Kemsolid, a subsidiary of German attachment manufacturer KEMROC, builds soil mixing tools that mount on standard excavators and piling rigs to stabilise soft ground in place. With Big 5 Construct Saudi spending its August edition on the foundational phase of construction, the economics of avoiding excavate-and-replace are getting a closer look.
Big 5 Construct Saudi has spent this week on the part of a project that nobody photographs. The August edition of the show is built around the foundational phase of construction — heavy plant, concrete, ground works and the systems that go in before anything is visible above grade — and the least resolved cost line in that phase is what to do about ground that will not carry a load.
The conventional answer is to remove it. Excavate the soft material, cart it away, import engineered fill, compact it in layers and test. That sequence consumes truck movements, tipping capacity, imported material and programme, and on a saturated site it also consumes dewatering. An alternative that has been gaining ground in European civils is to leave the soil where it is and change its properties in place.
Kemsolid, which was set up as a subsidiary of the German attachment manufacturer KEMROC, builds the tooling for exactly that. Its KSI soil mixing attachments mount on a standard excavator or on drilling and piling equipment and mix binder into the ground as they advance, producing soil-cement diaphragm and retaining walls at working depths that the manufacturer states run from four to sixteen metres. For shallower work across a whole footprint rather than along a line, its KRD drum units perform mass soil mixing to around six metres.
The distinction between the two methods matters on site. Trench soil mixing follows a line and is used where the objective is a cut-off wall, a retaining element or a strip of improved ground under a foundation. Mass soil mixing treats an area, and is the technique reached for when a whole platform, a tank base or a road formation sits on material that will settle. Both work by binding the fines in place rather than replacing them, which is why the manufacturer positions them at soft to fluid soils — clays, loams, silts and mixed or unstable ground — rather than at rock.
The arithmetic that makes the method attractive is not primarily environmental, though the supplier's case leans on a stated reduction in carbon dioxide of up to 40 per cent against excavate-and-replace. The harder number is disposal. Every cubic metre of unsuitable material that leaves a site has to be loaded, hauled, received and paid for, and on a large platform in a congested corridor the haulage itself becomes the constraint rather than the earthworks. In-situ mixing removes most of that movement, and with it a large share of the traffic management, the wheel-wash and the neighbour complaints.
Ground improvement is not a fringe topic in the Saudi programme. Keller, one of the specialist contractors in the field, was among the companies spotlighted on the show's sustainability trail this week, and the reason is straightforward: the Kingdom is building on coastal and reclaimed sites, on corridors that cross old wadi deposits, and on industrial platforms where settlement tolerances are measured in millimetres. Every one of those conditions is a decision between removing the problem and treating it.
The caution is that in-situ mixing is a design-led method rather than a plant purchase. The binder dosage, the mixing energy and the resulting strength have to be established by trial and confirmed by coring, and the achieved product is only as uniform as the operator and the ground allow. Contractors used to specifying imported fill by a compaction test are being asked to accept a performance specification on a material they cannot see. That is a procurement change as much as a technical one, and it is the sort of change the Kingdom's volume of foundation work will eventually force.