Structure of C-S-H/PCE Prepared from PCE with Different Side Chain Densities and Its Effects on Early Hydration Properties of Cement

doi:10.12141/j.issn.1000-565X.220176

Abstract

Abstract:

The development of prefabricated buildings increases the demand for using early strong agents in the production of prefabrication. As a new type of crystal early strength agent, synthetic calcium silicate hydrate (C-S-H) can significantly enhance the early strength of cement-based materials, but its poor dispersibility limits its application. In this paper, the polycarboxylate superplasticizers (PCE) with different side chain density were used as a dispersant to synthesis a series of C-S-H/PCE by means of co-precipitation method. The influence of C-S-H/PCE on the structure of C-S-H was studied with XRD, FT-IR, DLC. Moreover, its influence on the cement hydration behavior, hardened body strength and composition structure was investigated. The results show that the smaller the side chain density of PCE, the better the dispersion of C-S-H seeds and the smaller the particle size; the median particle size can reach 339.5 nm; the increase of the number of seed particles can provide more nucleation sites. The incorporation of C-S-H/PCE can significantly accelerate cement hydration, advance the exothermic peak of hydration acceleration by 1.3 h, and increase the heat release by 10.8% at 8 h. After the incorporation of C-S-H/PCE, the porosity of the hardenite of the cement slurry decreases at 8 h and 1 d and the compressive strength increases by 13% and 15%, respectively.

Key words: synthetic calcium silicate hydrate, polycarboxylate superplasticizer, side chain density, cement, early hydration

CLC Number:

TQ172.4⁺6

YIN Suhong, YANG Xinglin, FENG Xian, et al. Structure of C-S-H/PCE Prepared from PCE with Different Side Chain Densities and Its Effects on Early Hydration Properties of Cement[J]. Journal of South China University of Technology(Natural Science Edition), 2023, 51(1): 76-83.

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样品编号	n	a∶b	M_w	M_n	M_w/M_n
P52-2	52	2∶1	60 160	30 410	1.978
P52-4	52	4∶1	70 880	32 620	2.173
P52-6	52	6∶1	97 780	35 740	2.736

样品编号	底料成分		H₂O₂	混合液1成分		混合液2成分
样品编号	HPEG	水	H₂O₂	AA	水	MPA	维生素C	水
P52-2	60	25	0.34	3.6	40	0.08	0.11	28
P52-4	60	25	0.57	7.2	40	0.15	0.18	35
P52-6	60	25	0.80	10.8	40	0.23	0.25	40

样品编号	中位粒径/nm	样品编号	中位粒径/nm
C-S-H	4 661.0	C-S-H/P52-4	378.6
C-S-H/P52-2	433.7	C-S-H/P52-6	339.5

水化产物	特征峰位置/nm	8 h龄期时的峰强度上升率%			1 d龄期时的峰强度上升率/%
水化产物	特征峰位置/nm	1% C-S-H/P52-2	1% C-S-H/P52-4	1% C-S-H/P52-6	1% C-S-H/P52-2	1% C-S-H/P52-4	1% C-S-H/P52-6
C₃S	0.278	-8.77	-14.00	-16.69	-3.29	-5.11	-7.08
	0.265	-9.19	-13.42	-14.39	-9.65	-10.77	-15.66
	0.307	-3.67	-8.10	-18.35	-2.62	-5.24	-11.69
C₂S	0.275	-2.76	-3.81	-4.73	-4.43	-5.91	-6.57
	0.278	-4.53	-12.59	-16.69	-4.94	-6.43	-7.08
	0.260	-7.75	-15.07	-15.63	-5.88	-6.50	-10.68
CH	0.263	16.60	21.37	28.44	2.69	4.42	8.37
	0.490	1.97	3.66	10.69	1.05	1.44	2.36
	0.193	2.27	9.85	41.67	2.17	4.64	12.07

龄期	样品	孔径分布/%			孔隙率/%
龄期	样品	<10 nm	10~50 nm	50~10 000 nm	孔隙率/%
8 h	空白样	2.44	70.11	27.00	32.18
	C-S-H/P52-2	3.68	69.36	26.59	30.13
	C-S-H/P52-4	3.91	69.28	26.16	26.48
	C-S-H/P52-6	5.09	68.97	25.39	25.20
1 d	空白样	13.63	73.71	12.43	27.49
	C-S-H/P52-2	13.71	73.53	12.39	25.26
	C-S-H/P52-4	14.08	75.83	9.51	24.19
	C-S-H/P52-6	15.53	76.69	7.21	22.37