Effect of Calcium Nitrate on the Properties of Portland–Limestone Cement-Based Concrete Cured at Low Temperature

Abstract

The effect of calcium nitrate (CN) dosages from 0 to 3% (of cement mass) on the properties of fresh cement paste rheology and hardening processes and on the strength of hardened concrete with two types of limestone-blended composite cements (CEM II A-LL 42.5 R and 42.5 N) at different initial (two-day) curing temperatures (−10 °C to +20 °C) is presented. The rheology results showed that a CN dosage up to 1.5% works as a plasticizing admixture, while higher amounts demonstrate the effect of increasing viscosity. At higher CN content, the viscosity growth in normal early strength (N type) cement pastes is much slower than in high early strength (R type) cement pastes. For both cement-type pastes, shortening the initial and final setting times is more effective when using 3% at +5 °C and 0 °C. At these temperatures, the use of 3% CN reduces the initial setting time for high early strength paste by 7.4 and 5.4 times and for normal early strength cement paste by 3.5 and 3.4 times when compared to a CN-free cement paste. The most efficient use of CN is achieved at −5 °C for compressive strength enlargement; a 1% CN dosage ensures the compressive strength of samples at a −5 °C initial curing temperature, with high early strength cement exceeding 3.5 MPa but being less than the required 3.5 MPa in samples with normal early strength cement.

Compatibility and Biomineralization Oriented Optimization of Nutrient Content in Nitrate-Reducing-Biogranules-Based Microbial Self-Healing Concrete

“…Above this limit, initial and final setting times, as well as the workability of the mortar decreased significantly to the levels which compromised the commercial application of these mixtures without the use of additional modifiers (set retarders, superplasticizers, etc.). Similar set acceleration behaviours of CN and CF were also reported in previous studies and attributed to the increased calcium content in the mixture [17,18,21]. Thus, calcium content of the nutrients should not exceed 2.00% w/w cement.…”

Study of the Structure and Properties of Electrical Sand Concrete under Prolonged Exposure to Sulfate Environment

“…A significant number of experimental and theoretical studies indicate that the degree of electrical conductivity of a composite material based on Portland cement modified with electrically conductive additives is determined by reaching the percolation threshold [ 7 , 19 ]. Along with this, the factors [ 7 , 20 ] that have a direct impact on the electrical resistivity for a long time were studied. The main one is the recrystallization of crystalline hydrate and hydrosulfoaluminate compounds, which have clear dielectric properties at the level of 10 9 Ωcm [ 7 , 20 ].…”

“…Along with this, the factors [ 7 , 20 ] that have a direct impact on the electrical resistivity for a long time were studied. The main one is the recrystallization of crystalline hydrate and hydrosulfoaluminate compounds, which have clear dielectric properties at the level of 10 9 Ωcm [ 7 , 20 ]. In view of this, it is proposed to use such additives as calcium chloride and calcium nitrite, containing the like-named cation with alite and belite, which ensures the acceleration of hydration processes [ 20 , 21 ].…”

“…The main one is the recrystallization of crystalline hydrate and hydrosulfoaluminate compounds, which have clear dielectric properties at the level of 10 9 Ωcm [ 7 , 20 ]. In view of this, it is proposed to use such additives as calcium chloride and calcium nitrite, containing the like-named cation with alite and belite, which ensures the acceleration of hydration processes [ 20 , 21 ]. The use of these additives leads to the rapid formation of CSH and reduces the intensity of ettringite formation [ 7 , 22 ], thus stabilizing the electrical resistivity.…”

Effect of layered double hydroxides Ca-Al LDHs and polycarboxylate ethers on the hardening of Portland limestone cement

“…Such admixture as calcium nitrate effectively accelerates the hydration of Portland limestone cement and thus activates the crystallization processes of hydrates; it contains the same cations as clinker minerals [27]. One should also note the importance of using complex admixtures based on calcium nitrate and superplasticizers in concretes.…”