{"id":2490,"date":"2025-09-16T04:30:08","date_gmt":"2025-09-16T04:30:08","guid":{"rendered":"https:\/\/dev.conceptcc.co.za\/izulu\/?page_id=2490"},"modified":"2025-09-16T08:14:35","modified_gmt":"2025-09-16T08:14:35","slug":"post-tensioning","status":"publish","type":"page","link":"https:\/\/dev.conceptcc.co.za\/izulu\/post-tensioning\/","title":{"rendered":"Post Tensioning"},"content":{"rendered":"

[vc_row][vc_column][vc_custom_heading text=”Post-tensioning” font_container=”tag:h1|text_align:left” use_theme_fonts=”yes” css=””][vc_empty_space height=”15″][vc_column_text css=””]Post-tensioning<\/strong> is a construction method used to strengthen concrete by running high-strength steel tendons or strands through ducts in the concrete, which are then tensioned and anchored after the concrete has cured. This process places the concrete under compression, allowing for longer spans, thinner slabs, and greater resistance to cracking, making it especially valuable in dams, bridges, and large-scale structural projects.[\/vc_column_text][\/vc_column][\/vc_row][vc_row css=”.vc_custom_1453476243999{margin-bottom: 15px !important;}”][vc_column]

\"\"
Post-Tesnioning-1138X655<\/figcaption><\/figure><\/div>[\/vc_column][\/vc_row][vc_row][vc_column][vc_empty_space height=”15″][vc_custom_heading text=”New Sub Head Here” use_theme_fonts=”yes” css=””][vc_empty_space height=”15″][vc_column_text]Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris a enim aliquam, condimentum nisl a, laoreet lectus. Aliquam convallis sed elit nec vehicula. Praesent gravida, massa sit amet ullamcorper fringilla, tortor nunc ultrices dui, in tristique leo leo sed massa.<\/p>\n

Quisque et lectus pulvinar, porttitor mi non, elementum dui. Morbi mi nisl, tincidunt sed venenatis eget, finibus eu mauris. Nullam nisi lacus, feugiat eget varius eget, pellentesque dictum odio. Sed sollicitudin viverra est, at aliquam metus ultrices id. Duis eu purus vel nisl commodo facilisis vitae ut lectus.<\/p>\n

Sed elementum dapibus tellus, a dictum metus interdum ac. Nullam condimentum, dui volutpat fringilla molestie, libero tortor ultrices lorem, at tempus diam purus non velit. Aliquam vel nulla eleifend, consequat elit id, tristique massa. Fusce dolor velit, blandit ac erat ac, vestibulum ornare diam.<\/p>\n

Curabitur maximus feugiat velit, sed dapibus sem auctor quis. Maecenas turpis purus, tincidunt eget mattis ac, placerat sit amet dolor. Aenean vel porttitor.\u00a0Maecenas turpis purus, tincidunt eget mattis ac, placerat sit amet dolor. Aenean vel porttitor libero.[\/vc_column_text][\/vc_column][\/vc_row][vc_row][vc_column][vc_empty_space height=”15″][vc_custom_heading text=”SPECIFICATIONS” use_theme_fonts=”yes” css=””][vc_empty_space height=”15″][vc_column_text css=””]<\/p>\n

Materials<\/h3>\n
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  • \n

    Strands (bonded\/unbonded):<\/strong> 7-wire, low-relaxation steel
    \u2014 \u00d8 12.7 mm (0.5″)<\/strong>, 15.2\/15.7 mm (0.6″)<\/strong>
    \u2014 fpu \u2248 1,770\u20131,860 MPa (250\u2013270 ksi)<\/strong>; E \u2248 195\u2013205 GPa<\/p>\n<\/li>\n

  • \n

    Bars (where used):<\/strong> \u00d8 26\u201375 mm, fpu \u2248 1,030\u20131,080 MPa<\/strong><\/p>\n<\/li>\n

  • \n

    Ducts (bonded multistrand):<\/strong> steel or HDPE corrugated, \u00d8 50\u2013130 mm<\/strong> typical<\/p>\n<\/li>\n

  • \n

    Anchorage hardware:<\/strong> wedges + bearing plates per system; galvanised or stainless options<\/p>\n<\/li>\n

  • \n

    Sheathing (unbonded):<\/strong> HDPE with grease<\/strong> corrosion protection<\/p>\n<\/li>\n

  • \n

    Grout (bonded):<\/strong> cementitious, non-shrink, low-bleed<\/p>\n<\/li>\n<\/ul>\n

    Concrete & cover<\/h3>\n
      \n
    • \n

      Concrete strength before stressing:<\/strong> typically \u2265 25\u201330 MPa<\/strong> (check design)<\/p>\n<\/li>\n

    • \n

      Nominal cover to duct\/tendon:<\/strong> interior \u2265 25\u201340 mm<\/strong>; exterior\/exposure \u2265 40\u201375 mm<\/strong> (environment dependent)<\/p>\n<\/li>\n<\/ul>\n

