primarily found along riverbeds near the Congo and Djoué rivers [3] [8] [14] . Clay is extracted near Brazzaville and Boko, while laterite dominates in Bouenza and the Batéké Plateaus. Limestone reserves are concentrated in Loutété and Mfouati, supporting major cement factories [15] . Hard rocks like basalt and granite are located in the Batéké Plateaus and Mayombe mountains.

Artisanal mining along riverbanks significantly contributes to soil erosion, sedimentation, and water pollution due to the digging and sluicing activities, which often lead to the unmanaged release of mine tailings into waterways, causing siltation and river diversion or clogging [8] . The removal of vegetation for mining operations destabilizes soils and transforms them into unproductive wastelands, resulting in long-term degradation, increased erosion, and loss of biodiversity [16] . Furthermore, most artisanal miners (over 94%) do not conduct environmental impact assessments or implement rehabilitation plans, exacerbating environmental deterioration caused by wasteful practices and insufficient national legislation on sustainable land management [17] . This mining activity also leads to deforestation, water depletion, turbidity, and destruction of aquatic habitats. Weak enforcement of environmental regulations allows many mining companies to operate in non-compliance, dumping waste into the environment and polluting water, air, and soil, which worsens the physical degradation, biodiversity loss, and soil fertility decline [3] [18] .

Informal extraction dominates the sector, providing livelihoods but lacking legal protections, safety, or social services. Land-use conflicts often arise, especially where mining overlaps with agriculture. The absence of clear land tenure and coordinated planning results in fragmented governance. Formalizing artisanal mining could improve livelihoods and environmental compliance [17] .

Cement companies such as SONOCC and Dangote significantly influence local governance and land-use dynamics in the Republic of Congo. Their operations affect regional development, infrastructure planning, and control over mineral-rich zones. Although these companies are regulated, their economic power often marginalizes small-scale miners and reinforces spatial inequalities in contexts where governance remains weak [19] - [21] .

Sand and gravel deposits are unevenly distributed, with significant concentrations along the Congo and Djoué rivers. These materials are mainly extracted from riverbeds, generating significant environmental concerns such as habitat loss, deforestation, and land degradation due to unregulated activities in riparian and forested zones [3] [8] [18] . While the U.S. Geological Survey offers broader regional data on construction resources, specific datasets for Congo remain limited.

Clay is mined primarily on the outskirts of Brazzaville (Makélékélé, Mfilou) and in the Boko area, where it supports small-scale brickmaking. These artisanal operations are largely informal and contribute to localized environmental degradation [3] [18] . Laterite, widespread in the Bouenza region and Batéké Plateaus, is extensively used for rural road construction due to its strength and accessibility [1] .

Limestone deposits are concentrated in the southwest, especially in Loutété and Mfouati (Bouenza Department). Loutété hosts two major cement plants operated by SONOCC and Dangoté, while Dolisie is home to the FORSPAK plant. Mfouati features karstic limestone hills with historical mining significance. These limestone reserves are central to the national cement industry [1] [3] [22] .

Basalt is abundant on the Batéké Plateaus, while granite and quartzite are primarily found in the Mayombe mountains. These hard rocks are essential in infrastructure projects, including road bases, building foundations, and railway ballast [4] [17] .

Artisanal mining along riverbanks, especially near the Congo and Djoué rivers, contributes to severe erosion, increased sedimentation, and water pollution. The removal of vegetation and destabilization of soils further accelerate ecological degradation. Such operations are frequently conducted without prior environmental impact assessments or subsequent rehabilitation plans, leaving long-term scars on the landscape [2] [19] [20] .

Recent studies emphasize that quarrying and mining operations in the Republic of the Congo cause significant habitat destruction and landscape alteration, which exacerbate soil degradation and increase the risk of flooding in surrounding areas [2] . These operations also frequently encroach upon forests and ecologically sensitive zones, leading to deforestation and biodiversity loss. These pressures are further intensified by weak enforcement of environmental regulations and limited institutional capacity to monitor and manage the sector [2] [20] . Watha-Ndoudy et al. [2022] reported significant environmental degradation associated with geomaterials exploitation in the Republic of the Congo [2] .

