Cement Alkalinity Variation
Effects of temperature, humidity and CO2 concentration on …
Firstly, carbonation decreases concrete alkalinity and destroys passive film on steel reinforcement relying on a pH of exceeding 12.5 [10], [11]; Secondly, CO 2 reacts with Ca-bearing products like CSH gel and AFm products, weakening the resistance of salt ingress; Finally, as carbonation progresses, surface of the carbonated concrete becomes ...
Axial compressive behavior of low-alkalinity seawater sea-sand concrete
In order to record the lateral expansion variation of the concrete core (i.e., the concrete inside of the hoops) during compression, three hoop bars located in the middle portion of column were selected to paste strain gauges with 120° intervals following the direction of stirrups. Three longitudinal bars were selected to monitor the internal ...
Numerical Simulation on Carbonation Depth of …
In order to further understand the carbonation process of concrete structures, the time- and temperature-dependent diffusion process of CO 2 in concrete is simulated based on the law of the CO 2 ...
Study of influence of alkaline component type on pH …
In general, for different cement systems under study pH value varies from 8.5 to 12 reflecting on the materials structure formation processes and strength gain. Shrinkage of the systems was …
Effects of cement alkalinity, exposure conditions and steel-concrete …
Effects of (1) cement alkalinity (low, normal and high), (2) exposure conditions (RH and temperature), (3) rebar surface condition (as-received versus cleaned) and (4) density and distribution of ...
Effect of alkali content of cement on properties of high …
The available literature on the properties of UHPC affected by cement alkalinity is still limited. ... such as fill or blocks. Alternatively, considering the significant variation in corn species and farming regimens, further research and ash treatment could help fine-tune the properties of this product for structural applications.
Clean and low-alkalinity one-part geopolymeric cement: …
The method to induce producing the more homogeneous microstructure in low-alkalinity one-part geopolymeric cement is also a novel research field. Graphical abstract. ... Local Ca-structure variation and microstructural characteristics on one-part activated slag system with various activators. Cement and Concrete Composites, Volume 102, 2019, pp ...
Understanding the effect of alkali content on hydration, …
In general, the alkali content in concrete exhibits dual aspects with regard to its influence on concrete. On one hand, alkali content serves as a stabilizer for hydration products …
RESEARCH ON REDUCING ALKALINITY OF AN …
In this article, XRD was utilized to analyze the alkalinity affecting the pore size of an ecological porous concrete mixture (EPCM). Variations in the pore alkalinity and compressive strength of the EPCM with different mineral admixtures were investigated using accelerated carbonization and natural carbonization.
Insights into microbial actions on hydraulic concrete …
Concrete alkalinity has also been shown to differ in various aquatic systems. ... and the amplitude of the variations differed among alkalinity gradients. For samples cultivated under low alkalinity conditions (i.e., pH 7.88–10.31; A0 to A3), the change in bacterial community diversity ranged from 15.34% to 17.88%. ...
Alkalinity Regulation and Optimization of Cementitious …
Ecological porous concrete (EPC) is one of the novel formulations of concrete with unique phytogenic properties. However, achieving both low alkalinity and high strength in EPC proves challenging due to the inherently high alkalinity of the pore environment, which hinders the growth of the plant and affects its ecological benefits significantly. This research investigated …
(PDF) Decrease of pore solution alkalinity in concrete tested …
The alkalinity difference between cement paste cylinders and reactive concretes was about the same level at 4 weeks (Tables 6 and 7). Pore solution alkalinity in Paste-Mass was 837 mmol/l, whereas in concrete, the alkalinity dropped to 561 mmol/l (33%) for Potsdam, to 478 mmol/l (40%) for Spratt, and to 558 mmol/l (33%) for Limeridge.
Insights into microbial actions on hydraulic concrete …
The mixed proportion of concrete coupons was designed based on the Chinese Standard of JGJ55-2000 [29]. The strength grade of concrete coupons was designed for the C30 class with a water-cement ratio (w/c) of 0.47 according to the commonly used concrete strength for hydraulic or municipal engineering [30], [31].
Experimental Methods to Evaluate the Carbonation Degree in Concrete
The carbonation action in concrete, in which carbonation reactions transform calcium hydroxide into calcium carbonate, is considered as a multi-phase physico-chemical process. Generally, carbonation in the cementitious composites has negative effects on the protection of reinforced bars due to the accelerated corrosion problem. The investigation of the …
Impact of novel chloride-binding on strength, chloride
In addition, less alkalinity of concrete reduces the ability of hydrated cement to bind chloride ions . Table 8 showed that incorporation of chloride binders into concrete had no influence on concrete alkalinity since pH values obtained for all specimens varied between 12.2 and 12.3, suggesting no potential for pH reduction by chloride binders ...