      Stressing & acceptance<\/h3>\n
        \n
      • \n

        Stressing level:<\/strong> typically 0.70\u20130.80 fpu<\/strong> (do not exceed system limit)<\/p>\n<\/li>\n

      • \n

        Elongation tolerance:<\/strong> measured vs theoretical \u00b17%<\/strong> (common)<\/p>\n<\/li>\n

      • \n

        Jack calibration:<\/strong> certified within 30 days\/usage<\/strong>, accuracy \u00b12%<\/strong><\/p>\n<\/li>\n

      • \n

        Seating loss (wedges):<\/strong> allow ~3\u20136 mm<\/strong> (system specific)<\/p>\n<\/li>\n

      • \n

        Stressing sequence:<\/strong> from the most restrained end; alternate\/multiple stages to control cracks\/deflection<\/p>\n<\/li>\n<\/ul>\n

        Friction & layout<\/h3>\n
          \n
        • \n

          Friction coefficient (\u03bc):<\/strong>
          \u2014 steel duct ~0.20\u20130.25<\/strong>; plastic\/HDPE ~0.10\u20130.18<\/strong><\/p>\n<\/li>\n

        • \n

          Wobble factor (k):<\/strong> ~0.001\u20130.002 per m<\/strong> (system\/layout dependent)<\/p>\n<\/li>\n

        • \n

          Minimum radius of curvature:<\/strong> typically \u2265 50\u2013100 \u00d7 duct diameter<\/strong> (follow supplier tables)<\/p>\n<\/li>\n

        • \n

          Deviators\/blocks:<\/strong> provide bursting\/anchor zone reinforcement per design<\/p>\n<\/li>\n<\/ul>\n

          Grouting (bonded systems)<\/h3>\n
            \n
          • \n

            w\/c ratio:<\/strong> ~0.40\u20130.45<\/strong><\/p>\n<\/li>\n

          • \n

            Bleed:<\/strong> \u2264 0.3%<\/strong> (low-bleed spec)<\/p>\n<\/li>\n

          • \n

            Compressive strength:<\/strong> \u2265 17\u201325 MPa @ 7 days<\/strong> (project-specific 28-day often \u2265 30 MPa)<\/p>\n<\/li>\n

          • \n

            Chlorides:<\/strong> very low\u2014\u2264 0.1%<\/strong> by mass of cement (or per spec)<\/p>\n<\/li>\n

          • \n

            Temperature (mix\/injection):<\/strong> generally 10\u201332 \u00b0C<\/strong><\/p>\n<\/li>\n

          • \n

            Grout verification:<\/strong> density, flow, bleed tests each batch; venting from high points until neat grout<\/p>\n<\/li>\n<\/ul>\n

            QA\/QC & testing<\/h3>\n
              \n
            • \n

              Tendon ID\/tracking<\/strong> per drawing; record jack pressure & elongations<\/strong><\/p>\n<\/li>\n

            • \n

              Lift-off checks:<\/strong> sample tendons (e.g., 1\u20135%<\/strong>) to verify residual force<\/p>\n<\/li>\n

            • \n

              Duct pressure\/continuity tests<\/strong> prior to grouting (bonded)<\/p>\n<\/li>\n

            • \n

              Protection of unbonded tails:<\/strong> caps + grease; seal all vents\/anchorages after grout set<\/p>\n<\/li>\n<\/ul>\n

              References to align with (South Africa\/UK\/EU)<\/h3>\n
                \n
              • \n

                EN 1992 \/ BS 8110<\/strong> practices, PTI<\/strong> (Post-Tensioning Institute) manuals, and local SANS 10100<\/strong>\/project specs.<\/p>\n<\/li>\n<\/ul>\n

                [\/vc_column_text][\/vc_column][\/vc_row]<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

                [vc_row][vc_column][vc_custom_heading text=”Post-tensioning” font_container=”tag:h1|text_align:left” use_theme_fonts=”yes” css=””][vc_empty_space height=”15″][vc_column_text css=””]Post-tensioning is a construction method used to strengthen concrete by running high-strength steel tendons or strands through ducts in the concrete, which are then tensioned and anchored after the concrete has cured. This process …<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"pagelayer_contact_templates":[],"_pagelayer_content":"","footnotes":""},"class_list":["post-2490","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/dev.conceptcc.co.za\/izulu\/wp-json\/wp\/v2\/pages\/2490","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dev.conceptcc.co.za\/izulu\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/dev.conceptcc.co.za\/izulu\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/dev.conceptcc.co.za\/izulu\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/dev.conceptcc.co.za\/izulu\/wp-json\/wp\/v2\/comments?post=2490"}],"version-history":[{"count":3,"href":"https:\/\/dev.conceptcc.co.za\/izulu\/wp-json\/wp\/v2\/pages\/2490\/revisions"}],"predecessor-version":[{"id":4013,"href":"https:\/\/dev.conceptcc.co.za\/izulu\/wp-json\/wp\/v2\/pages\/2490\/revisions\/4013"}],"wp:attachment":[{"href":"https:\/\/dev.conceptcc.co.za\/izulu\/wp-json\/wp\/v2\/media?parent=2490"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}