Effect of superplasticiser and sodium tripolyphosphate on fluidity of cement paste

Abstract

The effect of sodium tripolyphosphate (STPP) on the fluidity of cement paste with lignin sulfonate (LS), sulfonated naphthalene formaldehyde condensate (FDN) and polycarboxylate ether (PCE) superplasticiser (SP) was studied. The adsorption amounts of LS, FDN and PCE were assessed using UV spectrophotometry and total organic carbon analysis; the concentration of Ca 2+ ions in solution and the adsorption amounts of STPP were tested with plasma emission spectrometry and the electrokinetic properties of the cement particles were confirmed using ae-potential measurements. Based on analysis of the adsorption amounts, the Ca 2+ concentration, ae-potential and fluidity of cement paste, the competitive adsorption between SPs and STPP was investigated. The result shows that SP and STPP can all adsorb onto the surface of cement particles and there is competitive adsorption between STPP and SP. STPP prevents Ca 2+ releasing and pre-empts the adsorption sites of SP; it causes a reduction in the adsorption amount of SP and increases the ae-potential of cement particles. The SP also reduces the adsorption amount of STPP. Competitive adsorption causes changes in fluidity and fluidity loss. STPP can improve the initial fluidity and reduce fluidity loss of cement paste with LS or FDN. With PCE and STPP, the initial fluidity can be improved, but fluidity loss increases; this is due to the different molecular structure of the SPs. It is thus suggested that STPP can be used with LS and FDN to improve fluidity and reduce fluidity loss, but it is a disadvantage when used with PCE.

Studying effects of chemical admixtures on the workability retention of zeolitic Portland cement mortar

“…They also noticed that the mixture containing polycarboxylate type admixture had the lowest slump loss. Superior performance of PC in terms of workability retention at constant dosage and w/c ratio was also observed by Tan et al [25]. However, Gołaszewski and Szwabowski observed the same slump loss of mortars with PC and NSF superplasticizers [26].…”

Effect of competitive adsorption between polycarboxylate superplasticiser and sodium tripolyphosphate on cement paste fluidity

“…Tartaric acid or citric acid can reduce the adsorption amount of PCS to improve fluidity loss (Plank and Winter, 2008) and sulfate can also reduce the adsorption of PCS (Fan et al, 2012;Yamada et al, 2001). It is uncertain whether the adsorption of ions in solution is reduced or not, but research on the competitive adsorption between sodium gluconate and naphthalene-based superplasticiser has proved that both their adsorption amounts are reduced (Yang et al, 2013 superplasticiser also inhibit the adsorption of each other, and both their adsorption amounts are reduced due to competitive adsorption (Tan et al, 2014a(Tan et al, , 2014b. It can be inferred that ions in solution adsorb onto the surfaces of cement particles, thus pre-empting adsorption points so that superplasticiser cannot be adsorbed.…”

“…Sodium tripolyphosphate in solution can react with calcium ions to form complexes and adsorb onto cement surfaces because of its strong chelating ability (Tan et al, 2014b). With carboxyl groups in the side chains of PCS, these polymers can easily react with calcium ions, as shown in Figure 4 (Plank and Sachsenhauser, 2009).…”

“…From a traditional point of view, the widely used retarder sodium tripolyphosphate improves the fluidity and workability of cement and concrete with added superplasticiser (Tan et al, 2014a(Tan et al, , 2014b. The main reason for this is that cement hydration and the formation of cement products are delayed by the presence sodium tripolyphosphate, which can reduce the consumption of water and superplasticiser in the first few minutes.…”

Effect of Sodium Hexametaphosphate and Trisodium Phosphate on Dispersion of Polycarboxylate Superplasticizer

“…Generally, high fluidity can be easily achieved by incorporation of the comb-type copolymers, known as polycarboxylate superplasticizer (PCE) system [13][14][15][16], and this system consists of copolymers and retarders, rather than a single-component system [17][18][19]. In spite of being added as a supplementary material, retarders can significantly enhance the dispersion capacity of the superplasticizer system [20,21], and, in the real engineering practice, this has been widely employed. The generally believed reason is because the consumed free water and superplasticizer was reduced, as a result of the delayed hydration of cement minerals [22][23][24][25].…”