Sika colloidal silica agent arms contractors to control slab destiny

Nanotechnology driving deployment of particles far smaller than those typical of cementitious materials augments the latest addition to the Sika Corp. line of concrete admixtures for improving slab on grade performance. A colloidal silica topical agent, SikaCem-190 Concrete Control is spray applied during floating or troweling to maintain adequate moisture, promote cement particle hydration, and reduce premature set risk. The non-filming, low VOC product suits plain or colored slabs and those treated with dry shake hardeners. 

“SikaCem-190 puts the contractor in charge of workability and timing of the finishing process,” says Vice President, SikaColor Adam Jordan. “It represents our continuous investment in innovation and new technology in the leading decorative concrete marketplace.” 

Lab and field testing has proved the product’s potential to react with the entire mix and extend workability; lubricate slab surface; promote proper hydration, along with flatter, thicker, denser cream cap; reduce surface crazing and efflorescence; and, improve abrasion resistance.

“Concrete has a very rough surface, even in its plastic state, so there are many peaks and valleys, like a moonscape, especially when viewed under a microscope. SikaCem-190 essentially fills in the peaks and valleys, creating a smoother surface, thereby increasing the surface area,” explains Sika Sales Representative Todd Stone. “Think of the concrete slab or surface as a rough sponge with many open pores. This filling of the capillary action by our tiny amorphous colloidal silica helps hydrate available unhydrated cement particles—giving exceptional cream at the cap. Capillary filling also significantly reduces the amount of surface dehydration, allowing the concrete to gain additional strength and abrasion resistance during the first 48 hours. When it dries, the amorphous colloidal silica anchors into all sides of the capillary, bridging incredibly strong crystals.”

“Filling voids with crystals is only half the equation,” he continues. “Crystalline structures don’t always have great bonds or great structure. SikaCem-190 builds incredibly strong bridges because we have the purest formulation of colloidal silica for the concrete market.”

NanoSilica particles typical of those in SikaCem-190 exhibit a high degree of pozzolanic activity, Stone adds. They can function as pozzolanic process catalysts in fresh concrete, promoting tricalcium silicate dissolution and calcium silicate hydrate production by providing nucleation sites. — Sika Corp., Lyndhurst, N.J.,