The dominance of informal extraction limits the sector’s economic contribution to the state and undermines efforts to establish regulatory oversight. Artisanal miners often operate under precarious conditions, lacking safety equipment, social protection, and access to basic services such as healthcare and education [19] [23] .

Furthermore, conflicts over land use are common, particularly where mining activities intersect with agricultural zones. These tensions are fueled by unclear land tenure systems and the absence of coordinated land-use planning. The result is a fragmented resource landscape where competing interests go unresolved [17] [24] .

Formalizing artisanal mining in the Republic of the Congo is essential to addressing the environmental degradation and social vulnerabilities associated with the sector [11] . By establishing clear legal frameworks, implementing social protection mechanisms, and enhancing regulatory oversight, formalization can improve the livelihoods of mining communities while supporting traceability and environmental compliance [11] . If not linked to broader development strategies, however, it may worsen poverty and environmental harm, reflecting the complex challenges observed in other contexts [17] .

A digital, up-to-date geological cadastre would provide a centralized platform for mapping mineral resources. This system would enhance transparency, facilitate resource allocation, and support regulatory bodies in overseeing extraction activities in real time, especially when integrated with broader sustainable infrastructure development models applicable in Sub-Saharan Africa [32] - [34] .

Incorporating Geographic Information Systems (GIS) into resource management enables planners to identify optimal extraction sites by accounting for environmental sensitivities, infrastructure proximity, and transportation logistics, thereby enhancing spatial decision-making and promoting sustainable outcomes [35] . When combined with remote sensing technologies, GIS further strengthens the ability to detect extraction hotspots, monitor land-use changes, and support environmental protection initiatives. These tools provide a comprehensive framework for integrating environmental constraints, land-use planning, and logistical considerations into strategic planning processes.

Artisanal mining plays a critical socio-economic role in the Republic of the Congo, particularly in providing livelihoods for vulnerable populations. However, its predominantly informal and unregulated nature poses serious environmental and social challenges [24] [33] . The formalization of this sector is therefore imperative. This process requires the establishment of clear legal frameworks, the strengthening of institutional capacity, and the enforcement of environmental safeguards to improve labor conditions, ensure regulatory compliance, and mitigate ecological degradation [36] . To be both effective and equitable, formalization efforts must also be guided by legal clarity and supported by socio-economic incentives that prevent the exclusion or marginalization of artisanal miners [24] .

Promoting the use of sustainable construction materials—such as geopolymers, recycled aggregates, and industrial by-products—can significantly reduce the reliance on natural deposits and mitigate environmental degradation [34] [37] . Geopolymers, in particular, present a viable alternative to conventional cement due to their lower carbon emissions, enhanced durability, and capacity to incorporate industrial waste materials [35] . Advancing research and encouraging the adoption of innovative, eco-friendly building techniques are essential steps toward minimizing the environmental footprint of the construction sector and embedding sustainability principles into construction economics.

Fostering collaboration between academic institutions, government agencies, and the private sector is key to advancing knowledge and technical expertise in sustainable construction. Applied research, training programs, and policy support will enable the development of context-appropriate solutions and long-term resource stewardship [36] .

Sustainability strategies in construction materials management focus on minimizing environmental impacts while promoting social and economic benefits. Research highlights that adopting green construction practices reduces waste, energy use, and legal costs, improving economic outcomes alongside environmental and social performance [38] . Integrating Environmental, Social, and Governance (ESG) criteria in sustainable materials further supports the UN Sustainable Development Goals, fosters social equity, and creates healthier, energy-efficient buildings [39] [40] . Sustainable construction management plays a crucial role in optimizing resource use and enhancing overall project benefits [8] [41] [42] .

Effective implementation of these strategies hinges on multisectoral coordination, robust governance frameworks, and active community involvement. Only through an integrated and sustained effort can the Republic of the Congo ensure the responsible use of its construction materials to support both present and future development needs.