{"id":25638,"date":"2026-02-05T00:35:43","date_gmt":"2026-02-05T00:35:43","guid":{"rendered":"http:\/\/141.23.68.248\/wp\/?page_id=25638"},"modified":"2026-02-09T17:04:32","modified_gmt":"2026-02-09T17:04:32","slug":"raft-mat-foundation","status":"publish","type":"page","link":"http:\/\/141.23.68.248\/wp\/?page_id=25638","title":{"rendered":"Raft Mat Foundation"},"content":{"rendered":"\n

Introduction<\/strong><\/h2>\n\n\n\n

Design decisions made during the early stages of civil engineering projects have long-term implications for environmental performance and maintenance requirements. Foundations are critical structural elements, and their material selection strongly influences the life-cycle impacts of buildings and infrastructure. Reinforced concrete (RC) raft foundations are widely used due to their simplicity and ability to distribute loads uniformly. However, the durability of the reinforcement system governs the frequency of maintenance interventions and associated environmental burdens.<\/p>\n\n\n\n

This study evaluates the environmental performance of three reinforcement strategies for a raft foundation reinforcement mat using life-cycle assessment (LCA)<\/strong> combined with multi-criteria decision analysis (AHP)<\/strong>. The analysis focuses on energy consumption and emissions of CO\u2082, NOx, and SO\u2082 over a 75-year service life<\/strong>, providing comparative insights to support sustainable design decisions at the conceptual stage.<\/p>\n\n\n\n

System Description and Design Alternatives<\/strong><\/h2>\n\n\n\n

Subsystem: Raft Foundation Reinforcement Mat<\/strong><\/h3>\n\n\n\n

The subsystem analyzed is the reinforcement mat of a reinforced concrete raft foundation with dimensions 16 m \u00d7 15 m \u00d7 0.25 m<\/strong>, corresponding to a total concrete volume of 60 m\u00b3<\/strong>. At this conceptual design stage, the geometry and thickness of the foundation were assumed constant for all alternatives to ensure functional equivalence. This approach is consistent with early-stage LCA practice, where standardized material intensities are used instead of detailed structural sizing (ISO 14040, 2006a).<\/p>\n\n\n\n

Three reinforcement strategies were evaluated:<\/p>\n\n\n\n

    \n
  1. Option A \u2013 Baseline steel reinforcement<\/strong>
    <\/strong> Conventional uncoated steel reinforcement, susceptible to corrosion and requiring frequent maintenance.
    <\/li>\n\n\n\n
  2. Option B \u2013 Protected steel reinforcement<\/strong>
    <\/strong> Steel reinforcement with protective measures to reduce corrosion and maintenance frequency.
    <\/li>\n\n\n\n
  3. Option C \u2013 Fiber-reinforced polymer (FRP) reinforcement<\/strong>
    <\/strong> Corrosion-resistant FRP reinforcement with minimal maintenance requirements but higher embodied energy during production.
    <\/li>\n<\/ol>\n\n\n
    \n
    \"\"<\/a><\/figure><\/div>\n\n\n

      Option A                Option B              Option C<\/strong><\/p>\n\n\n\n

    Figure 1.<\/strong> Design Options for raft foundations: (A) baseline steel, (B) protected steel, and (C) FRP reinforcement.<\/p>\n\n\n\n

    Life-Cycle Scope and Maintenance Strategy<\/strong><\/h2>\n\n\n\n

    The assessment adopts a cradle-to-grave perspective<\/strong>, including material production, transportation, construction, and maintenance over 75 years<\/strong>. Operational energy related to building use and end-of-life processes were excluded due to their independence from foundation design and limited data availability, respectively (ISO 14044, 2006b).<\/p>\n\n\n\n

    Maintenance interventions were defined based on durability characteristics reported in the literature for reinforced concrete foundations (Huang et al., 2019). Baseline steel requires the most frequent inspections and repairs, protected steel reduces intervention frequency, and FRP reinforcement requires minimal maintenance. Over the service life, seven interventions<\/strong> were considered for Option A, five for Option B<\/strong>, and three for Option C<\/strong>..<\/p>\n\n\n\n

    Life-Cycle Inventory (LCI)<\/strong><\/h2>\n\n\n\n

    Material quantities per cubic meter of reinforced concrete were derived from published life-cycle inventory datasets<\/strong> rather than project-specific structural calculations. Cement, fly ash, and aggregate quantities were adopted from the Portland Cement Association<\/strong> and NRMCA<\/strong> datasets for reinforced concrete foundations (Marceau et al., 2007; NRMCA, 2011). Reinforcement intensity for steel was assumed as 135 kg\/m\u00b3<\/strong>, consistent with values reported for foundation slabs in LCI-based studies (Marceau et al., 2007).<\/p>\n\n\n\n

    For FRP reinforcement, a reduced quantity of 54 kg\/m\u00b3<\/strong> (approximately 40% of steel mass) was assumed, reflecting its higher tensile strength and corrosion resistance, following assumptions reported by Van Geem and Marceau (2015). Environmental impact factors for energy use and emissions (CO\u2082, NOx, SO\u2082) were taken directly from the same sources.<\/p>\n\n\n\n

    This approach is appropriate for comparative LCA at the conceptual design stage but does not replace detailed structural design.<\/p>\n\n\n\n

    Life-Cycle Assessment Results<\/strong><\/h2>\n\n\n\n

    The cumulative life-cycle environmental impacts over 75 years are summarized in Table 1.<\/p>\n\n\n\n

    Table 1. <\/strong>Life-cycle assessment results for raft foundation reinforcement options<\/p>\n\n\n\n

    Option<\/strong><\/td>Energy (MJ)<\/strong><\/td>CO\u2082 (g)<\/strong><\/td>NOx (g)<\/strong><\/td>SO\u2082 (g)<\/strong><\/td><\/tr>
    A<\/td>1729.57<\/td>169,197.13<\/td>70.40<\/td>53.84<\/td><\/tr>
    B<\/td>1316.41<\/td>122,880.09<\/td>50.28<\/td>38.46<\/td><\/tr>
    C<\/td>1008.54<\/td>54,336.65<\/td>21.62<\/td>7.87<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

    Option A exhibits the highest environmental impacts across all indicators due to frequent maintenance interventions. Option B shows moderate reductions, while Option C achieves the lowest cumulative impacts, particularly for NOx and SO\u2082 emissions, reflecting its corrosion resistance and reduced maintenance requirements.<\/p>\n\n\n\n

    \"\"<\/a><\/figure>\n\n\n\n

    Figure 5\u20138.<\/strong> Comparative life-cycle energy consumption and emissions (CO\u2082, NOx, SO\u2082) for Options A, B, and C.<\/p>\n\n\n\n

    Multi-Criteria Decision Analysis (AHP)<\/strong><\/h2>\n\n\n\n

    To integrate multiple environmental indicators into a single ranking, the Analytic Hierarchy Process (AHP)<\/strong> was applied following Saaty\u2019s methodology (Saaty, 1980). The criteria considered were energy consumption, CO\u2082 emissions, NOx emissions, and SO\u2082 emissions. Pairwise comparisons of alternatives were derived from normalized LCA results, with preference intensities reflecting relative differences between options.<\/p>\n\n\n\n

    The resulting AHP scores were:<\/p>\n\n\n\n