The Civil Engineering Contractor October 2018 | Page 24

ON SITE Sustainable structural shotcrete saves time Professionally placed wet shotcrete was chosen as the preferred method to apply concrete for a tricky 8m-high, 400mm-thick retaining wall for new digs being built in Braamfontein by Liviero Building, to save time and space. “In today’s increasingly competitive and challenging structural concrete marketplace, the need for innovative solutions to challenging forming issues is greater than ever,” says Dustin Strever, director of Shotcrete Africa. The marketplace is seeing greater acceptance of wet shotcrete as a logical and efficient option for structural concrete applications, with the added benefits of sustainability and environmental responsibility. Structural shotcrete offers a number of compelling advantages: substantially less formwork is required; and the formwork that is required is considerably lighter in weight. Strever says the reason for it winning the concrete application contract for the South Point Bertha Avenue/ Jorissen Street development was primarily the saving in time. “Our application methodology meant that 80m 3 of concrete could be laid in two days without the need for formwork, whereas the traditional methodology of form-and-pour would have taken just over 10 days to erect the shuttering and place the concrete using the on-site crane and a concrete kibble. There was a difficult and congested working area and we were able to allow the other contractors to continue working while we completed our scope.” One advantage of wet shotcrete is that it can be placed in difficult, tight-to-reach areas. Strever mentions that in this case, the cost of the shotcrete option was approximately 15% higher than the on-site allowable, “but allowables don’t take into consideration the real savings in time, crane, and other plant and equipment”. 22 - CEC October 2018 A recent concrete application. Applying a smooth finish. “We can accelerate the pace of projects, and in this instance saved Liviero 10 days on only 80m 3 . Imagine what could be saved time-wise on an 8 000m 3 contract, though both wet shotcrete and dry shotcrete (gunite) methodologies are both equally excellent ways of placing concrete.” Each has its own definite advantages and disadvantages. Dry shotcrete must not be used in thick structural elements due to high rebound and fluctuating w/c ratios; however, it is a superlative concrete repair method. One reason why shotcrete is not as well supported as i