Civil Engineering August 2022 | Vol 30 No 7

32 August 2022 Civil Engineering T he provision and implementation of good-quality construction mate- rials is important given the ongoing requirement to deliver on increasingly higher standards of infrastructure across South Africa, coupled with government’s infrastructure-led Economic Recovery and Reconstruction Programme. In support of these national impera- tives, the Council for Geoscience under- took research to delineate the availability and quality of hard rock aggregates across southwestern KwaZulu-Natal. This will allow stakeholders and authorities in urban areas to take stock of what is available and to identify where to prioritise detailed assessment efforts in support of specific infrastructure development projects. APPROACH The Council for Geoscience’s team of engineering geologists used an integrated approach, incorporating remote sensing techniques, geological and engineering geological mapping methodologies, and well-established laboratory practices. A total of 185 samples were collected during three field investigation phases, aimed at characterising primary lithological units such as metasedimentary and plutonic rocks of the Namaqua Natal Metamorphic Province, the Natal Group, Dwyka Group tillite, sedimentary rocks of the Ecca and Beaufort Groups, and Karoo dolerite. Mapping crushed aggregate resource potential in KZN Figure 1 Field mapping and sampling of the Margate gneissose garnet leucogranite in the vicinity of the Mpenjati River 0 50 100 150 200 250 300 350 400 450 0,0 10,0 20,0 30,0 40,0 50,0 60,0 10% FACT dry value (kN) ACV dry value (%) Dwyka tillite Karoo dolerite Natal sandstone Natal quartzite Natal granulestone Beaufort sandstone Beaufort siltstone Beaufort shale Ecca sandstone Ecca shale Ecca slate Ingwe granodiorite Mapumulo paragneiss and migmatite Mzumbe gneissic quartz diorite Mkomazi granite gneiss Mzimlilo granite gneiss Margate gneissose garnet leucogranite Mapumulo amphibolite Mzimkulu amphibolite Mzimkulu (Marble Delta) Oribi Gorge granite Mahlongwa granite Arenaceous rocks with a siliceous cementing material and/or other compliant rock types R 2 = 0,7901 Arenaceous rocks without a siliceous cementing material Diamictites (tillite) Argillaceous rocks (shale, slate) COTO specifications (2020): Figure 2 10% FACT versus aggregate crushing values of the major lithological units across southwestern KwaZulu-Natal (Note: 10% FACT values were estimated from the aggregate impact value (AIV) in accordance with test method BS 812-112: 1990)