(PDF) Structure and Properties of Alkaline Cement and …
A new structure-based model for the durability (cracking) assessment of the alkaline cement concrete with heat of hydration and deformation properties during hardening …
ALKALINITY IN CONCRETE SLABS
In the presence of moisture, alkalinity is always an integral part of concrete or other cement based materials. The degree to which alkalinity exists depend largely on the composition of the cement used for construction. Primarily responsible for high alkalinity levels are highly soluble metal oxides such as Potassium and Sodium Hydroxides.
Leaching Behavior of Hardened Cement Paste with Mineral …
Abstract. In order to obtain the influence of mineral admixtures such as fly ash and slag on the leaching resistance of cement-based materials in water environments, a conventional leaching experiment on the slice specimens with pure, binary, and ternary cement pastes immersed into deionized water was performed. The dissolved calcium concentration, porosity, …
Study of influence of alkaline component type on pH value …
The paper discusses the questions of alkalinity changes in alkali activated cement-based materials at different stages of hardening. It was shown that use of alkali activated cement with dry ...
Insights into microbial actions on hydraulic concrete …
Although concrete carbonation played a role to increase its compressive strength, the decrease in surface alkalinity of concrete accelerated the concrete deterioration when exposed to the sewage ...
A Review on Carbonation Study in Concrete
types of concrete, the variation of the carbonation depth and the theoretical study on carbonation. Carbonation depth is the average distance, measured in mm, from the surface of the concrete or mortar where CO 2 has reduced the alkalinity of the hydrated cement to an extent such that an indicator solution based on phenolphthalein remains ...
Effects of cement alkalinity, exposure conditions and steel …
Effects of (1) cement alkalinity (low, normal and high), (2) exposure conditions (RH and temperature), (3) rebar surface condition (as-received versus cleaned) and (4) density and …
Mechanical properties of straw basalt fiber reinforced concrete
Portland cement (Type 1) was used as a binder with sand and crushed limestone as aggregates. In addition, fly ash type C was added to the concrete mix (by replacing cement by 67%, and sand by 33% of fly ash amount) to improve the compressive strength of the composite which expected to decrease due to the presence of the straw in the concrete.
Concrete Alkalinity
Calcium hydroxide is a hydration by-product of clinker - unreacted particles that when hydrated, produces cement with the calcium hydroxide making up as much as 15% of …
Sustainable Cements: Hybrid Alkaline Cements Overview
The ordinary Portland cement (PC) production contributes 2–3% of global energy use and 8% to 10% of world-wide carbon dioxide emissions (CO 2).According to estimates in 2050, the CO 2 emissions associated with the manufacture of PC, could increase between 240–260% compared to the 1990 emissions. Faced with this need, the Portland cement …
Evaluation of alkalinity changes and carbonation of geopolymer concrete
The investigation of alkalinity changes of geopolymer concrete (GPC) in various environments is important to enhance the application of GPC in the construction field. ... The changes in pH value, carbonation depth, compressive strength variation, and electrical resistance were determined after a six-month exposure to the three-above-mentioned ...
Pore Solution Chemistry of Calcium …
Calcium sulfoaluminate cement (CSA) is a type of low-CO2 binder which has been widely applied in the production of concrete. To investigate the protection capability offered by CSA to keep steel from corrosion, the pore solution …
Measurements of pH Variations in High-and Low-pH Cement …
Figure 3 shows the pH variation of hardened cement grout specimens versus curing time. ... This study can also provide insight into the use of low-alkalinity concrete to enhance the long-term ...
Assessing the durability performance of high belite cement
The widespread use of ordinary Portland cement (OPC), which has a significant carbon footprint, greatly contributes to the climate crisis. High belite cement (HBC) is renowned for its low-carbon characteristics, resulting in an evident reduction in both energy consumption and CO 2 emissions. Fly ash (FA), an industrial solid waste material, is commonly employed in …
Effect of alkali content in cement on its hydration kinetics …
Four kinds of clinker with different alkali content were used to study the effect of alkali content on hydration. A high alkali content accelerates hydration of cement at early ages …
Alkali-Activated Materials and Geopolymer: a Review of …
Yet, the variation in properties due to mixture ratio and understanding the effect and multi-functionality of the chain of factors makes the very basis for this review. ... The role of aggregate in AAMs is the same as in OPC concrete; however, high alkalinity and reactivity are reported to increase surface reaction with the binding agent.